Extraction,selection and comparison of features for an effective automated computer-aided diagnosis of Parkinson’s disease based on [<Superscript>123</Superscript>I]FP-CIT SPECT images

Purpose

This work aimed to assess the potential of a set of features extracted from [¹²³I]FP-CIT SPECT brain images to be used in the computer-aided “in vivo” confirmation of dopaminergic degeneration and therefore to assist clinical decision to diagnose Parkinson’s disease.

Methods

Seven features were computed from each brain hemisphere: five standard features related to uptake ratios on the striatum and two features related to the estimated volume and length of the striatal region with normal uptake. The features were tested on a dataset of 652 [¹²³I]FP-CIT SPECT brain images from the Parkinson’s Progression Markers Initiative. The discrimination capacities of each feature individually and groups of features were assessed using three different machine learning techniques: support vector machines (SVM), k-nearest neighbors and logistic regression.

Results

Cross-validation results based on SVM have shown that, individually, the features that generated the highest accuracies were the length of the striatal region (96.5%), the putaminal binding potential (95.4%) and the striatal binding potential (93.9%) with no statistically significant differences among them. The highest classification accuracy was obtained using all features simultaneously (accuracy 97.9%, sensitivity 98% and specificity 97.6%). Generally, slightly better results were obtained using the SVM with no statistically significant difference to the other classifiers for most of the features.

Conclusions

The length of the striatal region uptake is clinically useful and highly valuable to confirm dopaminergic degeneration “in vivo” as an aid to the diagnosis of Parkinson’s disease. It compares fairly well to the standard uptake ratio-based features, reaching, at least, similar accuracies and is easier to obtain automatically. Thus, we propose its day to day clinical use, jointly with the uptake ratio-based features, in the computer-aided diagnosis of dopaminergic degeneration in Parkinson’s disease.

     

Decreased striatal D<Subscript>2</Subscript> receptor density associated with severe behavioral abnormality in Alzheimer’s disease

OBJECTIVES: Since patients manifesting behavioral and psychological symptoms of dementia (BPSD) are a burden for their families and caregivers, the underlying neurobiological mechanism of this condition should be clarified. Using positron emission tomography (PET), we previously reported that wandering behavior in dementia was associated with a disturbed dopaminergic neuron system. We herein investigated the relationship between the severity of BPSD and the striatal D2 receptor density in Alzheimer's disease (AD). METHODS: Ten patients with probable AD as per the National Institute of Neurological and Communicative Disorders and Stroke (NINCDS) and the AD and Related Disorders Association (ADRDA) criteria and five normal subjects were examined with PET. The tracer used was [11C]raclopride (D2 antagonist). The uptake of [11C] raclopride was calculated as the estimation of binding potential (BP) of the striatum to the cerebellum. The AD patients were institutionalized in multiple nursing homes, and their BPSD were evaluated by the Behavioral Pathology in AD Frequency Weighted Severity Scale (BEHAVE-AD-FW) scale (Reisberg). RESULTS: There was a significant inverse Spearman's correlation between BEHAVE-AD-FW score and the BP, especially between the score of the behavioral domain and the BP values. The BP was found to be lower in severer BPSD patients. CONCLUSIONS: Patients with AD who manifest severe BPSD may have some dysfunction of striatal dopamine metabolism compared with those without BPSD.     

Longitudinal Decline of Striatal Subregional [<Superscript>18</Superscript>F]FP-CIT Uptake in Parkinson’s Disease

Purpose

Dopamine transporter imaging is suggested to be a useful imaging biomarker for Parkinson’s disease (PD) progression and monitoring drug effects. We investigated the longitudinal decline characteristics of striatal [¹⁸F]FP-CIT uptake in PD.

Methods

We retrospectively reviewed 35 PD patients and 9 non-PD patients. All patients underwent [¹⁸F]FP-CIT PET at the initial diagnosis and follow-up. PET images were spatially normalized and analyzed with eight striatal and one occipital VOI templates. We measured the specific to non-specific binding ratio (SNBR) of the striatal subregions and calculated the absolute annual reduction (AAR) and relative annual reduction (%RAR) of the SNBRs.

Results

Total striatal SNBRs in PD patients were significantly lower than those in non-PD patients, with the most significant difference in the posterior putamen. Both AAR (0.26 ± 0.14 vs. 0.09 ± 0.19, p < 0.05) and %RAR (6.9 ± 3.5 vs. 1.2 ± 2.7, p < 0.001) of total striatal SNBRs were significantly greater in PD than non-PD patients. There were no significant differences in the AAR and %RAR of total striatal SNBRs between elderly and young onset PD. The AARs of the posterior putamen were higher in early PD than in advanced PD. Conversely, the %RARs were not significantly different between early and more advanced PD. The disease duration was significantly negatively correlated with the AAR but not with the %RAR of the posterior putamen.

Conclusions

The longitudinal decline of striatal [¹⁸F]FP-CIT uptake in PD was nonlinear and significantly faster than that in non-PD, with a different rate of decline among the striatal subregions.

     

Intra-individual comparison of p-[<Superscript>123</Superscript>I]-iodo-L-phenylalanine and L-3-[<Superscript>123</Superscript>I]-iodo-α-methyl-tyrosine for SPECT imaging of gliomas

Objectives Radioactive amino-acids accumulate in gliomas even with an intact blood-brain-barrier. L-3-[¹²³I]-iodo-α-methyl-tyrosine (IMT) is well established for SPECT imaging of gliomas. Recently, we introduced p-[¹²³I]-iodo-L-phenylalanine (IPA) for the characterisation of brain lesions. This study compares both tracers in glioma patients. Methods Eleven patients with gliomas (1 WHO grade 1, 5 grade 2, 1 grade 3, 2 grade 4 gliomas, 1 unconfirmed upgrading and 1 post-therapeutic non-neoplastic lesion) underwent SPECT imaging with IPA (early and delayed acquisitions at 30 min and 3 h) and IMT (early only). Maximum tumour-to-brain ratios (TBR) were calculated using region-of-interest analysis to assess uptake of IMT and IPA. Imaging results were compared to histopathological findings. Results Early TBRs of IMT and IPA were strongly correlated (r = 0.828, p = 0.002). TBRs were higher for IMT than IPA (1.95±0.50 versus 1.79±0.42; p < 0.05), but independent from tumour cell density (p > 0.1). Visual interpretation by different observers was more concordant for IMT-SPECT than IPA-SPECT (kappa 1.0 versus 0.774). No differences in early TBRs were observed between low-grade and high-grade gliomas for IMT (1.97±0.53 versus 2.21±0.44, p > 0.5) or IPA (1.70±0.23 versus 2.21±0.56, p = 0.167) with a trend to higher TBRs in low-grade tumours for IMT (p = 0.093). In contrast to the known wash-out of IMT, we observed persistent accumulation of IPA in gliomas. Conclusions IPA shows lower TBRs than IMT, especially in low-grade tumours, so IMT should be preferred for the delineation of low-grade gliomas by SPECT imaging. Due to its prolonged retention, however, IPA remains promising for therapeutic use in gliomas after labelling with I-131. This work was supported by a grant from the “Deutsche Krebshilfe” (70-3024-He 1).     

Reduced striatal D<Subscript>2</Subscript> receptor binding in myoclonus–dystonia

Purpose  

To study striatal dopamine D₂ receptor availability in DYT11 mutation carriers of the autosomal dominantly inherited disorder myoclonus–dystonia (M–D).     

Automated striatal uptake analysis of <Superscript>18</Superscript>F-FDOPA PET images applied to Parkinson’s disease patients

Objective  

6-[¹⁸F]Fluoro-l-DOPA (FDOPA) is a radiopharmaceutical valuable for assessing the presynaptic dopaminergic function when used with positron emission tomography (PET). More specifically, the striatal-to-occipital ratio (SOR) of FDOPA uptake images has been extensively used as a quantitative parameter in these PET studies. Our aim was to develop an easy, automated method capable of performing objective analysis of SOR in FDOPA PET images of Parkinson’s disease (PD) patients.     

Reproducibility of dopamine transporter density measured with<Superscript>123</Superscript>I-FPCIT SPECT in normal control and Parkinson’s disease patients

The objective of this study was to evaluate the reproducibility of 123I-FPCIT SPECT by using whole striatal region of interest (ROI) and subdivided ROI in normal controls (NC) and Parkinson's disease (PD) patients. METHODS: Ten NC and 6 PD received a SPECT scan for 6 hours postinjection of FPCIT. The distribution volume ratio (R(V)) and specific-nonspecific tissue activity ratio (RT) were measured as an outcome measure. The test/retest reproducibility of R(V) and R(T) was evaluated by calculating the test/retest difference, variability, and reliability. RESULTS: There were no significant test/retest differences for any regions in either the NC or PD. The test/retest variability/reliability of Rv was 5.53+/-4.12%/0.89 in NC, 4.50+/-5.31%/0.99 in PD with whole striatal ROI, 4.29+/-0.78%/ 0.94+/-0.03 in NC, and 6.87+/-1.23 %/0.98+/-0.01 in PD with subdivided ROI. The test/retest variability/reliability of RT was 11.1+/-10.4%/0.59 in NC, 7.84+/-8.94%/0.95 in PD with whole striatal ROI, 11.9+/-1.22%/0.65+/-0.06 in NC, and 12.2+/-4.00%/0.95+/-0.03 in PD with subdivided ROI. CONCLUSION: R(V) is highly reproducible and reliable compared with RT in both NC and PD as an outcome measure.     

Correlations between dopamine transporter density measured by <Superscript>123</Superscript>I-FP-CIT SPECT and regional gray matter volume in Parkinson’s disease

Purpose

Parkinson’s disease (PD) is caused by a selective degeneration of dopamine neurons. The relationship between dopamine transporter (DAT) density and gray matter volume has been unclear. Here we investigated the voxelwise correlation between gray matter volume and DAT binding measured by ¹²³I-N-ω-fluoropropyl-2β-carboxymethoxy-3β-(4-iodophenyl)nortropane (¹²³I-FP-CIT) single-photon emission computed tomography (SPECT; DaTscan? imaging) in PD.

Materials and methods

Thirty-one male patients with PD were examined with MRI and DaTscan. To measure nigrostriatal dopaminergic degeneration in PD, the specific binding ratio (SBR) of the striatum was obtained by DaTscan. Voxel-based morphometry (VBM) of 3D T1-weighted images was used to evaluate the relationships between the regional gray matter volume and the SBR in the striatum.

Results

There were significant positive correlations between the SBR and the gray matter volume in the right pulvinar and posterior middle temporal gyrus and a trend level in the left pulvinar, all of which are associated with the second visual pathway.

Conclusion

The nigrostriatal dopaminergic degeneration might affect the secondary visual pathway, leading to visual dysfunctions in PD.

     

Clinical correlation of the binding potential with <Superscript>123</Superscript>I-FP-CIT in de novo idiopathic Parkinson’s disease patients

Purpose  The aim of this study was to evaluate the accuracy of different single-photon emission computed tomography (SPECT) reconstruction techniques in measuring striatal N-ω-fluoropropyl-2β-carbomethoxy-3β-4-[¹²³I]iodophenyl-nortropane (¹²³I-FP-CIT) binding in de novo Parkinson’s disease (PD) patients, in order to find a correlation with clinical scales of disease severity in the initial phases of disease. Methods  Thirty-six de novo PD patients underwent ¹²³I-FP-CIT SPECT and MRI scan. SPECT data were reconstructed with filtered back projection (FBP), with an iterative algorithm (ordered subset expected maximization, OSEM) and with a method previously developed in our institution, called least-squares (LS) method. The ratio of specific to non-specific striatal ¹²³I-FP-CIT binding (binding potential, BP) was used as the outcome measure with all the reconstruction methods (BP_FBP, BP_OSEM, BP_LS). Results  The range of values of striatal BP_LS was significantly greater than BP_FBP and BP_OSEM. For all striatal regions, estimates of BP_FBP correlated well with BP_OSEM (r = 0.84) and with BP_LS (r = 0.64); BP_OSEM correlated significantly with BP_LS (r = 0.76). A good correlation was found between putaminal BP_LS and Hoen and Yahr, Unified PD Rating Scale (UPDRS) and lateralized UPDRS motor scores (r = −0.46, r = −0.42, r = −0.39, respectively). Neither putaminal BP_FBP nor putaminal BP_OSEM correlated with any of these motor scores. Conclusions  In de novo PD patients, ¹²³I-FP-CIT BP values derived from FBP and OSEM reconstruction techniques do not permit to differentiate PD severity. The LS method instead finds a correlation between striatal BP and disease severity scores. The results of this study support the use of ¹²³I-FP-CIT BP values estimated with the LS method as a biomarker of PD severity.     

Relationship between striatal [123I]β-CIT binding and four major clinical signs in Parkinson’s disease

We investigated the correlation between clinical severity and striatal [123I]-CIT binding in 12 patients with Parkinson's Disease (PD: 6 men and 6 women, age: 65 +/- 7 years, Hoehn & Yahr stage: 1 to 3). The clinical severity of PD patients was measured with the Unified Parkinson's Disease Rating Scale (UPDRS) after withdrawal of antiparkinsonian medication at least 12 hours before assessment. [123I]beta-CIT binding in the caudate and putamen was measured at 3 hours [V'3 (day 1)], and at 24 hours [V'3 (day 2)) after tracer injection with small square ROIs. The specific striatal uptake index (day 2) was calculated with large square ROIs that encompassed the whole striatum. The best correlation (r = -0.82, p < 0.0012) was between putamenal V'3 (day 2) and the motor UPDRS scores. When the motor UPDRS scores were divided into four subscales, bradykinesia was the only sign that correlated significantly with putamenal V'3 (day 2) (r = -0.81, p < 0.002). [123I]beta-CIT SPECT is a useful marker of disease severity in PD with potential utility in the serial monitoring of disease progression.     

Early [<Superscript>18</Superscript>F]florbetaben and [<Superscript>11</Superscript>C]PiB PET images are a surrogate biomarker of neuronal injury in Alzheimer’s disease

Purpose

[¹⁸F]FDG is a commonly used neuronal injury biomarker for early and differential diagnosis of dementia. Typically, the blood supply to the brain is closely coupled to glucose consumption. Early uptake of the Aβ tracer [¹¹C]PiB on PET images is mainly determined by cerebral blood flow and shows a high correlation with [¹⁸F]FDG uptake. Uptake data for ¹⁸F-labelled Aβ PET tracers are, however, scarce. We investigated the value of early PET images using the novel Aβ tracer [¹⁸F]FBB in the diagnosis of Alzhimers disease (AD).

Methods

This retrospective analysis included 22 patients with MCI or dementia who underwent dual time-point PET imaging with either [¹¹C]PiB (11 patients) or [¹⁸F]FBB (11 patients) in routine clinical practice. Images were acquired 1 – 9 min after administration of both tracers and 40 – 70 min and 90 – 110 min after administration of [¹¹C]PiB and [¹⁸F]FBB, respectively. The patients also underwent [¹⁸F]FDG brain PET imaging. PET data were analysed visually and semiquantitatively. Associations between early Aβ tracer uptake and dementia as well as brain atrophy were investigated.

Results

Regional visual scores of early Aβ tracer and [¹⁸F]FDG PET images were significantly correlated (Spearman’s ρ?=?0.780, P?<?0.001). Global brain visual analysis revealed identical results between early Aβ tracer and [¹⁸F]FDG PET images. In a VOI-based analysis, the early Aβ tracer data correlated significantly with the [¹⁸F]FDG data (r?=?0.779, P?<?0.001), but there were no differences between [¹⁸F]FBB and [¹¹C]PiB. Cortical SUVRs in regions typically affected in AD on early Aβ tracer and [¹⁸F]FDG PET images were correlated with MMSE scores (ρ?=?0.458, P?=?0.032, and ρ?=?0.456, P?=?0.033, respectively). A voxel-wise group-based search for areas with relatively higher tracer uptake on early Aβ tracer PET images compared with [¹⁸F]FDG PET images revealed a small cluster in the midbrain/pons; no significant clusters were found for the opposite comparison.

Conclusion

Early [¹⁸F]FBB and [¹¹C]PiB PET brain images are similar to [¹⁸F]FDG PET images in AD patients, and these tracers could potentially be used as biomarkers in place of [¹⁸F]FDG. Thus, Aβ tracer PET imaging has the potential to provide biomarker information on AD pathology and neuronal injury. The potential of this approach for supporting the diagnosis of AD needs to be confirmed in prospective studies in larger cohorts.

     

The clinical utility of 99<Superscript>m</Superscript>Tc-HMPAO SPECT in Fahr’s disease

Fahr's disease is a rare neurodegenerative syndrome, characterized by massive symmetrical intracerebral calcifications of the basal ganglia, dentate nuclei of the cerebellum, and the adjacent parenchyma. Computerized tomography (CT) is considerably more sensitive to detect these intracranial calcifications than other imaging modalities. The clinical, CT scan, and 99(m)Tc-D,L-hexamethylpropylene amine oxime (99(m)Tc-HMPAO) brain perfusion single-photon emission computerized tomography (SPECT) findings in a 42-year-old woman with Fahr's disease are reported, and the clinical utility of 99(m)Tc-HMPAO SPECT findings in Fahr's disease is discussed in this article. In conclusion, 99(m)Tc-HMPAO brain perfusion SPECT seems to be useful in the clinical approach to Fahr's disease, and may provide more specific and clinically relevant information when compared with anatomical imaging.     

Imaging of dopamine transporters and D<Subscript>2</Subscript> receptors in patients with Parkinson’s disease and multiple system atrophy

Purpose The aim of this study was to ascertain whether combined presynaptic and postsynaptic dopaminergic single-photon emission computed tomography (SPECT) scanning is useful for differentiation between patients with idiopathic Parkinsons disease (IPD), patients with multiple system atrophy of the striatonigral type (MSA) and healthy subjects.Methods SPECT measurements of the dopamine transporter (DAT) were done with ¹²³I--CIT, while for determination of the dopamine D₂-like receptors (D₂), ¹²³I-epidepride was used. Clinical evaluation and SPECT scans were carried out in 14 patients with IPD, eight patients with MSA and 11 healthy age-matched control subjects.Results Putaminal DAT binding was reduced to 32% of control values in IPD and to 19% of control values in MSA . Significantly higher striatal asymmetry in DAT binding was found in MSA than in controls, but IPD patients had significantly higher asymmetry than MSA patients. Striatal D₂ binding did not differ significantly between patients and healthy controls but the ratio between caudate DAT and D₂ binding was significantly higher in patients with IPD than in those with MSA, even when disease severity was taken into account.Conclusion Patients with reduced striatal ¹²³I--CIT binding and a side-to-side difference greater than 15% are likely to suffer from IPD. Patients with reduced striatal ¹²³I--CIT binding and a side-to-side difference of between 5% and 15% are more likely to have MSA. ¹²³I-epidepride SPECT measurements may add further diagnostic information, since the ratio between DAT and D₂ receptor binding is significantly higher in IPD than in MSA.     

Early-stage [123I]β-CIT SPECT and long-term clinical follow-up in patients with an initial diagnosis of Parkinson’s disease

Purpose Previous studies using dopamine transporter single-photon emission computed tomography (SPECT) to try and distinguish between patients with idiopathic Parkinsons disease (IPD) and patients with atypical parkinsonian syndromes (APS) have mainly focussed on patients with an already established clinical diagnosis of several years duration. Differences in the pattern of striatal involvement between IPD and APS have been found in only few studies. We hypothesized that distinguishing SPECT features might be most pronounced at an early disease stage, and the purpose of the present study was to investigate this hypothesis.Methods The study included 72 patients with an initial clinical diagnosis of IPD, supported by decreased striatal [¹²³I]-CIT binding on baseline SPECT. In ten patients, the diagnosis was changed to APS over a mean follow-up period of 62 months. We retrospectively compared the patterns of striatal involvement on the baseline SPECT scans between the group of patients (re)diagnosed with APS and the remaining 62 patients in whom a diagnosis of IPD was maintained.Results In the group of patients with APS, baseline [¹²³I]-CIT binding in both caudate nuclei was lower than in the group of patients with IPD. In addition, putamen to caudate binding ratios were higher in the group of APS patients. In spite of these differences, individual binding values showed considerable overlap between the groups.Conclusion [¹²³I]-CIT SPECT scanning in early-stage, untreated parkinsonian patients revealed a relative sparing of the caudate nucleus in patients with IPD as compared to patients later (re)diagnosed with APS. Nevertheless, the pattern of striatal involvement appears to have little predictive value for a later re-diagnosis of APS in individual cases.     

PET imaging of α<Subscript>7</Subscript> nicotinic acetylcholine receptors: a comparative study of [<Superscript>18</Superscript>F]ASEM and [<Superscript>18</Superscript>F]DBT-10 in nonhuman primates,and further evaluation of [<Superscript>18</Superscript>F]ASEM in humans

Purpose

The α₇ nicotinic acetylcholine receptor (nAChR) is implicated in many neuropsychiatric disorders, making it an important target for positron emission tomography (PET) imaging. The first aim of this work was to compare two α₇ nAChRs PET radioligands, [¹⁸F]ASEM (3-(1,4-diazabicyclo[3.2.2]nonan-4-yl)-6-([¹⁸F]fluorodibenzo[b,d]thiophene 5,5-dioxide) and [¹⁸F]DBT-10 (7-(1,4-diazabicyclo[3.2.2]nonan-4-yl)-2-([¹⁸F]fluorodibenzo[b,d]thiophene 5,5-dioxide), in nonhuman primates. The second aim was to assess further the quantification and test-retest variability of [¹⁸F]ASEM in humans.

Methods

PET scans with high specific activity [¹⁸F]ASEM or [¹⁸F]DBT-10 were acquired in three rhesus monkeys (one male, two female), and the kinetic properties of these radiotracers were compared. Additional [¹⁸F]ASEM PET scans with blocking doses of nicotine, varenicline, and cold ASEM were acquired separately in two animals. Next, six human subjects (five male, one female) were imaged with [¹⁸F]ASEM PET for 180 min, and arterial sampling was used to measure the parent input function. Different modeling approaches were compared to identify the optimal analysis method and scan duration for quantification of [¹⁸F]ASEM distribution volume (V _T). In addition, retest scans were acquired in four subjects (three male, one female), and the test-retest variability of V _T was assessed.

Results

In the rhesus monkey brain [¹⁸F]ASEM and [¹⁸F]DBT-10 exhibited highly similar kinetic profiles. Dose-dependent blockade of [¹⁸F]ASEM binding was observed, while administration of either nicotine or varenicline did not change [¹⁸F]ASEM V _T. [¹⁸F]ASEM was selected for further validation because it has been used in humans. Accurate quantification of [¹⁸F]ASEM V _T in humans was achieved using multilinear analysis with at least 90 min of data acquisition, resulting in V _T values ranging from 19.6?±?2.5 mL/cm³ in cerebellum to 25.9?±?2.9 mL/cm³ in thalamus. Test-retest variability of V _T was 11.7?±?9.8%.

Conclusions

These results confirm [¹⁸F]ASEM as a suitable radiotracer for the imaging and quantification of α₇ nAChRs in humans.

     

Test–retest stability of cerebral A<Subscript>1</Subscript> adenosine receptor quantification using [<Superscript>18</Superscript>F]CPFPX and PET

PURPOSE: The goal of the present study was to evaluate the reproducibility of cerebral A1 adenosine receptor (A1AR) quantification using [18F]CPFPX and PET in a test-retest design. METHODS: Eleven healthy volunteers were studied twice. Eight brain regions ranging from high to low receptor binding were examined. [18F]CPFPX was injected as a bolus with subsequent infusion over 120 min. Various outcome parameters were compared based on either metabolite-corrected venous blood sampling [e.g. apparent equilibrium total distribution volume (DVt')] or a reference region [ratio of specific to non-specific distribution volume (BP2)]. RESULTS: Test-retest variability was low in the outcome measure BP2 (on average 5.9%) and moderate in DVt' (on average 13.2%). Regarding reproducibility, the outcome parameter BP2 showed an intra-class correlation coefficient (ICC) of 0.94 +/- 0.1. For DVt' the between-subject coefficient of variation (%CV) was similar to the within-subject %CV (around 10%), resulting in a poor ICC of 0.06 +/- 0.2. CONCLUSION: Our results suggest that quantification of [18F]CPFPX imaging is reproducible and reliable for PET studies of the cerebral A1AR. Among the outcome parameters the non-invasive measures were of superior test-retest stability over the invasive.     

A novel computer-assisted image analysis of [<Superscript>123</Superscript>I]β-CIT SPECT images improves the diagnostic accuracy of parkinsonian disorders

Purpose  

The purpose of this study was to develop an observer-independent algorithm for the correct classification of dopamine transporter SPECT images as Parkinson’s disease (PD), multiple system atrophy parkinson variant (MSA-P), progressive supranuclear palsy (PSP) or normal.     

Progression of dopamine transporter decline in patients with the Parkinson variant of multiple system atrophy: a voxel-based analysis of [<Superscript>123</Superscript>I]β-CIT SPECT

Purpose  

We characterized the progression of dopamine transporter (DAT) decline in the striatum and extrastriatal regions including the midbrain and pons of patients with the Parkinson variant of multiple system atrophy (MSA-P) and compared longitudinally collected SPECT results with those in a cohort of patients with Parkinson's disease (PD).