Purpose: Digital breast tomosynthesis (DBT) offers a choice of image acquisition conditions. The object of observation is the entire detector in the full depth (Z-axis) direction. In this study, we investigated the effect of each acquisition condition on Z-resolution with a micro-metallic sphere (bead) as an imaged object in DBT images. Method: DBT images were acquired in two imaging modes with different angular ranges, varying with the height of the bead, the bead placement position, and the bead diameter. The depth profile of the bead image was obtained, and the Z-resolution was defined by its full width at half maximum. The Z-resolution was compared with each acquisition condition. Result: The Z-resolution values decreased with increasing height from the breast support and decreasing bead diameter. The Z-resolution values were larger at the edges than at the detector center. Conclusion: This study shows that the bead diameter and the geometry of the bead and detector affect the Z-resolution measurement.

Purpose: Recently, monitors with maximum luminance exceeding 2000 cd/m² (high-luminance monitor) have been used for diagnostic mammography. In this study, we examined the visibility of high-luminance monitors by converting luminance meter measurements into the just noticeable difference (JND) Index. The ambient light was also examined at the same time. Method: The high-luminance monitor is a 21.3-inch IPS monochrome monitor with a maximum luminance of 3000 cd/m². Experiments were conducted with a minimum luminance of 0.6 cd/m² and a maximum luminance of 500, 850, and 1200 cd/m². The luminance ratio was set to 1 : 2000 and the maximum luminance was changed to 500, 1000, and 2000 cd/m². The ambient light was varied to 8.7, 36.1, 61.3, and 129.6 lx. The Japan Radiological Society recommended luminance values for each stage of phantom and Grayscale Standard Display Function curves were measured. Result: The JND increased as the maximum luminance was increased for both the case with the same minimum luminance and the case with the same luminance ratio, and visibility was improved. Conclusion: In both the case of the same minimum luminance and the case of the same luminance ratio, the JND was found to increase as the maximum luminance was increased. The results suggest that high-luminance monitors may improve visibility and allow for higher ambient light settings. Furthermore, the degree of eye fatigue needs to be verified.

The local dense area (LDA) test is a test for evaluating the stability of image quality published in the EUREF fourth edition-supplements for local high-density areas. In this test, a small PMMA plate imitating LDA is placed on a rectangular PMMA, and the exposure conditions and SNR are evaluated when the thickness is changed. In this study, we replaced the rectangular PMMA with a D-shaped PMMA phantom-like breast. Then, we inserted an implant and a muscle phantom simulating the pectoral muscle and varied the distance from the edge of the chest wall to a small PMMA plate. In most of the tests, the SNR was stable as the thickness of the small PMMA plate increased as the exposure conditions increased. However, the SNR was not stable because the exposure conditions were not appropriate depending on the insertion distance of the muscle phantom and the position of the small PMMA plate.

The average glandular dose (AGD) is very important in the quality control of mammography. The AGD calculation requires measurements of half-value layer (HVL) and entrance surface air karma (ESAK). The HVL is measured by the Al-attenuation method using a non-energy-dependent ionization dosimeter. As the Al-attenuation method performs measurements using a succession of added filters, it requires lots of X-ray exposure and measurement time. In recent years, measuring instruments that can measure tube voltage, irradiation time, exposure dose, HVL, and other factors, at the same time, using one shot of X-rays have been developed. In this study, measurement of the AGD using multiparameter X-ray measuring instrument about rhodium (Rh) and tungsten (W) anode X-ray tubes. A comparative study was performed using standard ionization dosimeters. The error in measurements was as follows: HVL 5.8%, ESAK 3.3%, and AGD 2.9%. The AGD measurement using a multiparameter X-ray measuring instrument is simple and can significantly reduce the measurement time while maintaining accuracy.

Purpose: The purpose of this study was to assess inter-rater reliability and workload for creating accurate training data in the clinical evaluation of mammographic positioning for deep learning. Methods: A total of 107 mammographic images without lesions were labeled by two certified radiologic technologists in seven items: six clinical image evaluation criteria in positioning and breast tissue density. The kappa coefficient was calculated as an indicator of interrater reliability. Furthermore, the labeling cost per image was calculated based on labeling time and salary for the technologists. Results: The kappa coefficients were 0.71 for inframammary fold, 0.43 for nipple in profile, 0.45 for great pectoral muscle, 0.10 for symmetrical images, and 0.61 for retromammary fat. No significant difference was found in the coefficients of spread of breast tissue. The cost per image was calculated at 11.0 yen. Conclusion: The inter-rater reliability for the inframammary fold, nipple in profile, great pectoral muscle, and retromammary fat ranged from “moderate” to “substantial.” The reliability for symmetrical images was “slight,” indicating the need for a consensus among evaluators during labeling. The labeling cost was equivalent to or higher than that of existing services.

Recently, mammography systems equipped with digital breast tomosynthesis (DBT) have become widely used in Japan. Therefore, it is urgently necessary to establish a quality control method for DBTs. So far, we have been studying acceptance tests for DBTs with reference to EUREF. In 2020, IEC 61223-3-6 was published, which provides not only acceptance tests but also constancy test methods. Therefore, we conducted data collection using DBTs sold in Japan and examined the feasibility of conducting constancy tests. Although there were some items that were difficult to implement in each device, we were able to confirm quality control items that could be implemented in many devices. In addition, we were able to confirm routine tests that enable rapid evaluation. Based on these results, we have developed a “Digital Breast Tomosynthesis Quality Control Manual”. In this paper, we report an overview of the manual and the results of routine tests.

It is important to make an appropriate diagnosis category by evaluating the morphology, blood flow, and hardness of mammary gland disease in breast ultrasound, such as screening and detailed examination. Therefore, understanding the characteristics and effects of B-mode (BM), color Doppler (CD), and elastography (EG) in ultrasonography is considered to lead to improvement in examination accuracy. In this study, we clarified the impact of each function on qualitative diagnosis, with the aim of assisting technologists with high-accuracy breast ultrasound. The subjects were 531 malignant tumor cases. The final evaluation of ultrasonography was classified into 5 levels, BM was classified into 5 levels, CD was classified into 4 levels based on blood flow evaluation, and EG was classified into 9 levels based on the Tsukuba elasticity score. The contribution rates of BM, CD, and EG were 70.4%, 15.0%, and 14.6% in all cases (correlation ratio 0.87). BM was most important at the time of breast ultrasound. No difference was observed between CD and EG. In the evaluation by malignant tumor, each characteristic was seen in the degree of influence. It became clear that comprehensive evaluation is important for benign/malignant evaluation and histological-type estimation.