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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.
MRI contrast agents may be administered by injection into the blood stream or orally, depending on the subject of interest. Oral administration is well suited to gastrointestinal tract scans, while intravascular administration proves more useful for most other scans. MRI contrast agents can be classified [2] by their: Chemical composition
Watershed stroke symptoms are due to the reduced blood flow to all parts of the body, specifically the brain, thus leading to brain damage. Initial symptoms, as promoted by the American Stroke Association, are FAST, representing F = Facial weakness (droop), A = Arm weakness (drift), S = Speech difficulty (slur), and T = Time to act (priority of intervention).
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.
In a comparison of genotoxic effects of MRI compared with those of CT scans, Knuuti et al. reported that even though the DNA damage detected after MRI was at a level comparable to that produced by scans using ionizing radiation (low-dose coronary CT angiography, nuclear imaging, and X-ray angiography), differences in the mechanism by which this ...
No effects of MRI on the fetus have been demonstrated. [49] As opposed to many other forms of medical imaging in pregnancy, MRI avoids the use of ionizing radiation, to which the fetus is particularly sensitive. As a precaution, however, many guidelines recommend pregnant women only undergo MRI when essential, especially during the first trimester.
Cerebral infarction, also known as an ischemic stroke, is the pathologic process that results in an area of necrotic tissue in the brain (cerebral infarct). [1] In mid to high income countries, a stroke is the main reason for disability among people and the 2nd cause of death. [2]
Hemorrhagic stroke may occur on the background of alterations to the blood vessels in the brain, such as cerebral arteriolosclerosis, cerebral amyloid angiopathy, cerebral arteriovenous malformation, brain trauma, brain tumors and an intracranial aneurysm, which can cause intraparenchymal or subarachnoid hemorrhage. [1]