Gurjar Om Prakash, Arya Ramesh, Goyal Harsh
Government Cancer Hospital, Mahatma Gandhi Memorial Medical College, Indore, Madhya Pradesh, India.
Department of Radiotherapy, Maharaja Bhim SIngh Medical College and Hospital, Kota, Rajasthan, India.
Prostate Int. 2020 Jun;8(2):91-97. doi: 10.1016/j.prnil.2019.12.003. Epub 2020 Feb 27.
To study the impact of bladder and rectum volume changes on prostate positioning and the dosimetric parameters.
Prostate is a moving organ, and its position is also affected by bladder and rectum volumes. Image-guided radiotherapy (IGRT) is being practiced widely for the treatment of prostate carcinoma (Ca). So, it is important to accurately study the effect of bladder and rectum volume changes in treatment.
Thirty patients with Ca prostate were included in this study, and all were treated with 50 Gray (Gy) in 25 fractions for the first phase of treatment. A total of 750 cone-beam computed tomography (CBCT) sessions were performed. Prostate position w.r.t. its day one position was noted, and the bladder and rectum volumes were compared with their volumes on day one. Also, repeat CT was done for five patients after 10 fractions. The initial plan was imported as it was on the repeat CT images, and a hybrid plan was prepared by putting the plan isocenter at the relative anatomical reference point in repeat CT images as it was in primary CT images. The multileaf collimators (MLC) fluence was put as it is, and the dose was calculated using the monitoring units (MU), which were in the initial plan. Doses to bladder, rectum, and the target were analyzed.
The mean prostate motion in lateral and anterior-posterior direction was found to be 0.71 (±0.69) centimeter cm) and 0.77 (±0.57) cm, respectively. The mean change in bladder and rectum volumes as compared to that in day one CT images was found to be 110.51 (±84.25) cubic centimeters (cc) and 10.89 (±10.17) cc, respectively. No significant variation was observed in the doses to bladder, rectum, and the target volume in a hybrid plan, as compared to that in actual initial plan.
Bladder and rectum volume affects the position of prostate, rather the dosimetric parameters, and therefore, it can be concluded that daily CBCT should be done for accurate IGRT delivery to the prostate cancer.
研究膀胱和直肠体积变化对前列腺位置及剂量学参数的影响。
前列腺是一个活动器官，其位置也受膀胱和直肠体积的影响。图像引导放射治疗（IGRT）在前列腺癌（Ca）治疗中被广泛应用。因此，准确研究膀胱和直肠体积变化在治疗中的作用很重要。
本研究纳入30例前列腺癌患者，所有患者在治疗第一阶段均接受25次分割、每次50格雷（Gy）的治疗。共进行了750次锥形束计算机断层扫描（CBCT）。记录前列腺相对于其第一天位置的位置，并将膀胱和直肠体积与其第一天的体积进行比较。另外，对5例患者在10次分割后进行了重复CT扫描。将初始计划按原样导入重复CT图像，通过将计划等中心置于重复CT图像中相对于原始CT图像的相对解剖参考点来制备混合计划。多叶准直器（MLC）注量保持不变，并使用初始计划中的监测单位（MU）计算剂量。分析膀胱、直肠和靶区的剂量。
发现前列腺在左右方向和前后方向的平均移动分别为0.71（±0.69）厘米（cm）和0.77（±0.57）厘米。与第一天的CT图像相比，膀胱和直肠体积的平均变化分别为110.51（±84.25）立方厘米（cc）和10.89（±10.17）cc。与实际初始计划相比，混合计划中膀胱、直肠和靶区体积的剂量无显著差异。
膀胱和直肠体积影响前列腺的位置，而非剂量学参数，因此，可以得出结论，为了将IGRT准确地应用于前列腺癌，应每日进行CBCT扫描。
