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Comparative Study
. 2004 Jun-Jul;25(6):939-44.

Comparison of CT and three MR sequences for detecting and categorizing early (48 hours) hemorrhagic transformation in hyperacute ischemic stroke

Marie-Cécile Arnould  1 , Cécile B Grandin, André Peeters, Guy Cosnard, Thierry P Duprez
Affiliations
Comparative Study

Comparison of CT and three MR sequences for detecting and categorizing early (48 hours) hemorrhagic transformation in hyperacute ischemic stroke

Marie-Cécile Arnould et al. AJNR Am J Neuroradiol. 2004 Jun-Jul.

Abstract

Background and purpose: Our goal was to compare the sensitivity of CT and three MR sequences in detecting and categorizing early (48 hours) hemorrhagic transformation (HT) in hyperacute ischemic stroke.

Methods: Twenty-five consecutive patients with hyperacute ischemic stroke (<6 hours) without MR signs of cerebral bleeding at admission were included. Twenty-one underwent thrombolytic therapy. A standardized follow-up protocol, performed 48 hours after admission, combined brain CT scan and MR examination (1.5 T) including fast spin-echo-fluid-attenuated inversion recovery (FSE-FLAIR), echo-planar spin-echo (EPI-SE) T2-weighted, and EPI-gradient-recalled echo (GRE) T2*-weighted sequences. Both CT scans and MR images were obtained within as short a time span as possible between techniques (mean delay, 64 minutes). CT scans and MR images were independently rated as negative or positive for bleeding and categorized for bleeding severity (five classes) by two blinded observers. Prevalence of positive cases, intra- and interobserver agreement, and shifts in bleeding categorization between respective modalities and sequences were assessed.

Results: Twelve patients (48%) were rated positive for HT on the basis of findings of at least one technique or sequence. From this subset of bleeding patients, seven (58%) had positive CT findings, nine (75%) had positive FSE-FLAIR and EPI-SE T2-weighted findings, and 12 (100%) had positive EPI-GRE T2*-weighted findings. CT had lower intra- and interobserver agreement for positivity than did MR imaging. Among the seven patients with positive CT and MR findings, only two had convergent ratings for bleeding category based on findings of two modalities. The five remaining had upward grading from CT to MR, which varied according to pulse sequence.

Conclusion: MR imaging depicted more hemorrhages and had higher intra- and interobserver agreement than did CT. The EPI-GRE T2*-weighted sequence demonstrated highest sensitivity. Equivocal upward shifts in bleeding categorization were observed from CT to MR imaging and between MR images.

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Figures

F<sc>ig</sc> 1.
Fig 1.
Increased conspicuity of HT and upgrade in bleeding categorization at 24 hours by using the different sequences. The patient is a 75-year-old woman admitted 24 hours previously for aphasia, right hemiparesis, and right conjugate ocular deviation who was treated by a combination of 450 mg ASA and low-dose low molecular heparinoids. A, Axial CT scan, showing an ambiguous isoattenuated area within infarcted left PCA territory, which was ultimately rated as “HI1” after extended debate. The hemorrhagic area displays a similar attenuation as the normal parenchyma raising the hypothesis of spared tissue rather than petechial HT. Consensual interobserver rating of “HI2” was retained. B, FSE-FLAIR image, showing punctuate hypointense foci confirming petechial hemorrhage and the “HI2” rating. C, EPI-SE T2-weighted image, demonstrating homogeneous, round hypointense area rated as “PH1” because of the clotlike aspect of the bleeding, without mass effect but with the presence of a surrounding hyperintense ring of ischemic tissue. D, EPI-GRE T2*-weighted image, demonstrating enlargement of the hemorrhagic area resulting in “PH2” rating since the hypointense artifact had recovered the ring of hyperintense ischemic tissue seen on FSE-FLAIR and EPI-SE T2-weighted images (previous views), thereby filling the theoretical >30% of infarct area criterion for “PH2” rating.
F<sc>ig</sc> 2.
Fig 2.
EPI-GRE T2*-weighted sequence as the only positive technique for the 24-hour detection of post-thrombolytic petechial hemorrhage in an 86-year-old man admitted 24 hours previously and treated with 58 mg r-tPA IV 110 minutes after the onset of a left hemiplegia (NIH stroke score on admission, 13). A, CT scan, showing a large acute hypoattenuated area within the MCA territory without sign of fresh blood extravasation. B, FSE-FLAIR image, showing uniform hyperintensity within the ischemic area without hypointense hemorrhagic focus. C, EPI-SE T2-weighted image, showing similar findings of positivity for ischemia and negativity for HT as in previous 3B image. D, EPI-GRE T2*-weighted image, showing hypointense susceptibility artifact within both putamen and globus pallidus, revealing confluent petechiae. The extravasation was rated “HI2.”
F<sc>ig</sc> 3.
Fig 3.
Discrepancy in CT and MR results between infarcted subareas in a 74-year-old woman admitted 24 hours previously and treated by 67 mg of rt-PA administered intravenously 185 minutes after the sudden onset of a left hemiplegia (NIH stroke score on admission, 14) A, axial CT scan through the thalamic level shows a round area of isoattenuation relative to normal brain surrounded by ischemic edema within the lenticulate nucleus, which was rated confluent petechial “HI2” after intra- and interobserver controversies (similar to the previous case). B, EPI-GRE T2*-weighted MR image in the similar location as Fig 2A, confirming the presence of freshly extravasated blood. C, Axial CT scan through an upper level, showing homogeneous ischemic hypoattenuation without hyperattenuated focus suggesting HT. D, EPI-GRE T2*-weighted MR image in the similar location as Fig 2C, disclosing unsuspected subependymal hemorrhagic focus.
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