Items tagged “physics”

104 results found
Case

X-ray tube: diagram

 Diagnosis not applicable
A.Prof Frank Gaillard
Published 17 Jan 2010
41% complete
Diagram
Article

Physical principles of ultrasound

Medical ultrasound is based on the use of high-frequency sound to aid in the diagnosis and treatment of patients. Ultrasound frequencies range from 2 to approximately 15 MHz, although even higher frequencies may be used in some situations. The ultrasound beam originates from mechanical oscillat...
Case

Mirror image artifact

 Diagnosis certain
Radswiki
Published 20 Oct 2010
72% complete
Ultrasound
Article

Inverse square law

The inverse square law describes the principle of dose reduction as the distance from the source increases. This assumes a point source. If radiation spreads over a spherical area, as the radius increases, the area over which the dose is distributed increases according to A=4πr^2 where A is the...
Article

Noise

Noise is present in all electronic systems, and originates from a number of sources including electronic interference. It appears as irregular granular pattern in all images and degrades image information. It may be inapparent or render images non-diagnostic, depending on the severity. Radiogra...
Case

Electron-positron annihilation

 Diagnosis not applicable
Dr Mohamed Elbanan
Published 17 Jan 2012
16% complete
Diagram
Article

Nuclear magnetic resonance

Nuclear magnetic resonance is a powerful technique which involves placing nuclei within an external magnetic field enabling thus them to undergo precession. The 'resonance' part of the names implies the fact that a second (usually perpendicular) radiofrequency pulse tuned to the precessional fre...
Article

Gibbs and truncation artifacts

Gibbs artifact, also known as truncation artifact or ringing artifact, is a type of MRI artifact. It refers to a series of lines in the MR image parallel to abrupt and intense changes in the object at this location, such as the CSF-spinal cord and the skull-brain interface. The MR image is reco...
Case

MRI physics (diagrams)

 Diagnosis not applicable
A.Prof Frank Gaillard
Published 16 Feb 2013
40% complete
Diagram
Article

Gradient coils

Gradient coils are used to produce deliberate variations in the main magnetic field (B0). There are three sets of gradient coils, one for each direction. The variation in the magnetic field permits localization of image slices as well as phase encoding and frequency encoding. The set of gradient...
Article

Radiofrequency coils

Radiofrequency coils (RF coils) are the "antennae" of the MRI system, broadcasting the RF signal to the patient and/or receiving the return signal. RF coils can be receive-only, in which case the body coil is used as a transmitter; or transmit and receive (transceiver). Surface coils are the si...
Article

Paramagnetism

Paramagnetic materials include oxygen and ions of various metals like Fe (iron), Mg (magnesium), and Gd (gadolinium). These ions have unpaired electrons, resulting in a positive magnetic susceptibility. The magnitude of this susceptibility is less than 0.1% of that of ferromagnetic materials. T...
Article

Superparamagnetism

Superparamagnetic materials consist of individual domains of elements that have ferromagnetic properties in bulk. Their magnetic susceptibility is between that of ferromagnetic and paramagnetic materials.  The figure illustrates the effect of a superparamagnetic material (grey circle) on the ma...
Case

Diagram - X-ray tube

 Diagnosis not applicable
Dr Matt Skalski
Published 08 Apr 2013
10% complete
Diagram
Case

Ring artefact

 Diagnosis certain
Dr Omar Giyab
Published 16 Apr 2013
77% complete
CT
Case

Magnetic susceptibility artifact

 Diagnosis certain
Dr Ayush Goel
Published 19 Apr 2013
73% complete
MRICT
Article

Diastolic pseudogating

Diastolic pseudogating appears as periodic bright and dark signal in arteries such as the aorta as one progresses through a series of images. Synchronization of the cardiac cycle and the pulse sequence results in high signal in the artery during diastole when blood is relatively stationary and l...
Article

Spiral pulse sequences

Spiral scanning in MRI is unlike spiral scanning in CT where the x-ray tube is continuously rotating and data is continuously being acquired. In MRI the word "spiral" refers to the pattern of sampling k-space. In conventional imaging sequences including spin echo and gradient echo and in fast im...
Case

Mirror image artifact

 Diagnosis certain
Dr Ayush Goel
Published 28 Dec 2013
94% complete
Ultrasound
Article

Mirror image artifact

Mirror image artifact in sonography is seen when there is a highly reflective surface (e.g. diaphragm) in the path of the primary beam. The primary beam reflects from such a surface (e.g. diaphragm) but instead of directly being received by the transducer, it encounters another structure (e.g. ...

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