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.

Role of molecular imaging in the management of patients affected by inflammatory bowel disease: State-of-the-art

AIM

To present the current state-of-the art of molecular imaging in the management of patients affected by inflammatory bowel disease (IBD).

METHODS

A systematic review of the literature was performed in order to find important original articles on the role of molecular imaging in the management of patients affected by IBD. The search was updated until February 2016 and limited to articles in English.

RESULTS

Fifty-five original articles were included in this review, highlighting the role of single photon emission tomography and positron emission tomography.

CONCLUSION

To date, molecular imaging represents a useful tool to detect active disease in IBD. However, the available data need to be validated in prospective multicenter studies on larger patient samples.