Robert A DeKemp

Robert A DeKemp
University of Ottawa · University of Ottawa Heart Institute

PhD

About

441
Publications
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Publications

Publications (441)
Article
Full-text available
Background The etiology of sarcoidosis is still unknown and is likely related to a genetic susceptibility to unidentified environmental trigger(s). Our group and others have extensively described a specific phenotype of primarily Caucasian patients with clinically manifest cardiac sarcoidosis (CS). In this study we sought to explore whether smoking...
Article
Full-text available
Purpose To estimate the interobserver agreement of the Carimas software package (SP) on global, regional, and segmental levels for the most widely used myocardial perfusion PET tracer—Rb-82. Materials and methods Rest and stress Rb-82 PET scans of 48 patients with suspected or known coronary artery disease (CAD) were analyzed in four centers using...
Article
Background Alterations in atrial metabolism may play a role in the perpetuation of atrial fibrillation (AF). This study sought to compare 18F-fluorodeoxyglucose (FDG) uptake on PET, in patients with LV dysfunction versus those without AF.Methods Seventy-two patients who underwent myocardial viability assessment were evaluated. AF patients (36) had...
Article
Full-text available
Background Rubidium-82 positron emission tomography (⁸²Rb PET) MPI is considered a noninvasive reference standard for the assessment of myocardial perfusion in coronary artery disease (CAD) patients. Our main goal was to compare the diagnostic performance of static rest/ vasodilator stress CT myocardial perfusion imaging (CT-MPI) to stress/ rest ⁸²...
Article
Aims: This study aimed to evaluate markers of systemic as well as imaging markers of inflammation in the ascending aorta, bone marrow, and spleen measured by 18F-FDG PET/CT, in HIV+ patients at baseline and following therapy with rosuvastatin. Methods and results: Of the 35 HIV+ patients enrolled, 17 were randomized to treatment with 10 mg/day r...
Article
BACKGROUND The role of revascularization in patients with ischemic heart failure is still controversial and novel strategies are needed to identify patients in whom revascularization may be of benefit. We set out to analyze whether viability and scar correlate with biomarkers associated with increased myocardial wall stress, cardiac remodeling, myo...
Article
BACKGROUND Sympathetic denervation has been shown to predict the risk of sudden cardiac death in ischemic cardiomyopathy (ICM) heart failure patients with implanted cardiac defibrillators. The previous PAREPET trial (JACC 2014;63(2):141) used the PET tracer hydroxyephedrine (HED) which is a false neurotransmitter analog of norepinephrine. This esta...
Article
BACKGROUND Psoriatic arthritis (PsA) and cutaneous psoriasis (PsO) are linked with an increased risk of adverse cardiovascular events. We hypothesized that central vascular inflammation on F-18-fluorodeoxyglucose (FDG) positron emission tomography (PET) in the ascending aorta would improve in these patients following therapy with biologic agents co...
Article
Full-text available
Purpose To cross-compare three software packages (SPs)—Carimas, FlowQuant, and PMOD—to quantify myocardial perfusion at global, regional, and segmental levels. Materials and Methods Stress N-13 ammonia PET scans of 48 patients with HCM were analyzed in three centers using Carimas, FlowQuant, and PMOD. Values agreed if they had an ICC > 0.75 and a...
Article
Background: In ischemic cardiomyopathy patients, cardiac sympathetic nervous system dysfunction is a predictor of sudden cardiac arrest (SCA). This study compared abnormal innervation and perfusion measured by [11C]meta-hydroxyephedrine (HED) vs [13N]ammonia (NH3), conventional uptake vs parametric tracer analysis, and their SCA risk discriminatio...
Article
Background Current risk assessment approaches fail to identify the majority of patients at risk of sudden cardiac arrest (SCA). Noninvasive imaging of the cardiac sympathetic nervous system using single-photon emission computed tomography and positron emission tomography offers the potential for refining SCA risk assessment. While various [ ¹¹ C]me...
Article
Background Survivors of community-acquired pneumonia (CAP) are at increased risk of cardiovascular disease, cognitive and functional decline, and death but the mechanisms remain unknown. Research Question Do CAP survivors have evidence of increased inflammatory activity in their lung parenchyma on ¹⁸FDG-PET/CT after clinical resolution of infectio...
Article
Background Little is known about the sequelae of chronic sympathetic nervous system (SNS) activation in patients with pulmonary arterial hypertension (PAH) and right heart failure (RHF). We aimed to, (1) validate the use of [11C]-meta-hydroxyephedrine (HED) for assessing right ventricular (RV) SNS integrity, and (2) determine the effects of β-recep...
Article
Background Myocardial flow reserve (MFR) measurement provides incremental diagnostic and prognostic information. The objective of the current study was to investigate the application of a simplified model for the estimation of MFR using only the stress/rest myocardial activity ratio (MAR) in patients undergoing rest–stress cardiac PET MPI.Methods a...
Article
Objectives The aim of this study was to investigate the regional distribution of novel ¹⁸F-labeled positron emission tomographic (PET) tracer flubrobenguane (FBBG) (whose longer half-life could enable more widespread use) to assess myocardial presynaptic sympathetic nerve function in humans in comparison to [¹¹C]meta-hydroxyephedrine (HED). Backgr...
Article
Introduction: Cardiovascular disease (CVD) is a major source of morbidity and mortality in HIV+ patients, which is thought to be in part due to a state of persistent systemic inflammation that results in accelerated atherosclerosis. Hypothesis: We hypothesized that inflammation, as measured by 18F-fluorodeoxyglucose (18F-FDG) uptake measured by 18F...
Conference Paper
Introduction: Cardiovascular disease (CVD) is a major source of morbidity and mortality in HIV+ patients, which is thought to be in part due to a state of persistent systemic inflammation that results in accelerated atherosclerosis. Hypothesis: We hypothesized that inflammation, as measured by 18F-fluorodeoxyglucose (18F-FDG) uptake measured by 18...
Article
Full-text available
Cardiac sarcoidosis (CS) is an increasingly recognized condition, but cardiac magnetic resonance (CMR) image interpretation in these patients may be challenging as findings are often non-specific. The main objective of this study was to investigate the inter-reader agreement for the overall interpretation of CMR for the diagnosis of CS in an experi...
Article
Background: Myocardial blood flow (MBF) quantification by Rubidium-82 positron emission tomography (PET) has shown promise for cardiac allograft vasculopathy (CAV) surveillance and risk stratification post heart transplantation. The objective was to determine the prognostic value of serial PET performed early post transplantation. Methods and res...
Conference Paper
Full-text available
Background: Aging is associated with structural and functional deteriorations of the heart. Mitochondrial dysfunction (MD) promotes oxidative stress, and is a common feature of aging, metabolic disorders and cardiomyopathy. The 18 kDa mitochondrial translocator protein (TSPO) is expressed in the outer mitochondrial membrane. Several TSPO-targeted P...
Article
Full-text available
Purpose of review: PET scanner design and performance evaluation has been driven historically by the imaging requirements for whole-body imaging in oncology. Cardiac PET imaging for accurate quantification of myocardial blood flow (MBF) using short-lived tracers such as rubidium-82 imposes additional requirements for wide dynamic range and high co...
Article
Full-text available
Purpose Cardiac sympathetic nervous system (SNS) dysfunction is associated with poor prognosis in chronic heart failure patients. This study characterized the reproducibility and repeatability of [¹¹C]meta-hydroxyephedrine (HED) positron emission tomography (PET) quantification of cardiac SNS innervation, regional denervation, and myocardial blood...
Article
Full-text available
Background Sarcoidosis is a condition of unknown etiology. A number of occupational, recreational and environmental exposures have been associated with the development of extra-cardiac sarcoidosis. Patients with clinically manifest cardiac sarcoidosis (CS) have a distinct clinical phenotype. We sought to explore the exposures associated with clinic...
Article
Objectives This study sought to develop a clinical model that identifies a lower-risk population for coronary artery disease that could benefit from stress-first myocardial perfusion imaging (MPI) protocols and that can be used at point of care to risk stratify patients. Background There is an increasing interest in stress-first and stress-only im...
Article
Full-text available
Background The objective of this study was to compare the hyperemic myocardial blood flow (MBF) and myocardial flow reserve (MFR) obtained with dobutamine to those of dipyridamole in patients referred for myocardial perfusion imaging (MPI) using 82Rb positron emission tomography.Methods One hundred and fifty-six patients who underwent a 82Rb PET MP...
Article
Full-text available
Introduction: Strontium-82/Rubidium-82 (82Sr/82Rb) generators are used widely for positron emission tomography (PET) imaging of myocardial perfusion. In this study, the 82Rb isotope yield and production efficiency of two FDA-approved 82Sr/82Rb generators were compared. Methods: N = 515 sequential daily quality assurance (QA) reports from 9 Cardi...
Article
Background Reduced left ventricular (LV) function is associated with increased myocardial oxygen consumption rate (MVO2) and altered sympathetic activity, the role of which is not well described in right ventricular (RV) dysfunction.Methods and results33 patients with left heart failure were assessed for RV function/size using echocardiography. Pos...
Article
Introduction: Three-dimensional (3D) data acquisition is now standard on PET/computed tomography scanners. The aim of this study was to evaluate the repeatability of myocardial blood flow (MBF) estimation with rubidium-82 (Rb) 3D PET and to validate regional MBF measurements by comparison with two-dimensional (2D) PET. Patients and methods: Fift...
Article
Background Regional cardiac sympathetic denervation is predictive of sudden cardiac arrest in patients with ischemic cardiomyopathy. The reproducibility of denervation scores between automated software programs has not been evaluated. This study seeks to (1) compare the inter-rater reliability of regional denervation measurements using two analysis...
Article
Purpose: Motion compensated positron emission tomography (PET) imaging requires detecting and monitoring of patient body motion. We developed a semiautomatic list-mode method to track the three-dimensional (3D) motion of fiducial positron-emitting markers during PET imaging. Methods: A previously developed motion tracking method using positron-e...
Article
Background Qualification and interpretation standards are essential for establishing 99mTc-SPECT MPI accuracy vs. alternative modalities.Methods Rest–stress 99mTc-SPECT phantom scans were acquired on 35 cameras. LV defects were quantified with summed stress (SSS) and difference scores (SDS) at 2 core labs. SDS ≥ 2 in the right coronary artery (RCA)...
Article
Coronary artery disease has been the leading cause of death since the 1960s, which has motivated the research and development of myocardial perfusion imaging (MPI) agents for early diagnosis and to guide treatment. MPI with SPECT has been the clinical workhorse for MPI, but over the past two decades PET MPI is experiencing growth due to enhanced im...
Article
Molecular imaging with positron emission tomography (PET) and single-photon emission computed tomography (SPECT) serves numerous applications in clinical cardiology and research. Similar to other medical imaging technologies, this area has undergone and continues to experience rapid changes resulting from technological and medical advances. These h...
Article
Background Measurement of myocardial blood flow (MBF) with single photon emission computed tomography (SPECT) is feasible using cardiac cameras with solid-state detectors. SPECT MBF has been shown to be accurate when compared with positron emission tomography MBF measured in the same patients. However, the value of a test result applied to an indiv...
Article
Purpose: A data-driven motion tracking system was developed for respiratory gating in PET/CT studies. The positron emission tracking system (PeTrack) estimates the position of a low-activity fiducial marker placed on the patient during imaging. The aim of this study is to compare the performance of PeTrack against that of the Real-Time Position Ma...
Article
Background We previously demonstrated high diagnostic accuracy of Rubidium-82 positron emission tomography (PET) myocardial blood flow (MBF) quantification for CAV. The purpose of this study was to validate multiparametric PET detection of CAV by combined rate-pressure-product-corrected myocardial flow reserve (cMFR), stress MBF, and coronary vascu...
Article
At time of initial publication, the USAN Council had assigned the generic name for LMI1195 as Flurobenguan. However, the Council has since changed and finalized this compound name as Flubrobenguane which is recommended as the generic name to be used in the future.
Article
Background Rb-82 positron emission tomography (PET) myocardial perfusion imaging (MPI) is a robust tool for the evaluation of coronary artery disease (CAD). However, gastric uptake and spillover can be seen in 10% of Rb-82 PET MPI studies, commonly affecting the inferior wall, and can preclude the accurate identification of myocardial ischemia. We...
Article
Background: The induction of matrix metalloproteinases (MMPs) and reduction in tissue inhibitors of MMPs (TIMPs) plays a role in ischemia/reperfusion (I/R) injury post-myocardial infarction (MI) and subsequent left ventricular remodeling. We developed a hybrid dual isotope single-photon emission computed tomography/computed tomography approach for...
Article
Approximately 5% of patients with sarcoidosis have clinically manifest cardiac involvement. Clinical features of Cardiac Sarcoidosis are dependent on the location, extent, and activity of the disease. First line therapy is usually with prednisone and this is recommended based on clinician experience, expert opinion and small observational cohorts....
Article
Rubidium-82 is the most well-established cardiac PET flow tracer with over 6 decades of literature. Due to its robust supply, short physical half-life, ease of use, low radiation dose and favorable kinetics it can deliver comprehensive clinical information with minimal risk and maximum convenience to patients and clinical staff. Optimized ⁸²Rb prot...
Article
Abnormalities in the cardiac sympathetic nervous system have been documented in various heart diseases and have been directly implicated in their pathogenesis and disease progression. Noninvasive techniques using single-photon-emitting radiotracers for planar scintigraphy and single-photon emission computed tomography, and positron-emitting tracers...
Conference Paper
Image reconstruction for positron emission tomography (PET) can be challenging and the resulting image typically has high noise. The kernel-based reconstruction method [1], incorporates prior anatomic information in the reconstruction algorithm to reduce noise while preserving resolution. Prior information is incorporated in the reconstruction algo...
Article
Aims : Diabetes mellitus (DM) affects the macro- and microvasculature, leading to impairment in coronary vascular reactivity. Microvascular dysfunction is more prevalent in females compared to males, leading to increased cardiovascular risk in women. The purpose of this study was to quantify the association between diabetes and female sex on myoca...
Conference Paper
Background: Cardiac sympathetic nervous system dysfunction is a predictor of sudden cardiac arrest in heart failure patients with ischemic cardiomyopathy. Qualitative markers of cardiac PET tracer uptake have typically been used to assess cardiac function in these patients, however there may be added value in quantification for subsequent clinical...
Conference Paper
Introduction: In patients with diabetes mellitus (DM) and coronary artery disease (CAD), revascularization with coronary artery bypass grafting (CABG) has been shown to decrease the number of adverse events compared to percutaneous coronary intervention (PCI) and optimal medical therapy (OMT) alone. Myocardial Flow Reserve (MFR) measured by Positro...
Article
Background and purpose: Abnormal electrical conduction and excitability associated with fibrosis in the left atrium (LA) may serve as a substrate for atrial fibrillation (AF). Electroanatomical voltage mapping systems (EAMs) have become a dominant facilitator to treat AF with catheter ablation assisted by additional diagnostic imaging modalities....
Article
Full-text available
Angiotensin receptor blocker-neprilysin inhibitor (ARNi) therapy improves the prognosis of heart failure patients. However, the mechanisms remain unclear. This study investigated the biological effects of ARNi with neprilysin inhibitor sacubitril and angiotensin receptor blocker valsartan on myocardial remodeling and cardiac perfusion in experiment...
Article
Purpose Neurohormonal dysfunction has been implicated in pulmonary arterial hypertension (PAH), and therefore may be an important modifiable target. Despite β-blocker's proven efficacy in left heart failure, their use in PAH and RV failure is less established. The objectives of the study were twofold, to determine the effects of β-receptor blockade...
Article
Introduction: Patient body motion is known to cause large deviations in the determination of myocardial blood flow (MBF) with errors exceeding 300%. Accurate correction for patient whole-body motion is still a largely unsolved problem in cardiac positron emission tomography (PET) imaging. Objective: This study evaluated the efficacy of using Nat...
Article
Background Our aim was to determine if end-stage liver disease (ESLD) is associated with an attenuated response to vasodilator-stress or dobutamine-stress using ⁸²Rb-PET MPI with blood flow quantification. Methods and Results Pre-liver transplant patients who had a normal dipyridamole-stress (n = 27) or dobutamine-stress (n = 26) ⁸²Rb PET/CT MPI s...
Article
Full-text available
Background: Graphical methods of radiotracer kinetic modeling in PET are ideal for parametric imaging and data quality assurance but can suffer from noise bias. This study compared the Logan and Multilinear Analysis-1 (MA1) graphical models to the standard one-tissue-compartment (1TC) model, including correction for partial-volume effects, in dyna...