Purpose: This study was designed to assess working environment preferences of students in the Department of Radiological Technology using conjoint analysis for establishing an efficient medical system. Method: We carried a questionnaire survey on working environment preferences for 196 students in the Department of Radiological Technology in Japan. We defined eight characteristics for virtual medical facilities as follows: presence of colleagues who can be consulted, employment status, number of night shift per month, academic meeting participation, number of hospital beds, possession of nuclear medicine imaging systems and radiation therapy systems, location of medical facilities, and change rate in annual income. A total of 18 virtual medical facilities were selected by an orthogonal array table using above-mentioned characteristics. The acquired data by the pairwise comparison method were analyzed by conjoint analysis. Marginal rates of substitution that represent students’ preferences were also calculated. Result: The factors that influenced their preferences were the following: placement of medical facilities in great city, presence of colleagues who can be consulted, employment status is not non-regular employment, set up of nuclear medicine imaging systems and radiation therapy systems, the number of night shift is twice per month, and attendances at academic meetings. Conclusion: In summary, students in the Department of Radiological Technology tend to prefer the facilities with regular employment, great city, presence of colleagues who can be consulted, and possession of nuclear medicine imaging systems and/or radiation therapy systems.
Purpose: Using a pediatric head phantom constructed in our department, we examined a method to reduce exposure by using organ-effective modulation (OEM; Toshiba Medical Systems Corporation, Tochigi) to tilt the gantry during pediatric head computed tomography (CT) scanning. Method: The radiation reduction and CT image standard deviation (SD) were measured at gantry angles at which the orbit was slightly irradiated, partially irradiated, and completely irradiated. The OEM incident surface dose reduction rate was measured using an automatic exposure control (AEC) phantom with a diameter of 6–18 cm. Results: The lens surface dose reduction rate using OEM was 21.2%. When the gantry was tilted and the orbit was completely out of the scanning range, the rate of reduction was 47.8%. OEM incident surface dose reduction rates were 27.4% for a phantom diameter of 18 cm, 22.0% for that of 16 cm, 17.8% for that of 14 cm, 17.2% for that of 12 cm, 8.4% for that of 10 cm, and 0% for that of 8 cm and 6 cm. OEM effectiveness decreased with decreasing phantom diameter. The use of OEM increased the rate of change of SD by 1.25´ when the gantry inclination was 0°, 1.27´ when the gantry inclination was 10°, and 1.27´ when the gantry inclination was 20°in the 12 o’clock position. Conclusion: The degree of reduction in exposure dose to the lens in pediatric head CT imaging was 47.8% by completely removing the lens from the irradiation range using gantry tilt and 21.2% by using OEM. The effect of OEM changed in proportion to tube current. The exposure reduction effect of the OEM decreases with decreasing head size, indicating its reduced effectiveness in head CT scans of smaller infants.
Objectives: Optimal beam quality for detection of pulmonary nodules in digital chest radiography using CsI-flat panel detector (FPD) was investigated in consideration of image quality and patient dose. Methods: The human chest phantom with inserted imitated nodules (diameter: 10 mm, CT value: +30 Hounsfield unit (HU), –375 HU, –620 HU) was used for the measurement of contrast-to-noise ratio (CNR) of imitated nodules by twenty beams arranged by five tube voltages and four filters. Results: The CNR varies with X-ray tube voltage and added filter. CNR correlates weakly to the tube voltage, fairly to the effective energy in second-order polynomial and strongly to the quality index (effective energy divided X-ray tube voltage). In order to improve the CNR, the effective energy and the quality index are kept about 50 keV and more than 0.5, respectively, using an 80–100 kV beam with a copper filter. Conclusion: A 90 kV (2.5 mm Al inherent filtration) beam with a 0.15 mm copper filter and a 90 kV or 100 kV (2.5 mm Al inherent filtration) beam with a 0.2 mm copper filter are appropriate for chest radiography using CsI-FPD.
The purpose of this study is to examine the maximum brightness of the monitor, which is suitable for radiological technologistsʼ (hereinafter referred to as technicians) interpretation assistance and image inspection. The signal detection ability was evaluated by receiver operating characteristic (ROC) analysis using a chest X-ray image with a simulated nodule. In order to examine the ease of observation and the effect on the subjective evaluation by changing the maximum brightness, evaluation was performed by the normalized ranking method using chest X-ray images. ROC experiments were performed using images with and without simulated nodules in the chest phantom. There was no significant difference in detectability by changing the maximum brightness (p>0.05), but the average area under the curve (AUC) was higher at 350 cd/m2 than at 100 cd/m2 and 170 cd/m2. A normalized ranking method was performed focusing on simulated nodules on chest X-ray images. In the least significant difference (l.s.d.) method, there was a significant difference between the maximum luminance, and the higher the maximum luminance, the better the evaluation. From these results, the change in the maximum brightness did not significantly affect the signal detection ability of the technicianʼs chest X-ray image, but the higher the maximum brightness, the easier it was to observe and the higher the subjective evaluation. It has been reported that the higher the maximum brightness, the shorter the signal recognition time, and a monitor with a high maximum brightness may lead to more efficient image inspection by a technician. From the results of this study, it is considered appropriate to use a medical liquid crystal display (LCD) monitor with a maximum brightness of 350 cd/m2 for the technicianʼs interpretation assistance and image inspection.
In proton magnetic resonance (MR) spectroscopy (1H-MRS) of the breast cancer, choline peak could be detected. The purpose of this study was to evaluate the influences of the tumor volume, full width at half maximum (FWHM) of the water peak (FWHM), and T2* value of water (T2* value) on the detection rate of the choline peaks at 3.0 T-MRI. We measured FWHM and T2* value in 109 cases, and we evaluated the effect of tumor volume on the detection rate of the choline peaks and the effect of FWHM and T2* value on the detection of choline peaks. In 1H-MRS of breast cancer at 3.0 T-MRI, the detection rate of the choline peaks improved as the tumor volume was larger. As a shimming environment when acquiring 1H-MRS of breast cancer, FWHM is preferably 57.4 Hz or less and T2* value should be 11 ms or more, and T2* value has a great influence on the detection rate of the choline peaks.
Purpose: In 2011, the International Commissionon Radiological Protection (ICRP) recommended reducing the threshold dose for the lens. Therefore, it is important to reduce the lens exposure dose in medical exposures. In a cranio-caudal (CC) view of mammography, the patient’ s lens receives scattered radiation. In this study, we investigated scatter dose around the lens during mammography and reviewed the simple and easy protection methods of the lens. Methods: Optically stimulated luminescence (OSL) dosimeters were placed in front of the device to obtain scattered radiation intensity distribution. The human phantom was placed in the same way as the CC positioning, and BR-12 phantoms with a thickness of 40 mm was placed on the FPD. Then, the scatter dose around the lens was measured using an OSL dosimeter. In order to confirm the change in the scatter radiation dose by the face guard (FG) and eyelid, we measured and compared under the same conditions the presence of FG and adipose tissue about 1 mm thick assuming the eyelid. Results: Scatter radiation intensity decreased around the FG. When the FG was installed, the scatter dose was reduced about 33%, and when the adipose tissue was pasted on the OSL dosimeter, the scatter dose was reduced about 29%. Conclusion: This study suggested that eye closure during mammography was effective in reducing lens exposure. In the future, we would like to expect further protective effects by increasing the thickness of FG and reviewing the materials.
In a previous issue of this journal, we published a report entitled “Creation of Stereo-paired Bone Anatomical Charts Using Human Bone Specimens for Radiation Education” To understand how the bone specimen is visualized as an X-ray image, we newly created a bone specimen stereo-paired X-ray anatomical chart by adding the X-ray images of the same bone specimen. When a bone is X-rayed, the surface structure and internal structure of the bone are visualized as a composite image of the difference in X-ray absorption, and each bone becomes a unique X-ray image. Therefore, we took stereo-paired X-ray images of the bone specimens by the same method as the stereo-paired anatomical chart of the bone specimens. Then, we arranged the stereo-paired X-ray images and surface images of the same bone specimen in the one sheet to be readily compared. Similar to the previous bone specimen anatomical charts, these data of X-ray image anatomical chart were also made into an electronic file, so that we can do the three-dimensional observation of bone X-ray images even at the place of radiological examination or at home through electronic media. Until now, none of the specialized anatomy books and pictorial books are available for stereoscopic viewing of bone specimens and bone X-ray images. However, this stereo-paired X-ray image anatomical chart enabled us to learn accurate three-dimensionalization of bones by comparing the bone surface morphology and bone X-ray images.