Grids

marker market

physical vs online non scatter grid

Physical grid: attenuates scatter radiation. Reduces scatter reduces contrast resolution, must increase exposure, must increase kVp, increased patient dose. Has either vertical or diagonal lines: angles in opposite way will burn out image. Can create grid lines if not oscillating grid ( back-and-forth or circular motion of the grid, which is key to minimising the grid lines on the X-ray images.). oscillating grids usually on wall Bucky. Why no grid lines on portable grids? Portable grids use stationary grids. Portable grids higher frequency. grid ration and frequency: distance vs width of lead strips. Higher freq grids have thinner lead strips, spaced closer together, reduce likelihood of lines being visible on final image. But proper alignment must be followed. 

Digital image processing: usually filters. Mostly smooth and sharpening. Smooth- average. Sharpness- edge enhancement. Smooth replaces outliers/extrapolates?  And replaces them with average. thus no “noise” in image.  Sharpness filter use edge enhancement to differentiate between organ/tissue and background/edge. If contrast/grey levels too similar  e.g..“55 57 56” to “67 68 68/66 65 66”, software will multiply/add/subract higher number by X factor to create “edge” and grey level difference between tissue and non-tissue. Wow amazing. Problem?

1. Rads will not pay attention to exposure levels, overexpose/underexpose and rely on filters + pos processing. 

2. Physical grids reduce scatter BEFORE it reaches pt. In digital imaging processing, scatter already reached pt, maybe created artefact. this can’t be fixed in post processing. physical grid fixed problem before it happens. Can’t have this issue if not there in the first place.