Smith Ryan L, Hanlon Max, Panettieri Vanessa, Millar Jeremy L, Matheson Bronwyn, Haworth Annette, Franich Rick D
Alfred Health Radiation Oncology, Alfred Health, Melbourne, VIC, Australia; School of Science, RMIT University, Melbourne, VIC, Australia.
School of Science, RMIT University, Melbourne, VIC, Australia.
Brachytherapy. 2018 Jan-Feb;17(1):111-121. doi: 10.1016/j.brachy.2017.08.004. Epub 2017 Sep 22.
High-dose-rate (HDR) prostate brachytherapy treatment is usually delivered in one or a few large dose fractions. Poor execution of a planned treatment could have significant clinical impact, as high doses are delivered in seconds, and mistakes in an individual fraction cannot be easily rectified. Given that most potential errors in HDR brachytherapy ultimately lead to a geographical miss, a more direct approach to verification of correct treatment delivery is to directly monitor the position of the source throughout the treatment. In this work, we report on the clinical implementation of our treatment verification system that uniquely combines the 2D source-tracking capability with 2D pretreatment imaging, using a single flat panel detector (FPD).
The clinical brachytherapy treatment couch was modified to allow integration of the FPD into the couch. This enabled the patient to be set up in the brachytherapy bunker in a position that closely matched that at treatment planning imaging. An anteroposterior image was acquired of the patient immediately before treatment delivery and was assessed by the Radiation Oncologist online, to reestablish the positions of the catheters relative to the prostate. Assessment of catheter positions was performed in the left-right and superior-inferior directions along the entire catheter length and throughout the treatment volume. Source tracking was then performed during treatment delivery, and the measured position of the source dwells were directly compared to the treatment plan for verification.
The treatment verification system was integrated into the clinical environment without significant change to workflow. Two patient cases are presented in this work to provide clinical examples of this system, which is now in routine use for all patient treatments in our clinic. The catheter positions were visualized relative to the prostate, immediately before treatment delivery. For one of the patient cases presented in this work, they agreed with the treatment plan on average by 1.5 mm and were identifiable as a predominantly inferior shift. The source tracking was performed during treatment delivery, and for the same case, the mean deviation from the planned dwell positions was 1.9 mm (max = 4.9 mm) for 280 positions across all catheters.
We have implemented our noninvasive treatment verification system based on an FPD in the clinical environment. The device is integrated into a patient treatment couch, and the process is now included in the routine clinical treatment procedure with minor impact on workflow. The system which combines both 2D pretreatment imaging and HDR 2D source tracking provides a range of information that can be used for comprehensive treatment verification. The system has the potential to meaningfully improve safety standards by allowing widespread adoption of routine treatment verification in HDR brachytherapy.
高剂量率（HDR）前列腺近距离放射治疗通常采用单次或少数几次大剂量分割。由于高剂量在数秒内即可完成照射，且单个分割中的错误难以轻易纠正，因此计划治疗执行不佳可能会产生重大临床影响。鉴于HDR近距离放射治疗中的大多数潜在误差最终都会导致剂量分布偏差，一种更直接的验证正确治疗实施的方法是在整个治疗过程中直接监测放射源的位置。在本研究中，我们报告了我们的治疗验证系统的临床应用情况，该系统使用单个平板探测器（FPD），独特地将二维放射源跟踪功能与二维治疗前成像相结合。
对临床近距离放射治疗床进行了改装，以便将FPD集成到治疗床中。这使得患者能够在近距离放射治疗掩体中以与治疗计划成像时紧密匹配的位置进行摆位。在治疗开始前立即采集患者的前后位图像，并由放射肿瘤学家在线评估，以重新确定导管相对于前列腺的位置。在整个导管长度和整个治疗体积内，沿左右和上下方向对导管位置进行评估。然后在治疗过程中进行放射源跟踪，并将测量的放射源驻留位置直接与治疗计划进行比较以进行验证。
治疗验证系统已集成到临床环境中，且工作流程没有显著变化。本研究展示了两个患者案例，以提供该系统的临床实例，该系统现已在我们诊所的所有患者治疗中常规使用。在治疗开始前，可以看到导管相对于前列腺的位置。对于本研究中展示的一个患者案例，导管位置与治疗计划的平均偏差为1.5毫米，且可识别为主要是向下偏移。在治疗过程中进行了放射源跟踪，对于同一案例，所有导管上280个位置与计划驻留位置的平均偏差为1.9毫米（最大值 = 4.9毫米）。
我们已在临床环境中基于FPD实施了我们的无创治疗验证系统。该设备集成到患者治疗床上，并且该过程现在已包含在常规临床治疗程序中，对工作流程的影响较小。结合二维治疗前成像和HDR二维放射源跟踪的系统提供了一系列可用于全面治疗验证的信息。该系统有可能通过在HDR近距离放射治疗中广泛采用常规治疗验证来切实提高安全标准。
