Cantley Justin L, Cheng Chee-Wai, Jesseph Fredrick B, Podder Tarun K, Colussi Valdir C, Traughber Bryan J, Ponsky Lee E, Ellis Rodney J
University Hospitals.
J Appl Clin Med Phys. 2016 Nov 8;17(6):305-311. doi: 10.1120/jacmp.v17i6.6508.
A novel FDA approved in vivo dosimetry device system using plastic scintillating detectors placed in an endorectal balloon to provide real-time in vivo dosimetry for prostatic rectal interface was tested for use with stereotactic body radiotherapy (SBRT). The system was used for the first time ever to measure dose during linear accelerator based SBRT. A single patient was treated with a total dose of 36.25 Gy given in 5 fractions. Delivered dose was measured for each treatment with the detectors placed against the anterior rectal wall near the prostate rectal interface. Measured doses showed varying degrees of agreement with computed/ planned doses, with average combined dose found to be within 6% of the expected dose. The variance between measurements is most likely due to uncertainty of the detector location, as well as variation in the placement of a new balloon prior to each fraction. Distance to agreement for the detectors was generally found to be within a few millimeters, which also suggested that the differences in measured and calculated doses were due to positional uncertainty of the detectors during the SBRT, which had sharp dose falloff near the penumbra along the rectal wall. Overall, the use of a real time in vivo dosimeter provided a level of safety and improved confidence in treatment delivery. We are evaluating the device further in an IRB-approved prospective partial prostate SBRT trial, and believe further clinical investigations are warranted.
一种新型的、经美国食品药品监督管理局（FDA）批准的体内剂量测定设备系统，该系统使用置于直肠内气囊中的塑料闪烁探测器，为前列腺直肠界面提供实时体内剂量测定，现对其用于立体定向体部放射治疗（SBRT）进行测试。该系统有史以来首次用于在基于直线加速器的SBRT过程中测量剂量。一名患者接受了总量为36.25 Gy、分5次给予的治疗。每次治疗时，将探测器放置在靠近前列腺直肠界面的直肠前壁处测量所输送的剂量。测量剂量与计算/计划剂量显示出不同程度的一致性，发现平均总剂量在预期剂量的6%以内。测量值之间的差异很可能是由于探测器位置的不确定性，以及每次分次治疗前新气囊放置的变化。通常发现探测器达到一致的距离在几毫米以内，这也表明测量剂量与计算剂量的差异是由于SBRT期间探测器的位置不确定性，在直肠壁半影附近剂量急剧下降。总体而言，使用实时体内剂量计提供了一定程度的安全性，并提高了对治疗实施的信心。我们正在一项经机构审查委员会（IRB）批准的前瞻性部分前列腺SBRT试验中进一步评估该设备，并认为有必要进行进一步的临床研究。
