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MR imaging of hemorrhagic conditions of the head and neck
R I Grossman1, J M Gomori, H I Goldberg
1Department of Radiology, Hospital of the University of Pennsylvania 19104.
Abstract:
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.
Insights
Magnetic resonance imaging (MRI) reveals distinct signal intensity patterns in hemorrhagic lesions. These patterns change over time due to hemoglobin degradation and biological factors, aiding diagnosis.
Area of Science:
- Neuroradiology
- Biochemistry
- Pathology
Background:
- Intraparenchymal hemorrhage diagnosis relies on understanding MRI signal characteristics.
- The evolution of hemorrhage appearance is influenced by hemoglobin breakdown products and biological factors.
Purpose of the Study:
- To define the characteristic signal intensity patterns of intraparenchymal hemorrhage on 1.5 T spin echo MRI.
- To correlate these patterns with the chemical degradation of hemoglobin and biological factors.
Main Methods:
- Analysis of 1.5 T spin echo MRI sequences in patients with intraparenchymal hemorrhage.
- Observation of signal intensity changes over different stages of hemorrhage (acute, early subacute, late subacute, chronic).
Main Results:
- Distinct, sequential signal intensity patterns were identified for acute, subacute, and chronic intraparenchymal hemorrhage.
- Signal changes are attributed to hemoglobin degradation products and influenced by factors like pO2, edema, hematocrit, and blood-brain barrier (BBB) integrity.
- Hemosiderin deposition, indicated by hypointensity on T2-weighted images, is observed in later stages and depends on BBB integrity.
Conclusions:
- MRI demonstrates a predictable sequence of signal intensity changes in intraparenchymal hemorrhage.
- Understanding these patterns aids in diagnosing various hemorrhagic conditions, including venous thrombosis and vascular malformations.