Comparison of FP-CIT SPECT with F-DOPA PET in patients with de novo and advanced Parkinson’s disease

Dopamine Synthesis in the Nigrostriatal Dopaminergic System in Patients at Risk of Developing Parkinson's Disease at the Prodromal Stage

Parkinson's disease (PD) is diagnosed by the onset of motor symptoms and treated long after its onset. Therefore, the development of the early diagnosis of PD is a priority for neurology. Advanced methodologies for this include (1) searching for patients at risk of developing prodromal PD based on premotor symptoms; (2) searching for changes in the body fluids in these patients as diagnostic biomarkers; (3) verifying the diagnosis of prodromal PD and diagnostic-value biomarkers using positron emission tomography (PET); (4) anticipating the development of motor symptoms. According to our data, the majority of patients (n = 14) at risk of developing PD selected in our previous study show pronounced interhemispheric asymmetry in the incorporation of 18F-DOPA into dopamine synthesis in the striatum. This was assessed for the caudate nucleus and putamen separately using the specific binding coefficient, asymmetry index, and putamen/caudate nucleus ratio. Interhemispheric asymmetry in the incorporation of 18F-DOPA into the striatum provides strong evidence for its dopaminergic denervation and the diagnostic value of previously identified blood biomarkers. Of the 17 patients at risk of developing prodromal PD studied using PET, 3 patients developed motor symptoms within a year. Thus, our study shows the promise of using the described methodology for the development of early diagnosis of PD.

Practical Overview of 123I-Ioflupane Imaging in Parkinsonian Syndromes

Parkinsonian syndromes are a heterogeneous group of progressive neurodegenerative disorders involving the nigrostriatal dopaminergic pathway and are characterized by a wide spectrum of motor and nonmotor symptoms. These syndromes are quite common and can profoundly impact the lives of patients and their families. In addition to classic Parkinson disease, parkinsonian syndromes include multiple additional disorders known collectively as Parkinson-plus syndromes or atypical parkinsonism. These are characterized by the classic parkinsonian motor symptoms with additional distinguishing clinical features. Dopamine transporter SPECT has been developed as a diagnostic tool to assess the levels of dopamine transporters in the striatum. This imaging assessment, which uses iodine 123 (123I) ioflupane, can be useful to differentiate parkinsonian syndromes caused by nigrostriatal degeneration from other clinical mimics such as essential tremor or psychogenic tremor. Dopamine transporter imaging plays a crucial role in diagnosing parkinsonian syndromes, particularly in patients who do not clearly fulfill the clinical criteria for diagnosis. Diagnostic clarification can allow early treatment in appropriate patients and avoid misdiagnosis. At present, only the qualitative interpretation of dopamine transporter SPECT is approved by the U.S. Food and Drug Administration, but quantitative interpretation is often used to supplement qualitative interpretation. The authors provide an overview of patient preparation, common imaging findings, and potential pitfalls that radiologists and nuclear medicine physicians should know when performing and interpreting dopamine transporter examinations. Alternatives to 123I-ioflupane imaging for the evaluation of nigrostriatal degeneration are also briefly discussed. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material. See the invited commentary by Intenzo and Colarossi in this issue.

[18F]FE-PE2I DAT correlates with Parkinson's disease duration, stage, and rigidity/bradykinesia scores: a PET radioligand validation study

BACKGROUND

Correlations between dopamine transporter (DAT) availability and Parkinson's disease (PD) motor symptoms vary depending on the imaging modality, choice of regions of interest and clinical measures. We aimed to validate the PET radioligand [¹⁸F]FE-PE2I as a clinical biomarker in PD, hypothesizing negative correlations between DAT availability in specified nigrostriatal regions with symptom duration, disease stage and motor symptom scores.

METHODS

We included 41 PD patients (age 45-79 years; H&Y stage < 3) and 37 healthy control subjects in a cross-sectional study with dynamic [¹⁸F]FE-PE2I PET. Binding potential (BP_ND) was estimated in the caudate nucleus, putamen, ventral striatum, sensorimotor striatum, and substantia nigra using the cerebellum as reference region.

RESULTS

We found negative correlations (p < 0.02) between symptom duration and BP_ND in the putamen and sensorimotor striatum (r_s = - .42; r_s = - .51), and between H&Y stage and BP_ND in caudate nucleus, putamen, sensorimotor striatum, and substantia nigra (r_s between - .40 and - .54). The first correlations were better described with exponential fitting. MDS-UPDRS-III in 'OFF' state correlated negatively (p < 0.04) with BP_ND in the sensorimotor striatum (r_s = - .47), and excluding tremor score also in the putamen (r_s = - .45).

CONCLUSION

Results are in agreement with earlier findings in in vivo and post-mortem studies and validate [¹⁸F]FE-PE2I as a functional PD biomarker for PD severity.

TRIAL REGISTRATION

EudraCT 2011-0020050, Registered April 26 2011; EudraCT 2017-003327-29, Registered October 08 2017; EudraCT 2017-001585-19, Registered August 2 2017. https://eudract.ema.europa.eu/ .

Imaging in Movement Disorders

OBJECTIVE

This article reviews commonly used imaging modalities in movement disorders, particularly parkinsonism. The review includes the diagnostic utility, role in differential diagnosis, reflection of pathophysiology, and limitations of neuroimaging in the setting of movement disorders. It also introduces promising new imaging modalities and describes the current status of research.

LATEST DEVELOPMENTS

Iron-sensitive MRI sequences and neuromelanin-sensitive MRI can be used to directly assess the integrity of nigral dopaminergic neurons and thus may reflect disease pathology and progression throughout the full range of severity in Parkinson disease (PD). The striatal uptake of presynaptic radiotracers in their terminal axons as currently assessed using clinically approved positron emission tomography (PET) or single-photon emission computed tomography (SPECT) imaging correlates with nigral pathology and disease severity only in early PD. Cholinergic PET, using radiotracers that target the presynaptic vesicular acetylcholine transporter, constitutes a substantial advance and may provide crucial insights into the pathophysiology of clinical symptoms such as dementia, freezing, and falls.

ESSENTIAL POINTS

In the absence of valid, direct, objective biomarkers of intracellular misfolded α-synuclein, PD remains a clinical diagnosis. The clinical utility of PET- or SPECT-based striatal measures is currently limited given their lack of specificity and inability to reflect nigral pathology in moderate to severe PD. These scans may be more sensitive than clinical examination to detect nigrostriatal deficiency that occurs in multiple parkinsonian syndromes and may still be recommended for clinical use in the future to identify prodromal PD if and when disease-modifying treatments become available. Multimodal imaging to evaluate underlying nigral pathology and its functional consequences may hold the key to future advances.

Head-to-Head Comparison Between Rabbit Sign and EANM/SNMMI Criteria for the 18F-DOPA Visual Assessment of Parkinsonian Syndromes in PET/MRI: A Multiple Expert-Based and Blinded Controlled Study

PURPOSE

The aim of this study was to compare the diagnostic performance of the rabbit visual pattern versus the one endorsed by the EANM/SNMMI for the diagnosis of parkinsonian syndromes in PET/MRI.

PATIENTS AND METHODS

The 18F-DOPA PET images of 129 consecutive patients (65 Park+ and 64 controls) with 1 year of clinical follow-up were reviewed independently by 5 experienced readers on the same imaging workstation, blinded to the final clinical diagnosis. Two visual methods were assessed independently, with several days to months of interval: the criteria endorsed by EANM/SNMMI and the "rabbit" shape of the striate assessed on 3D MIP images. The sensitivities, specificities, likelihood ratios, and predictive values of the 2 diagnostic tests were estimated simultaneously by using the "comparison of 2 binary diagnostic tests to a paired design" method.

RESULTS

The estimated 95% confidence interval (CI) of sensitivities and specificities ranged from 49.4% to 76.5% and from 83.2% to 97.7%, respectively. The 95% CI estimates of positive and negative likelihood ratios ranged from 3.8 to 26.7 and from 0.26 to 0.56, respectively. The 95% CI estimates of the positive and negative predictive values ranged from 78.1% to 96.7% and from 60.3% to 81.4%, respectively. For all the parameters, no statistical difference was observed between the 2 methods (P > 0.05). The rabbit sign reduced the readers' discrepancies by 25%, while maintaining the same performance.

CONCLUSIONS

The rabbit visual pattern appears at least comparable to the current EANM/SNMMI reference procedure for the assessment of parkinsonian syndromes in daily clinical practice, without the need of any image postprocessing. Further multicenter prospective studies would be of relevance to validate these findings.

Wearable sensors during drawing tasks to measure the severity of essential tremor

Commonly used methods to assess the severity of essential tremor (ET) are based on clinical observation and lack objectivity. This study proposes the use of wearable accelerometer sensors for the quantitative assessment of ET. Acceleration data was recorded by inertial measurement unit (IMU) sensors during sketching of Archimedes spirals in 17 ET participants and 18 healthy controls. IMUs were placed at three points (dorsum of hand, posterior forearm, posterior upper arm) of each participant's dominant arm. Movement disorder neurologists who were blinded to clinical information scored ET patients on the Fahn-Tolosa-Marin rating scale (FTM) and conducted phenotyping according to the recent Consensus Statement on the Classification of Tremors. The ratio of power spectral density of acceleration data in 4-12 Hz to 0.5-4 Hz bands and the total duration of the action were inputs to a support vector machine that was trained to classify the ET subtype. Regression analysis was performed to determine the relationship of acceleration and temporal data with the FTM scores. The results show that the sensor located on the forearm had the best classification and regression results, with accuracy of 85.71% for binary classification of ET versus control. There was a moderate to good correlation (r² = 0.561) between FTM and a combination of power spectral density ratio and task time. However, the system could not accurately differentiate ET phenotypes according to the Consensus classification scheme. Potential applications of machine-based assessment of ET using wearable sensors include clinical trials and remote monitoring of patients.

Single Photon Emission Computed Tomography/Positron Emission Tomography Molecular Imaging for Parkinsonism: A Fast-Developing Field

The early differential diagnosis of Parkinson disease and atypical parkinsonism is a major challenge. The use of single photon emission computed tomography (SPECT)/positron emission tomography (PET) molecular imaging to investigate parkinsonism is a fast‐developing field. Imaging biomarker research may potentially lead to more accurate disease detection, enabling earlier diagnosis and treatment. This review summarizes recent SPECT/PET advances in radiopharmaceuticals and imaging technologies/analyses that improve the diagnosis of neurodegenerative parkinsonism. We are currently witnessing a turning point in the field. Integrating molecular imaging as a diagnostic technique represents an opportunity to reassess the strategies for diagnosing neurodegenerative parkinsonism. ANN NEUROL 2021;90:711–719

Parkinson's disease multimodal imaging: F-DOPA PET, neuromelanin-sensitive and quantitative iron-sensitive MRI

Parkinson's disease (PD) is a neurodegenerative synucleinopathy characterized by the degeneration of neuromelanin (NM)-containing dopaminergic neurons and deposition of iron in the substantia nigra (SN). How regional NM loss and iron accumulation within specific areas of SN relate to nigro-striatal dysfunction needs to be clarified. We measured dopaminergic function in pre- and postcommissural putamen by [¹⁸F]DOPA PET in 23 Parkinson's disease patients and 23 healthy control (HC) participants in whom NM content and iron load were assessed in medial and lateral SN, respectively, by NM-sensitive and quantitative R2* MRI. Data analysis consisted of voxelwise regressions testing the group effect and its interaction with NM or iron signals. In PD patients, R2* was selectively increased in left lateral SN as compared to healthy participants, suggesting a local accumulation of iron in Parkinson's disease. By contrast, NM signal differed between PD and HC, without specific regional specificity within SN. Dopaminergic function in posterior putamen decreased as R2* increased in lateral SN, indicating that dopaminergic function impairment progresses with iron accumulation in the SN. Dopaminergic function was also positively correlated with NM signal in lateral SN, indicating that dopaminergic function impairment progresses with depigmentation in the SN. A complex relationship was detected between R2* in the lateral SN and NM signal in the medial SN. In conclusion, multimodal imaging reveals regionally specific relationships between iron accumulation and depigmentation within the SN of Parkinson's disease and provides in vivo insights in its neuropathology.

Dopamine transporter SPECT imaging in Parkinson’s disease and parkinsonian disorders

The dopamine transporter (DAT) imaging provides an objective tool for the assessment of dopaminergic function of presynaptic terminals which is valuable for the differential diagnosis of parkinsonian disorders related to a striatal dopaminergic deficiency from movement disorders not related a striatal dopaminergic deficiency. DAT imaging with single-photon emission computed tomography (SPECT) can be used to confirm or exclude a diagnosis of dopamine deficient parkinsonism in cases where the diagnosis is unclear. It can also detect the dopaminergic dysfunction in presymptomatic subjects at risk for Parkinson’s disease (PD) since the reduced radiotracer binding to DATs in striatum is already present in the prodromal stage of PD. This review covers the rationale of using DAT SPECT imaging in the diagnosis of PD and other parkinsonian disorders, specifically focusing on the practical aspects of imaging and routine clinical indications.

Co-registration Analysis of Fluorodopa and Fluorodeoxyglucose Positron Emission Tomography for Differentiating Multiple System Atrophy Parkinsonism Type From Parkinson's Disease

It is difficult to differentiate between Parkinson's disease and multiple system atrophy parkinsonian subtype (MSA-P) because of the overlap of their signs and symptoms. Enormous efforts have been made to develop positron emission tomography (PET) imaging to differentiate these diseases. This study aimed to investigate the co-registration analysis of ¹⁸F-fluorodopa and ¹⁸F-flurodeoxyglucose PET images to visualize the difference between Parkinson's disease and MSA-P. We enrolled 29 Parkinson's disease patients, 28 MSA-P patients, and 10 healthy controls, who underwent both ¹⁸F-fluorodopa and ¹⁸F-flurodeoxyglucose PET scans. Patients with Parkinson's disease and MSA-P exhibited reduced bilateral striatal ¹⁸F-fluorodopa uptake (p < 0.05, vs. healthy controls). Both regional specific uptake ratio analysis and statistical parametric mapping analysis of ¹⁸F-flurodeoxyglucose PET revealed hypometabolism in the bilateral putamen of MSA-P patients and hypermetabolism in the bilateral putamen of Parkinson's disease patients. There was a significant positive correlation between ¹⁸F-flurodeoxyglucose uptake and ¹⁸F-fluorodopa uptake in the contralateral posterior putamen of MSA-P patients (rs = 0.558, p = 0.002). Both ¹⁸F-flurodeoxyglucose and ¹⁸F-fluorodopa PET images showed that the striatum was rabbit-shaped in the healthy control group segmentation analysis. A defective rabbit-shaped striatum was observed in the ¹⁸F-fluorodopa PET image of patients with Parkinson's disease and MSA-P. In the segmentation analysis of ¹⁸F-flurodeoxyglucose PET image, an intact rabbit-shaped striatum was observed in Parkinson's disease patients, whereas a defective rabbit-shaped striatum was observed in MSA-P patients. These findings suggest that there were significant differences in the co-registration analysis of ¹⁸F-flurodeoxyglucose and ¹⁸F-fluorodopa PET images, which could be used in the individual analysis to differentiate Parkinson's disease from MSA-P.

The role of the deep convolutional neural network as an aid to interpreting brain [18F]DOPA PET/CT in the diagnosis of Parkinson's disease

OBJECTIVES

To test the performance of a 3D convolutional neural network (CNN) in analysing brain [¹⁸F]DOPA PET/CT in order to identify patients with nigro-striatal neurodegeneration. We evaluated the robustness of the 3D CNN by testing it against a manual regional analysis of the striata by using a striatal-to-occipital ratio (SOR).

METHODS

We analyzed patients who had undergone [¹⁸F]DOPA PET/CT from 2016 to 2018. Two examiners interpreted PET/CT images as positive or negative. Only patients with at least 2 years of follow-up and an ascertained neurological diagnosis were included. A 3D CNN was developed to evaluate [¹⁸F]DOPA PET/CT and refine the diagnosis of movement disorder. This system required training and testing, which were carried out on 2/3 and 1/3 of patients, respectively. A regional analysis was also conducted by drawing region of interest on T1-weighted 3D MRI scans, on which the [¹⁸F]DOPA PET images were first co-registered.

RESULTS

Ninety-eight patients were enrolled: 43 presented nigro-striatal degeneration and 55 negative cases used as controls. After training on 69 patients, the diagnostic performance of the 3D CNN was then calculated in 29 patients. Sensitivity, specificity, negative predictive value, positive predictive value and accuracy were 100%, 89%, 100%, 85% and 93%, respectively. When we compared the 3D CNN results with the SOR analysis, we found that the two patients falsely classified as positive by the 3D CNN procedure showed SOR values ≤ 5^th percentile of the negative cases' distribution.

CONCLUSIONS

3D CNNs are able to interpret [¹⁸F]DOPA PET/CT properly, revealing patients affected by Parkinson's disease.

KEY POINTS

• [¹⁸F]DOPA PET/CT is a sensitive diagnostic tool to identify patients with nigro-striatal neurodegeneration. • A semiquantitative evaluation of the images allows a more confident interpretation of the PET findings. • 3D convolutional neural network allows an accurate interpretation of 18F-DOPA PET/CT images, revealing patients affected by Parkinson's disease.

Comparison of 6-[18F]FDOPA PET with Nigrosome 1 detection in patients with parkinsonism

Background

The functional 6-[¹⁸F]FDOPA positron emission tomography (PET) can be a helpful tool in differentiating parkinsonism with dopaminergic deficiency from clinically similar differential diagnoses. Furthermore, in T2*/susceptibility-weighted imaging (SWI) magnetic resonance imaging (MRI) sequences the structural integrity of the Nigrosome 1 (N1) can be assessed by checking the presence of the swallow tail sign (STS). We therefore retrospectively compared the performance of the 6-[¹⁸F]FDOPA PET with the N1 detection in patients suspected with parkinsonian diseases. Forty-three consecutive patients (m: 23, f: 20, mean age: 63 ± 12 years) were included in the study. They underwent clinically indicated 6-[¹⁸F]FDOPA PET/MRI scans as part of their neurological evaluation of uncertain parkinsonian syndromes. Visual and semi-quantitative PET imaging results were statistically compared with visual N1 assessment on 3 T SWI. As the gold standard, we defined the clinical diagnosis at the last follow-up, which included idiopathic Parkinson syndrome (IPS; n = 18), atypical parkinsonian syndromes (APS; n = 9) and other neurological diseases without dopaminergic deficit (n = 16).

Results

Thirty-five of 43 patients (81%, Kappa 0.611) had corresponding results in 6-[¹⁸F]FDOPA PET and SWI. Seven of the remaining 8 patients were correctly diagnosed by 6-[¹⁸F]FDOPA PET alone. Sensitivity, specificity and accuracy for 6-[¹⁸F]FDOPA and N1 imaging were 93%, 94%, 93% and 82%, 75%, 79%, respectively.

Conclusions

6-[¹⁸F]FDOPA PET and Nigrosome 1 evaluation had an overall good intermodality agreement. Diagnostic agreement was very good in cases of clinically suspected idiopathic Parkinson syndrome and fair in atypical parkinsonian syndromes, but poor in patients with non-parkinsonian disorders. 6-[¹⁸F]FDOPA PET showed higher sensitivity, specificity and accuracy in discriminating parkinsonian syndromes from non-parkinsonian disorders than the N1 evaluation. In summary, the additional benefit of N1 assessment in patients with APS or parkinsonism without dopaminergic deficit needs to be proven by prospective studies.

Non-FDG PET/CT

The major applications for molecular imaging with PET in clinical practice concern cancer imaging. Undoubtedly, 18F-FDG represents the backbone of nuclear oncology as it remains so far the most widely employed positron emitter compound. The acquired knowledge on cancer features, however, allowed the recognition in the last decades of multiple metabolic or pathogenic pathways within the cancer cells, which stimulated the development of novel radiopharmaceuticals. An endless list of PET tracers, substantially covering all hallmarks of cancer, has entered clinical routine or is being investigated in diagnostic trials. Some of them guard significant clinical applications, whereas others mostly bear a huge potential. This chapter summarizes a selected list of non-FDG PET tracers, described based on their introduction into and impact on clinical practice.

[Recommendation for the differentiated use of nuclear medical diagnostic for parkinsonian syndromes]

The present work provides an overview of the various nuclear medicine methods in the diagnosis of neurodegenerative parkinsonian syndromes and their respective evidence and is intended to enable practical decision-making aids in the application and interpretation of the methods and findings. The value of the procedures differs considerably in relation to the two relevant diagnostic questions. On the one hand, it is the question of whether there is a neurodegenerative parkinsonian syndrome at all, and on the other hand the question of which one. While the DAT-SPECT is undisputedly the method of choice for answering the first question (taking certain parameters into account), this method is not suitable for answering the second question. To categorise parkinsonian syndromes into idiopathic (i. e. Parkinson´s disease) or atypical, various procedures are used in everyday clinical practice including MIBG scintigraphy, and FDG-PET. We explain why FDG-PET currently is not only the most suitable of these methods to differentiate an idiopathic parkinsonian syndrome, from an atypical Parkinson's syndrome, but also enables sufficiently valid to distinguish the various atypical neurodegenerative Parkinson's syndromes (i. e. MSA, PSP and CBD) from each other and therefore should be reimbursed by health insurances.

Longitudinal functional connectivity changes related to dopaminergic decline in Parkinson's disease

BACKGROUND

Resting-state functional magnetic resonance imaging (fMRI) studies have demonstrated that basal ganglia functional connectivity is altered in Parkinson's disease (PD) as compared to healthy controls. However, such functional connectivity alterations have not been related to the dopaminergic deficits that occurs in PD over time.

OBJECTIVES

To examine whether functional connectivity impairments are correlated with dopaminergic deficits across basal ganglia subdivisions in patients with PD both cross-sectionally and longitudinally.

METHODS

We assessed resting-state functional connectivity of basal ganglia subdivisions and dopamine transporter density using 11C-PE2I PET in thirty-four PD patients at baseline. Of these, twenty PD patients were rescanned after 19.9 ± 3.8 months. A seed-based approach was used to analyze resting-state fMRI data. 11C-PE2I binding potential (BPND) was calculated for each participant. PD patients were assessed for disease severity.

RESULTS

At baseline, PD patients with greater dopaminergic deficits, as measured with 11C-PE2I PET, showed larger decreases in posterior putamen functional connectivity with the midbrain and pallidum. Reduced functional connectivity of the posterior putamen with the thalamus, midbrain, supplementary motor area and sensorimotor cortex over time were significantly associated with changes in DAT density over the same period. Furthermore, increased motor disability was associated with lower intraregional functional connectivity of the posterior putamen.

CONCLUSIONS

Our findings suggest that basal ganglia functional connectivity is related to integrity of dopaminergic system in patients with PD. Application of resting-state fMRI in a large cohort and longitudinal scanning may be a powerful tool for assessing underlying PD pathology and its progression.

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.

EANM practice guideline/SNMMI procedure standard for dopaminergic imaging in Parkinsonian syndromes 1.0

Purpose

This joint practice guideline or procedure standard was developed collaboratively by the European Association of Nuclear Medicine (EANM) and the Society of Nuclear Medicine and Molecular Imaging (SNMMI). The goal of this guideline is to assist nuclear medicine practitioners in recommending, performing, interpreting, and reporting the results of dopaminergic imaging in parkinsonian syndromes.

Methods

Currently nuclear medicine investigations can assess both presynaptic and postsynaptic function of dopaminergic synapses. To date both EANM and SNMMI have published procedural guidelines for dopamine transporter imaging with single photon emission computed tomography (SPECT) (in 2009 and 2011, respectively). An EANM guideline for D2 SPECT imaging is also available (2009). Since the publication of these previous guidelines, new lines of evidence have been made available on semiquantification, harmonization, comparison with normal datasets, and longitudinal analyses of dopamine transporter imaging with SPECT. Similarly, details on acquisition protocols and simplified quantification methods are now available for dopamine transporter imaging with PET, including recently developed fluorinated tracers. Finally, [¹⁸F]fluorodopa PET is now used in some centers for the differential diagnosis of parkinsonism, although procedural guidelines aiming to define standard procedures for [¹⁸F]fluorodopa imaging in this setting are still lacking.

Conclusion

All these emerging issues are addressed in the present procedural guidelines for dopaminergic imaging in parkinsonian syndromes.

Correlations between dopaminergic dysfunction and abnormal metabolic network activity in REM sleep behavior disorder

Striatal dopamine transporter (DAT) deficiency and abnormal expression of Parkinson's disease (PD)-related pattern (PDRP) have been observed in patients with idiopathic REM sleep behavior disorder (IRBD). This study aimed to investigate the correlations between these two measures with comparison to PD using a dual tracer imaging design. Age-matched 37 IRBD patients, 86 PD patients, and 15 control subjects underwent concurrent PET scans with 11C-CFT to quantify dopaminergic dysfunction and 18F-FDG to quantify PDRP expression. IRBD patients were divided into two subgroups: those with relatively normal (IRBD-RN) or abnormal (IRBD-AB) striatal DAT binding. Significantly decreased DAT binding and increased PDRP scores were present in all patient groups, except for IRBD-RN, relative to the controls. There was a significant effect of hemisphere and hemisphere × group interaction for DAT binding but not for PDRP expression. Significant correlations were observed between DAT binding and PDRP expression in the IRBD-AB and PD groups but not in the IRBD-RN group. IRBD patients present with an intermediate state in striatal DAT distribution and PDRP activity between PD and normal controls. The modest correlations between the two measures in both IRBD and PD suggest that differences in network activity cannot be fully explained by nigrostriatal dopaminergic denervation.

Longitudinal study of striatal aromatic l-amino acid decarboxylase activity in patients with idiopathic rapid eye movement sleep behavior disorder

STUDY OBJECTIVES

To determine if nigrostriatal dopaminergic system function, evaluated by aromatic l-amino acid decarboxylase (AADC) activity using 6-[¹⁸F]fluoro-meta-tyrosine brain positron emission tomography (FMT-PET) can accurately and efficiently identify idiopathic rapid-eye-movement behavior disorder (IRBD) individuals at risk for conversion to a clinical diagnosis of Parkinson's disease (PD) or dementia with Lewy bodies (DLB).

METHODS

We assessed prospectively striatal aromatic l-amino acid decarboxylase activity using FMT brain PET imaging in IRBD patients who were followed systematically every 1-3 months for 1-10 years. IRBD patients (n = 27) were enrolled in this prospective cohort study starting in 2009. Those who underwent follow-up scans between January 2011 and September 2014 (n = 24) were analyzed in the present study.

RESULTS

Of the 24 IRBD patients with baseline and follow-up FMT-PET scans, 11 (45.8%) developed PD (n = 6) or DLB (n = 5). Compared to IRBD patients who were still disease-free, those who developed PD (n = 5) or DLB with parkinsonism (n = 1) had significantly reduced bilateral putaminal FMT uptake during the follow-up. Furthermore, the rate of FMT decline between baseline and follow-up scans was higher in all converted patients, even for those with DLB without parkinsonism, than in IRBD patients who remained disease-free.

CONCLUSIONS

FMT-PET, which represents a dynamic change in AADC activity over time, may also be a useful predictor for the risk of conversion to PD or DLB over short-term clinical follow-up periods, or when testing neuroprotective and restorative strategies in the prodromal phases of PD or DLB.

Innovative Molecular Imaging for Clinical Research, Therapeutic Stratification, and Nosography in Neuroscience

Over the past few decades, several radiotracers have been developed for neuroimaging applications, especially in PET. Because of their low steric hindrance, PET radionuclides can be used to label molecules that are small enough to cross the blood brain barrier, without modifying their biological properties. As the use of 11C is limited by its short physical half-life (20 min), there has been an increasing focus on developing tracers labeled with 18F for clinical use. The first such tracers allowed cerebral blood flow and glucose metabolism to be measured, and the development of molecular imaging has since enabled to focus more closely on specific targets such as receptors, neurotransmitter transporters, and other proteins. Hence, PET and SPECT biomarkers have become indispensable for innovative clinical research. Currently, the treatment options for a number of pathologies, notably neurodegenerative diseases, remain only supportive and symptomatic. Treatments that slow down or reverse disease progression are therefore the subject of numerous studies, in which molecular imaging is proving to be a powerful tool. PET and SPECT biomarkers already make it possible to diagnose several neurological diseases in vivo and at preclinical stages, yielding topographic, and quantitative data about the target. As a result, they can be used for assessing patients' eligibility for new treatments, or for treatment follow-up. The aim of the present review was to map major innovative radiotracers used in neuroscience, and explain their contribution to clinical research. We categorized them according to their target: dopaminergic, cholinergic or serotoninergic systems, β-amyloid plaques, tau protein, neuroinflammation, glutamate or GABA receptors, or α-synuclein. Most neurological disorders, and indeed mental disorders, involve the dysfunction of one or more of these targets. Combinations of molecular imaging biomarkers can afford us a better understanding of the mechanisms underlying disease development over time, and contribute to early detection/screening, diagnosis, therapy delivery/monitoring, and treatment follow-up in both research and clinical settings.

The Story of the Dopamine Transporter PET Tracer LBT-999: From Conception to Clinical Use

The membrane dopamine transporter (DAT) is involved in a number of brain disorders and its exploration by positron emission tomography (PET) imaging is highly relevant for the early and differential diagnosis, follow-up and treatment assessment of these diseases. A number of carbon-11 and fluor-18 labeled tracers are to date available for this aim, the majority of them being derived from the chemical structure of cocaine. The development of such a tracer, from its conception to its use, is a long process, the expected result being to obtain the best radiopharmaceutical adapted for clinical protocols. In this context, the cocaine derivative (E)-N-(4-fluorobut-2-enyl)2β-carbomethoxy-3β-(4′-tolyl)nortropane, or LBT-999, has passed all the required stages of the development that makes it now a highly relevant imaging tool, particularly in the context of Parkinson's disease. This review describes the different steps of the development of LBT-999 which initially came from its non-fluorinated derivative (E)-N-(3-iodoprop-2-enyl)-2-carbomethoxy-3-(4-methylphenyl) nortropane, or PE2I, because of its high promising properties. [¹⁸F]LBT-999 has been extensively characterized in rodent and non-human primate models, in which it demonstrated its capability to explore in vivo the DAT localized at the dopaminergic nerve endings as well as at the mesencephalic cell bodies, in physiological conditions. In lesion-induced rat models of Parkinson's disease, [¹⁸F]LBT-999 was able to precisely quantify in vivo the dopaminergic neuron loss, and to assess the beneficial effects of therapeutic approaches such as pharmacological treatment and cell transplantation. Finally recent clinical data demonstrated the efficiency of [¹⁸F]LBT-999 in the diagnosis of Parkinson's disease.

Head-to-head comparison of 18 F-FP-CIT and 123 I-FP-CIT for dopamine transporter imaging in patients with Parkinson's disease: A preliminary study

¹²³ I-FP-CIT and ¹⁸ F-FP-CIT are radiotracers which are widely used to diagnose Parkinson's disease (PD). However, to our knowledge, no studies to date have made head-to-head comparisons between ¹²³ I-FP-CIT and ¹⁸ F-FP-CIT. Therefore, in this study, ¹²³ I-FP-CIT SPECT/CT was compared with ¹⁸ F-FP-CIT PET/CT in the same cohort of subjects. Patients with PD and essential tremor (ET) underwent ¹²³ I-FP-CIT SPECT/CT and ¹⁸ F-FP-CIT PET/CT. Visual and semiquantitative analyses were conducted. The specific binding ratio (SBR) and putamen to caudate ratio (PCR) were compared between subjects who underwent ¹²³ I-FP-CIT SPECT/CT and ¹⁸ F-FP-CIT PET/CT. Visual analysis showed that the striatal uptake of both radiotracers was decreased in the PD group, whereas striatal uptake was intact in the ET group. The SBR between ¹²³ I-FP-CIT SPECT/CT and ¹⁸ F-FP-CIT PET/CT showed a positive correlation (r = .78, p < .01). However, the mean SBRs on ¹⁸ F-FP-CIT PET/CT were higher than those on ¹²³ I-FP-CIT SPECT/CT (2.19 ± .87 and 1.22 ± .49, respectively; p < .01). The PCRs in these two modalities were correlated with each other (r = .71, p < .01). The mean PCRs on ¹⁸ F-FP-CIT PET/CT were not significantly higher than those on ¹²³ I-FP-CIT SPECT/CT (1.31 ± .19 and 0.98 ± .06, respectively; p = .06). These preliminary results indicate that the uptake of both ¹²³ I-FP-CIT and ¹⁸ F-FP-CIT was decreased in the PD group when compared with the ET controls. Visual analyses using both methods did not affect the diagnostic accuracy in this study. However, semiquantitative analysis indicated a better contrast of ¹⁸ F-FP-CIT PET/CT relative to ¹²³ I-FP-CIT SPECT/CT.

F-18 FP-CIT PET in Multiple System Atrophy of the Cerebellar Type: Additional Role in Treatment

We evaluated the difference in the status of dopamine transporters (DATs) depending on Parkinsonism, cerebellar, and autonomic features using F-18 FP-CIT positron emission tomography (PET) in multiple system atrophy with cerebellar ataxia (MSA-C). We also assessed whether the DAT PET could be useful in the management of MSA-C. Forty-nine patients who were clinically diagnosed as possible to probable MSA-C were included. Based on the F-18 FP-CIT PET results, patients were classified into normal (n = 25) and abnormal (n = 24) scan groups. There were statistically significant differences in rigidity, bradykinesia, postural instability, asymmetry, and specific uptake ratio (SUR) between the two groups but no significant differences in tremor and cerebellar/autonomic symptoms. Dopaminergic medications were administered to 22 patients. All seven patients with normal scans showed no change, while 10 of the 15 patients with abnormal scans showed clinical improvement. There was a trend of a negative correlation between levodopa equivalent dose and SUR, but it was not statistically significant. DAT imaging, such as F-18 FP-CIT PET, may be useful in predicting the response to dopaminergic medication regardless of cerebellar/autonomic symptoms in MSA-C. In addition to being used for the diagnosis of the disease, it may be used as a treatment decision index.

11 C-PE2I and 18 F-Dopa PET for assessing progression rate in Parkinson's: A longitudinal study

BACKGROUND

¹⁸ F-dopa PET measuring aromatic l-amino acid decarboxylase activity is regarded as the gold standard for evaluating dopaminergic function in Parkinson's disease. Radioligands for dopamine transporters are also used in clinical trials and for confirming PD diagnosis. Currently, it is not clear which imaging marker is more reliable for assessing clinical severity and rate of progression. The objective of this study was to directly compare ¹⁸ F-dopa with the highly selective dopamine transporter radioligand ¹¹ C-PE2I for the assessment of motor severity and rate of progression in PD.

METHODS

Thirty-three mild-moderate PD patients underwent ¹⁸ F-dopa and ¹¹ C-PE2I PET at baseline. Twenty-three were followed up for 18.8 ± 3.4 months.

RESULTS

Standard multiple regression at baseline indicated that ¹¹ C-PE2I BP_ND predicted UPDRS-III and bradykinesia-rigidity scores (P < 0.05), whereas ¹⁸ F-dopa K_i did not make significant unique explanatory contributions. Voxel-wise analysis showed negative correlations between ¹¹ C-PE2I BP_ND and motor severity across the whole striatum bilaterally. ¹⁸ F-Dopa K_i clusters were restricted to the most affected putamen and caudate. Longitudinally, negative correlations were found between striatal Δ¹¹ C-PE2I BP_ND , ΔUPDRS-III, and Δbradykinesia-rigidity, whereas no significant associations were found for Δ¹⁸ F-dopa K_i . One cluster in the most affected putamen was identified in the longitudinal voxel-wise analysis showing a negative relationship between Δ¹¹ C-PE2I BP_ND and Δbradykinesia-rigidity.

CONCLUSIONS

Striatal ¹¹ C-PE2I appears to show greater sensitivity for detecting differences in motor severity than ¹⁸ F-dopa. Furthermore, dopamine transporter decline is closely associated with motor progression over time, whereas no such relationship was found with aromatic l-amino acid decarboxylase. ¹¹ C-PE2I may be more effective for evaluating the efficacy of neuroprotective treatments in PD. © 2017 International Parkinson and Movement Disorder Society.

Distinct Role of Striatal Functional Connectivity and Dopaminergic Loss in Parkinson's Symptoms

Degeneration of dopaminergic neurons is a hallmark of Parkinson's disease. However, its link to Parkinson's disease symptoms remains unclear. Striatal resting state functional connectivity differentiates between Parkinson's disease patients and healthy controls and might be a potential mediator of the effects of striatal dopaminergic degeneration onto Parkinson's disease symptoms. Here, we evaluated the relationship between dopaminergic deficits, striatal functional connectivity (SFC) at rest and different Parkinson's disease clinical symptoms in the largest currently established cohort of de novo Parkinson's disease patients. We show that SFC is an independent predictor of symptom severity in Parkinson's disease in addition to striatal dopaminergic deficits. Furthermore, we find that distinct SFC networks are associated with symptoms reflecting the ability to perform daily routine automatized motor tasks and clinician-rated Parkinson's disease motor symptoms. We find that reduced SFC is a major and independent predictor of Parkinson's disease symptoms going beyond the mere reflection of striatal dopaminergic input loss. These findings indicate the high value of SFC as a clinically relevant biomarker in Parkinson's disease.

Functional volumetric analysis of striatum using F-18 FP-CIT PET in patients with idiopathic Parkinson's disease and normal subjects

OBJECTIVE

We applied a simple isocontour volume-of-interest (VOI) method to analyze the whole striatum in an F-18 FP-CIT PET image and to investigate the usefulness of the method in differentiating healthy subjects from idiopathic Parkinson's disease (IPD) patients and the correlation of the value of functional volume parameters with the motor symptoms in patients with IPD.

METHODS

Forty-three IPD patients and 23 age-matched healthy controls underwent F-18 FP-CIT PET. Using a dedicated workstation, VOIs for the whole striatum were drawn automatically with the gradient delineation method. The SUVmax, SUVmean, functional volume (FV), striatal volume activity (SVA), striatal-specific binding (SSB), and volume-specific uptake ratio (VSUR) were compared between the IPD patients and the normal subjects. In the IPD patients, the correlation between the clinical factor and the functional parameters was assessed.

RESULTS

The SUVmax, SUVmean, FV, SVA, SSB, and VSUR were significantly lower in the IPD patients than in the normal subjects. In the receiver operating characteristic analysis, those parameters had significant and good-to-excellent accuracy. In the patients with IPD, a moderate negative correlation was revealed between the SUVmax and H&Y stage, the SUVmean and H&Y stage, SVA and H&Y stage, the VSUR and H&Y stage, the FV and bradykinesia, and the SVA and bradykinesia.

CONCLUSION

The functional volumetric analysis of the striatum based on simple isocontour VOI was a useful method of analyzing the F-18 FP-CIT PET image. Not only can it be easily applied in daily clinical practice, but it can also be used as a clinical parameter to discriminate IPD and to correlate it with the disease severity.

(123)I-FP-CIT SPECT imaging in early diagnosis of dementia in patients with and without a vascular component

Alzheimer’s disease (AD) and vascular dementia (VaD) are the most common cause of dementia. Cerebral ischemia is a major risk factor for development of dementia. ¹²³I-FP-CIT SPECT (DaTScan) is a complementary tool in the differential diagnoses of patients with incomplete or uncertain Parkinsonism. Additional application of DaTScan enables the categorization of Parkinsonian disease with dementia (PDD), and its differentiation from pure AD, and may further contribute to change the therapeutic decision. The aim of this study was to analyze the vascular contribution towards dementia and mild cognitive impairment (MCI). We evaluated the utility of DaTScan for the early diagnosis of dementia in patients with and without a clinical vascular component, and the association between neuropsychological function, vascular component and dopaminergic function on DaTScan. One-hundred and five patients with MCI or the initial phases of dementia were studied prospectively. We developed an initial assessment using neurologic examination, blood tests, cognitive function tests, structural neuroimaging and DaTScan. The vascular component was later quantified in two ways: clinically, according to the Framingham Risk Score (FRS) and by structural neuroimaging using Wahlund Scale Total Score (WSTS). Early diagnosis of dementia was associated with an abnormal DaTScan. A significant association was found between a high WSTS and an abnormal DaTScan (p < 0.01). Mixed AD was the group with the highest vascular component, followed by the VaD group, while MCI and pure AD showed similar WSTS. No significant associations were found between neuropsychological impairment and DaTScan independently of associated vascular component. DaTScan seems to be a good tool to discriminate, in a first clinical assessment, patients with MCI from those with established dementia. There was bigger general vascular affectation observable in MRI or CT in patients with abnormal dopaminergic uptake seen on DaTScan.

Orbitofrontal (18) F-DOPA Uptake and Movement Preparation in Parkinson's Disease

In Parkinson's disease (PD) degeneration of mesocortical dopaminergic projections may determine cognitive and behavioral symptoms. Choice reaction time task is related to attention, working memory, and goal-directed behavior. Such paradigm involves frontal cortical circuits receiving mesocortical dopamine which are affected early in PD. The aim of this study is to characterize the role of dopamine on the cognitive processes that precede movement in a reaction time paradigm in PD. We enrolled 16 newly diagnosed and untreated patients with PD without cognitive impairment or depression and 10 control subjects with essential tremor. They performed multiple-choice reaction time task with the right upper limb and brain ¹⁸F-DOPA PET/CT scan. A significant inverse correlation was highlighted between average reaction time and ¹⁸F-DOPA uptake in the left lateral orbitofrontal cortex. No correlations were found between reaction time and PD disease severity or between reaction time and ¹⁸F-DOPA uptake in controls. Our study shows that in PD, but not in controls, reaction time is inversely related to the levels of dopamine in the left lateral orbitofrontal cortex. This novel finding underlines the role of dopamine in the lateral orbitofrontal cortex in the early stages of PD, supporting a relation between the compensatory cortical dopamine and movement preparation.

Brain (18)F-DOPA PET and cognition in de novo Parkinson's disease

PURPOSE

The role of mesocortical dopaminergic pathways in the cognitive function of patients with early Parkinson's disease (PD) needs to be further clarified.

METHODS

The study groups comprised 15 drug-naive patients with de novo PD and 10 patients with essential tremor (controls) who underwent (18)F-DOPA PET (static acquisition, normalization on mean cerebellar counts) and an extended neuropsychological test battery. Factor analysis with varimax rotation was applied to the neuropsychological test scores, to yield five factors from 16 original scores, which explained 82 % of the total variance. Correlations between cognitive factors and (18)F-DOPA uptake were assessed with SPM8, taking age and gender as nuisance variables.

RESULTS

(18)F-DOPA uptake was significantly lower in PD patients than in controls in the bilateral striatum, mainly in the more affected (right) hemisphere, and in a small right temporal region. Significant positive correlations were found only in PD patients between the executive factor and (18)F-DOPA uptake in the bilateral anterior cingulate cortex (ACC) and the middle frontal gyrus, between the verbal fluency factor and (18)F-DOPA uptake in left BA 46 and the bilateral striatum, and between the visuospatial factor and (18)F-DOPA uptake in the left ACC and bilateral striatum. No correlations were found between (18)F-DOPA uptake and either the verbal memory factor or the abstraction-working memory factor.

CONCLUSION

These data clarify the role of the mesocortical dopaminergic pathways in cognitive function in early PD, highlighting the medial frontal lobe, anterior cingulate, and left BA 46 as the main sites of cortical correlation with executive and language functions.

Neuroimaging in Parkinson disease: from research setting to clinical practice

Over the past three decades, neuroimaging studies-including structural, functional and molecular modalities-have provided invaluable insights into the mechanisms underlying Parkinson disease (PD). Observations from multimodal neuroimaging techniques have indicated changes in brain structure and metabolic activity, and an array of neurochemical changes that affect receptor sites and neurotransmitter systems. Characterization of the neurobiological alterations that lead to phenotypic heterogeneity in patients with PD has considerably aided the in vivo investigation of aetiology and pathophysiology, and the identification of novel targets for pharmacological or surgical treatments, including cell therapy. Although PD is now considered to be very complex, no neuroimaging modalities are specifically recommended for routine use in clinical practice. However, conventional MRI and dopamine transporter imaging are commonly used as adjuvant tools in the differential diagnosis between PD and nondegenerative causes of parkinsonism. First-line neuroimaging tools that could have an impact on patient prognosis and treatment strategies remain elusive. This Review discusses the lessons learnt from decades of neuroimaging research in PD, and the promising new approaches with potential applicability to clinical practice.

¹⁸F-DOPA PET/computed tomography imaging

18F-DOPA is a radiopharmaceutical with interesting clinical applications and promising performances in the evaluation of the integrity of dopaminergic pathways, brain tumors, NETs (especially MTCs, paragangliomas, and pheochromocytomas), and congenital hyperinsulinism. 18F-DOPA traces a very specific metabolic pathway and has a very precise biodistribution pattern. As for any radiopharmaceutical, the knowledge of the normal distribution of 18F-DOPA, its physiologic variants, and its possible pitfalls is essential for the correct interpretation of PET scans. Moreover, it is important to be aware of the potential false-positive and false-negative episodes that can occur in the various clinical settings.

Depressive symptoms in Parkinson's disease are related to reduced [123I]FP-CIT binding in the caudate nucleus

BACKGROUND

Depression is a common neuropsychiatric symptom in Parkinson's disease (PD). In previous research, PD-related depression was associated with striatal dopaminergic deficits, presumably due to degeneration of brainstem dopaminergic projections. Segregated areas of the striatum are crucially involved in various parallelly arranged cortical-striatal-thalamocortical circuits and serve functions in, among others, motor control or emotion. This suggests regional specificity of dopaminergic deficits in the striatum in motor and depressive symptoms in PD.

METHODS

In this cross-sectional retrospective study, we correlated severity scores of depressive and motor symptoms in 100 non-demented PD patients (median Hoehn & Yahr stage: 2) with dopamine loss in specific regions of the striatum as measured by [(123)I]FP-CIT SPECT tracer binding to the dopamine transporter (DaT).

RESULTS

Depressive symptoms were related to lower DaT binding in the right caudate nucleus, while motor symptoms were associated with decreased DaT binding in the right putamen. This double dissociation was most pronounced in early-stage PD patients.

CONCLUSIONS

These results suggest that depressive symptoms in PD are associated with dopamine loss in the caudate nucleus, possibly related to degeneration of dopaminergic projections from the ventral tegmental area, while motor symptoms are associated with low dopamine signalling to the putamen and loss of nigrostriatal projections. This is consistent with the neuroanatomy of partially segregated cortical-striatal-thalamocortical circuits and supports the role of dysfunctional associative and motivational circuits in PD-related depression.

A simple algorithm for subregional striatal uptake analysis with partial volume correction in dopaminergic PET imaging

OBJECTIVE

In positron emission tomography (PET) of the dopaminergic system, quantitative measurements of nigrostriatal dopamine function are useful for differential diagnosis. A subregional analysis of striatal uptake enables the diagnostic performance to be more powerful. However, the partial volume effect (PVE) induces an underestimation of the true radioactivity concentration in small structures. This work proposes a simple algorithm for subregional analysis of striatal uptake with partial volume correction (PVC) in dopaminergic PET imaging.

METHODS

The PVC algorithm analyzes the separate striatal subregions and takes into account the PVE based on the recovery coefficient (RC). The RC is defined as the ratio of the PVE-uncorrected to PVE-corrected radioactivity concentration, and is derived from a combination of the traditional volume of interest (VOI) analysis and the large VOI technique. The clinical studies, comprising 11 patients with Parkinson's disease (PD) and 6 healthy subjects, were used to assess the impact of PVC on the quantitative measurements. Simulations on a numerical phantom that mimicked realistic healthy and neurodegenerative situations were used to evaluate the performance of the proposed PVC algorithm. In both the clinical and the simulation studies, the striatal-to-occipital ratio (SOR) values for the entire striatum and its subregions were calculated with and without PVC.

RESULTS

In the clinical studies, the SOR values in each structure (caudate, anterior putamen, posterior putamen, putamen, and striatum) were significantly higher by using PVC in contrast to those without. Among the PD patients, the SOR values in each structure and quantitative disease severity ratings were shown to be significantly related only when PVC was used. For the simulation studies, the average absolute percentage error of the SOR estimates before and after PVC were 22.74% and 1.54% in the healthy situation, respectively; those in the neurodegenerative situation were 20.69% and 2.51%, respectively.

CONCLUSIONS

We successfully implemented a simple algorithm for subregional analysis of striatal uptake with PVC in dopaminergic PET imaging. The PVC algorithm provides an accurate measure of the SOR in the entire striatum and its subregions, and improves the correlation between the SOR values and the clinical disease severity of PD patients.

An FP-CIT PET comparison of the differences in dopaminergic neuronal loss between idiopathic Parkinson disease with dementia and without dementia

Previous studies have demonstrated a decreased density of dopamine transporters (DAT) in basal ganglia in patients with idiopathic Parkinson disease (IPD) using I-n-fluoropropyl-2b-carbomethoxy-3b-(4-iodophenyl) nortropane (FP-CIT), and the reductions in striatal DAT levels were inversely correlated with the severity of motor dysfunction in IPD. However, there has been no study on the correlation of DAT levels between IPD patients with and without cognitive dysfunction. Thus, we evaluated the differences in regional DAT density in the brain of patients with IPD without dementia and those with dementia using FP-CIT positron emission tomography. We recruited 24 consecutive patients with IPD, including 7 with IPD without dementia and 17 with IPD with dementia, and 18 healthy controls. FP-CIT positron emission tomography scans were acquired 90 and 210 minutes after the FP-CIT injection. The DAT density did not differ in the caudate nucleus or the putamen between patients with IPD without dementia and those with dementia. However, the DAT density between the 2 groups with IPD demonstrated a significantly decreased density compared with that of healthy controls in the putamen. We cautiously suggest that there is no relationship between DAT density and cognitive severity because there were no significant differences in the DAT density between IPD with dementia and those without dementia.

Molecular imaging in oncology

The major application for PET imaging in clinical practice is represented by cancer imaging and (18)F-FDG is the most widely employed positron emitter compound. However, some diseases cannot be properly evaluated with this tracer and thus there is the necessity to develop more specific compounds. The last decades were a continuous factory for new radiopharmaceuticals leading to an endless list of PET tracers; however, just some of them guard diagnostic relevance in routine medical practice. This chapter describes a selected list of non-FDG PET tracers, basing on their introduction into and impact on clinical practice.

Automated striatal uptake analysis of ¹⁸F-FDOPA PET images applied to Parkinson's disease patients

OBJECTIVE

6-[(18)F]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.

METHODS

Brain images from FDOPA PET studies of 21 patients with PD and 6 healthy subjects were included in our automated striatal analyses. Images of each individual were spatially normalized into an FDOPA template. Subsequently, the image slice with the highest level of basal ganglia activity was chosen among the series of normalized images. Also, the immediate preceding and following slices of the chosen image were then selected. Finally, the summation of these three images was used to quantify and calculate the SOR values. The results obtained by automated analysis were compared with manual analysis by a trained and experienced image processing technologist.

RESULTS

The SOR values obtained from the automated analysis had a good agreement and high correlation with manual analysis. The differences in caudate, putamen, and striatum were -0.023, -0.029, and -0.025, respectively; correlation coefficients 0.961, 0.957, and 0.972, respectively.

CONCLUSIONS

We have successfully developed a method for automated striatal uptake analysis of FDOPA PET images. There was no significant difference between the SOR values obtained from this method and using manual analysis. Yet it is an unbiased time-saving and cost-effective program and easy to implement on a personal computer.

Biomarkers for Parkinson's disease

Biomarkers for detecting the early stages of Parkinson's disease (PD) could accelerate development of new treatments. Such biomarkers could be used to identify individuals at risk for developing PD, to improve early diagnosis, to track disease progression with precision, and to test the efficacy of new treatments. Although some progress has been made, there are many challenges associated with developing biomarkers for detecting PD in its earliest stages.

Blood oxygenation level-dependent activation in basal ganglia nuclei relates to specific symptoms in de novo Parkinson's disease

To aid the development of symptomatic and disease modifying therapies in Parkinson's disease (PD), there is a strong need to identify noninvasive measures of basal ganglia (BG) function that are sensitive to disease severity. This study examines the relation between blood oxygenation level-dependent (BOLD) activation in every nucleus of the BG and symptom-specific disease severity in early stage de novo PD. BOLD activation measured at 3 T was compared between 20 early stage de novo PD patients and 20 controls during an established precision grip force task. In addition to the BG nuclei, activation in specific thalamic and cortical regions was examined. There were three novel findings. First, there were significant negative correlations between total motor Unified PD Rating Scale and BOLD activation in bilateral caudate, bilateral putamen, contralateral external segment of the globus pallidus, bilateral subthalamic nucleus, contralateral substantia nigra, and thalamus. Second, bradykinesia was the symptom that most consistently predicted BOLD activation in the BG and thalamus. Also, BOLD activation in the contralateral internal globus pallidus was related to tremor. Third, the reduced cortical activity in primary motor cortex and supplementary motor area in de novo PD did not relate to motor symptoms. These findings demonstrate that BOLD activity in nuclei of the BG relates most consistently to bradykinesia and functional magnetic resonance imaging has strong potential to serve as a noninvasive marker for the state of BG function in de novo PD.

Non FDG PET

2- [(18)F]-fluoro-2-deoxy-D-glucose (FDG) is the radiopharmaceutical most frequently used for clinical positron emission tomography (PET). However, FDG cannot be used for many oncological, cardiological, or neurological conditions, either because the abnormal tissue does not concentrate it, or because the tissues under investigation demonstrate high physiological glucose uptake. Consequently, alternative PET tracers have been produced and introduced into clinical practice. The most important compounds in routine practice are (11)C-choline and (18)F-choline, mainly for the evaluation of prostate cancer; (1)C-methionine for brain tumours; (118)F-DOPA ((18)F-deoxiphenilalanine) for neuroendocrine tumours and movement disorders; (68)Ga-DOTANOC (tetraazacyclododecanetetraacetic acid-[1-Nal3]-octreotide) and other somatostatin analogues for neuroendocrine tumours; 11C-acetate for prostate cancer and hepatic masses and 18F-FLT (3-deoxy-3-fluorothymidine) for a number of malignant tumours. Another impetus for the development of new tracers is to enable the investigation of biological processes in tumours other than glucose metabolism. This is especially important in the field of response assessment, where there are new agents that are targeted more specifically at angiogenesis, hypoxia, apoptosis and other processes.

Progression of Parkinson's disease in the clinical phase: potential markers

Neuromodulatory or even neuroprotective therapy could soon be available for Parkinson's disease (PD), raising the question of how we should define and measure disease progression. Reported evidence suggests that several symptoms worsen with disease duration. Bradykinesia, rigidity, and activities of daily living deteriorate faster at the beginning of the disease, and this deterioration is paralleled by a decline in functional presynaptic dopaminergic activity, as shown by imaging techniques. Cognitive, speech, sleep, and gait difficulties might progress linearly in proportion to disease duration. Reduced variability in heart rate, orthostatic dysfunction, and visual hallucinations start to develop at mid-stage disease and are more common in late stages than earlier stages. In this Review, we summarise our current understanding of the progression of PD-associated symptoms and markers and conclude that an effective measurement of progression of PD must adapt to the different stages of the disease. In addition to routine clinical rating scales, new quantitative assessments of motor and non-motor symptoms, which should be more broadly available, reasonably priced, and easy-to-use, are needed.

Direct comparison of FP-CIT SPECT and F-DOPA PET in patients with Parkinson's disease and healthy controls

PURPOSE

Diagnosing Parkinson's disease (PD) on clinical grounds may be difficult, especially in the early stages of the disease. F-DOPA PET and FP-CIT SPECT scans are able to determine presynaptic dopaminergic activity in different ways. The aim of this study was to determine and compare the sensitivity and specificity of the two methods in the detection of striatal dopaminergic deficits in the same cohort of PD patients and healthy controls.

METHODS

Movement disorder specialists recruited 11 patients with early-stage PD and 17 patients with advanced PD. The patients underwent both an FP-CIT SPECT scan and an F-DOPA PET scan. In addition, 10 FP-CIT SPECT scans or 10 F-DOPA PET scans were performed in 20 healthy controls. A template with regions of interest was used to sample tracer activity of the caudate, putamen and a reference region in the brain. The outcome parameter was the striatooccipital ratio (SOR). Normal SOR values were determined in the controls. The sensitivity and specificity of both scanning methods were calculated.

RESULTS

FP-CIT SPECT and F-DOPA PET scans were both able to discriminate PD patients from healthy controls. For the early phases of the disease, sensitivity and specificity of the contralateral striatal and putaminal uptake of FP-CIT and F-DOPA was 100%. When only caudate uptake was considered, the specificities were 100% and 90% for FP-CIT and F-DOPA, respectively, while the sensitivity was 91% for both scanning techniques.

CONCLUSION

FP-CIT SPECT and F-DOPA PET scans are both able to diagnose presynaptic dopaminergic deficits in early phases of PD with excellent sensitivity and specificity.