Faculty Bibliography

1. There is a constant sequence of signal intensity patterns that characterize 1.5 T, spin echo MR images of hemorrhagic lesions. 2. The MRI appearance of intraparenchymal hemorrhage is determined by the sequential chemical degradation of Hb, by the paramagnetic properties of the degradation products and by certain biologic factors including pO2, edema formation, hematocrit and BBB. 3. Acute intraparenchymal hemorrhage is characterized by markedly diminished signal intensity centrally relative to surrounding white matter (hypointensity) on T2 weighted images and often by a moderately increased signal intensity (hyperintensity) of the adjacent white matter produced by surrounding edema on proton density and T2 weighted images. 4. Early subacute intraparenchymal hemorrhage is characterized centrally by moderate hypointensity on T2 weighted images, and peripherally, by moderate hyperintensity on T1 weighted and marked hypointensity on T2 weighted images. Hyperintensity on proton density and T2 weighted images of nearby white matter owing to edema may again be seen. 5. Late subacute intraparenchymal hemorrhage is characterized by marked peripheral and central hyperintensity on both T1 and T2 weighted images. Also, marked hypointensity of the adjacent brain rim on T2 weighted images owing to hemosiderin deposition may be seen. 6. Chronic intraparenchymal hemorrhage is characterized by marked hyperintensity both centrally and peripherally on both T1 and T2 weighted images and by marked hypointensity of the adjacent brain rim on T2 weighted images owing to hemosiderin deposition. Surrounding edema is no longer present. 7. The integrity of the blood-brain barrier appears to be important in determining whether or not hemosiderin accumulations consistently occur in subacute and chronic hemorrhage. 8. Hemorrhagic conditions in which the defined sequence of signal intensity patterns may be seen include: venous thrombosis, hemorrhagic infarction, occult vascular malformation and intracranial aneurysm

The sequential degradation of hemoglobin in an evolving hemorrhage has been reviewed. Physical mechanisms of proton relaxation enhancement that contribute to the clinical MR appearances of hemorrhage have been described, and the dependence of relaxation rates on field strength and interecho interval in spin-echo imaging techniques has been defined

One hundred intracranial hematomas aged 1 day to greater than 4 years old were imaged at 1.5 Tesla using T1- and T2-weighted spin-echo pulse sequences. Characteristic intensity patterns seen in the evolution of hematomas were identical to those preliminarily reported in 20 hematomas. They allow staging of a hematoma into acute (less than 1 week old), subacute (between 1 week and 1 month old), and chronic (several months to several years old). The mechanisms suspected to be responsible for these intensity patterns were confirmed by in vitro nuclear magnetic relaxometry of blood, ferritin and hemosiderotic spleen samples performed on a variable field spectrometer at 0.19 to 1.4 Tesla. High-field magnetic resonance imaging is sensitive and specific for hemorrhage in all of its stages of evolution as well as to the ambient oxygen tension of acute hematomas

Retinoblastoma is a highly curable tumor unless extraocular extension or metastases have occurred. Intracranial retinoblastoma metastases usually result from either contiguous or hematogenous spread and are rapidly fatal. We report two cases of pathologically proven, hemorrhagic intracranial retinoblastoma metastases and correlate magnetic resonance images with pathologic findings. Magnetic resonance with its high sensitivity and specificity for blood extravasation can document the associated hemorrhagic component of the tumor and help in the differentiation of nonmetastatic second neoplasms in retinoblastoma patients

To determine the relationship between MR relaxation times and the iron content of the spleens in patients with thalassemia, we measured these parameters at 0.19 and 1.18 T in 19 thalassemic spleen specimens in vitro. The correlation was best between iron content and the dependence between the interecho interval and the 1/T2 (T2 relaxation rate) at 1.18 T(r = .9361, p less than .001). No statistically significant correlation was found between T1 and iron content at either field strength. The variation of the 1/T2 with interecho interval may be useful for measuring iron content in vivo. It supports the theory that the T2 relaxation of iron deposits occurs via cellular field gradients produced by intralysosomal granules of hemosiderin

Facial nerve paresis is rarely seen in dural cavernous sinus arteriovenous malformations or carotid-cavernous sinus fistulae. A patient with an otherwise typical presentation of a spontaneous carotid-cavernous sinus malformation was found to have ipsilateral infranuclear facial nerve paresis. Angiography revealed a dural arteriovenous malformation with early petrosal sinus filling. Possible mechanisms for the paresis include compression of the facial nerve by increased venous pressure and 'stealing' of the arterial supply by the malformation

A case report of an 11 years old boy with new onset of a seizure disorder is presented. A computed tomography scan demonstrated a noncalcified, nonenhancing focal region of abnormal cortex. A magnetic resonance imaging scan delineated both an isointense area of abnormally thickened gyri and linear areas of abnormal high signal intensity in the subjacent white matter. A review of the radiologic and pathologic literature suggests that this lesion represents the entity focal cortical dysplasia as described by Taylor, et al. This abnormality is part of a spectrum of disorders including hamartomas (of tuberous sclerosis), focal cortical dysplasia and heterotopias

Sixteen patients with multiple sclerosis were evaluated by magnetic resonance imaging (MRI) to determine if number of brain lesions correlated with the amount of functional disability, as described by the Incapacity Status Scale contained in the Minimal Record of Disability. Although no correlation existed, the statistical analysis did indicate a trend toward correlation, which warrants a study with a larger number of subjects

Fast low-angle multiecho (FLAME) imaging uses partial flip angles of less than 90 degrees with 180 degrees radiofrequency refocusing pulses. The partial flip angle permits imaging with shorter repetition time (TR) values on the order of 750-1,000 ms for 30 degrees angles with image contrast characteristics identical to those obtained with conventional 90-180 degrees schemes and TRs on the order of 2,500 ms. The approximately threefold reduction in imaging time is accompanied by a decrease in signal-to-noise ratio. In many circumstances, however, this trade-off may produce entirely acceptable images of the CNS at a significant reduction in imaging time