Differential automatic diagnosis between Alzheimer's disease and frontotemporal dementia based on perfusion SPECT images

OBJECTIVE

Alzheimer's disease (AD) and frontotemporal dementia (FTD) are among the most frequent neurodegenerative cognitive disorders, but their differential diagnosis is difficult. The aim of this study was to evaluate an automatic method returning the probability that a patient suffers from AD or FTD from the analysis of brain perfusion single photon emission computed tomography images.

METHODS AND MATERIALS

A set of 116 descriptors corresponding to the average activity in regions of interest was calculated from the images of 82 AD and 91 FTD patients. A set of linear (logistic regression and linear discriminant analysis) and non-linear (support vector machines, k-nearest neighbours, multilayer perceptron and kernel logistic PLS) classification methods was subsequently used to ascertain diagnoses. Validation was carried out by means of the leave-one-out protocol. Diagnoses by the classifier and by four physicians (visual assessment) were compared. Since images were acquired in different hospitals, the impact of the medical centre on the diagnosis of both the classifier and the physicians was investigated.

RESULTS

Best results were obtained with support vector machine and partial least squares regression coupled with k-nearest neighbours methods (PLS+K-NN), with an overall accuracy of 88%. PLS+K-NN was however considered as the best method since performances obtained with leave-one-out cross-validation were closer to whole-database learning. The performances of the classifier were higher than those of experts (accuracy ranged from 65 to 72%). Physicians found it more difficult to diagnose the images from centres other than their own, and it affected their performances.

CONCLUSIONS

The performances obtained by the classifier for the differential diagnosis of AD and FTD were found convincing. It could help physicians in daily practice, particularly when visual assessment is inconclusive, or when dealing with multicentre data.

Validation of a Standardized Normalization Template for Statistical Parametric Mapping Analysis of 123I-FP-CIT Images

(123)I-FP-CIT ((123)I-N-omega-fluoropropyl-2beta-carbomethoxy-3beta-(4-iodophenyl)nortropane) is a SPECT dopamine transporter (DAT) tracer that probes dopaminergic cell loss in Parkinson's disease (PD). Quantification of (123)I-FP-CIT images is performed at equilibrium using a ratio (BR) of specific (striatal) to nonspecific (occipital) uptake with values obtained from regions of interest drawn manually over these structures. Statistical parametric mapping (SPM) is a fully automated voxel-based statistical approach that has great potential in the context of DAT imaging. However, the accuracy of the spatial normalization provided by SPM has not been validated for (123)I-FP-CIT images. Our first aim was to create an (123)I-FP-CIT template that does not require the acquisition of patient-specific MRI and to validate the spatial normalization procedure. Next, we hypothesized that this customized template could be used by different SPECT centers without affecting the outcomes of imaging analyses.

METHODS

The spatial normalization to the customized template created with SPM (template A1) was validated using (123)I-FP-CIT images obtained from 6 subjects with essential tremor (ET) with normal DAT status and 6 PD patients. Variability in BR values due to the normalization was evaluated using striatal volume of interest (VOI). To determine whether different SPECT centers could use a unique (123)I-FP-CIT template, we generated 3 other (123)I-FP-CIT templates using different subjects and image-processing schemes. The interchangeability of these templates was assessed using (a) putamen BR values analyzed with the intraclass correlation coefficient (ICC) and the Bland-Altman graphical analysis, and (b) SPM analysis comparing the results of group comparisons-that is, ET versus PD, obtained after normalization to each of the 4 templates.

RESULTS

There was no significant difference between pre- and post-normalization striatal BR values in our study. The mean variability calculated with putamen VOI values after normalization to each template was <10%, with the lowest ICC of 98%. Intergroup analyses performed with VOI and SPM approaches provided similar results independently of the template used.

CONCLUSION

SPM normalization was accurate even in subjects with low striatal (123)I-FP-CIT uptake, making it a promising approach for automatic analysis of (123)I-FP-CIT images using a single customized template at different centers.

Quantitative simultaneous (99m)Tc-ECD/123I-FP-CIT SPECT in Parkinson's disease and multiple system atrophy

PURPOSE

The purpose of this study was to investigate the feasibility and utility of dual-isotope SPECT for differential diagnosis of idiopathic Parkinson's disease (IPD) and multiple system atrophy (MSA).

METHODS

Simultaneous (99m)Tc-ECD/123I-FP-CIT studies were performed in nine normal controls, five IPD patients, and five MSA patients. Projections were corrected for scatter, cross-talk, and high-energy penetration, and iteratively reconstructed while correcting for patient-specific attenuation and variable collimator response. Perfusion and dopamine transporter (DAT) function were assessed using voxel-based statistical parametric mapping (SPM2) and volume of interest quantitation. DAT binding potential (BP) and asymmetry index (AI) were estimated in the putamen and caudate nucleus.

RESULTS

Striatal BP was lower in IPD (55%) and MSA (23%) compared to normal controls (p<0.01) , and in IPD compared to MSA (p<0.05). AI was greater for IPD than for MSA and controls in both the caudate nucleus and the putamen (p<0.05). There was significantly decreased perfusion in the left and right nucleus lentiformis in MSA compared to IPD and controls (p<0.05).

CONCLUSION

Dual-isotope studies are both feasible in and promising for the diagnosis of parkinsonian syndromes.

Diagnostic value of 99mTc-HMDP bone scan in atypical osseous tuberculosis mimicking multiple secondary metastases

STUDY DESIGN

A case of atypical osseous tuberculosis (TB) mimicking multiple secondary metastases on radiologic and nuclear imaging is presented.

OBJECTIVES

To emphasize the contribution of nuclear bone scanning for the assessment of osseous tuberculosis in typical and atypical presentations.

SUMMARY AND BACKGROUND DATA

Skeletal locations of TB mostly involve the dorsolumbar spine and diagnosis is often delayed. The presence of multiple TB sites can mimic secondary metastases and biopsy remains the mainstay for final diagnosis.

METHODS

Clinical symptoms, lab tests, and imaging data are presented. Possible diagnoses are discussed. A review of imaging characteristics in cases of typical and atypical presentations of osseous TB is proposed.

RESULTS

A dorsal spine spondylitis was first diagnosed on a 56-year-old patient presenting neurologic deficit of the left arm. Fine needle aspiration identified bacterial infection but was negative for Mycobacterium tuberculosis. Whole-body bone scan allowed the identification of an asymptomatic sacroiliac lesion, which was accessible to biopsy and gave a final diagnosis.

CONCLUSION

Nuclear bone scanning should be kept in mind when assessing spinal pain in patients at high risk of TB infection or reactivation.

Uptake-1 carrier downregulates in parallel with the beta-adrenergic receptor desensitization in rat hearts chronically exposed to high levels of circulating norepinephrine: implications for cardiac neuroimaging in human cardiomyopathies

Imaging techniques have demonstrated in various cardiomyopathies that an altered uptake of radiolabeled norepinephrine (NE) analogs may coexist with beta-adrenergic receptor downregulation, but the relationships between these 2 alterations and their mechanisms remain unclear. The aim of this study was to evaluate the hypothesis of a chronic elevation of circulating NE levels as a mechanism of decreased uptake of radiolabeled NE analogs and reduced beta-adrenergic receptor sites in the heart.

METHODS

Osmotic minipumps containing either NE or NaCl were implanted intravenously in rats for 5 d. The uptake-1 function was assessed in vitro by measuring in excised hearts (3)H-NE and (123)I-metaiodobenzylguanidine ((123)I-MIBG) uptakes and uptake-1 carrier density using (3)H-mazindol binding assay. The myocardial beta-adrenergic receptor pathway was assessed in vitro by (3)H-CGP 12177 binding and measurement of adenylyl cyclase activity at baseline and under stimulation.

RESULTS

A 34% decrease in (3)H-NE uptake and a 35% decrease in (123)I-MIBG uptake were found in the hearts of rats infused with the NE pump compared with that of rats infused with saline solution (P < 0.05 for both). Moreover, the uptake-1 carrier protein density was decreased by 29% (P < 0.05) and 33% (P < 0.05) in right and left ventricles, respectively, of rats infused with NE compared with those infused with saline solution. Myocardial beta-adrenergic receptor desensitization was associated with a 36% reduction in receptor density in the right ventricle (P < 0.05) and a 31% reduction in the left ventricle (P < 0.05) of rats infused with NE compared with those infused with saline solution.

CONCLUSION

The decrease in myocardial beta-adrenergic receptors and radiolabeled NE analog uptake found in different cardiomyopathies using neuroimaging techniques may be related to a functional mechanism of NE-induced downregulation of both beta-adrenergic receptor and uptake-1 carrier sites.