TITLE:
Feasibility Study of Adaptive Prostate Cancer Radiotherapy Using Daily kVCT Images on a Ring-Gantry Radiotherapy Machine
AUTHORS:
Chunhui Han, Oluwaseyi M. Oderinde, Arjun Maniyedath, Terence M. Williams, An Liu
KEYWORDS:
Adaptive Radiotherapy, Image-Guided Radiotherapy, Prostate Cancer, kVCT
JOURNAL NAME:
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology,
Vol.15 No.4,
October
15,
2026
ABSTRACT: Background: For prostate cancer patients undergoing external beam radiotherapy, dose delivery accuracy of radiotherapy is limited due to daily anatomical variations. One alternative, adaptive radiotherapy (ART) based on daily imaging, has been proposed to minimize changes in treatment delivery. Methods: We aimed to evaluate kilo-voltage computed tomography (kVCT) image quality from a ring-gantry medical linac (X1 machine) with an integrated fan-beam CT imaging system and assess whether daily kVCT images can be used to plan ART in prostate cancer radiotherapy. We compared the image quality of all kVCT scanning protocols on the X1 and a clinical CT simulator on an image quality phantom. To calculate volumetric modulated arc therapy plan doses, we used CT images for an anthropomorphic phantom from the CT simulator and X1 linac. We retrospectively selected treatment plans and daily imaging data for ten prostate cancer patients who received X1 machine treatments. Using daily kVCT images, we delineated normal organs and target volume contours and created adaptive plans with the original treatment optimization parameters. Results: Excluding the air insert, average CT numbers for different density inserts on the image quality phantom varied from −3.5 to 5.7 HU between CT simulator and X1 kVCT images. kVCT images had less than 0.3% variation in mean dose compared to phantom CT simulation images. Daily bladder and rectum volume variation ranged from −352 to +212 cc and from −138.6 to 81.8 cc, respectively. Relative to the original treatment plans, kVCT image-based plan mean doses for the primary PTV, bladder, rectum, and penile bulb were 100.9% ± 2.7%, 97.8% ± 9.2%, 98.1% ± 9.2%, and 96.1% ± 24.7%, respectively. Conclusions: The kVCT images from the X1 machine demonstrated adequate CT image quality for treatment planning. Most optimized adaptive treatment plans had comparable target coverages and acceptable normal organ dose variations, indicating potential clinical benefits with adaptive treatment planning in the presence of large daily anatomical variations.