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 SUVmean in the background region of the NEMA IEC body phantom, SUVmax and SUVpeak of the 37-mm-diameter sphere. Results: In the SPECT scanner, SUVmean and SUVmax 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, SUVmean with CT attenuation correction (AC) was in agreement with the theoretical values using each phantom. SUVmax 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: This study aimed at analyzing the relationship between the estimated volume of distribution on computed tomography (eVdCT) of non-ionic contrast medium and four different patientsʼ body size parameters (BSPs) (total body weight, body mass index, body surface area, and lean body weight) in abdominal dynamic contrast-enhanced computed tomography (ADCE-CT) . Moreover, this study intended to derive a method for calculating the iodine dose to target contrast enhancement. Methods: We measured enhanced CT values of the equilibrium phase of the abdominal aorta in 527 patients who underwent ADCE-CT. The eVdCT of the ADCE-CT equilibrium phase was calculated from enhanced CT values based on the pharmacokinetic model. The optimal iodine dose (OID) was calculated from the regression analysis of eVdCT and BSP. Results: The eVdCT was 7741.1±1799.5 ml. The eVdCT showed a strong positive correlation with BSP and could be calculated using a linear regression equation. The correlation coefficients for total body weight, body surface area, and lean body weight were 0.83, 0.84, and 0.81, respectively. The OID per unit BSP required for target iodine concentration of the abdominal aorta on ADCE-CT (TIC) could be calculated as “OID [mgI/BSP]=[(a･BSP+b)×TIC]/BSP”. Conclusion: The OID calculation method based on the patientsʼ body size parameters and estimated volume of distribution can normalize contrast enhancement in abdominal dynamic contrast-enhanced CT.
Purpose: To investigate the activation dynamics of language-related areas from multiple activation maps by performing analysis while shifting the signal change model from the actual stimulation timing along the temporal axis using high temporal resolution fMRI data. Methods: High temporal resolution fMRI data were obtained using 3T MRI. Ten healthy right-handed volunteers participated in the study. Task paradigm was block design to carry out two sets of the rest periods and word-generation tasks. Data analysis was performed using SPM 12 software. We created several different activation maps of different phases by shifting the signal change model along the temporal axis, and the activation dynamics of activation areas were analyzed. Results: In the activation dynamics analysis, there was a tendency for activation to become stronger in the order of bilateral superior temporal gyrus and supplementary motor area, left angular gyrus with slight delay, and then left middle and inferior frontal gyrus. This result was considered to reflect the processing process in the brain during the word-generation task. Conclusions: It was suggested that this analysis method is useful for activation dynamics analysis.
Purpose: This study aimed to verify whether cold artifacts caused by the gap state between attenuation correction computed tomography (ACCT) and positron emission tomography (PET) data (so-called hot-in-air (HIA) state) in body trunk PET/computer tomography (CT) examinations can be improved by the Absolute-single scatter simulation (SSS), which is a scatter correction method in a phantom experiment using the high-accumulation syringe of out-of-body phantom. Method: PET imaging profile curves in the HIA state were evaluated using a high-accumulation syringe that simulated a urinary tract pouch encapsulated with 18F-FDG solution. The hot syringe-to-background ratio (HBR) of the syringe was changed to 5, 7, and 10. Moreover, PET image quality evaluation of the HIA state was performed with a syringe placed on the top of a NEMA IEC body phantom. Six spheres (10–37 mm in diameter) were placed inside the phantom and filled with 18F-FDG solution with a sphere-to-background ratio of 4. The evaluation items of image quality were N10 mm, QH, 10 mm / N10 mm, and recovery coefficient (RC). Result: The image quality tended to deteriorate as the HBR of the syringe increased in the relative-SSS, while the effect was small in the Absolute-SSS and the lowest at HBR 10. The RC10 mm of HBR 5 was 0.33 for the Relative-SSS, which was below the criterion for the Relative-SSS, but was 0.5 for the Absolute-SSS, which met the criterion. Conclusion: Absolute-SSS significantly improved cold artifacts caused by HIA states on body trunk PET/CT examinations, suggesting that it is highly useful both visually and quantitatively.
Purpose: For whole-breast irradiation after breast-conserving surgery, computed tomography simulation (CTS) and irradiation are generally performed during free breathing. In treatment planning, there are three techniques: field-in-field (FIF), physical wedge (PW), and enhanced dynamic wedge (EDW). The aim of this study was to investigate the impact of respiratory motion on doses for these three irradiation techniques. Methods: All doses were measured using an ionization chamber in a cylindrical phantom on a respiratory motion platform. Doses for each technique were measured with and without phantom motion. The dose without phantom motion was defined as the reference. The reference was compared to the dose with the phantom motion. The positions of the isocenter with respect to the ranges of phantom motion were set as exhale and intermediate. The phantom motion amplitude was set to 5 mm or 10 mm. The respiratory phase to initiate irradiation was varied as inhale, intermediate-inhale, exhale and intermediate-exhale. Results: When the motion amplitude was 10 mm, the dose differences for the FIF, PW, and EDW techniques were 4.2%, 0.5%, and 0.8%, respectively, at the maximum. However, the dose difference for the FIF technique was –0.5% when the isocenter position was set to the intermediate phase of phantom motion. Conclusion: We found that the dose difference per fraction was reduced when the respiratory phase during CTS image acquisition was set to the intermediate phase. Meanwhile, the dose differences per fraction for the PW and EDW techniques were less affected by the respiratory motion.