Category: S

In hyperthermia treatment, the rate of absorption of heat energy per unit mass of tissue in units of W/kg.  

The number used to describe the relative contributions to a detected signal of the true signal and random superimposed signals (“noise”). One way of improving the SNR is to average several measurements of the signal on the expectation that the random contributions will tend to cancel out. The SNR can also be improved by sampling…

A unit of dose equivalent. The sievert has idential units to the gray and is arrived at by multiplying the absorbed dose by the quality EA( tor, a number that has been determined to accurately compare the health consequences of that type of radiation to x rays. The rem bears the same relationship to the…

Techniques in which the image is built from successive point positions in the object.  

Technique in which the image of an object is built up from successive planes in the object. In various schemes, the planes are selected by oscillating gradient magnetic fields or selective excitation.  

Techniques in which the image is built up from successive lines through the object.  

In NMR imaging the region of the object from which an NMR signal will preferentially be acquired because of strong magnetic field inhomogeneity elsewhere. The effect can be enhanced by use of a shaped rf field that is strongest in the sensitive region.  

A device that relies on the emission of light or ultraviolet radiation from a crystal subjected to ionizing radiation. The light is detected by a photomultiplier tube and converted to an electrical signal which can be processed further. An array of scintillation detectors is used in a gamma camera.  

Therapy administered to sites at which previous therapies have failed and the disease has recurred. Treatment that follows the relapse of an illness that had already been treated in standard fashion. When other treatment options have proven ineffective in managing a disease, medical interventions implemented at a later stage in the disease’s progression are referred…

The ability of an imaging process to distinguish adjacent structures in the object, and an important measure of image quality. In radiology, the ability to distinguish two adjacent points of similar density as being separate.