Richard L. Weinberg

ASNC imaging guidelines for nuclear cardiology procedures

The American Society of Nuclear Cardiology (ASNC) published a guideline for the reporting of myocardial perfusion imaging (MPI) in 2009. Over the last eight years there has been significant change in the breadth and depth of nuclear cardiology practice along with significant changes in the landscape of structured reporting. In consideration of this degree of change, it is appropriate that the guideline be updated and expanded to include a broader perspective of nuclear cardiology practice. At the same time, many things have not changed. This includes the fact that the report should provide a basic ‘‘bottom line’’ result to the referring physician and that this result must be clear and concise. This premise was expanded on by the American College of Radiology (ACR) with its development of a reporting and communication guideline with continued recent updates. All these documents emphasized the need for a defined structure containing standardized data elements to facilitate utilization of the complex data contained in an imaging report into the integrated healthcare of the patient through the electronic health record. The structured report is also an integral part to define quality in nuclear cardiology practices. There continues to be interest in the implementation of structured reporting as a mechanism to improve quality and outcomes and to reduce cost in fulfillment of the triple aim.

Incidence of and Risk Assessment for Adverse Cardiovascular Outcomes After Liver Transplantation: A Systematic Review

Background Cardiovascular events represent a major source of morbidity and mortality after liver transplantation and will likely increase given the aging population and nonalcoholic fatty liver disease as a leading indication for transplant. The optimal cardiovascular risk stratification approach in this evolving patient population remains unclear. The aims of this systematic review are to: (1) refine the definition, (2) characterize the incidence, and (3) identify risk factors for cardiovascular events post-liver transplantation. Additionally, we evaluated performance characteristics of different cardiac testing modalities. Methods MEDLINE via PubMed, EMBASE, Web of Science, and Scopus were searched for studies published between 2002 and 2016 (model of end-stage liver disease era). Two authors independently reviewed articles to select eligible studies and performed data abstraction. Results Twenty-nine studies representing 57 493 patients from 26 unique cohorts were included. Definitions of cardiovascular outcomes were highly inconsistent. Incidence rates were widely variable: 1% to 41% for outcomes of 6 months or shorter and 0% to 31% for outcomes longer than 6 months. Multivariate analyses demonstrated that older age and history of cardiac disease were the most consistent predictors of cardiovascular events posttransplant (significant in 8/23 and 7/22, studies, respectively). Predictive capacity of various cardiac imaging modalities was also discrepant. Conclusions The true incidence of cardiovascular outcomes post-liver transplant remains unknown in large part due to lack of consensus regarding outcome definition. Overall, poor data quality and gaps in knowledge limit the ability to clearly identify predictors of outcomes, but existing data support a more aggressive risk stratification protocol for patients of advanced age and/or with preexisting cardiac disease.

Optimization of temporal sampling for 82rubidium PET myocardial blood flow quantification

BackgroundSuboptimal temporal sampling of left ventricular (LV) blood pool and tissue time-activity curves (TACs) may introduce bias and increased variability in estimates of myocardial blood flow (MBF) and flow reserve (MFR) from dynamic PET myocardial perfusion images. We aimed to optimize temporal sampling for estimation of MBF and MFR.MethodsTwenty-four normal volunteers and 32 patients underwent dynamic stress/rest rubidium-82 chloride (82Rb) PET imaging. Fine temporal sampling was used to estimate the full width at half maximum (FWHM) of the LV blood pool TAC. Fourier analysis was used to determine the longest sampling interval, TS, as a function of FWHM, which preserved the information content of the blood phase. Dynamic datasets were reconstructed with frame durations varying from 2 to 20xa0seconds over the first 2xa0minutes for the blood phase and 30 to 120xa0seconds for the tissue phase. The LV blood pool and tissue TACs were sampled using regions of interest (ROI) and fit to a compartment model for quantification of MBF and MFR. The effects of temporal sampling on MBF and MFR were evaluated using clinical data and simulations.ResultsTS increased linearly with input function FWHM (Rxa0=xa00.93). Increasing the blood phase frame duration from 5 to 15 seconds resulted in MBF and MFR biases of 6-12% and increased variability of 14-24%. Frame durations <5xa0seconds had biases of less than 5% for both MBF and MFR values. Increasing the tissue phase frame durations from 30 to 120xa0seconds resulted in <5% biases.ConclusionsA two-phase framing of dynamic 82Rb PET images with frame durations of 5xa0seconds (blood phase) and 120xa0seconds (tissue phase) optimally samples the blood pool TAC for modern 3D PET systems.Spanish AbstractAntecedentesUna subóptima adquisición temporal del contenido sanguíneo del ventrículo izquierdo así como de las curvas de actividad tiempo (CAT) tisulares pueden introducir sesgos e incremento de la variabilidad en las estimaciones del flujo sanguíneo miocárdico (FSM) y la reserva de flujo (RFM) a partir de las imágenes dinámicas de perfusión miocárdica con PET. Nuestro objetivo fue optimizar la adquisición temporal para el cálculo de FSM y RFM.Métodos24 voluntarios normales y 32 pacientes se sometieron a un estudio PET con Cloruro de Rubidio-82 (82Rb) y protocolo estrés/reposo. Se utilizó una cuidadosa adquisición temporal para estimar el “full width at half máximum” (FWHM) de la CAT del contenido sanguíneo ventricular izquierdo. Se utilizó el análisis de Fourier para determinar el intervalo de adquisición más largo, IA, en función del FWHM, que preservó el contenido informativo de la fase sanguínea. Los conjuntos de datos dinámicos se reconstruyeron con duraciones de los cuadros que variaron de 2 a 20 segundos durante los primeros dos minutos para la fase sanguínea y de 30 a 120 segundos para la fase tisular. Las CAT tisular y del contenido sanguíneo ventricular se obtuvieron usando regiones de interés (ROI, por sus siglas en ingles) y se ajustaron a un modelo compartamental para la cuantificación de FSM y RFM. Los efectos de la adquisición temporal sobre el FSM y RFM se evaluaron utilizando datos clínicos y simulaciones.ResultadosEl IA aumentó linealmente con el aporte de la función FWHM (R=0.93). Aumentando la duración de los cuadros de la fase sanguínea de 5 a 15 segundos se incremento el sesgo del FSM y RFM en la fase de estrés en un 10% así como la variabilidad en el 20-25%. La duración de los cuadros menor a 5 segundos tuvo sesgos de menos del 5% para los valores de FSM y RFM. Aumentando la duración de los cuadros de la fase tisular de 30 a 120 segundos resultó en sesgos menores a 2%.ConclusionesRealizar las 2 fases del PET con 82Rb con duraciones de los cuadros de 5 segundos (fase sanguínea) y 120 segundos (fase tisular) es optimo para adquirir la CAT del contenido sanguíneo ventricular en los nuevos sistemas de PET 3D.Chinese Abstract背景在用动态的 PET 心肌灌注影像评估心肌血流量(MBF)和血流储备(MFR)时, 对左心室血池和组织时间活动曲线(TACs)的不恰当时间采样可能会引起结果的偏差和不稳定。本研究拟优化MBF和MFR评估的时间采样方案。方法24 名正常志愿者和32名患者采用动态静息/负荷铷-82氯化物(82Rb)PET成像,使用良好的时间采样来评估左心室血池TAC的半峰值处全幅宽度(FWHM)。采用傅里叶变换来确定最长采样间隔(Ts),Ts作为FWHM的一个函数反映血液相位的信息。随着帧持续时间的改变, 从超过前两分钟后的第2到20秒血液相位动态数据集被重建,以及从第30到120秒组织相位数据集被重建。对左心室血池和组织的TACs用兴趣区(ROI)进行采样,然后拟合成隔室模型,实现对MBF和MFR的量化。时间采样对MBF和MFR的影响使用临床数据和计算机模拟进行评估。结果Ts 随着输入函数FWHM呈线性增加(R=0.93)。增加血液相位帧持续时间5到15秒导致负荷MBF和MFR出现10%的偏差并且增加了20%-25%的不稳定性,而小于5秒的帧持续时间导致MBF和MFR值出现小于5%的偏差。增加组织相位帧持续时间30到120秒导致MBF和MFR值小于2%的偏差。结论一个两相位帧的动态(82Rb)PET图像且持续时间为5秒(血液相位)和120秒(组织相位),能够最佳地对现代3DPET系统的血池TAC采样。

Relationship of non-invasive quantification of myocardial blood flow to arrhythmic events in patients with implantable cardiac defibrillators

BackgroundIschemia contributes to arrhythmogenesis though its role is incompletely understood. Abnormal myocardial perfusion measured by PET imaging may predict ventricular arrhythmias (VAs) in a high-risk population.MethodsPatients with implantable cardiac defibrillators who had undergone rubidium-82 cardiac PET imaging were identified. Patients were stratified by median MBF and MFR values for analysis. The Cox proportional hazards model was used to assess the impact of myocardial perfusion on survival free of VT independent of critical covariates.ResultsA total of 159 patients (124 (78%) males, median age 65.9xa0years, IQR [56.76-72.63]) were followed for 1.43xa0years IQR [0.83-2.21]. VA occurred in 29 patients (23.7%). After adjustment for ejection fraction, age, and sex, impaired stress MBF was associated with an increased risk of VA (adjusted HR per ml/min/g 1.52, 95% CI (1.01-2.31), Pxa0=xa00.04). Summed rest and stress scores were not predictive of VA. Among patients with severe LV dysfunction, stress MBF remained an independent predictor of VA (adjusted HR per 1xa0ml/min/g HR 1.69, 95% CI (1.03-11.36), Pxa0=xa00.03), while residual EF, summed rest, and summed stress scores were not (Pxa0>xa00.05).ConclusionsImpaired stress myocardial blood flow was associated with less survival free of ventricular arrhythmias.

Safety of regadenoson stress testing in patients with pulmonary hypertension.

ObjectivesWe sought to determine the safety of regadenoson stress testing in patients with PH.BackgroundPH is increasingly recognized at more advanced ages. As many as one-third of patients with PH have coronary artery disease. Because of their physical limitations, patients with PH are unable to adequately exercise. Regadenoson can potentially have an adverse impact due to their tenuous hemodynamics. Current guidelines suggest performing a coronary angiography in patients with PH who have angina or multiple coronary risk factors.MethodsWe identified 67 consecutive patients with confirmed PH by catheterization (mean PAxa0>xa025xa0mmHg not due to left heart disease) who underwent MPI with regadenoson stress. Medical records were reviewed to determine hemodynamic and ECG response to regadenoson.ResultsNo serious events occurred. Common side effects related to regadenoson were observed, dyspnea being the most common (70.6%). No syncope occurred. Heart rate increased from 74.6xa0±xa014 to 96.3xa0±xa018.3xa0bpm, systolic blood pressure increased from 129.8xa0±xa020.9 to 131.8xa0±xa031xa0mmHg, and diastolic blood pressure decreased from 77.1xa0±xa011.4 to 72.9xa0±xa015.3xa0mmHg. There was no ventricular tachycardia, ventricular fibrillation, or second- or third-degree atrioventricular block.ConclusionRegadenoson stress MPI appears to be well tolerated and safe in patients with PH.

Blood pool and tissue phase patient motion effects on 82rubidium PET myocardial blood flow quantification

BackgroundPatient motion can lead to misalignment of left ventricular volumes of interest and subsequently inaccurate quantification of myocardial blood flow (MBF) and flow reserve (MFR) from dynamic PET myocardial perfusion images. We aimed to identify the prevalence of patient motion in both blood and tissue phases and analyze the effects of this motion on MBF and MFR estimates.MethodsWe selected 225 consecutive patients that underwent dynamic stress/rest rubidium-82 chloride (82Rb) PET imaging. Dynamic image series were iteratively reconstructed with 5- to 10-second frame durations over the first 2xa0minutes for the blood phase and 10 to 80xa0seconds for the tissue phase. Motion shifts were assessed by 3 physician readers from the dynamic series and analyzed for frequency, magnitude, time, and direction of motion. The effects of this motion isolated in time, direction, and magnitude on global and regional MBF and MFR estimates were evaluated. Flow estimates derived from the motion corrected images were used as the error references.ResultsMild to moderate motion (5-15xa0mm) was most prominent in the blood phase in 63% and 44% of the stress and rest studies, respectively. This motion was observed with frequencies of 75% in the septal and inferior directions for stress and 44% in the septal direction for rest. Images with blood phase isolated motion had mean global MBF and MFR errors of 2%-5%. Isolating blood phase motion in the inferior direction resulted in mean MBF and MFR errors of 29%-44% in the RCA territory. Flow errors due to tissue phase isolated motion were within 1%.ConclusionsPatient motion was most prevalent in the blood phase and MBF and MFR errors increased most substantially with motion in the inferior direction. Motion correction focused on these motions is needed to reduce MBF and MFR errors.

Reduced Myocardial Flow Reserve by Positron Emission Tomography Predicts Cardiovascular Events After Cardiac Transplantation

Background: We evaluated the diagnostic and prognostic value of quantification of myocardial flow reserve (MFR) with positron emission tomography (PET) in orthotopic heart transplant patients. Methods and Results: We retrospectively identified orthotopic heart transplant patients who underwent rubidium-82 cardiac PET imaging. The primary outcome was the composite of cardiovascular death, acute coronary syndrome, coronary revascularization, and heart failure hospitalization. Cox regression was used to evaluate the association of MFR with the primary outcome. The relationship of MFR and cardiac allograft vasculopathy severity in patients with angiography within 1 year of PET imaging was assessed using Spearman rank correlation and logistic regression. A total of 117 patients (median age, 60 years; 71% men) were identified. Twenty-one of 62 patients (34%) who underwent angiography before PET had cardiac allograft vasculopathy. The median time from orthotopic heart transplant to PET imaging was 6.4 years (median global MFR, 2.31). After a median of 1.4 years, 22 patients (19%) experienced the primary outcome. On an unadjusted basis, global MFR (hazard ratio, 0.22 per unit increase; 95% confidence interval, 0.09–0.50; P<0.001) and stress myocardial blood flow (hazard ratio, 0.48 per unit increase; 95% confidence interval, 0.29–0.79; P=0.004) were associated with the primary outcome. Decreased MFR independently predicted the primary outcome after adjustment for other variables. In 42 patients who underwent angiography within 12 months of PET, MFR and stress myocardial blood flow were associated with moderate–severe cardiac allograft vasculopathy (International Society of Heart and Lung Transplantation grade 2–3). Conclusions: MFR assessed by cardiac rubidium-82 PET imaging is a predictor of cardiovascular events after orthotopic heart transplant and is associated with cardiac allograft vasculopathy severity.

F-18 sodium fluoride PET/CT does not effectively image myocardial inflammation due to suspected cardiac sarcoidosis

BackgroundSarcoidosis is an inflammatory disorder of unknown etiology that can involve the heart. While effective in imaging cardiac sarcoidosis, F-18 fluorodeoxyglucose (FDG) PET/CT often shows non-specific myocardial uptake. F-18 sodium fluoride (NaF) has been used to image inflammation in coronary artery plaques and has low background myocardial uptake. Here, we evaluated whether F-18 NaF can image myocardial inflammation due to clinically suspected cardiac sarcoidosis.Patients and MethodsWe performed a single institution pilot study testing if F-18 NaF PET/CT can detect myocardial inflammation in patients with suspected cardiac sarcoidosis. Patients underwent cardiac PET/CT with F-18 FDG as part of their routine care and subsequently received an F-18 NaF PET/CT scan.ResultsThree patients underwent F-18 FDG and F-18 NaF imaging. In all patients, there was F-18 FDG uptake consistent with cardiac sarcoidosis. The F-18 NaF PET/CT scans showed no myocardial uptake.ConclusionsIn this small preliminary study, PET/CT scan using F-18 NaF does not appear to detect myocardial inflammation caused by suspected cardiac sarcoidosis.

Rescued diagnostic quality by motion correction of dynamic cardiac positron emission tomography (PET) perfusion images

Cardiac positron emission tomography (PET) imaging is widely utilized to measure myocardial blood flow and perfusion. Patient motion is a well-recognized cause of artifacts and techniques to correct for this have been developed, primarily for single photon imaging. Herein, we describe a case where gross patient motion during stress imaging resulted in non-diagnostic static images summed between 2 and 7 minutes. Respiratory gated images did not improve image quality (not shown). However, manual adjustment of dynamic images to correct for gross patient motion yielded diagnostic quality images and allowed detection of a proximal LAD stenosis. A 63-year-old man, with a medical history of tuberculous meningitis, normal pressure hydrocephalus status post ventriculoperitoneal shunt, and mild cognitive impairment, presented with exertional substernal chest pain. Normal plasma cardiac troponin ruled out acute myocardial infarction. Due to new T-wave inversions on electrocardiography, additional risk stratification was sought. The patient is obese and unable to exercise. Consequently, he underwent rest and regadenoson stress cardiac PET/CT imaging using rubidium82 as the perfusion tracer. Gross patient motion artifact rendered the study non-diagnostic by standard static reconstructions (Figure 1A). However, by manually adjusting the dynamic images acquired during this period (2 to 7 minutes) for patient motion, we resolved a completely reversible defect in the territory of proximal left anterior descending (LAD) coronary artery (Figure 1B). The patient underwent coronary angiography which confirmed proximal LAD disease and was percutaneously revascularized (Figure 2). This case highlights the utility of motion correction of the dynamic image series. The motion artifact in this case was a nearly 16 mm gross patient shift early during

Multiparametric assessment of left atrial remodeling using 18F-FDG PET/CT cardiac imaging: A pilot study

BackgroundLeft atrial (LA) remodeling is associated with structural, electric, and metabolic LA changes. Integrated evaluation of these features in vivo is lacking.MethodsPatients undergoing 18F-fluorodeoxyglucose (FDG) PET-CT during a hyperinsulinemic-euglycemic clamp were classified into sinus rhythm (SR), paroxysmal AF (PAF), and persistent AF (PerAF). The LA was semiautomatically segmented, and global FDG uptake was quantified using standardized uptake values (SUVmax and SUVmean) in gated, attenuation-corrected images and normalized to LA blood pool activity. Regression was used to relate FDG data to AF burden and critical patient factors. Continuous variables were compared using t-tests or Mann-Whitney tests.Results117 patients were included (76% men, age 66.4u2009±u200911.0, ejection fraction (EF) 25[22-35]%) including those with SR (nu2009=u200948), PAF (nu2009=u200955), and PerAF (nu2009=u200914). Patients with any AF had increased SUVmean (2.3[1.5-2.4] vs 2.0[1.5-2.5], Pu2009=u20090.006), SUVmax (4.4[2.8-6.7] vs 3.2[2.3-4.3], Pu2009<u20090.001), uptake coefficient of variation (CoV) 0.28[0.22-0.40] vs 0.25[0.2-0.33], Pu2009<u20090.001), and hypometabolic scar (32%[14%-53%] vs 16.5%[0%-38.5%], Pu2009=u20090.01). AF burden correlated with increased SUVmean, SUVmax, CoV, and scar independent of age, gender, EF, or LA size (Pu2009<u20090.03 for all).ConclusionsLA structure and metabolism can be assessed using FDG PET/CT. Greater AF burden correlates with the increased LA metabolism and scar.