[The Need for Lens Radiation Protection for Healthcare Provider in Open and Internal Fixation of the Hip Joint].

Increased occupational exposure of radiation workers is a major problem during open reduction and internal fixation (ORIF) of the hip joint, as the surgeon's eye lens is in close proximity to the patient and the X-ray tube. The purposes of this study were to clarify the occupational exposure of radiation workers during ORIF of the hip joint and to examine the need for radiation protection measures. The radiation exposure of radiation workers was evaluated by making an airborne dose distribution map using phantom experiments. The radiation goggles attached with a small optically stimulated luminescence dosimeter were used in clinical practice to measure the lens dose received by the surgeon, and the necessity of radiation goggles was examined. The airborne dose distribution in ORIF of the hip joint showed a wider area of high dose rate during axial fluoroscopy of the femoral neck than during posterior-anterior fluoroscopy. In axial fluoroscopy of the femoral neck, the surgeon was always in the high dose rate range of 10 µGy/min or higher, the nurses were in the dose rate range of 4 to 10 µGy/min, and the radiologic technologists were in the dose rate range of 0.5 µGy/min or lower. The maximum 3 mm dose equivalent to the surgeon per case was 0.38 mSv. In contradiction, radiation goggles were useful in ORIF because they provided approximately 60% shielding. It is advisable to work with radiation goggles to avoid cataracts.

PATIENT DOSIMETRY SURVEY OF PEDIATRIC DIAGNOSTIC AND THERAPEUTIC CARDIAC CATHETERISATION IN JAPAN.

To propose reference values for air-kerma at the reference point (Ka,r), air-kerma area product (PKA), fluoroscopy time (FT) and number of cine images (CI) for four age groups in Japan, a nationwide questionnaire was posted to 132 pediatric catheterisation of certified facility in Japan, using the conventional post system, to which 43 facilities responded. For diagnostic cardiac angiography, reference values were as follows: Ka,r: 86, 102, 165 and 264 mGy; PKA: 9.3, 9.5, 16 and 34 Gy.cm2; FT: 33, 29, 26 and 30 min and CI: 1904, 1966, 2405 and 1871 images. For therapeutic cardiac angiography, reference values were as follows: Ka,r: 107, 163, 103 and 202 mGy; PKA: 7.5, 18, 7 and 24 Gy.cm2; FT: 56, 52, 42 and 30 min and CI: 3886, 3232, 2212 and 4316 images for less than 1, 1-5, 6-10 and 11-15 y, respectively. To optimal patient exposure from diagnostic and therapeutic cardiac catheterisation, it is therefore necessary to establish reference values for pediatric cardiac catheterisation examinations for four age groups.

COMPARISON OF THE 64- AND 80-DETECTOR ROW COMPUTED TOMOGRAPHY AMONG THE CT NUMBER AND RADIATION DOSE DURING LOWER EXTREMITY COMPUTED TOMOGRAPHY ANGIOGRAPHY.

To compare the computed tomography (CT) number and the radiation dose between the 64 (group A) and 80-detector row (group B) during lower extremity computed tomography angiography (LE-CTA). We enrolled 144 patients underwent LE-CTA and compared the CT number for the popliteal arteries, radiation dose and the rate of the optimal CT number during the LE-CTA exceeding 200 HU between the two groups. The CT number for the popliteal arteries and mean dose-length product was significantly higher in Group A than in Group B (P < 0.01). The rate of the optimal CT number for the popliteal arteries was 23.6% with Group B scanner and 56.9% with Group A (P < 0.05). The 64-detector row CT was significantly higher in the CT number for the popliteal arteries, radiation dose and rate of the optimal CT number during the LE-CTA than the 80-detector row. Depiction ability did not improve by using a high CT scanner with a wider detector during LE-CTA.

[Measurement of the Lens Dose for Radiological Technologists during Mobile Radiography].

The radiological technologists often assist patients near the X-ray area during mobile radiography. Therefore, it is expected that the lens of eye of radiological technologists is exposed to much radiation. The purposes of this study were to measure the lens dose received by radiological technologists during mobile radiography using radiation protection goggles with a personal dosimeter and a small optically stimulated luminescence dosimeter and discuss the need for radiation protection goggles and additional radiation protection measures. From October 2017 to March 2018, lens doses were measured for eight radiological technologists during mobile radiography using radiation protection goggles with a small optically stimulated luminescence dosimeter and a personal dosimeter. The maximum value of the lens dose received by radiological technologists in mobile radiography was 0.3 mSv per month with a personal dosimeter attached to the neck. The dose-reduction effect of radiation protection glasses during mobile radiography was about 45%. The radiation protection goggles are effective for reducing radiation exposure of lens of eye during mobile radiography. Since there is concern about an increase in lens dose, it is desirable to use the radiation protection goggles for reducing the lens of eye exposure.

[Influence of Calculated Equivalent Doses and Effective Dose due to Differences in Software Version on Radiation Dose Management System].

PURPOSE: To verify the influence of the software version of the dose control system on the equivalent dose and effective dose calculation values. METHODS: We performed chest CT and liver to pelvic CT imaging with a human phantom placed on a CT bed. After the imaging was completed, the radiation dose structured reports (RDSRs) generated by the equipment were transferred to several dose management systems with different software versions for equivalent dose and effective dose calculations. RESULTS: The equivalent and effective doses calculated from the same RDSR differed depending on the software version of the dose management system with a difference of approximately 2 times for the effective dose and up to 50 times for the equivalent dose. CONCLUSION: It is considered that the voxel phantom geometry and dose calculation algorithm may differ depending on the software version of the dose management system. Careful attention should be paid in handling the dose calculation values because the exposure explanations and risk assessments using the equivalent doses, and effective dose calculated by the dose management systems may be overestimated.

[Scientific Research Group Report: Nationwide Survey on Radiation Exposure of Pediatric CT Examination in Japan (2018)].

PURPOSE: To understand the latest pediatric computed tomography (CT) exposure required for the revision of national DRLs. METHODS: A questionnaire was sent to 409 facilities where the members of the Japanese Society of Radiological Technology and the Japanese Society of Pediatric Radiology are enrolled. We investigated the imaging conditions, CTDIvol, and DLP of the pediatric head, chest, and abdominal CT examinations. RESULTS: In all, 43 facilities (11%) responded to our survey. multi detector-row CT (MDCT) systems were available in all surveyed facilities. More than 98% of the MDCT systems had more than 64 detector rows. The CTDIvol of all CT protocols was lower than the NDRL due to the progress of updating to MDCTs with radiation exposure reduction functions such as an iterative reconstruction, but the DLP of head and abdominal CT protocols of some age group were higher than NDRL. CONCLUSION: It is necessary to review the imaging protocol with the attending physician and radiologist and consider further optimization of medical exposure.

[Experiment of a Dedicated Lead Slit for X-ray Output Analyzer in X-ray CT Half-value Layer Measurements].

It is not easy to measure the half-value layer (HVL) of CT because it is necessary to place the X-ray tube position fixed. The aim of this study was to experiment the new methods of HVL measuring of CT using a custom-made lead slit. The custom-made lead slit method allowed the HVL measuring of CT while the rotation of the X-ray tube. The error of HVL value using the custom-made lead slit method compared to the conventional method was within 6%. The custom-made lead slit method can enable to measure the HVL of CT easily without the X-ray tube position fixed.

NATIONWIDE SURVEY OF RADIATION EXPOSURE FOR RADIOFREQUENCY CATHETER ABLATION FOR PULMONARY VEIN ISOLATION AND NONPULMONARY VEIN ISOLATION IN JAPAN.

To propose typical values for the arrhythmia region between pulmonary vein isolation (PVI) and nonpulmonary vein isolation (non-PVI) in Japan. A nationwide questionnaire was posted to 343 facilities, to which 125 facilities (36.4%) responded. Results is the median for PVI and non-PVI were in terms of Ka,r (317 and 196 mGy), PKA (40.8 and 26.3 Gy.cm2), FT (43.0 and 27.3 min), and CI (326 and 102 images). When comparing PVI and non-PVI procedures, there were significant differences in Ka, r, PKA, FT, and CI (p < 0.05). In other words, by classifying into two types, PVI and non-PVI, we contributed to the establishment of typical values in Japan's RFCA.

USE OF VACUUM MATTRESSES CAN REDUCE THE ABSORBED DOSE DURING PEDIATRIC CT.

To evaluate and compare the absorbed dose and image quality when applying a commercially produced fixation device (group A) and a vaccum mattress fixation device to pediatric patients (group B). We compared the absorbed dose and image noise between the groups at the phantom and clinical study. For phantom study, the measurement absorbed dose for a real time skin dosimeter was 3.0 mGy at the group A and 1.9 mGy at the group B (p < 0.05). For clinical study, computed tomography dose index product, dose-length and effective radiation dose were significantly lower with the group B compared to the group A, (3.4 mGy, 27.0 mGy-cm, and 2.2 mSv vs 4.4 mGy, and 36.7 mGy-cm, and 3.0 mSv), p < 0.05 for all comparisons. Compared to the commercially produced fixation device, the vaccum mattress fixation device composed of a less absorptive material enabled a reduction in the absorbed dose while maintaining the image quality during pediatric CT examinations.

[Scatter Radiation Intensities during Transforaminal Lumbar Interbody Fusion Using a Mobile C-arm System].

The purpose of this study was to measure the scatter radiation intensity during transforaminal lumbar interbody fusion using a mobile C-arm system (Arcadis Orbic 3D; Siemens) and minimize radiation exposure. Dosimetry was performed with anterior-posterior and lateral continuous fluoroscopy, and cone beam computed tomography (CT). A scaffold tower (L: 300 cm×W: 200 cm×H: 150 cm) was built with radiation-resistant paper cylinders at intervals of 50 cm and plastic joints over the bed, and 100 optically stimulated luminescence dosimeters (nanoDot; Nagase Landauer) were placed on each joint. A human torso phantom from head to pelvis (Kyoto Kagaku) was positioned on the bed in a prone position. The scatter radiation dose in a lateral view was highest on the X-ray tube side at the height of 100 cm (170.5 µGy/min). The scatter radiation dose increased significantly on the X-ray tube side during lateral continuous fluoroscopy. Continuous change of surgeons' standing positions is important to minimize radiation exposure received by a specific surgeon.

A multicenter study of radiation doses to the eye lenses of medical staff performing non-vascular imaging and interventional radiology procedures in Japan.

PURPOSE: This study aimed to measure the eye lens doses received by physicians and other medical staff participating in non-vascular imaging and interventional radiology procedures in Japan. MATERIAL AND METHODS: From October 2014 to March 2017, 34 physicians and 29 other medical staff engaged in non-vascular imaging and interventional radiology procedures at 18 Japanese medical facilities. These professionals wore radioprotective lead glasses equipped with small, optically stimulated luminescence dosimeters and additional personal dosimeters at the neck during a 1-month monitoring period. The Hp(3) and the Hp(10) and Hp(0.07) were obtained from these devices, respectively. The monthly Hp(3), Hp(10), and Hp(0.07) for each physician and other medical staff member were then rescaled to a 12-month period to enable comparisons with the revised occupational equivalent dose limit for the eye lens. RESULTS: Among physicians, the average annual Hp(3) values measured by the small luminescence dosimeters on radioprotective glasses were 25.5 ± 38.3 mSv/y (range: 0.4-166.8 mSv/y) and 9.3 ± 16.6 mSv/y (range: 0.3-82.4 mSv/y) on the left and right sides, respectively. The corresponding values for other medical staff were 3.7 ± 3.1 mSv/y (range: 0.4-10.4 mSv/y) and 3.2 ± 2.7 mSv/y (range: 0.5-11.5 mSv/y), respectively. CONCLUSIONS: The eye lens doses incurred by physicians and other medical staff who engaged in non-vascular imaging and interventional radiology procedures in Japan were provided. Physicians should wear radioprotective glasses and use additional radioprotective devices to reduce the amount of eye lens doses they receive.

[Reduction of Radiation Exposure to Operator with Radiation Protective Device in ERCP Procedure Using Over-coach X-ray TV System].

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 curtain. In order to reduce the dose received by operators, it is desirable to use protective curtain.

[Nationwide Survey of Medical Radiation Exposure on Cardiovascular Examinations in Japan].

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 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, PKA, 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・cm2, 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.

A more accurate and safer method for the measurement of scattered radiation in X-ray examination rooms.

Advancements in and increasing usage of complex diagnostic examinations with interventional procedures and surgeries has led to an increase in the occupational radiation doses received by physicians and other medical staff. Measuring the scattered radiation doses received by these staff is vital for the development-effective radiation protection programs. In this study, we measured scattered doses during angiography and digital breast tomosynthesis examinations with small-type dosimeters using our jungle gym (JG) method with measurement points at 50-cm intervals. The results were compared with measurements taken using the conventional ion chamber method. The JG method uses paper pipe tubes and a plastic joint structure and allows measurements at different points inside an examination room. The difference between measurements can be attributed to the radiation absorption characteristics of the components used in the JG method. A maximum radiation dose reduction of 20% was observed due to absorption by the JG components. This effect was smaller than the measurement error produced because of reproducibility issues and other limitations of the conventional method. The conventional measurement has disadvantages that are associated with the reproducibility of measurement points, equipment load, and the radiation exposure experienced by the measurer. The proposed JG method exhibits significant improvements in all these aspects. Furthermore, the measurer does not have to be present in the measurement room; therefore, the JG method is extremely safe and useful for radiation protection.

[Evaluation of Radiation Exposure on Mass Screening Examination for Gastric Cancer Using an Air Kerma-area Product Meter].

The present study grasped the radiation exposure per examination by incident air kerma (air kerma-area product; KAP and incident air kerma; Ka, e) using an air kerma-area product meter of our division with mobile population based gastric cancer screening. Initially, we measured the air kerma rate at the patient entrance reference point using an air kerma-area product meter and calibrated dosimeter, for three devices which an air kerma-area product meter was equipped, inspected the indication error of them. The error was 4.3% at the maximum, and accuracy was confirmed. The 816 patients who underwent gastric cancer screening in our division, the median values of KAP and Ka, e of the standard gastrography method 1 were 645.7 mGy·cm2, 37.4 mGy, respectively. The radiation dose of males were significantly higher than females, and the radiation dose increased in proportion to the BMI. The median values of calculated KAP and Ka, e of the standard gastrography method 1 for standard body size were 633.8 mGy·cm2, 37.0 mGy, respectively. We suggest that the patient exposure in gastrography can be optimized using an air kerma-area product meter.

USEFULNESS OF SIZE-SPECIFIC DOSE ESTIMATES IN PEDIATRIC COMPUTED TOMOGRAPHY: REVALIDATION OF LARGE-SCALE PEDIATRIC CT DOSE SURVEY DATA IN JAPAN.

The objective of this research is to calculate the organ equivalent dose and effective dose from the scanning conditions at 165 centers in Japan using computed tomography (CT) Dose software and compare the results with the CT dose index volume (CTDIvol), dose length product (DLP) and size-specific dose estimates (SSDE) to validate the usefulness of SSDE. The CTDIvol and DLP were significantly lower in infants than in children (p < 0.05). No significant differences were found in the bone marrow equivalent dose and effective dose for the torso between infants and children (p > 0.05), and the bone marrow equivalent dose and effective dose for the head were higher in infants than children (p < 0.05). No significant difference was found in SSDE for the torso between infants and children (p > 0.05). Organ equivalent and effective doses for head CT scans are higher in infants than in children (I/P ratio ≥ 1). The I/P ratios of CTDIvol and DLP for chest and abdominal CT scans are also higher in Japan than in other countries. CTDIvol and DLP are not accurate when used as a dose index, and SSDE was considered suitable for dose assessment of the torso. However, for head CT in infants, a further reduction in radiation exposure is required.

Nationwide survey of radiation exposure during pediatric computed tomography examinations and proposal of age-based diagnostic reference levels for Japan.

BACKGROUND: Diagnostic reference levels (DRLs) have not been established in Japan. OBJECTIVE: To propose DRLs for CT of the head, chest and abdomen for three pediatric age groups. MATERIALS AND METHODS: We sent a nationwide questionnaire by post to 339 facilities. Questions focused on pediatric CT technology, exposure parameters, CT protocols, and radiation doses for age groups <1 year, 1-5 years, and 6-10 years. RESULTS: For the three age groups in the 196 facilities that responded, the 75th percentile values of volume CT dose index based on a 16-cm phantom (CTDIvol 16 [mGy]) for head, chest and abdominal CT were for infants 39.1, 11.1 and 12.0, respectively; for 1-to 5-year-olds 46.9, 14.3 and 16.7, respectively; and for 6-to 10-year-olds 67.7, 15.0 and 17.0, respectively. The corresponding dose­length products (DLP 16 [mGy・cm]) for head, chest and abdominal CT were for infants 526.1, 209.1 and 261.5, respectively; for 1-to 5-year-olds 665.5, 296.0 and 430.8, respectively; and for 6-to 10-year-olds 847.9, 413.0 and 532.2, respectively. CONCLUSION: The majority of CTDIvol 16 and DLP 16 values for the head were higher than DRLs reported from other countries. For risk reduction, it is necessary to establish DRLs for pediatric CT in Japan.