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One advantage of MRI of the brain over computed tomography of the head is better tissue contrast, [19] and it has fewer artifacts than CT when viewing the brainstem. MRI is also superior for pituitary imaging. [20] It may however be less effective at identifying early cerebritis. [21]
A contrast agent usually shortens, but in some instances increases, the value of T1 of nearby water protons thereby altering the contrast in the image. Most clinically used MRI contrast agents work by shortening the T1 relaxation time of protons inside tissues via interactions with the nearby contrast agent.
MRI without contrast agents is the imaging mode of choice for pre-surgical, in-utero diagnosis and evaluation of fetal tumors, primarily teratomas, facilitating open fetal surgery, other fetal interventions, and planning for procedures (such as the EXIT procedure) to safely deliver and treat babies whose defects would otherwise be fatal. [52] [53]
A contrast agent (or contrast medium) is a substance used to increase the contrast of structures or fluids within the body in medical imaging. [1] Contrast agents absorb or alter external electromagnetism or ultrasound , which is different from radiopharmaceuticals , which emit radiation themselves.
Modern 3 Tesla clinical MRI scanner.. Magnetic resonance imaging (MRI) is a medical imaging technique mostly used in radiology and nuclear medicine in order to investigate the anatomy and physiology of the body, and to detect pathologies including tumors, inflammation, neurological conditions such as stroke, disorders of muscles and joints, and abnormalities in the heart and blood vessels ...
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to generate pictures of the anatomy and the physiological processes inside the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves to form images of the organs in the body.
Many pituitary tumors (25%) are found to have areas of hemorrhagic infarction on MRI scans, but apoplexy is not said to exist unless it is accompanied by symptoms. [ 1 ] [ 4 ] In some instances, lumbar puncture may be required if there is a suspicion that the symptoms might be caused by other problems ( meningitis or subarachnoid hemorrhage ).
When water is in an environment where it can freely tumble, relaxation tends to take longer. In certain clinical situations, this can generate contrast between an area of pathology and the surrounding healthy tissue. To sensitize MRI images to diffusion, the magnetic field strength (B1) is varied linearly by a pulsed field gradient.