Medical Physics Program, University of Massachusetts Lowell, Lowell, MA, 01852, USA.
Department of Radiation Oncology, Rhode Island Hospital, The Alpert Medical School of Brown University, Providence, RI, 02903, USA.
Med Phys. 2017 Jul;44(7):3861-3865. doi: 10.1002/mp.12289. Epub 2017 May 24.
Real-time dynamic control of the linear accelerator, couch, and imaging parameters during radiation delivery was investigated as a novel technique for acquiring tissue maximum ratio (TMR) data.
TrueBeam Developer Mode (Varian Medical Systems, Palo Alto, CA, USA) was used to control the linear accelerator using the Extensible Markup Language (XML). A single XML file was used to dynamically manipulate the machine, couch, and imaging parameters during radiation delivery. A TG-51 compliant 1D water tank was placed on the treatment couch, and used to position a detector at isocenter at a depth of 24.5 cm. A depth scan was performed towards the water surface. Via XML control, the treatment couch vertical position was simultaneously lowered at the same rate, maintaining the detector position at isocenter, allowing for the collection of TMR data. To ensure the detector remained at isocenter during the delivery, the in-room camera was used to monitor the detector. Continuous kV fluoroscopic images during 10 test runs further confirmed this result. TMR data at multiple Source to Detector Distances (SDD) and scan speeds were acquired to investigate their impact on the TMR data. Percentage depth dose (PDD) scans (for conversion to TMR) along with traditional discrete TMR data were acquired as a standard for comparison.
More than 99.8% of the measured points had a gamma value (1%/1 mm) < 1 when compared with discrete or PDD converted TMR data. Fluoroscopic images showed that the concurrent couch and tank movements resulted in SDD errors < 1 mm. TMRs acquired at SDDs of 99, 100, and 101 cm showed differences less than 0.004.
TrueBeam Developer Mode was used to collect continuous TMR data with the same accuracy as traditionally collected discrete data, but yielded higher sampled resolution and reduced acquisition time. This novel method does not require the modification of any equipment and does not use a 3D tank or reservoir.
研究在放射治疗过程中实时动态控制直线加速器、治疗床和成像参数，作为获取组织最大比（TMR）数据的一种新方法。
使用可扩展标记语言（XML）通过 TrueBeam 开发者模式（美国加利福尼亚州帕洛阿尔托的瓦里安医疗系统公司）控制直线加速器。使用单个 XML 文件在放射治疗过程中动态地操纵机器、治疗床和成像参数。将一个符合 TG-51 标准的一维水水箱放在治疗床上，并用它将探测器定位在深度为 24.5 厘米的等中心。进行了向水面的深度扫描。通过 XML 控制，治疗床垂直位置以相同的速度同时降低，保持探测器在等中心的位置，从而可以收集 TMR 数据。为了确保在治疗过程中探测器保持在等中心位置，使用室内摄像机监测探测器。在 10 次测试运行中连续进行的千伏荧光透视图像进一步证实了这一结果。采集了多个源到探测器距离（SDD）和扫描速度的 TMR 数据，以研究它们对 TMR 数据的影响。同时还采集了百分深度剂量（PDD）扫描（用于转换为 TMR）和传统离散 TMR 数据作为标准进行比较。
与离散或 PDD 转换的 TMR 数据相比，超过 99.8%的测量点的伽马值（1%/1 毫米）<1。荧光透视图像显示，同时进行的治疗床和水箱运动导致 SDD 误差<1 毫米。在 SDD 为 99、100 和 101 厘米处采集的 TMR 差异小于 0.004。
使用 TrueBeam 开发者模式采集连续 TMR 数据的准确性与传统采集的离散数据相同，但具有更高的采样分辨率和更短的采集时间。这种新方法不需要修改任何设备，也不需要使用 3D 水箱或储液器。
