Predicting cerebral ischemic infarct volume with diffusion and perfusion MR imaging

Abstract

Background and purpose: Diffusion and perfusion MR imaging have proved useful in the assessment of acute stroke. We evaluated the utility of these techniques in detecting acute ischemic infarction and in predicting final infarct size.

Methods: Diffusion and hemodynamic images were obtained in 134 patients within a mean of 12.3 hours of onset of acute ischemic stroke symptoms. We retrospectively reviewed patient radiology reports to determine the presence or absence of lesion identification on initial diffusion- (DW) and perfusion-weighted (PW) images. Radiologists were not blinded to the initial clinical assessment. For determination of sensitivity and specificity, the final discharge diagnosis was used as the criterion standard. Neurologists were not blinded to the DW or PW imaging findings. In 81 patients, acute lesions were compared with final infarct volumes.

Results: Sensitivities of DW imaging and cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) perfusion parameters were 94%, 74%, 84%, and 84%, respectively. Specificities of DW imaging, CBV, CBF, and MTT were 96%, 100%, 96%, and 96%, respectively. Results were similar in 93 patients imaged within 12 hours. In 81 patients with follow-up, regression analysis yielded r(2) = 0.9, slope = 1.24 for DW imaging; r(2) = 0.84, slope = 1.22 for CBV; r(2) = 0.35, slope = 0.44 for CBF; and r(2) = 0.22, slope = 0.32 for MTT, versus follow-up volume. A DW-CBV mismatch predicted additional lesion growth, whereas DW-CBF and DW-MTT mismatches did not. Results were similar in 60 patients imaged within 12 hours.

Conclusion: Diffusion and hemodynamic images are sensitive and specific for detecting acute infarction. DW imaging and CBV best predict final infarct volume. DW-CBV mismatch predicts lesion growth into the CBV abnormality. CBF and MTT help identify additional tissue with altered perfusion but have lower correlation with final volume.

Fig 1.

A–D, Scatterplots demonstrate initial lesion volume with each technique versus final lesion volume at follow-up (F-U) in 81 patients. A, Initial DW imaging versus follow-up: r² = 0.9, slope = 1 .24 ± 0.08 (95% confidence limits). B, Initial CBV versus follow-up: r² = 0.84, slope = 1 .22 ± 0.11. C, Initial CBF versus follow-up: r² = 0.35, slope = 0.44 ± 0.09. D, Initial MTT versus follow-up: r² = 0.22, slope = 0.32 ± 0.08. r² indicates coefficient of determination.

Fig 2.

A–F, Scatterplots show initial lesion volume versus final infarct volume in patients with a perfusion-diffusion mismatch (perfusion lesion more than 20% larger than the diffusion lesion). A and B, DW-CBV mismatch group: For DW imaging versus follow-up, the regression line was significantly different from the line of identity (P < .001). For CBV versus follow-up, the regression line was not significantly different from the line of identity (P = .18). C and D, DW-CBF mismatch group: For DW imaging versus follow-up and for CBF versus follow-up, the line of regression was significantly different from the line of identity (P < .001). E and F, DW-MTT mismatch group: For DW imaging versus follow-up and for MTT versus follow-up, the line of regression was significantly different from the line of identity (P < .001). r² indicates coefficient of determination.

Fig 3.

A, Axial DW image demonstrates an infarct involving the left basal ganglia, insula, and subinsular region. B, CBV map shows the lesion is larger than the initial DW imaging abnormality; it also involves the left frontal and parietal opercula. C and D, CBF (C) and MTT (D) abnormalities involve most of the left middle cerebral artery distribution. E, Follow-up (F/u) T2-weighted image 10 days later demonstrates a lesion similar in size to that of the initial CBV abnormality (B).

Fig 4.

Percentage of patients with diffusion-perfusion mismatches for proximal (black bars) and nonproximal (white bars) infarctions.