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The first study of the human brain at 3.0 T was published in 1994, [13] and in 1998 at 8 T. [14] Studies of the human brain have been performed at 9.4 T (2006) [15] and up to 10.5 T (2019). [16] Paul Lauterbur and Sir Peter Mansfield were awarded the 2003 Nobel Prize in Physiology or Medicine for their discoveries concerning MRI.
The key to Phase-contrast MRI (PC-MRI) is the use of a bipolar gradient. [4] A bipolar gradient has equal positive and negative magnitudes that are applied for the same time duration. The bipolar gradient in PC-MRI is put in a sequence after RF excitation but before data collection during the echo time of the generic MRI modality.
In cerebral infarction, the penumbra has decreased perfusion. [1] Another MRI sequence, diffusion weighted MRI, estimates the amount of tissue that is already necrotic, and the combination of those sequences can therefore be used to estimate the amount of brain tissue that is salvageable by thrombolysis and/or thrombectomy.
Diffusion imaging is an MRI method that produces in vivo magnetic resonance images of biological tissues sensitized with the local characteristics of molecular diffusion, generally water (but other moieties can also be investigated using MR spectroscopic approaches). [15]
Like in vivo MRS, fMRS can probe different nuclei, such as hydrogen (1 H) and carbon (13 C). The 1 H nucleus is the most sensitive and is most commonly used to measure metabolite concentrations and concentration dynamics, whereas 13 C is best suited for characterizing fluxes and pathways of brain metabolism.
Liver MRE examinations are performed in MRI systems that have been equipped for the technique. Patients should fast for 3 to 4 hours prior to their MRE exam to allow for the most accurate measurement of liver stiffness. [20] [21] [22] Patients lie supine in the MRI scanner for the examination. A special device is placed on the right side of the ...
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CT scans may be used to diagnose headaches when neuroimaging is indicated and MRI is not available, or in emergency settings when hemorrhage, stroke, or traumatic brain injury is suspected. [9] MRI (magnetic resonance imaging) provides more sensitivity in the evaluation of the cavernous sinus and the orbital apex. [8]