鈴木 昇一

Diagnostic reference levels (DRLs) for mammography have yet to be created in Japan. A national questionnaire investigation into radiographic conditions in Japan was carried out for the purpose of creating DRLs. Items investigated included the following: tube voltage; tube current; current-time product; source-image distance; craniocaudal view; automatic exposure control (AEC) settings; name of mammography unit; image receptor system (computed radiography (CR), flat panel detector (FPD), or film/screen (F/S)); and supported or unsupported monitor diagnosis (including monitor resolution). Estimation of the mean glandular dose (MGD) for mammography was performed and compared with previous investigations. The MGD was 1.58(0.48) mGy, which did not significantly differ from a 2007 investigation. In relation to image receptors, although no difference in average MGD values was observed between CR and FPD systems, F/S systems had a significantly decreased value compared to both CR and FPDs. Concerning digital systems (FPDs), the MGD value of the direct conversion system was significantly higher than the indirect conversion system. No significant difference in MGD value was evident concerning type of monitor diagnosis for either the CR or the FPD digital systems; however, hard copies were used more often in CR. No significant difference in the MGD value was found in relation to monitor resolution. This report suggests ways to lower the doses patients undergoing mammography receive in Japan, and serves as reference data for 4.2 cm compressed breast tissue of 50% composition DRLs. Furthermore, our findings suggest that further optimisation of FPD settings can promote a reduction in the MGD value.

Our aim in this study was to investigate the incident air kerma (IAK) and average glandular dose (AGD) for polymethylmethacrylate (PMMA) phantoms and patient breasts for each thickness by use of digital mammography units, and to determine the correlation between phantom and patient measurements. An additional aim was to calculate the numerical value of the diagnostic reference level (DRL) for digital mammography in Japan based on the AGD from patient measurements. Patient-based IAK and AGD values were calculated for 300 patients who underwent mammographic examinations at three institutions. On examination of a 40-mm PMMA phantom, the IAK and the AGD were 7.89 and 1.84 mGy, respectively. The mean patient breast thickness was 37.6 mm, and the mean IAK and the AGD calculated from actual patient data for breast thicknesses between 40 mm and 50 mm were 8.91 and 2.08 mGy, respectively. Approximately 20% of the 300 patients had IAK &gt 10 mGy. The distributions of patient-based IAK and AGD values were higher than the IAK and AGD values for the PMMA phantom. The patient dose with use of the PMMA phantom can be underestimated. The DRL was calculated from patient-based AGDs of the regular breast thickness as 2.0 mGy in Japan. © Japanese Society of Radiological Technology and Japan Society of Medical Physics 2013.

Background: Although different gait analysis methods such as Walking Track Analysis exist, they cannot be used to demonstrate the physical condition of mice with specific gait disorder characteristic. Therefore, we developed a new method for the gait analysis of such mice to accurately assess hind limb angle based on the pelvic axis. New method: We established and verified a gait analysis method capable of pelvic axis-based limb angle measurement by video-recording the gait of a control mice group (C57BL/6J(B6)) and three ataxic mice (ataxic B6-wob/t, Parkinson's disease model (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine treated (MPTP)), and cerebellum hypoplasia (cytosine-beta-D-arabinofuranoside treated)) from the ventral side. Results: The assessed hind limb angles of B6-wob/t and MPTP-treated mice were significantly wider than B6 mice (p<0.01). Moreover, we could draw separating lines with slopes of minus one that could separate the data of each group in-the scatter plot of the normalized hind limb step width and angle. Comparison with existing methods: We found no significance when we applied the already existing nose-tail method for the analysis of the hind limb angles of B6 and B6-woblt mice. In the nose-tail method, since the whole body axis of the trunk varies while the trunk of the mouse is laterally bent changing the hind limb angle, B6 and B6-wob/t mice could not be differentiated. However, the two mice groups could be differentiated by the pelvic axis-based gait analysis method. Conclusion: The pelvic axis-based gait analysis method is promising and valid for mice with gait disorder. (C) 2013 Elsevier B.V. All rights reserved.