Cardiac Positron Emission Tomography Imaging Research Articles

Impact of point spread function modeling and time-of-flight on myocardial blood flow and myocardial flow reserve measurements for rubidium-82 cardiac PET

BackgroundMyocardial flow reserve (MFR) obtained from dynamic cardiac positron emission tomography (PET) with rubidium-82 (Rb-82) has been shown to be a useful measurement in assessing coronary artery disease. Advanced PET reconstructions with point spread function modeling and time-of-flight have been shown to improve image quality but also have an impact on kinetic analysis of dynamic data. This study aims to determine the impact of these algorithms on MFR data. MethodsDynamic Rb-82 cardiac PET images from 37 patients were reconstructed with standard and advanced reconstructions. Area under curve (AUC) of the blood input function (BIF), myocardial blood flow (MBF) and MFR were compared with each reconstruction. ResultsNo significant differences were seen in MFR for the two reconstructions. A relatively small mean difference in MBF data of +11.9% was observed with advanced reconstruction compared with the standard reconstruction but there was considerable variability in the degree of change (95% confidence intervals of −16.2% to +40.0%). Small systematic relative differences were seen for AUC BIF (mean difference of −6.3%; 95% CI −17.5% to +5.4%). Conclusion:MFR results from Rb-82 dynamic PET appear to be robust when generated by standard or advanced PET reconstructions. Considerable increases in MBF values may occur with advanced reconstructions, and further work is required to fully understand this.

Cardiac Metabolism Imaging and Chemotherapy Cardiotoxicity

Cardiac oncology is a field that will become increasingly important in clinical practice as we become more effective in treating cancer and those treated with chemotherapy live longer. Potential cardiac toxicity associated with some chemotherapy treatments can cause significant morbidity. Molecular positron emission tomography (PET) to assess cardiac metabolism is a promising technology that could increase our knowledge of chemotherapy-related toxicity in the heart. We review the utility of PET cardiac imaging to evaluate the toxic effects of chemotherapy on metabolism. Free fatty acids, glucose and ketone bodies are major substrates for cardiac energy consumption, and adaptations to their use can occur under differing conditions. Cardiovascular complications of chemotherapy can include direct effects on metabolism as well as injury to myocardial tissue by effects on endothelial function, hypertension or ischemia. Even novel chemotherapies that are designed to be more specific in their actions continue to be associated with cardiotoxicity. Further study is required to understand the effects of cardiotoxicity related to chemotherapy, and to develop techniques for its detection as well as prevention. PET cardiac imaging could be used to assist in the early detection of cardiotoxicity and help guide management clinically. It may offer insights to assist in the development of novel treatments and methods for cardioprotection.

Abstract 19211: The Relationship Between Anatomical and Functional Coronary Artery Disease Severity and Transmural Myocardial Blood Flow Distribution

Objectives: To determine the impact of lesion severity as assessed by the fractional flow reserve (FFR) on the transmural perfusion gradient (TPG) using H215O positron emission tomography (PET) imaging in patients evaluated for coronary artery disease (CAD). Background: Myocardial ischemia occurs principally in the subendocardial layer, whereas conventional myocardial perfusion imaging provides no information on the transmural myocardial blood flow (MBF) distribution. Methods: Sixty-six patients evaluated for CAD were prospectively enrolled and underwent H215O PET imaging for quantification of TPG. Subsequently, invasive coronary angiography was performed and FFR obtained in all coronary arteries irrespective of the PET imaging results. Results: Thirty (45%) patients were diagnosed with significant CAD (i.e. FFR ≤ 0.80), whereas on a per vessel analysis (n=198), 53 (27%) displayed a positive FFR. Hyperemic MBF decreased significantly from 3.09 ± 1.16 to 1.67 ± 0.57 mL·min-1·g-1 (p < 0.001) in nonischemic and ischemic myocardium, respectively. The TPG decreased during hyperemia as compared with baseline (1.20 ± 0.14 vs. 0.94 ± 0.17, p<0.001), and was lower in arteries with a positive FFR (0.97 ± 0.16 vs. 0.88 ± 0.18, p<0.01). A TPG threshold of 0.94 yielded anc accuracy to detect CAD of 59%, which was inferior to transmural MBF with an optimal cutoff of 2.20 mL·min-1·g-1 and an accuracy of 85% (p < 0.001). Conclusions: Cardiac H215O PET imaging is able to detect TPGs and demonstrates a significantly lower hyperemic TPG in ischemic myocardium. However, the diagnostic accuracy of TPG seems to be limited compared to quantitative transmural MBF.

Taking the perfect nuclear image: Quality control, acquisition, and processing techniques for cardiac SPECT, PET, and hybrid imaging

Nuclear Cardiology for the past 40 years has distinguished itself in its ability to non-invasively assess regional myocardial blood flow and identify obstructive coronary disease. This has led to advances in managing the diagnosis, risk stratification, and prognostic assessment of cardiac patients. These advances have all been predicated on the collection of high quality nuclear image data. National and international professional societies have established guidelines for nuclear laboratories to maintain high quality nuclear cardiology services. In addition, laboratory accreditation has further advanced the goal of the establishing high quality standards for the provision of nuclear cardiology services. This article summarizes the principles of nuclear cardiology single photon emission computed tomography (SPECT) and positron emission tomography (PET) imaging and techniques for maintaining quality: from the calibration of imaging equipment to post processing techniques. It also will explore the quality considerations of newer technologies such as cadmium zinc telleride (CZT)-based SPECT systems and absolute blood flow measurement techniques using PET.

Impact of anatomical and functional severity of coronary atherosclerotic plaques on the transmural perfusion gradient: a H215O PET study

353 Objectives The present study aimed to determine the impact of lesion severity as assessed by the fractional flow reserve (FFR) on the transmural perfusion gradient (TPG) using H215O positron emission tomography (PET) imaging in patients evaluated for coronary artery disease (CAD). Methods Sixty-six patients evaluated for CAD were prospectively enrolled and underwent H215O PET imaging for quantification of TPG, which was defined as the ratio of subendocardial to supepicardial myocardial blood flow (MBF). Subsequently, invasive coronary angiography was performed and FFR obtained in all coronary arteries irrespective of the PET imaging results. Results Thirty (45%) patients were diagnosed with significant CAD (i.e. FFR ≤ 0.80), whereas on a per vessel analysis (n=198), 53 (27%) displayed a positive FFR. Transmural hyperemic MBF decreased significantly from 3.09 ± 1.16 to 1.67 ± 0.57 mL/min/g (p Conclusions Cardiac H215O PET imaging is able to detect transmural perfusion gradients and demonstrates a significantly lower hyperemic TPG in ischemic myocardium. However, the diagnostic accuracy of TPG seems to be limited compared to quantitative transmural perfusion assessment.

Variation in Quantitative Myocardial Perfusion Due to Arterial Input Selection

This study compared the clinical implications of quantifying myocardial perfusion among different potential arterial input sites: the high (HAo) and basal (BAo) ascending aorta, descending aorta (DA), left atrium (LA), and left ventricular (LV) cavity. Absolute myocardial perfusion and its hyperemic reserve imaged by positron emission tomography (PET) can serve as noninvasive functional measures of physiologic severity. Quantitative myocardial perfusion by PET depends on the time-concentration of vascular activity, called arterial input (AI). However, arterial activity imaged by PET can vary among sites due to partial volume effects from anatomic size, cardiac or respiratory motion out of fixed regions of interest, and spillover from neighboring vascular structures. Patients underwent cardiac rubidium-82 PET imaging with flow quantification using various anatomic AI. After excluding sites with overt spillover or misregistration, we selected the customized, highest AI among the BAo, HAo, DA, and LA. Average whole heart flows and percent of LV with substantial definite ischemia were compared among sites. Of 288 cases, LA was selected in roughly half, with HAo in another quarter to one-third. Compared with using the customized AI, rest and stress absolute flow were higher by 5% to 10% for HAo, 14% for BAo, 19% to 23% for DA, and 46% to 49% for LV due to artifactually low AI values. The ratio of coronary flow reserve to its customized value was less affected, although its 95% confidence interval increased among AI locations: 7% for LA, 16% for HAo, 20% for BAo, 28% for DA, and 31% for LV. The best customized site for AI activity varies for each patient among potential anatomic locations. Selection of the customized arterial site for each individual improved quantification of myocardial perfusion and coronary flow reserve with less variability compared with utilizing a single, pre-selected, fixed anatomic site.

Regional patterns of cardiac sympathetic denervation in patients with type 2 diabetes mellitus and it's relationship to autonomic dysfunction

Objective: In this study we evaluated regional myocardial blood flow (MBF) and left ventricular (LV) sympathetic innervation using positron emission tomography (PET) and its relationship to standard autonomic function tests (AFT). Methods: We studied 12 diabetic patients (7M, 5F) (mean age 62±8), and 5 healthy controls (2M, 3F) (mean age 59±10). All patients underwent AFT and cardiac PET imaging with oxygen-15 labeled water to measure myocardial blood flow (MBF) and carbon –11 hydroxyephedrine (HED) to assess presynaptic cardiac sympathetic nerves. HED images were read semiquantitatively (summed score 4 segment/4 point model) and quantitatively (3-compartment model) to quantify cardiac HED density and flux (B-max). Single compartment model was used for MBF quantification. Results: All 5 controls had normal MBF, homogeneous uptake of HED, no regional difference in B-max and normal AFT. All 12 diabetic patients had normal MBF, 5 had homogeneous uptake of HED and 7 had heterogeneous uptake. The average HED defects summed score in diabetic patients was 9 in apical, 15 in basal lateral, 11 in distal lateral and 0 in septal region. In heterogeneous group there was a significant difference in B-max between the septal and lateral wall regions (24±12 vs.18 ± 10). On AFT all 12 diabetic patients had normal resting heart rate, RR and normal postural heart rate variability but 6/12 had postural hypotension. All 6 of these patients had heterogeneous HED uptake. Conclusions: Diabetic patients exhibited LV sympathetic dysfunction predominantly in the lateral wall region and only postural hypotension was significantly correlated with it.

Advances in Cardiac SPECT and PET Imaging: Overcoming the Challenges to Reduce Radiation Exposure and Improve Accuracy

Nuclear cardiology came of age in the 1970s and subsequently has expanded so that more than 9 million single-photon emission computed tomography (SPECT) studies are performed annually in North America. Coronary artery disease management has demanded a reliable technique that will detect, risk stratify, and assist with revascularization decisions. Using cardiac SPECT and positron-emission tomography (PET), researchers and clinicians have sought to achieve excellence in coronary artery disease diagnosis and risk stratification, and strive to achieve higher standards in these areas. Developments in other cardiac imaging modalities, however, such as cardiac computed tomography, cardiac magnetic resonance, and echocardiography, have raised expectations in terms of diagnostic accuracy and achieving high quality images with little or no ionizing radiation exposure. The challenge facing nuclear cardiology as it embarks upon a fifth decade of clinical use is whether high quality images can be obtained at lower radiation exposures. In this review we consider current practice in SPECT and PET perfusion imaging. We discuss emerging advances in techniques, technologies, and radiotracers that focus specifically on improvements in image quality that enhance diagnostic accuracy while reducing radiation exposure. We provide a perspective as to the future roles of cardiac SPECT and PET in ischemic heart disease, and consider emerging novel applications beyond perfusion imaging. Although for a number of years nuclear cardiology has shone brightly as a leading light for the imaging of ischemic heart disease, its half-life has not yet been reached. Instead, even with the pressure to reduce radiation exposure, the future continues to look bright for cardiac SPECT and PET.

Dynamic Cardiac PET Imaging: Extraction of Time-Activity Curves Using ICA and a Generalized Gaussian Distribution Model

Kinetic modeling of metabolic and physiologic cardiac processes in small animals requires an input function (IF) and a tissue time-activity curves (TACs). In this paper, we present a mathematical method based on independent component analysis (ICA) to extract the IF and the myocardium's TACs directly from dynamic positron emission tomography (PET) images. The method assumes a super-Gaussian distribution model for the blood activity, and a sub-Gaussian distribution model for the tissue activity. Our appreach was applied on 22 PET measurement sets of small animals, which were obtained from the three most frequently used cardiac radiotracers, namely: desoxy-fluoro-glucose ((18)F-FDG), [(13)N]-ammonia, and [(11)C]-acetate. Our study was extended to PET human measurements obtained with the Rubidium-82 ((82) Rb) radiotracer. The resolved mathematical IF values compare favorably to those derived from curves extracted from regions of interest (ROI), suggesting that the procedure presents a reliable alternative to serial blood sampling for small-animal cardiac PET studies.

A three-dimensional model-based partial volume correction strategy for gated cardiac mouse PET imaging

Quantification in cardiac mouse positron emission tomography (PET) imaging is limited by the imaging spatial resolution. Spillover of left ventricle (LV) myocardial activity into adjacent organs results in partial volume (PV) losses leading to underestimation of myocardial activity. A PV correction method was developed to restore accuracy of the activity distribution for FDG mouse imaging. The PV correction model was based on convolving an LV image estimate with a 3D point spread function. The LV model was described regionally by a five-parameter profile including myocardial, background and blood activities which were separated into three compartments by the endocardial radius and myocardium wall thickness. The PV correction was tested with digital simulations and a physical 3D mouse LV phantom. In vivo cardiac FDG mouse PET imaging was also performed. Following imaging, the mice were sacrificed and the tracer biodistribution in the LV and liver tissue was measured using a gamma-counter. The PV correction algorithm improved recovery from 50% to within 5% of the truth for the simulated and measured phantom data and image uniformity by 5–13%. The PV correction algorithm improved the mean myocardial LV recovery from 0.56 (0.54) to 1.13 (1.10) without (with) scatter and attenuation corrections. The mean image uniformity was improved from 26% (26%) to 17% (16%) without (with) scatter and attenuation corrections applied. Scatter and attenuation corrections were not observed to significantly impact PV-corrected myocardial recovery or image uniformity. Image-based PV correction algorithm can increase the accuracy of PET image activity and improve the uniformity of the activity distribution in normal mice. The algorithm may be applied using different tracers, in transgenic models that affect myocardial uptake, or in different species provided there is sufficient image quality and similar contrast between the myocardium and surrounding structures.

Evaluation of LMI1195, a Novel 18 F-Labeled Cardiac Neuronal PET Imaging Agent, in Cells and Animal Models

Heart failure has been associated with impaired cardiac sympathetic neuronal function. Cardiac imaging with radiolabeled agents that are substrates for the neuronal norepinephrine transporter (NET) has demonstrated the potential to identify individuals at risk of cardiac events. N-[3-Bromo-4-(3-[18F]fluoro-propoxy)-benzyl]-guanidine (LMI1195) is a newly developed 18F-labeled NET substrate designed to allow cardiac neuronal imaging with the high sensitivity, resolution, and quantification afforded by positron emission tomography (PET). LMI1195 was evaluated in comparison with norepinephrine (NE) in vitro and 123I-meta-iodobenzylguanidine (MIBG) in vivo. The affinity (Ki) of LMI1195 for NET was 5.16 ± 2.83 μmol/L, similar to that of NE (3.36 ± 2.77 μmol/L) in a cell membrane-binding assay. Similarly, LMI1195 uptake kinetics examined in a human neuroblastoma cell line had Km and Vmax values of 1.44 ± 0.76 μmol/L and 6.05 ± 3.09 pmol/million cells per minute, comparable to NE (2.01 ± 0.85 μmol/L and 6.23 ± 1.52 pmol/million cells per minute). In rats, LMI1195 heart uptake at 15 and 60 minutes after intravenous administration was 2.36 ± 0.38% and 2.16 ± 0.38% injected dose per gram of tissue (%ID/g), similar to 123I-MIBG (2.14 ± 0.30 and 2.19 ± 0.27%ID/g). However, the heart to liver and lung uptake ratios were significantly higher for LMI1195 than for 123I-MIBG. In rabbits, desipramine (1 mg/kg), a selective NET inhibitor, blocked LMI1195 heart uptake by 82%, which was more effective than 123I-MIBG (53%), at 1 hour after dosing. Sympathetic denervation with 6-hydroxydopamine, a neurotoxin, resulted in a marked (79%) decrease in LMI1195 heart uptake. Cardiac PET imaging with LMI1195 in rats, rabbits, and nonhuman primates revealed clear myocardium with low radioactivity levels in the blood, lung, and liver. Imaging in rabbits pretreated with desipramine showed reduced heart radioactivity levels in a dose-dependent manner. Additionally, imaging in sympathetically denervated rabbits resulted in low cardiac image intensity with LMI1195 but normal perfusion images with flurpiridaz F 18, a PET myocardial perfusion imaging agent. In nonhuman primates pretreated with desipramine (0.5 mg/kg), imaging with LMI1195 showed a 66% decrease in myocardial uptake. In a rat model of heart failure, the LMI1195 cardiac uptake decreased as heart failure progressed. LMI1195 is a novel (18)F imaging agent retained in the heart through the NET and allowing evaluation of the cardiac sympathetic neuronal function by PET imaging.

Fatty Acid Imaging of the Heart

Imaging metabolic processes in the human heart yields valuable insights into the mechanisms contributing to myocardial pathology and allows assessment of the efficacy of therapies designed to treat cardiac disease. Recent advances in fatty acid (FA) imaging using positron emission tomography (PET) include the development of a method to assess endogenous triglyceride metabolism and the design of new fluorine-18 labeled tracers. Studies of patients with diabetes have shown that the heart is resistant to insulin-mediated glucose uptake and that metabolism of nonesterified FA is upregulated. Cardiac PET imaging has also recently shown the increase in myocardial FA uptake seen in obese patients can be reversed with weight loss. And a pilot study of patients with chronic kidney disease demonstrated that PET imaging can reveal myocardial metabolic alterations that parallel the decline in estimated glomerular filtration rate. Recent advances in FA imaging using single photon emission computed tomography (SPECT) have been accomplished with the tracer β-methyl-p-[(123)I]-iodophenyl-pentadecanoic acid (BMIPP). Two meta-analyses showed this imaging technique has a diagnostic accuracy for the detection of obstructive coronary artery disease that compares favorably with SPECT myocardial perfusion imaging and that BMIPP imaging yields excellent prognostic data in patients across the spectrum of coronary artery disease. A recent multicenter study of patients presenting with acute coronary syndromes found BMIPP SPECT imaging has greater diagnostic sensitivity than, and enhances the negative predictive value of, clinical assessment alone. Because of their exquisite sensitivity, nuclear imaging techniques facilitate the study of physiologic processes that are the key to our understanding of cardiac metabolism in health and disease.

Coronary calcium score scan-based attenuation correction in cardiovascular PET imaging

Cardiac positron emission tomography (PET)/CT imaging is a noninvasive procedure allowing the assessment of coronary artery disease (CAD). CT-based attenuation correction of PET data is essential for accurate quantitative analysis in PET/CT imaging. Coronary artery calcium scoring CT (CaScCT) is used as a noninvasive tool for the diagnosis of atherosclerosis in patients with medium risk for CAD. In addition to the CaScCT examination, current cardiac rest/stress NH3 or ¹⁸F-fluorodeoxyglucose viability PET/CT protocols incorporate a correlated low-dose CT scan for attenuation correction purposes (ACCT). As a result, the patient receives a non-negligible radiation dose. The aim of this study is to evaluate the possibility of using CaScCT images for AC of myocardial rest/stress/viability PET data with the aim of reducing patient dose. Since in cardiac PET/CT protocols, the CaScCT examination is usually reconstructed using a small field-of-view, the CaScCT data were reconstructed again with extended field-of-view (ExCaScCT) and used for AC of the corresponding PET data. The feasibility study was performed using 10 patients including four NH3 perfusion and six ¹⁸F-fluorodeoxyglucose viability examinations acquired on the Biograph TP 64 PET/CT scanner. The assessment of PET images corrected using both ACCT and ExCaScCT images was carried out through qualitative assessment performed by an expert nuclear medicine specialist in addition to the regression analysis and the Bland-Altman plots, and 20-segment myocardial bull's eye view analysis. Despite the good agreement between PET images corrected using ACCT and ExCaScCT images as expressed by the correlation coefficient and slope of the regression line in viability (0.949 ± 0.041 and 0.994 ± 0.124) and stress perfusion examinations (0.944 ± 0.008 and 0.968 ± 0.055), the rest perfusion examinations had weak correlation (0.454 ± 0.203 and 0.757 ± 0.193). This is attributed to the fact that the CaScCT scan is performed immediately after the stress/viability ACCT in our protocol that leads to a small misalignment between the CaScCT and stress/viability ACCT images, whereas there is a large misalignment between the CaScCT and rest ACCT images. The bull's eye view analysis showed that the difference between the uptake values was larger in the inferior wall because of diaphragm motion. Our preliminary results seem to suggest that the calcium score study could be used for attenuation correction of cardiac PET images, thus allowing the elimination of ACCT in viability and stress perfusion studies and as such reduce patient dose.

Pre-Clinical Myocardial Metabolic Alterations in Chronic Kidney Disease

The risk for cardiovascular events conferred by decreased renal function is curvilinear with exponentially greater increases in risk as estimated glomerular filtration rate (eGFR) declines. In 13 non-diabetic pre-dialysis chronic kidney disease (CKD) patients, we employed quantitative F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) as a means to measure myocardial metabolic changes. Methods: Dynamic cardiac FDG PET images were acquired after 6 h fasting and glucose loading. Corrections for attenuation, scatter, randoms, dead time and decay were applied to the PET data and myocardial glucose utilization (MGU) was calculated using the Patlak method in conjunction with standardized myocardial regions of interest and an image-derived input function (left atrium). MGU was compared with eGFR based on a serum creatinine drawn within 2 weeks of the study date. Results: MGU was relatively uniform between the myocardial sectors (coefficient of variation = 16.2 ± 6.8%) within each patient. Between patients, whole myocardium MGU varied considerably with a range of 37.3–156.2 µmol/min/100 g and a mean of 68.9 ± 38.3 µmol/min/ 100 g. eGFR ranged from 11–89 ml/min/1.73 m² with a mean of 42.8 ± 26.9 ml/min/1.73 m². There was an inverse correlation between whole myocardium MGU and eGFR (Spearman’s rho correlation = –0.615, p = 0.025). In multivariate analysis, the relationship between MGU and eGFR was sustained with adjustment for age, race and gender (adjusted β = –1.56 ± 0.48, p = 0.01). There was no correlation between cardiac workload and eGFR (p = NS). Conclusions: A significant inverse correlation between MGU and eGFR is supportive of the hypothesis that CKD is associated with myocardial metabolic changes, which could not be attributed to demographic factors or cardiac workload. Dynamic FDG PET could provide a sensitive, non-invasive, quantitative tool for investigating pre-clinical myocardial abnormalities in patients with CKD.

ECG-triggered 18F-fluorodeoxyglucose positron emission tomography imaging of the rat heart is dramatically enhanced by acipimox

18F-Fluorodeoxyglucose (FDG) imaging, provided by current positron emission tomography (PET) systems dedicated to small animals,might provide a precise functional assessment of the left ventricle (LV) in rats, although conventional metabolic conditioning by hyperinsulinaemic glucose clamping is not well adapted to this setting. This study was aimed at assessing cardiac FDG PET in rats premedicated with acipimox, a potent nicotinic acid derivative yielding comparable image quality to clamping in man. Metabolic conditioning was compared in Wistar rats between a conventional oral glucose loading (1.5 mg/kg) and acipimox, which was given at high but well tolerated doses subcutaneously (25 mg/kg) or orally (50 mg/kg). Myocardial to blood (M/B) activity ratio and myocardial signal to noise (S/N) ratio were analysed on gated FDG PET images. The S/N ratio of the gated cardiac images evolved in parallel with the M/B activity ratio and these two ratios were independently enhanced by glucose loading and acipimox. However, these enhancements were: (1) dramatic for acipimox, especially for the high oral dose of 50 mg/kg (from 2.85 +/- 0.57 to 10.73 +/- 0.54 for the M/B ratio of rats with or without glucose loading; p<0.0001) and (2) much more limited for glucose loading (from 6.61 +/- 0.49 to 7.89 +/- 0.41 for the M/B ratio of rats with or without acipimox administration; p=0.049). With the high oral dose of acipimox, the gated cardiac FDG PET images had very high S/N ratios, at least equivalent to those currently documented in man. Metabolic conditioning by oral doses of acipimox is highly efficient for experimental studies planned with cardiac FDG PET in rats.

The Application of a Statistical Shape Model to Diaphragm Tracking in Respiratory-Gated Cardiac PET Images

Respiratory-induced diaphragm mismatch between positron emission tomography (PET) and computed tomography (CT) has been identified as a source of attenuation-correction artifact in cardiac PET. Diaphragm tracking in gated PET could therefore form part of a mismatch correction technique, where a single CT is transformed to match each PET frame. To investigate the feasibility of such a technique, a statistical shape model of the diaphragm was constructed from gated CT and applied to two gated 18F-FDG PET-CT datasets. A poor level of accuracy was obtained when the model was fitted to landmarks obtained from PET, with errors of 3.6 and 5.0 mm per landmark for the two patients, despite inclusion of the data within the model construction. However, errors were reduced to 2.4 and 1.9 mm with the incorporation of a single frame of CT landmarks. These values are closer to the baseline measure of fitting solely to CT landmarks, found to be 2.2 and 1.2 mm in this case. Excluding the datasets from the model yielded similar trends but with higher overall residual errors, indicating the need for a larger training set. Therefore, a highly trained diaphragm model could negate the need for a gated CT for diaphragm tracking, provided that information from a static CT is incorporated.

Cardiac Positron Emission Tomography Imaging—State of the Art

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Рositron emission tomography in assessment of heart sympathetic nervous system

This article summarizes data of the studies with the use of positron emission tomography (PET) and devotes technical aspects and clinical application of PET for assessment of the autonomic nervous system of the heart in patients with cardiac diseases. According to the results of experimental and clinical studies PET with radiolabeled сatecholamines and adrenoreceptor ligands provides us with information about alteration of cardiac sympathetic innervation at different steps of neurotransmission. It plays a key role in the progression of various heart diseases such as ischemia, diabetes mellitus, heart failure and noncoronary arrhythmia. Cardiac sympathetic neuronal PET imaging seems to be a good tool for the stratification of the risk of the severe cardiovascular complications.

Cardiac Positron Emission Tomography Imaging – State of the Art

Cardiac Positron Emission Tomography Imaging – State of the Art

Cardiac positron emission tomography imaging

Cardiac positron emission tomography (PET) imaging has advanced from primarily a research tool to a practical, high-performance clinical imaging modality. The widespread availability of state-of-the-art PET gamma cameras, the commercial availability of perfusion and viability PET imaging tracers, reimbursement for PET perfusion and viability procedures by government and private health insurance plans, and the availability of computer software for image display of perfusion, wall motion, and viability images have all been a key to cardiac PET imaging becoming a routine clinical tool. Although myocardial perfusion PET imaging is an option for all patients requiring stress perfusion imaging, there are identifiable patient groups difficult to image with conventional single-photon emission computed tomography imaging that are particularly likely to benefit from PET imaging, such as obese patients, women, patients with previous nondiagnostic tests, and patients with poor left ventricular function attributable to coronary artery disease considered for revascularization. Myocardial PET perfusion imaging with rubidium-82 is noteworthy for high efficiency, rapid throughput, and in a high-volume setting, low operational costs. PET metabolic viability imaging continues to be a noninvasive standard for diagnosis of viability imaging. Cardiac PET imaging has been shown to be cost-effective. The potential of routine quantification of resting and stress blood flow and coronary flow reserve in response to pharmacologic and cold-pressor stress offers tantalizing possibilities of enhancing the power of PET myocardial perfusion imaging. This can be achieved by providing assurance of stress quality control, in enhancing diagnosis and risk stratification in patients with coronary artery disease, and expanding diagnostic imaging into the realm of detection of early coronary artery disease and endothelial dysfunction subject to risk factor modification. Combined PET and x-ray computed tomography imaging (PET-CT) results in enhanced patient throughput and efficiency. The combination of multislice computed tomography scanners with PET opens possibilities of adding coronary calcium scoring and noninvasive coronary angiography to myocardial perfusion imaging and quantification. Evaluation of the clinical role of these creative new possibilities warrants investigation.