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Purpose: To verify the effectiveness of optimizing the number of mask images in DSA for radiation dose reduction during cerebral angiography., Methods: A total of 60 angiography sessions in 2 times for 30 patients performed by the same operator were included in this study. In order to compare the effects of optimization to change the injection delay time of DSA from 1 s to the shortest possible time, the number of mask images, the number of imaging frames, and radiation doses between sessions were compared and analyzed retrospectively., Results: In one DSA run, the number of mask images was decreased from 6 (5-7) to 3 (2-3) frames (p<0.01)/57.1% (median [IQR]/reduction rate), the number of imaging frames was decreased from 34 (32-36) to 32 (29-34) frames (p<0.01)/7.9%, and the radiation dose was decreased from 33 (23-47) to 30 (21-40) mGy (p<0.01)/8.3%. In magnification angiography, the reductions rate was significantly increased. In one angiography session, the number of mask images was decreased from 45 (35-72) to 19 (16-34) frames (p<0.01)/54.6%, the number of imaging frames was decreased from 242 (199-385) to 211 (181-346) frames (p<0.01)/8.3%, the radiation dose of DSA was decreased from 295 (190-341) to 242 (167-305) mGy (p<0.01)/11.6%, and the total radiation dose was decreased from 369 (259-418) to 328 (248-394) mGy (p<0.01)/7.5%., Conclusion: Using the shortest possible injection delay time for the number of mask image optimization was an effective radiation dose reduction method.

Purpose: The objective of this study was to compare the temperature dependence of a scintillation survey meter with and without the temperature compensation function. Investigation of temperature dependence is important to make precise measurements in various environments., Method: The experiment was conducted using the NaI (Tl) scintillation survey meter with the temperature compensation function (TCS-1172) and the NaI (Tl) and CsI (Tl) scintillation survey meters without the temperature compensation function (TCS-171, PDR-111). In all, 1 cm dose equivalent rate (µSv/h) was measured by changing the room temperature from 10 to 40 degree Celsius., Result: The results showed that the scintillation survey meter with the temperature compensation function had almost no change in the measured values with changes in room temperature, whereas the 1 cm dose equivalent rate of the scintillation survey meter without the temperature compensation function changed by a maximum of -7.2 (%/10°C) as temperature increased., Conclusion: This study confirms that the scintillation survey meter with the temperature compensation function was less dependent on temperature, and stable measurement was possible. However, it was suggested that the scintillation survey meter without the temperature compensation function might cause a drop in the measured value as the temperature rises.

Purpose: Skin injury in patients due to radiation exposure has been a complication in percutaneous coronary intervention (PCI) for a long time. To the best of our knowledge, there have been no reports comparing radiation dose by treatment area with diagnostic reference levels (DRLs) 2020, although the radiation dose varies by treatment area in PCI., Methods: In this study, the treatment areas were classified into four segments (i.e., AHA #1-3, AHA #4, AHA #5-10, and AHA #11-15), and each segment was compared with DRLs 2020. This retrospective study included 984 consecutive patients with single-vessel disease and non-chronic total occlusion. PCI was performed on a single device., Results: The median radiation dose was 1640.8 mGy, and the radiation dose for AHA #4 was 2732.0 mGy, which was significantly higher than the other treatment areas (p<0.001). In AHA #4, the radiation dose increased due to the heavy use of the left cranial view, and the patient background contributed to the increased lesion complexity. Therefore, it was challenging to evaluate AHA #4 and the other treatment areas with a uniform DRL value., Conclusion: Establishing a subdivided index for each treatment area is crucial if DRLs are used as a reference during procedures and as a guide for dose optimization.

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.

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 hand, the maximum Hp (3) of the EP-IR physician was estimated 29 mSv without the radiation protective glasses and 15 mSv with the radiation protective glasses., Conclusion: Physicians eye lens dose [Hp (3) ] tended to be overestimated by the neck badge measurements [Hp (0.07)]. A correct evaluation of the lens dose [Hp (3) ] using the direct eye dosimeter is recommended. Although we found a positive correlation between Hp (0.07) and Hp (3), the value of R 2 in the regression equation is low, we recommended that the eye lens dose estimated carefully from Hp (0.07).

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 (P KA ). 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 cases of the percutaneous coronary intervention (PCI), 962 cases of the radiofrequency catheter ablation (RFCA) and 377 cases of pediatric CVI. The 75th percentile value of Ka,r, P KA , fluoroscopy time (FT) and number of cine images (CI) for CAG, PCI, RFCA and pediatric CVI were 702, 2042, 644, and 159 mGy, respectively, 59.3, 152, 81.3, and 14.9 Gy・cm 2 , respectively, 10.2, 35.6, 61.1, and 35.6 min, respectively and 1503, 2672, 722, and 2378 images, respectively. Our investigation showed that the angiographic parameters were different in several CVI procedures., Conclusions: The displayed dosimetric parameters on the angiographic machine in CVI procedures showed different values. We should classify the dosimetric parameters for each procedure.

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.

Deterministic effects have been reported in cardiac interventional procedures. To prevent radiation skin injuries in percutaneous coronary intervention (PCI), it is necessary to measure accurate patient entrance skin dose (ESD) and maximum skin absorbed dose (MSD). We measured the MSD on 62 patients in four facilities by using the Chest-RADIREC(Ⓡ) system. The correlation between MSD and fluoroscopic time, dose area product (DAP), and cumulative air kerma (AK) showed good results, with the correlation between MSD and AK being the strongest. The regression lines using MSD as an outcome value (y) and AK as predictor variables (x) was y=1.18x (R(2)=0.787). From the linear regression equation, MSD is estimated to be about 1.18 times that of AK in real time. The Japan diagnostic reference levels (DRLs) 2015 for IVR was established by the use of dose rates using acrylic plates (20- cm thick) at the interventional reference point. Preliminary reference levels proposed by International Atomic Energy Agency (IAEA) were provided using DAP. In this study, AK showed good correlation most of all. Hence we think that Japanese DRLs for IVR should reconsider by clinical patients' exposure dose such as AK.

Although measurement and management of angiographic entrance skin dose (ESD) are deemed extremely important, accurate determination of maximum ESD and its location is generally difficult because of the dependence on therapeutic technique and position. Following our development of body-mounted gear bearing radiophotoluminescence glass dosimeter (RPLD) arrays for direct measurement of ESD in cranial and cardiovascular angiography and interventional radiology (IVR), our focus next turned to the limited number of facilities equipped to read RPLD outputs and the need for methods to effectively provide feedback to clinical facilities. As described here, we first constructed an RPLD reading facility capable of sending and receiving RPLDs by post, offering the potential to enable utilization of the developed gear at all hospitals in Japan that perform angiography and IVR. We next developed specialized web-based system to generate dose maps from RPLD dose data, thereby enabling any facility to perform trial system analysis, evaluation, and implementation; and investigated the results and related problems.

Using radio-photoluminescence glass dosimeter, we measured the entrance skin dose (ESD) in 46 cases and analyzed the correlations between maximum ESD and angiographic parameters [total fluoroscopic time (TFT); number of digital subtraction angiography (DSA) frames, air kerma at the interventional reference point (AK), and dose-area product (DAP)] to estimate the maximum ESD in real time. Mean (± standard deviation) maximum ESD, dose of the right lens, and dose of the left lens were 431.2 ± 135.8 mGy, 33.6 ± 15.5 mGy, and 58.5 ± 35.0 mGy, respectively. Correlation coefficients (r) between maximum ESD and TFT, number of DSA frames, AK, and DAP were r=0.379 (P<0.01), r=0.702 (P<0.001), r=0.825 (P<0.001), and r=0.709 (P<0.001), respectively. AK was identified as the most useful parameter for real-time prediction of maximum ESD. This study should contribute to the development of new diagnostic reference levels in our country.

In recent years, dose justification and optimization have been attempted in percutaneous coronary intervention (PCI); however, deterministic effects have been reported. To prevent radiation skin injuries in PCI, it is necessary to measure the patient entrance skin dose (ESD), but an accurate dose measurement method has not yet been established. In this study, we developed a dosimetry gown that can measure the ESD during PCI using multiple radiophotoluminescence dosimeters (RPLDs). The RPLDs were placed into 84 pockets that were sewn into a dosimetry gown. Patients wear the original dosimetry gown during the procedures, after which we obtain accurate ESD measurements. We believe that this method using RPLDs and a newly-designed dosimetry gown provides accurate ESD measurements during PCI. We expect this system to become a standard method for measuring ESD during PCI.

The Fukushima nuclear disaster occurred on March 11, 2011. For about six weeks, I worked as a counselor for phone consultations regarding radiation risk. I analyzed the number of consultations, consultations by telephone, and their changing patterns with elapse of time, to assist with consultations about risk in the future. There were a large number of questions regarding the effects of radiation, particularly with regard to children. We believe that counseling and risk communication are the key to effectively informing the public about radiation risks.

Radiation safety education/training is essential and is associated with a reduction in the radiation dose to both patients and staff. We used a questionnaire to assess the level of radiation safety knowledge among nurses working at Tohoku Kosei-Nenkin Hospital. Some nurses were also interviewed. The results of our study indicate that the nurses had insufficient radiation safety knowledge and that a high percentage of nurses were concerned about the health hazards of radiation. Moreover, more than 80% of the nurses expressed an interest in attending periodic radiation safety seminars. Appropriate radiation safety training is required to reduce nurse radiation doses, and an understanding of radiation safety can help to optimize the patient dose.

Angiographic equipment has tended toward using flat-panel detector (FPD). However, the radiation dose varies depending on the size of field of view (FOV) in the FPD. Although we were using 7 inch FOV in cardiac procedures, we examined a way to reduce the patients' radiation dose by using 8 inch FOV utilizing a digital zoom processing. We measured the absorbed dose rates at an interventional reference point (IRP) with 20 cm acrylic board to compare 8 inch FOV using a digital zoom processing with 7 inch FOV. Additionally we visually evaluated these phantom images. Result of comparison of absorbed dose rates at IRP, 8 inch FOV using a digital zoom processing was reduced more than 7 inch FOV (fluoroscopic 29.0% and digital cine 37.5%). These phantom images were of equivalent quality. The method to use 8 inch FOV utilizing a digital zoom processing technique in cardiac procedures is one of the effective radiation exposure reduction methods.

The use of an adaptive filter for CT images is becoming a common procedure and is said to reduce image noise while preserving sharpness and helping to reduce the required X-ray dose. Although many reports support this view, the validity of such evaluations is arguable. When the linearity of a system is in question, physical performance indexes should be measured under conditions similar to those of clinical use. Evaluations of diagnosis using clinical images may be fallible because the non-filtered image used as the reference might not have been optimally reconstructed. We have chosen simple, but commonly used, adaptive filters for our evaluation. As a reference for comparing performance, we designed linear filters that best approximate the noise characteristics of the adaptive filters. MTF is measured through observation of the edge-spread function. Clinical abdominal images are used to compare the performance of adaptive filters and linear filters. We conclude that the performance of the type of adaptive filter we have chosen is virtually the same as that of the linear filter, as long as the image quality of soft tissues is our interest. Both the noise SD and MTF are virtually the same if the contrast of the object is not substantially higher than 150 HU. Images of soft tissues obtained with the use of adaptive filters are also virtually the same as those obtained by linear filters. The edge-preservation characteristic of this adaptive filter is not observable for soft tissues.

Since cardiac interventional procedures deliver high doses of radiation to the physician, radiation protection for the physician in cardiac catheterization laboratories is very important. One of the most important means of protecting the physician from scatter radiation is to use additional lead shielding devices, such as tableside lead drapes and ceiling-mounted lead acrylic protection. During cardiac interventional procedures (cardiac IVR), however, it is not clear how much lead shielding reduces the physician dose. This study compared the physician dose [effective dose equivalent (EDE) and dose equivalent (DE)] with and without additional shielding during cardiac IVR. Fluoroscopy scatter radiation was measured using a human phantom, with an ionization chamber survey meter, with and without additional shielding. With the additional shielding, fluoroscopy scatter radiation measured with the human phantom was reduced by up to 98%, as compared with that without. The mean EDE (whole body, mean+/-SD) dose to the operator, determined using a Luxel badge, was 2.55+/-1.65 and 4.65+/-1.21 mSv/year with and without the additional shielding, respectively (p=0.086). Similarly, the mean DE (lens of the eye) to the operator was 15.0+/-9.3 and 25.73+/-5.28 mSv/year, respectively (p=0.092). In conclusion, although tableside drapes and lead acrylic shields suspended from the ceiling provided extra protection to the physician during cardiac IVR, the reduction in the estimated physician dose (EDE and DE) during cardiac catheterization with additional shielding was lower than we expected. Therefore, there is a need to develop more ergonomically useful protection devices for cardiac IVR.