Additional Value of Early-Phase 18F-FP-CIT PET Image for Differential Diagnosis of Atypical Parkinsonism

Patterns of regional cerebral hypoperfusion in early Parkinson's disease: Clinical implications

INTRODUCTION

This study aimed to investigate whether regional cerebral perfusion patterns on early-phase 18F-FP-CIT PET scans, which is typically coupled to cerebral metabolism, predict the long-term prognosis of Parkinson's disease (PD).

METHODS

We enrolled 397 drug-naïve patients with early-stage PD who underwent dual-phase 18F-FP-CIT PET scans. After quantifying the early-phase 18F-FP-CIT PET images, cluster analysis was performed to delineate the PD subtypes according to the patterns of regional cerebral perfusion. We compared the risk of developing levodopa-induced dyskinesia (LID), wearing-off, freezing of gait (FOG), and dementia between the PD subtypes.

RESULTS

Cluster analysis classified patients into three subtypes: cluster 1 (relatively preserved cortical uptake; n = 175), cluster 2 (decreased uptake in the frontal, parietal, and temporal regions; n = 151), and cluster 3 (decreased uptake in more extensive regions, additionally involving the lateral occipital regions; n = 71). Cluster 1 was characterized by a younger age-of-onset, less severe motor deficits, less severely decreased 18F-FP-CIT binding in the caudate, and better cognitive performance. Cluster 3 was characterized by an older age-of-onset, more severe motor deficits, and poorer cognitive performance. Cluster 2 was intermediate between clusters 1 and 3. Cox regression analyses demonstrated that clusters 2 and 3 had a higher risk for dementia conversion than cluster 1, whereas the risk for developing LID, wearing-off, and FOG did not differ among the clusters.

CONCLUSION

The patterns of regional cerebral perfusion can provide information on long-term prognosis with regards to cognitive, but not motor aspects of patients with early-stage PD.

Dopamine Transporter SPECT with 12-Minute Scan Duration Using Multiple-Pinhole Collimators

This study evaluated the potential to reduce the scan duration in dopamine transporter (DAT) SPECT when using a second-generation multiple-pinhole (MPH) collimator designed for brain SPECT with improved count sensitivity and improved spatial resolution compared with parallel-hole and fanbeam collimators. Methods: The retrospective study included 640 consecutive clinical DAT SPECT studies that had been acquired in list mode with a triple-head SPECT system with MPH collimators and a 30-min net scan duration after injection of 181 ± 10 MBq of [123I]FP-CIT. Raw data corresponding to scan durations of 20, 15, 12, 8, 6, and 4 min were obtained by restricting the events to a proportionally reduced time interval of the list-mode data for each projection angle. SPECT images were reconstructed iteratively with the same parameter settings irrespective of scan duration. The resulting 5,120 SPECT images were assessed for a neurodegeneration-typical reduction in striatal signal by visual assessment, conventional specific binding ratio analysis, and a deep convolutional neural network trained on 30-min scans. Results: Regarding visual interpretation, image quality was considered diagnostic for all 640 patients down to a 12-min scan duration. The proportion of discrepant visual interpretations between 30 and 12 min (1.2%) was not larger than the proportion of discrepant visual interpretations between 2 reading sessions of the same reader at a 30-min scan duration (1.5%). Agreement with the putamen specific binding ratio from the 30-min images was better than expected for 5% test-retest variability down to a 10-min scan duration. A relevant change in convolutional neural network-based automatic classification was observed at a 6-min scan duration or less. Conclusion: The triple-head SPECT system with MPH collimators allows reliable DAT SPECT after administration of about 180 MBq of [123I]FP-CIT with a 12-min scan duration.

Dopamine transporter positron emission tomography in patients with Alzheimer's disease with Lewy body disease features

In 36 normal controls (NC), 37 patients with Alzheimer's disease (AD) without parkinsonism (ADP-), 31 AD with parkinsonism (ADP+), and 40 AD with dementia with Lewy bodies (ADDLB), dual-phase dopamine transporter (DAT) positron emission tomography (PET) were performed to evaluate the diagnostic performance of DAT and early-to-delayed uptake ratios (E/Ds) in the anterior caudate (AC), posterior caudate (PC), anterior putamen (AP), posterior putamen (PP), and substantia nigra (SN) to differentiate ADP+/ADDLB from NC, and their effects on parkinsonism and cognition. DAT-SN and E/D-PP showed higher accuracies to differentiate ADP+/ADDLB from NC than DAT-PP. Among AD patients, lower DAT in the putamen and PC and higher E/Ds in the striatum were associated with severe parkinsonism, while higher E/Ds in the putamen, PC, and SN were associated with executive dysfunction. Our results suggest that decreased DAT-SN and increased E/D-PP could be biomarkers differentiating ADP+/ADDLB from pure AD and controls. Meanwhile, increased E/Ds in the putamen could reflect the severity of DLB presenting with parkinsonism and executive dysfunction among AD patients.

The Role of Dual-Phase 18 F-FP-CIT PET to Early Diagnosis of Corticobasal Syndrome

BACKGROUND

Corticobasal syndrome (CBS) is a neurodegeneration characterized by asymmetric parkinsonism, dystonia, myoclonus, and apraxia. In the early stage, CBS presents with asymmetric parkinsonism and cortical symptoms (apraxia and alien hand), and neuroimaging finding is often vague, making early clinical differentiation from idiopathic Parkinson disease (IPD) challenging. This study was performed to delineate the specific patterns of cortical hypoperfusion, dopamine transporter (DAT) uptake using dual-phase FP-CIT PET in discriminating between CBS and IPD at early stage.

PATIENTS AND METHODS

The study enrolled clinically diagnosed CBS (n = 11) and IPD (n = 22) patients (age and sex matched). All participants underwent dual-phase 18 F-FP-CIT PET, and regional SUV ratio (SUVR) was obtained by semiquantitative analysis. The early perfusion imaging and DAT imaging were compared between groups.

RESULTS

The regional SUVRs (early phase) of the frontal lobe, thalamus, cingulate, and caudate were significantly lower in patients with CBS, whereas the SUVR of occipital lobe was lower in the IPD group. The CBS group exhibited more prominent asymmetry than the IPD group, particularly in the perirolandic area, superior frontal gyrus, and anterior parietal lobe in early phase PET. Striatal DAT uptake (delayed phase) revealed that the caudate showed lower SUVR and prominent asymmetry in the CBS group, and the caudate-to-putamen ratio (CP ratio) was significantly lower in CBS patients ( P < 0.001). Among the parameters (early and delayed), the CP ratio in DAT exhibited the most powerful discriminative power from receiver operating characteristic curve comparison (area under curve = 0.983).

CONCLUSIONS

This study demonstrated that the dual-phase FP-CIT PET is useful in differentiating CBS and IPD in the early stage of the disease, and a lower CP ratio of DAT imaging is highly informative for distinguishing between corticobasal degeneration and IPD.

Is the cingulate island sign a marker for early dementia conversion in Parkinson's disease?

BACKGROUND

To investigate whether the cingulate island sign (CIS) ratio (i.e., the ratio of regional uptake in the posterior cingulate cortex relative to the precuneus and cuneus on cerebral perfusion scans) is associated with early dementia conversion in Parkinson's disease (PD).

METHODS

We enrolled 226 patients with newly diagnosed PD and 48 healthy controls who underwent dual-phase 18 F-FP-CIT PET scans. Patients with PD were classified into three groups according to the CIS ratio on early-phase 18 F-FP-CIT PET images: a PD group with CIS or high CIS ratios (PD-CIS; n = 96), a PD group with inverse CIS or low CIS ratios (PD-iCIS; n = 40), and a PD group consisting of the remaining patients with normal CIS ratios (PD-nCIS; n = 90). We compared the risk of dementia conversion within a 5-year time point between the groups.

RESULTS

There were no significant differences in age, sex, education, or baseline cognitive function between the PD groups. The PD-CIS group had higher Unified Parkinson's Disease Rating Scale (UPDRS) motor scores and more severely decreased dopamine transporter availability in the putamen. The PD-iCIS group had a smaller hippocampal volume compared with the other groups. The risk of dementia conversion in the PD-CIS group did not differ from that in the PD-iCIS and PD-nCIS groups. Meanwhile, the PD-iCIS group had a higher risk of dementia conversion than the PD-nCIS group.

CONCLUSION

The results of this study suggest that inverse CIS, rather than CIS, is relevant to early dementia conversion in patients with PD.

Dual-phase 18 F-FP-CIT positron emission tomography and cardiac 123 I-MIBG scintigraphy of Parkinson's disease patients with GBA mutations: evidence of the body-first type?

BACKGROUND AND PURPOSE

Parkinson's disease (PD) with glucocerebrosidase (GBA) gene mutation (GBA-PD) is known to show more rapid clinical progression than sporadic PD without GBA mutation (sPD). This study was performed to delineate the specific patterns of cortical hypoperfusion, dopamine transporter uptake and cardiac meta-iodobenzylguanidine (MIBG) uptake of GBA-PD in comparison to sPD.

METHODS

Through next-generation sequencing analysis targeting 41 genes, a total of 16 GBA-PD and 24 sPD patients (sex, age matched) were enrolled in the study, and the clinical, dual-phase [¹⁸ F]-N-(3-fluoropropyl)-2β-carboxymethoxy-3β-(4-iodophenyl) nortropane (^{1 8} F-FP-CIT) positron emission tomography (PET) and cardiac ¹²³ I-MIBG scintigraphy results were compared between the two groups.

RESULTS

The GBA-PD group had higher rates of rapid eye movement sleep behavior disorder, orthostatic hypotension and neuropsychiatric symptoms than the sPD group. Early-phase ¹⁸ F-FP-CIT PET showed significantly lower standard uptake value ratio on bilateral posterior parietal cortex (0.94 ± 0.05 vs. 1.02 ± 0.04, p = 0.011) and part of the occipital cortex (p < 0.05) in the GBA-PD group than the sPD group. In striatal dopamine transporter uptake, the regional standard uptake value ratio, asymmetry index and caudate-to-putamen ratio were similar between the two groups. The GBA-PD group had a lower heart-to-mediastinum uptake ratio in ¹²³ I-MIBG scintigraphy than the sPD group.

CONCLUSIONS

The GBA-PD patients showed decreased regional perfusion in the bilateral posterior parietal and occipital cortex. Cardiac sympathetic denervation and non-motor symptoms (orthostatic hypotension, rapid eye movement sleep behavior disorder) were more common in GBA-PD than sPD. These findings suggest that GBA-PD patients have more widespread peripheral (extranigral) α-synuclein accumulation, representing a body-first PD subtype.

Dual phase 18F-FP CIT PET and 99mTc- ECD SPECT findings of Huntington's disease

Fluorine-18 N-3-fluoropropyl-2-beta-carboxymethoxy-3-beta-(4-iodophenyl) nortropane (18F- FP CIT) has been used for the differential diagnosis of atypical parkinsonian disorders, and Technetium 99m ethyl cysteinate dimer (99mTc- ECD) has been used for evaluation of cerebral blood flow. A 60-year-old female with a history of Huntington's disease (HD) with full mutation of cytosine-adenine-guanine (GAG) 18/43 repeats underwent early and late 18F- FP CIT positron emission tomography/computed tomography (PET/CT) and 99mTc- ECD single-photon emission computed tomography (SPECT). The 18F-FP CIT PET/CT showed decreased uptake in both basal ganglia, both frontal and parietotemporal lobes at early images, and decreased presynaptic dopamine transporter (DAT) binding in both ventral & posterior putamen at late images. 99mTc- ECD SPECT showed decreased perfusion in both basal ganglia, both frontal and temporal lobes. Early 18F- FP CIT PET/CT and 99mTc- ECD SPECT images showed similar findings in Huntington's disease.

Diagnostic Performance for Differential Diagnosis of Atypical Parkinsonian Syndromes from Parkinson’s Disease Using Quantitative Indices of 18F-FP-CIT PET/CT

We are aimed to evaluate the diagnostic performances of quantitative indices obtained from dual-phase ¹⁸F-FP-CIT PET/CT for differential diagnosis of atypical parkinsonian syndromes (APS) from Parkinson’s disease (PD). We analyzed 172 subjects, including 105 non-Parkinsonism, 26 PD, 8 PSP, 1 CBD, 8 MSA-P, 9 MSA-C, and 15 DLB retrospectively. Two sequential PET/CT scans were acquired at 5 min and 3 h. We compared subregional binding potentials, putamen-to-caudate nucleus ratio of the binding potential, asymmetry index, and degree of washout. To differentiate APS, all BPs in both early and late phases (except late BPbrainstem) and all factors of the percent change except for putamen in APS significantly differed from PD. When a cut-off for early BPcerebellum was set as 0.79, the sensitivity, specificity (SP), positive predictive value (PPV), negative predictive value (NPV), and accuracy for differentiating APS 73.2%, 91.7%, 93.8%, 66.7%, and 80.0%. The early BPcerebellum showed significantly greater SP and PPV than the late quantitative indices. Combined criteria regarding both early and late indices exhibited only greater NPV. The quantitative indices showed high diagnostic performances in differentiating APS from PD. Our findings provide the dual-phase ¹⁸F-FP-CIT PET/CT would be useful for differentiating APS from PD.

60 Years of Achievements by KSNM in Neuroimaging Research

Nuclear medicine neuroimaging is able to show functional and molecular biologic abnormalities in various neuropsychiatric diseases. Therefore, it has played important roles in the clinical diagnosis and in research on the normal and pathological states of the brain. More than 400 outstanding studies have been conducted by Korean researchers over the past 60 years. In the 1990s, when multiheaded single-photon emission computed tomography (SPECT) scanners were first introduced in South Korea, stroke research using brain perfusion SPECT was conducted. With the spread of positron emission tomography (PET) scanners in the 2000s, research on the clinical usefulness of PET and the evaluation of pathophysiology in various diseases such as epilepsy, brain tumors, degenerative brain diseases, and other neuropsychiatric diseases were actively conducted using [¹⁸F]FDG and various neuroreceptor tracers. In the 2010s, with the clinical application of new radiopharmaceuticals for amyloid and tau imaging, research demonstrating the clinical usefulness of PET imaging and the pathophysiology of dementia has increased rapidly. It is expected that the role of nuclear medicine will expand with the development of new radiopharmaceuticals and analysis technologies, along with the application of artificial intelligence for early and differential diagnosis, and the development of therapeutic agents for degenerative brain diseases.

Comparison of perfusion 18F-FP-CIT PET and 99mTc-ECD SPECT in parkinsonian disorders

Early and accurate identification of various conditions that can cause parkinsonian symptoms is important for determining treatment policies. Currently dopamine transporter (DAT) imaging using FP-CIT, glucose metabolism imaging using fluorodeoxyglucose, cerebral blood flow image using ethyl cysteinate dimer (ECD), and others are used for differentiation. However, the use of multiple modalities is inconvenient and costly. In the present retrospective study, we evaluated the correlation between regional brain uptake ratios (URs) in perfusion FP-CIT PET and ECD SPECT images.Twenty patients with Parkinson's symptoms underwent perfusion DAT positron emission tomography (18F-FP-CIT PET/CT) and cerebral blood flow tomography (99mTc-ECD SPECT) within a 2-week period. Perfusion 18F-FP-CIT PET/CT and 99mTc-ECD SPECT URs of 19 brain regions (bilateral frontal, temporal, parietal and occipital lobes, bilateral caudate nucleus, bilateral putamen, bilateral insula, bilateral cingulate gyrus, bilateral thalamus, and brainstem) were directly compared and correlations were analyzed.Average 18F-FP-CIT PET/CT regional perfusion URs were higher than 99mTc-ECD SPECT URs. Uptake ratios were well correlated in all 19 regions (except right putamen), and especially in dopamine poor regions (cerebral cortex). In left putamen, URs were significantly correlated, but the correlation coefficient was lower than those of other regions.A single tracer dual phase N-3-fluoropropyl-2-beta-carboxymethoxy-3-beta-(4-iodophenyl) nortropane test seems to be helpful for differential diagnosis of parkinsonian disorders. Large-scale, longitudinal studies on complementary diseases with parkinsonian patterns are required to investigate differences in correlations between perfusion 18F-FP-CIT PET/CT and 99mTc-ECD SPECT over time.

Diagnostic accuracy of dual-phase 18F-FP-CIT PET imaging for detection and differential diagnosis of Parkinsonism

Delayed phase 18F-FP-CIT PET (dCIT) can assess the striatal dopamine transporter binding to detect degenerative parkinsonism (DP). Early phase 18F-FP-CIT (eCIT) can assess the regional brain activity for differential diagnosis among parkinsonism similar with 18F-FDG PET. We evaluated the diagnostic performance of dual phase 18F-FP-CIT PET (dual CIT) and 18F-FDG PET compared with clinical diagnosis in 141 subjects [36 with idiopathic Parkinson's disease (IPD), 77 with multiple system atrophy (MSA), 18 with progressive supranuclear palsy (PSP), and 10 with non-DP)]. Visual assessment of eCIT, dCIT, dual CIT, 18F-FDG and 18F-FDG PET with dCIT was in agreement with the clinical diagnosis in 61.7%, 69.5%, 95.7%, 81.6%, and 97.2% of cases, respectively. ECIT showed about 90% concordance with non-DP and MSA, and 8.3% and 27.8% with IPD and PSP, respectively. DCIT showed ≥ 88% concordance with non-DP, IPD, and PSP, and 49.4% concordance with MSA. Dual CIT showed ≥ 90% concordance in all groups. 18F-FDG PET showed ≥ 90% concordance with non-DP, MSA, and PSP, but only 33.3% concordance with IPD. The combination of 18F-FDG and dCIT yielded ≥ 90% concordance in all groups. Dual CIT may represent a powerful alternative to the combination of 18F-FDG PET and dCIT for differential diagnosis of parkinsonian disorders.

Early-phase 18F-FP-CIT and 18F-flutemetamol PET were significantly correlated

Little is known about whether early-phase PET images of ¹⁸F-FP-CIT match those of amyloid PET. Here, we compared early-phase ¹⁸F-FP-CIT and ¹⁸F-flutemetamol PET images in patients who underwent both within a 1-month interval. The SUVR on early-phase ¹⁸F-FP-CIT PET (median, 0.86) was significantly lower than that of ¹⁸F-flutemetamol PET (median, 0.91, p < 0.001) for total brain regions including all cerebral lobes and central structures. This significant difference persisted for each brain region except central structures (p = 0.232). The SUVR of total brain regions obtained from early ¹⁸F-FP-CIT PET showed a very strong correlation with that of ¹⁸F-flutemetamol PET (rho = 0.80, p < 0.001). Among the kinetic parameters, only R1 showed a statistically significant correlation between the two techniques for all brain regions (rho = 0.89, p < 0.001). R1 from ¹⁸F-FP-CIT (median, 0.77) was significantly lower in all areas of the brain compared to R1 from ¹⁸F-flutemetamol PET (median, 0.81, p < 0.001).¹⁸F-FP-CIT demonstrated lower uptake in cortical brain regions than ¹⁸F-flutemetamol on early-phase PET. However, both early-phase PETs demonstrated significant correlation of uptake.

Dynamic 18F-FPCIT PET: Quantification of Parkinson's disease metabolic networks and nigrostriatal dopaminergic dysfunction in a single imaging session

Previous multi-center imaging studies with 18F-FDG PET have established the presence of Parkinson's disease motor- and cognition-related metabolic patterns termed PDRP and PDCP in patients with this disorder. Given that in PD cerebral perfusion and glucose metabolism are typically coupled in the absence of medication, we determined whether subject expression of these disease networks can be quantified in early-phase images from dynamic 18F-FPCIT PET scans acquired to assess striatal dopamine transporter (DAT) binding. Methods: We studied a cohort of early-stage PD patients and age-matched healthy control subjects who underwent 18F-FPCIT at baseline; scans were repeated 4 years later in a smaller subset of patients. The early 18F-FPCIT frames, which reflect cerebral perfusion, were used to compute PDRP and PDCP expression (subject scores) in each subject, and compared to analogous measures computed based on 18F-FDG PET scan when additionally available. The late 18F-FPCIT frames were used to measure caudate and putamen DAT binding in the same individuals. Results: PDRP subject scores from early-phase 18F-FPCIT and 18F-FDG scans were elevated and striatal DAT binding reduced in PD versus healthy subjects. The PDRP scores from 18F-FPCIT correlated with clinical motor ratings, disease duration, and with corresponding measures from 18F-FDG PET. In addition to correlating with disease duration and analogous 18F-FDG PET values, PDCP scores correlated with DAT binding in the caudate/anterior putamen. PDRP and PDCP subject scores using either method rose over 4 years whereas striatal DAT binding declined over the same time period. Conclusion: Early-phase images obtained with 18F-FPCIT PET can provide an alternative to 18F-FDG PET for PD network quantification. This technique therefore allows PDRP/PDCP expression and caudate/putamen DAT binding to be evaluated with a single tracer in one scanning session.

FUNCTIONAL NEUROMARKERS IN PARKINSON’S DISEASE (PD)

New neurotechnologies which help to study not only the structure but also brain work, especially in milliseconds, allow for a more accurate diagnosis of a given disease entity. The aim of our study was to characterize the functional neuromarkers, including a new neuromarker, that is high rolandic beta, in Parkinson’s disease (PD). A 76-year-old male patient, a university professor, a widower, in an intimate relationship with a beloved partner, was tested in the Reintegration and Training Center of the Polish Society of Neuropsychology. Five years earlier (when he was 71 years old), following long-term stress, he had had a transient ischemic attack (TIA). In the following years he experienced two neurological episodes, and was diagnosed, on the basis of MRI findings and clinical symptoms, with vascular (multi-infarct) Parkinsonism. A sudden deterioration in his functioning, including hand tremors at rest, bradykinesia (motor slowdown), asymmetrical gait difficulties, postural instability, and falls typical for PD, as well as MRI finding (the appearance of ‘a swallow tail ’ on the left side, and the lack on the right of the substantia nigra within the midbrain) was the cause of further differential diagnosis. He was assessed using the HBI methodology (Kropotov 2016; Pąchalska, Kaczmarek, Kropotov 2014). EEG was recorded from 19 scalp sites, in resting state conditions, with eyes open and eyes closed, and during the cued GO/NOGO tasks with animal/plants as GO/NOGO stimuli. The electrodes were applied according to the International 10-20 system. The EEG was recorded referentially to linked ears, allowing for a computational re-referencing of the data (remontaging). Event related potentials (ERPs) were used to assess the functional changes manifested by the patient. To compare our patient with healthy controls we used the normative Human Brain Index (HBI), a database obtained through joint research by Swiss, Norwegian, Polish and Russian neuroscientists (Kropotov 2018). This database included behavioral parameters and ERP measures in 6 different neuropsychological tasks for 1000 healthy subjects. What is striking, no signs of cognitive dysfunction was found; however observed were an asymmetrical frontal lobe alpha (a neuromarker of depression) and excessive Rolandic beta (a neuromarker of Parkinson’s disease). We will discuss the results on the basis of recent subject literature findings, including the personal factors that might influenced the process of the diagnosis and treatment of this patient, ones which should be also taken into account in any differential diagnosis. The obtained results show the importance of using HBI methodology in clinical practice. Physicians involved in the diagnosis and treatment of those with progressive ambulatory impairment and an abnormal white matter (WM) signal on neuroimaging, should when formulating any differential diagnosis consider the use of this approach. ------------------------------------------------------------------------------------------------------------------------------------

Spatial Normalization Using Early-Phase [18F]FP-CIT PET for Quantification of Striatal Dopamine Transporter Binding

Purpose

The precise quantification of dopamine transporter (DAT) density on N-(3-[¹⁸F]Fluoropropyl)-2β-carbomethoxy-3β-(4-iodophenyl) nortropane positron emission tomography ([¹⁸F]FP-CIT PET) imaging is crucial to measure the degree of striatal DAT loss in patients with parkinsonism. The quantitative analysis requires a spatial normalization process based on a template brain. Since the spatial normalization method based on a delayed-phase PET has limited performance, we suggest an early-phase PET-based method and compared its accuracy, referring to the MRI-based approach as a gold standard.

Methods

A total of 39 referred patients from the movement disorder clinic who underwent dual-phase [¹⁸F]FP-CIT PET and took MRI within 1 year were retrospectively analyzed. The three spatial normalization methods were applied for quantification of [¹⁸F]FP-CIT PET-MRI-based anatomical normalization, PET template-based method based on delayed PET, and that based on early PET. The striatal binding ratios (BRs) were compared, and voxelwise paired t tests were implemented between different methods.

Results

The early image-based normalization showed concordant patterns of putaminal [¹⁸F]FP-CIT binding with an MRI-based method. The BRs of the putamen from the MRI-based approach showed higher agreement with early image- than delayed image-based method as presented by Bland-Altman plots and intraclass correlation coefficients (early image-based, 0.980; delayed image-based, 0.895). The voxelwise test exhibited a smaller volume of significantly different counts in putamen between brains processed by early image and MRI compared to that between delayed image and MRI.

Conclusion

The early-phase [¹⁸F]FP-CIT PET can be utilized for spatial normalization of delayed PET image when the MRI image is unavailable and presents better performance than the delayed template-based method in quantitation of putaminal binding ratio.

Dopamine transporter imaging in neurodegenerative movement disorders: PET vs. SPECT

Purpose

The dopamine transporter (DAT) serves as biomarker for parkinsonian syndromes. DAT can be measured in vivo with single-photon emission computed tomography (SPECT) and positron emission tomography (PET). DAT-SPECT is the current clinical molecular imaging standard. However, PET has advantages over SPECT measurements, and PET radioligands with the necessary properties for clinical applications are on the rise. Therefore, it is time to review the role of DAT imaging with SPECT compared to PET.

Methods

PubMed and Web of Science were searched for relevant literature of the previous 10 years. Four topics for comparison were used: diagnostic accuracy, quantitative accuracy, logistics, and flexibility.

Results

There are a few studies directly comparing DAT-PET and DAT-SPECT. PET and SPECT both perform well in discriminating neurodegenerative from non-neurodegenerative parkinsonism. Clinical DAT-PET imaging seems feasible only recently, thanks to simplified DAT assessments and better availability of PET radioligands and systems. The higher resolution of PET makes more comprehensive assessments of disease progression in the basal ganglia possible. Additionally, it has the possibility of multimodal target assessment.

Conclusion

DAT-SPECT is established for differentiating degenerative from non-degenerative parkinsonism. For further differentiation within neurodegenerative Parkinsonian syndromes, DAT-PET has essential benefits. Nowadays, because of wider availability of PET systems and radioligand production centers, and the possibility to use simplified quantification methods, DAT-PET imaging is feasible for clinical use. Therefore, DAT-PET needs to be considered for a more active role in the clinic to take a step forward to a more comprehensive understanding and assessment of Parkinson’s disease.

Reproducible metabolic topographies associated with multiple system atrophy: Network and regional analyses in Chinese and American patient cohorts

•

This study produced reliable metabolic brain networks for multiple system atrophy.

•

Network scores discriminated this disorder from other major forms of Parkinsonism.

•

Network scores correlated with clinical stages and motor symptoms in this disorder.

•

The network was highly reproducible across Chinese and American patient cohorts.

•

Network scores provided a clinically useful biomarker in a multi-center setting.

Purpose

Multiple system atrophy (MSA) is an atypical parkinsonian syndrome and often difficult to discriminate clinically from progressive supranuclear palsy (PSP) and Parkinson's disease (PD) in early stages. Although a characteristic metabolic brain network has been reported for MSA, it is unknown whether this network can provide a clinically useful biomarker in different centers. This study was aimed to identify and cross-validate MSA-related brain network and assess its ability for differential diagnosis and clinical correlations in Chinese and American patient cohorts.

Methods

We included ¹⁸F-FDG PET scans retrospectively from 128 clinically diagnosed parkinsonian patients (34 MSA, 34 PSP and 60 PD) and 40 normal subjects in China and in the USA. Using PET images from 20 moderate-stage MSA patients of parkinsonian subtype and 20 normal subjects in both centers, we reproduced MSA-related pattern (MSAPRP) of spatial covariance and estimated its reliability. MSAPRP scores were evaluated in assessing differential diagnosis among moderate- and early-stage MSA, PSP or PD patients and clinical correlations with disease severity. Regional metabolic differences were detected using statistical parameter mapping analysis. MSA-related network and regional topographies of metabolic abnormality were cross-validated between the Chinese and American cohorts.

Results

We generated a highly reliable MSAPRP characterized by decreased loading in inferior frontal cortex, striatum and cerebellum, and increased loading in sensorimotor, parietal and occipital cortices. MSAPRP scores discriminated between normal, MSA, PSP and PD subjects and correlated with standardized ratings of clinical stages and motor symptoms in MSA. High similarities in MSAPRPs, network scores and corresponding maps of metabolic abnormality were observed between two different cohorts.

Conclusion

We have demonstrated reproducible metabolic topographies associated with MSA at both network and regional levels in two independent patient cohorts. Moreover, MSAPRP scores are sensitive for evaluating disease discrimination and clinical correlates. This study supports differential diagnosis of MSA regardless of different patient populations, PET scanners and imaging protocols.

Imaging of dopamine transporters in Parkinson disease: a meta-analysis of 18 F/123 I-FP-CIT studies

OBJECTIVE

¹⁸ F-FP-CIT and ¹²³ I-FP-CIT are widely used radiotracers in molecular imaging for Parkinson's disease (PD) diagnosis. Compared with ¹²³ I-FP-CIT, ¹⁸ F-FP-CIT has superior tracer kinetics. We aimed to conduct a meta-analysis to assess the efficacy of using ¹⁸ F-FP-CIT positron emission tomography (PET) and ¹²³ I-FP-CIT single-photon emission computed tomography (SPECT) of dopamine transporters in patients with PD in order to provide evidence for clinical decision-making.

METHODS

We searched the PubMed, Embase, Wanfang Data, and China National Knowledge Infrastructure databases to identify the relevant studies from the time of inception of the databases to 30 April 2020. We identified six PET studies, including 779 patients with PD and 124 healthy controls, which met the inclusion criteria. Twenty-seven SPECT studies with 1244 PD patients and 859 controls were also included in this meta-analysis.

RESULTS

Overall effect-size analysis indicated that patients with PD showed significantly reduced ¹⁸ F-FP-CIT uptake in three brain regions [caudate nucleus: standardized mean difference (SMD) = -1.71, Z = -3.31, P = 0.0009; anterior putamen: SMD = -3.71, Z = -6.26, P < 0.0001; and posterior putamen: SMD = -5.49, Z = -5.97, P < 0.0001]. Significant decreases of ¹²³ I-FP-CIT uptake were also observed in the caudate (SMD = -2.31, Z = -11.49, P < 0.0001) and putamen (SMD = -3.25, Z = -14.79, P < 0.0001).

INTERPRETATION

In conclusion, our findings indicate that both ¹⁸ F-FP-CIT PET and ¹²³ I-FP-CIT SPECT imaging of dopamine transporters can provide viable biomarkers for early PD diagnosis.

Dysautonomia Is Linked to Striatal Dopamine Deficits and Regional Cerebral Perfusion in Early Parkinson Disease

PURPOSE

The aim of this study was to investigate the association between autonomic dysfunction and striatal dopamine depletion or metabolic changes in de novo Parkinson disease (PD).

METHODS

Based on the Composite Autonomic Severity Score (CASS), patients with de novo PD were classified into PD with (PD-AUT+) and without autonomic dysfunction (PD-AUT-) groups. We compared the dopamine transporter (DAT) availability in the striatum by quantitatively measuring F-FP-CIT PET between both groups. We also assessed the association between DAT availability and the CASS. In addition, we compared regional uptake in early-phase images of F-FP-CIT PET as well as cortical thickness between the PD-AUT+ and PD-AUT- groups.

RESULTS

The PD-AUT+ group had significantly lower DAT availability in all striatal subregions than did the PD-AUT- group. The total CASS was significantly correlated with DAT availability in all striatal subregions. In addition, the subscores of the adrenergic component were correlated with DAT availability in all striatal subregions. The subscores of the cardiovagal component were negatively correlated with DAT availability in the caudate and ventral striatum. In early-phase F-FP-CIT PET, the PD-AUT+ group exhibited decreased regional perfusion in the parieto-occipital areas and increased regional perfusion in the pallidothalamic, pontocerebellar, inferior frontal, and primary motor areas compared with the PD-AUT- group. There were no regions of different cortical thickness between the PD groups.

CONCLUSIONS

The present study revealed that autonomic dysfunction is closely linked to striatal dopamine depletion and prominent PD-related perfusion patterns in de novo PD, suggesting a greater pathological burden in patients with dysautonomia.

Correlation of Early-Phase F-18 Florapronal PET with F-18 FDG PET in Alzheimer's Disease and Normal Brain

Purpose

F-18 florapronol (FPN) is the commercially recognized beta-amyloid positron emission tomography (PET) radiotracer in Korea. This study compared the early F-18 florapronol PET with F-18 fluorodeoxyglucose (FDG) PET between healthy controls (HC) and Alzheimer's dementia (AD) patients.

Methods

A total of 29 subjects (15 HC and 14 AD subjects) underwent F-18 FPN PET and F-18 FDG PET. F-18 FDG PET image was acquired from 30 to 60 min and F-18 FPN PET for 0 to 10 min. F-18 FPN and F-18 FDG images were spatially normalized with transformation matrices obtained from individual CT images and standardized uptake value ration (SUVR) from cerebellum area, and the global mean was calculated using PMOD 3.6. Pearson's correlation coefficients between F-18 FDG and early F-18 FPN for predefined cortical brain regions were calculated.

Results

We compared the F-18 FDG and F-18 FPN for SUVR of a specific region in global mean normalization and cerebellum normalization, and most of the correlation coefficient was higher in global mean normalization. In global mean normalization, the correlation coefficient for SUVR of HC was higher than that of AD in all brain regions.

Conclusions

Early F-18 FPN study can be used as a proxy marker for the F-18 FDG PET.

Dual-Phase 18F-FP-CIT PET in Corticobasal Syndrome

Corticobasal syndrome is the most common phenotype of corticobasal degeneration (CBD). F-FP-CIT PET and MRI are not helpful in distinguishing CBD from idiopathic Parkinson disease. Dual-phase F-FP-CIT PET is a recently developed imaging that shows regional cerebral perfusion in the early phase and dopamine transporter density in the late phase. We investigated the usefulness of dual-phase F-FP-CIT PET imaging in 3 patients with corticobasal syndrome. This image highlights that the early phases of F-FP-CIT PET may reflect regional cerebral perfusion with a pattern very similar to that of regional glucose metabolism in CBD.

Multimodal correlation of dynamic [18F]-AV-1451 perfusion PET and neuronal hypometabolism in [18F]-FDG PET

PURPOSE

Cerebral glucose metabolism measured with [18F]-FDG PET is a well established marker of neuronal dysfunction in neurodegeneration. The tau-protein tracer [18F]-AV-1451 PET is currently under evaluation and shows promising results. Here, we assess the feasibility of early perfusion imaging with AV-1451 as a substite for FDG PET in assessing neuronal injury.

METHODS

Twenty patients with suspected neurodegeneration underwent FDG and early phase AV-1451 PET imaging. Ten one-minute timeframes were acquired after application of 200 MBq AV-1451. FDG images were acquired on a different date according to clinical protocol. Early AV-1451 timeframes were coregistered to individual FDG-scans and spatially normalized. Voxel-wise intermodal correlations were calculated on within-subject level for every possible time window. The window with highest pooled correlation was considered optimal. Z-transformed deviation maps (ZMs) were created from both FDG and early AV-1451 images, comparing against FDG images of healthy controls.

RESULTS

Regional patterns and extent of perfusion deficits were highly comparable to metabolic deficits. Best results were observed in a time window from 60 to 360 s (r = 0.86). Correlation strength ranged from r = 0.96 (subcortical gray matter) to 0.83 (frontal lobe) in regional analysis. ZMs of early AV-1451 and FDG images were highly similar.

CONCLUSION

Perfusion imaging with AV-1451 is a valid biomarker for assessment of neuronal dysfunction in neurodegenerative diseases. Radiation exposure and complexity of the diagnostic workup could be reduced significantly by routine acquisition of early AV-1451 images, sparing additional FDG PET.