Determination of a reliable assessment for occupational eye lens dose in nuclear medicine.

The most recent statement published by the International Commission on Radiological Protection describes a reduction in the maximum allowable occupational eye lens dose from 150 to 20 mSv/year (averaged over 5-year periods). Exposing the eye lens to radiation is a concern for nuclear medicine staff who handle radionuclide tracers with various levels of photon energy. This study aimed to define the optimal dosimeter and means of measuring the amount of exposure to which the eye lens is exposed during a routine nuclear medicine practice. A RANDO human phantom attached to Glass Badge and Luminess Badge for body or neck, DOSIRIS and VISION for eyes, and nanoDot for body, neck, and eyes was exposed to 99m Tc, 123 I, and 18 F radionuclides. Sealed syringe sources of each radionuclide were positioned 30 cm from the abdomen of the phantom. Estimated exposure based on measurement conditions (i.e., air kerma rate constants, conversion coefficient, distance, activity, and exposure time) was compared measured dose equivalent of each dosimeter. Differences in body, neck, and eye lens dosimeters were statistically analyzed. The 10-mm dose equivalent significantly differed between the Glass Badge and Luminess Badge for the neck, but these were almost equivalent at the body. The 0.07-mm dose equivalent for the nanoDot dosimeters was greatly overestimated compared to the estimated exposure of 99m Tc and 123 I radionuclides. Measured dose equivalents of exposure significantly differed between the body and eye lens dosimeters with respect to 18 F. Although accurately measuring radiation exposure to the eye lenses of nuclear medicine staff is conventionally monitored using dosimeters worn on the chest or abdomen, eye lens dosimeters that provide a 3-mm dose equivalent near the eye would be a more reliable means of assessing radiation doses in the mixed radiation environment of nuclear medicine.

Influence of brain atrophy using semiquantitative analysis in [123I]FP-CIT single-photon emission computed tomography by a Monte Carlo simulation study.

The specific binding ratio (SBR) is an objective indicator of N-ω-fluoropropyl-2ß-carbomethoxy-3ß-(4-[123I] iodophenyl) nortropane ([123I]FP-CIT) single-photon emission computed tomography (SPECT) that could be used for the diagnosis of Parkinson's disease and Lewy body dementia. One of the issues of the SBR analysis is that the setting position of the volume of interest (VOI) may contain cerebral ventricles and cerebral grooves. These areas may become prominent during the brain atrophy analysis; however, this phenomenon has not been evaluated enough. This study thus used Monte Carlo simulations to examine the effect of brain atrophy on the SBR analysis. The brain atrophy model (BAM) used to simulate the three stages of brain atrophy was made using a morphological operation. Brain atrophy levels were defined in the descending order from 1 to 3, with Level 3 indicating to the most severe damage. Projection data were created based on BAM, and the SPECT reconstruction was performed. The ratio of the striatal to background region accumulation was set to a rate of 8:1, 6:1, and 4:1. The striatal and the reference VOI mean value were decreased as brain atrophy progressed. Additionally, the Bolt's analysis methods revealed that the reference VOI value was more affected by brain atrophy than the striatal VOI value. Finally, the calculated SBR value was overestimated as brain atrophy progressed, and a similar trend was observed when the ratios of the striatal to background region accumulation were changed. This study thus suggests that the SBR can be overestimated in cases of advanced brain atrophy.

Changing Methods of Education During a Pandemic: Questionnaire Survey about Examinations for Nuclear Medicine Technology at Educational Institutions in Japan.

Coronavirus disease 2019 (COVID-19) has spread around the world. Its effects go far beyond health care: education has to be conducted so as to prevent infection among students and faculty. Accordingly, changes have occurred in Japan's educational institutions, including methods of preparing students for examinations for nuclear medicine. To assess the quality of training for radiologic technologists, we investigated the related changes undertaken at educational institutions. We investigated the lecture format for teaching nuclear medicine technology at Japanese institutions during COVID-19 and efforts to ensure the quality of conventional education. Methods: We sent a questionnaire to 19 Japanese institutions. It addressed the lecture format and initiatives in examinations for nuclear medicine technology in the first and second semesters of 2020. Results: We obtained responses from 17 institutions. In the first semester of 2020, the lecture format for nuclear medicine technology included remote, hybrid (combination of remote and face-to-face), and video-on-demand lectures. To reinforce the effect of the new teaching formats, institutions adopted various methods, such as enhancing the possibility of allowing students to ask questions, increasing the number of quizzes during lectures, delivering lectures to YouTube, and introducing an e-learning system. In the second semester of 2020, the lecture format included face-to-face, remote, hybrid, and video-on-demand lectures. In that second semester, the number of institutions providing face-to-face lectures while taking thorough measures against infection showed a marked increase. Conclusion: The institutions introduced various educational techniques and initiatives. They prioritized students' understanding of lecture content and applied what they considered the best teaching methods. Sharing information about the changes adopted at different institutions should help promote good radiologic technologists-even during a pandemic.

Current state of oncologic 18F-FDG PET/CT in Japan: A nationwide survey.

OBJECTIVES: Combined positron emission tomography/computed tomography (PET/CT) has gradually advanced with the introduction of newly developed techniques. However, the recent status of imaging techniques (e.g., scanning range, availability of correction methods, and decisions on performing delayed scan) in oncologic PET/CT with 18F-fluorodeoxyglucose (18F-FDG) in Japan is unclear. We conducted a nationwide cross-sectional survey to document 18F-FDG PET/CT protocols and clarify the recent status of imaging techniques for oncologic 18F-FDG PET/CT in Japan. METHODS: We conducted a web survey hosted by the Japanese Society of Radiological Technology between October and December 2017. The questionnaire included nine items on the demographics of the respondents, their scan protocols, and additional imaging to their routine protocols. RESULTS: We received responses from 119 Japanese technologists who performed 18F-FDG PET/CT in practice. Almost all the respondents stated that the scanning range was from the top of the head to the pelvis or mid-thigh region. Newly developed techniques were used by fewer than half of the respondents. Most respondents performed additional imaging in consultation with physicians, such as delayed imaging (83%) or an extended scanning range for early imaging (55%). CONCLUSIONS: Our survey helps in clarifying the recent state of oncologic 18F-FDG PET/CT imaging techniques in Japan. Given that 18F-FDG PET/CT practices most frequently performed additional imaging along with their routine scan protocol, the practice constitutes the most varied examination performed in Japanese nuclear medicine.

[Validation of Simulation Codes for Nuclear Imaging Using Digital Phantoms].

Validation study of simulation codes was performed based on the measurement of a sphere phantom and the National Electrical Manufacturers Association (NEMA) body phantoms. SIMIND and Prominence Processor were used for the simulation. Both source and density maps were generated using the characteristics of 99mTc energy. A full width at half maximum (FWHM) of the sphere phantom was measured and simulated. Simulated recovery coefficient and the background count coefficient of variation were also compared with the measured values in the body phantom study. When the two simulation codes were compared with actual measurements, maximum relative errors of FWHM values were 3.6% for Prominence Processor and -10.0% for SIMIND. The maximum relative errors of relative recovery coefficients exhibited 11.8% for Prominence Processor and -2.0% for SIMIND in the body phantom study. The coefficients of variation of the SPECT count in the background were significantly different among the measurement and two simulation codes. The simulated FWHM values and recovery coefficients paralleled measured results. However, the noise characteristic differed among actual measurements and two simulation codes in the background count statistics.

[Radiological Technology for Targeted Radionuclide Therapy].

Targeted radioisotope therapy (TRT) is a radiotherapy using radioisotope or drug incorporating it and has been used as a treatment for selectively irradiating cancer cells. In recent years, interest in TRT has increased due to improvements in radionuclide production technology, development of new drugs and imaging modalities, and improvements in radiation technology. In order to enhance the effect of TRT, measurement of individual radiation doses to tumor tissue and organs at risk is important using highly quantitative nuclear medicine images. In this paper, we present a review of literature on optimization of TRT, which is a new research area from the perspective of radiation technology.

The 2020 national diagnostic reference levels for nuclear medicine in Japan.

The diagnostic reference levels (DRLs) are one of several effective tools for optimizing nuclear medicine examinations and reducing patient exposure. With the advances in imaging technology and alterations of examination protocols, the DRLs must be reviewed periodically. The first DRLs in Japan were established in 2015, and since 5 years have passed, it is time to review and revise the DRLs. We conducted a survey to investigate the administered activities of radiopharmaceuticals and the radiation doses of computed tomography (CT) in hybrid CT accompanied by single photon emission computed tomography (SPECT)/CT and positron emission tomography (PET)/CT. We distributed a Web-based survey to 915 nuclear medicine facilities throughout Japan and survey responses were provided by 256 nuclear medicine facilities (response rate 28%). We asked for the facility's median actual administered activity and median radiation dose of hybrid CT when SPECT/CT or PET/CT was performed for patients with standard habitus in the standard protocol of the facility for each nuclear medicine examination. We determined the new DRLs based on the 75th percentile referring to the 2015 DRLs, drug package inserts, and updated guidelines. The 2020 DRLs are almost the same as the 2015 DRLs, but for the relatively long-lived radionuclides, the DRLs are set low due to the changes in the Japanese delivery system. There are no items set higher than the previous values. Although the DRLs determined this time are roughly equivalent to the DRLs used in the US, overall they tend to be higher than the European DRLs. The DRLs of the radiation dose of CT in hybrid CT vary widely depending on each imaging site and the purpose of the examination.

Current state of bone scintigraphy protocols and practice in Japan.

OBJECTIVES: Nuclear medicine technologists in Japan often perform additional single-photon emission computed tomography (SPECT) with or without computed tomography (CT) after whole-body imaging for bone scintigraphy. In this study, we wanted to identify the bone scanning protocols used in Japan, together with the current clinical practices. METHODS: The study was conducted between October and December 2017. We created a web survey that was hosted by the Japanese Society of Radiological Technology. The questionnaire included 12 items regarding the demographics of the responders, their scan protocols, and the imaging added to, or omitted from, routine protocols. RESULTS: In total, 228 eligible responses were collected from participants with a mean of 11.6±8.4 years' experience in nuclear medicine examination. All responders reported using routine scan protocols that included whole-body imaging. However, only 2%, 4%, 20%, and 14% of the responders also acquired single-field SPECT, single-field SPECT/CT, multi-field SPECT, and multi-field SPECT/CT, respectively. CONCLUSION: Our survey results indicate that nuclear medicine practice in Japan is beginning to shift from planar whole-body imaging with additional spot planar images to additional SPECT or SPECT/CT. Further study is required to examine the optimal protocols for bone scintigraphy.

[A Nationwide Survey on Additional Scan in Nuclear Medicine Imaging].

The aim of the present study was to clarify the routine protocols and the frequency of added or omitted imaging on nuclear medicine imaging in Japan. A nationwide survey on routine protocols and current state of added or omitted imaging in major nuclear medicine imaging were performed for Japanese nuclear medicine technologist. The survey showed that the routine protocols were almost 100% fixed, some of the routine protocols were found to be useful and percentage of imaging techniques such as single photon emission computed tomography/computed tomography that increased patient burden and reduced through put were low. Furthermore, the survey showed that additional or omission imaging were frequently performed on bone scintigraphy and positron emission tomography and added or omitted judgements were often depend upon the rule of thumb by nuclear medicine technologist. In this study, we have concluded that the quality of examination and the diagnosis might depend on the knowledge of nuclear medicine technologist, performed added or omitted imaging.

Imaging technology for myocardial perfusion single-photon emission computed tomography 2018 in Japan.

AIM: Recently, nuclear cardiology has dramatically advanced by a new technology development such as the device, short-term acquisition system, image reconstruction algorithm and image analysis. Although these innovations have been gradually employed in routine examinations, we did not investigate the current use of image acquisition, image reconstruction, and image analysis with myocardial perfusion single-photon emission computed tomography (MPS). We investigated the current status of MPS imaging technology in Japan. METHODS: We carried out a survey using a Web-based questionnaire system, the opening of which was announced via e-mail, and it was available on a website for 3 months. We collected data on the current use of MPS with 201Tl and/or 99mTc agents with respect to routine protocols, image acquisition, image reconstruction, and image analysis. RESULTS: We received responses to the Web-based questionnaire from 178 and 174 people for 99mTc and 201Tl MPS, respectively. The routine protocols of MPS of stress-rest and rest-stress MPS on 1-day protocols with 99mTc were 41.2% and 14.5%, respectively, and the rest-only scan response rate was 23.7%, whereas that of 201Tl MPS was 65.9% with stress-rest MPS, 19.0% with rest-only MPS, and 10.9% with stress-rest MPS adding a rest scan 24 h after injection. The filtered back projection (FBP) method is most commonly used image reconstruction method, yielding 70.5% for 99mTc MPS and 76.8% for 201Tl MPS, including combined FBP and ordered subset expectation maximization method. The results for no-correction (NC) images were 49.2% with 99mTc MPS and 55.2% with 201Tl MPS including the response of NC and combined attenuation correction (AC) and scatter correction (SC) (i.e., ACSC) images. The AC or ACSC images of 99mTc and 201Tl were provided by 30-40% of the institutions surveyed. CONCLUSIONS: We investigated the current status of MPS imaging technology in Japan, and found that although the use of various technical developments has been reported, some of these technologies have not been utilized effectively. Hence, we expect that nuclear medicine technology will be used more effectively to improve diagnosis.

[Global Trends Survey for Targeted Radionuclide Therapy].

Radionuclide therapy has been used to help manage a range of diseases and has a role of growing importance, with an increasing impact on clinical practice globally. A survey in the field of Radionuclide therapy was conducted by reviewing 4199 science abstracts of main conference (Japanese Society of Radiological Technology, Japanese Society of Nuclear Medicine, Japanese Society of Nuclear Medicine Technology, Society of Nuclear Medicine and Molecular Imaging, European Association of Nuclear Medicine) held in 2016. This survey consisted of research content, modality for evaluation, dosimetry, radionuclide, and researcher's country. There tend to be a lot of studies related to targeted radionuclide therapy more than Japan (4%) in the United States (11%) or Europe (13%). Radiopharmaceuticals still un-approving in Japan were used in some of these studies. And many studies on dosimetry using PET or SPECT imaging were confirmed in the United States (37%) or in Europe (25%) compared with in Japan (14%). This survey has clarified the current status of Japan and global trend in the field of radionuclide therapy.

Elimination of scattered gamma rays from injection sites using upper offset energy windows in sentinel lymph node scintigraphy.

OBJECTIVE: The identification of sentinel lymph nodes (SLNs) near injection sites is difficult because of scattered gamma rays. The purpose of this study was to investigate the optimal energy windows for elimination of scattered gamma rays in order to improve the detection of SLNs. METHODS: The clinical study group consisted of 56 female patients with breast cancer. While the energy was centred at 140 keV with a 20% window for Tc-99m, this energy window was divided into five subwindows with every 4% in planar imaging. Regions of interest were placed on SLNs and the background, and contrast was calculated using a standard equation. The confidence levels of interpretations were evaluated using a five-grade scale. RESULTS: The contrast provided by 145.6 keV±2% was the best, followed by 140 keV±2%, 151.2 keV±2%, 134.4 keV±2% and 128.8 keV±2% in that order. When 128.8 keV±2% and 134.4 keV±2% were eliminated from 140 keV±10% (145.6 keV±6%), the contrast of SLNs improved significantly. The confidence levels of interpretation and detection rate provided by the planar images with 140 keV±10% were 4.74±0.58 and 94.8%, respectively, and those provided by 145.6 keV±6% were 4.94±0.20 and 100%. CONCLUSION: Because lower energy windows contain many scattered gamma rays, upper offset energy windows, which exclude lower energy windows, improve the image contrast of SLNs near injection sites.

Optimization of attenuation and scatter corrections in sentinel lymph node scintigraphy using SPECT/CT systems.

OBJECTIVE: Although SPECT/CT systems have been used for sentinel lymph node (SLN) imaging, few studies have focused on optimization of attenuation correction (AC) and scatter correction (SC). While SLNs could be detected in conventional planar images, they sometimes do not appear in SPECT/CT images. The purpose of this study was to investigate the optimal AC and SC and to improve the detectability of SLNs in examinations using SPECT/CT systems. MATERIALS AND METHODS: The study group consisted of 56 female patients with breast cancer. In SPECT/CT imaging, four kinds of images were created with and without AC and SC; namely, AC-SC-, AC+SC-, AC-SC+ and AC+SC+. Five nuclear medicine physicians interpreted the planar and SPECT/CT images with five grades of confidence levels (1-5). The detection rate was calculated as the number of patients whose average confidence levels of interpretation were more than 4, divided by the total number of patients. RESULTS: The confidence level of interpretation and the detection rate provided by the planar images were 4.76 ± 0.49 and 94.6 %, respectively. In SPECT/CT imaging, the AC+SC- provided the best detection rate (confidence level of interpretation, 4.81 ± 0.38; detection rate, 98.2 %), followed by the AC-SC- (4.70 ± 0.55, 89.3 %), and the AC-SC+ (4.39 ± 1.2, 78.6 %). The lowest values were obtained for the AC+SC+ (4.36 ± 1.22, 78.6 %). Regarding the confidence levels of interpretation, significant differences were observed between AC+SC- and AC-SC-, AC+SC- and AC+SC+, AC+SC- and AC-SC+, and between planar images and AC+SC+ (P = 0.0021, 0.0009, 0.0013, and 0.0056, respectively). CONCLUSIONS: When SPECT/CT was used, AC improved the detection of SLNs. SC caused disappearance of a faint SLN in some cases and should not be performed.

Validation of threshold method for myocardial control database by use of clinical data.

A database is an important factor in the statistical analysis of myocardial scintigraphy. Our aim in this study was to verify the validity of the threshold method using phantoms and to create a clinical database using this method. Since this method involves artificially excluding a low count area on a polar map, we created a myocardial phantom with defects. Then, we applied this method to the construction of a control database (CDB) for which we used stress-rest scans of 152 male and 52 female Japanese patients. The clinical relevance of this database was investigated by comparison of the values between the CDB and a Japanese normal database. In the study evaluation, we mainly used the summed extent score (SES) and a severity map (severity). Data from the phantom with defects demonstrated that the threshold method could compensate for defective areas, enabling the use of data for the creation of the CDB. Comparison of the CDB with the Japanese normal database showed a good relationship with respect to the SES and severity (Initial post-stress: SES: r = 0.978; severity: r = 0.997, Redistribution: SES: r = 0.944; severity: r = 0.993). The threshold method facilitates the effective creation of a database by use of clinical data. This enables individual institutions to build their own databases, taking into account differences in collection and processing conditions between institutions as well as the characteristics of individual equipment.