Gifford H C, King M A, Wells R G, Hawkins W G, Narayanan M V, Pretorius P H
Department of Radiology, University of Massachusetts Medical School, Worcester 01655, USA.
IEEE Trans Med Imaging. 2000 May;19(5):463-73. doi: 10.1109/42.870256.
Localization ROC (LROC) observer studies examined whether detector response compensation (DRC) in ordered-subset, expectation-maximization (OSEM) reconstructions helps in the detection and localization of hot tumors. Simulated gallium (Ga-67) images of the thoracic region were used in the study. The projection data modeled the acquisition of attenuated 93- and 185-keV photons with a medium-energy parallel-hole collimator, but scatter was not modeled. Images were reconstructed with five strategies: 1) OSEM with no DRC; 2) OSEM preceded by restoration filtering; 3) OSEM with iterative DRC; 4) OSEM with an ideal DRC; and 5) filtered backprojection (FBP) with no DRC. All strategies included attenuation correction. There were four LROC studies conducted. In a study using a single tumor activity, the ideal DRC offered the best performance, followed by iterative DRC, restoration filtering, OSEM with no DRC, and FBP. Statistical significance at the 5% level was found between all pairs of strategies except for restoration filtering and OSEM with no DRC. A similar ranking was found for a more realistic study using multiple tumor activities. Additional studies considered the effects of OSEM iteration number and tumor activity on the detection improvement that iterative DRC offered with respect to OSEM with no DRC.
局部定位ROC（LROC）观察者研究考察了有序子集期望最大化（OSEM）重建中的探测器响应补偿（DRC）是否有助于热肿瘤的检测和定位。该研究使用了胸部区域的模拟镓（Ga - 67）图像。投影数据模拟了使用中能平行孔准直器采集衰减后的93 keV和185 keV光子的过程，但未对散射进行模拟。图像采用五种策略重建：1）无DRC的OSEM；2）在OSEM之前进行恢复滤波；3）具有迭代DRC的OSEM；4）具有理想DRC的OSEM；5）无DRC的滤波反投影（FBP）。所有策略均包括衰减校正。共进行了四项LROC研究。在一项使用单个肿瘤活性的研究中，理想DRC表现最佳，其次是迭代DRC、恢复滤波、无DRC的OSEM和FBP。除恢复滤波和无DRC的OSEM之间外，所有策略对之间在5%水平上均具有统计学显著性。在一项使用多个肿瘤活性的更现实研究中也发现了类似的排名。其他研究考虑了OSEM迭代次数和肿瘤活性对迭代DRC相对于无DRC的OSEM在检测改善方面的影响。
