Influence of nuclear interactions in body tissues on XXXX dose in @entity505 -ion radiotherapy.

@entity505 @entity1 @entity15929 @entity5
PURPOSE: In @entity505 -ion radiotherapy treatment planning, the @entity15929 ( @entity15929 ) measured in water is applied to the @entity1 dose calculation with density scaling using the stopping power ratio. Since body tissues are chemically different from water, this dose calculation can be subject to errors, particularly due to differences in inelastic nuclear interactions. In recent studies, the authors proposed and validated a @entity15929 correction method for these errors. In the present study, the authors used this correction method to assess the influence of these nuclear interactions in body tissues on @entity5 dose in various clinical cases. METHODS: Using 10-20 cases each of prostate, head and neck (HN), bone and soft tissue (BS), lung, liver, pancreas, and uterine @entity5 , the authors first used treatment plans for @entity505 -ion radiotherapy without nuclear interaction correction to derive uncorrected dose distributions. The authors then compared these distributions with recalculated distributions using the nuclear interaction correction (corrected dose distributions). RESULTS: Median (25%/75% quartiles) differences between the target mean uncorrected doses and corrected doses were 0.2% (0.1%/0.2%), 0.0% (0.0%/0.0%), -0.3% (-0.4%/-0.2%), -0.1% (-0.2%/-0.1%), -0.1% (-0.2%/0.0%), -0.4% (-0.5%/-0.1%), and -0.3% (-0.4%/0.0%) for the prostate, HN, BS, lung, liver, pancreas, and uterine cases, respectively. The largest difference of -1.6% in target mean and -2.5% at maximum were observed in a uterine case. CONCLUSIONS: For most clinical cases, dose calculation errors due to the water nonequivalence of the tissues in nuclear interactions would be marginal compared to intrinsic uncertainties in treatment planning, @entity1 setup, beam delivery, and clinical response. In some extreme cases, however, these errors can be substantial. Accordingly, this correction method should be routinely applied to treatment planning in clinical practice.
