Grids | 合法醫療器材資訊網

Gridsareplacedbetweenthepatientandthex-rayfilmtoreducethescatteredradiationreachingthedetector(producedmainlybytheComptoneffect)and ...

Grids are placed between the patient and the x-ray film to reduce the scattered radiation reaching the detector (produced mainly by the Compton effect[1]) and thus improve image contrast[2].

They are made of parallel strips of high attenuating material such as lead with an interspace filled with low attenuating material such as carbon fiber or organic spacer 7. The strips can be oriented either linear or crossed in their longitudinal axis. As scattered radiation is increased in "thicker" patients and at larger field sizes, grids are useful in such scenarios to improve image contrast.

The working ability of a grid is described by the grid ratio, which is the ratio of the height of the lead strips (h) to the distance between two strips, i.e. the interspace (D) 7. A grid ratio of 8:1 is generally used for 70-90 kVp technique and 12:1 is used for >90 kV...