Items tagged “physics”

54 results found
Case

X-ray tube: diagram

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

Inverse square law

The inverse square law describes the principle of dose reduction as 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 are...
Article

Nuclear magnetic resonance

Nuclear magentic 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 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 reconstructed from k-space which is a finite sampling of the...
Case

Electron-positron annihilation

Diagnosis not applicable
Dr. Mohamed Elbanan
Published 17 Jan 2012
16% 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 "antenna" 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...
Case

Diagram - X-ray tube

Diagnosis not applicable
Dr Matt Skalski
Published 08 Apr 2013
13% complete
Diagram
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 one one-thousandths of that of ferromagneti...
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...
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 ...
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

Mirror image artifact

Diagnosis certain
Dr Ayush Goel
Published 28 Dec 2013
85% complete
Ultrasound
Article

Mirror image artifact

Mirror image artifact in ultrasonography 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 (...
Case

CT stair step artifact

3D reconstruction...
Diagnosis certain
Dr David Cuete
Published 13 Feb 2014
91% complete
CT
Article

Kilovoltage peak

Kilovoltage peak (kVp) is the peak voltage applied to the X-ray tube. It determines the highest energy of X-ray photon. It is responsible for acceleration of electrons from cathode to anode. It also determines tube current in space charge region.  Increase in kVp shifts the X-ray spectrum to ri...
Case

Static electricity

Diagnosis certain
Dr Ayush Goel
Published 14 Jul 2014
79% complete
X-ray
Case

Thermoluminescent dosimeter badge (CaSO4:Dy Teflon)

Nickel coated alu...
Diagnosis not applicable
Dr Ayush Goel
Published 23 Jul 2014
35% complete
Photo
Article

Compton effect

Compton effect or Compton scatter is one of three principle forms of photon interaction. It is the main cause of scattered radiation in a material. It occurs due to the interaction of the X-ray or gamma photon with the outermost (and hence loosely bound) valence electron at the atomic level. The...

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