The influence of crosstalk on the fast fluid attenuated inversion recovery(fast FLAIR)pulse sequence was studied. On multislice fast FLAIR images, the water null point was shortened in comparison with that on single slice images owing to the crosstalk received from adjacent slices. That influence became greater with decreases in the slice gap and increases in the number of slices. The timing of crosstalk in each slice varied according to excitation order. The process of recovery of longitudinal magnetization changed according to differences in timing ; thus, it was possible that the water null point changed in each slice. In brain images with thinner slice gaps, the signal intensity of CSF is increased by the effect of crosstalk. In order to eliminate changes in the water null point caused by crosstalk on fast FLAIR, the multislice sequence requires a sequence with interleaving based on the premise that slice gaps are set for more than 100% of slice thickness.
The dose distribution of proton beams with depth exhibits a strong Bragg peak at the end of the range, beyond which the dose rapidly falls to zero. These qualities make these beams particularly suitable for tumors situated near critical organs, where there is a high demand for accurate dose delivery. In proton dosimetry, we studied the scatter-to-primary dose ratio(SPR), which is used for dose evaluation in high-en-ergy photon beams. The formula for SPR calculation was developed by Ceberg et al. The maximum energy of the proton beam used in this study was 70 MeV, produced by an isochronous cyclotron. We assumed that SPR could by separated into longitudinal and lateral components that are dependent on depth(Z)and field radius(R), such that SPR(Z, R)=SPR(Z)・SPR(R). In particular, the effect of the longitudinal component on the shift of the spread-out Bragg peak(SOBP)was examined. The results showed that SPR(Z)of the lonitudinal component decreased with decreasing water depth and SPR(R) of the lateral component decreased with decreasing field size.
The importance of informatics in the education of medical and nursing students has been widely recognized in recent years, and many curricula in information literacy have been proposed. Students of radiological technology, as well as other medical students, need these curricula. We had the opportunity to teach "Practice in Radiation Protection" to junior and senior students, and to use problem-solving group learning. This course consisted of 13 sessions. The contents included introductory lectures on informatics, the critical reading of an epidemiological paper written in English, and a problem-solving exercise carried out in a small group setting. In the exercise, students chose one theme related to medical informatics, health science, or radiation protection. After collecting information on this theme, they presented a report to the class. A questionnaire given to students after the course work had finished pointed to certain problems. These problems included difficulty in being able to read the English paper, group work, and insufficient time for the exercise. Ninety-percent of the students reported that they had gained a positive attitude toward problem solving as a result of the exercise.
Two kinds of gastric images of 85 examinees were compared in order to study the procedure of giving barium meal and forming agents The more recent images were obtained with examinees given a barium meal followed by a forming agent, whereas the other images were of the same examinees obtained the previous year, with the foaming agent given before the barium meal. Results showed that when the barium meal was given first, the mucous membrane of the stomach was imaged better. In contrast, when the forming agent was given first, sodium tartrate, derived from the foaming agent, was considered to cover the mucous membrane and physically to prevent the barium meal from clinging to the membrane.
Scattered radiation levels near ana imaging system commonly used in angiography were measured with a 200 mm thick water phantom. The scattered radiation exposure rate was measured in lines parallel in space to the central ray of the x-ray beam, at lateral distances of 30-100 cm. The effects of an x-ray beam limiting device, geometric and electric magnification, and rotation angle of the C-arm were also determined. The results indicated that the highest scattered radiation levels occurred near the surface of the phantom where the x-ray beam enters. In P-A geometry, the highest radiation levels occurred below the angiographer's waist. These areas of the body corresponded to the gonads of the angiographer. It has been suggested that angiographers' exposure rates are higher near the gonads than near the chest. However, lead aprons efficiently protect these areas. When smaller field sizes were limited by a variable x-ray beam limiting device, the volume of irradiated tissue was reduced, and the scattered radiation exposure rate was decreased. Further, when larger magnification factors were chosen for the analogue magnification method, the volume of irradiated tissue was reduced by the automatic x-ray beam limiting device, and the scattered radiation exposure rate was decreased. However, smaller field sizes markedly increased patient exposure by auto brightness control. To mitigate the angiographer's exposure, smaller field sizes with x-ray limiting devices are required. However, a larger field size should by used whenever possible to minimize patient exposure. The angiographer's exposure rate was influenced by the incidence direction of the x-ray beam when the C-arm had been rotated around the phantom. Consequently, the angiographer's exposure rate was maximum when the x-ray tube most closely approached the angiographer and was minimum when the image intensifier most closely approached the angigrapher. Therefore, to mitigate the angiographer's exposure, attention needs to be given to the incidence direction of the x-ray beam.