Imaging of the dopaminergic system in differential diagnosis of dementia

Practical Application of DaTQUANT with Optimal Threshold for Diagnostic Accuracy of Dopamine Transporter SPECT

Evaluation of Parkinsonian Syndromes (PS) with Ioflupane iodine-123 dopamine transporter single photon emission computed tomography (DaT-SPECT), in conjunction with history and clinical examination, aids in diagnosis. FDA-approved, semi-quantitative software, DaTQUANT^TM (GE Healthcare, Chicago, IL, USA) is available to assist in interpretation. This study aims to evaluate the optimal variables and thresholds of DaTQUANT to yield the optimal diagnostic accuracy. It is a retrospective review with three different patient populations. DaT-SPECT images from all three study groups were evaluated using DaTQUANT^TM software, and both single and multi-variable logistic regression were used to model PS status. The optimal models were chosen via accuracy, sensitivity, and specificity, then evaluated on the other study groups. Among single variable models, the posterior putamen yielded the highest accuracy (84% to 95%), while balancing sensitivity and specificity. Multi-variable models did not substantially improve the accuracy. When the optimal single variable models for each group were used to evaluate the remaining two groups, comparable results were achieved. In typical utilization of DaT-SPECT for differentiation between nigrostriatal degenerative disease (NSDD) and non-NSDD, the posterior putamen was the single variable that yielded the highest accuracy across three different patient populations. The posterior putamen’s recommended thresholds for DaTQUANT are SBR ≤ 1.0, z-score of ≤−1.8 and percent deviation ≤ −0.34.

Cerebral Glucose Metabolism and Dopaminergic Function in Patients with Corticobasal Syndrome

BACKGROUND AND PURPOSE

The corticobasal syndrome (CBS) is a clinical diagnosis that comprises a group of rare neurodegenerative diseases manifesting in movement disorder and cognitive impairment. While diagnosis is based upon clinical criteria, there have been a number of molecular imaging studies, albeit in rather small cohorts. Therefore, we investigated the pattern of cerebral glucose metabolism, as well as dopamine transporter (DAT) availability in a large and clinically well-defined cohort.

METHODS

Thirty-four patients fulfilling either the Armstrong or the Boeve criteria were assessed with [¹⁸ F]-2-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) and/or [¹²³ I]-Ioflupane single-photon-emission-computed tomography (SPECT) for DAT availability. A small subset of patients had also undergone D_2/3 receptor imaging. Imaging data were analyzed using both statistical parametric mapping and a volume-of-interest-based approach relative to data from healthy controls.

RESULTS

Significant reductions of the cortical glucose metabolism were observed in the central region and the adjacent frontal and parietal association areas contralateral to the side with predominant motor symptoms. Reductions were also evident in the basal ganglia, notably in the putamen contralateral to the clinically affected side, and in the bilateral thalamus. DAT availability was reduced bilaterally, most distinctly on the side contralateral to the main motor symptoms.

CONCLUSIONS

We replicated and refined earlier findings of impaired glucose metabolism and nigrostriatal degeneration in CBS, highlighting asymmetric cortical and subcortical hypometabolism, symmetrically reduced metabolism in the thalamus, and only a slightly asymmetric reduction in DAT, while D_2/3 receptors seem to be mainly preserved. These results provide systematic evidence for the usefulness of FDG PET and dopaminergic SPECT imaging to characterize CBS.

Molecular imaging biomarkers for dementia with Lewy bodies: an update

BACKGROUND

Dementia with Lewy body (DLB) is considered to be the second most common form of neurodegenerative disorders after Alzheimer's disease (AD), affecting as many as 100,000 people in the UK and up to 1.3 million in the USA. However, nearly half of patients with DLB remain undiagnosed thus depriving many of them from an early and adequate treatment of their distressing symptoms. Accurate and early diagnosis of DLB is important for both patients and their caregivers, since the neuropsychiatric symptoms require specific management.

METHODS

In the current study, we review the most recent developments in the field of molecular nuclear imaging to diagnose DLB.

RESULTS

The review addresses, the neurotransmitter based (dopaminergic, cholinergic, and glutamatergic) nuclear imaging techniques, role of the autonomic dysfunction and its visualization in DLB with myocardial sympathetic imaging and vesicular catecholamine uptake, as well as the use of amyloid polypeptides and glial markers as molecular imaging probes in the clinical diagnosis of DLB.

CONCLUSIONS

Most of the above nuclear imaging methods are restricted to highly specialized clinical centers, and thus not applicable to a large number of patients requiring dementia (e.g. DLB) diagnosis in routine clinical setting. Validating them against more readily accessible peripheral biomarkers, e.g. CSF and blood biomarkers linked to the DLB process, may facilitate their use in wider clinical settings.

Dopamine transporter imaging for the diagnosis of dementia with Lewy bodies

BACKGROUND

Dementia with Lewy bodies (DLB) is a common cause of neurodegenerative dementia of old age. Its accurate recognition can be important in clinical management and is essential for the development of disease-modifying treatments. The current clinical diagnostic criteria are limited particularly by relatively poor sensitivity. Dopamine transporter (DAT) imaging using single-photon emission computed tomography (SPECT) is the most highly developed supplementary test for DLB, and is now incorporated as a suggestive feature in the consensus diagnostic criteria. However, there is uncertainty about its accuracy and its place in clinical practice. It is most commonly used in people who are already suspected of having DLB.

OBJECTIVES

We had two objectives in this review: (A) to estimate the accuracy of DAT imaging for the diagnosis of DLB in people with dementia in secondary care (specialist dementia services), and (B) to estimate the accuracy of DAT imaging for the diagnosis of DLB in people with dementia in secondary care who are already suspected of having DLB on the basis of a prior clinical work-up.

SEARCH METHODS

We searched MEDLINE (1946 to February 2013), Embase (1980 to February 2013), BIOSIS Previews (1926 to February 2013), PsycINFO (1806 to February 2013), CINAHL (1982 to February 2013), LILACS (February 2013) and Web of Science and Conference Proceedings (ISI Web of Science) (1945 to February 2013). Several of these sources contain conference abstracts. We also searched four specialised databases containing diagnostic reviews: Meta-analyses van Diagnostisch Onderzoek (MEDION; February 2013), Database of Abstracts of Reviews of Effects (DARE; February 2013), Health Technology Assessment Database (HTA; February 2013), and Aggressive Research Intelligence Facility (ARIF; February 2013). We checked reference lists of relevant studies and reviews for potential additional studies. Terms for electronic database searching were devised in conjunction with the team at the Cochrane Dementia and Cognitive Improvement Group.

STUDY DESIGN

We included test accuracy studies with delayed verification, diagnostic case-control studies, and two-gate studies with alternative diagnosis controls.

PARTICIPANTS

(A) participants with dementia in secondary care, (B) participants in secondary care meeting consensus clinical criteria (other than the DAT imaging criterion) for possible or probable DLB, or both.

INDEX TEST

SPECT or positron emission tomography (PET) imaging of brain dopamine transporters. Reference standard: Neuropathological diagnosis at autopsy.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies for inclusion and extracted data. We extracted results into a 2x2 table, showing the binary test results cross-classified with the binary reference standard. We used this data to calculate sensitivities, specificities, and their 95% confidence intervals. We used the QUADAS-2 tool plus some additional items to assess methodological quality.

MAIN RESULTS

We included one study that was applicable to our first objective (A). It reported data on 22 participants who met consensus clinical criteria for DLB or National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDA) criteria for Alzheimer's disease, or both (a two-gate design with alternative diagnosis controls). The index test was SPECT scanning using the ligand (123)I-FP-CIT. We considered the study to be at high risk of bias in the participant selection and index test domains (QUADAS-2). (123)I-FP-CIT SPECT analysed semiquantitatively had a sensitivity of 1.00 (95% confidence interval (CI) 0.66 to 1.00) and a specificity of 0.92 (95% CI 0.64 to 1.00) for the diagnosis of DLB (n = 22, 1 study). Analysed visually, the sensitivity was 0.86 (95% CI 0.42 to 1.00) and the specificity was 0.83 (95% CI 0.52 to 0.98) (n = 19, 1 study).We considered that the study also provided the best available data to address our second objective (B). At baseline, 15 participants were clinically suspected of having DLB. In this group, (123)I-FP-CIT SPECT scanning analysed semiquantitatively had a sensitivity of 1.00 (95% CI 0.63 to 1.00) and a specificity of 1.00 (95% CI 0.59 to 1.00) for the diagnosis of DLB (n = 15, 1 study). Analysed visually, accuracy in this group was lower with a sensitivity of 0.83 (95% CI 0.36 to 1.00) and a specificity of 0.71 (95% CI 0.29 to 0.96) (n = 13, 1 study).

AUTHORS' CONCLUSIONS

Only one study has used a neuropathological reference standard to assess the accuracy of DAT imaging for the diagnosis of DLB. The small size of the included study means that sensitivity and specificity estimates are imprecise. However, data from this study suggest that DAT imaging is more accurate than clinical diagnosis. Clinical diagnosis is therefore unsuitable to use as a reference standard for assessing the accuracy of DAT imaging.No studies using a neuropathological reference standard have directly addressed the common clinical scenario where the use of DAT imaging is considered as a diagnostic test in a person with possible DLB, or assessed the accuracy of DAT imaging in people with mild dementia. However, the data from the included study suggest that, where there is moderately severe dementia and a strong pre-existing suspicion of DLB (probable DLB), then a normal (123)I-FP-CIT SPECT scan may be an accurate means of excluding the diagnosis.Semiquantitative ratings of (123)I-FP-CIT SPECT scans appeared to be more accurate than visual ratings in all analyses.

Nigrostriatal dopamine terminal imaging with dopamine transporter SPECT: an update

This article gives an update on nigrostriatal dopamine terminal imaging, with emphasis on SPECT performed with the presynaptic dopamine transporter (DAT) ligand (123)I-FP-CIT. The paper covers the rational use of this technique in the diagnostic work-up of patients with known or suspected parkinsonian syndromes. In detail, it addresses the impact of the method for the proof or exclusion of neurodegenerative parkinsonism, for its early and preclinical diagnosis, and for the evaluation of disease progression. The importance of normal DAT binding for differentiating symptomatic parkinsonism and relevant tremor syndromes from neurodegeneration is highlighted. Particularly emphasized is the role of DAT SPECT for diagnosing Lewy body dementia and its separation from Alzheimer dementia. Finally, some remarks deal with the economic aspects of the use of these imaging techniques in the clinical setting.

Predictive value of dopamine transporter SPECT imaging with [¹²³I]PE2I in patients with subtle parkinsonian symptoms

PURPOSE

To examine the diagnostic sensitivity and specificity of dopamine transporter SPECT imaging with a highly dopamine transporter selective radioligand. The study included consecutively enrolled, drug-naive patients with an average short history of parkinsonian motor symptoms, referred for diagnostic scanning.

METHODS

The study group comprised 288 patients naive to antiparkinson treatment who were enrolled as they were admitted for a diagnostic SPECT scan with the radioligand [(123)I]-N-(3-iodoprop-2E-enyl)-2-β-carbomethoxy-3β-(4-methylphenyl)nortropane ((123)I-PE2I). After the diagnostic scanning, patients were followed clinically with an average follow-up of 19.7 ± 12.5 months.

RESULTS

A diagnosis could be clinically settled in 189 patients and among these patients, a dopamine transporter scan had a sensitivity of 88% and a specificity of 91% for discrimination between patients with and without striatal neurodegeneration. In cognitively impaired patients (Mini Mental State Examination <27) the specificity was 75% and the sensitivity 95%. A striatal anterior-posterior ratio (APR) of >2 differentiated between idiopathic Parkinson's disease and atypical parkinsonian syndromes with a specificity of 84% and a sensitivity of 63%.

CONCLUSION

In drug-naive patients with subtle clinical parkinsonian motor symptoms, dopamine transporter scan using (123)I-PE21 has a high sensitivity and specificity in distinguishing between patients with and without striatal neurodegeneration. The specificity is lower in patients who are also cognitively impaired. Calculation of the striatal APR can assist in differentiating between idiopathic Parkinson's disease and atypical parkinsonian syndromes.

Behavioural phenotype of APPC100.V717F transgenic mice over-expressing a mutant Abeta-bearing fragment is associated with reduced NMDA receptor density

The aim of this study was to characterize APPC100.V717F transgenic (TgC100.V717F) mice which over-express a mutant C100 fragment of the amyloid precursor protein. The mice were compared to TgC100 wild type mice (TgC100.WT) and non-transgenic controls at 4-9 and 16-22 months of age. TgC100.V717F mice showed behavioural hyperactivity, particularly at a younger age, as shown by increased numbers of elevated plus maze arm entries and Y-maze arm entries, enhanced baseline locomotor activity in the open field, and enhanced amphetamine-induced hyperlocomotion. This hyperactivity was less pronounced in TgC100.WT which only displayed significant differences to non-transgenic controls at a younger age for the number of Y-maze arm entries and baseline locomotor activity in the open field. In addition, TgC100.V717F mice, but not TgC100.WT, demonstrated cognitive deficits, as shown by reduced spontaneous alternation in the Y-maze and markedly reduced retention in a passive avoidance test. At an older age, TgC100.V717F mice showed enhanced startle and increased immobility time in the forced swim test. In the TgC100.V717F mice, but not TgC100.WT, the behavioural changes were paralleled by a significant reduction in the expression of hippocampal NMDA receptor subunits types 1 and 2A. Concomitantly, we detected axonal disruption and apoptosis in the hippocampus of TgC100.V717F mice. In conclusion, these data demonstrate that the mutant C100 fragment is an effector of biochemical and both cognitive and non-cognitive behaviours. These transgenic mice may be a model for the psychotic features associated with early Alzheimer's disease.

Differential diagnosis of dementia with Lewy Bodies and Alzheimer Disease using combined MR imaging and brain perfusion single-photon emission tomography

BACKGROUND AND PURPOSE

Diagnostic performance by MR imaging or by SPECT alone in discriminating DLB patients from AD patients has been estimated previously. However, the performance of a combination of MR imaging and SPECT has not yet been evaluated. Our aim was to evaluate the usefulness of combining MR imaging and SPECT to discriminate mild DLB from AD.

MATERIALS AND METHODS

Nineteen patients with mild DLB and 19 age- and cognitive decline-matched patients with mild AD underwent both SPECT and MR imaging. Hippocampal, occipital, and striatal volume and SPECT count ratios were compared. Linear discriminant and ROC analyses were performed by using the parameters of striatal volume and the occipital SPECT ratio.

RESULTS

The striatal volume ratio in the DLB group was significantly lower than that in the AD group. The occipital SPECT ratio in the DLB group was lower than that in the AD group. The mean area under the ROC curve from combined MR imaging and SPECT (AUC = 0.898) was higher than that from MR imaging (AUC = 0.679) or SPECT (AUC = 0.798) alone.

CONCLUSIONS

By combining MR imaging and SPECT, we were able to distinguish patients with mild DLB from those with AD with a high level of accuracy. Our findings suggest that combining MR imaging and SPECT modalities is a useful and practical approach for diagnostically differentiating DLB from AD.

Functional magnetic resonance in psychiatry

Neuroimaging is a powerful tool for the study of the neurobiological changes in psychiatric disorders. Functional magnetic resonance imaging (MRI) is a noninvasive method that assesses cortical activation by measuring changes in the local concentration of deoxyhemoglobin, which is paramagnetic and therefore can be detected using MRI. This method has been referred to as blood oxygen level-dependent imaging. This article discusses the application of functional MRI techniques, with emphasis on blood oxygen level-dependent imaging, to the study of psychiatric diseases. The first part of the article provides an overview of the contribution of functional MRI research to the current understanding of mood disorders, schizophrenia, and substance abuse. The last part reviews recent advances and highlights future directions for the use of the functional MRI technique for psychiatric research.