Dose calculation accuracy of different image value to density tables for cone-beam CT planning in head & neck and pelvic localizations.
PURPOSE
We aimed to identify the most accurate combination of phantom and protocol for image value to density table (IVDT) on volume-modulated arc therapy (VMAT) dose calculation based on kV-Cone-beam CT imaging, for head and neck (H&N) and pelvic localizations.


METHODS
Three phantoms (Catphan(®)600, CIRS(®)062M (inner phantom for head and outer phantom for body), and TomoTherapy(®) "Cheese" phantom) were used to create IVDT curves of CBCT systems with two different CBCT protocols (Standard-dose Head and Standard Pelvis). Hounsfield Unit (HU) time stability and repeatability for a single On-Board-Imager (OBI) and compatibility of two distinct devices were assessed with Catphan(®)600. Images from the anthropomorphic phantom CIRS ATOM(®) for both CT and CBCT modalities were used for VMAT dose calculation from different IVDT curves. Dosimetric indices from CT and CBCT imaging were compared.


RESULTS
IVDT curves from CBCT images were highly different depending on phantom used (up to 1000 HU for high densities) and protocol applied (up to 200 HU for high densities). HU time stability was verified over seven weeks. A maximum difference of 3% on the dose calculation indices studied was found between CT and CBCT VMAT dose calculation across the two localizations using appropriate IVDT curves. One IVDT curve per localization can be established with a bi-monthly verification of IVDT-CBCT.


CONCLUSIONS
The IVDT-CBCTCIRS-Head phantom with the Standard-dose Head protocol was the most accurate combination for dose calculation on H&N CBCT images. For pelvic localizations, the IVDT-CBCTCheese established with the Standard Pelvis protocol provided the best accuracy.
['Barateau|Anaïs|A|', 'Garlopeau|Christopher|C|', 'Cugny|Audrey|A|', 'De Figueiredo|Bénédicte Henriques|BH|', 'Dupin|Charles|C|', 'Caron|Jérôme|J|', 'Antoine|Mikaël|M|']
D000328:Adult D054893:Cone-Beam Computed Tomography D006257:Head D006801:Humans D008297:Male D009333:Neck D010388:Pelvis D019047:Phantoms, Imaging D011829:Radiation Dosage D011879:Radiotherapy Dosage D011880:Radiotherapy Planning, Computer-Assisted D050397:Radiotherapy, Intensity-Modulated D015203:Reproducibility of Results D013997:Time Factors
IVDT curve Hounsfield units kV-CBCT