Contrast-enhanced magnetic resonance angiography (CE-MRA) is frequently performed in body and extremity studies because of its superior ability to detect the vascular stenosis. However, nephrotoxicity of the contrast medium has been emphasized in recent years. Non-contrast MRA using the three-dimensional electrocardiogram-synchronized fast spin echo method (FBI, NATIVE and TRANCE) is recommended as a substitute for CE-MRA. There are a few reports in the literature that evaluate the detectability of vascular stenosis using non-contrast MRA on 3.0 T MRI. The purpose of this study was to evaluate the detectability of vascular stenosis using non-contrast MRA at 3.0 T with an original vascular phantom. The vascular phantom consisted of silicon tubes. 30% and 70% stenosis of luminal diameter were made. Each silicon tube connected a pump producing a pulsatile flow. A flowing material to was used in this study to show the similarity of the intensity to blood on MRI. MRA without a contrast medium (NATIVE sequence) were performed in the vascular phantom by changing the image matrix, static magnetic field strength and flow velocity. In addition, the NATIVE sequence was used with or without flow compensation. Vascular stenosis was quantitatively estimated by measurement of the signal intensities in non-contrast MRA images. MRA with NATIVE sequence demonstrated an accurate estimation of 30% vascular stenosis at slow flow velocity. However, 30% stenosis was overestimated in cases of high flow velocity. Estimation was improved by using a flow compensation sequence. 70% stenosis was overestimated on MRA with NATIVE sequence. Estimation of 70% stenosis was improved by using a flow compensation sequence. Accurate estimation of vascular stenosis in MRA with a NATIVE sequence is improved by using the flow compensation technique. MRA with NATIVE sequence is considered to be a promising method for the evaluation of patients with severe renal dysfunction as a substitute for CT angiography or CE-MRA.
In optimizing exposures, it is very important to evaluate the impact of image noise on image quality. To realize this, there is a need to evaluate how much image noise will make the subject disease invisible. But generally it is very difficult to shoot images of different quality in a clinical examination. Thus, a method to create a noise addition image by adding the image noise to raw data has been reported. However, this approach requires a special system, so it is difficult to implement in many facilities. We have invented a method to easily create a noise addition image by using the water phantom and image add-subtract software that accompanies the device. To create a noise addition image, first we made a noise image by subtracting the water phantom with different SD. A noise addition image was then created by adding the noise image to the original image. By using this method, a simulation image with intergraded SD can be created from the original. Moreover, the noise frequency component of the created noise addition image is as same as the real image. Thus, the relationship of image quality to SD in the clinical image can be evaluated. Although this method is an easy method of LDSI creation on image data, a noise addition image can be easily created by using image addition and subtraction software and water phantom, and this can be implemented in many facilities.
We present the main points of the optimization in IMRT. The skin surface of the planned target volume was reduced by a few millimeters, in view of the limitations of a calculation grid in accurately estimating the influence of build-up or contamination of electrons. Air cavities such as nasal or oral cavities were, in general, filled with water equivalent density in the dose calculation. Planned target volume was contracted by 5 mm when PTV of a higher prescribed dose was delineated adjacent to it. The 5 mm width of ring-shaped ROI was set at 5 mm outside of the entire PTV to eliminate hot spots. Physical quality assurance is extremely important to eradicate unexpected dose inhomogeneity, and meticulous efforts are required.
The purpose of this study was to determine the exposure conditions for general X-rays by calculation. The concept of the basic equation for the calculation is that the dose after transmitting an object is determined by entering the exposure conditions. For this purpose, we formulated a basic equation by mathematically representing all factors that influence imaging conditions. Using the basic equation, we succeeded in determining the optimal exposure condition for a patient’s body thickness by calculation. Even if another equipment, grid, added filter, etc., is used, optimal exposure conditions can be determined by adding correction factors determined by simple added measurements; this confirmed the versatility of the system. The calculation accuracy was verified to be within 15%. By using this system, we succeeded in optimizing exposure conditions for general X-rays.
A percutaneous transvascular angioplasty (PTA) is performed to relieve failed vascular access for hemodialysis. Angiography using non-ionic iodinated contrast media is the imaging modality of choice for performing PTA. However, the use of iodinated contrast media is contraindicated for patients with a history of iodine allergy. Since 1920, carbon dioxide (CO2) has been used as a safe contrast medium in various studies. In CO2 shunt angiography for hemodialysis, visualization of the vascular structures was often suboptimal due to shunt-specific conditions, such as rapid flow and narrow diameter of the vessels. In the present report, we attempted an improvement of the visualization by injection of CO2 bubbles in view of the properties of CO2 (floating and low viscosity). The results indicated that the CO2 bubbles angiography clearly demonstrated the narrow vessels and stenotic portions that were not visualized by conventional CO2 angiography. In addition, the required volume of CO2 could be reduced in comparison with previous studies in the literature. Therefore, the method seemed to be effective in reducing exposure and preventing complication by CO2. Thus, CO2 bubbles angiography may be useful for shunt angiography and sequential angioplasty when experiencing shunt problems.
In order to evaluate the exposure dose in CT examinations, we measured the tissue and organ doses by test site in 4-row, 16-row, and 64-row multi detector CT by using an anthropomorphic phantom and fluorescent glass dosimeters. Furthermore, we calculated the effective dose by using the tissue weighting factor recommended by the ICRP in 2007. The effective dose in the head and neck examinations was 1.4–3.1 mSv, whereas the maximum skin dose was 278.9 mGy in head perfusion CT. The effective dose in examinations of the body trunk was 10.1–35.2 mSv. In addition, the organ dose and skin dose in the scanning range was similar to the CTDIvol in head and neck examinations, while it was higher than the CTDIvol in examinations of the body trunk. The exposure dose of patients undergoing CT is high in comparison to other radiological examinations. As a result, due to consecutive examinations, an absorbed dose of more than 100 mGy is possible. A future problem therefore remains how to lower the overall exposure dose with the introduction of new radiographic diagnostic modalities, such as phase scan or coronary CT angiography.
The purpose of this study was to clarify actual conditions and problems in medical information education and to propose the educational concept to be adopted in medical information. A questionnaire survey was carried out by the anonymous method in June 2008. The survey was intended for 40 radiological technology schools. The questionnaire items were as follows: (1) educational environment in medical information education, (2) content of a lecture in medical information, (3) problems in medical information education. The response rate was 55.0% (22 schools). Half of the responding schools had a laboratory on medical information. Seventeen schools had a medical information education facility, and out of them, approximately 50% had an educational medical information system. The main problems of the medical information education were as follows: (a) motivation of the students is low, (b) the educational coverage and level for medical information are uncertain, (c) there are not an appropriate textbook and educational guidance. In conclusion, these findings suggest that it is necessary to have a vision of medical information education in the education of radiological technologists.
How the maintenance checks of the medical treatment system, including start of work check and the ending check, was effective for preventive maintenance and the safety improvement was verified. In this research, date on the failure of devices in multiple facilities was collected, and the data of the trouble repair record was analyzed by the technique of reliability engineering. An analysis of data on the system (8 general systems, 6 Angio systems, 11 CT systems, 8 MRI systems, 8 RI systems, and the radiation therapy system 9) used in eight hospitals was performed. The data collection period assumed nine months from April to December 2008. Seven items were analyzed. (1) Mean time between failures (MTBF) (2) Mean time to repair (MTTR) (3) Mean down time (MDT) (4) Number found by check in morning (5) Failure generation time according to modality. The classification of the breakdowns per device, the incidence, and the tendency could be understood by introducing reliability engineering. Analysis, evaluation, and feedback on the failure generation history are useful to keep downtime to a minimum and to ensure safety.