A diagnostic strategy for Parkinsonian syndromes using quantitative indices of DAT SPECT and MIBG scintigraphy: an investigation using the classification and regression tree analysis

Abstract

Purpose: We aimed to evaluate the diagnostic performances of quantitative indices obtained from dopamine transporter (DAT) single-photon emission computed tomography (SPECT) and ¹²³I-metaiodobenzylguanidine (MIBG) scintigraphy for Parkinsonian syndromes (PS) using the classification and regression tree (CART) analysis.

Methods: We retrospectively enrolled 216 patients with or without PS, including 80 without PS (NPS) and 136 with PS [90 Parkinson's disease (PD), 21 dementia with Lewy bodies (DLB), 16 progressive supranuclear palsy (PSP), and 9 multiple system atrophy (MSA). The striatal binding ratio (SBR), putamen-to-caudate ratio (PCR), and asymmetry index (AI) were calculated using DAT SPECT. The heart-to-mediastinum uptake ratio (H/M) based on the early (H/M [Early]) and delayed (H/M [Delay]) images and cardiac washout rate (WR) were calculated from MIBG scintigraphy. The CART analysis was used to establish a diagnostic decision tree model for differentiating PS based on these quantitative indices.

Results: The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 87.5, 96.3, 93.3, 92.9, and 93.1 for NPS; 91.1, 78.6, 75.2, 92.5, and 83.8 for PD; 57.1, 95.9, 60.0, 95.4, and 92.1 for DLB; and 50.0, 98.0, 66.7, 96.1, and 94.4 for PSP, respectively. The PCR, WR, H/M (Delay), and SBR indices played important roles in the optimal decision tree model, and their feature importance was 0.61, 0.22, 0.11, and 0.05, respectively.

Conclusion: The quantitative indices showed high diagnostic performances in differentiating NPS, PD, DLB, and PSP, but not MSA. Our findings provide useful guidance on how to apply these quantitative indices in clinical practice.

Keywords: 123I-FP-CIT; 123I-Ioflupane; Artificial intelligence; CART; Data mining.

Fig. 1

Flow diagram of patient inclusion. Abbreviations: DLB dementia with Lewy body, MSA multiple system atrophy, NPS non-Parkinsonian syndrome, PD Parkinson’s disease. PSP progressive supranuclear palsy

Fig. 2

Representative DAT SPECT and MIBG scintigraphy images. a A representative VOI setting of DAT SPECT. A commercially available software package DaTQUANT was used. b A representative ROI setting of MIBG scintigraphy. A commercially available software package smartMIBG was used. Abbreviations: DAT dopamine transporter, MIBG ¹²³I-metaiodobenzylguanidine, ROI region of interest, SPECT single-photon emission computed tomography, VOI volume of interest

Fig. 3

Box-and-whisker plots of the quantitative indices. Asterisks represent significant differences between patients’ groups (p < 0.05). Abbreviations: AI asymmetry index, DLB dementia with Lewy body, H/M heart-to-mediastinum activity uptake ratio, MSA multiple system atrophy, NPS non-Parkinsonian syndrome, PCR putamen-to-caudate ratio, PD Parkinson’s disease, PSP progressive supranuclear palsy, SBR striatal binding ratio, WR cardiac washout rate

Fig. 4

Optimal decision tree used to classify the patient groups. The bar graphs show the distribution of the patient groups at the optimal quantitative index in each node. The arrowheads in the bar graphs represent the cutoff values for each quantitative index. The pie charts represent the proportion of patients’ groups in terminal nodes. Abbreviations: AI asymmetry index, DLB dementia with Lewy body, H/M, heart-to-mediastinum activity uptake ratio, MSA multiple system atrophy, NPS non-Parkinsonian syndrome, PCR putamen-to-caudate ratio, PD Parkinson’s disease, PSP progressive supranuclear palsy, SBR striatal binding ratio, WR cardiac washout rate

Fig. 5

DAT SPECT images of representative cases of PD, DLB, PSP, and MSA. a A representative case of PD (aged 64 years, Female). b A representative case of DLB (aged 79 years, Female). c A representative case of PSP (aged 86 years, Female). d A representative case of MSA (aged 56 years, Male). Abbreviations: DLB dementia with Lewy body, MSA multiple system atrophy, PD Parkinson’s disease, PSP progressive supranuclear palsy