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Radiation Oncology

, 9:43

Radiation Physics


BackgroundTo determine the effect of different imaging options and the most efficient imaging strategy for treatment planning of patients with hip prostheses.

MethodsThe planning kilovoltage CT kVCT and daily megavoltage CT MVCT studies for three prostate cancer patients with bilateral hip prostheses were used for creating hybrid kVCT-MVCT image sets. Treatment plans were created for kVCT images alone, hybrid kVCT-MVCT images, and MVCT images alone using the same dose prescription and planning parameters. The resulting dose volume histograms were compared. The orthopedic metal artifact reduction O-MAR reconstruction tool for kVCT images and different MVCT options were investigated with a water tank fit with double hip prostheses. Treatment plans were created for all imaging options and calculated dose was compared with the one measured by a pin-point ion chamber.

ResultsOn average for three patients, the D35% for the bladder was 8% higher in plans based on MVCT images and 7% higher in plans based on hybrid images, compared to the plans based on kVCT images alone. Likewise, the D35% for the rectum was 3% higher than the kVCT based plan for both hybrid and MVCT plans. The average difference in planned D99% in the PTV compared to kVCT plans was 0.9% and 0.1% for MVCT and hybrid plans, respectively. For the water tank with hip prostheses phantom, the kVCT plan with O-MAR correction applied showed better agreement between the measured and calculated dose than the original image set, with a difference of -1.9% compared to 3.3%. The measured doses for the MVCT plans were lower than the calculated dose due to image size limitations. The best agreement was for the kVCT-MVCT hybrid plans with the difference between calculated and measured dose around 1%.

ConclusionMVCT image provides better visualization of patient anatomy and hybrid kVCT-MVCT study enables more accurate calculations using updated MVCT relative electron density calibration.

KeywordsTomotherapy MVCT Prostheses Electronic supplementary materialThe online version of this article doi:10.1186-1748-717X-9-43 contains supplementary material, which is available to authorized users.

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Author: David Chapman - Shaun Smith - Rob Barnett - Glenn Bauman - Slav Yartsev

Source: https://link.springer.com/

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