X-ray dose reduction using additional copper filtration for abdominal digital radiography: Evaluation using signal difference-to-noise ratio.
OBJECTIVE
X-ray dose reduction using additional copper filters (Cu-filters) for abdominal general radiography was indicated in a report using a simulation study. We validated the dose reduction effects using a clinical digital radiography system equipped with an indirect-type CsI detector and an automatic Cu-filter insertion function.


METHODS
The image qualities were evaluated using signal difference-to-noise ratio (SDNR) for different radiation qualities with and without Cu-filters for a 20-cm acrylic phantom. Acrylic and bone equivalent material plates were used for contrast measurements. The dose reduction using Cu-filters was estimated from the ratios of the SDNR2values.


RESULTS
For the same entrance surface dose (ESD), Cu-filters with 0.1- and 0.2-mm thicknesses increased the image quality as evaluated by SDNR2and the estimated dose reduction without degrading the image quality. For the acrylic contrast, the dose reductions with the 0.1- and 0.2-mm-thick Cu-filters were approximately 30% and 44% at 70kV and 29% and 35% at 80kV, respectively. For the bone contrast, the reduction rates were slightly reduced.


CONCLUSIONS
We validated the dose reduction capability of additional Cu-filters without degrading the image quality for abdominal radiography. The estimated entrance surface dose reductions of the Cu-filters were approximately 30-40% and 20-30% for the acrylic and bone contrasts, respectively, and effective dose reductions for acrylic were nearly half of those for ESD. At these reduced dose conditions, the current time product values needed to be increased by factors of 1.4 and 1.8 for the 0.1- and 0.2-mm-thick Cu-filters, respectively.
Faculty of Health Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University,Japan. Electronic address: kawa3@med.kanazawa-u.ac.jp.
Hiroki
H
Kawashima
Faculty of Health Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University,Japan.
Katsuhiro
K
Ichikawa
Division of Health Sciences, Graduate School of Medical Sciences, Kanazawa University,Japan.
Daisuke
D
Nagasou
Division of Health Sciences, Graduate School of Medical Sciences, Kanazawa University,Japan.
Masayuki
M
Hattori
D003300:Copper; D005374:Filtration; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement / Q000379:methods*; D011860:Radiography, Abdominal / Q000379:methods*; D059629:Signal-To-Noise Ratio; D014965:X-Rays
D003300:Copper
Abdominal radiography; Cu-filter; Dose reduction; Signal difference-to-noise ratio