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Purpose: The aim of this study was to investigate the leakage radiation dose rate on the surface of an auto infusion device in 18 F-fludeoxyglucose (FDG) positron emission tomography., Method: We preliminary measured the radioactivity of delivery-supplied FDG drugs. Leakage radiation doses on the six (front, rear, right, left, top, and bottom) surface points of the auto infusion device were measured ninety minutes before the assay time using an energy-compensated gamma scintillation survey meter and an ionization chamber-type survey meter., Result: Leakage radiation doses on the front, rear, right, left, and top surfaces were less than 7 µSv/h and satisfied specification of the auto infusion device. However, a leakage dose exceeding 40 µSv/h was detected on the bottom surface.

Purpose: Field of view (FOV) and matrix size determine the pixel size of positron emission tomography (PET) images; however, the effect of any variation in these parameters on the quantitative accuracy is unclear. The FOV and matrix size of PET images are adjusted as per each clinical objective. Therefore, this study aimed to evaluate the quantitative accuracy of PET images under different FOV and matrix sizes., Method: A National Electrical Manufacturers Association (NEMA) body phantom set was filled with 18 F-FDG solution, and imaging data were acquired for 30 min. Images were reconstructed using ordered subset expectation maximization (OSEM) and Bayesian penalized likelihood (BPL), both of which were combined with point spread function (PSF) and time of flight (TOF). In each reconstruction method, the image parameters were set to the following: FOV, 20-70 cm; matrix size, 128×128 to 384×384; and pixel size, 1-3 mm. The images were evaluated by physical assessment of the recovery coefficient (RC) and maximum standardized uptake value ratio (SUV max ratio )., Result: The RC of OSEM images was not affected by changes in FOV, whereas the RC of BPL images decreased in small spheres, when FOV was 20 and 30 cm. The SUV max ratio of the OSEM images was not affected by the difference in pixel size. However, the SUV max ratio of BPL images degraded in the 1-mm pixel size; this influence was observed only when the FOV was changed. Conclusion: BPL images reconstructed using a small FOV might degrade the quantitative accuracy of small spheres.

Purpose: The administration accuracy of the automated infusion device for the positron emission radiopharmaceutical affects to calculation of the standardized uptake value (SUV) in 18 F-fluorodeoxyglucose ( 18 F-FDG) PET examination. The purpose of this study was to investigate the administration error in the clinical use of an automated infusion device for quantitative management in PET examination., Methods: We assumed clinical use of the automated infusion device and investigated two types of administration errors. First, for investigating the administration error over time in a day (error day ), a total of 13 infusion works were performed every 30 minutes. Second, for investigating the long period administration error (error period ), the infusion work was performed once before clinical use of an automated infusion device. The dispensed radioactivity was set to 150 MBq. The administration error was calculated using output values from the automated infusion device and measured values from the dose calibrator., Results: The administration error day was 0.9±1.3%, and the maximum error was 2.7%. The administration error period was 1.1±2.0%, and the maximum error was 5.9%., Conclusion: We investigated the administration error of the automated infusion device. We confirmed the approximately 1% administration error and high-accuracy injection in an automated-device method.

Purpose: We applied deviceless, positron emission tomography/computed tomography(PET/CT) data-driven respiratory gating (DDG) to validate the effects of misalignment between PET and CT at various respiratory phases., Methods: A lung lesion was simulated using an NEMA IEC body phantom in which the background comprised hot spheres containing polystyrene foam beads. We acquired PET images as the phantom moved downwards and then stopped. Attenuation on computed tomography images acquired at the inspiratory, stationary, and expiratory phases was corrected after the phantom stopped moving. Normalized mean square error (NMSE), recovery coefficients (RC max and RC mean ) and volume were analyzed on DDG-PET images using CT-based attenuation correction., Results: The NMSE was closest to 0 in PET images corrected using the expiratory CT image. The RC max was<1.0, and the RC mean was closest to 1.0 only in PET images corrected using the expiratory CT image. Volume was either underestimated or overestimated more according to the size of the spheres when the alignment of CT and PET images was greater., Conclusion: We recommend using the expiratory but not the inspiratory phase when using DDG for PET/CT correction.

In an amyloid PET for visualizing amyloid beta plaque accumulated in the brain, an amyloid imaging agent generally tends to adsorb to the inner walls of materials used in routes of administration to the patient. Therefore, we evaluated the adsorption of the amyloid imaging agent 18 F-flutemetamol by measuring the residual radioactivity of the injection route material (intravenous catheter, extension tube, three-way stopcock) and the dispensed material (needle, syringe) in 35 patients during amyloid PET. The average actual radioactivity administered to the patients was 188.5±6.0 MBq (mean±standard deviation). When the radioactive concentration was 66.5±14.5 MBq/ml, the residual radioactivity was 1.4±0.2% for the injection route material, 0.8±0.3% for the dispensed material and 2.2±0.5% for both materials added based on the radioactivity of the amyloid imaging agent 18 F-flutemetamol used for administration to the patient. There was a correlation between radioactive concentration and residual radioactivity. As the radioactive concentration increased, the residual radioactivity of all the materials tended to increase. Validation of adsorption to the tube and other materials used to administer patients can predict the residual radioactivity of the amyloid imaging agent 18 F-flutemetamol prior to administration.

PET and SPECT provide us with information about biological quantitative values at localized area, even at the deep component of human. They usually have been used for diagnosis, but when combining with radiotherapy, PET and SPECT images would be helpful to make a decision on radiation-dose distribution for treatment because the patient images can be obtained in the similar condition under radiation therapy. In addition, anti-tumor effect of radiation therapy is now precisely controlled for target. Therefore, precise information of tumor, such as extent of tumor and heterogeneity within tumor, would make the treatment more effective, while normal organ functions are preserved. What nuclear medicine can do for the ideal treatment is discussed in this section.

Purpose: The AI-300 automated infusion device (Sumitomo Heavy Industries, Ltd., Tokyo, Japan) is subject to administration error as a function of smaller volumes of 18 F-FDG dispensed via a three-way cock supplied with a disposable kit. The present study aimed to validate the administration accuracy of the AI-300 using an improved disposable kit for quantitative positron emission tomography (PET) assessment., Methods: We determined administration accuracy between the improved and previous disposable kits by measuring variations in dispensed volumes and radioactive concentrations of 18 F-FDG according to the criteria of the Japanese Society of Nuclear Medicine. A reference value was generated by measuring radioactivity using a standard dose calibrator., Results: The values obtained using the previous kit deviated from the reference values by a maximum of -10.6%, and the deviation depended on dispensed volumes of 18 F-FDG<0.25 mL. In contrast, the values were relatively stable when using the improved kit with dispensed 18 F-FDG volumes < 0.25 mL. Variations in radioactive concentrations were relatively stable using the improved kit, whereas that of the previous kit was slightly unstable at high radioactive concentrations., Conclusion: The administration accuracy of the AI-300 using the previous kit varied considerably according to smaller dispensed volumes, but the improved kit might alleviate this problem. The present results indicated that the improved disposal kit should be immediately implemented to eliminate uncertainty surrounding quantitative PET findings.

A high-resolution display panel comes to practical use, but the resolution of the indicated contents does not change. The up-sampling processing is applied to indication of the low-resolution contents. In the up-sampling process, the super resolution enables an up-sampling process which estimates information of high frequency components lost by sampling while analyzing input images is noticed. In this paper, we aimed at reconstructing an image of normal resolution in which the influence of statistical noise is reduced by applying super resolution after down-sampling processing is applied to positron emission tomography (PET) image with many statistical noises. To evaluate the noise reduction effect, we compared it with the Gaussian filter which is frequently used to reduce the influence of the statistical noise of the PET image. A 3D Hoffman brain phantom was used to evaluate objectively by peak signal-to-noise ratio and power spectral density. The objective index of the PET image applying super resolution is positive results, suggesting the possibility of being useful as compared with the conventional method.

Objective: The present study aimed to clarify gross tumor volume (GTV) contouring accuracy at the diaphragm boundary using respiratory-gated PET/CT., Methods: The lung/diaphragm boundary was simulated using a phantom containing 18 F solution (10.6 kBq/mL). Tumors were simulated using spheres (diameter, 11-38 mm) containing 18 F and located at the positions of the lungs and liver. The tumor background ratios (TBR) were 2, 4, and 8. The phantom was moved from the superior to inferior direction with a 20-mm motion displacement at 3.6 s intervals. The recovery coefficient (RC), volume RC (VRC), and standardized uptake value (SUV) threshold were calculated using stationary, non-gated (3D), and gated (4D) PET/CT., Results: In lung cancer simulation, RC and VRC in 3D PET images were, respectively, underestimated and overestimated in smaller tumors, whereas both improved in 4D PET images regardless of tumor size and TBR. The optimal SUV threshold was about 30% in 4D PET images. In liver cancer simulation, RC and VRC were, respectively, underestimated and overestimated in smaller tumors, and when the TBR was lower, but both improved in 4D PET images when tumors were >17 mm and the TBR was >4. The optimal SUV threshold tended to depend on the TBR., Conclusions: The contouring accuracy of GTV was improved by considering TBR and using an optimal SUV threshold acquired from 4D PET images.