Department of Radiation Oncology, University of Florida Proton Therapy Institute, Jacksonville, Florida 32206, USA.
Med Phys. 2011 May;38(5):2450-4. doi: 10.1118/1.3578602.
To evaluate both the Calypso Systems' (Calypso Medical Technologies, Inc., Seattle, WA) localization accuracy in the presence of wireless metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters of dose verification system (DVS, Sicel Technologies, Inc., Morrisville, NC) and the dosimeters' reading accuracy in the presence of wireless electromagnetic transponders inside a phantom.
A custom-made, solid-water phantom was fabricated with space for transponders and dosimeters. Two inserts were machined with positioning grooves precisely matching the dimensions of the transponders and dosimeters and were arranged in orthogonal and parallel orientations, respectively. To test the transponder localization accuracy with/without presence of dosimeters (hypothesis 1), multivariate analyses were performed on transponder-derived localization data with and without dosimeters at each preset distance to detect statistically significant localization differences between the control and test sets. To test dosimeter dose-reading accuracy with/without presence of transponders (hypothesis 2), an approach of alternating the transponder presence in seven identical fraction dose (100 cGy) deliveries and measurements was implemented. Two-way analysis of variance was performed to examine statistically significant dose-reading differences between the two groups and the different fractions. A relative-dose analysis method was also used to evaluate transponder impact on dose-reading accuracy after dose-fading effect was removed by a second-order polynomial fit.
Multivariate analysis indicated that hypothesis 1 was false; there was a statistically significant difference between the localization data from the control and test sets. However, the upper and lower bounds of the 95% confidence intervals of the localized positional differences between the control and test sets were less than 0.1 mm, which was significantly smaller than the minimum clinical localization resolution of 0.5 mm. For hypothesis 2, analysis of variance indicated that there was no statistically significant difference between the dosimeter readings with and without the presence of transponders. Both orthogonal and parallel configurations had difference of polynomial-fit dose to measured dose values within 1.75%.
The phantom study indicated that the Calypso System's localization accuracy was not affected clinically due to the presence of DVS wireless MOSFET dosimeters and the dosimeter-measured doses were not affected by the presence of transponders. Thus, the same patients could be implanted with both transponders and dosimeters to benefit from improved accuracy of radiotherapy treatments offered by conjunctional use of the two systems.
评估 Calypso 系统（Calypso Medical Technologies，Inc.，西雅图，WA）在无线金属氧化物半导体场效应晶体管（MOSFET）剂量验证系统（DVS，Sicel Technologies，Inc.，莫里斯维尔，NC）的无线剂量计存在的情况下的定位准确性，以及剂量计在体模内存在无线电磁转发器的情况下的读数准确性。
制作了一个定制的、实心水的体模，用于容纳转发器和剂量计。两个插入物用精确匹配转发器和剂量计尺寸的定位槽加工而成，分别以正交和平行的方向布置。为了测试转发器定位准确性在有无剂量计存在的情况下（假设 1），在每个预设距离处，对有和没有剂量计的转发器衍生的定位数据进行多元分析，以检测控制组和测试组之间的统计学上显著的定位差异。为了测试剂量计在有无转发器存在的情况下的剂量读数准确性（假设 2），实施了一种在七个相同分次剂量（100cGy）输送和测量中交替存在转发器的方法。采用双向方差分析来检查两组和不同分次之间的统计学上显著的剂量读数差异。还使用相对剂量分析方法来评估在通过二次多项式拟合去除剂量衰减效应后，转发器对剂量读数准确性的影响。
多元分析表明假设 1 是错误的；控制组和测试组的定位数据之间存在统计学上的显著差异。然而，控制组和测试组之间的定位差异的 95%置信区间的上下限小于 0.1 毫米，这明显小于最小的临床定位分辨率 0.5 毫米。对于假设 2，方差分析表明，有无转发器存在时，剂量计读数之间没有统计学上的显著差异。正交和平行配置的多项式拟合剂量与测量剂量值的差异均在 1.75%以内。
这项体模研究表明，由于 DVS 无线 MOSFET 剂量计的存在，Calypso 系统的定位准确性不会受到临床影响，并且剂量计测量的剂量不受转发器存在的影响。因此，同一患者可以同时植入转发器和剂量计，从两个系统联合使用提供的放疗治疗准确性提高中获益。
