Effective dose efficiency: an application-specific metric of quality and dose for digital radiography

The detective quantum efficiency (DQE) and the effective DQE (eDQE) are relevant metrics of image quality for digital radiography detectors and systems, respectively. The current study further extends the eDQE methodology to technique optimization using a new metric of the effective dose efficiency (eDE), reflecting both the image quality as well as the effective dose (ED) attributes of the imaging system. Using phantoms representing pediatric, adult and large adult body habitus, image quality measurements were made at 80, 100, 120 and 140 kVp using the standard eDQE protocol and exposures. ED was computed using Monte Carlo methods. The eDE was then computed as a ratio of image quality to ED for each of the phantom/spectral conditions. The eDQE and eDE results showed the same trends across tube potential with 80 kVp yielding the highest values and 120 kVp yielding the lowest. The eDE results for the pediatric phantom were markedly lower than the results for the adult phantom at spatial frequencies lower than 1.2-1.7 mm-1, primarily due to a correspondingly higher value of ED per entrance exposure. The relative performance for the adult and large adult phantoms was generally comparable but affected by kVps. The eDE results for the large adult configuration were lower than the eDE results for the adult phantom, across all spatial frequencies (120 and 140 kVp) and at spatial frequencies greater than 1.0 mm-1 (80 and 100 kVp). Demonstrated for chest radiography, the eDE shows promise as an application-specific metric of imaging performance, reflective of body habitus and radiographic technique, with utility for radiography protocol assessment and optimization.