A spectrometer with an integrating sphere (IS) detector was used to measure the absorbance due to scattering and absorption. Analysis of the measurement process showed that two measurements of the absorbance, one with the cuvette placed in the normal spectrometer position, and the second with the cuvette placed next to the entrance aperture of the IS detector, provide enough information to separate the contributions from scattering and molecular absorption. Measurements were carried out with mixtures of microsphere and chromophore solutions. Two cases were examined: microspheres suspended in an aqueous fluorescein solution, and microspheres suspended in an aqueous holmium oxide solution. In both cases, the proposed measurement model gave results which were in good agreement with the expected response. Measurements on microalgae suspensions yielded a molecular absorption contribution and a scattering contribution. The scattering contribution had significant spectral structure which was inversely related to the molecular absorption contribution. The absorption and scattering contributions may provide independent information on the status of chlorophyll molecules and the structure of chloroplasts in microalgae. The measurement of absorption and scattering in a turbid environment is an important problem. Such measurements are used to characterize impurities in water  and to cThe proposed method for measuring the scattering and molecular absorption utilizes a spectrophotometer with an integrating sphere (IS) detector. For clarity, the measurement will be described with a specific instrument—the Perkin Elmer Lambda 850i (W-Watts), passes through the cuvette placed in holder 1, enters the IS through the sample aperture of area iA (m2), and hits the wall of the IS. A reference flux, Φr (W), enters the IS through a reference aperture of area rA (m2) and hits the IS wall without passing through the cuvette. The reference beam will enter the IS, hit the IS wall and undergo the first reflection. A baffle inside the IS prevents the detector from seeing the first reflection of the incident reference beam. The reference light beam undergoes many more reflections resulting in an average flux, An incident flux, ΦrefM represents the magnification of the incident reference flux due to the many reflections on the IS wall. Neglecting the presence of the baffle, the ideal IS behavior leads to the following expression for the magnification refM = ρ (1 − f) / (1 − ρ (1 − f)). The constant f is defined as the ratio of areas given by f = (iA + rA + dA)/sA where dA and sA are the areas of the detector aperture and total sphere surface respectively. The average reflectance of the material lining the surface of the IS is given by ρ [rD, will be given by R(λ) is the radiant sensitivity of the photomultiplier cathode. The ratio of the detector area to the area of the entire IS is a constant which can be combined with the radiant sensitivity to give overall detection efficiency E(λ). It will be assumed that the dependence of the detection efficiency on wavelength comes mainly from the radiant sensitivity of the photomultiplier cathode. According to the manufacturer, the reflectance of the IS surface varies by less than 1 % over the spectral region considered in this work. This variation has a weak dependence on wavelength and may introduce a systematic uncertainty in the final result.The symbol ven by ρ . The phoiD to the incident flux, Φi entering through the sample portAn equation similar to The subscript on the magnification factor indicates that the magnification may be slightly different for the flux entering through the sample port to that for the flux entering through the reference port. The “autozero” function of the spectrometer is used to compensate for any differences in the IS detector response between the reference and sample beams in the case where there is no sample in the cuvette holder. We will assume that the detection efficiency is identical for both cases, so that the “autozero” function insures the equality given by Consider next the response of the IS detector when a cuvette with a sample is placed in holder 1. It will be assumed that the material inside the cuvette both absorbs and scatters the light passing through it. a = sa + ma where sa = sNsσ describes the contribution of scattering to the measured absorbance, and ma = mNmσ is the molecular absorption coefficient. The symbols sσ, mσ represent the scattering and absorption cross section respectively. sN, mN represent the number concentrations of the scatterers and absorbers. The effect of the first cuvette wall is represented by a change in the incident flux to tΦi = 10logtΦi where t is the transmission of the cuvette wall. The first differential equation in tΦie–ali = tΦi 10–0.434al where l is the path length which will be set to 1 cm. The second cuvette wall introduces another transmission coefficient t giving the final transmitted flux Φt = t2Φi 10–0.434al. Next, consider the scattered flux which originates from the scattering of the incident flux by the material inside the cuvette. Solving the second differential equation in sa, spa are given by n is the index of refraction of the solution, and 104 converts the area units from m2 to cm2. The quantity sa is proportional to the total scattered flux, while the quantity spa is proportional to the scattered flux within the detector acceptance aperture which is denoted by the symbol Δ in i(θ) is the differential scattering cross section averaged over the two possible polarizations. For the purpose of modeling the response, we used a software package called Far Field Mie Scattering  to provide the values of i(θ) for specified particle and illumination conditions. (The formula in Ref. [i(θ) as the sum of the contributions from the two possible polarizations, hence the factor of 2 instead of 4 in the denominator of The two vertical lines in  in Ref.  defines A1 presented by the instrument can be compared directly to the function given by the model in t2 factor in The value of spa in spa so that the response predicted by δM can be estimated by measuring water filled cuvette in holders 1 and 2 after performing an auto zero function with all holders empty. To a very good approximation the absorbance and scattering of water is close to zero. Therefore comparing sa and ma vanish, we obtain the relation A1 and A2 are the absorbencies measured in holder 1 and holder 2 respectively. The data is shown in δM is shown in δM differs from 1 by less than 1 % over the range of wavelengths 400 nm to 700 nm. The factor is slightly greater than 1 as would be expected for a reflecting surface placed in front of the sample port. The factor δM will be neglected in the subsequent discussion.The response of the instrument to the sample in cuvette holder 2 can be modeled in the same way as the response to the cuvette in holder 1. The only changes are in the value of the instrument acceptance aperture in sa, due to scattering and the molecular absorption, ma. In the case of holder 1, the sphere accepts a small portion of the scattered flux exiting the cuvette while in the case of holder 2 the sphere accepts almost all of the flux exiting the cuvette. Fluorescence was neglected. sa = 0) and no molecular absorption (ma = 0). The two equations, sa, and molecular absorption ma.However, the form of In order to test the utility of spa. We use the approximation 10x = 1 – x ln x « 1, and obtain the following approximate relations for As discussed previously, to a good approximation the magnification factor is not changed appreciably when a cuvette is placed in front of the IS entrance aperture. In that case, t to the measured absorbance of the buffer in the cuvette placed in holder 1. Subtracting the measured buffer absorbance from the absorbance in holder 1 and holder 2 gives the final relation between measured absorbencies and the suspension propertiesspa ≈ 0 for holder 1 and sa and ma are not small, a slightly more complicated analysis is required. Assuming again that in holder 1, the value of spa is approximately 0, The last terms on the right side of sa, we obtain another relation using δM set to 1.Making the assumption that in holder 2, the value of sa and ma. Note that to first order the right side of sa. Therefore a good start is to assume a reasonable value for saand use ma at each value of the wavelength. This can be done using an algorithm which finds the zero of a specified function. The resulting values of ma at different wavelengths are inserted into sa. If needed, the new values of sa can be put back into ma. This iterative process yields a self consistent set of values of ma and sa. The procedure works well because ma and is not sensitive to sa. The above procedure is applicable to larger values of ma and sa and extends the analysis used in 4 and suspended in a solution containing a 50 fold dilution of SRM 1932 (fluorescein solution) in acetate buffer. The pH of the acetate buffer is close to 5 thus minimizing fluorescein fluorescence. The solid trace in ma. The estimated value of ma is shown by the solid trace in ma obtained from the suspension and the ma obtained from the equivalent fluorescein solution is good. The solid trace in ma from the solid trace in sa in ma shown by the solid trace in ma was subtracted from sa and ma is valid. However, as discussed in conjunction with Chlorella fusca var. fusca (UTEX number 343) was obtained from the Culture Collection of Algae, University of Texas at Austin. This organism was selected according to its ecological relevance and ease of culture in the laboratory [3, 0.17 mmol/L CaCl2, 0.3 mmol/L MgSO4, 0.43 mmol/L K2HPO4, 1.29 mmol/L KH2PO4 and 0.43 mmol/L NaCl, pH 6.8) and supplemented with 1g/L of Proteose Peptone. All cultures were started from stock cultures initiated from single alga grown on semi-solid plates of the appropriate media containing 3 % agar. Newly transferred cultures were incubated at 20 °C to 25 °C under a cool-white fluorescent lamp for 12 h and then in the dark for 12 h, allowing cells to grow until a desired population density was achieved, usually at 1,000,000 cells per mL. The possible contamination and cell density were monitored and counted with a microscope.boratory . Cultureθ ≤ 20. Inserting i (θ) displayed in 6 cm–3, gives sa = 0.41. This value is smaller than the value sa = 0.65 derived from measurements  and the analyte properties . Approximate forms of the two equations are used to analyze several systems consisting of scatterers and absorbers. The results suggest that it is possible to separate the absorption and scattering contributions. Furthermore, the results with microalgae suggest that the two quantities sa, ma are independent characteristics of the microalgae suspension. The quantity ma gives information about the electronic states of the absorbing chlorophyll molecules, while the quantity sa may provide information about the packing of the chromophores inside the microalgae cells. Further work is needed to clarify the systematic uncertainties inherent in the measurement model. The most significant of these uncertainties are the estimates of the partial cross sections spa and An analysis of the measurement process in a spectrometer with an integrating sphere (IS) detector lead to a procedure for separating the contributions to the measured absorbance due to scattering and the molecular absorption. The analysis hinges on the interpretation of absorbance measured for a cuvette placed in two holders in the spectrometer. Holder 1 is the normal position, and holder 2 places the cuvette at the entrance aperture of the IS detector.


It has always been a challenge to reconstruct large bone gaps. The aim of this case report is to highlight the success of homologous maternal bone grafting in a large cystic lesion. A six and half years old boy presented to us with an aneurysmal bone cyst (ABC) of the right radius, not amenable to curettage. We excised the lesion in toto, which created an 11 cm bone loss. Considering the age of the patient, we reconstructed the bone gap with maternal fibular graft. Accordingly, 12 cm of fibular graft was harvested and fashioned to fit into the bone gap. It was fixed with an intramedullary K-wire. No cancellous graft was used in the procedure. The limb was kept in the above elbow cast till incorporation of the fibula was noted on the radiographs. Six months following surgery the skiagram showed that the fibula was incorporated. Mobilization of the elbow and wrist was started along with strengthening of the forearm muscles. K-wire was removed at nine months. At the latest follow up of 24 months, the fibula is fully incorporated, the child regained full range of motion and strength of elbow. We discuss the techniques adopted in this particular case along with the review of literature. Aneurysmal bone cyst (ABC) is a rare non-neoplastic expansile osteolytic bone lesion of unknown etiology. Aneurysmal and solitary bone cysts develop most commonly during skeletal growth. The annual incidence of primary aneurysmal bone cyst is 4 per 100 individuals. The male to female ratio is 1:1.04, and the median age is 13 years  . AlthougWe report a case of homologous maternal bone grafting after excision of a large benign cystic lesion involving the right radius bone in a boy of six and half years which was not amenable to curettage. We suggest that maternal fibular allograft is a possible option for treating a large gap after resection of a bone cyst in a pediatric age group.A six and half year old boy referred to us from another center had complaints of an insidious onset of pain in his right forearm, which initially was less intense. The parents ignored it initially thinking it might be due to his excessive playful nature and cycling. They had a delay of three and half months to consult a doctor in their town when the child complained of an increasing pain. In the meantime, there appeared some swelling in his forearm, which was gradually progressing. A X-ray was done  which reThe tumor was expansile with papery thin cortices and hence was not amenable to curettage. It was decided to do wide resection of the tumor. Reconstruction of the radius following tumor resection can be done with different techniques. First to use child’s own fibula may be considered as vascularized or nonvascularized pattern. Second, the cadaveric allograft. Third, an allogenic allograft from the mother. The parents were informed regarding all the options for reconstructing the radius following excision of the tumor. We were a bit concerned with regard to the diameter of child’s own fibula to be used with the radius because of the possible size mismatch as well as the surgical trauma at two sites. The parents were reluctant to use the allograft stored in the bone bank and hence opted for the mother’s fibula. A written consent was taken from both the parents. Two operating tables were used with two surgical teams. The mother’s surgery was commenced after exposing the tumor in the child and establishing length. Both the surgeries were conducted under tourniquet to reduce blood loss.The radius was exposed using the Henry’s approach with around 15 cm long longitudinal incision along the line joining the lateral side of biceps tendon to the radial styloid process. After incising the deep fascia, a plan was developed between the brachioradialis and flexor carpi radialis. Proximally a plane was developed between the pronator teres and brachioradialis. The superficial radial nerve, radial artery, and poster interosseous nerve all were secured. Periosteum was elevated and was tagged. The exposed tumor length was found to be 11 cm long. The tumor was completely excised .The mother was screened before the surgery and was found to be free of any diseases. It was decided to harvest 12 cm of fibula. A linear incision was made just posterior to the fibula. A plane was developed between the peroneal and the soleus muscles. The muscles as well as the interosseous membrane attached to the fibula were stripped off. The required length of the fibula was taken out . The harn = 46) to those from paternal donors (n = 50). At 5 years, recipients of maternal hematopoietic cells had a significantly higher overall survival than patients receiving paternal grafts  [Aneurysmal and solitary bone cysts develop most commonly during skeletal growth. The stage 1 ABC can be treated with intralesional curettage , the com= 0.006) . We coul= 0.006) . At 12 w= 0.006) . It has = 0.006) . In our The authors declare no conflict of interest in regard with this paper.


There is a need for new knowledge regarding determinants of a successful implementation of new methods in health care. The role of a receptive context for change to support effective diffusion has been underlined, and could be studied by assessing the organizational climate. The aim of this study was to assess the association between organizational climate when a computer-based lifestyle intervention tool (CLT) was introduced in primary health care (PHC) and the implementation outcome in terms of how the tool was perceived and used after 2 years.The CLT was offered to 32 PHC units in Sweden, of which 22 units agreed to participate in the study. Before the introduction of the CLT, the creative climate at each participating unit was assessed. After 24 months, a follow-up questionnaire was distributed to the staff to assess how the CLT was perceived and how it was used. A question on the perceived need for the CLT was also included.The units were divided into three groups according to the creative climate: high, medium and low. The main finding was that the units identified as having a positive creative climate demonstrated more frequent use and more positive perceptions regarding the new tool than those with the least positive creative climate. More positive perceptions were seen at both individual and unit levels.According to the results from this study there is an association between organizational climate at baseline and implementation outcome after 2 years when a tool for lifestyle intervention is introduced in PHC in Sweden. Further studies are needed before measurement of organizational climate at baseline can be recommended in order to predict implementation outcome. Factors influencing the implementation of new methods in health care have been studied, but there is still a lack of knowledge regarding determinants of a successful implementation. The role of context has been highlighted, and is one essential part in the Promoting Action on Research Implementation in Health Services (PARIHS) framework; implementation success is considered to be a function of evidence, context and facilitation . CummingIn Sweden, health care has an obligation not only to provide medical care but also to address lifestyle issues in order to prevent illness and promote health . PreventIf there is an association between organizational climate and willingness to adopt a new way of working, climate could be seen as an implementation facilitator, and a climate assessment could help in developing a tailored implementation strategy. Organizational climate has earlier been found to be associated with youth outcomes in child welfare systems , but to The aim of this study was to assess the association between organizational climate when a tool for lifestyle intervention was introduced in PHC and implementation outcome in terms of how the tool was perceived and used after 2 years.In 2008–2010, the CLT was offered to all 32 PHC units  and other health care professionals) in Östergötland County, Sweden, that had not yet tried it. Of these, 22 units agreed to participate in the study.The CLT consists of a lifestyle assessment performed on a touch-screen computer, and provides tailored advice to the patient, based on their individual answers. Staff members at the PHC unit are encouraged to refer their patients (aged ≥18 years) to the computer, and to give them the opportunity to discuss the results and provided advice. The CLT has been described in detail previously .The implementation strategy used was based on Rogers’ innovation–decision process including knowledge, persuasion, decision and implementation . The impBefore the first visit at each unit, a questionnaire was sent to all staff members who meet patients in their daily work (administrative staff excluded) to assess the organizational climate. The Creative Climate Questionnaire (CCQ) developed by Ekvall was found to be feasible for the study . The insWhen the CLT had been in operation for 24 months, another questionnaire was sent to the same staff categories. Respondents were regarded as a closed cohort, so that only those who had received the first questionnaire were included in the study population for the second questionnaire. As perceived need for the innovation has been found to be an important predictor for implementation , there wt-test. Units with a higher number of dimensions exceeding than falling short to the reference values were defined as Hi, units with less than six more dimensions falling short to than exceeding the reference values were defined as Med and units with at least six more dimensions falling short to than exceeding the reference values were defined as Lo. This resulted in 4 units in group Hi, 15 units in group Med,and 3 units in group low. See also Table The CCQ assessment at baseline resulted in a mean value for each CCQ dimension, as suggested by Ekvall et al. . Based oAssociations between perceived need for the CLT and the CCQ dimensions were analysed with Spearman’s rank correlation coefficient. The Kruskall-Wallis test was used to calculate mean ranks regarding perceived need. Generalized Estimating Equations (GEE), which allows for analysis of clustered data, was used to calculate the Wald Chi-Square test in order to compare the distribution of responses to the follow-up questionnaire among the individual staff members from the three CCQ groups. Statistical analyses were performed using the computer-based analysis program, Statistical Package for the Social Sciences (SPSS) version 22.0. Statistical significance was set at p ≤ 0.05.The study was carried out in compliance with the Helsinki Declaration and was approved by the Regional Ethical Review Board in Linköping, Sweden (Dnr Ö 16–08). As the participants were staff members, written consent was not required according to Swedish regulations (SFS 2003:460).The average response rate was 53 % (range 30–81 %) at baseline and 52 % (range 20–86 %) at follow-up. The total number of respondents was 322 at baseline and 239 at follow-up. To be included at baseline, the responder had to have completed the CCQ instrument, leaving 275 (45 %) respondents for the analysis. An analysis of the drop-outs showed no differences between responders and the entire sample in terms of profession or gender, except that at baseline, the proportion of GPs was lower among the responders (12 %) than in the entire sample (20 %). CCQ scores for the units in group Hi and group Lo are shown in Table p = 0.004). The mean ranks for each unit are presented in Table p = 0.060, p = 0.808). Group Hi showed within-group differences (p = 0.003). It was found that the unit with the lowest perceived need was one of the units in the Hi group; this unit was excluded from further analysis, leaving three units in group Hi, which thus was homogeneous regarding perceived need (p = 0.481). The unit with lowest perceived need was also found to score low on perceptions and use. The question capturing use in terms of frequency of referral to the CLT showed significantly higher levels of use in group Hi compared with group Lo (p < 0.001) as shown in Table p = 0.002) and that they believed the CLT could influence patients’ lifestyles (p < 0.001).At follow-up, internal non-response occurred for some of the questions; the number of responders for each question is shown in Tables p = 0.006), use of the CLT was more supported (p < 0.001), was perceived to a higher degree to facilitate the work with lifestyle issues (p < 0.001), and was seen as an important part of the work with lifestyle issues (p = 0.001), compared with group Lo.For questions regarding perceptions at the unit level, group Hi was significantly more positive than group Lo for all four items assessed Table . Among sThe aim of the study was to assess the association between the creative climate at baseline and perceptions and use of a tool for lifestyle intervention in PHC 2 years after its introduction. The main finding was that the units having a positive creative climate (group Hi) adopted the new tool to a higher degree than those with the least positive creative climate (group Lo). Differences were found regarding use at the individual level, and regarding perceptions at both the individual and unit levels. This result was based on self-reported data, and, at the individual level, concerned use in terms of frequency of referral, and perceptions of the CLT such as facilitating work with lifestyle issues and being an effective way to influence lifestyle. At the unit level, staff in group Hi were found to discuss the CLT, support its use and find that it facilitated work with lifestyle issues at the unit.Staff in group Hi did refer patients to the CLT to a higher degree than staff in group Lo, but only one third of the respondents in group Hi referred patients more than once a month. This could not be considered a frequent use of the CLT. The fact that staff members express positive perceptions and seem to have adopted the new tool, but do not use it on a regular basis, could be explained in terms of conceptual or instrumental use, terms often applied in the context of research use . ConceptIn our study the unit with the lowest level of perceived need showed high scores on creative climate, but low scores on perceptions and use of the innovation. Previous research has shown that a certain level of perceived need is important for an innovation to be successfully implemented . If the Implementation is known to be a complex process, and there might have been other factors influencing the outcome, which could be seen as a limitation of the study. For example, adopter characteristics, outer context or the presence of opinion leaders, all potentially influencing factors according to Greenhalgh et al. , were noMeasuring creative climate using the CCQ is one way of assessing context. An advantage with the CCQ instrument is that it was originally developed in Sweden, and the disadvantages associated with translating, such as misinterpretation of questions, are avoided. The instrument has also been used and found feasible in other studies in Swedish health care settings –16. CreaThe unit with the lowest perceived need and the highest creative climate was excluded from further analysis. A lack of perceived need at this stage, 2 years after the introduction of the CLT, was interpreted to mean that other ways of handling lifestyle issues were available, which made the CLT unnecessary and thus not used at all. Thus, the unit differed in such an important way from the other units in the CCQ Hi group that it was considered most appropriate to exclude it.According to the results from this study there is an association between organizational climate at baseline and implementation outcome after 2 years when a tool for lifestyle intervention is introduced in PHC in Sweden. Since the findings are based on self-reports and the use of the CLT was relatively low, further studies are needed before measurement of organizational climate at baseline can be recommended in order to predict implementation outcome.


Background: Sample size calculations are an important tool for planning epidemiological studies. Large sample sizes are often required in Mendelian randomization investigations.Methods and results: Resources are provided for investigators to perform sample size and power calculations for Mendelian randomization with a binary outcome. We initially provide formulae for the continuous outcome case, and then analogous formulae for the binary outcome case. The formulae are valid for a single instrumental variable, which may be a single genetic variant or an allele score comprising multiple variants. Graphs are provided to give the required sample size for 80% power for given values of the causal effect of the risk factor on the outcome and of the squared correlation between the risk factor and instrumental variable. R code and an online calculator tool are made available for calculating the sample size needed for a chosen power level given these parameters, as well as the power given the chosen sample size and these parameters.Conclusions: The sample size required for a given power of Mendelian randomization investigation depends greatly on the proportion of variance in the risk factor explained by the instrumental variable. The inclusion of multiple variants into an allele score to explain more of the variance in the risk factor will improve power, however care must be taken not to introduce bias by the inclusion of invalid variants. Resources are provided for investigators to perform sample size and power calculations for Mendelian randomization with a binary outcome.The sample size required for a given power level is greater with a binary outcome than a continuous outcome, and is highly dependent on the proportion of the variance in the risk factor explained by the instrumental variable.Sample size calculations are an important part of experimental design. They inform an investigator of the expected power of a given analysis to reject the null hypothesis. If the power of an analysis is low, then not only is the probability of rejecting the null hypothesis low, but when the null hypothesis is rejected, the posterior probability that the rejection of the null hypothesis is not simply a chance finding is low.,Mendelian randomization is the use of genetic variants as instrumental variables for assessing the causal effect of a risk factor on an outcome from observational data.Sample size calculations have been previously presented for Mendelian randomization experiments with continuous outcomes. Calculations based on asymptotic statistical theory have been presented with a single instrumental variable (IV), whether that IV is a single genetic variant or an allele score.et al.We give results for the asymptotic variance of IV estimators with a single IV, and for the resulting sample size needed in a Mendelian randomization study to obtain a given power level. We initially present formulae with a continuous outcome .Other estimation approaches are possible with a binary outcomeRY = Y – β1. X is the residual of the outcome on subtraction of the causal effect of the risk factor, and X and the IV G.R2) in the regression of the risk factor on the IV is an estimate of With a single IV and a continuous outcome, the IV estimates from the ratio, two-stage least squares (2SLS) and limited information maximum likelihood (LIML) methods coincide.X and the outcome Y is given by the formula:a and the power desired to test the null hypothesis is 1−β, then the sample size required to test a causal effect of size β1 using IV analysis is:z is a quantile function, so that zα is the 100α percentile point on the standard normal distribution. If the significance level is 0.05 and the power is 0.8, then the sample size to test for a change of β1 standard deviations in Y per standard deviation increase in X is:α) = α).The asymptotic variance of the conventional regression  estimator of the association between the risk factor 1 = 0.05, 0.1, 0.15, 0.2, 0.25, 0.3 and the sample size N = 1000 to 10 000. In 1 = 0.2 and vary the squared correlation R2 statistic increases).We use these formulae to construct power curves for Mendelian randomization using a significance level of 0.05. In 1) and squared correlation  ≈ G is 0 and the variance is 1, so that N, where N is the sample size. The square of the coefficient X) 1 per standard deviation increase in X for 80% power with a significance level of 0.05 is therefore1 is a log odds ratio. If there are to be an equal number of cases and controls, 1 with a significance level of 0.05 is:Web Appendix (available as Supplementary data at IJE online).With a single IV and a binary outcome, the same IV estimatoring term . The asy1 and We use these approximations to calculate the number of cases needed to obtain 80% power in a Mendelian randomization analysis with a binary outcome for different values of βAppendix (available as Supplementary data at IJE online). This code enables the calculation of the sample size required for a chosen power level given the values of β1 and 1, An Ri is:x) = (exp(x) / 1 + exp(x)) is the inverse of the logit function and β1 is the log odds ratio per unit  increase in the risk factor. The genetic variant is modelled by a standard normal distribution; it can be regarded as a standardized weighted allele score. The parametric relationship between X, G and ρGX ensures that the proportion of variance in the risk factor explained by the instrumental variable in a large sample is Web Appendix (available as Supplementary data at IJE online).In order to validate the estimates of sample size and power, we simulate data on a genetic variant, a continuous risk factor and an outcome. The data-generating model for individuals indexed by 0 = −3 so that the outcome has a prevalence of about 5% in the population from which the case-control sample is taken. We take three values of β1 = 0.1, 0.2, 0.3, three values of We set βThe 95% confidence interval for the ratio method used in calculating the power of the simulation method is constructed using Fieller’s method,Results from the validation simulation are given in Web Table A1 (available as Supplementary data at IJE online). In comparing estimates of power with equal numbers of cases, greater power is achieved when there is a case:control ratio of 1:2 than with a ratio of 1:1. However, when the total sample size is fixed, the estimate of power is greatest when the numbers of cases and controls are equal. This can be seen by comparing estimates with 30 000 cases and a ratio of 1:1, and with 20 000 cases and a ratio of 1:2.We note that estimates of power from the formula of Web Appendix . No substantial differences were observed from the validation simulation in the main paper when the instrumental variable was discrete. When there was confounding, estimates from the analytical formula slightly overestimated power, particularly when the confounding was in the same direction as the causal effect. However, this overestimation was slight . As the magnitude of confounding is not possible to estimate in applied practice, conservative estimates of the correlation and causal effect parameters used in power calculations are recommended, particularly if confounding is thought to be substantial.In response to concerns from a reviewer that the power estimates may not be valid with a discrete instrumental variable (such as a single nucleotide polymorphism) or when there is confounding, additional validation simulations were performed in these scenarios. Results are given in the In this paper, we have provided information on sample sizes and power calculations in a Mendelian randomization analysis with a single IV and a binary outcome. We have shown in the continuous setting how the power depends on the magnitude of causal effect and the proportion of variance in the risk factor explained by the IV. With a binary outcome, the precision of the coefficient in the regression of the outcome on the IV is reduced compared with a continuous outcome, as the outcome can only take two values. As a result, the required sample sizes to obtain 80% power are much larger.For a given applied example, the magnitude of the causal effect of a risk factor is fixed, as is the expected proportion of variance in the risk factor explained by each variant. However, the expected proportion of variance in the risk factor explained by the IV depends on the choice of IV. The required sample size for a given power level can be reduced  by including more genetic variants into the IV. This can be achieved by using multiple variants as separate IVs,If there are missing data, this may adversely impact the power of an analysis. When there are multiple genetic variants, individuals with sporadic missing genetic data can be included in an analysis using an imputation approach.The calculations in this paper make several assumptions. The distribution of the IV estimator is assumed to be well approximated by a normal distribution. This is known to be a poor approximation when the IV is weak;,The ratio method used in this paper has been criticized for use with binary outcomes to estimate an odds ratio.Although the sample sizes required in Mendelian randomization experiments are often large, it is not always necessary to measure the risk factor on all of the participants in a study. Simulations have shown that, in some cases, 90% of the power of the complete-data analysis can be obtained while only measuring the risk factor for 10% of participants.Supplementary data are available at IJE online.Conflict of interest: None declared.


The purpose of this study was to determine the maximum proton kinetic energy required to treat a given percentage of patients eligible for stereotactic radiosurgery (SRS) with coplanar arc‐based proton therapy, contingent upon the number and location of gantry angles used. Treatment plans from 100 consecutive patients treated with SRS at the University of Wisconsin Carbone Cancer Center between June of 2007 and March of 2010 were analyzed. For each target volume within each patient, in‐house software was used to place proton pencil beam spots over the distal surface of the target volume from 51 equally‐spaced gantry angles of up to 360°. For each beam spot, the radiological path length from the surface of the patient to the distal boundary of the target was then calculated along a ray from the gantry location to the location of the beam spot. This data was used to generate a maximum proton energy requirement for each patient as a function of the arc length that would be spanned by the gantry angles used in a given treatment. If only a single treatment angle is required, 100% of the patients included in the study could be treated by a proton beam with a maximum kinetic energy of 118 MeV. As the length of the treatment arc is increased to 90°, 180°, 270°, and 360°, the maximum energy requirement increases to 127, 145, 156, and 179 MeV, respectively. A very high percentage of SRS patients could be treated at relatively low proton energies if the gantry angles used in the treatment plan do not span a large treatment arc. Maximum proton kinetic energy requirements increase linearly with size of the treatment arc.PACS numbers: 87.55.‐x, 87.53.Ly, 87.53.Bn The dosimetric characteristics of protons give them several theoretical advantages over photons for use in radiation therapy, such as their finite range and Bragg peak. Such considerations have been widely reported on in the literature. However, proton therapy is still only available to a relatively small percentage of radiation therapy patients. As of February 2011, there were only nine operating proton facilities in the United States, compared to over 2000 radiation therapy treatment centers. The primary reason that proton therapy has such limited availability is that the equipment used in proton therapy is much larger and more expensive than the equipment used in traditional photon radiation therapy. Several novel accelerator designs have been proposed for use in proton therapy, as will be discussed in more detail below. In all cases, the maximum energy required of the accelerator is the critical factor in the size and cost of the treatment system. This is due to the fact that the costs of the accelerator and magnet systems increase as beam energy increases., make them particularly attractive for use in SRS. Furthermore, those treatment volumes that are close to the skull can most benefit from proton radiotherapy because the entrance path, and therefore the integral dose to normal brain tissue, is reduced. Tumors closer to the surface need less energy, but could perhaps benefit from shallow angle arc delivery to spread out the entrance dose to a wider area.In 2009, a paper was published that quantified the maximum proton kinetic energy requirements for a set of 100 radiation therapy patients that were randomly selected to be representative of the total pool of patients eligible for radiation therapy.,4, m and the dielectric wall accelerator (DWA).The increased cost of protons relative to photons,8 anIt has been shown that approximately 90% to 95% of patients eligible for proton therapy can be treated with coplanar arc‐based delivery with proton energies at or below 200 MeV.In this study, the maximum proton kinetic energy that would be required for a treatment system dedicated to brain SRS patients is estimated. This value depends strongly on the gantry angles from which the treatment beam is incident. While only coplanar directions are used in this study, it is likely that entrance directions that minimize the path length to the tumor are optimal. Thus, the estimates presented here represent a conservative estimate of the maximum energy needed. Further discussion of non‐coplanar beam directions is presented in the following sections below. This study presents a comprehensive analysis to determine the distribution of required energies as a function of the length of the coplanar treatment arc.0.0703 cm×0.0703 cm×0.125 cm were used, where the last dimension is the slice thickness. For each target ROI in each patient, maximum proton energies were calculated for 51 coplanar gantry angles equally spaced over 360°. A discretization of 51 beam angles was chosen because it coincides with that used by the TomoTherapy rotational treatment planning software , with which there exists extensive clinical experience, and because that number of beam angles was on the high end of what was computationally feasible for this study.One hundred patients treated consecutively from June 2007 through March 2010 with photon SRS at the University of Wisconsin Carbone Cancer Center were included in this study. All patients had diseases of the brain and were treated on a Varian linear accelerator with a tertiary collimator system. A summary of the diseases included is shown in 0.005 g/cm2), adipose tissue (between 0.005 g/cm2 and 1.100 g/cm2), muscle (between 1.100 g/cm2 and 1.500 g/cm2), or bone (greater than 1.500 g/cm2). These cutoffs are based on clinical values and have a negligible effect on the results of this study. Each voxel was then scaled by the ratio of the mass stopping power of its tissue type to that of water. The scaling factors that were used were the average value taken over the energy range 50 MeV to 250 MeV, as reported by NIST.dmax,i,j, where i is the index for the target ROI and j is the index for the gantry angle for the given patient, as shown in The procedure for calculating the maximum proton energy for a single gantry angle and a single target ROI is as follows. Voxels were classified based on their density, and were considered to be air  that had a Bragg peak depth that was closest to dmax,i,j. Beamlets were calculated between 50 and 250 MeV using Monte Carlo simulation with MCNPX, which has been benchmarked with experiment for proton therapy and other physics applications,(–) with an energy separation of 1 MeV. This method essentially places the Bragg peak on the distal bounding of the target, which gives an estimate of the maximum energy required. For each of the 100 patients, Emax,i,j was calculated for all i target ROIs and all 51 gantry angles. It was then possible to determine the maximum proton energy required to treat each patient as a function of the arc length ϕ through which treatment was required. A search was done for the minimum path length necessary to deliver the required arc segment anywhere within the 360° set of possible coplanar beam directions. If we let k be the index for the set of all groups of consecutive treatment angles spanning ϕ degrees and we let n serve as the patient index, then this maximum proton kinetic energy value for a given treatment arc length ϕ can be represented mathematically as En(ϕ)=maxi[mink(j)]. These values were calculated for several different values of ϕ, namely 1°, 90°, 180°, 270°, and 360°, and the results are shown in the following section. An arc length of 1° represents a single beam direction.Each maximum path length ications,–23 wAn example may help to clarify the procedure. Suppose ϕ is fixed to be 90°. Consider a single ROI in a single patient. First, the maximum proton energy required to reach the distal edge of the target was calculated for the arc spanning 0° to 90°. Next, the arc was shifted by 7.059° to get an arc spanning the angles 7.059° to 97.059°, and the maximum proton energy was calculated for that arc. This procedure was repeated until a maximum energy value was obtained for all 51 possible arcs spanning 90°. The minimum was then taken over this set of 51 maximum energy values to give the proton energy requirement for that ROI in that patient. This procedure was repeated with different values of ϕ for all ROIs and all patients to produce the results presented in the following section. It is important to note that this method of using arcs for this analysis does not necessarily require arc treatment for these results to be applicable. Included within the arc treatment results are static gantry angle results. The arc method simply ensures that all possible coplanar treatment angles (discretized into 51 beam angles for tractability) were considered, and that an upper bound was set on the proton energy requirements. Note that since all smaller arcs are inherently included in any larger arcs, the maximum energy requirement is necessarily an increasing function of ϕ.The results of the calculations described above are shown in It is clear from these results that the energy requirements for proton SRS in brain patients are considerably less than for the general population of all patients eligible for proton radiotherapy. For example, the energy requirement to treat nearly 100% of eligible patients with proton therapy over a 180° treatment arc is approximately 240 MeV.It is clear from the discussion above that as the required length of the treatment arc increases, so does the maximum proton energy requirement. As can be seen in There is no mention in the analysis above of the avoidance of critical structures, which is clearly an extremely important consideration in stereotactic radiosurgery. However, this study does not seek to specify desirable beam angles for individual treatment plans. Certainly, some angles included in the analyses presented would never be used in an actual treatment. By considering all possible treatment angles (discretized into 51 beam directions for tractability), this study sets an upper bound on the energy requirements – the stated purpose of the study. Removing certain angles from the calculations based on critical structure constraints would have no effect on the results.This study included only coplanar beam angles. In the current practice of photon stereotactic radiosurgery, non‐coplanar beam angles are used regularly . Considering such angles would likely change the results presented here. This study was meant to provide justification for a maximum energy selection in a coplanar arc‐based SRS proton unit. The coplanar design was selected to minimize mechanical complications in the unit. It is anticipated that the dosimetric properties of protons may eliminate the need for using non‐coplanar beam angles and the additional hardware complications that they introduce. Such considerations are beyond the scope of this paper, but are certainly an area for further investigations. Nevertheless, noncoplanar arcs chosen to minimize integral dose would require even less energy, and this study thus represents a conservative estimate for the energy required for non‐coplanar proton SRS.A detailed analysis of the exact cost implications of increased energy for a proton system is beyond the scope of this paper because the total impact will vary with the accelerator technology under consideration. For example, in a cyclotron‐based proton center, increased energy would lead to larger magnet systems, which represent a substantial portion of the cost of a cyclotron. Nonetheless, it is worthwhile to consider one specific example to get a sense of the magnitude of the cost implications. This paper was written with the DWA‐based system that is under development in mind, and it is this system that will be used as an example. The DWA has a fixed energy gradient per unit length, and the cost of the accelerator scales linearly with its length. Thus, the cost of the accelerator scales linearly with the required energy. An increase in the required energy from 125 MeV to 250 MeV would double the cost of the accelerator. Of course, other system components whose cost is not affected by the required proton energy must be considered, such as the building, control system, imaging system, couch, and planning system. However, at least for the DWA example, the accelerator itself represents the majority of the cost of the entire proton facility (as much as 80%). If the accelerator is mounted on a gantry, the gantry can represent a large portion of the total facility cost. For a gantry‐based system, the accelerator may represent a smaller fraction of the total facility cost, perhaps closer to 50%; doubling the required energy would increase the cost of the total treatment facility by at least 50% to 80%. This increase considers only the accelerator, and does not take into account additional cost increases associated with a larger treatment room, higher magnetic field requirements for scanning magnets, and increased shielding requirements (for more details regarding the impact on shielding see Ref. 1). These concerns would not have as great an impact as that of the cost of the accelerator itself, but they would serve to make the impact that the required proton energy has on the overall price of the system even more substantial.The largest factor limiting patient access to proton radiation therapy is the cost of the accelerator systems that create clinically useful proton beams. For nearly all systems either in use or proposed for use in proton radiation therapy, the maximum energy that must be achieved plays a major role in the size and cost of the accelerator and magnet systems used to transport the beam. Furthermore, certain disease sites receive much greater benefit from protons relative to photons than others. Specifically, cranial diseases have been shown to be well suited for proton therapy. This study attempted to quantify the maximum energy that would need to be reached by a proton accelerator to treat the majority of patients with brain lesions using coplanar arc‐based proton stereotactic radiosurgery. By using a randomized patient population of 100 photon SRS patients, systematic inclusion biases were eliminated. It was shown that a proton system dedicated to cranial SRS cases could be conceived with a much lower maximum attainable energy than conventional proton systems. It is possible that this reduction in energy could lead to substantial reductions in the size and cost of such a dedicated SRS system relative to other proton therapy systems.This work was supported by the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program and by a National Science Foundation Graduate Fellowship. This work utilized the National Science Foundation and University of Wisconsin‐funded Grid Laboratory of Wisconsin (GLOW) computer cluster (NSF award number 0320708). Support from an NIH Training Grant T32 CA09206 is acknowledged.


This study aimed to evaluate the applicability of the principles and informed consent form (ICF) template proposed by the Strategic Initiative for Developing Capacity in Ethical Review (SIDCER) in a clinical pharmacokinetic study by comparing the volunteers’ understanding of the enhanced ICF (developed based on the SIDCER methodology) and the conventional ICF .A total of 550 volunteers were randomly assigned to read either the enhanced ICF or the conventional ICF (1:1) in a mock informed consent approach and subsequently performed the post-test questionnaire. The primary endpoint was the proportion of the participants who had the post-test score of ≥80 %; the secondary endpoints were the total score of the post-test, the score of the categorized ICF elements, and time spent for participation.p < 0.001). The participants in the enhanced ICF group obtained higher scores and spent less time in reading the given ICF and answering the post-test than those in the conventional ICF group .The proportion of the participants in the enhanced ICF group who achieved the primary endpoint was significantly higher than the conventional ICF group (82.2 % vs. 60.4 %, The enhanced ICF improved the understanding of the participants in this study. This demonstrates the applicability of the SIDCER ICF principles and its template in the development of an enhanced ICF for improving the quality of ICFs and subjects’ understanding in clinical research.Trial registration: TCTR20140727001 The subjects’ limited understanding of trial information has been a continuing source of concern especially in non-therapeutic studies involving healthy volunteers. After the incident of the TGN1412 study, there has been an increasing concern regarding the validity of informed consent in healthy volunteers in phase I studies. All healthy volunteers who received an intervention in the TGN1412 study ended up in the intensive care unit . This stAn ICF is a required document in clinical studies, which provides information of a particular study to potential research subjects and documents an individual subject’s voluntary consent to participate in research. To date, the quality of ICFs used in clinical studies is still problematic due mainly to extensive length –10, chaoRecently, the Strategic Initiative for Developing Capacity in Ethical Review (SIDCER), an organization launched by the Special Programme for Tropical Disease Research, World Health Organization in 2001, has proposed the SIDCER ICF principles and template for ICF development. The concept and structure of the SIDCER ICF have been refined and finalized in collaboration with researchers and Ethics Committee members mainly from the Forum of Ethical Review Committees in the Asian and Western Pacific region (FERCAP). In short, the SIDCER ICF consists of three principles: (1) completeness of the mandatory ICF content required by international ethics guidelines and regulations, (2) concise information provision which is relevant to a subject’s decision-making and local context, and (3) use of simplified means to effectively convey relevant information to the target population. The SIDCER ICF template for clinical trials has been designed to guide the development of an ICF based on the SIDCER ICF principles . Validation of the SIDCER ICF’s applicability and effectiveness in a variety of clinical studies with different designs is needed. Although the concept is universal, the application and validation must be done in a local language as it plays a major role in the comprehension of research subjects in a reference setting and context.The present study is an empirical study to test the SIDCER ICF’s applicability and effectiveness in Thai and to evaluate the understanding of Thai volunteers. The SIDCER ICF methodology was applied to a clinical pharmacokinetic (PK) drug-drug interaction (DDI) study involving healthy subjects, and the local volunteers’ understanding between the enhanced (SIDCER) ICF and the conventional ICF was compared using a randomized-controlled design.This study was an open-label, randomized-controlled study of the two different ICF interventions (1:1), i.e., the enhanced ICF and the conventional ICF, using a post-test questionnaire as an assessment tool. The clinical study protocol of the PK DDI study entitled “Effect of curcuminoids on the blood level of digoxin in healthy male volunteers”  was used to be the core information for ICF development.Following the SIDCER ICF principles and template, the enhanced ICF was developed (in Thai) based on the abovementioned clinical study protocol. In close observation of the first SIDCER ICF principle, the study protocol was reviewed and the essential information in regard to compliance with internationally recognized regulatory ICF requirements are selected and present in the enhanced ICF. To limit the contents and length of the enhanced form in accordance with the second SIDCER ICF principle, the information in the study protocol was carefully analyzed and summarized, and only relevant information to a subject’s decision-making on research matters was used for ICF development. The refined information was then transformed into a narrative and illustrative format and appropriately inserted into the SIDCER ICF template (where the third SIDCER ICF principle is applied) using local lay language with reference to local context.A four-page enhanced ICF containing 21 required elements was successfully developed  used in the abovementioned PK DDI study was considered as a conventional ICF in the present ICF study. This ICF was previously approved by the Research Ethics Committee of the Faculty of Medicine, Chiang Mai University, 2 years prior to the development of the SIDCER ICF, and it was used in the real informed consent process of that study. It had seven pages containing 15 required elements (Table The post-test questionnaire (in Thai) consisted of 21 short case studies where each case study was designed to illustrate a common practical situation of one element required, followed by a question with three possible answers. It was used as an assessment tool to determine the volunteers’ understanding of each required element after they read a given ICF. All case studies and answer choices were also reviewed and corrected by the principal investigator of the PK DDI study (NH) and two independent laypersons.The primary endpoint was the proportion of the participants who had the post-test score of more than 80 %. The secondary endpoints were the total score of the post-test, the score of each category of elements required Table , and timz-test to detect the 10 % difference between two independent proportions of the primary endpoint (p1 = 0.85 and p2 = 0.75) was applied, with the precision and confidence level of 95 % (α = 0.05) and 80 % power (1 − β = 0.80), using continuity correction with allocation ratio of 1. A sample size of at least 269 subjects is adequate for each group.The estimated sample size was calculated using G*power 3.1.9.2 for Windows. The Volunteers (age > 18) who can read and write Thai were recruited from universities, colleges, cafeterias, hospitals, and markets in Chiang Mai, Thailand. Individuals who had no time to read the entire ICF and do the post-test questionnaire were excluded. All processes were done in an anonymous manner using a subject unique number. The study protocol and all related documents were approved by the Research Ethics Committee of the Faculty of Medicine, Chiang Mai University. All procedures performed in this study were in accordance with the ethical standards of the institutional and national research committee and with the 2013 Helsinki declaration. Written informed consent was obtained from all individual participants prior to the enrollment of the study. This study was registered as TCTR20140727001 via the Thai Clinical Trial Registry.There were two main processes in this study: 1) the process of reading a given ICF and (2) the process of completing the post-test questionnaire. The participants were randomly assigned to read either the enhanced ICF or the conventional ICF  since none of them were normally distributed. Subgroup analyses were performed by applying the chi-square test to determine the impact of genders , generations   and educA total of 550 participants, aged 18–67 years (median age = 24 years), were enrolled: 62 % were female; 66.9 % were under generation Y; and 76 % had educational level 2. Their demographic data are shown in Table p < 0.001). The proportion of the participants in the enhanced ICF group who achieved the primary endpoint was significantly higher than that in the conventional ICF group  . The time spent by the participants in the enhanced ICF group was significantly lesser than that in the other group .The assessment of the secondary endpoints showed that the total score of the post-test and the score of each category in the enhanced ICF group were significantly higher than those in the conventional ICF group . The participants in the enhanced ICF group spent less time but achieved higher scores on the post-test when compare to those in the conventional ICF group .The present study demonstrates the applicability of the SIDCER ICF and its template in the development of an enhanced ICF for the clinical PK trial and its effectiveness in improving the participants’ understanding of information related to the trial. Higher proportions of the participants who read the enhanced ICF obtained the satisfactory level of understanding at 80 % and perfect score in the post-test questionnaire than those who read the conventional ICF . A possible reason for this result is the small number of subjects in the baby boomers generation in comparison to the other generations (Table Although most of our data favored the enhanced ICF, there were two data subgroups that did not fully support our conclusion: the participants in the baby boomers generation and the participants in the educational level 3. Literature points out that each generation has a difference in perspective and perception . It is pns Table , as we dIt should be noted that this study was performed in a mock population so that the level of understanding might be either overestimated, due to the inclusion of only respondents who were willing to read a given ICF, or underestimated, owing to their limited concern for the information regarding study participation. Studies involving real research subjects of clinical studies could provide stronger evidence to support the effectiveness of the SIDCER ICF in enhancing subjects’ understanding of ICFs.Understanding of the participants in this study was improved by the enhanced ICF developed based on the SIDCER ICF principles and template. The results of this study demonstrate the potential of the application of the SIDCER ICF principles and its template in improving the quality of ICFs and subjects’ understanding in clinical research. Further studies to evaluate the applicability and effectiveness of the SIDCER ICF in a variety of clinical studies in different languages and settings are necessary.


Complex Regional Pain Syndrome (CRPS) is a disabling disease that is sometimes difficult to treat. Although spinal cord stimulation (SCS) can reduce pain in most patients with CRPS, some do not achieve the desired reduction in pain. Moreover, the pain reduction can diminish over time even after an initially successful period of SCS. Pain reduction can be regained by increasing the SCS frequency, but this has not been investigated in a prospective trial. This study compares pain reduction using five SCS frequencies  in patients with CRPS to determine which of the modalities is most effective.All patients with a confirmed CRPS diagnosis that have unsuccessfully tried all other therapies and are eligible for SCS, can enroll in this trial (primary implantation group). CRPS patients that already receive SCS therapy, or those previously treated with SCS but with loss of therapeutic effect over time, can also participate (re-implantation group). Once all inclusion criteria are met and written informed consent obtained, patients will undergo a baseline assessment (T0). A 2-week trial with SCS is performed and, if successful, a rechargeable internal pulse generator (IPG) is implanted. For the following 3 months the patient will have standard 40 Hz stimulation therapy before a follow-up assessment (T1) is performed. Those who have completed the T1 assessment will enroll in a 10-week crossover period in which the five SCS frequencies are tested in five periods, each frequency lasting for 2 weeks. At the end of the crossover period, the patient will choose which frequency is to be used for stimulation for an additional 3 months, until the T2 assessment.Currently no trials are available that systematically investigate the importance of variation in frequency during SCS in patients with CRPS. Data from this trial will provide better insight as to whether SCS with a higher frequency, or with burst stimulation, results in more effective pain relief.ISRCTN36655259Current Controlled Trials  Complex Regional Pain Syndrome (CRPS) is defined as a collection of locally appearing painful conditions following a trauma, which mainly occurs distally and exceeds in severity and duration the expected clinical course of the original trauma; this often results in considerably restricted motor function and is characterised by a variable progression over time . The diaThe natural course of the disease is not always favourable, even with a multidisciplinary approach and the use of evidence-based guideline-supported treatment algorithms. CRPS has an estimated incidence of 5.46–26.2 per 100,000 person years (95 % CI: 23.0–29.7) [Although the pathophysiology of CRPS is incompletely understood, several mechanisms are proposed to contribute to this disease such as inflammation, vasomotor dysfunction, and involvement of the central nervous system with features of central sensitisation and neuroplasticity .Some patients with diagnosed CRPS are unresponsive to any conventional therapy, such as physical therapy, medication and invasive interventions such as sympathetic blockade. In these cases there is a clear indication for spinal cord stimulation (SCS) as a last resort therapy to reduce pain. SCS has been performed in many CRPS patients and has shown an evident and clinically relevant pain reduction that can be maintained for a prolonged period of time –12.The exact mechanism of action that occurs during SCS, which results in pain relief, has not been fully elucidated. However, it is known that for neuropathic pain in general, SCS decreases the hyperexcitability of the multimodal wide dynamic range neurons (WDR), increases the release of gamma-aminobutyric acid (GABA) in the dorsal horn and, subsequently, decreases the release of glutamate. Other mechanisms proposed to be involved are activation of an inhibitory descending pathway and involvement of the cholinergic system. Several CRPS-specific mechanisms of SCS are considered to play a pivotal role, such as inhibiting the hyperexcitable central neural circuitry, a decrease in the efferent-sympathetic output and by antidromic activation which, in turn, causes the release of several vasoactive substances, such as nitric oxide, substance P and calcitonin gene-related peptide –15.However, despite these successes some CRPS patients are not responsive or, in others, the pain-reducing effect diminishes over time due to tolerance –12. It iThis study aims to compare the effects of five different SCS modalities in patients with CRPS and determine which frequency is most effective in terms of pain reduction; these frequencies are standard stimulation with 40 Hz , 500 Hz, 1200 Hz, burst and placebo stimulation.This is a prospective randomised, double-blind and placebo-controlled crossover trial. The study is a multi-centre trial including one university hospital and four regional hospitals located throughout the Netherlands. Figure Patients considered for enrollment in this trial must be diagnosed with CRPS that is in accordance with the endorsed IASP criteria at the time of disease onset. We defined two groups of patients that can take part in this trial. The first group (primary implantation group) consists of patients with chronic CRPS who are unresponsive to conventional therapies . The second group (re-implantation group) consists of patients who already have SCS therapy, or were treated with SCS in the past but with loss of therapeutic effect over time. In the re-implantation group it is imperative that the paresthesia, that is or was felt under SCS therapy, has adequate overlap with the painful area.Eligibility for SCS is in accordance with the Dutch CRPS and Neuromodulation Guidelines. These guidelines state that patients must have a mean pain intensity of a least 5, as measured on a visual analogue scale , a CRPS duration of at least 12 months, and no lasting success or complications with conventional therapy. An additional requirement for this study is that the CRPS is located in one extremity only. Exclusion criteria are: anticoagulant drug therapy or disturbed coagulation, age < 18 years, pregnancy, ICD or pacemaker, life expectancy < 1 year, lack of cooperation of the patient, drugs, medication or alcohol addiction, and immune-compromised patients.Approval from the Medical Ethics Committee of Erasmus Medical Center Rotterdam was obtained in August 2011 (Registration number: MEC-201 1-012). The trial was subsequently registered in the Current Controlled Trials register (ISRCTN 36655259). Written informed consent is obtained from all patients before enrollment into the trial.The main study parameters are pain reduction and patient satisfaction. The pain scores are measured with the McGill Pain Questionnaire-Dutch Language Version (MPQ-DLV) , 19 and Secondary outcomes consist of detecting temperature asymmetry by using video thermography imaging –27, and A MicroFet Dynamometer® is used to measure muscle strength of the flexors and extensors of the elbow in case of the upper extremity, and of the knee and the foot in case of CRPS in the lower extremity. The grip strength and the pinch strength is determined by means of a Jamar Hydraulic Hand Dynamometer® and a Jamar Hydraulic Pinch Gauge®, respectively. The pinch strength is measured in two ways: thumb tip to index fingertip, and thumb pad to lateral aspect of middle phalanx of index finger; the biceps and the triceps. In addition, a walking test is performed only in patients that have lower extremity CRPS. This test records how long it takes to cover a 10 m distance when walking at a comfortable and maximum walking pace. Furthermore, the maximum walking distance is assessed during a 2-min walk where the patient is instructed to cover as much distance as possible within these 2 min –40.The types of activity and physical activity level (PAL) of a patient is continuously measured with the VitaMove system  for multiple days (2–3 day), providing a detailed and continuous report on the patient’s energy expenditure, motions and postures over the course of several days –46. ThisArtificial skin blisters are created to measure whether local inflammation is still present in these patients before SCS and the effects stimulation therapy might elicit on the inflammatory profile –56. A blpsychological and social evaluation: Inventory for Social Support (ISS) [Physical activity: the Disabilities of Arm Shoulder and Hand Questionnaire (DASH) [Economic evaluations: The cost analysis is performed from a societal viewpoint in collaboration with the Institute for Medical Technology Assessment of Erasmus University Rotterdam. Three categories of costs are distinguished: 1) Direct costs within the healthcare system, 2) Direct costs outside the healthcare system, and 3) indirect costs outside the healthcare system. These data are collected using diaries and the Trimbos/iMTA questionnaire for Costs associated with Psychiatric Illness (TiC-p) and health consumption, simultaneously with the clinical data and quality of life data. The costs are valued using the Dutch guidelines for cost analysis in healthcare .Multiple questionnaires are filled in by the patient throughout the course of the study to monitor the various dimensions Table . These irt (ISS) , Pain Cart (ISS) –63, RANDrt (ISS) –66, the rt (ISS) , 68 and rt (ISS) , 70. Phye (DASH) , 71, 72 e (DASH) –75. EconProductivity costs: The productivity costs are defined as the costs of absence from paid work due to CRPS, including the impact of compensation mechanisms, the cost of efficiency losses (productivity costs while working at a slower pace) and the costs of hindrance at unpaid work. For this, the three modules of the PRODISQ questionnaire for measuring and valuing productivity costs for unpaid work are used , 77. ForMedication consumption is assessed by taking an inventory of all (pain)medication and dosing the patients use at the time of the T0, T1 and T1 assessment. The pain medication will be stratified into the various medication groups and a the sum dosage of the various pain medication groups will be calculated.By means of MANOVA for repeated measurements within factors, the potential differences in effect of the five different stimulation modalities will be assessed. A minimal detectable effect size (f) of 0.15 on the main primary outcome parameter pain intensity (VAS) was chosen. The required minimum number of participating patients is negatively associated with the correlation between measurements during the cross-over. Unfortunately, no data of previous research on this correlation were available at the time of setting up this study. Therefore, we made an conservative guess and a correlation of 0.6 was chosen. Thus, assuming a power of 0.8 and a significance level (σ) of 0.05 , an a priori sample size of 48 is required.Randomization was performed with a computer based program at the beginning of the trial and no blocks were used since this is not viable in our study design. In our study design all patients in the crossover will be subjected to all five stimulation modalities in random order, resulting in 5! (120) different orders in which the stimulation modalities can be programmed. Only 48 (the required sample size) of these 120 potential different orders are selected at random by the computer to be used.The specific order of the programming for an individual patient is revealed to the local SCS programmer only during each of the five crossover periods. The patient is blinded for the intervention by means of a mask that cannot be seen through. The outcome assessments at the end of each 2-week period are done by means of questionnaires. The statistician who performs the analysis of the measurements and questionnaires is blinded for the allocation key for the treatments for each patient.Data are analyzed using the latest version of IBM SPSS Statistics. Descriptive statistics are used to determine the frequencies of the demographic and secondary outcome parameters, and to describe measures of central tendency and of dispersion, dependent on the shape of their distribution. The Kolmogorov-Smirnov test is used to analyze whether or not the scores on the these parameters are normally distributed. The outcome parameters are analyzed using Mixed Linear Models for repeated measurements within factors model. These Mixed Linear Models model require normality of residuals. These models are however relatively robust against violations of this assumption . TherefoPatients with an indication for neuromodulation are referred by their physicians to the SCS nurses for further evaluation, and to provide them with additional information about the procedure and lifestyle limitations. Also, a psychologist will screen the patient to rule out any psychological contraindication that might influence the outcome of the SCS trial. The patients are contacted by the researcher for trial information and enrollment once all the clinical inclusion criteria for SCS treatment have been met. After obtaining written obtained consent from the patient, the next phase in the trial can commence. It is noteworthy that patients who decline to participate in the trial will still be treated with regular SCS therapy.The patient is invited to our medical centre to participate in various test that are conducted as well as medical history and physical examination. All questionnaires must be filled in by the patient prior to this visit. Table The trial stimulation is conducted at the various hospitals attended by the patients and lasts for 2 weeks. Only experienced physicians are allowed to perform implantation. During the test stimulation the patient is positioned in the prone position and spinal column landmarks are identified with fluoroscopy. Local anaesthetics are used during this procedure; however, a mild sedative or short-acting opioid can be used without compromising the patient’s ability to cooperate during the intra-operative testing. The surgical procedure used is left to the discretion of the physician in charge.The cylindrical percutaneous Octrode™ lead  is primarily used in all patients to gain unilateral stimulation and is positioned under fluoroscopic guidance. The correct position is determined by means of intra-operative stimulation and is deemed successful if the induced paresthesia has an adequate overlap with the painful area. The lead is sutured to the fascia using an anchor. An extension cable is attached to the lead and is tunneled under the skin towards a suitable exit site. A temporary battery is attached to the external part of this extension cable during the trial period.The parameters used for stimulation is up to the SCS nurse in charge, except for the mandatory frequency setting of 40 Hz. All other parameters  are the result of the individual clinical paresthesia mapping. The trial period will generally last for 1 or 2 weeks and is considered successful if a patient has >50 % pain reduction on a VAS and/or has stated that the symptoms are much improved. All patients with a successful trial receive a permanent rechargeable internal pulse generator (IPG) from the Eon family line  under general anaesthesia. The trial extension cable is removed and replaced with a new extension cable that is connected to the IPG. In some instances, a direct connection with the lead and IPG can be made if the length of the lead is sufficient. The pocket location for the IPG is free of choice and can either be in the lower abdomen or in the gluteal are. All materials are removed if a trial is unsuccessful and the patient is then excluded from further follow-up during this trial. The standard stimulation setting is further optimised during the regular checkups in the subsequent weeks. Antibiotic prophylaxis is given during both the trial and implantation in accordance with the local hospital antimicrobial guidelines.Three months after the IPG implantation and therapy with normal tonic 40 Hz SCS, another assessment T1) takes place. This serves as an evaluation of the effects of regular SCS on the previously described tests (Table  takes plThe crossover period consists of five periods (each lasting for 2 weeks) in which the 5 different frequencies are tested. After each period, a small assessment (S1-S5) is done to evaluate the stimulation effects on pain and GPE. A 2-day wash-out period, during which the stimulation is switched off, is incorporated at the beginning of the first 2-week period (S1) and at the end of each period. The purpose of a wash-out period is to objectively determine the baseline pain levels and symptoms of CRPS when they are not masked by SCS, and to minimise the carryover effects of the previous period into the next period. The small assessments (S1-S5) comprise a stimulation evaluation, a pain diary, the McGill Pain Questionnaire and the Global Perceived Effect. Stimulation evaluation requires a patient to keep a stimulation diary in which they must answers four questions; (1) the effect(s) of stimulation on pain in the CRPS effected area, (2) if they feel paresthesia and if so where do they feel it and how is the stimulation described, (3) how they would rate the ease of use of the stimulation, (4) the advantages and (5) the disadvantages per stimulation modality. A detailed overview of the crossover period is provided in Fig. During the final evaluation (S6) a decision is made by the patient regarding which stimulation modality is to be used for the subsequent 3 months at the end of these 5 periods. This decision is mainly based on pain reduction, but also on other CRPS-related symptoms and practical matters related to the stimulation. The patient continues with their stimulation of choice for another 3 months. A switch of stimulation within these 3 months is possible in certain cases.The five stimulation modalities are all programmed in such a way the maximum effect pain be obtained. Standard 40 Hz stimulation will be performed above threshold which generates paresthesia in the affected area and is in accordance with normal practice. Both 500 Hz and 1200 Hz will be above threshold stimulation and will also generate paresthesia. At the time this study protocol was postulated there were no other reports available on how best to program 500 and 1200 Hz SCS based on mechanisms of action. Thus, in absence of evidence stating the contrary, we decided to program 500 and 1200 Hz SCS like standard 40 Hz stimulation with the intention to induce paresthesia and thus being an above threshold stimulation. Placebo stimulation is performed with the IPG switched off and thus does not generate paresthesia. The rationale is to evaluate how big a part of the pain relief could be attributed to the placebo effect. Burst stimulation is performed with fixed stimulation parameters and the intensity of the stimulation will be sub-threshold and therefore is does not generate paresthesia. The fixed parameters of burst stimulation are: an overall frequency of 40 Hz per burst complex. Each burst complex delivers 5 spikes with a frequency of 500 Hz and a pulse width per spike of 1 ms and an inter-spike interval of 1 ms. The charge is balanced during the 15 ms pause between the burst complexes.The T2 assessment is performed when a patient has completed the 3-month period with the frequency of choice. This T2 evaluation enables us to compare all the primary and secondary outcomes parameters with the T1 assessment with standard SCS and the baseline T0 assessment prior to SCS therapy. The patient is actively asked whether they want to continue with the SCS program they have chosen, or want to switch to another one based on the crossover results.After completion of this trial the patient will continue with the chosen stimulation and a clinical follow-up is performed once a year by the physicians and nurses.Data obtained from this trial will provide better insight as to whether SCS, as it is currently applied, is the best available therapy modality, or whether stimulation with a higher frequency or with burst stimulation results in better pain relief. Another result might be that these new modalities of stimulation are equally preferred by the patients. Irrespective of the outcomes, this trial will provide new insights into the mechanisms of action involved in SCS treatment and, particularly, in patients with CRPS.For this trial, standard SCS was defined as stimulation with 40 Hz and corresponds with the normal stimulation setting used in our daily practice. The choice to select 500 Hz was based on studies reporting that blood flow and endogenous opioid release are at their maximum while applying SCS at this frequency , 59, 81.High-frequency SCS (HF-SCS) with 10,000 Hz is also available and multiple studies have shown its effect in pain patients and its ability to reduce pain over a longer period of time , 86. OurBurst stimulation is a new concept which requires a totally different programming algorithm in daily practice. The stimulation must be programmed to a sub-threshold current output level so that a patient will not experience paresthesia. This paresthesia free ‘side-effect’ can be used to incorporate a placebo element into the trial where paresthesia cannot be felt because the stimulation is switched off.The question remains if a 2 week test period per frequency along with a 2 day wash-out to counteract the possible carryover effects of the various frequencies are enough. In clinical practice a patient can conclude whether the SCS is beneficial to him/her within a two week period during trial SCS. We choose to maintain the 2 week per period analogy in the crossover period which should provide the patient with enough time to decide if one of the test frequencies is beneficial or not. Moreover, by increasing the crossover period to 3 weeks or even longer the possibility of patient withdrawal from the study increases in case one of the test stimulations does not provide (sufficient) pain relief. This is further supported by what clinicians hear from patients that the pain returns when the stimulation is switched off. Some experience an instantaneous increase in pain while others report that it takes a few minutes or a few hours before the pain has fully returned, but never longer than 24 h. On these arguments we decided on a wash-out period of 2 days between the various stimulation modalities to be tested –90.A potential pitfall in the design of the present trial that might influence the patient’s choice, is that the patients are preconditioned with standard stimulation for the first 3 months. On the other hand, if they do choose a SCS setting other than the standard one, it is a choice they make despite the odds being in favour of the standard stimulation.Bias and in particular attrition bias is a serious problem that could affect the results of the trial. In our trial attrition bias will be handled by describing all patients that have dropped out of the trial before its completion and the reasons for dropping out/trial exit will be documented and provided in a flowchart in a separate manuscript with the results of this trial. The flowchart will adhere to the requirements of the CONSORT statement for transparent reporting of trials. Furthermore, data will be analysed using linear mixed models. Hence we can use all of the data, i.e., if a score is missing, it has no effect on other scores from that same patient.With the results obtained from this study, that focuses solely on patients with CRPS, we aim to increase knowledge on the effects of SCS in this patient group. However, caution is advised when extrapolating these results to other neuropathic pain states because of the single-disease inclusion approach.Patient recruitment and inclusion started in August 2011 and the trial is currently ongoing. Completion of the first part of the study  is expected in early 2015. The completion of T2 and long-term data collection is expected towards the end of 2015.


Studies suggest that fluid motion in the extracellular space may be involved in the cellular mechanosensitivity at play in the bone tissue adaptation process. Previously, the authors developed a mesoscale predictive structural model of the femur using truss elements to represent trabecular bone, relying on a phenomenological strain-based bone adaptation algorithm. In order to introduce a response to bending and shear, the authors considered the use of beam elements, requiring a new formulation of the bone adaptation drivers. The primary goal of the study presented here was to isolate phenomenological drivers based on the results of a mechanistic approach to be used with a beam element representation of trabecular bone in mesoscale structural modelling. A single-beam model and a microscale poroelastic model of a single trabecula were developed. A mechanistic iterative adaptation algorithm was implemented based on fluid motion velocity through the bone matrix pores to predict the remodelled geometries of the poroelastic trabecula under 42 different loading scenarios. Regression analyses were used to correlate the changes in poroelastic trabecula thickness and orientation to the initial strain outputs of the beam model. Linear ( It has long been observed that bone adapts its shape and structure to its mechanical environment Wolff . The proStrains that are osteogenic at the tissue level . It wasp as its counterpart. If the changes in the medium are assumed to occur by reversible processes, the macroscopic condition of the medium described by the strain variables G the drained shear modulus related to Young’s modulus E and M a coefficient such as:K, q is the fluid flux, Bone can be considered as a biphasic or poroelastic material with fluid present within the porous solid matrix Cowin . PoroelaAbaqus 6.12 element CPE4P (Dassault Systemes The single trabecula was modelled as a rectangle (cylinder projected on the 2D plane) with length 1 mm and width 0.2 mm. It was meshed using four-nodded linear plane strain poroelastic elements with characteristic element edge length of 0.015 mm , with a time step of one second. The loading was applied, in step increments of 0.1 s, linearly from zero to the amplitude prescribed in the plan of analysis over half of the time step and then decreased linearly over the other half. This load rate was consistent with the literature (Pereira and Shefelbine The poroelastic simulations were conducted using the transient soil analysis option in For both the beam model and the poroelastic model, the bottom edge of the bottom plate was fixed. The loading was evenly applied to the nodes at the top edge of the top plate. The top plate was constrained to displace only in the direction of the load, to maintain a constant load direction on the trabecula and avoid deformation of the plate in ways that could impact the load profile on the trabecula. A schematic of both set-ups is displayed in Fig. F were selected in the range Five values of load amplitude mentclass2pt{minimIn this study, the mechanistic remodelling algorithm was based on the fluid motion theory. Hence, pore fluid velocity, directly linked to cell membrane shear stress and strain, was chosen as the driver for bone apposition or resorption. This driver is consistent with previous in silico work. For instance, Adachi et al.  used memA the cross-sectional area of a cylindrical trabecula with radius equal to half the width of the 2D trabecular model in this study. According to the ‘Mechanostat’ principle, such a load case should elicit minimal adaptation. The remodelling algorithm was run with varying fluid velocity targets and target range limits until ‘qualitatively minimal’ remodelling was obtained. The target values were thus set to Just as in the previous studies, a target fluid velocity range was chosen. Its limits can be interpreted as thresholds for cell mechanosensitivity. They were obtained through a trial-and-error calibration: A purely compressive force by Frost  and A thV at that point. The median was chosen instead of the mean to minimise potential errors arising from outliers and finite-element edge effects. The radius of the sphere of influence was taken as a third of the distance between two characteristic points. An updated horizontal component of the position p:Python scripts to extract information from an Abaqus output database and generate new Abaqus models, and MATLAB to compute the updated characteristic point positions.Remodelling happens on the surface of the bone elements Rucci . In thisThe poroelastic remodelling pipeline was tested on a scenario adapted from Adachi et al.  for compi et al. , pore flThe definition parameters of beams equivalent to the remodelled poroelastic trabeculae were estimated for all the loading scenarios tested. The position of the start and end nodes were taken as the middle points between the left and right extremities of the corresponding edge of the trabecula models. The inclination An apparent trabecular radius was estimated as half of the mean between the differences in horizontal position of the characteristic points of both splines. The remodelled radius was computed as the projection of the apparent radius over the direction perpendicular to the beam axis defined by the start and end nodes. The changes in the beam definition parameters between initial and equivalent adapted configurations (Figure Figures Figure Figures The results shown in Fig. For all the loading scenarios tested, including pure tension and pure compression at force amplitude The calibration of the target fluid velocities was arbitrarily assigned, based on achieving a match with the well-established strain targets proposed by Frost , and furAdaptation in tension (f between The trabecula orientations adapted consistently with the load inclination; however, they did not match them exactly. The offset can be visualised on Fig. The offset, and its increase with load amplitude are very likely due to the non-zero width of the target range, as a less precise alignment of The interpretation of the results of bone remodelling to a purely lateral load is unclear. It seems like a combination of the adaptation to a load with a small positive k of these linear relationships varies between For all other It should be noted that the adapted position of the centre of the trabecula was not computed. In a perfectly symmetrical set-up, it could be assumed that this point remains fixed, the trabecula ‘rotating’ around it. However, the set-up in this study only allows loading from above, and in reality, trabecular elements are likely not to be loaded symmetrically from both sides.At this stage of development, the relationships derived can be implemented in the authors’ phenomenological structural model (Phillips et al. Another limitation is that, to this point, no branching phenomenon has been implemented in the poroelastic model. It is, however, a potential mechanism of adaptation, already reported in in silico work (Kameo and Adachi To summarise, a single-beam model and a microscale poroelastic model of a single trabecula were developed. A mechanistic iterative adaptation algorithm was implemented based on fluid motion velocity through the bone matrix pores to predict the remodelled geometries of a single trabecula under 42 different axial loading scenarios. The remodelled geometries were used to derive two phenomenological relationships (