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Purpose: This study aimed to investigate the frequency of COVID-19 vaccine-induced reactive change and potential factors including blood type correlated with increased FDG uptake on positron emission tomography (PET)/computed tomography (CT)., Materials and Methods: We evaluated 284 patients who underwent PET/CT between June and September 2021 and had a known history of COVID-19 vaccination. Information on the injection site, vaccine type, and adverse reactions was obtained. We visually assessed the presence or absence of accumulation in the axillary and supraclavicular lymph nodes and the deltoid muscles. We measured the maximum standardized uptake value (SUVmax) using semi-quantitative analysis., Results: Our study included 158 males and 126 females aged 16-94. The median time between vaccination and PET/CT was 9 and 42 days for patients who had received their first and second doses, respectively. We observed axillary lymph node accumulation, supraclavicular lymph node accumulation, and deltoid muscle accumulation in 98 (SUVmax 1.07-25.1), nine (SUVmax 2.28-14.5), and 33 cases (SUVmax 0.93-7.42), respectively. In cases with axillary lymph node (P = 0.0057) or deltoid muscle (P = 0.047) accumulation, the shorter the time since vaccination, the higher the FDG accumulation. Patients with axillary lymph node accumulation were significantly younger (P < 0.0001) and had a significantly higher frequency of adverse reactions such as fever (P < 0.0001) and myalgia (P = 0.002). No significant relationship was observed between blood type and the frequency of FDG accumulation. Logistic regression analysis also showed that age, gender, days since vaccination, and adverse reactions such as fever and myalgia were important factors for axillary lymph node accumulation., Conclusion: Our study found that FDG accumulation in the axillary lymph nodes and deltoid muscle was higher within a shorter time after vaccination, and axillary lymph node accumulation was higher in young patients, females, and those with adverse reactions of fever and myalgia. No significant relationship was observed between blood type and the frequency of FDG accumulation. Confirming the vaccination status, time since vaccination, and the presence of adverse reactions before PET may reduce false positives., (© 2024. The Author(s), under exclusive licence to The Author(s) under exclusive licence to The Japanese Society of Nuclear Medicine.)

Nuclear cardiology has long been used to identify myocardial ischemia for appropriate treatment strategies for stable coronary artery disease (CAD). After the Ischemia Trial, it is time to reevaluate the significance of ischemia assessment. Functional imaging continues to play pivotal role in detecting microcirculatory disturbances. PET provides a clear image of blood flow distribution and is useful for the quantitative evaluation of myocardial flow reserve (MFR), which plays an important role in predicting treatment strategies and improving prognosis in CAD. Heart failure has become a major area of focus in cardiovascular medicine. Radionuclide imaging has been widely applied in this field. FDG PET is useful in identifying cardiac sarcoidosis and active inflammation. Clinical values of I-123 MIBG and BMIPP SPECT have been reported worldwide from Japan. Additionally, clinical experiences of Tc-99m pyrophosphate imaging have recently gained attention for assessing cardiac amyloidosis. Cardiac PET/CT and PET/MR imaging permit combined assessment of metabolic/functional/structural analyses of various cardiac diseases. While other non-invasive imaging modalities have rapidly been developed, the roles of radionuclide imaging remain to be valuable for early and accurate diagnosis and patient management in most cases of chronic CAD and various cardiovascular diseases., (© 2023. The Author(s) under exclusive licence to The Japanese Society of Nuclear Medicine.)

Recently, positron emission tomography (PET) with fibroblast activation protein inhibitor (FAPI) has gained significant attention as an advanced tumor diagnostic imaging tool. FAPI PET has a promising potential owing to its ability to accurately depict most malignant tumors. It has an accuracy that is comparable to or surpassing the diagnostic accuracy of PET using 18 F-fluorodeoxyglucose (FDG). Moreover, FAPI PET can identify malignant lesions that may be inconclusive on FDG PET. Beyond its application in neoplastic disorders, there have been encouraging reports suggesting the utility of FAPI PET in non-neoplastic conditions such as respiratory or cardiac diseases. This article aimed to provide a comprehensive overview of the recently published articles investigating FAPI and discuss its clinical utility with an emphasis on its application in tumor diagnostics. Numerous radiopharmaceutical FAPIs, including 18 F- and 68 Ga-labeled compounds, have been developed, and they offer various advantages and applications. With the progress in the FAPI PET synthesis to enhance accumulation and retention in pathological lesions, future studies are expected to provide valuable data on its therapeutic efficacy., (© 2023. The Author(s) under exclusive licence to The Japanese Society of Nuclear Medicine.)

Objective: This study aimed to compare the contribution of 18 F-fluorodepxyglucose (FDG) positron (PET)/ computed tomography (CT) acquisition of early and delayed scans in patients with cardiac sarcoidosis (CS)., Methods: Twenty-three patients with CS (median age: 69 years; 11 women) were retrospectively evaluated using dual-phase FDG PET/CT. All patients were instructed to consume a low-carbohydrate diet followed by fasting for 18 h before FDG injection to reduce physiological myocardial uptake. PET/CT was acquired at 60 min (early) and 100 min (delayed) after FDG administration. Focal and focal on diffuse uptake on visual analysis was considered positive for CS. A semi-quantitative analysis was performed using the maximum standardized uptake value (SUVmax) of the cardiac lesion and the mean SUV (SUVmean) of the blood pool., Results: Significant myocardial FDG uptake was observed in 21 patients (91.3%) in the early acquisition group and in 23 patients in the delayed scan group (100%). Compared to the early scan, the delayed scan showed a significantly higher SUVmax of the cardiac lesion [median, 4.0; IQR (interquartile range, 2.9 to 7.0) vs. 5.8 (IQR 3.7 to 10.1); P = 0.0030] and a significantly lower SUVmean of blood pool [median, 1.3 (IQR, 1.2 to 1.4) vs. 1.1 (IQR, 0.9 to 1.2); P < 0.0001]., Conclusion: Delayed FDG PET/CT acquisition improves detection accuracy in patients with CS compared to early scans with washout of the blood pool activity. Therefore, it can contribute to a more accurate assessment of CS., (© 2023. The Author(s) under exclusive licence to The Japanese Society of Nuclear Medicine.)

Objectives: The purpose of this study was to examine the diagnostic value of planar 99m Tc-pyrophosphate (PYP) imaging at 1 and 3 h after tracer administration in patients with suspected transthyretin cardiac amyloidosis (ATTR-CA) using SPECT as a reference standard. We also tested whether blood pool activity of PYP is associated with renal dysfunction., Methods: PYP images of 109 consecutive patients with suspected ATTR-CA were retrospectively reviewed. The myocardial PYP uptake was visually graded on a scale of 0 to 3 and quantified with the heart-to-contralateral (H/CL) ratio in accordance with the current expert consensus recommendations. The diagnostic value of planar images for identifying positive PYP SPECT was assessed by a receiver-operating characteristic curve analysis with the area under the curve (AUC). The uptake ratios of the ascending and descending aorta, left atrium, and trapezius muscle divided by the liver uptake were measured on SPECT images and compared to the renal function., Results: A total of 41 patients (38%) had myocardial PYP uptake on SPECT images. In comparison with the visual scores on 1-h anterior planar images, those on 3-h anterior planar images had lower sensitivity (80.5% vs. 97.6%) and higher specificity (86.8% vs. 55.9%) for identifying positive PYP SPECT. The ROC analysis showed that the combination of visual scores on both 1-h and 3-h anterior planar images had significantly higher AUC values in comparison with 1-h anterior planar images alone (0.90 [95% CI 0.83-0.94] vs. 0.83 [95% CI 0.75-0.88]; P < 0.001), which was comparable to the AUC values on 3-h anterior planar images alone (0.88 [95% CI 0.80-0.92]; P = 0.071). In comparison with visual scores on 1-h or 3-h anterior planar images alone, the combination of visual scores and H/CL ratio did not significantly improve the diagnostic value for identifying positive PYP SPECT (P = 0.73 and P = 0.50, respectively). The uptake ratios of ascending aorta/liver, descending aorta/liver, left atrium/liver, and trapezius muscle/liver were not significantly associated with the serum creatinine level or estimated glomerular filtration rate (P > 0.05 for all)., Conclusions: In the assessment of ATTR-CA using PYP imaging, visual scores on 3-h anterior planar images for identifying positive PYP SPECT had lower sensitivity and higher specificity in comparison with those on 1-h anterior planar images. The diagnostic value of the visual scores on 1-h and 3-h anterior planar images was not improved by adding the H/CL ratio. Blood pool activity of PYP was not significantly associated with renal dysfunction., (© 2022. The Author(s) under exclusive licence to The Japanese Society of Nuclear Medicine.)

Positron emission tomography (PET) has been used to noninvasively evaluate myocardial perfusion and metabolism. For clinical assessments of myocardial perfusion, the quantitative capability of PET permits precise assessments of ischemia and microcirculatory dysfunction, playing an important role in patient management and outcome analyses. 18 F-fluorodeoxyglucose (FDG) PET has recently been used to identify active cardiovascular lesions such as cardiac sarcoidosis, endocarditis, and aortitis. This may hold promise for the early and accurate diagnosis of such fatal diseases, as well as for patient management. This review covers new and clinical roles of cardiac PET in treatment strategies and patient outcomes.

Objective: (11)C-acetate has been applied for evaluation of myocardial oxidative metabolism and can simultaneously estimate myocardial blood flow (MBF). We developed a new method using two-parameter spillover correction to estimate regional MBF (rMBF) with (11)C-acetate PET in reference to MBF derived from (15)O-H2O PET. The usefulness of our new approach was evaluated compared to the conventional method using one-parameter spillover correction., Methods: Sixty-three subjects were examined with (11)C-acetate and (15)O-H2O dynamic PET at rest. Inflow rate of (11)C-acetate (K1) was compared with MBF derived from (15)O-H2O PET. For the derivation, the relationship between K1 and MBF from (15)O-H2O was linked by the Renkin-Crone model in 20 subjects as a pilot group. One-parameter and two-parameter corrections were applied to suppress the spillover between left ventricular (LV) wall and LV cavity. Validation was set using the other 43 subjects' data. Finally, rMBFs were calculated using relational expression derived from the pilot-group data., Results: The relationship between K1 and MBF derived from (15)O-H2O PET was approximated as K1 = [1-0.764 × exp(-1.001/MBF)] MBF from the pilot data using the two-parameter method. In the validation set, the correlation coefficient between rMBF from (11)C-acetate and (15)O-H2O demonstrated a significantly higher relationship with the two-parameter spillover correction method than the one-parameter spillover correction method (r = 0.730, 0.592, respectively, p < 0.05)., Conclusion: In (11)C-acetate PET study, the new two-parameter spillover correction method dedicated more accurate and robust myocardial blood flow than the conventional one-parameter method.

Objectives: (123)I-metaiodobenzylguanidine (MIBG) has been used to estimate cardiac sympathetic nervous innervation. Heterogeneous MIBG distribution is mainly associated with high physiological MIBG uptakes in the liver. We postulate that prone position acquisition might be especially effective for MIBG, providing for separation from high liver uptake similar to that provided by perfusion single-photon emission computed tomography (SPECT). We investigated whether prone-position acquisition improved MIBG image quality by comparing our results to those acquired using supine MIBG and high-quality (11)C-hydroxyephedrine (HED) positron emission tomography/computed tomography PET/CT., Methods: Ten male volunteers (body mass index (BMI) 22.7 ± 3.4) underwent prone and supine MIBG and HED PET. Relative regional tracer uptake was estimated in early MIBG and HED. Acquired images were divided into 17 segments and were grouped into 4 regions: anterior, inferior, septum, and lateral. For each patient, the inferior/anterior ratio was calculated., Results: The quality of images acquired using prone MIBG was better than that using supine MIBG (p < 0.05). Inferior and septum relative MIBG uptake was reduced in comparison with anterior or lateral MIBG uptake in the supine position (inferior vs. anterior: 69.0 ± 5.6 vs. 82.3 ± 4.6 %, p < 0.01; septum vs. lateral: 66.2 ± 5.1 vs. 81.9 ± 5.4 %, p < 0.01). Prone MIBG showed a significantly higher inferior/anterior uptake ratio in comparison with supine MIBG (n = 24, seg: 92.2 ± 7.2 vs. 83.6 ± 5.7 %, p < 0.05). However, intergroup differences in uptake ratio were demonstrated among prone and supine MIBG and HED. HED PET/CT still showed a higher uptake ratio in comparison with prone MIBG SPECT (103.9 ± 8.0 vs. 92.2 ± 7.2 %, p < 0.05)., Conclusion: Even in normal male subjects, standard supine MIBG imaging showed reduced inferior and septum uptake. Uptake with prone MIBG imaging showed a significant improvement over that with supine imaging and was closer to uptake for HED PET/CT. This improvement may be the result of preventing intense uptake by the liver. Prone data acquisition may be a viable alternative in evaluating regional abnormalities using MIBG SPECT in men.

Objective: (18)F-FDG PET has become one of the most important methods for studying malignant lymphoma, but its diagnostic role for primary central nervous system lymphoma (PCNSL) has not been established. The aim of this study was to determine the appropriate cut-off values of FDG uptake and to investigate how corticosteroid administration influences PCNSL., Methods: We retrospectively reviewed 82 patients with contrast-enhanced brain tumors who underwent an FDG PET scan at onset, including 19 PCNSLs. FDG uptake of the lesion was assessed by the maximum standardized uptake value (SUVmax) and the ratio of tumor to normal contralateral cortex activity (T/N ratio). Receiver operating characteristic (ROC) curves were generated from the SUVmax and T/N ratios. To investigate the influence of corticosteroid application before a FDG PET scan, we evaluated the association between the FDG uptake of the lesion and the cumulative dose of corticosteroid administration on 13 PCNSL patients who had received steroid treatment before an FDG PET examination., Results: The mean FDG SUVmax and T/N ratio of PCNSLs were 22.6 and 2.79, respectively, and these values were significantly higher than those of the other malignant brain tumors. ROC analysis indicated that the evaluation of FDG uptake using the T/N ratio was more reliable than the SUVmax with respect to the differential diagnosis. When PCNSL patients went without steroid application before FDG PET, the accuracy of the T/N ratio with a cut-off point of 2.0 was 91.1%, the sensitivity was 94.7%, and the specificity was 87.3%. Although there are no significant differences in the FDG T/N ratio for PCNSL patients with or without steroid treatment, a negative correlation was found between the T/N ratio and cumulative dose of corticosteroid before PET study (r = -0.71, p = 0.032)., Conclusions: We concluded that the T/N ratio was superior to SUVmax for FDG uptake assessment as for distinguishing PCNSLs from other malignant brain tumors; the appropriate T/N ratio cut-off point was 2.0. In addition, FDG uptake could be influenced by cumulative doses of corticosteroid before a PET scan, and thus this fact should be taken into consideration when evaluating FDG PET for PCNSL diagnosis.

Purpose: Cardiac sarcoidosis is most commonly found in the left ventricular (LV) free wall. Presence in the right ventricle (RV) is less common but might be useful for detecting cardiac involvement of sarcoidosis. (18)F-fluorodeoxyglucose ((18)F-FDG) PET has been used to detect LV regions with cardiac sarcoidosis. However, the same has not been done for RV involvement. The aims of the current study were to evaluate RV (18)F-FDG uptake and its relationship to the distribution of LV wall (18)F-FDG-positive segments in the LV, and to evaluate whether patients with positive RV (18)F-FDG uptake met the 1993 diagnostic criteria of the Japanese Ministry of Health and Welfare (JMHW) guidelines regarding sarcoidosis with suspected cardiac involvement., Method: Fifty-nine biopsy-proven extra-cardiac sarcoidosis patients (age 56.1 ± 14.7 years) with suspected cardiac involvement based on abnormal electrocardiography or echocardiography findings underwent fasting (18)F-FDG PET or PET/CT. The LV wall was divided into 17 segments and RV uptake was also evaluated., Result: Among 59 patients, 35 (59.3%) showed some abnormal (18)F-FDG uptake in the RV and/or LV wall. With respect to the RV wall, 13 (22.0%) showed abnormal (18)F-FDG uptake. The number of LV-involved segments was 4.8 ± 2.4 in the patients with RV (18)F-FDG uptake, which was significantly higher than in the patients without RV uptake, 1.8 ± 2.2 (P < 0.0001). Patients with RV uptake more frequently met the diagnostic criteria of the 1993 JMHW guidelines (n = 27), than did those without RV uptake (84.6 vs. 34.8%, P = 0.0033)., Conclusion: (18)F-FDG PET identified RV involvement less frequently than LV involvement in this study population. However, patients who had RV uptake showed a greater number of LV-involved segments and met the JMHW diagnostic criteria more frequently. Although RV uptake is less frequent, (18)F-FDG RV uptake may be useful in diagnosing cardiac involvement in sarcoidosis., Clinical Trial Registration: UMIN000006533.

Objective: Application of the electrocardiographically (ECG) gated positron emission tomography (PET) technique with (11)C-hydroxyephedrine (HED) would allow the simultaneous assessment of cardiac sympathetic and contractile functions. However, there are uncertainties regarding the diagnostic accuracy of left ventricular (LV) volume measurements using ECG-gated HED-PET. The purpose of this study was to clarify the minimal requirement of count statistics to measure LV volumes with ECG-gated HED-PET and to investigate the reliability of the measurements., Methods: Five healthy volunteers and 11 patients with heart failure underwent a 40-min list-mode PET scan after an injection of HED (197 ± 35 MBq). The list-mode data were histogrammed into multiple sets of acquisition periods at 0.5, 1.0, 2.0, 4.0, 6.0, 8.0, 12.0 Mcount/bin and reconstructed into corresponding gated images using an iterative algorithm. The LV end-diastolic volume (LVEDV), the LV end-systolic volume (LVESV), and the LV ejection fraction (LVEF) were calculated in each acquisition period. These values were compared with those obtained by cardiac magnetic resonance imaging (MRI). Possible effects of HED retention on the accuracy of the volume measurements were investigated., Results: Collecting less than 4.0 Mcount/bin resulted in noisy cardiac images. The lower counts resulted in underestimation in the volume measurements. Reasonably accurate volume measurements required equal to or greater than 6.0 Mcount/bin. This corresponded to 7.0 ± 1.9 min (range, 4.0-10.3 min) for the acquisition period. Volumetric results using the 6.0 Mcount/bin data highly correlated with cardiac MRI (LVEDV: r = 0.85, p < 0.0001; LVESV: r = 0.89, p < 0.0001; LVEF: r = 0.77, p < 0.01). The HED retention did not affect the volumetric results compared to the MRI volumetry., Conclusions: The volumetric accuracy with ECG-gated HED-PET was affected by the count statistics rather than the HED retention. LV volume measurements were feasible with 10-min acquisition period for most of the patients. This technique allows the simultaneous assessment of cardiac sympathetic and contractile functions without the need for an additional injection or scanning time, thus reducing overall costs for diagnostic imaging.

Objective: It is sometimes difficult to assess I-131 lung uptake at the initial I-131 therapy because of strong artifacts from I-131 uptake in the thyroid bed. The aim of this study was to analyze the lung uptake at the second I-131 therapy for lung metastasis in patients who did not have lung uptake at the initial therapy from differentiated thyroid carcinoma (DTC). Then, we also analyzed the relationship between the initial lung uptake and short-term outcome after I-131 therapies., Methods: This study included 62 DTC patients with lung metastasis. The patients were classified into 2 groups according to the lung uptake at the initial I-131 therapy such as patients with lung uptake (positive uptake group n = 31) and those without lung uptake (negative uptake group n = 31). The lung uptake was analyzed at the second therapy in both groups. The short-term outcome was also analyzed based on the CT findings of lung metastasis size and serum thyroglobulin level between the two groups., Results: The positive uptake group showed positive lung uptake at the second therapy in 23 patients (74 %), whereas none of negative uptake group showed any lung uptake at the second therapy (P < 0.01). The positive uptake group significantly decreased in the size of lung metastasis from the initial therapy to the second therapy (20.0 ± 11.7 to 16.6 ± 9.6 mm, P < 0.01) with further decrease after the second therapy (P < 0.05). The serum thyroglobulin level was also significantly decreased from the initial therapy to the second therapy (4348 ± 7011 to 2931 ± 4484 ng/ml, P < 0.05). In contrast, the negative uptake group significantly increased in the size of lung metastasis from the initial therapy to the second therapy (17.3 ± 12.2 to 19.9 ± 14.3 mm, P < 0.01) with further increase after the second therapy (P < 0.01)., Conclusion: No patients without lung uptake at the initial I-131 therapy showed lung uptake at the second therapy, or showed treatment effect. Therefore, second I-131 therapy for these patients with initially negative lung uptake should be considered cautiously.