The 10 most-cited articles in Japanese Journal of Radiological Technology, 2020

The aims of this study were to elucidate signal pattern of cerebral aneurysm clip in brain magnetic resonance angiography (MRA) using non-contrast enhanced ultra-short echo time (UTE) sequence and to explore effective utilization of this novel technique for patients, who underwent cerebral aneurysm clipping. The clip was embedded in homemade phantom and scanned using UTE sequence. We investigated characteristic features of the artifacts derived from the clip. Besides, we compared the volume of signal loss between conventional time-of-flight (TOF) and UTE-MRA in 50 patients with the cerebral aneurysm clip. In phantom study, the clip was delineated as signal void area fully surrounded by high signal on original images. On reconstructed short-axial views for the clip, four-leaf clover pattern of artifact was observed when clip was arranged orthogonal to the static magnetic field. On the other hand, this artifact disappeared when the clip was arranged in parallel with the static magnetic field. The volume of signal loss in clinical cases was significantly reduced in UTE-MRA (P < 0.05):…

Purpose: X-ray pelvimetry is typically performed for the diagnosis of the cephalopelvic disproportion (CPD). The purpose of this study was to assess the utility of new computed tomography (CT) reconstruction “deep learning based reconstruction (DLR) ” in ultra-low dose CT pelvimetry. Method: CT pelvimetry was performed 320-row CT. All CT images were reconstructed with and without DLR and transferred for workstation to processing martius and guthmann view. Radiologist and obstetrician-gynecologist subjectively ranked overall image quality of each CT image from the best to the worst. Exposure dose of the CT pelvimetry used a following calculated value, displayed CT dose index (CTDI) vol multiplied by measured value using the thimble chamber and pelvic phantom, and of the X-ray pelvimetry used Japan-Diagnositic Refernce Levels 2015 as a reference, were compared. Result: 3D images obtained from CT pelvimetry with DLR showed accurate biparietal diameter and obstetric conjugate as compared to without DLR. Radiation dose of CT pelvimetry is 0.39 mGy, of X-ray pelvimetry is 1.18 mGy,…

Purpose: It is very important to manage the radiation dose of cardiovascular interventional (CVI) procedures. Overseas, the diagnostic reference levels for cardiac interventional procedures were established with the air kerma at the patient entrance reference point (Ka,r) and the air kerma-area product (PKA). Although the Japan DRLs 2015 was established by the Japan Network for Research and Information on Medical Exposure (J-RIME), the Japan DRL for CVIs were established by fluoroscopic dose rates of 20 mGy/min at the patient entrance reference point with 20 cm thickness polymethyl methacrylate (PMMA) phantom. In the present our study, we performed a questionnaire survey of indicated values of angiographic parameters in CVI procedures. Methods: A nationwide questionnaire was sent by post to 765 facilities. Question focused on angiographic technology, exposure parameters and radiation doses as the displayed dosimetric parameters on the angiographic machine. Results: The recovery rate was 22.8% at 175 out of 765 facilities. In total 1728 cases of the coronary angiography (CAG), 1703…

PURPOSE: Organ-based tube current modulation (OB-TCM) techniques, which are provided by three vendors, reduces the radiation dose to the lens of the eyes by decreasing the tube current, when the X-ray tube passes over the anterior surface of critical organs. However, the characteristics of dose modulation of these techniques are different. The purpose of this study was to understand the performance characteristics of OB-TCM technique of each computed tomography (CT) vendor at head CT. METHODS: We used three CT scanners (SOMATOM Definition Flash; Siemens Healthcare, Revolution CT; GE Healthcare, and Aquilion ONE Genesis Edition; Canon Medical Systems). We measured the radiation dose to the lens surface as evaluation of radiation dose reduction and measured the image noise as index of image quality. We measured the radiation dose rate in the air for analysis of the characteristics of dose modulation in each OB-TCM. RESULTS: When applying OB-TCM, the radiation doses for the lens surface were decreased by 28%, 22%, and 25% for Siemens, GE, and Canon CT scanners, respectively, and the…

Purpose : This study investigated the dosimetric characteristics of electron beams shaped with a real-time shapeable tungsten-containing rubber (STR) collimator. Methods : Circular irradiation fields of 40 mm diameter were shaped using STR or low melting-point alloy (LMA) placed on the electron applicator. The STR heated with approximately 70-degree warm water was molded into the template bottom of the applicator. Percent depth doses (PDDs) and lateral dose profiles of 6 and 12 MeV electron beams were measured and compared between STR and LMA. For the PDDs, the depths of maximum dose (dmax), 90% dose (d90), and 80% dose (d80) were evaluated. For the lateral dose profiles, penumbra as the width of the off-axis distance from 80% to 20% doses and treatment diameter covering over 90% dose were evaluated at the surface, dmax, d90, and d80. The transmission of the STR was also investigated at thicknesses fit to electron applicator for 6 and 12 MeV electron beams. Results : The STR was softened with 70-degree warm water. Therefore, it was easy to mold it and attach the applicator. The PDDs…

Purpose: The aperture shape controller (ASC) decreases the complexity of the multi-leaf collimator (MLC) aperture for volumetric modulated arc therapy (VMAT). The purpose of this study was to evaluate the effect of ASC settings on the VMAT plan quality. Method: First, VMAT plans were created (ASC=off) for three test patterns of The American Association of Physicists in Medicine (AAPM) Task Group 119 (TG-119) and 20 cases of nasopharyngeal cancer. Next, for these VMAT plans, only the ASC settings were changed from very low (complexity reduction: low) to very high (complexity reduction: high) in five steps, and VMAT plans were created respectively. To evaluate the created VMAT plans per each ASC settings, we analyzed the modulation complexity score (MCSV) and dosimetric parameters for the planning target volume (PTV) and organ at risk (OAR). Result: In three test patterns, there were no major dosimetric differences between the VMAT plans. In nasopharyngeal cancer, the mean MCSV were 0.413, 0.325, 0.320, 0.307, 0.303, and 0.272 for very high, high, moderate, low, very low, off…

PURPOSE: To compare the contrast enhancement between bolus-tracking (BT) and test-bolus (TB) methods in coronary computed tomography angiography (CCTA). METHOD: We enrolled 300 patients who underwent CCTA by BT (245 mg I/kg main bolus) or TB (77.4 mg I/kg test bolus with 245 mg I/kg main bolus) methods. In group BT (n=150), scanning was started automatically 5-second after contrast enhancement exceeded a predefined threshold of 150 Hounsfield units (HU). In group TB (n=150), TB peak attenuation plus 2-second was used as a delay. We recorded the CT number in the ascending aorta and determined whether the CT number was equivalent in two groups. For the equivalence test, we adopted 70 HU as the equivalence margin. The standard deviation (SD) in the CT number and the rate of patients with an acceptable CT number were compared. We also compared total iodine dose and total dose length product (DLP). RESULT: The CT number of the ascending aorta was 437.6±68.9 HU in group BT and 438.9±69.7 HU in group TB; the 95% confidence interval for the difference between the groups was from -11.6 to…

It is important to reduce the dose received by medical staffs. The purpose of this study was to evaluate the effect of protective curtain and the property of small optically stimulated luminescence (OSL) dosimeters used for ambient dose measurement in fluoroscopy. The property of small OSL dosimeters was investigated in terms of uniformity, changing fluoroscopy time and polymethyl methacrylate (PMMA) thickness, and angular dependence. Paper pipes were assembled in glid shape and ambient dose was investigated by using small OSL dosimeters that were put on them with and without protective curtain. Air kerma was investigated by small OSL dosimeters that were put on a head phantom at the position of eyes. Dose response of small OSL dosimeters was independent of fluoroscopy time and PMMA thickness, so it is appropriate to measure ambient dose by small OSL dosimeters. In relation to ambient dose, there was significant difference with and without protective curtain (p<0.001, paired-t-test). These air kerma on the head phantom were reduced to approximately 20% by attaching protective…

Purpose: The International Commission on Radiological Protection recommended that interventional radiologies (IRs) have high radiation doses and that staff may also be exposed to high doses. In the present study, we measured the radiation exposure dose [3 mm dose equivalent, Hp (3) ] in the eye using an appropriate dosimeter placed next to the physician’ s eye during neurovascular intervention procedure (Neuro-IR) and interventional cardiac electrophysiology procedure (EP-IR). Method: Physicians wore a direct eye dosemeter just lateral to the left eye and an additional direct eye dosemeter outside the radiation protective glasses close to their left eye. Additionally, a neck badge [0.07 mm dose equivalent, Hp (0.07) ] was worn outside the protective apron to the left of the neck, to compare the direct eye dosimeter estimated doses. The occupational eye lens dose was evaluated over a period of 6-month. Results: The maximum Hp (3) of the Neuro-IR physician was estimated 5.1 mSv without the radiation protective glasses and 1.6 mSv with the radiation protective glasses. On the other…