Nigrostriatal Dopamine Terminal Imaging with Dopamine Transporter SPECT: An Update

Abstract

Learning Objectives: On successful completion of this activity, participants should be able to describe (1) the radiopharmaceuticals used to evaluate nigrostriatal dopamine imaging; (2) the pattern of uptake of these radiopharmaceuticals in parkinsonian syndromes; and (3) the role of these radiopharmaceuticals in the evaluation of parkinsonian syndromes.Financial Disclosure: Dr. Tatsch is a meeting participant/lecturer for GE Healthcare. The authors of this article have indicated no other relevant relationships that could be perceived as a real or apparent conflict of interest. CME Credit: SNMMI is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to sponsor continuing education for physicians. SNMMI designates each JNM continuing education article for a maximum of 2.0 AMA PRA Category 1 Credits. Physicians should claim only credit commensurate with the extent of their participation in the activity. For CE credit, participants can access this activity through the SNMMI Web site (http:// www.snmmi.org/ce_online) through August 2016.This article gives an update on nigrostriatal dopamine terminal imaging, with emphasis on SPECT performed with the presynaptic dopamine transporter (DAT) ligand 123 I-FP-CIT. The paper covers the rational use of this technique in the diagnostic work-up of patients with known or suspected parkinsonian syndromes. In detail, it addresses the impact of the method for the proof or exclusion of neurodegenerative parkinsonism, for its early and preclinical diagnosis, and for the evaluation of disease progression. The importance of normal DAT binding for differentiating symptomatic parkinsonism and relevant tremor syndromes from neurodegeneration is highlighted. Particularly emphasized is the role of DAT SPECT for diagnosing Lewy body dementia and its separation from Alzheimer dementia. Finally, some remarks deal with the economic aspects of the use of these imaging techniques in the clinical setting.

Quantitative Intensity Harmonization of Dopamine Transporter SPECT Images Using Gamma Mixture Models

“…Results: Raw striatal intensities and SBR values presented significant differences across distinct camera models. We demonstrate that GCDF normalization efficiently alleviated these differences in striatal quantification and with values constrained to a fixed interval [0,1]. Also, our method allowed a fully automated image assessment that provided maximal classification ability, given by an area under the curve (AUC) of AUC = 0.94 when used mean regional variables and AUC = 0.98 when used voxel-based variables.…”

“…Then, as a proof-of-concept example, we evaluate the performance of a binary classifier based on logistic regression to distinguish between healthy controls and PD after GCDF normalization when images from multiple sites were pooled together. As a reference, previous single-center studies have demonstrated that the diagnostic accuracy of visual expert reading or SBR-based classifiers can be as high as of 95 % [1,4]. We evaluated a low dimensional classifier using striatal ROI variables (bilateral putamen and caudate) and also a higher dimensional one using all striatal voxels; in both cases we used a logistic regression classifier and tenfold cross-validation for evaluation.…”

“…The imaging of the dopamine transporter (DAT) with nuclear medicine techniques, such as single-photon emission computed tomography (SPECT) or positron emission tomography (PET), is a very useful and widespread tool for the diagnosis of Parkinson's disease (PD) and other neurodegenerative parkinsonisms [1]. In these diseases, there is a progressive degeneration of the dopaminergic neurons in the nigrostriatal pathway, which projects from the substantia nigra to the striatum.…”

“…More specifically, our method consists of a reparametrization of the voxel values according a mixture model of two Gamma distributions fitting a normative image histogram. Such reparametrization is based on the cumulative density function of the Gamma component modeling the specific uptake so that the new feature space is constrained to the interval [0,1].…”

What can imaging tell us about cognitive impairment and dementia?

“…Low dopamine transporter uptake in basal ganglia demonstrated by SPECT or PET imaging is the only imaging feature in the diagnostic criteria for LBD [79] . However, FP-CIT SPECT is not indicated to distinguish between different parkinsonian syndromes [93] . FP-CIT SPECT scan has a sensitivity of 78% and a specificity of 90% with an overall accuracy of 80% to distinguish between normal (or AD) and a parkinsonian syndrome (LBD) [94] .…”