Lagerburg Vera, de Nijs Robin, Holm Søren, Svarer Claus
Department of Clinical Physiology, Nuclear Medicine and PET, Copenhagen University Hospital, Copenhagen, Denmark.
Nucl Med Commun. 2012 Jul;33(7):708-18. doi: 10.1097/MNM.0b013e3283537cd0.
One of the main problems in quantification of single photon emission computer tomography imaging is scatter. In iodine-123 (I-123) imaging, both the primary 159 keV photons and photons of higher energies are scattered. In this experimental study, different scatter correction methods, based on energy window subtraction, have been compared with each other.
Iodine-123 single photon emission computed tomography images of a phantom with a known intensity ratio between background and hollow spheres were acquired for three different collimators (low energy high resolution, low energy general purpose, and medium energy general purpose). The hollow spheres were filled with a higher activity concentration than the uniform background activity concentration, resulting in hot spots. Counts were collected in different energy windows, and scatter correction was performed by applying different methods such as effective scatter source estimation, triple and dual energy window (TEW and DEW), double peak window (DPW) and downscatter correction. The intensity ratio between the spheres and the background was used to compare the performance of the different methods.
The results revealed that the efficiency of the scatter correction techniques vary depending on the collimator used. For the low energy high resolution collimator, all correction methods except the effective scatter source estimation and the DPW perform well. For the medium energy general purpose collimator, even without scatter correction, the calculated ratio is close to the real ratio. The DEW and DPW methods tend to overestimate the ratio. For the low energy general purpose collimator, only the DEW and the combined DEW and downscatter correction methods perform well.
The only correction method that provides a ratio that differs by less than 5% from the real ratio for all the collimators is the combined DEW and downscatter correction method.
单光子发射计算机断层扫描成像定量分析中的主要问题之一是散射。在碘 - 123（I - 123）成像中，159 keV 的初级光子和更高能量的光子都会发生散射。在本实验研究中，基于能量窗减法的不同散射校正方法已相互比较。
使用三种不同的准直器（低能高分辨率、低能通用和中能通用）采集了具有已知背景与空心球强度比的体模的碘 - 123 单光子发射计算机断层扫描图像。空心球填充的活度浓度高于均匀背景活度浓度，从而形成热点。在不同能量窗中收集计数，并通过应用不同方法进行散射校正，如有效散射源估计、三能量窗和双能量窗（TEW 和 DEW）、双峰窗（DPW）和下散射校正。球体与背景之间的强度比用于比较不同方法的性能。
结果表明，散射校正技术的效率因所使用的准直器而异。对于低能高分辨率准直器，除有效散射源估计和 DPW 外，所有校正方法效果良好。对于中能通用准直器，即使不进行散射校正，计算出的比值也接近实际比值。DEW 和 DPW 方法往往会高估该比值。对于低能通用准直器，只有 DEW 以及 DEW 与下散射校正相结合的方法效果良好。
对于所有准直器，唯一能提供与实际比值相差小于 5%的比值的校正方法是 DEW 与下散射校正相结合的方法。
