CT PROGRESSION OF INTRACRANIAL HEMATOMA (change from HYPER- to HYPO- dense over time) Initially – 60 – 90 Hounsfield Units (HU) 2 days – 70 HU 3 weeks – 30 HU >5 weeks – <30 HU 20% show enhancing rim at 2-6 weeks

MRI APPEARANCE OF INTRAPARENCHYMAL HEMATOMA (T1/T2: II, ID, BD, BB, DD (I-iso, D-dark, B-bright) Hyperacute – minutes to hours (DD => II) – T1WI – hematoma hypointense (deoxyHb) => isointense – T2WI – hematoma hypointense (deoxyHb) => isointense Acute – 0-2 days (ID => BD) – deoxyhemoglobin in intact RBCs with surrounding edema – T1WI – hematoma isointense, low signal intensity (SI) edema – T2WI – hematoma decreased SI at center, high SI edema Subacute – 2-14 days (BB) – deoxyhemoglobin changes to methemoglobin from outer to inner – T1WI – outer core shows increased SI – T2WI – Outer core shows increased SI due to shortened T1, longer T2 Chronic – 14 days (BB => DD) – hemosiderin laden macrophages at periphery – T1WI – inner core now also increased SI, rim has low SI – T2WI – inner core also has increased SI, rim has low SI Chronic – months later (DD) – hemosiderin laden macrophages at periphery – T1WI – mostly iso-/decreased SI, rim has lower SI – T2WI – markedly hypointense rim has low SI – “blooms” with greater T2-weighting COMMENT: T1WI = T 1 weighted image T2WI = T 2 weighted image SI = signal intensity

CT PROGRESSION OF ISCHEMIC INFARCT Initially – 30 HU 1 day – <30 HU Enhance ~3 days till 6 weeks Mass effect peaks at 3-5 days – seen in 20 % of ischemic infarcts – a significant mass effect is a poor prognostic sign After 8th week – 50% have "negative mass effect" (atrophy)



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