Usefulness of Subtraction of 3D T2WI-DRIVE from Contrast-Enhanced 3D T1WI: Preoperative Evaluations of the Neurovascular Anatomy of Patients with Neurovascular Compression Syndrome

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Fig 1.
Method of image postprocessing. The first set of 3D T2WI-DRIVE source images (B) is subtracted from the second set of 3D CE T1WI (A) on a pixel-by-pixel basis by using workstations provided by the MR imaging system manufacturer. Then a third set of subtracted source images named sDRICE (C) is produced.
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Fig 2.
Comparison between the black/white-reversed 3D T2WI-DRIVE (A, C, E) and sDRICE images (B, D, F) at the NVC (arrow) in patients with HFS. In patients 1 (A and B) and 2 (C and D), the sDRICE images (B and D) clearly show that the offending vessel invaginates into the brain stem and compresses the root exit zone of CN VII, in contrast to the 3D T2WI-DRIVE images (A and C). In patient 6 (E and F), both images clearly show that the posterior cerebral artery compresses CN VII.
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Fig 3.
Comparison between the black/white-reversed 3D T2WI-DRIVE (A and C) and sDRICE images (B and D) at the NVC (arrow) in patients with TN. In patient 7 (A and B), the sDRICE image (B) clearly shows that the offending vessel (the petrosal vein) invaginates into CN V, in contrast to 3D T2WI-DRIVE (A). In patient 10 (C and D), the offending vessel is relatively easily discriminated from CN V even on 3D T2WI-DRIVE (D).

Table 1:

Patient data and outcomes

Patient No.	Age (yr)/Sex	Disease	Side	Offending Vessel	Result	Complication
1	46/F	HFS	R	AICA-PICA	Cure	No
2	30/M	HFS	L	VA, AICA	Cure	No
3	53/F	HFS	L	PICA	Cure	No
4	60/M	HFS	L	VA, AICA	Cure	No
5	40/F	HFS	L	PICA	Cure	No
6	50/M	HFS	L	AICA	Cure	No
7	57/F	TN	L	Petrosal vein	Cure	No
8	61/F	TN	R	SCA	Cure	No
9	62/F	TN	L	SCA	Cure	No
10	74/F	TN	R	SCA	Cure	No
11	64/F	TN	L	SCA, AICA	Cure	No
12	33/F	TN	L	VA	Cure	No

Note:—AICA indicates anterior inferior cerebellar artery, PICA, posterior inferior cerebellar artery; SCA, superior cerebellar artery; VA, vertebral artery.

Table 3:

Qualitative and quantitative analyses of 3D T2WI-DRIVE and sDRICE images

Parameter	3D T2WI-DRIVE	sDRICE	P Value
Lesion conspicuity on the neurovascular contact point^{^a}
Rater 1
Overall (N = 12)	2.0 (1–3)	3.0 (2–3)	.006
HFS (n = 6)	1.5 (1–2)	3.0 (3–3)	.023
TN (n = 6)	2.5 (1–3)	3.0 (2–3)	.102
Rater 2
Overall (N = 12)	2.0 (1–3)	3.0 (2–3)	.004
HFS (n = 6)	1.5 (1–2)	3.0 (2–3)	.038
TN (n = 6)	2.0 (1–3)	3.0 (3–3)	.038
Contrast (N = 12)^{^b}
Vessel/nerve	−1.21 ± 0.72	0.28 ± 0.15	<.001
Vessel/brain stem	−1.08 ± 0.67	0.17 ± 0.88	<.001
CNR (N = 12)^{^b}
Vessel/nerve	−1.80 ± 1.47	3.34 ± 1.99	.007
Vessel/brain stem	−0.97 ± 0.58	2.25 ± 1.57	.003

↵a Scoring data are listed for both raters as rater 1/rater 2 and correspond to the median (with range) across patients. P values were calculated with the Wilcoxon signed rank test.
↵b Contrast and CNR data are means ± SD. The P values were calculated with a paired t test. Contrast_a/b = 2(SI_a − SI_b)/(SI_a + SI_b), and CNR_a/b = (SI_a − SI_b)/SD_a.