Table 3a

Effect of grid removal on phantom fluoroscopy doses 30 s, source–image distance 100 cm

ProtocolFOV cmGrid inGrid outGrid removal effect
DAP µGy.m2 ESD mGyDAP µGy.m2 ESD mGyDAP % reductionESD % Reduction
Low dose adult3219.981.310.10.64954.8
Low dose adult2211.751.349.031.0323.123.1
Low dose adult166.761.545.751.3214.914.3
Low dose adult114.091.93.471.6115.215.3
  • Readings using low-dose adult protocols and a pediatric imaging protocol under conditions similar to those of table 2. Pulse rates were fixed at 3 per second. The impact of grid removal became less substantial with higher levels of magnification.

  • Notice that increasing magnification for all settings reduces the DAP to a disproportionately greater degree than the corresponding increase in ESD resulting from the same magnification. This effect is a result of the improved dose profile of flat-panel technology and runs counter to the long-maintained canard that ’magnification increases dose'. Skin dose does increase on flat-panel machines with smaller FOV settings but to a lesser degree than was the case with older image-intensifier equipment. More germanely, it may not yet have reached common understanding among all operators that an adjustment in thinking about the impact of magnification on ’dose' is therefore necessary. The stochastic risks of a procedure are linked to the DAP, not to skin dose, and therefore operating on routine portions of a procedure at low magnification will result as a general rule of thumb in lower skin doses but higher DAP readings.

  • DAP, dose–area product; ESD, estimated skin doses; FOV, field of view.