[show abstract][hide abstract] ABSTRACT: Increasing film-focus distance (FFD) from the traditional 100 cm has been shown to be an effective method of reducing dose whilst maintaining image quality. In particular, previous work increasing the FFD from 100 to 130 cm for lumbar spine examinations demonstrated an effective dose reduction of 44%. Objective. The current study continues on from this work by investigating the dose-reducing efficacy of this FFD change for pelvis X-ray examinations. Materials and methods. Dose measurements at 100 and 130 cm using thermoluminescent dosemeters were undertaken using an anthropomorphic phantom and patients. Image quality was assessed using CEC anatomical criteria and psychophysical tests. Results. The results showed that increasing the FFD results in a reduction in effective dose of 33%, with no change in image quality. The data provided in this and previous studies demonstrate the need for rapid implementation of this simple cost-effective procedure across imaging departments, leading to an important reduction in collective dose. Conclusion. The CEC recommendation of using 115 cm FFD for a number of procedures, although useful compared with 100 cm, undervalues by a factor between 2 and 3 the potential of this dose-reducing tool.
[show abstract][hide abstract] ABSTRACT: 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.
European Radiology 09/2003; 13(8):1992-9. · 3.55 Impact Factor