Items tagged “mri”
786 results found
Article
Effect of gradient strength and bandwidth on slice thickness
Slice thickness is dependent on gradient strength and bandwidth, to attain a slice thickness, a range of frequencies must be transmitted to produce resonance across the whole slice. This range of frequencies is the transmitter RF (radiofrequency) bandwidth (tBW). Slice thickness is determined by...
Article
Magnetic field homogeneity
One of the key concepts in assessing the quality of a magnet is that of magnetic field homogeneity, as it will relate to image quality and the presence of artifacts.Field homogeneity refers to the uniformity of the main magnetic field when no patient is present, measured in parts per million (pp...
Article
Magnetic shimming
Magnetic shimming refers to the process of reducing magnetic field inhomogeneities. It is an important aspect of optimizing image quality. Field inhomogeneities can be the result by both intrinsic magnet properties and the surrounding environment of the MR magnet – such as the presence of nearby...
Article
Slew rate
Slew rate refers to the speed at which a gradient can be turned on and off, and is defined as the maximum gradient strength of the gradient divided by the rise time.
MR imaging is a product of magnetic field gradients which are created by magnetic gradient coils. The quality and performance of...
Article
Paul Lauterbur
Paul C Lauterbur (1929-2007) is remembered as one of the co-developers of MRI, for which he was co-awarded the Nobel Prize for Medicine or Physiology in 2003, with Peter Mansfield.
Early life
Paul Christian Lauterbur was born on 6 May 1929 in Sidney, Ohio.
In 1951 he graduated with a bachelor...
Article
Mellado-Bencardino classification of Morel-Lavallée lesions
The Mellado-Bencardino classification of Morel-Lavallée lesions is based on shape, signal and enhancement characteristics, and the presence or absence of a capsule 1:
type I: laminar-shaped and seroma-like with increased T2 signal
type II: oval-shape that resembles a subacute hematoma with in...
Article
Radiofrequency transmitter
The radiofrequency (RF) transmitter is the generator of the radiofrequency current which is delivered to the transmitting coil. This creates a signal which is used to excite protons in the imaging field. Radiofrequency coils can be both transmitters and receivers of the radiofrequency signal or ...
Article
Radiofrequency receiver
Radiofrequency coils are the radiofrequency receivers (as well as sometimes the transmitters) of the electromagnetic signal used in MRI. Radiofrequency coils can be either receive-only, or both receivers and transmitters of the radiofrequency signal. The receiver coils detect the electromagnetic...
Article
Volume coils
Volume coils are the transmit and receive radiofrequency coils which are used to both transmit and receive the radiofrequency signal in MRI. Most MRI scanners have what is called a body coil – which is a volume coil built into the bore of the magnet which transmits the radiofrequency for most ex...
Article
Surface coil
Surface coils are a type of receive-only radiofrequency coil used in MRI to receive the radiofrequency signal (transmitted by the body coil). Surface coils are small and are shaped so that they can be placed near the part of anatomy being imaged. By their nature, surface coils have good signal-t...
Article
Phased array coil
Phased array coils are an example of a receive-only radiofrequency coil system which receives the radiofrequency signal in MRI. It involves the collection of multiple surface coils into a larger array whose individual signals are combined to create one image. As signal coils detect signal based ...
Article
Magnetic shielding
Magnetic shielding refers to the attempt to isolate or block the magnetic field of the MRI magnet. This can be done to prevent unwanted interference from the MRI magnet on nearby electronic devices. This is different from radiofrequency shielding, which is the attempt to prevent the unwanted i...
Article
Fringe field (MRI)
The fringe field is the peripheral magnetic field outside of the magnet core. It is important because it can cause interference with nearby electronic devices, such as pacemakers. Although the strength of the magnetic fields decreases with distance from the core of the magnet, the effect of the ...
Article
Voxel size
Voxel size is an important component of image quality. Voxel is the 3-D analog of a pixel. Voxel size is related to both the pixel size and slice thickness. Pixel size is dependent on both the field of view and the image matrix. The pixel size is equal to the field of view divided by the matrix...
Case
Shoulder osteoarthritis
Published
09 Dec 2018
89% complete
MRI
Case
Uterine adenomyosis
Published
13 Dec 2018
74% complete
MRI
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Ganglion cyst - flexor tendon sheath / A1 pulley
Published
21 Dec 2018
80% complete
MRI
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Cerebral cavernoma
Published
16 Dec 2018
77% complete
MRI
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Idiopathic intracranial hypertension
Published
17 Dec 2018
77% complete
MRI
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Sclerosing angiomatoid nodular transformation of the spleen
Published
24 Dec 2018
69% complete
CT
MRI
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