Comparison of 18F-FDG PET and Optimized Voxel-Based Morphometry for Detection of Alzheimer's Disease: Aging Effect on Diagnostic Performance

Abstract

The aim of this study was to compare optimized voxel-based morphometry (VBM) and 18 F-FDG PET for discrimination between patients with Alzheimer's disease (AD) and healthy subjects in relation to age. Methods: The study population consisted of 2 groups; the first group (27 AD patients and 40 control subjects) was used to determine the locations of significant abnormalities for both PET and VBM using statistical parametric mapping, and the second group (34 AD patients and 50 control subjects) was used to compare the diagnostic performance of PET and VBM. In the second group, a z-score map for PET or VBM of each subject was obtained by comparison with the mean and SD of PET or gray-matter MR images of the control subjects. Receiver-operating-characteristic (ROC) curve analysis was then performed to compare the diagnostic performance between PET and VBM. Furthermore, group 2 was divided into the early-and late-onset subgroups, and ROC analysis was performed for each subgroup. Results: In the first group, VBM revealed a significant decrease in gray-matter concentration in the hippocampus complex in AD, whereas PET showed a significant reduction in 18 F-FDG uptake in the posterior cingulate and parietotemporal lobe. The diagnostic performance of PET (0.988 6 0.008; mean 6 SE), as measured by the area under the ROC curve, was higher than that of VBM with (0.782 6 0.059) or without (0.832 6 0.049) modulation. PET yielded a sensitivity, specificity, and overall accuracy of 100%, 92%, and 95%, respectively, whereas for VBM the sensitivity, specificity, and accuracy were 74%, 92%, and 85%. Modulation for the VBM did not improve these values (56%, 94%, and 79%, respectively). When the early-and late-onset subjects were analyzed separately, the superiority of 18 F-FDG PET was significant only in the early-onset subgroup. Conclusion: The present study indicates that the detection of metabolic alteration by 18 F-FDG PET yields a better diagnostic performance for the discrimination between AD patients and healthy control subjects than does the morphologic approach by VBM, particularly in the early-onset subjects.

Automatic Voxel-Based Morphometry of Structural MRI by SPM8 plus Diffeomorphic Anatomic Registration Through Exponentiated Lie Algebra Improves the Diagnosis of Probable Alzheimer Disease

“…This difference in discrimination performance may arise from the well-known fact of selective atrophy in the medial temporal structures in AD. 1,[4][5][6]16,17 Even if the absolute amount of gray matter of the medial temporal structures is decreased, a concomitant decrease in the total volume of gray matter would decrease specificity. The specificity in ROC analysis of the severity for the target VOI was 17% lower in the condition without than with global normalization in very mild AD.…”

“…This is in line with several previous reports in which lateonset subgroups showed greater atrophy in the medial temporal structures than the early-onset subgroups. 16,17 However global normalization in SPM8 plus DARTEL extended the difference of indicators for a target VOI evenly in the early-onset and late-onset subgroups from indicators in healthy controls. This extension led to almost equal accuracy for discrimination of early-onset and late-onset very mild AD from healthy controls.…”

PET Approaches for Diagnosis of Dementia

“…As such, statistical images are helpful. Nevertheless, FDG-PET generally has a higher accuracy than MR imaging for diagnosing early AD 10,11 and for predicting rapid conversion of MCI to early AD. 12 A combination of PET and other biomarkers is important because imaging and CSF biomarkers can improve prediction of conversion from MCI to AD compared with baseline clinical testing.…”

Potential Clinical Applications of PET/MR Imaging in Neurodegenerative Diseases

“…Most clearly, these findings were shown by means of statistical groupwise comparison of patients versus healthy control subjects. However, the individual value of the specific patterns of atrophy for early diagnosis, prognosis, and differential diagnosis is less apparent (32)(33)(34)(35). A potential reason for this can be found in the assumption that structural and atrophic changes in the brain are a downstream phenomenon in the process of neurodegeneration (36).…”