High b-value diffusion tensor imaging of unilateral middle cerebral artery occlusive disease: evaluation of white matter injury

Abstract

Objective To investigate the value of diffusion tensor imaging (DTI) at high b value for unilateral middle cerebral artery (MCA) occlusive disease in patients without obvious infarct lesions on conventional MR imaging.Methods DTI at high b value (2200 s/mm2 ) was performed using a 3.0 Tesla MR scanner in 34 patients with unilateral middle cerebral artery occlusion,who had no obvious infarct lesions on conventional MR imaging. Fractional anisotropy (FA),apparent diffusion coefficient (ADC),axial diffusivity (eigenvalue λ1) and radial diffusivity (eigenvalues λ2,λ3) were measured at the ipsilateral and contralateral corona radiata,anterior and posterior limbs of the internal capsule,cerebral peduncle and pons in all subjects.Mean ADC,FA,λ1,λ2 and λ3 values of corona radiata,anterior and posterior limbs of the internal capsule,cerebral peduncle and pons were compared between the ipsilateral and contralateral MCA territory by t test. Results Among the 34 patients,left MCA occlusion in M1 segment occurred in 16 patients and right MCA occlusion in Ml segment occurred in 18 patients.At the ipsilateral corona radiata,mean FA,ADC,λ1,λ2 and λ3 were 0.419 ±0.032,(5.975 ±0.272) × 10 3,(5.704 ±0.365) ×10-3,(6.412 ±0.368) × 10-3 and (6.605 ±0.343) × 10-3 mm2/s,respectively.At the contralateral corona radiata,mean FA,ADC,λ1,λ2 and λ3 were 0.443 ± 0.033,(5.804 ± 0.282) × 10 -3,(5.651 ±0.350) × 10-3,(6.099 ±0.353) × 10-3 and(6.372 ±0.355) × 10-3 mm2/s,respectively.At the ipsilateral corona radiata,mean FA was significantly decreased(t =11.614,P ＜0.01),and mean ADC (t=12.421,P＜0.01),λ1(t =7.447,P＜0.01),λ2(t=10.244,P＜0.01) and λ3(t=9.890,P＜0.01) were significantly increased.At the ipsilateral anterior and posterior limb of the internal capsule,mean FA were 0.609 ±0.026 and 0.674 ±0.033,λ1 were(5.330 ±0.462) × 10 -3 and(5.171 ±0.456) ×10-3 mm2/s,respectively.At the contralateral anterior and posterior limb of the internal capsule,FA were 0.622 ±0.026 and 0.694 ±0.034,λ1 were(5.064 ± 0.448) × 10 -3 and(4.924 ± 0.365) × 10 -3 mm2/s,respectively.Mean FA was significantly decreased (t =7.823,8.013,all P ＜ 0.01) and mean λ1 was significantly increased (t =7.811,8.800,all P ＜0.01) at the ipsilateral anterior and posterior limbs of the internal capsule.There was no significant difference in ADC,λ2 and λ3 value between the ipsilateral and contralateral sides.And all the DTI parameters,including mean ADC,FA,λ1,λ2 and λ3 values,showed no statistical difference between both sides of cerebral peduncle and pons.Conclusion DTI at high b valuc can provide useful information for visualizing ischemic white matter injury in patients without obvious infarct lesions on conventional MR imaging. Key words: Infarction, middle cerebral artery; Diffusion magnetic resonance imaging