Table I.

Summary of scanner characteristics and acquisition parameters at each site

Site	Scanner	Acquisition data
			Voxel size (mm3)	FOV	Matrix	Pixel band width	TR (ms)	TE (ms)	Inversion time (ms)	Flip angle (°)
PHILIPS	Philips Gyroscan ACS 1.5 T	T1	1.0 × 1.0 × 1.5	256 × 256	256 × 256	NA	15.3	4.6	0	30
		T2	1.0 × 1.0 × 3.5	256 × 256	256 × 256	NA	5,809	120	—	90
GE_1	GE Genesis Signa 1.5 T	T1	0.98 × 0.98 × 1.5	250 × 250	256 × 256	122	10.9	4.6	300	20
		T2	0.98 × 0.98 × 3.5	250 × 250	256 × 256	122	5,800	126	—	90
GE_2	GE Genesis Signa 1.5 T	T1	0.98 × 0.98 × 1.5	250 × 250	256 × 256	122	12.1	5.2	300	20
		T2	0.98 × 0.98 × 3.5	250 × 250	256 × 256	122	5,800	126	—	90
SIEMENS_1	Siemens Symphony 1.5 T	T1	1.0 × 1.0 × 1.5	256 × 256	256 × 256	230	1,810	2.39	1,100	20
		T2	1.0 × 1.0 × 3.5	256 × 180	256 × 180	120	5,800	120	—	150
SIEMENS_2	Siemens Symphony 1.5 T	T1	0.98 × 0.98 × 2.0	256 × 250	256 × 256	130	2,020	5.04	1,100	15
		T2	1.0 × 1.0 × 3.5	256 × 192	256 × 192	100	5,800	116	—	150

All scans were obtained in axial orientation, using a 3D gradient echo acquisition technique for T1 weighted images, and spin‐echo sequence in the T2 weighted images, using the quadrate head coil. Neither parallel imaging (SENSE, iPAT, ASSET) sequences nor multichannel coils were used in any of the sites. By default, GE scanners have the gradient linearity correction filter activated, and thus scans from GE sites were acquired with this parameter.