Beam-on imaging of short-lived positron emitters during proton therapy
Beam-on imaging of short-lived positron emitters during proton therapy
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DOI：
10.1088/1361-6560/aa6b8c
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发表时间：
2017-06-21
影响因子：
3.5
通讯作者：
Dendooven, P.
中科院分区：
文献类型：
--
作者：
Buitenhuis, H. J. T.;Diblen, F.;Dendooven, P.
质子治疗中的体内剂量传递验证可以通过正电子发射断层扫描（PET）对患者体内质子束产生的正电子发射核进行验证。安装在质子治疗设备的处理位置的PET扫描仪，可以在光束上获取数据，可以看到寿命很短的核素和寿命较长的核素。质子治疗中最重要的短寿命核素是N-12 （Dendooven et al . 2015）。医学生物学60 8923-47)，其半衰期为11毫秒。本文介绍了短寿命N-12核的PET成像原理验证实验结果。使用飞利浦数字光子计数模块TEK PET系统，该系统基于安装在数字SiPM光传感器上的LYSO闪烁体。利用KVI-CART回旋加速器的90 MeV质子束，研究了质子束照射过程中PET重合的能量谱和时间谱。与质子束相吻合的事件，如瞬发伽马射线，通过回旋加速器RF的反重合滤波器从数据中去除。由此产生的能谱允许在光束照射期间很好地识别511 keV PET计数。提出了一种通过在回旋加速器波束时间结构中引入一个波束关闭周期来从N-12图像中去除长寿命背景的方法。我们测量了N-12分布的二维图像和一维剖面。使用N-12剖面测量5毫米的范围位移为6 +/- 3毫米。一个更大、更高效、具有更高数据吞吐量的PET系统将允许N-12 PET对辐照远端层的单个点进行波束成像，从而提高信号与背景比，从而提高准确性。仿真结果表明，大型双面板扫描仪在传送后直接对单个点进行成像，可以以毫米精度测量5mm的范围位移：1 x 10(8)个质子为5.5 +/- 1.1 mm, 5 x 10(8)个质子为5.2 +/- 0.5 mm。这使得在治疗期间对剂量给予的快速和准确的反馈成为可能。
In vivo dose delivery verification in proton therapy can be performed by positron emission tomography (PET) of the positron-emitting nuclei produced by the proton beam in the patient. A PET scanner installed in the treatment position of a proton therapy facility that takes data with the beam on will see very short-lived nuclides as well as longer-lived nuclides. The most important short-lived nuclide for proton therapy is N-12 (Dendooven et al 2015 Phys. Med. Biol. 60 8923-47), which has a half-life of 11 ms. The results of a proof-of-principle experiment of beam-on PET imaging of short-lived N-12 nuclei are presented. The Philips Digital Photon Counting Module TEK PET system was used, which is based on LYSO scintillators mounted on digital SiPM photosensors. A 90 MeV proton beam from the cyclotron at KVI-CART was used to investigate the energy and time spectra of PET coincidences during beam-on. Events coinciding with proton bunches, such as prompt gamma rays, were removed from the data via an anti-coincidence filter with the cyclotron RF. The resulting energy spectrum allowed good identification of the 511 keV PET counts during beam-on. A method was developed to subtract the long-lived background from the N-12 image by introducing a beam-off period into the cyclotron beam time structure. We measured 2D images and 1D profiles of the N-12 distribution. A range shift of 5 mm was measured as 6 +/- 3 mm using the N-12 profile. A larger, more efficient, PET system with a higher data throughput capability will allow beam-on N-12 PET imaging of single spots in the distal layer of an irradiation with an increased signal-to-background ratio and thus better accuracy. A simulation shows that a large dual panel scanner, which images a single spot directly after it is delivered, can measure a 5 mm range shift with millimeter accuracy: 5.5 +/- 1.1 mm for 1 x 10(8) protons and 5.2 +/- 0.5 mm for 5 x 10(8) protons. This makes fast and accurate feedback on the dose delivery during treatment possible.