Prediction of hepatocellular carcinoma in patients with Fontan-associated liver disease using gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid magnetic resonance imaging.

AIM: The unique feature of Fontan circulation is elevated central venous pressure, which causes Fontan-associated liver disease (FALD). FALD is associated with a high incidence of hepatocellular carcinoma (HCC). Performing biopsies in patients with FALD is difficult as a result of warfarinization; gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI), a noninvasive examination, is useful for characterizing liver disease and detecting HCC. However, few studies have reported the detailed features of Gd-EOB-DTPA MRI, and the association between these findings and prognosis. Thus, this study aimed to investigate the utility of Gd-EOB-DTPA MRI to predict HCC development in patients with FALD. METHODS: This study enrolled 44 patients with FALD (mean age 25 years) who underwent Gd-EOB-DTPA MRI. The hepatobiliary phase images were scored semiqualitatively, and the patients were classified into the mild (0-1 point) or severe group (≥2 points). The endpoint was HCC, and event-free survival was analyzed using Kaplan-Meier and log-rank tests. RESULTS: The severe group included 19 patients. During a mean follow-up of 58 months, HCC developed in six patients. Kaplan-Meier analysis revealed that patients in the severe group had a significantly poorer prognosis than those in the mild group (p = 0.0053). The Fibrosis-4 index and liver-to-spleen ratio of patients with HCC were moderate. CONCLUSIONS: Gd-EOB-DTPA MRI can be used to classify disease severity and predict the prognosis of patients with FALD.

Gated SPECT-Derived Myocardial Strain Estimated From Deep-Learning Image Translation Validated From N-13 Ammonia PET.

RATIONALE AND OBJECTIVES: This study investigated the use of deep learning-generated virtual positron emission tomography (PET)-like gated single-photon emission tomography (SPECTVP) for assessing myocardial strain, overcoming limitations of conventional SPECT. MATERIALS AND METHODS: SPECT-to-PET translation models for short-axis, horizontal, and vertical long-axis planes were trained using image pairs from the same patients in stress (720 image pairs from 18 patients) and resting states (920 image pairs from 23 patients). Patients without ejection-fraction changes during SPECT and PET were selected for training. We independently analyzed circumferential strains from short-axis-gated SPECT, PET, and model-generated SPECTVP images using a feature-tracking algorithm. Longitudinal strains were similarly measured from horizontal and vertical long-axis images. Intraclass correlation coefficients (ICCs) were calculated with two-way random single-measure SPECT and SPECTVP (PET). ICCs (95% confidence intervals) were defined as excellent (≥0.75), good (0.60-0.74), moderate (0.40-0.59), or poor (≤0.39). RESULTS: Moderate ICCs were observed for SPECT-derived stressed circumferential strains (0.56 [0.41-0.69]). Excellent ICCs were observed for SPECTVP-derived stressed circumferential strains (0.78 [0.68-0.85]). Excellent ICCs of stressed longitudinal strains from horizontal and vertical long axes, derived from SPECT and SPECTVP, were observed (0.83 [0.73-0.90], 0.91 [0.85-0.94]). CONCLUSION: Deep-learning SPECT-to-PET transformation improves circumferential strain measurement accuracy using standard-gated SPECT. Furthermore, the possibility of applying longitudinal strain measurements via both PET and SPECTVP was demonstrated. This study provides preliminary evidence that SPECTVP obtained from standard-gated SPECT with postprocessing potentially adds clinical value through PET-equivalent myocardial strain analysis without increasing the patient burden.

Glucose metabolic rate from four-dimensional [18F]FDG PET/CT to differentiate sarcoid lesions from malignant lesions.

OBJECTIVES: On 18F-Fludeoxyglucose (FDG) PET/CT, active sarcoid lesions are often difficult to differentiate from malignant lesions. We investigated the potential of the glucose metabolic rate (MRglc, mg/min/100 mL), a new quantification of glucose metabolic kinetics derived from direct reconstruction based on linear Patlak analysis, to distinguish between sarcoidosis and malignant lesions. MATERIALS AND METHODS: A total of 100 patients with cardiac sarcoidosis (CS) and 67 patients with cancer who underwent four-dimensional FDG PET/CT were enrolled. The lesions with a standardized uptake value (SUV) ≥ 2.7 on the standard scan were included as active lesions in the analysis. SUV and MRglc were derived using data acquired between 30 min and 50 min on four-dimensional FDG PET/CT. The mean value in the volume of interest (size 1.5 cm3) was measured. The diagnostic performance of sarcoidosis using MRglc and SUV was evaluated using receiver-operating-characteristic (ROC) analysis. RESULTS: A total of 90 sarcoidosis lesions from 44 CS patients (18 males, 63.4 ± 12.2 years) and 87 malignant lesions from 57 cancer-bearing patients (32 males, 65 ± 14 years) were analyzed. SUV and MRglc for sarcoid lesions were significantly lower than those for malignant lesions (SUV, 4.98 ± 2.00 vs 6.21 ± 2.14; MRglc, 2.52 ± 1.39 vs 3.68 ± 1.61; p < 0.01). ROC analysis indicated that the ability to discriminate sarcoid patients from those with malignancy yielded areas under the curves of 0.703 and 0.754, with sensitivities of 64% and 77% and specificities of 75% and 72% for SUV 5.025 and MRglc 2.855, respectively. CONCLUSION: MRglc was significantly lower in sarcoid lesions than malignant lesions, and improved sarcoid lesions identification over SUV alone. CLINICAL RELEVANCE STATEMENT: MRglc improves sarcoid lymph node identification over SUV alone and is expected to shorten the examination time by eliminating delayed scans. KEY POINTS: Active sarcoid lesions are sometimes associated with FDG accumulation and should be differentiated from malignant lesions. SUV and metabolic rate of glucose (MRglc) strongly positively correlated, and MRglc could differentiate sarcoid and malignant lesions. MRglc allows for accurate evaluation and staging of malignant lesions.

Right Ventricular Strain With 4-Dimensional Computed Tomography Identifies Pulmonary Hypertension in Adults With Repaired Tetralogy of Fallot.

BACKGROUND: This study evaluated right ventricular (RV) volume, strain, and morphology using cardiac 4-dimensional computed tomography (4D-CT) to detect pulmonary hypertension (PH) in adults with repaired tetralogy of Fallot (TOF) scheduled for transcatheter pulmonary valve implantation (TPVI). METHODS AND RESULTS: Using cardiac 4D-CT data, we calculated RV strain in 3 different geometries and RV outflow tract (RVOT) mass in 42 patients with repaired TOF. We compared RV strain and RVOT mass between patients with and without PH. Receiver operating characteristic (ROC) analysis was conducted to evaluate the diagnostic performance of these measurements for identifying PH. Four-chamber (4ch) strain was significantly smaller for patients with (n=10) than without (n=32) PH (8.8±1.7% vs. 11.1±2.4%, respectively; P<0.01), whereas RVOT mass was significantly larger in the PH group (12.5±3.5 vs. 9.2±3.2 cm2; P<0.01). ROC analysis of the diagnostic performance revealed that the respective sensitivity and specificity was 70% and 84% (area under the curve [AUC]=0.784) for 4ch strain of 8.8%; 80% and 69% (AUC=0.766) for RVOT mass of 10.7 cm2; and 80% and 81% (AUC=0.844) for a 4ch strain/RVOT mass ratio of 0.97. CONCLUSIONS: RVOT mass and 4ch strain obtained from cardiac 4D-CT may be helpful for identifying PH in patients with repaired TOF.

Prediction of cardiac allograft vasculopathy using splenic switch-off on myocardial PET.

BACKGROUND: Heart transplantation (HTx) is a definitive therapy for refractory heart failure. Cardiac allograft vasculopathy (CAV), characterized by diffuse arteriopathy involving the epicardial coronary arteries and microvasculature, is the major cause of death for patients with HTx. 13N-ammonia positron emission tomography (NH3-PET) can offer diagnostic and prognostic utility for CAV. The splenic switch-off (SSO) detected in NH3-PET is a hemodynamic indicator of favorable response to adenosine. We hypothesized that both CAV and SSO reflected a pathology that progresses in parallel with systemic vascular endothelial dysfunction. Therefore, we quantitatively evaluated splenic adenosine reactivity measured using NH3-PET as an index of endothelial function, and examined its predictability for CAV. METHODS: Forty-eight patients who underwent NH3-PET after HTx were analyzed. The spleen ratio was calculated as the mean standardized uptake value, measured by placing an ROI on the spleen, at stress divided by that at rest. SSO was defined by a cutoff determined using receiver operating characteristic (ROC) analysis for the spleen ratio. The endpoint was appearance or progression of CAV. Predictability of SSO was analyzed using Kaplan-Meier analysis. RESULTS: The endpoint occurred in 9 patients during a mean follow-up of 45 ±â€¯17 months. ROC curve analysis demonstrated a cutoff of 0.94 for spleen ratio. Patients without SSO displayed a significantly higher CAV rate than those with SSO (p = 0.022). CONCLUSIONS: SSO reflects the endothelial function of systemic blood vessels and was a predictor of CAV in patients with HTx.

Increased Diastolic Energy Loss Associated with Cardiac Events in Adults with Pulmonary Atresia Suffering from Intact Ventricular Septum.

PURPOSE: To assess right heart diastolic energy loss (EL) as a cardiac workload and evaluate its association with major cardiac events (MACE) in adult patients with pulmonary atresia with an intact ventricular septum (PAIVS). METHODS: We retrospectively enrolled and compared 30 consecutive adult patients (18 with PAIVS and 12 with pulmonary stenosis [PS] as controls) who underwent right ventricular (RV) outflow tract reconstruction and 4D flow MRI. EL, conventional parameters on MRI, and the severity of tricuspid regurgitation (TR) on echocardiography were assessed. We also evaluated the association between MACE including arrhythmias, heart failure, surgical intervention, and imaging parameters in adults with PAIVS. RESULTS: Patients with PAIVS were younger, had a higher diastolic EL/cardiac output (CO) ratio, and had a more significant TR than those with PS (controls). However, RV volume, ejection fraction (EF), and pulmonary regurgitation (PR) severity did not differ between the two groups. Higher RV end-diastolic pressure (EDP) and lower cardiac index (CI) correlated with the diastolic EL/CO in patients with PAIVS. Univariate logistic analysis demonstrated that older age and a higher diastolic EL/CO ratio were important factors for MACE in adults with PAIVS (P = 0.048, 0.049). CONCLUSION: A higher diastolic EL/CO ratio was associated with a higher RV EDP and lower CI. A high diastolic EL/CO ratio is also associated with MACE in adults with PAIVS. Even in adults with normal RV volume and EF, the right heart EL was elevated, suggesting an excessive right-sided cardiac workload that integrated both afterload and preload beyond the RV size in adult patients with PAIVS.

Risk Stratification Using Right Ventricular Longitudinal Strain Ratio Derived from 13N-Ammonia PET in Patients with Ischemic Heart Disease.

Purpose To investigate whether right ventricular (RV) myocardial strain ratio (RVMSR) assessed using nitrogen 13 ammonia (13N-NH3) PET can predict cardiovascular events in patients with ischemic heart disease (IHD). Materials and Methods This retrospective study included 480 consecutive patients (mean age, 66 years ± 12 [SD]; 334 males and 146 females) with IHD who underwent 13N-NH3 PET. RVMSR was defined as the ratio of RV strain during stress to that at rest. The primary end point was major adverse cardiac events (MACEs), defined as cardiac death or heart failure hospitalization. The ability of RVMSR to predict MACE was assessed using receiver operating characteristic (ROC) curve and Kaplan-Meier analyses. Cox proportional hazards regression analysis was used to calculate hazard ratios (HRs) with 95% CIs. Results ROC curve analysis identified a sensitivity and specificity of 84% and 82%, respectively, for predicting MACE from RVMSR. Patients with reduced RVMSR (<110.2) displayed a significantly higher rate of MACE than those with a preserved RVMSR (34 of 240 vs four of 240; P < .001). Cox proportional hazards regression analysis of imaging parameters, including myocardial flow reserve, indicated that RVMSR was an independent predictor of MACE (HR, 0.94 [95% CI: 0.92, 0.97]; P < .001). Conclusion RVMSR was an independent predictor of MACE and has potential to aid in the risk stratification of patients with IHD. Keywords: Right Ventricular Myocardial Strain Ratio, Myocardial Flow Reserve, Ischemic Heart Disease, 13N-Ammonia Positron Emission Tomography Supplemental material is available for this article. © RSNA, 2024.

Association Between Pretreatment 11C-Methionine Positron Emission Tomography Metrics, Histology, and Prognosis in 125 Newly Diagnosed Patients with Adult-Type Diffuse Glioma Based on the World Health Organization 2021Classification.

OBJECTIVE: To clarify the relationships between 11C-methionine (MET) positron emission tomography (PET) metrics and the histology, genetics, and prognosis of adult-type diffuse glioma (ADG) based on the World Health Organization (WHO) 2021 classification. METHODS: A total of 125 newly diagnosed patients with ADG were enrolled. We compared the maximum standardized uptake value (SUVmax), tumor-to-normal background ratio (TNR), metabolic tumor volume (MTV), and total lesion methionine uptake (TLMU) to the histology and genetics of the patients with ADG. We also evaluated the prognoses of the 93 surgically treated patients. RESULTS: The patients with isocitrate dehydrogenase wild ADG showed significantly higher MET-PET metrics (P < 0.05 for all parameters), significantly shorter overall survival and progression-free survival (P < 0.0001 for both) than those of the patients with isocitrate dehydrogenase mutant (IDHm) ADG. In the IDHm ADG group, the SUVmax, MTV, and TLMU values were significantly higher in patients with IDHm grade (G) 4 astrocytoma than patients with IDHm G2/3 astrocytoma (P < 0.05 for all), but not than patients with G2-3 oligodendroglioma. The progression-free survival was significantly shorter in the patients with G4 astrocytoma versus the patients with G2/3 astrocytoma and G3 oligodendroglioma (P < 0.05 for both). The SUVmax and TNR values were significantly higher in recurrent patients than nonrecurrent patients (P < 0.01 for both), but no significant differences were found in MTV or TLMU values. CONCLUSIONS: MET-PET metrics well reflect the histological subtype, WHO grade and prognosis of ADG based on the 2021 WHO classification, with the exception of oligodendroglial tumors. Volumetric parameters were not significantly associated with recurrence, unlike the SUVmax and TNR.

Simultaneous evaluation of brain metastasis and thoracic cancer using semiconductor 11C-methionine PET/CT imaging.

OBJECTIVE: To investigate the potential of whole-body digital 11C-methionine (MET) PET/CT imaging for simultaneous evaluation of thoracic cancer patients suspected of local recurrence (LR) after stereotactic radiosurgery (SRS) for brain metastasis. METHODS: A total of 45 lung or breast cancer patients suspected of LR after SRS were investigated using brain and whole-body MET-PET/CT scans. We compared the tumor-to-normal ratio (TNR) and maximum standardized uptake values (SUVmax) between patients with LR and radiation necrosis (RN) and performed receiver operating characteristic (ROC) analyses. We also investigated associations among extracranial recurrence, intracranial recurrence, primary site, and initial treatment type. RESULTS: A total of 44 LR and 14 RN lesions were analyzed. In the ROC analyses for differentiating LR from RN, TNR showed higher area under the curve (AUC) (0.82) than SUVmax (0.79), and the cutoff TNR value (2.12) was higher than current cutoff values of conventional PET systems. The whole-body scans detected extracranial recurrences in 31.1% of the patients. Recurrence rates were not significantly correlated with existence of intracranial recurrence or primary site, but patients who underwent non-surgical treatment (consisting of stage III/ IV patients according to the Union for International Cancer Control TNM classification or small-cell lung cancer patients) showed significantly higher recurrence than the surgically treated patients (68.8% vs. 10.3%, p = 0.0001). CONCLUSION: In digital MET-PET/CT imaging, TNR was a more useful parameter to differentiate LR from RN than SUVmax, and the cutoff value was higher than those with conventional PET systems. Additional whole-body scans could detect extracranial recurrence and would be especially useful for advanced thoracic cancer patients who underwent non-surgical treatment.

Prognostic value of right atrial strain in systemic sclerosis based on tissue tracking analysis using cine cardiac magnetic resonance imaging: a retrospective observational study.

Interstitial lung disease and cardiac involvement are common manifestations and prognostic factors of systemic sclerosis. However, it is unclear whether impaired right atrial function associated with interstitial lung disease in systemic sclerosis can be used as a prognostic factor in this patient population. Therefore, this study aimed to investigate the relationship between right atrial function, interstitial lung disease, and prognosis in patients with systemic sclerosis using tissue tracking analysis with cine cardiac magnetic resonance imaging. In this retrospective observational study, a total of 40 patients with systemic sclerosis were enrolled. Tissue tracking analysis was used to obtain time curves of right atrial strain. Reservoir (total strain), conduit (passive strain), and booster (active strain) pump function were calculated, and right atrial strain, interstitial lung disease, and clinical outcomes were examined. An adverse clinical event was defined as all-cause death. Overall, 23 patients had interstitial lung disease (58%). Six patients died during the follow-up (median, 44 months). The total skin score and right ventricular systolic pressure on echocardiography were higher in patients with an event than in those without an event (28 ± 16% vs. 13 ± 13%, P = 0.02; 46.3 ± 10.7 mmHg vs. 36.0 ± 8.5 mmHg, P = 0.01, respectively). Further, right atrial total strain and active strain were significantly lower in patients with an event than in those without an event (14.3 ± 11.3% vs. 25.8 ± 11.4%, P = 0.03; 3.48 ± 2.37 vs. 11.7 ± 6.78, P = 0.007, respectively). Multivariate analysis revealed that active strain was an independent predictor of all-cause death (hazard ratio 0.76, P = 0.029). Kaplan-Meier analysis revealed that the survival rate was significantly higher in patients with right atrial active strain levels above the cutoff 7.4 (P < 0.05). In systemic sclerosis, right atrial booster function was predictive of mortality. Hence, right atrial functional assessment may have incremental prognostic value for patients with systemic sclerosis, leading to better risk stratification.

4D flow MRI-derived energy loss and RV workload in adults with tetralogy of Fallot.

PURPOSE: To assess flow energy loss (EL) pattern inside the pulmonary circulation in adult patients with repaired tetralogy of Fallot (TOF), particularly in TOF with pulmonary stenosis (PS) and pulmonary regurgitation (PR), as a cardiac workload parameter and its relationship to symptoms and major adverse cardiovascular events (MACE). METHODS: Prospectively, 51 consecutive TOF adults after intracardiac repair, who underwent four-dimensional flow magnetic resonance imaging, were enrolled. All of them had significant PR (PR regurgitant fraction >25 %). TOF patients who had already reached the conventional criteria were excluded. We defined MACE as the following: 1) fatal arrhythmias, 2) sudden cardiac death, 3) surgical pulmonary valvular repair (PVR), 4) right heart failure (HF) needing diuretics and/or hospitalization within 2 years. RESULTS: A total of 15 patients had MACE; 1) 10 patients underwent PVR within 2 years, 2) 2 patients had ventricular tachycardia, and 3) 6 patients developed right HF (overlapped). Right ventricular (RV) end diastolic volume index (EDVI), RV end systolic volume index (ESVI), average EL/cardiac output (CO), and diastolic EL/CO in patients with MACE were greater than ones without MACE. On a multivariate logistic analysis, the diastolic EL/CO ratio and RVEDVI had the highest odds with MACE in all TOF (odds ratio, 40.7 and 1.15. 95%CI, 1.83-905 and 1.02-13.0; p-value, 0.02 and 0.03). In sub-analysis within 29 patients with moderate PS with PR, and 10 patients with MACE showed higher diastolic EL/CO. Average and diastolic EL/CO negatively correlated with RV ejection fraction (EF) in this sub-analysis. CONCLUSIONS: High EL, particularly, high diastolic EL/CO, were the important factors for MACE in adult TOF. Higher diastolic EL/CO was also related to lower RV EF and deteriorated RV function in adult TOF with PS and PR. Right-sided EL can be a sensitive marker of excessive cardiac workload which integrates both afterload and preload in adult patients with TOF, beyond the RV size.

13N-ammonia positron emission tomography for diagnosis and monitoring of ischemia without obstructive coronary artery disease.

BACKGROUND: Ischemia with no obstructive coronary arteries (INOCA), a chronic disorder with a poor prognosis, remains challenging to diagnose. 13N-ammonia positron emission tomography (13NH3 PET), which can quantify microcirculation, is its most reliable detection method. We aimed to investigate the differences in 13NH3 PET findings between INOCA and coronary artery disease (CAD). METHODS: Overall, consecutive 433 patients with known or suspected CAD underwent adenosine-stress 13NH3 PET. Based on the European Society of Cardiology guidelines, INOCA was defined as typical angina without coronary stenosis (INOCA n = 45, CAD n = 293, no CAD n = 95). Papillary muscle ischemia (PMI) and global myocardial flow reserve (MFR) were examined as microvascular injuries using 13NH3 PET. RESULTS: PMI was observed significantly more frequently in patients with INOCA than in those with CAD (40.0% vs. 11.6%, respectively; p = 0.02). Global MFR (1.84 ± 0.54 vs. 2.08 ± 0.66, respectively; p < 0.0001) and reactive hyperemia index were significantly lower in patients with INOCA than in those with CAD. Forty-five major adverse cardiac events (MACE) were recorded in a median follow-up time of 827 days. Kaplan-Meier analysis revealed that the survival rate worsened in patients with INOCA and PMI (log-rank test, p = 0.001). In the Cox proportional hazards model, PMI was an independent predictive factor for MACE (odds ratio, 4.16; 95% confidence interval, 2.13-8.15; p < 0.0001). CONCLUSIONS: PMI presence and decreased MFR were 13NH3 PET findings characteristic of INOCA. 13NH3 PET can be used to monitor the treatment course.

Patlak Reconstruction Using Dynamic 18 F-FDG PET Imaging for Evaluation of Malignant Liver Tumors : A Comparison of HCC, ICC, and Metastatic Liver Tumors.

PURPOSE OF THE REPORT: The aim of this study was to explore the different patterns of dynamic whole-body (D-WB) FDG PET/CT parameters among liver malignancy types as potential diagnostic clues and investigate the association between static and dynamic PET/CT parameters for each tumor histology. PATIENTS AND METHODS: Seventy-one patients with intrahepatic cholangiocarcinoma (ICC), metastatic liver tumor (MLT), or hepatocellular carcinoma (HCC) who underwent D-WB and static dual-time-point FDG PET/CT were enrolled. We obtained Pearson correlation coefficients between the metabolic rate of FDG (MR FDG ; mg/min/ 100ml) or distribution volume of free FDG (DV FDG , %) and static PET/CT parameters. We compared MR FDG and DV FDG values by tumor type and performed receiver operating characteristic analyses for MR FDG and static images. RESULTS: A total of 12 ICC, 116 MLT, and 36 HCC lesions were analyzed. MR FDG and DV FDG showed excellent correlation with early (SUV e ) and delayed SUV max (SUV d ) ( r = 0.71~0.97), but DV FDG in the HCC lesions did not ( r = 0.62 and 0.69 for SUV e and SUV d , respectively) ( P < 0.001 for all). HCC lesions showed significantly lower MR FDG (2.43 ± 1.98) and DV FDG (139.95 ± 62.58) than ICC (5.02 ± 3.56, 207.06 ± 97.13) and MLT lesions (4.51 ± 2.47, 180.13 ± 75.58) ( P < 0.01 for all). The optimal MR FDG could differentiate HCC from ICC and MLT with areas under the curve of 0.84 and 0.80, respectively. Metastatic liver tumor lesions showed the widest distribution of MR FDG and DV FDG values but with no significant difference among most primary sites. CONCLUSIONS: MR FDG was strongly correlated with SUV max in the 3 malignancies and showed utility for differentiating HCC from ICC and MLT. Each tumor type has a different glucose metabolism, and D-WB FDG PET/CT imaging has the potential to visualize those differences.

Deep learning approach using SPECT-to-PET translation for attenuation correction in CT-less myocardial perfusion SPECT imaging.

OBJECTIVE: Deep learning approaches have attracted attention for improving the scoring accuracy in computed tomography-less single photon emission computed tomography (SPECT). In this study, we proposed a novel deep learning approach referring to positron emission tomography (PET). The aims of this study were to analyze the agreement of representative voxel values and perfusion scores of SPECT-to-PET translation model-generated SPECT (SPECTSPT) against PET in 17 segments according to the American Heart Association (AHA). METHODS: This retrospective study evaluated the patient-to-patient stress, resting SPECT, and PET datasets of 71 patients. The SPECTSPT generation model was trained (stress: 979 image pairs, rest: 987 image pairs) and validated (stress: 421 image pairs, rest: 425 image pairs) using 31 cases of SPECT and PET image pairs using an image-to-image translation network. Forty of 71 cases of left ventricular base-to-apex short-axis images were translated to SPECTSPT in the stress and resting state (stress: 1830 images, rest: 1856 images). Representative voxel values of SPECT and SPECTSPT in the 17 AHA segments against PET were compared. The stress, resting, and difference scores of 40 cases of SPECT and SPECTSPT were also compared in each of the 17 segments. RESULTS: For AHA 17-segment-wise analysis, stressed SPECT but not SPECTSPT voxel values showed significant error from PET at basal anterior regions (segments #1, #6), and at mid inferoseptal regions (segments #8, #9, and #10). SPECT, but not SPECTSPT, voxel values at resting state showed significant error at basal anterior regions (segments #1, #2, and #6), and at mid inferior regions (segments #8, #9, and #11). Significant SPECT overscoring was observed against PET in basal-to-apical inferior regions (segments #4, #10, and #15) during stress. No significant overscoring was observed in SPECTSPT at stress, and only moderate over and underscoring in the basal inferior region (segment #4) was found in the resting and difference states. CONCLUSIONS: Our PET-supervised deep learning model is a new approach to correct well-known inferior wall attenuation in SPECT myocardial perfusion imaging. As standalone SPECT systems are used worldwide, the SPECTSPT generation model may be applied as a low-cost and practical clinical tool that provides powerful auxiliary information for the diagnosis of myocardial blood flow.

Optimization of Intraventricular Radioactive Concentration for 13N ammonia PET with Time-of-Flight Scanner: Simplified Phantom Study with Noise Equivalent Count Rate Analysis.

Background: Myocardial blood flow quantification (MBF) is one of the distinctive features for cardiac positron emission tomography. The MBF calculation is mostly obtained by estimating the input function from the time activity curve in dynamic scan. However, there is a substantial risk of count-loss because the high radioactivity pass through the left ventricular (LV) cavity within a short period. We aimed to determine the optimal intraventricular activity using the noise equivalent count rate (NECR) analysis with simplified phantom model. Methods: Positron emission tomography computed tomography scanner with LYSO crystal and time of flight was used for phantom study. 150 MBq/mL of 13N was filled in 10 mL of syringe, placed in neck phantom to imitate end-systolic small LV. 3D list-mode acquisition was repeatedly performed along radioactive decay. Net true and random count rate were calculated and compared to the theoretical activity in the syringe. NECR curve analysis was used to determine the optimal radioactive concentration. Result: The attenuation curves showed good correlation to the theoretical activity between 20 to 370, and 370 to 740 MBq (r2=1.0 ± 0.0001, p<0.0001; r2=0.99 ± 0.0001, p<0.0001 for 20 to 370, and 370 to 740, respectively), while did not over 740 MBq (p=0.62). NECR analysis revealed that the peak rate was at 2.9 Mcps, there at the true counts were significantly suppressed. The optimal radioactive concentration was determined as 36 MBq/mL. Conclusion: Simulative analysis for high-dose of 13N using the phantom imitating small LV confirmed that the risk of count-loss was increased. The result can be useful information in assessing the feasibility of MBF quantification in clinical routine.

Myocardial Strain Derived from 13N-ammonia Positron Emission Tomography: Detection of Ischemia-Related Wall Motion Abnormality.

Background: Due to the limitation of spatial resolution, cardiac nuclear medicine images have not been applied to feature-tracking method to automatic extraction of myocardial contours. We have successfully applied the feature-tracking method to high-resolution cine 13N-ammonia positron emission tomography (PET) images to calculate the regional myocardial strains. Here, we investigate the potential of 13N-ammonia PET-derived strain to detect ischemia-related wall motion abnormality. Methods: Data of adenosine-stress/rest 13N-ammonia PET for 95 coronary artery disease patients was retrospectively analyzed. Using an original algorithm dedicated to 13N-ammonia PET, the longitudinal strain (LS) corresponding to the three main coronary artery territories [right coronary artery (RCA), left anterior descending artery (LAD), and left circumflex coronary artery (LCX)] was calculated from semi-automatic endocardial contours extraction on cine 13N-ammonia PET images of the left ventricular long-axis. The presence of ischemia in three main territories was determined from rest and stress-perfusion images. Results: In all three coronary territories, LS at stress was significantly smaller at rest in the ischemic region RCA: -19.2±8.0% vs. -22.7±6.1%, LAD: -19.0±6.9% vs. -24.4±6.4%, LCX: -20.5%±7.6% vs. -22.6±6.9%). In contrast, in the non-ischemic region, there was no significant difference between the LS at stress and at rest. Receiver-operating-characteristic analysis revealed that using the optimal cutoff of the LS ratio of stress to rest, ischemia could be diagnosed with area under the curve of 0.82 in the RCA, 0.86 in the LAD, and 0.69 in the LCX. Conclusions: Myocardial strain derived from endocardial feature-tracking of 13N-ammonia PET cine imaging is reduced in the ischemia induced by adenosine-stress. The LS ratio of stress to rest may detect wall motion abnormality related to ischemia.

Coronary artery bypass grafting transiently improves myocardial flow reserve in patients with impaired left ventricular function.

BACKGROUND: Myocardial flow reserve (MFR) derived from 13N-ammonia positron emission tomography is an index used to evaluate ischemic cardiomyopathy and predict the prognosis of patients with coronary artery disease (CAD). This study aimed to evaluate the short-term changes in MFR in patients who underwent coronary artery bypass grafting (CABG). In addition, as a reference, we showed the changes in MFR in the percutaneous coronary intervention (PCI) and optimal medical therapy (OMT) patient groups. METHODS: To determine the short-term effects of CABG in CAD with left ventricular dysfunction, myocardial blood flow (MBF) and MFR were measured before and after CABG. Additionally, we showed changes in MBF and MFR of the PCI and OMT patient groups during treatment. RESULTS: We observed that resting MBF did not significantly increase from baseline to post-CABG (0.84 ± 0.32 vs. 0.83 ± 0.23, P = 0.958); however, stress MBF increased significantly from baseline to post-CABG (1.23 ± 0.64 vs. 1.49 ± 0.42, P < 0.001). The global MFR increased significantly from baseline to post-CABG (1.49 ± 0.42 mL/g/min vs. 1.91 ± 0.51 mL/g/min, P < 0.001). Additionally, stress and resting ejection fraction (EF) significantly increased (stress EF: 42 ± 18.7% vs. 50.9 ± 18%, P = 0.005; resting EF: 45.8 ± 19.5% vs. 52.1 ± 19.4%, P = 0.031). CONCLUSIONS: This study demonstrated that CABG significantly improved MFR in a short period of time with left ventricular dysfunction. These findings suggest that epicardial coronary artery patency restores myocardial microcirculatory dysfunction in the short term.