The purpose of this study was to investigate the effect of the position in XYZ directions and acquisition parameters on the basic image qualities of for cone beam computed tomography (CBCT) in an angiography system with flat panel detector. The resolution property (modulation transfer function: MTF) and the noise property (Wiener spectrum: WS) of CBCT images in X-Y plane were measured with different acquisition parameters (scan matrix number and projection number) and the effect of the position in XYZ directions. The MTFs with 1024×1024 matrix were higher than those of 512×512 matrix and decreased in the peripheral areas due to the reduction of projection number. The highest and the lowest MTFs were measured at the X-ray tube side and on the detector side of the position in X-Y plane, respectively. The WS-doubled projection number showed about 50% lesser noise level. There were differences in the Wiener spectra (WS) at the position in XYZ directions. We conclude that the resolution and the noise property of CBCT image in X-Y plane showed dependences on the position in XYZ directions and acquisition parameters of the CBCT.
Dose volume histogram (DVH) is one of the methods for evaluating the feasibility of radiotherapy plans. It is difficult to thoroughly comprehend an evaluation of each plan at a glance and to give a concise presentation of the case at conference. In this study, we provide a useful program that will fulfill such a purpose on a clinical setting. We have revised our protocols of radiotherapy planning, developed the program using Visual Basic 2010, which could facilitate an evaluation of DVH, and used it for checking plans and presentation at case conference. Since our DVH analysis program shows a result of DVH in a simple way, such as “OK (Okay)” or “NG (No good)”, we can promptly comprehend the results of each radiotherapy plan at ease. This program easily tells us accordance between plans and protocols. We found this program useful and worth spreading.
In magnetic resonance imaging (MRI) examination of the patients with the cochlear implant, only limited data have a mention for safety information in the instruction manual supplied by the manufacturers. Therefore, imaging operators require more detailed safety information for implant device. We conducted detailed examination about displacement force, torque, and demagnetizing of the cochlear implant magnet based on American Society for Testing and Materials (ASTM) standard using the PULSAR and CONCERTO (MED-EL) with 1.5 tesla MRI system. As a result, the displacement force and the torque of the implant magnet were less than the numerical values descried in the manual. Therefore, these have almost no effect on the body under the condition described in a manual. In addition, the demagnetizing factor of the cochlear implant magnet occurred by a change magnetic field. The demagnetization depended on the direction of a line of magnetic force of the static magnetic field and the implant magnet. In conclusion, the operator must warn the position of the patients on inducing in the magnet room.
The American College of Radiology recommends dividing magnetic resonance imaging (MRI) machine rooms into four zones depending on the education level. However, structural limitations restrict us to apply such recommendation in most of the Japanese facilities. This study examines the effectiveness of the usage of a belt partition to create the zonal division by a questionnaire survey including three critical parameters. They are, the influence of individuals’ background (relevance to MRI, years of experience, individuals’ post, occupation [i.e., nurse or nursing assistant], outpatient section or ward), the presence or absence of a door or belt partition (opening or closing), and any four personnel scenarios that may be encountered during a visit to an MRI site (e.g., from visiting the MRI site to receive a patient) . In this survey, the influence of dangerous action is uncertain on individuals’ backgrounds (maximum odds ratio: 6.3, 95% CI: 1.47–27.31) and the scenarios of personnel (maximum risk ratio: 2.4, 95% CI: 1.16–4.85). Conversely, the presence of the door and belt partition influences significantly (maximum risk ratio: 17.4, 95% CI: 7.94–17.38). For that reason, we suggest that visual impression has a strong influence on an individuals’ actions. Even if structural limitations are present, zonal division by belt partition will provide a visual deterrent. Then, the partitioned zone will serve as a buffer zone. We conclude that if the belt partition is used properly, it is an inexpensive and effective safety management device for MRI rooms.
Japan Network for Research and Information on Medical Exposures (J-RIME) released the primary diagnostic reference levels (DRLs 2015) to optimize/manage the radiation dose for interventional radiology (IVR) on June 7, 2015 in Japan. However, this DRLs 2015 has a wide range of selection bias for only certified IVR technologists’ dates. Therefore, it is important to know the radiation dose including non-certified IVR technologists’ facilities. In this study, we verified the fluoroscopy radiation dose rates for many IVR systems in the present situation. This study was conducted at 13 cardiac catheterization laboratories (18 X-ray systems) around Sendai. We measured the entrance doses at the patient entrance reference point (interventional reference point) using a 20-cm-thick acrylic plate and skin-dose monitor. Although the DRLs 2015 of IVR is 20 mGy/min, the result of a fluoroscopy radiation dose in 18 X-ray systems was median (inter quartile range: IQR), 24.4 (16.3, 35.5) mGy/min. The optimization/managing the radiation dose of IVR X-ray systems is an important issue. In addition, it is necessary to intensify the activities to raise awareness for DRLs 2015.