Correlations between exposure conditions and dosimetric parameters for digital radiography (DR)

Objective: To study correlations between exposure conditions and dosimetric parameters for digital radiography (DR). Methods: Quality assurance (QA) was performed with BARRACUDA system to make sure DR x-ray machine was in good condition. On condition that testing phantom was used, dosimetric parameters, such as dose area product (DAP), output of x-ray machine, entrance surface dose (ESD) were recorded while changing exposure conditions including kV,mAs and filter. Correlations between exposure conditions and dosimetric parameters were analyzed. Results: DAP reduced from 173.80 mGy · cm2 to 33.39 mGy · cm2, output of x-ray machine increased from 0.010Gy/ (A · s) to 0.032 Gy/(A · s), ESD reduced from 0.74 mGy to 0.17 mGy, when kV raised steadily from 60 to 120. At 70 kV, 90 kV and 110 kV, DAP and ESD increased steadily in same trend as mAs. The decrease extent of DAP and ESD was distinctly less when 2.5 mmAl+1 mm Cu or 3.3 mm Al+1 mm Cu were used as total filter, comparing to 3.3 mmAl or 4.1 mmAl. For certain filter, there were significantly negative correlation (P<0.05) among DAP, ESD and kV, and there were significantly positive correlation (P<0.05) among DAP, ESD and mAs. Output of x-ray machine was correlated positively negatively with kV (P<0.05), negatively with mAs (P<0.05). The correlations were not affected by changing of kV or mAs. Conclusion: For DR, the dose of examinees can be effectively reduced by properly raising kV or lowering mAs. (authors)