Approaches to Interpretation of MRI

      Head

      Time Substance T1W T2W
      Hyperacute (< 12 hrs) oxy-Hb isointense hyperintense
      Acute (12 hrs - 3 days) deoxy-Hb isointense hypointense
      Early subacute (4 days - 1 wk) intracellular met-Hb hyperintense hypointense
      Late subacute (1 wk - 1 month) extracellular met-Hb hyperintense hyperintense
      Chronic (> 1 month) hemosiderin, ferritin hypointense hypointense

      DWI ↑

      & ADC ↑

        Vasogenic edema
        T2 shine-through

      & ADC ↓
        Cytotoxic edema, e.g. acute ischemic stroke
        Diffuse axonal injury
        Abscess
        Cerebritis
        Epidermoid

        T1 ↑ T1 ↓ T1 ?
      T2 ↑ gad
      EC met-Hb
      hemangioma       		water
      metastasis       		oxy-Hb
      T2 ↓ flow (AVM, aneurysm)
      dural calcifn
      IC met-Hb       		cortical bone
      fibrous tissue
      hemosiderin, ferritin       		deooxy-Hb
      T2 ? fat (lipoma, dermoid)
      proteinaceous fld (colloid cyst, craniopharyngioma, Rathke's cleft cyst)
      melanin (melanoma)
      post pit
      hvy metals

      Chest

      Abdomen