School of Physics, The University of Sydney, New South Wales 2006, Australia.
Med Phys. 2010 May;37(5):2247-55. doi: 10.1118/1.3397446.
In pelvic brachytherapy treatments, the rectum is an organ at risk. The authors have developed an array of scintillation dosimeters suitable for in vivo use that enables quality assurance of the treatment delivery and provides an alert to potential radiation accidents. Ultimately, this will provide evidence to direct treatment planning and dose escalation and correlate dose with the rectal response.
An array of 16 scintillation dosimeters in an insertable applicator has been developed. The dosimeters were calibrated simultaneously in a custom designed circular jig before use. Each dosimeter is optically interfaced to a set of pixels on a CCD camera located outside the treatment bunker. A customized software converts pixel values into dose rate and accumulates dose for presentation during treatment delivery. The performance of the array is tested by simulating brachytherapy treatments in a water phantom. The treatment plans were designed to deliver a known dose distribution on the surface of the rectal applicator, assumed to represent the dose to the rectal wall.
The measured doses were compared to those predicted by the treatment plan and found to be in agreement to within the uncertainty in measurement, usually within 3%. The array was also used to track the progression of the source as it moved along the catheter. The measured position was found to agree with the position reported by the afterloader to within the measurement uncertainty, usually within 2 mm.
This array is capable of measuring the actual dose received by each region of the rectal wall during brachytherapy treatments. It will provide real time monitoring of treatment delivery and raise an alert to a potential radiation accident. Real time dose mapping in the clinical environment will give the clinician additional confidence to carry out dose escalation to the tumor volume while avoiding rectal side effects.
在盆腔近距离放射治疗中，直肠是一个危险器官。作者开发了一系列适用于体内使用的闪烁剂量计，可用于治疗交付的质量保证，并提供潜在辐射事故的警报。最终，这将提供证据来指导治疗计划和剂量升级，并将剂量与直肠反应相关联。
在可插入的施源器中开发了一个 16 个闪烁剂量计的阵列。在使用前，在定制设计的圆形夹具中同时校准这些剂量计。每个剂量计都与位于治疗掩体外部的 CCD 相机上的一组像素光学连接。定制软件将像素值转换为剂量率，并在治疗输送过程中累积剂量以供显示。通过在水模体中模拟近距离放射治疗来测试阵列的性能。治疗计划旨在在直肠施源器表面上提供已知的剂量分布，假定该剂量分布代表直肠壁的剂量。
测量的剂量与治疗计划预测的剂量进行了比较，发现测量结果在测量不确定性范围内（通常在 3%以内）与预测值一致。该阵列还用于跟踪源在导管中移动时的位置变化。发现测量位置与后装机报告的位置在测量不确定性范围内一致，通常在 2 毫米以内。
该阵列能够测量近距离放射治疗过程中直肠壁每个区域实际接收到的剂量。它将提供治疗交付的实时监测，并对潜在的辐射事故发出警报。在临床环境中进行实时剂量映射将为临床医生提供额外的信心，以便在避免直肠副作用的同时对肿瘤体积进行剂量升级。
