The use of anthropomorphic phantoms for patient dose and image contrast surveys in digital radiography

This work aims to investigate the relationship of dose and local contrast values between the standard anthropomorphic phantoms and patients with different body mass index (BMI) in chest and abdominal radiography. Entrance Surface Air Kerma (ESAK) values for chest and abdomen examinations were determined for patients categorized into three BMI groups and they were also measured for chest and abdomen anthropomorphic phantoms using three digital radiographic systems. Tissue regions were selected from different anatomical structures for the measurement of image contrast from patient and phantom images. Since the phantoms used are constructed to represent standard body size, ESAK values for these phantoms did not correlate "well" with the results from patients having different body mass index (BMI) for some examinations and systems. The means ESAK for thorax and abdomen examinations was 0.16 and 1.46 mGy, respectively. The calculated mean effective dose was 0.03 mSv for thorax and 0.20 mSv for abdomen examinations. For three digital radiographic systems, while a moderate or strong Spearman rank correlation coefficient (rs = 0.601-0.794) was established between ESAK and BMI for thorax examinations, strong or very strong correlation (rs = 0.710-0.904) was determined for abdomen examinations. The contrast between different tissue regions measured from the phantoms generally matched the patient results. It is shown that the use of phantom data, which are recorded using similar exposure and processing parameters to patient examinations, can provide useful information for better evaluation of patient results.