Jassim Hussam Hameed, Nedaei Hassan A, Banaee Nooshin, Geraily Ghazale, Kazemian Ali
Department of Medical Physics and Biomedical Engineering, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
Radiation Oncology Research Centre, Cancer Institute, Tehran University of Medical Sciences, Tehran, Iran.
J Biomed Phys Eng. 2025 Jun 1;15(3):221-230. doi: 10.31661/jbpe.v0i0.2212-1574. eCollection 2025 Jun.
Kilovoltage Cone Beam Computed Tomography (kVCBCT) is used for patient setup, monitoring the delivered dose, and adapting the treatment to changes in the patient's condition. Radiation therapy has recently shifted from image guidance to dose guidance, resulting in accurately calculating the daily dose, calculated by re-simulating CT-based treatment planning, to increase the precision of the actual treatment dosage. The use of kVCBCT instead of re-simulated CT can simplify the patient pathway and reduce potential therapeutic errors by eliminating the need for additional simulation.
The present study aimed to assess the dosimetric effects of anatomical changes on prostate tumors using Deformation Image Registration (DIR) and kVCBCT.
In this experimental study, eight patients with primary prostate cancer were treated with Volumetric Modulated Arc Therapy (VMAT), and kVCBCT images were obtained for each patient during the first treatment fraction. Both the planning CT (pCT) and kVCBCT images were imported into DIR software. The pCT was then deformed to the kVCBCT image and imported into a Treatment Planning System (TPS). A new contour was created on the deformed Computed Tomography (dCT) using Atlas-based Auto-segmentation (ABAS). Daily dCT plans were individually created based on the same planning principles using the new contours and also denoted dCTp1 through dCTp8. The outcomes of dose calculations were compared using Dose Volume Histograms (DVH), including mean Planning Target Volume (PTV) doses at the prescribed dose and dose volume limitations for the bladder and rectal wall.
The mean doses to the PTV in the eight dCT-based plans were the same as those in the pCT-based plans. However, the mean doses to organs at risk in the dCT plans were different from those in the pCT plans. The mean doses to the bladder were on average 4% lower than those in the pCT plans, while the mean doses to the rectum were on average 8% higher than those in the pCT plans.
The use of VMAT based on kilovoltage kVCBCT and Deformtion Image Registration (DIR) can lead to re-decreasing the dose to the bladder while increasing that to the rectum, with the same PTV dose coverage.
千伏级锥形束计算机断层扫描（kVCBCT）用于患者摆位、监测所给予的剂量以及根据患者病情变化调整治疗方案。放射治疗最近已从图像引导转向剂量引导，这使得通过重新模拟基于CT的治疗计划来准确计算每日剂量，以提高实际治疗剂量的精度。使用kVCBCT而非重新模拟的CT可简化患者流程，并通过消除额外模拟的需求来减少潜在的治疗误差。
本研究旨在使用形变图像配准（DIR）和kVCBCT评估解剖结构变化对前列腺肿瘤的剂量学影响。
在这项实验研究中，8例原发性前列腺癌患者接受容积调强弧形放疗（VMAT），并在首次治疗分次期间为每位患者获取kVCBCT图像。将计划CT（pCT）图像和kVCBCT图像都导入DIR软件。然后将pCT图像变形至kVCBCT图像，并导入治疗计划系统（TPS）。使用基于图谱的自动分割（ABAS）在变形后的计算机断层扫描（dCT）上创建新的轮廓。基于相同的计划原则，使用新轮廓分别创建每日dCT计划，并将其标记为dCTp1至dCTp8。使用剂量体积直方图（DVH）比较剂量计算结果，包括规定剂量下的平均计划靶体积（PTV）剂量以及膀胱和直肠壁的剂量体积限制。
八个基于dCT的计划中PTV的平均剂量与基于pCT的计划相同。然而，dCT计划中危及器官的平均剂量与pCT计划不同。膀胱的平均剂量比pCT计划平均低4%，而直肠的平均剂量比pCT计划平均高8%。
基于千伏级kVCBCT和形变图像配准（DIR）使用VMAT可在PTV剂量覆盖相同的情况下，导致膀胱剂量再次降低而直肠剂量增加。
