Although MRI is often thought of as not being sensitive to acute haemorrhage, this is not, in fact, true particularly with more modern sequences 5,7. The factors that affect the appearance of haemorrhage on MRI vary according to the sequence. The oxygenation state of haemoglobin and the location of either contained within red blood cells or diffused in the extracellular space have a tremendous effect on the imaging effects of blood. The three haemoglobin states to be considered are oxyhaemoglobin, deoxyhaemoglobin and methaemoglobin. Oxyhaemoglobin and deoxyhaemoglobin produce little effect on T1 signal.
MRI Detects Blood Flow Changes in Young People with Kidney Disease
Diffusion Weighted Imaging in Hemorrhage | Radiology Key
Aging blood on MRI is dependent on the varying MRI signal characteristics of hemorrhagic collections with time and can be very useful in correlating the imaging findings with the clinical picture. However, as it can be complicated to recall the MRI features of aging blood through the five stages of hematoma evolution several mnemonics have been devised:. The first two mnemonics use the first letters of the words and word pairs to denote the signal characteristics of blood at each stage as isointense I , bright B , or dark D. The first bold letter in each pair denotes the typical T1 signal finding, while the second denotes the T2 signal change. For those that find it difficult to memorize the mnemonic above an alternative is found below which uses full word pairs. This mnemonic uses bold capital letters of the sentence in pairs of two to denote the signal characteristics of blood at each stage as isointense I , bright B , or dark D.
Magnetic Resonance Imaging (MRI)
T he use of radiologic studies in the ophthalmic setting is becoming increasingly more common, especially for neuro-ophthalmic disorders. Many eye care providers now routinely order various types of neuroimaging studies that provide valuable and detailed information on neural visual pathways not easily obtained through clinical examination alone. The most commonly ordered diagnostic test is magnetic resonance imaging MRI because it allows imaging of the orbital apex and optic nerve despite the dense bone surrounding these areas. The most common indications for neuroimaging are vision or visual field loss, pupil abnormalities, ptosis, proptosis, diplopia or ophthalmoplegia, nystagmus and certain optic disc abnormalities. MRI studies are based on the signal detection of the interaction between hydrogen molecules within a magnetic field.
The pattern of evolving hematomas on conventional magnetic resonance imaging MRI is well documented but remains somewhat complex, and its interpretation is further complicated by diffusion weighted imaging DWI. T2 shine-through, T2 blackout effects, and susceptibility artifacts from blood products contribute to the appearance of hemorrhage on DWI and influence the apparent diffusion coefficient ADC measurements. According to recent studies, DWI is accurate in detection, characterization, and staging of intraparenchymal hematomas; however, it should not be interpreted alone but in conjunction with other sequences.