In order to use the practical training for beginners by means of a diagnostic X-ray, a leaf electroscope (which has a function to explain the ionization) was newly produced. The X-ray was introduced to the air in the electroscope having the electric charged leaf (the leaf was open at this time). The air irradiated by the X-ray was ionized, and then the produced ions or electrons were combined with charges on the leaf. As a result, the leaf was closed. In this way, experimenters can know the production and/or movement of charges by observing the conditions of the leaf. For the developed leaf electroscope, we added separators to divide the inner space into two regions; one is the irradiation area and the other is the space including the leaf. The separators have through-holes and/or a metallic mesh in order to create various conditions. In this paper, we described that different experimental results based on uses of the different separators were reflected in the ionization of the irradiated air and in the interaction of the charged particles. We summarized that the practical training by means of the developed leaf electroscope was valuable to educate beginners.
Background: It is possible to obtain equivalent image quality and a lower radiation dose using low tube current scanning with full reconstruction as compared to usual tube current scanning with half reconstruction in a 320-row area detector computed tomography (ADCT) angiography. Method: Of 589 patient underwent coronary CT angiography (CCTA), 11 patients with (RR-PQ) ≥1069 ms were enrolled. In those patients, low tube current (50% mA) scanning with full or half reconstruction were performed. As a control, 11 patients with matched pairs of tube voltage, BMI and heart rate who underwent usual scanning with half reconstruction (100% mA with half reconstruction) were selected. Standard deviation of the CT value (SD) was measured in aorta (Ao), left atrium (LA) and left ventricle (LV), and extended dose-length products (DLP.e) were calculated. Result: Significant motion artifact was not observed in any patients. SD of 50% mA with half reconstruction, 50% mA with full reconstruction, and 100% mA with half reconstruction were 28.1±2.6, 20.3±1.9, 20.7±2.5 HU in Ao, 34.4±4.4, 24.9±2.8, 24.9±3.1 HU in LA, and 29.7±2.3, 21.7±1.9, 22.1±2.3 HU in LV, respectively. There were not significant differences between 50% mA with full reconstruction and 100% mA with half reconstruction, but there were significant differences between 50% mA with half reconstruction and 50% mA with full reconstruction in all sites. The DLP.e of 50% mA scanning (74.1±21.8 mGy·cm) was significantly lower than 100% mA scanning (161.9±28.9 mGy·cm). Conclusion: CCTA with lower radiation dose and equivalent image quality can be obtained by ADCT using 50% mA scanning with full reconstruction in patients with (RR-PQ) ≥1069 ms.
Conventional radiography is first performed in the evaluation of knee osteoarthritis (OA). In view of diagnostic accuracy and reproducibility, joint space narrowing that is a typical feature of knee OA should be evaluated quantitatively based on the image findings, because it has been evaluating subjectively. We measured joint space widths and joint space areas on knee radiographs to analyze joint space narrowing quantitatively and investigated the usefulness in classification of the severity of knee OA. Radiographs of 35 no OA knees (normal group) and 46 OA knees (OA group) were analyzed in this study. Medial and lateral joint space width and joint space area were measured manually using ImageJ i.e., a public domain image processing program. Measured values were corrected for the physical size with the length of epicondylar line, and statistically significant differences between the normal group and OA group were investigated. The results showed that medial joint space width was significantly smaller and lateral joint space width was significantly larger in the OA group than in the normal group. Furthermore, joint space area in the OA group decreased significantly compared that in normal group. We conclude that joint space widths and joint space area are important parameters to classify the severity of knee OA.
We believe that the patient exposure dose differs by heart rate for a coronary computed tomography angiography (CCTA), and we attempted to reduce patient exposure dose of the CCTA. Specifically, we made a clear difference of exposure dose between heart rate and optimal cardiac phase or some imaging methods. Next, we established criterion of the CCTA in our hospital, and usefulness was discussed. For examination methods, patients with a heart rate below 60 beats per minute (bpm) received a high-pitch spiral scan (Flash Spiral mode), those between 61 to 70 bpm received a step and shoot scan (SAS mode), and those of >70 bpm or an irregular heart rate received low-pitch spiral scan (Helical mode). The results of the clinical study showed that patient exposure dose reduced 87% in Flash Spiral mode (1.93±0.26 mSv) and 66% in SAS mode (4.88±1.24 mSv) compared with Helical mode (14.35±3.42 mSv). In our present study, we proved the usefulness of our criteria using CCTA. If the results of our present study become guidelines of CCTA users, we suggest that total patient exposure dose can be reduced.
In magnetic resonance imaging (MRI), skin markers are used as a landmark in order to make plans for examinations. However, there isn’t a lot of research about the material and shape of skin markers. The skin marker’s essential elements are safety, good cost performance, high signal intensity for T1 weighted image (T1WI) and T2 weighted image (T2WI), and durable. In order to get a high signal-to-noise ratio (SNR) of T1WI and T2WI, baby oil, salad oil and olive oil were chosen, because these materials were easy to obtain and safe for the skin. The SNR of baby oil was the best. Baby oil was injected into the infusion tube, and the tube was solvent welded and cut by a heat sealer. In order to make ring shaped skin markers, both ends of the tube were stuck with adhesive tape. Three different diameters of markers were made (3, 5, 10 cmφ). Ring shaped skin markers were put on to surround the examination area, therefore, the edge of the examination area could be seen at every cross section. Using baby oil in the ring shaped infusion tube is simple, easy, and a highly useful skin marker.
In magnetic resonance imaging (MRI), we can use sensitivity encoding (SENSE) as a parallel imaging reconstruct from aliasing based on the sensitivity map of each coil element by reference scan. We researched SENSE reconstruction depending on the position of the reference scan. 1.5 T MRI (Achiva, Philips), 32-channel SENSE cardiac coil and rectangular solid phantom (nickel chloride) were used. Seven slices (A to G: from head to foot) were set at the phantom, slice thickness was 1 cm, and each slice interval was 5 cm. When T2 weighted axial images (TR: 3000 ms, TE: 120 ms) were taken, the center of the reference scan (C-Ref) was changed A to G, SENSE factor was changed 1 to 5, and number of signals averaged (NSA) was changed 1 to 3 with fold over suppression. Signal-to-noise ratio (SNR) and coefficient of variation (CV) from 9 regions of interest (ROI) of axial images were calculated. The SNR of slices A and G were lower than the other slices. %CV of slices F with C-Ref D was 69.4% lower than C-Ref A. %CV of slices D to F were higher than the other slices when C-Ref was A. %CV had no relation with SNR. Therefore, a 30 cm area around the center of reference can obtain best SENSE reconstruction.
Decay-in-storage for radioactive waste including that of nuclear medicine has not been implemented in Japan. Therefore, all medical radioactive waste is collected and stored at the Japan Radioisotope Association Takizawa laboratory, even if the radioactivity has already decayed out. To clarify the current situation between Takizawa village and Takizawa laboratory, we investigated the radiation management status and risk communication activities at the laboratory via a questionnaire and site visiting survey in June 2010. Takizawa laboratory continues to maintain an interactive relationship with local residents. As a result, Takizawa village permitted the acceptance of new medical radioactive waste containing Sr-89 and Y-90. However, the village did not accept any non-medical radioactive waste such as waste from research laboratories. To implement decay-in-storage in Japan, it is important to obtain agreement with all stakeholders. We must continue to exert sincere efforts to acquire the trust of all stakeholders.
A comparison of absorbed doses to water at a calibration depth determined by Japan Society of Medical Physics (JSMP) 12 and 01 was conducted, using a farmer type ionization chamber. The absorbed dose to water calibration factor (ND,W,Q0) and beam quality conversion factor (kQ,Q0) for JSMP 12 were smaller than the absorbed dose to water calibration factor and beam quality conversion factor for JSMP 01. Differences in absorbed doses at a calibration depth were -0.78% for 6 MV photon beam and -0.94% for 10 MV photon beam. In the present experiment, absorbed doses at a calibration depth were measured, using a farmer type ionization chamber. Further experiments at a larger number of facilities should be conducted to reveal the status of measurement of absorbed doses at a calibration depth using JSMP 12.