Prognostic value of left ventricular mechanical dyssynchrony indices derived from gated myocardial perfusion SPECT in coronary artery disease: a systematic review and meta-analysis.

PURPOSE: Left ventricular mechanical dyssynchrony (LVMD) is an important prognostic factor in coronary artery disease. A growing body of evidence indicates that LVMD parameters derived from phase analysis of gated myocardial SPECT may allow risk stratification for future cardiac events. We performed a systematic review and meta-analysis on the prognostic value of LVMD on gated SPECT in patients with coronary artery disease. METHODS: PubMed, Embase, and the Cochrane library were searched until August 25, 2022, for studies reporting the prognostic value of LVMD on gated SPECT for outcomes of all-cause death, cardiac death, or major adverse cardiovascular event (MACE) in patients with coronary artery disease. Hazard ratios (HRs) and their 95% confidence intervals (CIs) were meta-analytically pooled using a random-effects model. RESULTS: Nine studies (26,750 patients) were included in a qualitative synthesis. Among the SPECT LVMD parameters used in various studies, high phase standard deviation, phase bandwidth, and phase entropy were widely evaluated and reported to be associated with high rates of all-cause death, cardiac death, or MACE. For five studies (23,973 patients) in the quantitative synthesis, the pooled HR of LVMD for predicting MACE was 2.81 (95% CI 2.03-3.88). Studies using combined phase parameters to define LVMD showed higher HRs than a study using phase entropy (p = 0.0180). CONCLUSION: LVMD from gated myocardial SPECT is a significant prognostic factor for coronary artery disease. Phase analysis of gated SPECT may be useful for accurate risk stratification and could be applied for clinical decision-making in such patients.

Discordant Uptake of Leg Thrombi Versus Pulmonary Emboli on 68 Ga-FAPI-46 PET/CT.

ABSTRACT: Fibroblast activation protein inhibitor (FAPI) PET is gaining clinical relevance for visualizing activated fibroblasts in various diseases. Here, we report discordant FAPI uptake between venous thrombi of the lower extremities and pulmonary emboli. An 86-year-old man complained of left leg swelling and acute dyspnea; he was diagnosed with deep vein thrombosis involving the left femoral vein and acute pulmonary thromboembolism. Positive FAPI uptake was observed only in the thrombi of the left femoral vein, but not in the pulmonary emboli. Such discrepancies may indicate different thrombus constituents and chronologies even in the same patient.

Tc-99m DMSA SPECT for Follow-Up of Non-Operative Treatments in Renal Injuries: A Prospective Single-Center Study.

OBJECTIVE: The assessment of cortical integrity following renal injuries with planar Tc-99m dimercaptosuccinic acid (DMSA) scintigraphy depends on measuring relatively decreased cortical uptake (i.e., split renal function [SRF]). We analyzed the additive values of the volumetric and quantitative analyses of the residual cortical integrity using single-photon emission computed tomography (SPECT) compared to the planar scintigraphy. MATERIALS AND METHODS: This prospective study included 47 patients (male:female, 32:15; age, 47 ± 22 years) who had non-operatively managed renal injuries and underwent DMSA planar and SPECT imaging 3-6 months after the index injury. In addition to planar SRF, SPECT SRF, cortical volume, and absolute cortical uptake were measured for the injured kidney and both kidneys together. The correlations of planar SRF with SPECT SRF and those of SRF with volumetric/quantitative parameters obtained with SPECT were analyzed. The association of SPECT parameters with renal function, grades of renal injuries, and the risk of renal failure was also analyzed. RESULTS: SPECT SRF was significantly lower than planar SRF, with particularly higher biases in severe renal injuries. Planar and SPECT SRF (dichotomized with a cutoff of 45%) showed 19%-36% of discrepancies with volumetric and quantitative DMSA indices (when dichotomized as either high or low). Absolute cortical uptake of the injured kidney best correlated with glomerular filtration rate (GFR) at follow-up (ρ = 0.687, P < 0.001) with significant stepwise decreases by GFR strata (90 and 60 mL/min/1.73 m²). Total renal cortical uptake was significantly lower in patients with moderate-to-high risk of renal failure than those with low risk. However, SRF did not reflect GFR decrease below 60 mL/min/1.73 m² or the risk of renal failure, regardless of planar or SPECT (count- or volume-based SRF) imaging. CONCLUSION: Quantitative measurements of renal cortical integrity assessed with DMSA SPECT can provide more clinically relevant and comprehensive information than planar imaging or SRF alone.

Acute respiratory distress syndrome and severe pneumonitis after atezolizumab plus bevacizumab for hepatocellular carcinoma treatment: A case report.

BACKGROUND: Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide and has a high mortality. However, the treatment options for advanced HCC are limited to tyrosine kinase inhibitors, such as sorafenib and lenvatinib. Since previous regimens have an insufficient efficacy, the combination therapy of atezolizumab and bevacizumab (Ate/Bev) has been investigated, which showed an improvement in progression-free and overall survival. However, the adverse events of this combination therapy in advanced HCC have not been established. Herein, we report a novel case of an unresectable HCC and acute respiratory distress syndrome (ARDS) after a combination therapy of Ate/Bev. CASE SUMMARY: An 82-year-old male visited our outpatient clinic for an incidentally detected liver mass. Liver magnetic resonance imaging and enhanced chest computed tomography (CT) were performed, which showed arterial hyperenhancement with washout in delayed phase suggesting HCC, and a well-defined metastatic solid nodule, respectively. F-18 fluorodeoxyglucose positron emission tomography (PET)-CT exhibited multiple hypermetabolic lesions in the iliac bone, lumbar vertebrae, and femur. Because of the high burden of the intrahepatic tumor, transarterial radioembolization was initially performed; after 37 d, a combination therapy of Ate/Bev was administered. The patient visited the emergency department three days after Ate/Bev treatment complaining of dyspnea. He was diagnosed with severe pneumonitis based on CT. Despite administering oxygen via a high-flow nasal cannula, the P/F ratio was only 74; therefore, the patient was diagnosed with ARDS based on the overall examination results. Low tidal volume with high positive end-expiratory pressure, sedative agents combined with a neuromuscular blocker, and a systemic steroid were promptly applied to manage the ARDS. However, the patient did not recover from the hypoxia and expired 31 h after being admitted. CONCLUSION: Clinicians should be aware of severe pneumonitis due to the immune-related adverse events of this combination therapy, and patients should be closely monitored after therapy.

Case report: A fatal case of myocardial infarction due to myocardial bridge and concomitant vasospasm: the role of stress gated SPECT.

Introduction: Although most cases of myocardial bridge (MB) are clinically benign, sometimes it can be one of potential threats of myocardial infarction (MI) and life-threatening arrhythmia. In the present study, we present a case of ST-segment elevation MI caused by MB and concomitant vasospasm. Case Presentation: A 52-year-old woman was brought to our tertiary hospital due to resuscitated cardiac arrest. Because the 12-lead electrocardiogram indicated ST-segment elevation MI, coronary angiogram was promptly commenced, which showed near-total occlusion at the middle portion of left anterior descending coronary artery (LAD). After intracoronary nitroglycerin administration, this occlusion was dramatically relieved, however, systolic compression at this site remained, indicative of myocardial bridge (MB). Intravascular ultrasound also showed eccentric compression with a "half-moon" sign, which is consistent with MB. Coronary computed tomography also showed a bridged coronary segment surrounded by myocardium at the middle portion of LAD. To assess the severity and extent of myocardial damages and ischemia, myocardial single photon emission computed tomography (SPECT) was additionally conducted, showing a moderate fixed perfusion defect around the cardiac apex, suggesting MI. After receiving optimal medical therapy, the patient's clinical symptoms and signs were improved then the patient was discharged from the hospital successfully and uneventfully. Conclusion: We demonstrated a case of MB-induced ST-segment elevation MI which was confirmed with its perfusion defects via myocardial perfusion SPECT. There have been proposed a number of diagnostic modalities to examine its anatomic and physiologic significance. Among them, myocardial perfusion SPECT can be available as one of useful modalities to evaluate the severity and extent of myocardial ischemia in patients with MB.

Applying Pix2pix to Translate Hyperemia in Blood Pool Image into Corresponding Increased Bone Uptake in Delayed Image in Three-Phase Bone Scintigraphy.

Purpose: Delayed images may not be acquired due to severe pain, drowsiness, or worsening vital signs while waiting after blood pool imaging in three-phase bone scintigraphy. If the hyperemia in the blood pool image contains information from which increased uptake on the delayed images can be inferred, the generative adversarial network (GAN) can generate the increased uptake from the hyperemia. We attempted to apply pix2pix, a type of conditional GAN, to transform hyperemia into increased bone uptake. Methods: We enrolled 1464 patients who underwent three-phase bone scintigraphy for inflammatory arthritis, osteomyelitis, complex regional pain syndrome (CRPS), cellulitis, and recent bone injury. Blood pool images were acquired 10 min after intravenous injection of Tc-99 m hydroxymethylene diphosphonate, and delayed bone images were obtained after 3 h. The model was based on the open-source code of the pix2pix model with perceptual loss. Increased uptake in the delayed images generated by the model was evaluated using lesion-based analysis by a nuclear radiologist in areas consistent with hyperemia in the blood pool images. Results: The model showed sensitivities of 77.8% and 87.5% for inflammatory arthritis and CRPS, respectively. In osteomyelitis and cellulitis, their sensitivities of about 44% were observed. However, in cases of recent bone injury, the sensitivity was only 6.3% in areas consistent with focal hyperemia. Conclusion: The model based on pix2pix generated increased uptake in delayed images matching the hyperemia in the blood pool image in inflammatory arthritis and CRPS.

Association between myocardial ischemia and plaque characteristics in chronic total occlusion.

BACKGROUND: Myocardial ischemia varies in chronic total occlusion (CTO) despite the occluded artery. We analyzed whether it is associated with the plaque characteristics of the occluded segment. METHODS: We retrospectively enrolled 100 patients with CTO who underwent myocardial perfusion single-photon emission computed tomography (SPECT) and coronary computed tomography angiography (CCTA) within 2 months. CTO-related ischemia was classified as moderate to severe (summed difference score [SDS] of the CTO territory ≥ 5) or mild or none (SDS < 5) on SPECT. Using CCTA, the atherosclerotic plaques of the occluded segment were subdivided into low-density (- 100-30 HU), intermediate-density (31-350 HU), and high-density (351-1000 HU) plaques. The plaque composition was compared according to the severity of CTO-related ischemia. RESULTS: Moderate-to-severe CTO-related ischemia (n = 23) showed significantly higher proportion of intermediate-density plaques (72.4% vs. 64.0%), intermediate/low-density (7.10 vs. 3.65) and intermediate-to-high/low-density (7.78 vs. 3.80) plaque ratios, frequent shorter occlusion (30% vs. 6%), and lower volume (26.5 mm3 vs. 58.8 mm3) and proportion (11.4% vs. 20.8%) of low-density plaques. Multivariable analysis revealed significant associations between higher proportion of intermediate-density plaques and moderate-to-severe CTO-related ischemia, independent of occlusion length. CONCLUSION: Higher proportion of intermediate-density plaques in the occluded segment was associated with the moderate-to-severe CTO-related ischemia.

Evaluation of Non-infarct-Related Arteries Using C-11 Acetate PET in STEMI With Multivessel Disease.

BACKGROUND: We analyzed whether C-11 acetate positron emission tomography (PET) can be used for the evaluation of non-infarct-related artery (NIRA) in patients with ST-elevation myocardial infarction (STEMI) and multivessel disease. METHODS: We prospectively enrolled 31 patients with STEMI and at least one NIRA stenosis (diameter stenosis [DS] ≥ 50%). C-11 acetate PET was performed after successful revascularization for the infarct-related artery (IRA). Myocardial blood flow (MBF) and oxidative metabolism (kmono) were measured and compared between NIRA vs. IRA, stenotic (DS ≥ 50%) vs. non-stenotic (DS < 50%) NIRAs, and NIRAs with significant stenosis (DS ≥ 70% or fractional flow reserve [FFR] ≤ 0.80) vs. those without (neither DS ≥ 70% nor FFR ≤ 0.80). The correlations between PET and angiographic parameters were also analyzed. RESULTS: MBF and kmono were significantly higher in NIRAs than those in IRAs. Stenotic NIRAs showed significantly reduced stress MBF, myocardial flow reserve (MFR), relative flow reserve (RFR) (0.72 ± 0.12 vs. 0.82 ± 0.14; p = 0.001), and stress kmono, as compared to those in non-stenotic NIRAs. NIRAs with significant stenosis had significantly lower stress MBF, MFR, and RFR (0.70 ± 0.10 vs. 0.80 ± 0.14; p = 0.001). RFR showed the best, but modest linear correlation with DS of NIRA stenosis (r = -0.429, p = 0.001). RFR > 0.81 could effectively exclude the presence of significant NIRA stenosis. CONCLUSIONS: C-11 acetate PET could be a feasible alternative noninvasive modality in patients with STEMI and multivessel disease, by excluding the presence of significant NIRA stenosis.

Prediction of cardiac events following concurrent chemoradiation therapy for non-small-cell lung cancer using FDG PET.

OBJECTIVE: No imaging biomarkers are available for the prediction of cardiac events following concurrent chemoradiation therapy (CCRT) for non-small-cell lung cancer (NSCLC). We evaluated whether F-18 fluorodeoxyglucose positron emission tomography (FDG PET) early after CCRT, in addition to cardiac dosimetry, could predict late cardiac events in NSCLC. METHODS: We retrospectively enrolled 133 consecutive patients with locally advanced, unresectable stage III NSCLC, who underwent FDG PET early after CCRT and survived at least 6 months. The primary endpoint was cardiac event ≥ grade 2 according to the Common Terminology Criteria for Adverse Events (version 5.0). Myocardial FDG uptake was measured and its association with the risk of cardiac events was evaluated. RESULTS: FDG PET was performed after a median interval of 11 days of completing CCRT. Overall, 42 (32%) patients experienced cardiac events during a median follow-up of 45 months. The mean heart dose, maximum left ventricular (LV) standardized uptake value (SUV), changes in maximum and mean LV SUV, right ventricular uptake, tumor stage, white blood cell count, and diabetes were associated with cardiac events in univariable analysis. In multivariable analysis, maximum LV SUV (cutoff > 12.84; hazard ratio [95% confidence interval] = 2.140 [1.140-4.016]; p = 0.018) was an independent predictor of cardiac events along with the mean heart dose (> 11.1 Gy; 3.646 [1.792-7.417]; p < 0.001) and tumor stage (IIIB; 1.986 [1.056-3.734]; p = 0.033). It remained predictive of cardiac events in those with higher mean heart dose but not in those with lower mean heart dose. CONCLUSIONS: Early FDG PET after CCRT for NSCLC could aid in predicting late cardiac events, especially in patients with higher mean heart dose.

Precise characterization of a solitary pulmonary nodule using tumor shadow disappearance rate-corrected F-18 FDG PET and enhanced CT.

ABSTRACT: We aimed to characterize solitary pulmonary nodule (SPN) using imaging parameters for F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) or enhanced CT corrected by tumor shadow disappearance rate (TDR) to reflect the tissue density.We enrolled 51 patients with an SPN who underwent PET/CT and chest CT with enhancement. The FDG uptake of SPN was evaluated using maximum standardized uptake value (SUVmax) on PET/CT. The mean Hounsfield unit (HU) for each SPN was evaluated over the region of interest on nonenhanced and enhanced CT images. The change in mean HU (HUpeak-pre) was quantified by subtracting the mean HU of the preenhanced CT from that of the post-enhanced CT. TDR was defined as the ratio of the tumor area, which disappears at a mediastinal window, to the tumor area of the lung window. We investigated which parameters (SUVmax or HUpeak-pre) could contribute to the characterization of SPN classified by TDR value and whether diagnostic performance could be improved using TDR-corrected imaging parameters.For SPN with higher tissue density (TDR <42%, n = 22), high value of SUVmax (≥3.1) was a significant factor to predict malignancy (P = .006). High value of HUpeak-pre (≥38) was a significant factor to characterize SPN (P = .002) with lower tissue density (TDR ≥42%, n = 29). The combined approach using TDR-corrected parameters had better predictive performance to characterize SPN than SUVmax only (P = .031).Applying imaging parameters such as SUVmax or HUpeak-pre in consideration of tissue density calculated with TDR could contribute to accurate characterization of SPN.

Clinically viable myocardial CCTA segmentation for measuring vessel-specific myocardial blood flow from dynamic PET/CCTA hybrid fusion.

BACKGROUND: Positron emission tomography (PET)-derived LV MBF quantification is usually measured in standard anatomical vascular territories potentially averaging flow from normally perfused tissue with those from areas with abnormal flow supply. Previously we reported on an image-based tool to noninvasively measure absolute myocardial blood flow at locations just below individual epicardial vessel to help guide revascularization. The aim of this work is to determine the robustness of vessel-specific flow measurements (MBFvs) extracted from the fusion of dynamic PET (dPET) with coronary computed tomography angiography (CCTA) myocardial segmentations, using flow measured from the fusion with CCTA manual segmentation as the reference standard. METHODS: Forty-three patients' 13NH3 dPET, CCTA image datasets were used to measure the agreement of the MBFvs profiles after the fusion of dPET data with three CCTA anatomical models: (1) a manual model, (2) a fully automated segmented model and (3) a corrected model, where major inaccuracies in the automated segmentation were briefly edited. Pairwise accuracy of the normality/abnormality agreement of flow values along differently extracted vessels was determined by comparing, on a point-by-point basis, each vessel's flow to corresponding vessels' normal limits using Dice coefficients (DC) as the metric. RESULTS: Of the 43 patients CCTA fully automated mask models, 27 patients' borders required manual correction before dPET/CCTA image fusion, but this editing process was brief (2-3 min) allowing a 100% success rate of extracting MBFvs in clinically acceptable times. In total, 124 vessels were analyzed after dPET fusion with the manual and corrected CCTA mask models yielding 2225 stress and 2122 rest flow values. Forty-seven vessels were analyzed after fusion with the fully automatic masks producing 840 stress and 825 rest flow samples. All DC coefficients computed globally or by territory were ≥ 0.93. No statistical differences were found in the normal/abnormal flow classifications between manual and corrected or manual and fully automated CCTA masks. CONCLUSION: Fully automated and manually corrected myocardial CCTA segmentation provides anatomical masks in clinically acceptable times for vessel-specific myocardial blood flow measurements using dynamic PET/CCTA image fusion which are not significantly different in flow accuracy and within clinically acceptable processing times compared to fully manually segmented CCTA myocardial masks.

Determination of [N-13]-ammonia extraction fraction in patients with coronary artery disease by calibration to invasive coronary and fractional flow reserve.

BACKGROUND: This study presents a new extraction fraction (EF) model based on physiological measures of invasive coronary flow reserve (CFR) and fractional flow reserve (FFR) in patients with suspected coronary artery disease (CAD) and normal index microcirculatory resistance (IMR). To ascertain the clinical relevance of the new EFs, flow measurements using the newly patient-determined EFs were compared to flow measurements using traditional animal-determined EFs. METHODS: 39 patients were retrospectively selected that included a total of 91 vascular territories with invasive coronary angiography physiological measures. [N-13]-ammonia dynamic rest/adenosine-stress PET imaging was conducted in all patients and absolute myocardial flow was estimated using four published compartmental models. The extraction fraction during hyperemic flow was iteratively estimated by maximizing the agreement between invasive CFR and FFR with the non-invasive analogs myocardial flow reserve (MFR) and relative flow reserve (RFR) at similar physiological states, respectively. RESULTS: Using the new patient-determined EFs, agreement between CFR vs MFR for Model 1 and 2 was moderate and poor for Model 3 and 4. All models showed moderate agreement for FFR vs RFR. When using published models of animal-determined EFs, agreement between CFR vs MFR remained moderate for Model 1 and 2, and poor for Model 3 and 4. Similarly, all models showed moderate agreement for FFR vs RFR using animal-determined EF values. None of the observed differences were statistically significant. CONCLUSIONS: Flow measurements using extraction fraction correction for [N-13]-ammonia based on calibration to invasive intracoronary angiography physiological measures in patients with CAD were not discordant from those reported in the literature. Either patient-determined or traditional animal-determined EF correction, when used with the appropriate flow model, yields moderate agreement with invasive measurements of coronary flow reserve and fractional flow reserve.

KSNM60 in Cardiology: Regrowth After a Long Pause.

The Korean Society of Nuclear Medicine (KSNM) is celebrating its 60th anniversary in honor of the nuclear medicine professionals who have dedicated their efforts towards research, academics, and the more comprehensive clinical applications and uses of nuclear imaging modalities. Nuclear cardiology in Korea was at its prime time in the 1990s, but its growth was interrupted by a long pause. Despite the academic and practical challenges, nuclear cardiology in Korea now meets the second leap, attributed to the growth in molecular imaging tailored for many non-coronary diseases and the genuine values of nuclear myocardial perfusion imaging. In this review, we describe the trends, achievements, challenges, and perspectives of nuclear cardiology throughout the 60-year history of the KSNM.

Change of Therapeutic Response Classification According to Recombinant Human Thyrotropin-Stimulated Thyroglobulin Measured at Different Time Points in Papillary Thyroid Carcinoma.

PURPOSE: We investigated whether response classification after total thyroidectomy and radioactive iodine (RAI) therapy could be affected by serum levels of recombinant human thyrotropin (rhTSH)-stimulated thyroglobulin (Tg) measured at different time points in a follow-up of patients with papillary thyroid carcinoma (PTC). METHODS: A total of 147 PTC patients underwent serum Tg measurement for response assessment 6 to 24 months after the first RAI therapy. Serum Tg levels were measured at 24 h (D1Tg) and 48-72 h (D2-3Tg) after the 2nd injection of rhTSH. Responses were classified into three categories based on serum Tg corresponding to the excellent response (ER-Tg), indeterminate response (IR-Tg), and biochemical incomplete response (BIR-Tg). The distribution pattern of response classification based on serum Tg at different time points (D1Tg vs. D2-3Tg) was compared. RESULTS: Serum D2-3Tg level was higher than D1Tg level (0.339 ng/mL vs. 0.239 ng/mL, P < 0.001). The distribution of response categories was not significantly different between D1Tg-based and D2-3Tg-based classification. However, 8 of 103 (7.8%) patients and 3 of 40 (7.5%) patients initially categorized as ER-Tg and IR-Tg based on D1Tg, respectively, were reclassified to IR-Tg and BIR-Tg based on D2-3Tg, respectively. The optimal cutoff values of D1Tg for the change of response categories were 0.557 ng/mL (from ER-Tg to IR-Tg) and 6.845 ng/mL (from IR-Tg to BIR-Tg). CONCLUSION: D1Tg measurement was sufficient to assess the therapeutic response in most patients with low level of D1Tg. Nevertheless, D2-3Tg measurement was still necessary in the patients with D1Tg higher than a certain level as response classification based on D2-3Tg could change.

Increasing Use of Cardiac PET/CT for Inflammatory and Infiltrative Heart Diseases in Korea.

Recently the incidence of inflammatory and infiltrative heart diseases is increasing in Korea. Cardiac PET/CT is a useful technology evaluating inflammatory and infiltrative heart diseases. This study analyzed trends in the use of cardiac PET/CT for evaluating inflammatory and infiltrative heart diseases in the Chonnam National University Hospital and Chonnam National University Hwasun Hospital. The general trend in Korea was also assessed based on the domestic nuclear medicine database. There was a common increasing trend in the number of F-18 FDG PET/CT for the evaluation of inflammatory and infiltrative heart diseases. A representative case with cardiac sarcoidosis is illustrated.

Dynamic cardiac PET motion correction using 3D normalized gradient fields in patients and phantom simulations.

This work expands on the implementation of three-dimensional (3D) normalized gradient fields to correct for whole-body motion and cardiac creep in [N-13]-ammonia patient studies and evaluates its accuracy using a dynamic phantom simulation model. METHODS: A full rigid-body algorithm was developed using 3D normalized gradient fields including a multi-resolution step and sampling off the voxel grid to reduce interpolation artifacts. Optimization was performed using a weighted similarity metric that accounts for opposing gradients between images of blood pool and perfused tissue without the need for segmentation. Forty-three retrospective dynamic [N-13]-ammonia PET/CT rest/adenosine-stress patient studies were motion corrected and the mean motion parameters plotted at each frame time point. Motion correction accuracy was assessed using a comprehensive dynamic XCAT simulation incorporating published physiologic parameters of the heart's trajectory following adenosine infusion as well as corrupted attenuation correction commonly observed in clinical studies. Accuracy of the algorithm was assessed objectively by comparing the errors between isosurfaces and centers of mass of the motion corrected XCAT simulations. RESULTS: In the patient studies, the overall mean cranial-to-caudal translation was 7 mm at stress over the duration of the adenosine infusion. Noninvasive clinical measures of relative flow reserve and myocardial flow reserve were highly correlated with their invasive analogues. Motion correction accuracy assessed with the XCAT simulations showed an error of <1 mm in late perfusion frames that broadened gradually to <3 mm in earlier frames containing blood pool. CONCLUSION: This work demonstrates that patients undergoing [N-13]-ammonia dynamic PET/CT exhibit a large cranial-to-caudal translation related to cardiac creep primarily at stress and to a lesser extent at rest, which can be accurately corrected by optimizing their 3D normalized gradient fields. Our approach provides a solution to the challenging condition where the image intensity and its gradients are opposed without the need for segmentation and remains robust in the presence of PET-CT mismatch.

Differences in diagnostic impact of dual-tracer PET/computed tomography according to the extrahepatic metastatic site in patients with hepatocellular carcinoma.

OBJECTIVES: We compared the diagnostic performance of C-11 acetate and F-18 fluorodeoxyglucose (FDG) PET/computed tomography (CT) for the detection of extrahepatic metastasis in patients with hepatocellular carcinoma (HCC) and evaluated whether the improvement in the diagnostic performance of dual tracer PET/CT differs by the metastatic site. METHODS: Fifty-eight patients who had extrahepatic metastasis on either C-11 acetate or F-18 FDG PET/CT were enrolled, and 193 metastatic lesions were analyzed in this retrospective study. The metastatic lesions were categorized based on six sites of involvement. According to each involved site, the tracer avidity of the metastatic lesions was compared using the maximum standardized uptake value (SUVmax). RESULTS: Bone was the most frequent categorized metastatic site (44.8%), followed by lymph node (39.7%), lung (34.5%), soft tissue (27.6%), adrenal gland (6.9%), and vascular category (3.4%). C-11 acetate PET/CT showed a higher SUVmax than F-18 FDG PET/CT in metastatic bone lesions (P = 0.003). F-18 FDG uptake was significantly higher than C-11 acetate uptake in metastatic lymph node lesions (P < 0.001). The detection rate of dual tracer PET/CT was significantly higher in the metastatic lung (93.6%) and soft tissue (100%) lesions. However, the diagnostic performance of dual tracer PET/CT was limited in the metastatic bone and lymph node lesions because each tracer's detection rate was very high (bone: 94.6% in C-11 acetate, lymph node: 94.1% in F-18 FDG). CONCLUSIONS: The tracer avidity of metastatic lesions differed according to the involved site. This difference affected the complementary role of dual tracer PET/CT in the diagnosis of extrahepatic metastases in patients with HCC.

Deceased vs. living donor kidney transplantation in prediction of acute renal allograft rejection using Tc-99m DTPA renal scan.

OBJECTIVES: No data are available regarding different prognostic values of Tc-99m diethylenetriaminepentaacetic acid (DTPA) renal scan in kidney transplantation (KT) recipients according to two distinct donor types: deceased donor KT (DDKT) and living donor KT (LDKT). We evaluated whether the interpretation of Tc-99m DTPA renal scan should be different by the donor type in predicting acute renal allograft rejection (AR). METHODS: One hundred and seven KT recipients (61 DDKT and 46 LDKT) were included in this study. Tc-99m DTPA renal scan was performed 1 week after KT. AR was defined as pathological evidence of renal allograft rejection during the first 6 months of KT. Clinical factors and Tc-99m DTPA renal scan findings were compared between patients with and without AR. To further analyze the effect of the donor type, they were again compared within DDKT and LDKT recipients, respectively. RESULTS: AR occurred in 15 patients (7 DDKT and 8 LDKT recipients). Among all patients, time to peak uptake (TTP) of the cortex (TTPCX) measured by Tc-99m DTPA renal scan was independently predictive of AR. Moreover, TTPKD (TTP of the whole transplanted kidney) and TTPCX were the only predictors of AR among DDKT recipients. The most accurate predictors were TTPCX and kidney area on renal scan for DDKT and LDKT, respectively. However, these parameters could not predict AR for the opposite donor type. CONCLUSIONS: AR could be effectively predicted by Tc-99m DTPA renal scan obtained at 1 week post-KT. Different parameters should be applied according to the donor type in the prediction of AR.