Therriault-Proulx F, Beaulieu L, Archambault L, Beddar S
University of Texas MD Anderson Cancer Center, Houston, TX.
Departement de Physique, de Genie Physique et d'Optique, Universite Laval, Quebec, QC.
Med Phys. 2012 Jun;39(6Part28):3967. doi: 10.1118/1.4736190.
To develop a novel multi-point plastic scintillation detector (mPSD) capable of accurately measuring dose at multiple positions simultaneously with the use of a single optical guide.
We built a new generation of plastic scintillation detectors composed of multiple scintillating elements along a same optical transmission line. Three different scintillating fibers were optically coupled to a single collecting optical fiber. A primary challenge for this new type of detector is that the output signal is a superposition of multiple scintillation spectra and contaminating elements. Acquisition with a spectrometry setup allows for the implementation of a new hyperspectral approach that accounts for each light-emitting component separately, and allows spectral unmixing. The mPSD and an ion chamber were irradiated in a water phantom with a 6 MV photon beam. Profiles and depth-dose curves were measured and compared between detectors. This detector and the corresponding calibration approach were also applied to Ir- 192 HDR brachytherapy.
Doses measured with the mPSD were in good agreement with the ion chamber measurements for external beam irradiations. Average relative differences of (2.3±1.1)%, (1.6±0.4)% and (0.32±0.19)% were observed for each scintillating element. The mPSD measurements tended to be at least as accurate as published measurements from single-point PSDs. For the Ir-192 HDR brachytherapy application, the average difference between the treatment planning system and the measurements were (4.6±1.0)% per dwell-position and (2.1±1.0)% per catheter. The accuracy of each scintillating element was shown to depend on light attenuation and on the similarity of its scintillation spectrum in comparison to the other light emitters.
The feasibility and accuracy of mPSDs using a single transmission line was demonstrated. In addition to well-documented advantages of single-point PSDs, the multi-point capability of this single-fiber detector makes mPSDs a very promising new technique for quality assurance and on-line in vivo dosimetry.
开发一种新型多点塑料闪烁探测器（mPSD），该探测器能够利用单一光导同时精确测量多个位置的剂量。
我们构建了新一代塑料闪烁探测器，其由沿同一光传输线的多个闪烁元件组成。三根不同的闪烁光纤与一根收集光纤进行光耦合。这种新型探测器面临的一个主要挑战是输出信号是多个闪烁光谱和污染元素的叠加。使用光谱测量装置进行采集可实现一种新的高光谱方法，该方法能分别考虑每个发光组件，并实现光谱解混。mPSD和电离室在水模体中用6MV光子束进行照射。测量并比较了探测器之间的剂量分布曲线和深度剂量曲线。该探测器及相应的校准方法也应用于Ir-192高剂量率近距离放射治疗。
对于外照射，mPSD测量的剂量与电离室测量结果高度一致。每个闪烁元件的平均相对差异分别为(2.3±1.1)%、(1.6±0.4)%和(0.32±0.19)%。mPSD测量的准确性至少与已发表的单点PSD测量结果相当。对于Ir-192高剂量率近距离放射治疗应用，治疗计划系统与测量结果之间的平均差异在每个驻留位置为(4.6±1.0)%，每个导管为(2.1±1.0)%。结果表明，每个闪烁元件的准确性取决于光衰减及其闪烁光谱与其他发光体的相似性。
证明了使用单一传输线的mPSD的可行性和准确性。除了单点PSD已充分记录的优点外，这种单光纤探测器的多点功能使mPSD成为质量保证和在线体内剂量测定中非常有前景的新技术。
