Development and testing of an anthropomorphic aluminum phantom for digital chest radiography: a technical report

BACKGROUND: The regulated quality control procedure for radiography involves the analysis of test objects without simulating anatomical features. However, subsequent assessment of radiologists’ performance or artificial intelligence-based decision support systems requires anonymized data samples from real patients annotated by multiple specialists. Collecting such datasets is a labor-intensive and time-consuming process, especially when we need a sample containing actual pathologies. Therefore, it is advisable to use anthropomorphic test objects (phantoms) which simulate pathological findings, so that the X-ray image will be as close as possible to the analyzed images of patients. AIM: To develop and test an anthropomorphic aluminum phantom for digital radiography. METHODS: A digital radiograph of the chest of a healthy person was used as a reference standard during phantom design. A sample of the designed phantom was made using layer-by-layer milling of an aluminum blank. Validation was carried out by comparing phantom images and the reference image. In addition, the effect of the phantom sample on the spatial resolution and contrast sensitivity was assessed for different acquisition modes of the X-ray unit. The applicability of the phantom for simulating focal lung lesions was studied, with the results evaluated by experts. RESULTS: The phantom was found to reproduce the reference image with a high fidelity and allows simulation of pathological changes in chest X-rays by placing flexible pads in the required positions. The ratios of attenuation coefficients for different anatomical areas were identified during X-ray imaging of the phantom and three patients. CONCLUSION: This work presents a method for developing a high-fidelity anthropomorphic phantom made of D16T aluminum alloy, designed for calibrating X-ray systems and testing radiologists. The phantom imitates the anatomical structures of the chest organs and pathological changes, such as focal lesions. The main advantages of this solution include reduced production costs, compact design, and high accuracy of reproduction of radiographic characteristics.