Comparative Study of MRI Biomarkers in the Substantia Nigra to Discriminate Idiopathic Parkinson Disease

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Fig 1.
Segmentation of ROIs. Axial brain stem slices in a healthy volunteer (A) and a patient with Parkinson disease (B) show reduction of the neuromelanin signal intensity in the substantia nigra of the patient. Axial T2*WI 7T slices show dorsal nigral hyperintensity in a HV (C), which is absent in the patient with PD (D). T2WI axial (E) and coronal (F) images of the SN in a HV show T2-based segmentation of the SN.
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Fig 2.
Boxplot of the 3T NM SN volume (cubic millimeters) (A) and signal intensity ratio (B) (calculated by normalizing the mean signal of the SN in each slice to the signal in the background region), the 3T NM FA (C), and the 7T T2*WI SN volume (D) shows a reduction in all measures in patients with PD compared with HVs.
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Fig 3.
Receiver operating characteristic curves of the 3T NM volume, the 3T NM signal intensity ratio, the 3T NM FA, the 7T T2* volume (A), and the combination of the first 3 biomarkers for differentiating patients with PD from HVs (B).

Table 1:

Quantitative measurements in the SN^{^a}

Note:—L indicates left; R, right; LR, average of left and right.
↵a Quantitative measurements in the substantia nigra (mean and SD) are presented.
↵b Significant differences between patients with PD and HVs are indicated using P < .001.
↵c Significant differences between patients with PD and HVs are indicated using P < .05.
↵d Significant differences between patients with PD and HVs are indicated using P < .005.

Table 2:

Diagnostic accuracy of quantitative and qualitative (visual) assessments

	Sensitivity	Specificity	PPV	NPV	AUC (95% CI)	Diagnostic Accuracy	Cutoff
Quantitative measurements
3T NM signal	0.88	0.8	0.88	0.8	0.88 (0.79–0.97)	0.86	110.35
Volume	1	0.72	0.86	1	0.86 (0.76–0.95)	0.89	200.02
7T T2*WI volume	0.65	0.72	0.82	0.54	0.69 (0.53–0.84)	0.68	498.70
Diffusion measures
FA 3T NM	0.75	0.53	0.75	0.55	0.68 (0.54–0.82)	0.68	0.33
3T T2WI	0.65	0.70	0.8	0.52	0.64 (0.5–0.79)	0.66	0.37
AD 3T NM	0.7	0.65	0.78	0.54	0.73 (0.59–0.87)	0.68	0.64
3T T2WI	0.61	0.75	0.81	0.52	0.65 (0.49–0.80)	0.66	0.5
RD 3T NM	0.64	0.75	0.82	0.54	0.72 (0.58–0.86)	0.67	0.43
3T T2WI	0.72	0.6	0.76	0.55	0.68 (0.52–0.83)	0.67	0.29
MD 3T NM	0.67	0.75	0.83	0.56	0.72 (0.58–0.87)	0.7	0.51
3T T2WI	0.64	0.75	0.82	0.54	0.67 (0.53–0.82)	0.67	0.38
Combined measurements
NM signal and volume + FA (3T NM)	0.92	0.95	0.97	0.86	0.96 (0.9–1)	0.93	4.4
Qualitative evaluation
NM at 3T	0.83	0.9	0.94	0.9	–	0.86	–
DNH at 7T
Method 1	0.97	0.8	0.9	0.94	–	0.91	–
Method 2	0.94	0.85	0.92	0.9	–	0.91	–