Department of Radiation Oncology, University of Florida, Gainesville, FL, USA; University of Florida Health Proton Therapy Institute, Jacksonville, FL, USA.
Department of Radiation Oncology, University of Florida, Gainesville, FL, USA; University of Florida Health Proton Therapy Institute, Jacksonville, FL, USA.
Phys Med. 2021 Jan;81:47-51. doi: 10.1016/j.ejmp.2020.11.033. Epub 2020 Dec 27.
To compare the planning target volume (PTV) margins needed for prostate patients who have used hydrogel spacer or rectal balloon during proton treatments.
Total of 190 prostate patients treated with proton therapy during 2017 were selected for this study. Of these patients, 96 had hydrogel spacer injection and 94 patients had only rectal balloons insertion. All patients had implanted gold markers inside the prostate for daily target alignment. Post-treatment radigraphs were obtained to evaluate prostate intrafraction motion. The systematic and random components of patient setup residual error and prostate intrafraction motion error were obtained. PTV margins were calculated using the van Herk formula for both patient groups.
For setup residual error, the mean values in the superior-inferior (SI) direction and the variances in the left-right (LR) direction were statistically different between the two groups. For intrafraction motion, there were significant differences of the mean values in the SI direction and of the variances in both LR and anterior-posterior (AP) directions. The population PTV margins for hydrogel spacer group were 2.6 mm, 3.3 mm, and 1.6 mm in LR, SI, AP directions, respectively. For the rectal balloon group, the PTV margins were 2.1 mm, 3.1 mm, and 2.0 mm in LR, SI, AP directions, respectively.
Statistically significant differences were observed in the patient setup and prostate intrafraction motion errors of the two patient groups. However, under the current protocol of bladder preparation and daily marker-based x-ray image-guidance, population PTV margins were comparable between the two patient groups.
比较使用水凝胶 spacer 或直肠气囊进行质子治疗的前列腺患者所需的计划靶区（PTV）边界。
本研究共选取了 190 名在 2017 年接受质子治疗的前列腺患者。其中 96 名患者接受了水凝胶 spacer 注射，94 名患者仅接受了直肠气囊插入。所有患者的前列腺内均植入了金标记物以进行日常靶区对准。在治疗后获得放射图以评估前列腺内分次运动。获得患者体位残余误差和前列腺内分次运动误差的系统和随机分量。使用 van Herk 公式为两组患者计算 PTV 边界。
对于体位残余误差，两组在上下（SI）方向的平均值和左右（LR）方向的方差存在统计学差异。对于分次运动，SI 方向的平均值和 LR 和前后（AP）方向的方差存在显著差异。水凝胶 spacer 组的总体 PTV 边界在 LR、SI、AP 方向上分别为 2.6、3.3、1.6mm。直肠气囊组的 PTV 边界在 LR、SI、AP 方向上分别为 2.1、3.1、2.0mm。
两组患者在体位和前列腺内分次运动误差方面存在统计学显著差异。然而，在当前的膀胱准备和每日标记 X 射线图像引导方案下，两组患者的总体 PTV 边界相当。
