To evaluate the degree of cerebral atrophy, quantification methods of a difference from a standard normal brain are often used in clinical practice. However, these methods may not evaluate the cerebral atrophy accurately, because they do not take into account any cerebral atrophies due to normal aging. The purpose of this study is to develop a model for taking into account the cerebral atrophy due to normal aging. We obtained 60 normal magnetic resonance (MR) images from the Alzheimer’s disease neuroimaging initiative database. These data included 20 images of each age group of 60’s, 70’s, and 80’s, respectively. For anatomical standardization of the images, we used the statistical parametric mapping software and employed a linear grayscale transformation. The principal component (PC) analysis with voxel values of 60 normal MR images was subsequently performed to calculate eigenvectors and PC scores. All cases were projected onto the eigenspace formed by 2^nd and 5^th PC scores. The experimental result showed separated distributions corresponding to the age groups. In addition, the sites of cerebral atrophy could be recognized by displaying eigenimages. Our proposed method would be useful for the accurate evaluation of cerebral atrophy caused by Alzheimer’s disease.

This study aimed to develop and evaluate field shape optimization technique based on dose calculation using daily cone-beam computed tomography (CBCT) to compensate for interfractional anatomic changes in three-dimensional conformal radiation therapy (3D-CRT) for prostate cancer. For each of 10 patients, 9–10 CBCT images were obtained throughout the treatment course. The prostate, seminal vesicles, and rectum were manually contoured in all CBCT images. Subsequently, plan adaptation was performed with a program developed in-house. This program calculates dose distributions on CBCT images and optimizes field shape to minimize rectal dose while keeping the target at the optimal dose coverage (the planning target volume D_95% receives 95% of the prescription dose). To evaluate the adaptive planning approach, we re-calculated dose distributions on CBCT images based on the conventional and adaptive plans. For the entire cohort, plan adaptation improved rectal V_{50 Gy}, V_{60 Gy}, V_{65 Gy}, and V_{70 Gy} by −7.71±8.43%, −8.30±8.90%, −7.91±8.51% and −7.03±7.70% on average (±SD), respectively. Our results demonstrate that adaptive planning approach is superior to the conventional planning approach for optimizing dose distribution, and this adaptive approach can optimize field shape in 3 min. The proposed approach can be an effective solution for the problem of interfractional anatomic changes in 3D-CRT for prostate cancer.

Automatic exposure control technology can reduce the radiation dose during CT. The purpose of this study is to reveal the important points regarding the usage of organ effective modulation (OEM), by evaluating the characteristics of OEM, an automatic exposure control technology. An analysis of the dosage profiles revealed that OEM may not work with the first rotation of the X-ray tube in the helical method and wide volume method. This phenomenon can be avoided by using the orbital synchronism helical method. This was also demonstrated upon measurement of the integrated absorption dose at the imaging start position. An analysis of standard deviation measurement revealed that with the combined use of OEM and x–y modulation, the reduction in dose may significantly vary depending on the presence or absence of the gantry tilt. Based on the above results, when using OEM to reduce the dose at the imaging start position, the combined use of x–y modulation should be avoided and the orbital synchronism helical method should be used.

In radiography with focused grid, it is important to agree the X-ray center on the grid center. Actually, radiography is often put the off-center alignment which disagrees the X-ray center to the grid center. This misalignment decreases radiographic contrast because of cutoff the primary X-rays. The grid-tilt technique which makes the grid tilt corresponding to the misalignment of the X-ray center and the grid center was investigated. Using solid state dosimeter and 10 cm water phantom, transited dose of focused grids (focal distance 120 cm, grid ratio 6:1 and 8:1) were measured at off-center. The transited dose at 6 cm off-center by conventional manner was lower 20% (6:1) and 30% (8:1) to center’s one. While by grid-tilt technique, the transited dose at off-center was same to the center’s one. Axial radiography of hip joint was applied by this technique.

The purpose of this study is to compare the physical characteristics and visibility of high-resolution and conventional images acquired with the same X-ray dose, and to investigate the superiority of super high-resolution imaging. A Catphan phantom was scanned in the normal resolution (NR), high-resolution (HR), and super high-resolution (SHR) modes of ultra-high-resolution computed tomography at 120 kV and 75 mAs. All images were reconstructed into a 5-mm thick image slices with filtered back-projection (FBP) and hybrid image reconstruction (HIR), which included normal and enhanced adaptive iterative dose reduction 3D (AIDR and eAIDR, respectively). The modulation transfer function (MTF) and noise power spectrum (NPS) were measured using the circular edge method and radial frequency method, respectively. The signal-to-noise ratio (SNR) was then calculated. High-contrast resolution and low-contrast detectability were evaluated visually by five radiological technologists. The MTFs of HR_eAIDR and HR_FBP images were higher than those of NR_FBP images. However, the NPSs of HR_eAIDR and HR_FBP images were larger than those of NR_FBP images. The SNR of HR_eAIDR images was higher than that of NR_FBP and HR_FBP images. The scores of high-contrast resolution of HR_eAIDR, NR_FBP, and HR_FBP images were 13, 8, and 13 cycles/cm, respectively, and the scores of low-contrast detectability were 5, 5, and 6 mm, respectively. Hence, an improvement in high-contrast resolution of signal more than 400 HU in the axial section can be achieved without increasing the radiation dose and decreasing low-contrast detectability with 10 HU using the HR mode and eAIDR.

The restlessness of young children often causes motion artifacts on CT images. We devised a new animation projector system (CT Theater) that enables a child to view an animation during a pediatric head CT examination. The purpose of this study is to assess the usefulness on a children of a video viewed during a head CT scan. Children of 3–10 years old who underwent head CT (SOMATOM Definition Flash, SOMATOM Force; Siemens) were analyzed for a period from 6 months before, to 6 months after, introduction of the projector system (before: n=46, after: n=29). Mobile projector (MP-CL1; Sony) connected with tablet device (iPad; Apple) was put on the CT table near the child’s head. An animation was projected on the child’s line of sight inside the gantry. The animation is projected on the line of sight of the child such that the projector moves with the child on the table. The number of requests for use made by children was 28/29 (96.6%). The presence of images without motion artifacts decreased significantly after introduction (before/after introduction: 84.8% vs 100%, p=0.03). The overall examination success rate tended to increase after introduction (84.8% vs 92.9%, p=0.26). The overall examination time was significantly reduced (92.4±42.4 s vs 65.1±47.3 s, p<0.001). We developed an animation projector system that shortened examination time and decreased motion artifacts in pediatric head CT.

The present study grasped the radiation exposure per examination by incident air kerma (air kerma-area product; KAP and incident air kerma; K_{a, e}) using an air kerma-area product meter of our division with mobile population based gastric cancer screening. Initially, we measured the air kerma rate at the patient entrance reference point using an air kerma-area product meter and calibrated dosimeter, for three devices which an air kerma-area product meter was equipped, inspected the indication error of them. The error was 4.3% at the maximum, and accuracy was confirmed. The 816 patients who underwent gastric cancer screening in our division, the median values of KAP and K_{a, e} of the standard gastrography method 1 were 645.7 mGy·cm², 37.4 mGy, respectively. The radiation dose of males were significantly higher than females, and the radiation dose increased in proportion to the BMI. The median values of calculated KAP and K_{a, e} of the standard gastrography method 1 for standard body size were 633.8 mGy·cm², 37.0 mGy, respectively. We suggest that the patient exposure in gastrography can be optimized using an air kerma-area product meter.

Radionuclide therapy has been used to help manage a range of diseases and has a role of growing importance, with an increasing impact on clinical practice globally. A survey in the field of Radionuclide therapy was conducted by reviewing 4199 science abstracts of main conference (Japanese Society of Radiological Technology, Japanese Society of Nuclear Medicine, Japanese Society of Nuclear Medicine Technology, Society of Nuclear Medicine and Molecular Imaging, European Association of Nuclear Medicine) held in 2016. This survey consisted of research content, modality for evaluation, dosimetry, radionuclide, and researcher’s country. There tend to be a lot of studies related to targeted radionuclide therapy more than Japan (4%) in the United States (11%) or Europe (13%). Radiopharmaceuticals still un-approving in Japan were used in some of these studies. And many studies on dosimetry using PET or SPECT imaging were confirmed in the United States (37%) or in Europe (25%) compared with in Japan (14%). This survey has clarified the current status of Japan and global trend in the field of radionuclide therapy.