Abstract

Twenty-one intracranial hemorrhagic lesions were imaged at 0.15 and 0.6 T using inversion recovery (IR), spin echo (SE), and multiple SE (Carr-Purcell-Meiboom-Gill, CPMG) pulse sequences. Two subarachnoid hemorrhages (SAH), nine acute intraparenchymal hemorrhages (IPH), ten chronic IPH, and one subdural hematoma were studied. Acute SAH could not be identified on the T1-weighted, IR images but was clearly seen on a T2-weighted, CPMG image. Acute (7 days or less) intraparenchymal hematoma showed signal intensity on IR and CPMG images similar to white matter. The T1 and T2 times of acute intraparenchymal hematoma were also similar to white matter. Some small acute hematomas could not be distinguished from white matter on IR and CPMG images. Acute hemorrhagic tissue showed image intensities and relaxation times similar to gray matter. All acute hemorrhages were identified on CT. Chronic IPH lesions (14 days or more) showed high signal intensity, greater than white matter, on IR, SE, and CPMG images. The T1 of the chronic lesions was similar to the acute lesions but T2 was significantly longer (p less than 0.05). Available evidence suggests that the nonspecificity of acute IPH signal and relaxation times may not be restricted to our pulse sequences or magnetic field strengths.