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.

Clinical utility of the normal database of 123I-iodoamphetamine brain perfusion single photon emission computed tomography for statistical analysis using computed tomography-based attenuation correction: a multicenter study.

OBJECTIVES: We have established a common normal database (NDB) with applicability in multicenter settings for the statistical analysis of brain perfusion single photon emission computed tomography (SPECT) with triple energy window scatter correction, computed tomography-based attenuation correction (CTAC), and spatial resolution compensation. This study aimed to compare the CTAC normal database (CTAC-NDB) with conventional normal databases for the statistical analysis of 123I-iodoamphetamine (123I-IMP) brain perfusion SPECT at three institutions and to assess the clinical efficiency of CTAC-NDB. METHODS: We recruited 45 patients (26 men and 19 women; mean age, 74.2 ± 3.9 years; Mini-Mental State Examination score, 19.8 ± 6.1) with Alzheimer's disease (AD, n = 26), dementia with Lewy bodies (DLB, n = 9), and mild cognitive impairment (n = 10) from three institutions. Three-dimensional stereotactic surface projection (3D-SSP) technique was used to analyze data obtained from the 123I-IMP brain perfusion SPECT images compared with both CTAC-NDB and conventional NDB. We visually assessed each 3D-SSP z score map to determine the changes in specific findings, such as AD/DLB pattern. Furthermore, the stereotactic extraction estimation analysis software was used to measure the regional z score severity and extent as a semiquantitative assessment. RESULTS: In the visual assessment, all cases exhibited clearer findings with CTAC-NDB than with conventional NDB in the parietotemporal association cortex as well as in the inferior temporal, frontal, and lateral occipital cortices. Contrarily, the findings from the medial cerebral regions, including the precuneus and the posterior cingulate, became indistinct in 71% of the cases and remained unchanged in 25% of the cases. In the semiquantitative analysis, a similar tendency was observed in the mean z score in the three institutions included in the study. CONCLUSION: Using the CTAC-NDB, the findings in the vicinity of the cranium became increasingly clear, whereas those in the medial surface of the brain became less defined or remained unchanged. These findings were confirmed via a semiquantitative analysis. Moreover, similar changes in the reduction pattern were observed in the three institutions. Therefore, the new database with CTAC might be applicable in other institutions. Data collected in this study may serve as a CTAC-NDB.

Fluctuation of quantitative values on acquisition time and the reconstruction conditions in 99mTc-SPECT.

OBJECTIVE: This study aims to carry out a quantitative analysis with high reproducibility using single-photon emission computed tomography/computed tomography (SPECT/CT); we investigated the optimum parameters for the acquisition and the reconstruction. MATERIALS AND METHODS: SPECT images were acquired with varying time per view using SPECT phantom (JS-10) and the body phantom of National Electrical Manufacturers Association and International Electrotechnical Commission (Body-phantom), respectively. For the image reconstruction condition, we changed the product of subset and iteration (SI product) and the Gaussian filter using a three-dimensional ordered subset expectation maximization. A combination of no scattering correction and no attenuation correction (SC-/AC-) and a combination of scattering correction and attenuation correction by CT images (SC+/AC+) were performed. The dose linearity, the recovery coefficient, the scatter ratio, and the coefficient of variation were evaluated using JS-10. Using Body-phantom, contrast-to-noise ratios of the hot spheres (13, 17 mm) were calculated. Moreover, the change in the maximum standardized uptake value (SUVmax) and the average SUV (SUVmean) were evaluated for each sphere. RESULT: From the evaluation results using the JS-10, dose linearity, recovery coefficient, scatter ratio, and coefficient of variation were all good when time per view was 50-150 s, the Gaussian filter was 8-12 mm, and the SI product was 150. From the evaluation results using Body-phantom, comparing the Gaussian filter with 8 mm and 12 mm, the contrast-to-noise ratio was better for 12 mm and the error rate to the change of the scan-time was up to 3.7%. However, SUVmax and SUVmean using 8 mm were closer to the design value of the phantom. CONCLUSION: It is necessary that Quantitative SPECT be acquired at 50 s or more per view per detection, reconstructed using a three-dimensional ordered subset expectation maximization with SC+/AC+, the SI product is 150 times, and the Gaussian Filter is 8-12 mm. This suggested that the quantitative analysis would be carried out with good reproducibility.

CT-based attenuation correction and resolution compensation for I-123 IMP brain SPECT normal database: a multicenter phantom study.

OBJECTIVE: Statistical image analysis of brain SPECT images has improved diagnostic accuracy for brain disorders. However, the results of statistical analysis vary depending on the institution even when they use a common normal database (NDB), due to different intrinsic spatial resolutions or correction methods. The present study aimed to evaluate the correction of spatial resolution differences between equipment and examine the differences in skull bone attenuation to construct a common NDB for use in multicenter settings. METHODS: The proposed acquisition and processing protocols were those routinely used at each participating center with additional triple energy window (TEW) scatter correction (SC) and computed tomography (CT) based attenuation correction (CTAC). A multicenter phantom study was conducted on six imaging systems in five centers, with either single photon emission computed tomography (SPECT) or SPECT/CT, and two brain phantoms. The gray/white matter I-123 activity ratio in the brain phantoms was 4, and they were enclosed in either an artificial adult male skull, 1300 Hounsfield units (HU), a female skull, 850 HU, or an acrylic cover. The cut-off frequency of the Butterworth filters was adjusted so that the spatial resolution was unified to a 17.9 mm full width at half maximum (FWHM), that of the lowest resolution system. The gray-to-white matter count ratios were measured from SPECT images and compared with the actual activity ratio. In addition, mean, standard deviation and coefficient of variation images were calculated after normalization and anatomical standardization to evaluate the variability of the NDB. RESULTS: The gray-to-white matter count ratio error without SC and attenuation correction (AC) was significantly larger for higher bone densities (p < 0.05). The count ratio error with TEW and CTAC was approximately 5% regardless of bone density. After adjustment of the spatial resolution in the SPECT images, the variability of the NDB decreased and was comparable to that of the NDB without correction. CONCLUSION: The proposed protocol showed potential for constructing an appropriate common NDB from SPECT images with SC, AC and spatial resolution compensation.

[Development of a Striatal and Skull Phantom for Quantitative 123I-FP-CIT SPECT].

BACKGROUND: 123Iodine-labelled N-(3-fluoropropyl) -2ß-carbomethoxy-3ß-(4-iodophenyl) nortropane (123I-FP-CIT) single photon emission computerized tomography (SPECT) images are used for differential diagnosis such as Parkinson's disease (PD). Specific binding ratio (SBR) is affected by scattering and attenuation in SPECT imaging, because gender and age lead to changes in skull density. It is necessary to clarify and correct the influence of the phantom simulating the the skull. PURPOSE: The purpose of this study was to develop phantoms that can evaluate scattering and attenuation correction. METHODS: Skull phantoms were prepared based on the measuring the results of the average computed tomography (CT) value, average skull thickness of 12 males and 16 females. 123I-FP-CIT SPECT imaging of striatal phantom was performed with these skull phantoms, which reproduced normal and PD. SPECT images, were reconstructed with scattering and attenuation correction. SBR with partial volume effect corrected (SBRact) and conventional SBR (SBRBolt) were measured and compared. RESULTS: The striatum and the skull phantoms along with 123I-FP-CIT were able to reproduce the normal accumulation and disease state of PD and further those reproduced the influence of skull density on SPECT imaging. The error rate with the true SBR, SBRact was much smaller than SBRBolt. CONCLUSION: The effect on SBR could be corrected by scattering and attenuation correction even if the skull density changes with 123I-FP-CIT on SPECT imaging. The combination of triple energy window method and CT-attenuation correction method would be the best correction method for SBRact.

(89)Sr bremsstrahlung single photon emission computed tomography using a gamma camera for bone metastases.

OBJECTIVE: Strontium-89 chloride ((89)Sr) bremsstrahlung single photon emission computed tomography (SPECT) imaging was evaluated for detecting more detailed whole body (89)Sr distribution. METHODS: (89)Sr bremsstrahlung whole body planar and merged SPECT images were acquired using two-detector SPECT system. Energy window A (100 keV ± 50 %) for planar imaging and energy window A plus adjacent energy window B (300 keV ± 50 %) for SPECT imaging were set on the continuous spectrum. Thirteen patients with multiple bone metastases were evaluated. Bone metastases can be detected with (99m)Tc-HMDP whole body planar and merged SPECT images and compared with (89)Sr bremsstrahlung whole body planar and merged SPECT images. Based on the location of metastatic lesions seen as hot spots on (99m)Tc-HMDP images as a reference, the hot spots on (89)Sr bremsstrahlung images were divided into the same bone parts as (99m)Tc-HMDP images (a total of 35 parts in the whole body), and the number of hot spots were counted. We also evaluated the incidence of extra-osseous uptakes in the intestine on (89)Sr bremsstrahlung whole body planar images. RESULTS: A total of 195 bone metastatic lesions were detected in both (99m)Tc-HMDP whole body planar and merged SPECT images. Detection of hot spot lesions in (89)Sr merged SPECT images (127 of 195; 66 %) was more frequent than in (89)Sr whole body planar images (108 of 195; 56 %), based on metastatic bone lesions in (99m)Tc-HMDP whole body planar and merged SPECT images. A large intestinal (89)Sr accumulation was detected in 5 of the 13 patients (38 %). CONCLUSIONS: (89)Sr bremsstrahlung-merged SPECT imaging could be more useful for detailed detection of whole body (89)Sr distribution than planar imaging. Intestinal (89)Sr accumulation due to (89)Sr physiologic excretion was detected in feces for 4 days after tracer injection.

[A trial of 89Sr bremsstrahlung SPECT].

OBJECTIVE: 89Sr bremsstrahlung SPECT imaging has been evaluated for detecting the more detailed whole body 89Sr distribution. METHODS: 89Sr bremsstrahlung whole body planar and merged SPECT images were acquired by using two detectors type SPECT system. Energy window A (100 keV +/- 50%) for planar imaging, and energy window A plus adjacent energy window B (300 keV +/- 50%) for SPECT imaging were set on the continuous spectrum. Those images were compared with 99mTc-H-MDP whole body planar and merged SPECT images. To verify the accumulation obtained by bremsstrahlung whole body planar and merged SPECT image, we made original phantom based on the counts of clinical study imaging. RESULTS: On 89Sr bremsstrahlung merged SPECT image, focal accumulations were recognized in the parts of 99mTc-H-MDP merged SPECT accumulation. Focal accumulations were much clearer on 89Sr bremsstrahlung merged SPECT imaging than those of whole body planar image of 89Sr bremsstrahlung. In phantom study, counts of each concentration linearly increase as acquisition time and number of rotation increase on planar and SPECT images. CONCLUSIONS: 89Sr bremsstrahlung merged SPECT imaging would be useful for detecting the more detailed whole body 89Sr distribution.