Do CEC guidelines under-utilise the full potential of increasing kVp as a dose-reducing tool?
Brennan, Patrick C.
Increasing beam energies are well established as a radiation dose-reducing tool in diagnostic radiology. This has led to useful recommendations by the Commission of European Communities (CEC) for appropriate kVp values to be employed for a variety of examinations. The current work tests the hypothesis that kVp levels above those recommended by the CEC will result in reduced patient dose while still producing images of acceptable quality. This study explored the effect of a range of kVp levels within and above CEC recommendations for lumbar spine radiology. A phantom investigation facilitated selection of appropriate kVp levels for a patient study (n=59): 81 kVp (CEC) and 96 kVp (non-CEC) for the AP projection and 90 kVp (CEC) and 102 kVp (non-CEC) for the lateral projection. Entrance surface and effective dose were calculated and image quality quantified using CEC image criteria and images of a detail contrast test tool. Data analysis demonstrated significant reduction in effective radiation dose for AP (29.9%) and lateral (24.6%) when a kVp value above the CEC range was employed compared with a kVp recommended by the CEC. Although significant reductions in total image quality of 18.3 % and 10.1% for the antero-posterior and lateral projections, respectively, were noted, all patient images produced with all kVp values were considered acceptable by each member of the evaluative panel with all image criteria receiving a score of 2 (out of 3) or better. The psychophysical tests revealed minor non-significant reductions in visualisation scores. The current study demonstrated that kVp values outside the CEC recommended range offer reductions in dose while producing acceptable images. Practitioners should be guided, rather than constrained, by the CEC recommendations on good radiographic technique. The need for further work exploring the effect of higher energies on visualisation of subtle pathological lesions has been identified.