Radiographic grids are used extensively in plain film radiography. The fundamental properties of grids, such as focusing distance, focus- grid distance, grid ratio, grid frequency, primary and secondary transmission, grid factor, selectivity and contrast improvement factor will be revisited. The main aim is to calculate and examine the positioning limitations of grids in relation to the X-ray tube. These positioning limitations include range limits of the focal film distance (FFD) as the X-ray tube is brought closer to the grid when using parallel grids and the range of vertical and lateral movement of the X- ray tube focus in relation to a focused grid before grid cut-off occurs. Although latitude in the range of these movements can occur, it is important to understand that other areas such as increased patient dose will occur when the X-ray tube is not centrally located over the grid at the correct focusing distance.
|Number of pages||7|
|Publication status||Published - 1998|