Evaluation of the Usefulness of a Quality Control Phantom Developed for an In-House Mammography System and Assessment of Chest Wall Image Defects According to Focal Spot Position

Abstract

In Korea, the mammography quality control (QC) criteria currently exclude the assessment of “chest wall image loss according to focal spot position,” which is considered an essential item in advanced radiotherapy countries. This omission raises concerns regarding potential reductions in diagnostic accuracy. To address this issue, the present study designed and fabricated a QC phantom suitable for evaluating chest wall image loss. The phantom was modeled using Fusion 360 and manufactured with a stereolithography (SLA) 3D printer. Four holes (depth: 1 cm, diameter: 2 mm, repeated five times at each corner) were created on the lateral sides of the phantom, into which contrast medium was injected. After printing, the phantom was cleaned with isopropyl alcohol and post-cured at 60 °C. For imaging, the phantom was placed on the detector surface and fixed with a compression paddle. Exposures were performed with the focal spot fixed, using semi-automatic mode at 30, 32, and 34 kVp, as well as one exposure with automatic exposure control (AEC), for a total of four acquisitions. The images were analyzed using ImageJ software (version 1.53k, USA). Evaluation focused on whether all four contrast-filled holes near the chest wall were visualized and whether continuous visibility of at least 6 mm could be maintained throughout the image. The results showed that the mammography equipment at University S (Gyeonggi Province) achieved an average detectable length of 6 mm, whereas the mammography system at Hospital H (Namyangju) demonstrated an average length of less than 6 mm. Quality control review confirmed that the University S system met the Japanese mammography QC standards, while the Hospital H system did not. This study provides empirical evidence supporting the necessity of including the “verification of chest wall image loss” in domestic QC protocols, a criterion already established abroad. Furthermore, these findings offer foundational data for future policy improvements and are expected to contribute positively to enhancing mammographic image quality, promoting early detection of breast cancer, and ultimately improving patient survival rates.