Abstract
BackgroundIntegrated SPECT/CT enables non-uniform attenuation correction (AC) using built-in CT instead of the conventional uniform AC. The effect of CT-based AC on voxel-based statistical analyses of brain SPECT findings has not yet been clarified. Here, we assessed differences in the detectability of regional cerebral blood flow (CBF) reduction using SPECT voxel-based statistical analyses based on the two types of AC methods.Subjects and MethodsN-isopropyl-p-[123I]iodoamphetamine (IMP) CBF SPECT images were acquired for all the subjects and were reconstructed using 3D-OSEM with two different AC methods: Chang’s method (Chang’s AC) and the CT-based AC method. A normal database was constructed for the analysis using SPECT findings obtained for 25 healthy normal volunteers. Voxel-based Z-statistics were also calculated for SPECT findings obtained for 15 patients with chronic cerebral infarctions and 10 normal subjects. We assumed that an analysis with a higher specificity would likely produce a lower mean absolute Z-score for normal brain tissue, and a more sensitive voxel-based statistical analysis would likely produce a higher absolute Z-score for in old infarct lesions, where the CBF was severely decreased.ResultsThe inter-subject variation in the voxel values in the normal database was lower using CT-based AC, compared with Chang’s AC, for most of the brain regions. The absolute Z-score indicating a SPECT count reduction in infarct lesions was also significantly higher in the images reconstructed using CT-based AC, compared with Chang’s AC (P = 0.003). The mean absolute value of the Z-score in the 10 intact brains was significantly lower in the images reconstructed using CT-based AC than in those reconstructed using Chang’s AC (P = 0.005).ConclusionsNon-uniform CT-based AC by integrated SPECT/CT significantly improved sensitivity and the specificity of the voxel-based statistical analyses for regional SPECT count reductions, compared with conventional uniform Chang's AC.
Highlights
Integrated SPECT/CT provides readily available co-registered CT data for use in attenuation correction (AC) [1] and has been widely introduced in the last decade because of technical developments and innovative low-cost CT technology [2]
We assessed differences in the detectability of regional cerebral blood flow (CBF) reduction using SPECT voxel-based statistical analyses based on the two types of AC methods
Compared with uniform AC, such as that obtained using Chang’s method (Chang’s-AC) based on pooled phantom data [3], the importance of non-uniform AC based on transmission scans or CT (CT-AC) during SPECT imaging of brain perfusion has been advocated in a number of previous reports [4,5,6,7,8]
Summary
Integrated SPECT/CT provides readily available co-registered CT data for use in attenuation correction (AC) [1] and has been widely introduced in the last decade because of technical developments and innovative low-cost CT technology [2]. Compared with uniform AC, such as that obtained using Chang’s method (Chang’s-AC) based on pooled phantom data [3], the importance of non-uniform AC based on transmission scans or CT (CT-AC) during SPECT imaging of brain perfusion has been advocated in a number of previous reports [4,5,6,7,8]. The influence of non-uniform CT-AC methods on the detectability of voxel-based statistical analyses has not been clarified, voxel-based statistical analysis of brain SPECT has become an important solution for data mining in research and clinical diagnosis. We compared the detectability of a voxel-based Z-score analysis for lesions with decreased cerebral blood flow (CBF) between perfusion SPECT reconstructed using Chang’sAC and that reconstructed using CT-AC. We assessed differences in the detectability of regional cerebral blood flow (CBF) reduction using SPECT voxel-based statistical analyses based on the two types of AC methods
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