Purpose: The administration accuracy of the automated infusion device for the positron emission radiopharmaceutical affects to calculation of the standardized uptake value (SUV) in ¹⁸F-fluorodeoxyglucose (¹⁸F-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: To calculate the quantitative values in bone single-photon emission computed tomography, it is necessary to measure the amount of syringe radiation before and after the administration of a radiopharmaceutical. We proposed a method to omit the measurement of radioactivity. In this study, we clarified the effects of adopting this method and calculated its influence on quantitative values in a clinical setting. Methods: We derived a relational expression of the administration time and dose of radioactivity from the measured value and the administration time of the syringe dose before and after the administration in each patient. Next, we determined the differences for radioactivity calculated from this relational expression (estimated dose) and actual administered radioactivity (actual dose). Furthermore, we calculated the differences in the quantitative values of a normal region (the fourth lumbar vertebra) on adopting these data. Results: No significant differences between the estimated dose and actual dose were noted. Additionally, no significant differences in the quantitative values were observed. Conclusion: Our findings suggest that adoption of the estimated dose does not affect the quantitative value. When the estimated dose is adopted, it can be administered with an accuracy of 0.80%. Thus, it is possible to omit the actual measurement of radioactivity by using our proposed method.

Purpose: The aim of this study was to evaluate the effect of misregistration between single-photon emission computed tomography (SPECT) and computed tomography (CT) images on bone SPECT. Methods: We acquired SPECT and CT images of a body phantom filled with bone-equivalent solution and ^99mTc for evaluation of bone SPECT. SPECT images were reconstructed using attenuation correction maps obtained by shifting the attenuation coefficients from non-shifted values (reference). Activity concentrations, SPECT standardized uptake values (SPECT-SUVs), and tumor background ratios (TBRs) were evaluated. Results: Activity concentrations and SPECT-SUVs decreased with decreasing attenuation coefficient. The difference in attenuation coefficient was especially large between the shifted-to-lung (0.085 cm⁻¹) and reference (0.249 cm⁻¹) values. Non-shifted and shifted-to-lung SPECT-SUVs were 11.5±1.0 and 2.3±0.2, respectively. TBR also decreased with decreasing attenuation coefficient. The maximum percentage change in TBR was 86% in the shifted-to-lung value. Conclusions: Our results indicate that the accuracy of activity concentration and lesion detectability was commonly affected by misalignment between SPECT and CT images. Although the impact of SPECT/CT misregistration on bone SPECT is case-specific and difficult to predict, it is important to reduce the incidence of misregistration errors for quantitative bone SPECT imaging.

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.

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 ¹⁸F-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 ¹⁸F-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 ¹⁸F-FDG<0.25 mL. In contrast, the values were relatively stable when using the improved kit with dispensed ¹⁸F-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.

Objective: The present study aimed to reveal the influence of combination of different collimators and energy windows on the planar sensitivity and the spatial resolution during experimental ²²³Ra imaging, and to determine optimal imaging parameters. Methods: A vial type source containing ²²³Ra solution (4.55 MBq / 5.6 ml) was placed in the air at 100 mm away from the collimator surface. Planar images were acquired with LEHR, LMEGP, ELEGP and MEGP collimators on two dual-head gamma cameras (Symbia intevo (Siemens) and Infinia 3 (GE)). We compared three energy window combinations: 1) single window at 82 keV, 2) double window at 82+154 keV, 3) triple window at 82+154+270 keV. The energy spectrum, the sensitivity and the spatial resolution, such as full-width at half-maximum (FWHM) and full-width at tenth-maximum (FWTM), of each collimator were assessed. Results: Five energy spectra (at around 82, 154, 270, 351 and 405 keV) were essentially observed among four collimators. The sensitivity was high for LEHR collimator, then ELEGP and LMEGP collimator was 3–4 fold, which is greater than MEGP collimator. The 82 keV energy window of four collimators has best spatial resolution. Moreover, the spatial resolution of the 82 keV energy window with LMEGP and ELEGP collimator was almost equal to that of the triple window with MEGP collimator. Conclusions: Optimal imaging parameters were single energy window using LMEGP or ELEGP, and then triple energy window using MEGP collimator.

Purpose: The purpose of this study was to evaluate the best phantom for calculating the becquerel calibration factor (BCF) and correction method to obtain the improvement of standardized uptake value (SUV) accuracy in both single photon emission computed tomography (SPECT) and SPECT/CT. Method: A SPECT/CT scanner was used in this study. BCFs were calculated using four phantoms with different cross sections including National Electrical Manufacturers Association International Electrotechnical Commission body phantom (NEMA IEC body phantom) filled with ^99mTcO₄^-, and five correction methods were used for reconstruction. SUVs were calculated by the NEMA IEC body phantom and pediatric phantom in house with these BCFs. We then measured SUV_mean in the background region of the NEMA IEC body phantom, SUV_max and SUV_peak of the 37-mm-diameter sphere. Results: In the SPECT scanner, SUV_mean and SUV_max measured 1.04 and 4.02, respectively, in the case of BCF calculation and SUV measurement using NEMA IEC body phantoms without corrections. In the SPECT/CT scanner, SUV_mean with CT attenuation correction (AC) was in agreement with the theoretical values using each phantom. SUV_max showed the same trend. Conclusion: In the SPECT scanner, it is possible to obtain a highly accurate SUV by using a phantom that matches the size of the subject for BCF calculation and without correction. In the SPECT/CT scanner, highly accurate SUVs can be obtained by using CT-based attenuation correction, and these values do not depend on the size of the BCF calculation phantom.

Purpose: Several cross-calibration schemes have been proposed to produce quantitative values in bone SPECT imaging. Differences in the radionuclide sources and geometric conditions can decrease the accuracy of cross-calibration factor (CCF). The present study aimed to validate the effects of calibration schemes using different sources under various geometric conditions. Methods: Temporal variations as well as variations in acquisition counts and the shapes of ⁵⁷Co standard and ^99mTc point sources and a ^99mTc disk source were determined. The effects of the geometric conditions of the source-to-camera distance (SCD) and lateral distance on the CCF were investigated by moving the camera or source away from the origin. The system planar sensitivity of NEMA incorporated into a Symbia Intevo SPECT/CT device (Siemens®) was defined as reference values. Results: The temporal variation in CCF using the ⁵⁷Co source was relatively stable within the range of 0.7% to 2.3%, whereas the ^99mTc source ranged from 2.7% to 7.3%. In terms of source shape, the ⁵⁷Co standard point source was the most stable. Both SCD and lateral distance decreased as a function of distance from the origin. Errors in the geometric condition were higher for the ⁵⁷Co standard point source than the ^99mTc disk source. Conclusions: Different calibration schemes influenced the reliability of quantitative values. The ⁵⁷Co standard point source was stable over a long period, and this helped to maintain the quality of quantitative SPECT/CT imaging data. The CCF accuracy of the ^99mTc source decreased depending on the preparative method. The method of calibration for quantitative SPECT should be immediately standardized to eliminate uncertainty.

Quantification of PET/CT and SPECT/CT using standardized uptake value (SUV) is affected by many factors related to technical factors, such as scanner calibration, imaging physics related factors and patient related factors. Here, I briefly describe some world trend in accuracy of SUVs in PET/CT and SPECT/CT, followed by present and future strategies for clinical practice using SUVs. Finally, I also provided the results of multi-center phantom studies in Japan using SUVs of PET/CT and SPECT/CT.

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 ¹⁸F solution (10.6 kBq/mL). Tumors were simulated using spheres (diameter, 11–38 mm) containing ¹⁸F 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.