Abstract
BackgroundDopamine transporter (DaT) 123I–FP-CIT scans most commonly are interpreted visually. Alternatively, absolute quantitation of radiopharmaceutical uptake may improve scan accuracy. However, neither approach accomodates dependence of striatal uptake on age and gender. We investigated whether demographic indexing of visual and numerical variables improve discrimination of patients with essential tremor (ET), Parkinson’s disease (PD), and dementia with Lewy bodies (DLB).MethodsData of 132 consecutive patients undergoing DaT SPECT scans were reviewed retrospectively. The clinical impression in the latest neurology note was utilized as the final clinical diagnosis. Caudate and putamen specific binding ratio (PSBR) were computed. 123I calibration phantoms were constructed to enable absolute quantitation of putamen radiopharmaceutical uptake. A single experienced nuclear medicine physician graded visual certainty on a 3-level scale. Demographic indexing normalized metrics to published normal PSBR values. Methods were compared by simultaneous ROC analyses to identify the technique of maximal accuracy.ResultsThirty-four patients (26%) were diagnosed with ET, 85 (64%) with PD, 6 (5%) with multiple system atrophy, and 7 (5%) with DLB. For discriminating DLB from PD, visual analysis was significantly less specific and accurate than the other techniques. However, indexing significantly improved specificity and accuracy of visual scores, such that indexed visual scores were statistically equivalent to all other methods. Indexed PSBR yielded essentially the same results as non-indexed PSBR, for which highest overall test efficacy was achieved.ConclusionsOur results in this small series of patients with DLB suggest that if 123I–FP-CIT visual scores are to be used to discriminate DLB from other neurologic disorders, demographic indexing should be applied. However, best results overall are obtained using quantified parameters, regardless of whether or not demographic indexing is applied to these values.
Highlights
Dopamine transporter (DaT) 123I–flouropropyl-2b-carbomethoxy-3b-(4-iodophenyl) nortropane (FP-CIT) scans most commonly are interpreted visually
All data were handled in compliance with the Health Insurance Portability and Accountability Act of 1996
Neither demographic indexing nor use of absolute quantitation improved ability to discriminate patients with dementia with Lewy bodies (DLB) compared to conventional putamen specific binding ratios
Summary
Dopamine transporter (DaT) 123I–FP-CIT scans most commonly are interpreted visually. Absolute quantitation of radiopharmaceutical uptake may improve scan accuracy. We investigated whether demographic indexing of visual and numerical variables improve discrimination of patients with essential tremor (ET), Parkinson’s disease (PD), and dementia with Lewy bodies (DLB). Dopamine transporter (DaT) 123I–ioflupane scans are performed to help discriminate patients with essential tremor (ET), for which radiopharmaceutical uptake is intense and symmetric in caudate and putamen structures, from patients with Parkinson’s. FP-CIT binds to DaT, a presynaptic protein in nigrostriatal neurons responsible for dopamine reuptake from the synapatic cleft. Nigrostriatal neuronal dysfunction or loss of substantia nigra neuronal cell bodies results in reduced binding of FP-CIT (Walker & Walker, 2009). In Parkinson’s disease, loss of dopaminergic activity is progressive and first occurs in the contralateral putamen (Marshall & Grosset, 2003)
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