MR imaging of cerebral hemorrhage
November 11th, 2009 by Administrator

The author: Professor Yasser Metwally


November 11, 2009 — MR imaging of cerebral hemorrhage

Hyperacute Hemorrhage (0 TO 12 Hours)

Hyperacute hemorrhage refers to a collection of blood in which oxyhemoglobin predominates. This type of hemorrhage is rarely encountered in the clinical setting because several hours commonly elapse between the onset of hemorrhage and a patient being referred for MR imaging. A hyperacute hematoma may have a nonspecific appearance on MR imaging because oxyhemoglobin is not paramagnetic. Hyperacute hemorrhages can behave similar to other lesions with increased water content and are typically isointense or low signal on Tl-weighted images and high signal on T2- weighted images.With clot retraction in the hyperacute phase, the increased protein content of the hemorrhage results in the lesion being isointense to hyperintense on Tl- weighted images, which can facilitate differentiation from other mass lesions.A hypointense rim along the periphery of a hyperacute hemorrhage was noted ,and this may provide an additional clue to the diagnosis. Hyperacute hemorrhage, however, is more readily identified on CT, which remains the initial examination of choice for its evaluation.

Acute Hemorrhage (12 Hours to 3 Days)

In the acute setting, there is clot retraction and resorption of serum. As the hematoma becomes isolated from the normal cerebral circulation, oxyhemoglobin rapidly deoxygenates to yield deoxyhemoglobin. The increased protein content of the retracted clot, which is responsible for the high attenuation noted on noncontrast CT, causes the hematoma to be slightly hyperintense relative to low-intensity cerebrospinal fluid (CSF) and slightly hypointense to brain parenchyma on Tl-weighted images. In contrast to CT in the acute setting, which reliably demonstrates high attenuation characteristic of acute hemorrhage, MR imaging findings on Tl-weighted images are relatively nonspecific.

T2-weighted images demonstrate a marked decrease in signal intensity because of magnetic susceptibility effects. The signal loss is due to local field inhomogeneity related to paramagnetic deoxyhemoglobin within intact red blood cells. Gradient echo images exaggerate this effect and are often useful for the diagnosis of acute hemorrhage

Subacute Hemorrhage: Early (3 Days to I Week)

In the early subacute stage, oxidation of deoxyhemoglobin to methemoglobin occurs within intact red blood cells. Methemoglobin is paramagnetic, which results in marked increased signal intensity on Tl-weighted images. Typically the increased signal begins at the periphery of the clot and progresses inward. The differential diagnosis of lesions that demonstrate increased signal intensity on noncontrast TI-weighted images is relatively limited. Fat; substances with elevated protein content (mucus or fluid within certain intracranial tumors, i.e., craniopharyngioma); and paramagnetic moieties, such as melanin, free radicals (within the wall of parenchymal abscesses), and ions including calcium, manganese, and copper, can exhibit high signal intensity on Tl-weighted images. Correlation with the clinical history, morphology, and location of the lesion as well as appearance on other imaging sequences (i.e., T2, gradient echo, and fat suppression) typically allows differentiation from subacute hemorrhage.

On T2-weighted images, paramagnetic methemoglobin in intact red blood cells results in low signal intensity similar to that of deoxyhemoglobin. The combination of bright signal intensity on Tl and markedly decreased signal intensity on T2 is relatively specific for paramagnetic substances and, with the appropriate morphology, is highly suggestive of intracranial hemorrhage

Subacute Hemorrhage: Late (1 Week to Months)

The late subacute stage is characterized by lysis of the blood cells. Concurrently, there is dilution of extracellular methemoglobin and breakdown of the proteinaceous clot. High signal intensity persists on TI-weighted images because of methemoglobin; however, lysis of the red blood cells and the decrease in protein content result in increased signal intensity on T2-weighted images. Bright signal intensity on both Tl-weighted and T2- weighted images is highly specific for hemorrhage. Furthermore, at the periphery of the hemorrhage, early accumulation of hemosiderin and ferritin within macrophages causes a low signal intensity ring, most prominent on T2-weighted images.

Chronic stage (Months to Years)

The hallmark of chronic hemorrhage is low signal intensity on T2-weighted images because of ferritin and hemosiderin within macrophages, which are the final breakdown products of hemoglobin. The resulting low intensity first appears during the late subacute stage of hematoma evolution at the margin of the lesion. With time, the rim thickens. A collapsed cavity with peripheral areas of low signal intensity on T2-weighted images is the residuum of an uncomplicated intraparenchymal hemorrhage. This appearance can persist indefinitely.


  1. Metwally, MYM: Textbook of neuroimaging, A CD-ROM publication, (Metwally, MYM editor) WEB-CD agency for electronic publication, version 10.4a October 2009 [Click to have a look at the home page]

  2. Intracerebral haemorrhage [Full text]

  3. Neuroimaging of cerebral hemorrhage [Full text]


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