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In general, persistent increased signal intensity (corresponding to decreased T1 and thus increased Gd interaction) in a DCE-MRI image voxel indicates permeable blood vessels characteristic of tumor tissue, where Gd has leaked into the extravascular extracellular space. In tissues with healthy cells or a high cell density, gadolinium re-enters ...
MRI scans showing hyperintensities. A hyperintensity or T2 hyperintensity is an area of high intensity on types of magnetic resonance imaging (MRI) scans of the brain of a human or of another mammal that reflect lesions produced largely by demyelination and axonal loss.
In the case of CSF suppression, one aims for T 1-weighted images, which prioritize the signal of fat over that of water. Therefore, if the long TI (inversion time) is adjusted to a zero crossing point for water (none of its signal is visible), the signal of the CSF is theoretically being "erased," from the derived image.
Fig. 10. Surface coil artifact: high signal at anterior thoracic wall adjacent to surface coil. [1] Absence of signal from tissues of a particular T1 value is a consequence of magnitude sensitive reconstruction in inversion recovery imaging. When the chosen T1 equals 69% of the T1 value of a particular tissue, a bounce point artifact occurs. [1]
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.
Damage is greater in the sulci when compared to gyri of the brain. [2] When seen on CT scan, it shows hyperdensity in the surface of the cortex. Cortical enhancement is seen after two weeks, with maximum intensity at one to two months, and resolved after six months. [2] On MRI scans, early changes show low T1 intensity due to ischemic changes.
Fluid-attenuated inversion recovery (FLAIR) [2] is an inversion-recovery pulse sequence used to nullify the signal from fluids. For example, it can be used in brain imaging to suppress cerebrospinal fluid so as to bring out periventricular hyperintense lesions, such as multiple sclerosis plaques.
A conventional gradient echo T2*-weighted image (left, TE=20 ms) shows some low-signal foci associated with CAA. On the other hand, an SWI image (center, with a resolution of 0.5 mm x 0.5 mm x 2.0 mm, projected over 8mm) shows many more associated low-signal foci. Phase images were used to enhance the effect of the local hemosiderin build-up.