Complex procedures for interventional radiology can result in high radiation doses to patients and physicians. A spectral shaping filter (SSF) has recently been developed and equipped with angiographic systems to modulate the X-ray beam spectrum. In our feasibility study, the radiation doses to patients and physicians, air kerma rate at image receptor, and image quality were evaluated when SSF was applied in fluoroscopy. Polymethyl methacrylate (PMMA) phantom, a catheter attached on the bottom was placed on the examination table. The entrance air kerma rate at patient entrance reference point, H* (10) rate at a distance of 100 cm from the center of PMMA, air kerma rate at image receptor and the fluoroscopic catheter images were recorded as a function of PMMA thickness. Contrast-to-noise ratio (CNR) was used for the objective image quality. As a subjective image quality evaluation, three physicians (cardiologist, neurologist, and radiologist) rated the catheter images by a Likert scale. With SSF, the entrance air kerma rate and H* (10) rate reduced by about 34 and 21%, respectively. The air kerma rate at image receptor in conventional filter mode increased when the PMMA was up to 10 cm and then CNR was also improved. However, no significant differences were found in the subjective image qualities. In conclusion, SSF was contributed to the reduction of the radiation doses to patients and physicians while the subjective image quality was not affected.

Subtype classification of breast cancer by analyzing the gene expression profile of cancer cells is becoming a standard procedure. Breast cancer subtype classification is more useful than the conventional method because the characteristics of subtype classification is directly connected with the treatment method. However, genetic testing is invasive, and a part of cancer cells may not represent the overall nature of the cancer. In the computer-aided diagnosis (CAD) scheme for differentiation of triple-negative breast cancer (TNBC) by estimating the genetic properties of cancer based on Radiogenomics, principal component analysis (PCA) and least absolute shrinkage and selection operator (Lasso) were used for reducing the dimension of radiomic features, and we compared usefulness of both. We collected 81 magnetic resonance (MR) images, which included 30 TNBC and 51 others, from the public database. From the MR slice images, we selected the slice containing the largest area of the cancer and manually marked the cancer region. We subsequently calculated 294 radiomic features in the cancer region, and reduced the dimension of radiomic features. Finally, linear discriminant analysis, with the dimensionally compressed 10 image features, was used for distinguishing between TNBC and others. Area under the curve (AUC) was 0.60 when we used PCA, whereas AUC was 0.70 when we used Lasso (p=0.0058). Therefore, Lasso is useful for the determination of radiomic features in Radiogenomics.

To simplify a procedure of the observer study with Ura’s method of Scheffé’s paired comparison and to improve experimental accuracy, we developed a software package to automatically analyze observer study data obtained by using a computer interface developed specially for the ROC observer study. Simulated low-dose CT images were used to demonstrate practical utility of this proposed method with a software package, in terms of a statistical analysis of the change of noise property due to the change of exposure dose. Six radiological technologists were participated in this observer study and compared each of six sample images selected at lower lung and liver slices with dose levels of 100, 80, 60, 40, 20, 10% per case. In the statistical analysis, the average psychological measures were highly correlated with the dose levels (lower lungs: R=0.95, liver: R=0.99). In addition, there were statistically significant differences in all combination of dose levels in liver slices. In conclusion, we demonstrated practical utility of this proposed method in terms of simplification of experimental procedure and the consistency of the analytic results.

In many facilities, the displayed dose of dose-area product (DAP) is used for the dose management of interventional radiology. In this study, we investigated the measured dose at the patient entrance reference point (interventional reference point) and the displayed dose on each angiography systems. Also, we investigated the calibration method of each DAP. The errors of the measured dose and the displayed dose were less than 35%, but that dispersion was wide between the systems. The calibration methods varies according to a system. And even in the same manufacturer, the calibration methods were different. Therefore, to use the displayed dose of DAP for patient dose management, we need to compare that with the measured dose regularly. The differences of calibration methods induce the wide dispersion of the errors of the measured and the displayed dose. So the standardization of the calibration method in each manufacturer is expected.

Brain T₁-weighted images using spin echo (SE) sequence has poor contrast at 3.0 Tesla magnetic resonance imaging (3.0 T MRI) systems from the influence of crosstalk and magnetized transfer (MT) effect, and prolongation of the T₁ value. Therefore, improving of scan parameters has been reported such as excitation flip angle (FA) and interleave data acquisition. The purpose of this study was to show the effects of alterations of presaturation pulse amplitude and chemical shift selective (CHESS) pulse amplitude. Gray-to-white matter contrast increased with decreasing amplitude of presaturation pulse in whole brain imaging. Presaturation and CHESS pulse consist of radio frequency pulse. Therefore, both pulses have a similar effect on MT pulse. Manual alteration of presaturation pulse amplitude for each scan lacks versatility on clinical use. However, decreasing amplitude of presaturation pulse is equal to decreasing thickness of presaturation pulse. About CHESS pulse, it requires no manual alteration for each scan. For example, switching fat suppression mode from strong to weak increase T₁ contrast. Our study demonstrated that using not only low excitation FA and interleave date acquisition but also low amplitude of presaturation and CHESS pulse increase the contrast in T₁ SE brain scans at 3.0 T MRI.

We have conducted a questionnaire survey every 5 years from 1974 to grasp the existing status of X-ray equipment. This time, we will report on the results of the fiscal 2015 diagnostic X-ray equipment questionnaire survey. Compared to the previous survey on X-ray equipment, there has been a progress in the introduction of inverter type X-ray generators and image receptor systems in digital systems. We think that this transition will be occurred when the X-ray equipment are updated. In addition, there has been an increase in digital breast tomosynthesis (DBT) and the use of tungsten anodes in the X-ray tubes of mammography apparatuses. X-ray equipment management was performed in many facilities. It seems that the importance of quality control of X-ray equipment is being realized. Constancy tests corresponding to digital systems were conducted at each facility. Maintenance by manufacturers has also increased. This is considered to be because the equipment management of digital systems has become difficult. We believe that it is necessary to continue the survey on the status of diagnostic X-ray equipment.

Purpose: We investigated the way of thinking about the CT dose setting, the exposure dose (CTDI_vol, DLP) and the image quality (standard deviation of liver: SD_liver) of whole-body PET/CT examinations in the Chugoku and Shikoku regions for the optimized CT dose setting. Method: It was researched in the target 29 facilities which is equipped with ¹⁸F-FDG, PET/CT scanner in that regions. We examined how to determine the dose of complete physical PET/CT setting, the CT radiation dose (CTDI_vol and DLP) and the image quality of CT fusion image that is the standard deviation of liver CT value in each facility. Result: The optimized CT dose was lower than the diagnostic CT in many facilities. The 75^th percentile CTDI_vol was 6.01 mGy. The 75^th percentile DLP was 560.9 mGy ×cm. The SD_liver was 14.6±5.3 HU. Conclusion: The CT condition was low setting in comparison with diagnostic CT in many facilities. The exposure dose was lower than the diagnostic CT dose. The image quality of the normal region of liver was very close to the diagnostic CT. Even though it was low dose, images were less noise components.