Influence of OSEM, elliptical orbits and background activity on SPECT 3D resolution recovery
Influence of OSEM, elliptical orbits and background activity on SPECT 3D resolution recovery
复制标题
DOI：
10.1088/0031-9155/42/12/015
复制
发表时间：
1997-12-01
影响因子：
3.5
通讯作者：
King, MA
中科院分区：
文献类型：
--
作者：
Pan, TS;Luo, DS;King, MA
在SPECT图像的最大似然期望最大化（MLEM）重建中，如果包括衰减校正（AC）和探测器响应校正（DRC）两者，则重建可能太耗时而不能在临床上有用。使用有序子集期望最大化（OSEM）重建，据报道，重建时间可以大大减少。研究了非均匀衰减介质中点源的归一化半高宽重构问题。我们比较了MLEM与OSEM重建;圆形与椭圆形轨道;以及对象中背景活动的存在与不存在。我们发现：（i）OSEM确实比MLEM加快了10倍的重建速度;（ii）如果AC和DRC都包括在重建中，则分辨率恢复不取决于轨道类型;然而，当存在背景活动时，需要大量迭代来减轻轨道的影响;（iii）背景活动显著减慢点源的分辨率恢复;以及（iv）如果重建仅包括AC而不包括DRC，则改变轨道可以改变恢复的分辨率的各向同性，而引入背景活动可能降低恢复的分辨率并且还改变各向同性。
In maximum-likelihood expectation-maximization (MLEM) reconstruction of SPECT images, if both attenuation correction (AC) and detector response correction (DRC) are included, the reconstruction can be too time consuming to be clinically useful. With use of the ordered-subset expectation-maximization (OSEM) reconstruction, it has been reported that the reconstruction time can be substantially reduced. We investigated the reconstruction of point sources in a non-uniform attenuation medium in terms of the normalized FWHM of these sources. We compared MLEM versus OSEM reconstructions; circular versus elliptical orbits; and the presence versus the absence of background activity in the object. We found: (i) that OSEM does speed up the reconstruction by a factor of 10 over MLEM; (ii) that the resolution recovery does not depend on the type of orbit if both AC and DRC are included in the reconstruction; however, when there is background activity, a significant number of iterations are required to alleviate the effect of orbit; (iii) that background activity significantly slows down the resolution recovery of the point sources; and (iv) that if reconstruction only includes AC, and not DRC, changing orbit can change isotropy of recovered resolution, whereas introducing background activity may degrade the recovered resolution and also changes the isotropy.