Differences of Various Region-of-Interest Methods for Measuring Dopamine Transporter Availability Using ^𝟗𝟗𝐦𝐓𝐜-TRODAT-1 SPECT

Table 3

Striatal DAT availabilities, declines per decade of DAT availabilities, and striatum sizes in the transverse slices of the striatum ROIs defined by the atlas approaches.

Transverse slices**	MRI-normalization			SPECT-normalization
	Average***	Decline per decade	Average size*	Average***	Decline per decade	Average size*
≤(OM𝑧) − 2	1.46	5.12%	68.4	1.54	4.15%	78.3
(OM𝑧) − 1	1.78	6.19%	57.7	1.86	5.74%	67.4
(OM𝑧)	1.76	7.67%	76.4	1.81	7.17%	87.2
(OM𝑧) + 1	1.64	8.30%	89.8	1.66	8.04%	97.1
(OM𝑧) + 2	1.44	9.41%	92.7	1.47	8.89%	94.3
(OM𝑧) + 3	1.21	10.34%	87.5	1.25	10.29%	80.7
(OM𝑧) + 4	0.99	11.56%	73.8	1.04	11.51%	60.8
(OM𝑧) + 5	0.79	11.84%	56.9	0.85	12.70%	41.2
≥(OM𝑧) + 6	0.58	14.42%	77.4	0.68	11.91%	30.4

∗Voxels: each voxel is of 2.897 mm × 2.897 mm × 2.897 mm.
^∗∗OM_𝑧: the 𝑧 axis of the OC mark is at the transverse slice with the largest striatum area.
∗∗∗For comparisons, the same OC averages from the threshold-ROI methods were used in the calculation of (ST-OC)/OC.