Evaluating the use of higher kVp and copper filtration as a dose optimisation tool in digital planar radiography

Abstract

Introduction: To identify the potential of beam hardening techniques, specifically the use of higher kilo voltage (kV) and copper (Cu) filtration, to optimise digital planar radiographic projections. The study assessed the suitability of such techniques in radiation dose reductions while maintaining diagnostic image quality for four common radiographic projections: antero-posterior (AP) abdomen, AP-knee, AP-lumbar spine, and lateral lumbar spine.

Methods: Anthropomorphic phantom radiographs were obtained at varying kVp (standard kVp, +10 kVp, and +20 kVp) and varying Cu filtration thickness (0 mm, 0.1 mm, and 0.2 mm Cu). The Dose Area Product (DAP), mAs and time (s) were recorded as an indication of the emitted radiation dose. Image quality was assessed objectively via Contrast-Noise-Ratio (CNR) calculations and subjectively via Visual Grading Analysis (VGA) performed by radiographers and radiologists.

Results: Optimised exposure protocols were established for the AP-abdomen (100 kVp with 0.2 mm Cu), AP-knee (85 kVp, and 0.1 mm Cu), AP-lumbar spine (110 kVp and 0.2 mm Cu), and lateral lumbar spine (110 kVp and 0.2 mm Cu). This strategy resulted in respective DAP reductions of 71.98%, 62.50%, 64.51% and 71.85%. While CNR values decreased as beam hardening techniques were applied, VGA demonstrated either a lack of statistical variation or improved image quality between the standard and the optimised exposure protocols.

Conclusions: DAP reductions without compromising image quality can be achieved through beam hardening for the AP-abdomen, AP-knee, AP-lumbar spine, and lateral lumbar spine projections. Implications for practice: Beam hardening techniques should be considered as an optimisation strategy in medical imaging departments. Research into the applicability of this strategy for other radiographic projections is recommended.