FDG PET in the differential diagnosis of degenerative parkinsonian disorders: usefulness of voxel-based analysis in clinical practice

Abstract

Background The early differential diagnosis among neurodegenerative parkinsonian disorders becomes essential to set up the correct clinical-therapeutic approach. The increased utilization of [18F] fluoro-deoxy-glucose positron emission tomography (FDG PET) and the pressure for cost-effectiveness request a systematic evaluation and a validation of its utility in clinical practice. This retrospective study aims to consider the contribution, in terms of increasing accuracy and increasing diagnostic confidence, of voxel-based FDG PET analyses in the differential diagnosis of these disorders, including Parkinson’s disease, multiple system atrophy, progressive supranuclear palsy, and cortico-basal syndrome. Method Eighty-three subjects with a clinically confirmed diagnosis of degenerative parkinsonian disorders who underwent FDG brain PET/CT were selected. A voxel-based analysis was set up using statistical parametric mapping (SPM) on MATLAB to produce maps of brain hypometabolism and relative hypermetabolism. Four nuclear physicians (two expert and two not expert), blinded to the patients’ symptoms, other physicians’ evaluations, and final clinical diagnosis, independently evaluated all data by visual assessment and by adopting metabolic maps. Results In not-expert evaluators, the support of both hypometabolism and hypermetabolism maps results in a significant increase in diagnostic accuracy as well as clinical confidence. In expert evaluators, the increase in accuracy and in diagnostic confidence is mainly supported by hypometabolism maps alone. Conclusions In this study, we demonstrated the additional value of combining voxel-based analyses with qualitative assessment of brain PET images. Moreover, maps of relative hypermetabolism can also make their contribution in clinical practice, particularly for less experienced evaluators.

Automatic covariance pattern analysis outperforms visual reading of 18F‐fluorodeoxyglucose‐positron emission tomography (FDG‐PET) in variant progressive supranuclear palsy

“…Thus, a considerable fraction of the between-reader variability can be explained by intra-reader variability, indicating that visual reading of brain FDG-PET for the detection of PSP is difficult, even when supported by voxel-based testing. This is in line with previous studies that reported lower accuracy of non-expert readers than expert readers regarding the detection of PSP in FDG-PET, 47 and lower accuracy and confidence of expert readers for the detection of PSP compared to the detection of Parkinson's disease or multiple system atrophy. 47 Intra-reader and between-reader stability were considerably better in PSP-RS compared to vPSP.…”

“…This is in line with previous studies that reported lower accuracy of non-expert readers than expert readers regarding the detection of PSP in FDG-PET, 47 and lower accuracy and confidence of expert readers for the detection of PSP compared to the detection of Parkinson's disease or multiple system atrophy. 47 Intra-reader and between-reader stability were considerably better in PSP-RS compared to vPSP. Among the patients with vPSP, intra-reader variability was larger for cortical vPSP than for subcortical vPSP.…”

“…29 Here, visual FDG-PET reading was supported by voxel-based statistical testing as in most previous studies. 38,48,49,[57][58][59][60][61][62][63][64][65][66][67][68][69] Voxelbased testing increases reader confidence 47 and accuracy of FDG-PET in parkinsonian syndromes, 47,49,60 particularly in less experienced readers. 47 Procedure guidelines recommend supporting visual FDG-PET analysis with observer-independent approaches such as voxel-based statistical testing "especially for less-skilled readers and, more generally, with the aim to reduce inter-reader variability".…”

“…Age was taken into account as nuisance covariate. 47,48 Single subjects were tested for both hypometabolism and hypermetabolism using a sensitive significance threshold of P ≤ 0.01 uncorrected for multiple testing. 47,49 Visual interpretation of FDG-PET Visual interpretation of the FDG-PET images was based on a standardized display provided to the readers as a two-page pdf-document, a separate pdf-document for each subject (Fig.…”

Clinical and neuroimaging features of the progressive supranuclear palsy- corticobasal degeneration continuum

“…Patterns of both brainstem and cortical hypometabolism can also aid in the differentiation of PSP-RS from the parkinsonian disorders, multiple system atrophy (MSA) and Parkinson's disease (PD) [11]. Visual assessment of patterns of hypometabolism performed well in another study, providing 90% accuracy to differentiate clinically diagnosed PSP from CBS, MSA and PD [12]. However, in that study, accuracy to identify CBS was poor at only 50%.…”