Current situations and discussions in Japan in relation to the new occupational equivalent dose limit for the lens of the eye.

Since the International Commission on Radiological Protection recommended reducing the occupational equivalent dose limit for the lens of the eye in 2011, there have been extensive discussions in various countries. This paper reviews the current situation in radiation protection of the ocular lens and the discussions on the potential impact of the new lens dose limit in Japan. Topics include historical changes to the lens dose limit, the current situation with occupational lens exposures (e.g., in medical workers, nuclear workers, and Fukushima nuclear power plant workers) and measurements, and the current status of biological studies and epidemiological studies on radiation cataracts. Our focus is on the situation in Japan, but we believe such information sharing will be useful in many other countries.

Application of a Flexible PET Scanner Combined with 3 T MRI Using Non-local Means Reconstruction: Qualitative and Quantitative Comparison with Whole-Body PET/CT.

PURPOSE: Flexible positron emission tomography (fxPET) employing a non-local means reconstruction algorithm was designed to fit existing magnetic resonance imaging (MRI) systems. We aimed to compare the qualitative and quantitative performance of fxPET among fxPET with MR-based attenuation correction (MRAC), fxPET with CT-based attenuation correction (CTAC) using CT as a part of WB PET/CT, and whole-body (WB) PET/CT. PROCEDURES: Sixteen patients with suspected head and neck cancer underwent 2-deoxy-2-[18F]fluoro-D-glucose WB PET/CT scans, followed by fxPET and 3 T MRI scans. Phantom data were compared among the three datasets. For registration accuracy, we measured the distance between the center of the tumor determined by fxPET and that in MRI. We compared image quality, detection rates, and quantitative values including maximal standardized uptake value (SUVmax), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and tumor-to-muscle ratio (TMR) among the three datasets. RESULTS: The phantom data in fxPET, except the percent contrast recoveries of 17-mm and 22-mm hot spheres, were inferior to those in WB PET/CT. The mean registration accuracy was 4.4 mm between fxPET using MRAC and MRI. The image quality was comparable between two fxPET datasets, but significantly inferior to WB PET/CT (p < 0.0001). In contrast, detection rates were comparable among the three datasets. SUVmax was significantly higher, and MTV and TLG were significantly lower in the two fxPET datasets compared with the WB PET/CT dataset (p < 0.005). There were no significant differences in SUVmax, MTV, and TLG between the two fxPET datasets or in TMR among the three datasets. All quantitative values had significantly positive correlations. CONCLUSIONS: Compared with WB PET/CT, the phantom data and image quality were inferior in fxPET. However, the results of the detection rates and quantitative values suggested the clinical feasibility of fxPET.

Fusion of MRI and sonography image for breast cancer evaluation using real-time virtual sonography with magnetic navigation: first experience.

OBJECTIVE: We recently developed a real-time virtual sonography (RVS) system that enables simultaneous display of both sonography and magnetic resonance imaging (MRI) cutaway images of the same site in real time. The aim of this study was to evaluate the role of RVS in the management of enhancing lesions visualized with MRI. METHODS: Between June 2006 and April 2007, 65 patients underwent MRI for staging of known breast cancer at our hospital. All patients were examined using mammography, sonography, MRI and RVS before surgical resection. Results were correlated with histopathologic findings. MRI was obtained on a 1.5 T imager, with the patient in the supine position using a flexible body surface coil. Detection rate was determined for index tumors and incidental enhancing lesions (IELs), with or without RVS. RESULTS: Overall sensitivity for detecting index tumors was 85% (55/65) for mammography, 91% (59/65) for sonography, 97% (63/65) for MRI and 98% (64/65) for RVS. Notably, in one instance in which the cancer was not seen on MRI, RVS detected it with the supplementation of sonography. IELs were found in 26% (17/65) of the patients. Of 23 IELs that were detected by MRI, 30% (7/23) of IELs could be identified on repeated sonography alone, but 83% (19/23) of them were identified using the RVS system (P = 0.001). The RVS system was able to correctly project enhanced MRI information onto a body surface, as we checked sonography form images. CONCLUSIONS: Our results suggest that the RVS system can identify enhancing breast lesions with excellent accuracy.

[Report in 2017 April ～ 2018 March].

Women physicians, scientists and nurses are addressing many problems encountered in the practice of their chosen fields. We carried out a survey of the women working in the nuclear medicine field. Two hundred and six professionals answered this questionnaire. The findings of our survey were that we have many female bosses (experts), a low number of sexual harassment issues and enough parental leave. Many members work very hard to practice in this field, but they do not have enough support from their hospitals or research centers, to join medical conferences. And almost a quarter of those surveyed thought it is hard to improve their careers after taking parental leave. A change of perception in how their male colleagues and counterparts regard women in the field of nuclear medicine is required. This change, along with women having a clear and realistic career plan are fundamental answers to the issues faced by women in nuclear medicine.

Report of a nationwide survey on actual administered radioactivities of radiopharmaceuticals for diagnostic reference levels in Japan.

OBJECTIVE: The optimization of medical exposure is one of the major issues regarding radiation protection in the world, and The International Committee of Radiological Protection and the International Atomic Energy Agency recommend establishing diagnostic reference levels (DRLs) as tools for dose optimization. Therefore, the development of DRLs based on the latest survey has been required for nuclear medicine-related societies and organizations. This prompted us to conduct a nationwide survey on the actual administered radioactivity to adults for the purpose of developing DRLs in nuclear medicine. METHODS: A nationwide survey was conducted from November 25, 2014 to January 16, 2015. The questionnaire was sent to all of the 1249 nuclear medicine facilities in Japan, and the responses were collected on a website using an answered form. RESULTS: Responses were obtained from 516 facilities, for a response rate of 41 %. 75th percentile of (99m)Tc-MDP and (99m)Tc-HMDP: bone scintigraphy, (99m)Tc-HM-PAO, (99m)Tc-ECD and (123)I-IMP: cerebral blood flow scintigraphy, (99m)Tc-Tetrofosmin, (99m)Tc-MIBI and (201)Tl-Cl; myocardial perfusion scintigraphy and (18)F-FDG: oncology PET (in-house-produced or delivery) in representative diagnostic nuclear medicine scans were 932, 937, 763, 775, 200, 831, 818, 180, 235 and 252, respectively. More than 90 % of the facilities were within the range of 50 % from the median of these survey results in representative diagnostic nuclear medicine facilities in Japan. Responses of the administered radioactivities recommended by the package insert, texts and guidelines such as 740 MBq ((99m)Tc-MDP and (99m)Tc-HMDP: bone scintigraphy), 740 MBq ((99m)Tc-ECD and (99m)Tc-HM-PAO: cerebral blood flow scintigraphy) and 740 MBq ((99m)Tc-Tetrofosmin and (99m)Tc-MIBI: myocardial perfusion scintigraphy), etc. were numerous. The administered activity of many radiopharmaceuticals of bone scintigraphy ((99m)Tc-MDP and (99m)Tc-HMDP), cerebral blood flow scintigraphy ((99m)Tc-HM-PAO) and myocardial perfusion scintigraphy ((99m)Tc-Tetrofosmin and (99m)Tc-MIBI), etc. were within the range of the EU DRLs and almost none of the administered radioactivity in Japan exceeded the upper limit of SNMMI standard administered radioactivity. CONCLUSIONS: This survey indicated that the administered radioactivity in diagnostic nuclear medicine in Japan had been in the convergence zone and nuclear medicine facilities in Japan show a strong tendency to adhere to the texts and guidelines. Furthermore, the administered radioactivities in Japan were within the range of variation of the EU and the SNMMI administered radioactivities.

The essence of the Japan Radiological Society/Japanese College of Radiology Imaging Guideline.

Diagnostic imaging is undoubtedly important in modern medicine, and final clinical decisions are often made based on it. Fortunately, Japan has the highest numbers of diagnostic imaging instruments, such as CT and MRI devices, and boasts easy access to them as well as a high level of diagnostic accuracy. In consequence, a very large number of imaging examinations are performed, but diagnostic instruments are installed in so many medical facilities that expert management of these examinations tends to be insufficient. Particularly, in order to avoid risks, clinicians have recently become indifferent to indications of imaging modalities and tend to rely on CT or MRI resulting in increasing the number of imaging examinations in Japan. This is a serious problem from the viewpoints of avoidance of unnecessary exposure and medical economy. Under these circumstances, the Japan Radiological Society and Japanese College of Radiology jointly initiated the preparation of new guidelines for diagnostic imaging. However, the field of diagnostic imaging is extremely wide, and it is impossible to cover all diseases. Therefore, in drafting the guidelines, we selected important diseases and focused on "showing evidence and suggestions in the form of clinical questions (CQs)" concerning clinically encountered questions and "describing routine imaging techniques presently considered to be standards to guarantee the quality of imaging examinations". In so doing, we adhered to the basic principles of assuming the readers to be "radiologists specializing in diagnostic imaging", "simultaneously respecting the global standards and attending to the situation in Japan", and "making the guidelines consistent with those of other scientific societies related to imaging". As a result, the guidelines became the largest ever, consisting of 152 CQs, nine areas of imaging techniques, and seven reviews, but no other guidelines in the world summarize problems concerning diagnostic imaging in the form of CQs. In this sense, the guidelines are considered to reflect the abilities of diagnostic radiologists in Japan. The contents of the guidelines are essential knowledge for radiologists, but we believe that they are also of use to general clinicians and clinical radiological technicians. While the number and contents of CQs are still insufficient, and while chapters such as those on imaging in children and emergency imaging need to be supplemented, the guidelines will be serially improved through future revisions. Lastly, we would like to extend our sincere thanks to the 153 members of the drafting committee who authored the guidelines, 12 committee chairpersons who coordinated their efforts, six members of the secretariat, and affiliates of related scientific societies who performed external evaluation.

Human comparative study of zinc and copper excretion via urine after administration of magnetic resonance imaging contrast agents.

PURPOSE: To evaluate the in-vivo pharmacokinetics of magnetic resonance imaging (MRI) contrast agents, the excretion of zinc and copper via urine was studied for three gadolinium (Gd) chelate complexes. MATERIALS AND METHODS: Urine samples were taken before, three hours, and six hours after intravenous administration of Gd-DTPA-BMA, Gd-DTPA, and Gd-DOTA at 0.2 ml/kg to five patients each who underwent contrast-enhanced MRI. Five patients who had non-contrast MRI were evaluated as controls. Urine was assayed for quantitative analysis of zinc and copper using atomic absorption analysis. RESULTS: Gd-DTPA-BMA caused the highest increase in zinc excretion among the three agents, 1,795 +/- 1,273 microg at 3 hours and 985 +/- 434 microg at 3 to 6 hours. Gd-DOTA did not cause a significant increase in zinc excretion, 75 +/- 39 microg at 3 hours and 78+/-65 microg at 3 to 6 hours. Gd-DTPA caused a moderate increase in zinc excretion, 665 +/- 240 microg at 3 hours and 378 +/- 173 microg at 3 to 6 hours. Excretion of copper did not show a significant difference among the three agents. CONCLUSION: Gd-DOTA was found to be the most kinetically inert among the three agents tested. The difference in zinc excretion among the MR contrast agents is possibly related to in-vivo transmetallation of the Gd chelate complexes correlated with variable stability of the contrast agents. The large amount of excess ligands contained in some MR contrast agents was also considered to be responsible for the increase of urinary zinc excretion.

Increased radiation dose by automatic exposure control system during fluoroscopy and angiography of pelvis due to contrast material in the bladder: experimental study.

PURPOSE: To evaluate the increase of radiation dose caused by contrast material excreted in the bladder during vascular interventional procedures of the pelvis. MATERIALS AND METHODS: A latex balloon filled with diluted contrast material, simulating the bladder, was placed in a water phantom. Entrance dose rates were measured under various conditions with and without the balloon. In animal experiments, skin doses during fluoroscopy and angiographic image acquisitions were measured at the pelvis of a swine before and after the contrast was excreted in the bladder. RESULTS: In phantom experiments, fluoroscopic dose rates increased 1.3- to 3.9-fold when the contrast-filled balloon was placed at the periphery of the phantom. The dose rates increased 3.0- to 4.0-fold when the balloon was placed at the center. In the animal experiment, dose rates increased 1.4- to 2.0-fold when the bladder was filled with contrast material. Skin doses during 10-second angiographic image acquisition also increased 1.1- to 2.3-fold when the bladder was filled with contrast. CONCLUSION: When the bladder is filled with excreted contrast material, skin doses delivered by fluoroscopy and angiography will increase. Removal of urine is recommended during vascular interventional procedures of the pelvis.

Angiographic guidewire with measuring markers: design and clinical experience.

PURPOSE: We have developed an angiographic guidewire with measuring markers to determine accurately how far a guidewire is inserted within a catheter. We investigated whether use of this guidewire reduces the risk of vascular injury and the fluoroscopic time during guidewire manipulations. METHODS: Four markers were put on the surface of the guidewire at 80, 100, 110, and 120 cm from the tip. The actual lengths of 54 catheters from seven manufacturers were measured and compared with the nominal lengths. Sixty consecutive patients who underwent angiography were randomized into two groups: in one group guidewires with surface markers were used (marker group) and in the other group, conventional guidewires (control group). For each guidewire insertion, the fluoroscopic time before the guidewire was pushed forward into the vessel lumen was recorded. The number of occasions on which unintentionally the guidewire had already been pushed out of the catheter at the start of fluoroscopy was also evaluated. RESULTS: The actual lengths of all catheters were greater than the nominal lengths by 1.0-11.0 cm. Mean fluoroscopic time for each guidewire insertion was 3.3 sec in the marker group and 5.7 sec in the control group (p < 0.05). Guidewires were unintentionally pushed out of the catheters without fluoroscopy three times (3.6%), in each case in the control group. CONCLUSION: The guidewire with measuring markers is effective for enhancing safety and in reducing fluoroscopic radiation during angiographic procedures. It is recommended that operators be aware that actual lengths of catheters may vary significantly from the nominal lengths listed; they should be aware of this with any guidewire, but particularly with the angiographic measuring guidewire.