使用交错注射和瞬发伽马正电子发射体的双同位素 PET 的 EM 重建。
EM reconstruction of dual isotope PET using staggered injections and prompt gamma positron emitters.
机构信息
Philips Healthcare, Highland Heights, Ohio 44143.
Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114.
出版信息
Med Phys. 2014 Feb;41(2):022501. doi: 10.1118/1.4861714.
PURPOSE
The aim of dual isotope positron emission tomography (DIPET) is to create two separate images of two coinjected PET radiotracers. DIPET shortens the duration of the study, reduces patient discomfort, and produces perfectly coregistered images compared to the case when two radiotracers would be imaged independently (sequential PET studies). Reconstruction of data from such simultaneous acquisition of two PET radiotracers is difficult because positron decay of any isotope creates only 511 keV photons; therefore, the isotopes cannot be differentiated based on the detected energy.
METHODS
Recently, the authors have proposed a DIPET technique that uses a combination of radiotracer A which is a pure positron emitter (such as(18)F or (11)C) and radiotracer B in which positron decay is accompanied by the emission of a high-energy (HE) prompt gamma (such as (38)K or (60)Cu). Events that are detected as triple coincidences of HE gammas with the corresponding two 511 keV photons allow the authors to identify the lines-of-response (LORs) of isotope B. These LORs are used to separate the two intertwined distributions, using a dedicated image reconstruction algorithm. In this work the authors propose a new version of the DIPET EM-based reconstruction algorithm that allows the authors to include an additional, independent estimate of radiotracer A distribution which may be obtained if radioisotopes are administered using a staggered injections method. In this work the method is tested on simple simulations of static PET acquisitions.
RESULTS
The authors' experiments performed using Monte-Carlo simulations with static acquisitions demonstrate that the combined method provides better results (crosstalk errors decrease by up to 50%) than the positron-gamma DIPET method or staggered injections alone.
CONCLUSIONS
The authors demonstrate that the authors' new EM algorithm which combines information from triple coincidences with prompt gammas and staggered injections improves the accuracy of DIPET reconstructions for static acquisitions so they reach almost the benchmark level calculated for perfectly separated tracers.
目的
双同位素正电子发射断层扫描（DIPET）的目的是创建两个同时注射的 PET 放射性示踪剂的两个单独图像。与两个放射性示踪剂分别成像（顺序 PET 研究）相比，DIPET 缩短了研究时间，减少了患者不适，并产生了完全配准的图像。由于任何同位素的正电子衰变仅产生 511keV 光子，因此从同时采集的两个 PET 放射性示踪剂的数据重建是困难的；因此，不能基于检测到的能量来区分同位素。
方法
最近，作者提出了一种 DIPET 技术，该技术使用放射性示踪剂 A（纯正电子发射体，如（18）F 或（11）C）和放射性示踪剂 B 的组合，其中正电子衰变伴随着高能（HE）瞬时伽马（如（38）K 或（60）Cu）的发射。检测到 HE 伽马与相应的两个 511keV 光子的三重符合事件允许作者识别同位素 B 的线响应（LOR）。使用专用的图像重建算法，这些 LOR 用于分离两个交织的分布。在这项工作中，作者提出了一种新的基于 DIPET 的 EM 重建算法的版本，该算法允许作者包括放射性示踪剂 A 分布的额外独立估计，如果使用交错注射方法给予放射性同位素，则可以获得该分布。在这项工作中，该方法在静态 PET 采集的简单模拟中进行了测试。
结果
作者使用静态采集的蒙特卡罗模拟进行的实验表明，组合方法（串扰误差降低高达 50%）比正电子-伽马 DIPET 方法或单独的交错注射更好。
结论
作者证明，作者结合三重符合事件、瞬时伽马和交错注射信息的新 EM 算法可提高静态采集的 DIPET 重建的准确性，使其达到几乎为完美分离示踪剂计算的基准水平。
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