Koprivec Dylan, Rosenfeld Anatoly, Cutajar Dean, Petasecca Marco, Howie Andrew, Bucci Joseph, Poder Joel
Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia.
Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia.
Brachytherapy. 2022 Nov-Dec;21(6):943-955. doi: 10.1016/j.brachy.2022.07.011. Epub 2022 Sep 6.
The purpose of this study was to determine the feasibility of online adaptive transrectal ultrasound (TRUS)-based high-dose-rate prostate brachytherapy (HDRPBT) through retrospective simulation of source positioning and catheter swap errors on patient treatment plans.
Source positioning errors (catheter shifts in 1 mm increments in the cranial/caudal, anterior/posterior, and medial/lateral directions up to ±6 mm) and catheter swap errors (between the most and least heavily weighted) were introduced retrospectively into DICOM treatment plans of 20 patients that previously received TRUS HDRPBT. Dose volume histogram (DVH) indices were monitored as errors were introduced sequentially into individual catheters, simulating potential errors throughout treatment. Whenever DVH indices were outside institution thresholds: prostate V100% <95%, urethra D0.1cc >118% and rectum Dmax >80%, the plan was adapted using remaining catheters (i.e., simulating previous catheters as previously delivered). The final DVH indices were recorded.
Prostate coverage (V100% >95%) could be maintained for source position errors up to 6 mm through online plan adaptation. The source position error at which the urethra D0.1cc and rectum Dmax was able to return to clinically acceptable levels using online adaptation varied between 6 mm to 1 mm, depending on the direction of the source position error and patient anatomy. After introduction of catheter swap errors to patient plans, prostate V100% was recoverable using online adaptation to near original plan characteristics. Urethra D0.1cc and rectum Dmax showed less recoverability.
Online adaptive HDRPBT maintains the prostate V100% to clinically acceptable values for majority of directional shifts. However, the current online adaptive method may not correct for source position errors near organs at risk.
本研究的目的是通过对患者治疗计划中源定位和导管交换误差进行回顾性模拟，来确定基于在线自适应经直肠超声（TRUS）的高剂量率前列腺近距离放射治疗（HDRPBT）的可行性。
将源定位误差（导管在头侧/尾侧、前侧/后侧以及内侧/外侧方向上以1mm增量进行移位，最大可达±6mm）和导管交换误差（最重加权和最轻加权导管之间的交换）回顾性地引入到20例先前接受过TRUS HDRPBT的患者的DICOM治疗计划中。在将误差依次引入各个导管时，监测剂量体积直方图（DVH）指标，模拟整个治疗过程中的潜在误差。每当DVH指标超出机构阈值时：前列腺V100%<95%、尿道D0.1cc>118%以及直肠Dmax>80%，则使用剩余导管对计划进行调整（即模拟先前已输送的导管）。记录最终的DVH指标。
通过在线计划调整，对于高达6mm的源位置误差，前列腺覆盖率（V100%>95%）能够得以维持。根据源位置误差的方向和患者解剖结构，使用在线调整使尿道D0.1cc和直肠Dmax能够恢复到临床可接受水平的源位置误差在6mm至1mm之间变化。在将导管交换误差引入患者计划后，使用在线调整可使前列腺V100%恢复到接近原始计划特征。尿道D0.1cc和直肠Dmax的恢复性较差。
在线自适应HDRPBT可将前列腺V100%维持在大多数方向移位的临床可接受值。然而，当前的在线自适应方法可能无法校正靠近危及器官处的源位置误差。
