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

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.

Sub-endocardial and sub-epicardial measurement of myocardial blood flow using 13NH3 PET in man.

BACKGROUND: This study examined whether measuring myocardial blood flow (MBF) in the sub-endocardial (SEN) and sub-epicardial (SEP) layers of the left ventricular myocardium using 13NH3 positron emission tomography (PET) and an automated procedure gives reasonable results in patients with known or suspected coronary artery disease (CAD). METHODS: Resting and stress 13NH3 dynamic PET were performed in 70 patients. Using ≥ 70% diameter stenosis in invasive coronary angiography (ICA) to identify significant CAD, we examined the diagnostic value of SEN- and SEP-MBF, and coronary flow reserve (CFR) vs. the corresponding conventional data averaged on the whole wall thickness. RESULTS: ICA demonstrated 36 patients with significant CAD. Their global stress average [1.61 (1.26, 1.87) mL·min-1·g-1], SEN [1.39 (1.2, 1.59) mL·min-1·g-1] and SEP [1.22 (0.96, 1.44) mL·min-1·g-1] MBF were significantly lower than in the 34 no-CAD patients: 2.05 (1.76, 2.52), 1.72 (1.53, 1.89) and 1.46 (1.23, 1.89) mL·min-1·g-1, respectively, all P < .005. In the 60 CAD vs. the 150 non-CAD territories, stress average MBF was 1.52 (1.10, 1.83) vs. 2.06 (1.69, 2.48) mL·min-1·g-1, SEN-MBF 1.33 (1.02, 1.58) vs. 1.66 (1.35, 1.93) mL·min-1·g-1, and SEP-MBF 1.07 (0.80, 1.29) vs. 1.40 (1.12, 1.69) mL·min-1·g-1, respectively, all P < .05. Using receiver operating characteristics analysis for the presence of significant CAD, the areas under the curve (AUC) were all significant (P < .0001 vs. AUC = 0.5) and similar: stress average MBF = 0.79, SEN-MBF = 0.75, and SEP-MBF = 0.73. AUC was 0.77 for the average CFR, 0.75 for SEN, and 0.70 for SEP CFR. The stress transmural perfusion gradient (TPG) AUC (0.51) was not significant. However, stress TPG was significantly lower in segments subtended by totally occluded arteries vs. those subtended by sub-total stenoses: 1.10 (0.86, 1.33) vs. 1.24 (0.98, 1.56), respectively, P < .005. CONCLUSION: Automatic assessment of SEN- and SEP-MBF (and CFR) using 13NH3 PET gives reasonable results that are in good agreement with the conventional average whole wall thickness data. Further studies are needed to examine the utility of layer measurements such as in patients with hibernating myocardium or microvascular disease.

Management of periprosthetic knee joint infections: focus on the role of Nuclear Medicine (v2).

Background: When faced with a painful knee replacement, ruling out infection is mandatory to set the correct therapeutic approach. However, it is not always easy, especially in subclinical/chronic infections. A multidisciplinary approach is necessary to assess in the most correct way each case of suspected periprosthetic knee joint infection. This review explores the role of nuclear medicine investigations in the management of periprosthetic knee infections and their proper use within a multidisciplinary pathway. Methods: A PubMed search was conducted selecting studies from the past 10 years. Results: Triphasic bone scintigraphy has high sensitivity (93%) but poor specificity (56%) for periprosthetic joint infections of the knee, with a high negative predictive value (NPV), ranging from 96% to 100%. Consequently, a negative bone scan is useful in ruling out infection. In contrast, radiolabeled leukocyte scintigraphy is characterized by a sensitivity of 85.7-93%, specificity of 93.6-100%, diagnostic accuracy of 92.6-98%, NPV of 93-97.8%, and positive predictive value (PPV) of 66.7-100%. By adding a tomographic acquisition with hybrid single-photon emission computed tomography combined with computed tomography technique (SPECT/CT), the diagnostic accuracy increases. Because 18F-fluorodeoxyglucose (FDG) accumulates at both sites of inflammation and infection, FDG positron emission tomography (PET/CT) shows low specificity. Conclusions: A common decision-making process in the diagnosis of periprosthetic joint infection is not yet validated and multidisciplinary integration is mandatory. In this context, nuclear medicine can contribute decisively.

Evaluation of Age and Sex-Related Metabolic Changes in Healthy Subjects: An Italian Brain 18F-FDG PET Study.

BACKGROUND: 18F-fluorodeoxyglucose (18F-FDG) positron-emission-tomography (PET) allows detection of cerebral metabolic alterations in neurological diseases vs. normal aging. We assess age- and sex-related brain metabolic changes in healthy subjects, exploring impact of activity normalization methods. METHODS: brain scans of Italian Association of Nuclear Medicine normative database (151 subjects, 67 Males, 84 Females, aged 20-84) were selected. Global mean, white matter, and pons activity were explored as normalization reference. We performed voxel-based and ROI analyses using SPM12 and IBM-SPSS software. RESULTS: SPM proved a negative correlation between age and brain glucose metabolism involving frontal lobes, anterior-cingulate and insular cortices bilaterally. Narrower clusters were detected in lateral parietal lobes, precuneus, temporal pole and medial areas bilaterally. Normalizing on pons activity, we found a more significant negative correlation and no positive one. ROIs analysis confirmed SPM results. Moreover, a significant age × sex interaction effect was revealed, with worse metabolic reduction in posterior-cingulate cortices in females than males, especially in post-menopausal age. CONCLUSIONS: this study demonstrated an age-related metabolic reduction in frontal lobes and in some parieto-temporal areas more evident in females. Results suggested pons as the most appropriate normalization reference. Knowledge of age- and sex-related cerebral metabolic changes is critical to correctly interpreting brain 18F-FDG PET imaging.

The Role of 18F-FDG PET/CT in Staging and Prognostication of Mantle Cell Lymphoma: An Italian Multicentric Study.

Mantle cell lymphoma (MCL) is an aggressive lymphoma subtype with poor prognosis in which 18F-FDG-PET/CT role in treatment response evaluation and prediction of outcome is still unclear. The aim of this multicentric study was to investigate the role of 18F-FDG-PET/CT in staging MCL and the prognostic role of Deauville criteria (DC) in terms of progression-free survival (PFS) and overall survival (OS). We retrospectively enrolled 229 patients who underwent baseline and end-of-treatment (eot) 18F-FDG-PET/CT after first-line therapy. EotPET/CT scans were visually interpreted according to DC. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of PET/CT for evaluation of bone marrow (BM) were 27%, 100%, 100%, 48% and 57%, respectively. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of PET/CT for evaluation of the gastrointestinal (GI) tract were 60%, 99%, 93%, 90% and 91%, respectively. At a median follow-up of 40 months, relapse occurred in 104 cases and death in 49. EotPET/CT results using DC significantly correlated with PFS, not with OS. Instead, considering OS, only MIPI score was significantly correlated. In conclusion, we demonstrated that MCL is an FDG-avid lymphoma and 18F-FDG-PET/CT is a useful tool for staging purpose, showing good specificity for BM and GI evaluation, but suboptimal sensitivity. EotPET/CT result was the only independent significant prognostic factor that correlated with PFS.