PET-CMR in heart failure - synergistic or redundant imaging?

Multi-modality cardiac image computing: A survey

Multi-modality cardiac imaging plays a key role in the management of patients with cardiovascular diseases. It allows a combination of complementary anatomical, morphological and functional information, increases diagnosis accuracy, and improves the efficacy of cardiovascular interventions and clinical outcomes. Fully-automated processing and quantitative analysis of multi-modality cardiac images could have a direct impact on clinical research and evidence-based patient management. However, these require overcoming significant challenges including inter-modality misalignment and finding optimal methods to integrate information from different modalities. This paper aims to provide a comprehensive review of multi-modality imaging in cardiology, the computing methods, the validation strategies, the related clinical workflows and future perspectives. For the computing methodologies, we have a favored focus on the three tasks, i.e., registration, fusion and segmentation, which generally involve multi-modality imaging data, either combining information from different modalities or transferring information across modalities. The review highlights that multi-modality cardiac imaging data has the potential of wide applicability in the clinic, such as trans-aortic valve implantation guidance, myocardial viability assessment, and catheter ablation therapy and its patient selection. Nevertheless, many challenges remain unsolved, such as missing modality, modality selection, combination of imaging and non-imaging data, and uniform analysis and representation of different modalities. There is also work to do in defining how the well-developed techniques fit in clinical workflows and how much additional and relevant information they introduce. These problems are likely to continue to be an active field of research and the questions to be answered in the future.

Positron Emission Tomography in Heart Failure: From Pathophysiology to Clinical Application

Imaging modalities are increasingly being used to evaluate the underlying pathophysiology of heart failure. Positron emission tomography (PET) is a non-invasive imaging technique that uses radioactive tracers to visualize and measure biological processes in vivo. PET imaging of the heart uses different radiopharmaceuticals to provide information on myocardial metabolism, perfusion, inflammation, fibrosis, and sympathetic nervous system activity, which are all important contributors to the development and progression of heart failure. This narrative review provides an overview of the use of PET imaging in heart failure, highlighting the different PET tracers and modalities, and discussing fields of present and future clinical application.

Cardiovascular positron emission tomography: established and emerging role in cardiovascular diseases

Cardiac positron emission tomography (PET) imaging has established themselves firmly as excellent and reliable functional imaging modalities in assessment of the spectrum of coronary artery disease. With the explosion of technology advances and the dream of flow quantification now a reality, the value of PET is now well realized. Cardiac PET has proved itself as precise imaging modality that provides functional imaging of the heart in addition to anatomical imaging. It has established itself as one of the best available techniques for evaluation of myocardial viability. Hybrid PET/computed tomography provides simultaneous integration of coronary anatomy and function with myocardial perfusion and metabolism, thereby improving characterization of the dysfunctional area and chronic coronary artery disease. The availability of quantitative myocardial blood flow evaluation with PET provides additional prognostic information and increases diagnostic accuracy in the management of patients with coronary artery disease. Hybrid imaging seems to hold immense potential in optimizing management of cardiovascular diseases and furthering clinical research.

Diagnostic Value of Gadolinium Delayed Enhancement Combined with Longitudinal Relaxation Time Quantitative Imaging for Myocardial Amyloidosis

This article is based on the use of GE combined with longitudinal lag time to quantify cardiac MRI screening for amyloidosis autologous thousand-cell transplantation, combined with clinical routine risk stratification, method for risk assessment of patients with amyloidosis and monitor the patient’s evaluation of the efficacy after treatment. Cardiac involvement with systemic amyloidosis is of great significance for both treatment and prognosis assessment, and is essential for quantitative and qualitative diagnosis or objectively providing prognostic value. In summary, myocardial amyloidosis needs to be studied before heart failure. It is recommended that patients undergo routine cardiac MRI examination to comprehensively evaluate cardiac morphology, function, risk stratification, prognosis, and treatment guidance. Diagnosis based on a single modality has been replaced by a comprehensive multi-modality method, and there is sufficient evidence to show the potential value of cardiac. However, with the continuous improvement of quality and value in the medical field, the field of cardiac will inevitably develop. The predicted and baseline indexes of myocardial strain predicted cardiac remission were 0.96 and 0.79, respectively. When the predictive value of clinical routine indicators and cardiac indicators is analyzed using blood response as the evaluation standard, the reduction in end-diastolic volume/body surface area (P = 0.031) can predict complete haematological remission. Folded cross-validation test shows that the end-diastolic volume/body surface area reduction and the baseline index IgG combined with myocardial strain predict AUC of complete blood remission of 0.78 and 0.76, respectively. This study will also continue to follow up and increase the sample size to verify the current conclusions.

Diagnostic performance of FDG PET/CT in critically ill patients with suspected infection: A systematic review and meta-analysis

BACKGROUND/PURPOSE

Nuclear imaging, including gallium scintigraphy and fluorodeoxyglucose (FDG) positron emission tomography (PET), has been widely used to identify focus of infection in fever of unknown origin. However, little is known about its role in critically ill patients, who are usually with multiple inflammatory foci and unable to tolerate long image acquisition time. This systematic review aimed to evaluate the diagnostic performance of FDG PET for suspected infection in critically ill patients.

METHODS

PubMed and Embase were searched up to July 24th, 2019 to identify studies evaluating the diagnostic performance of FDG PET for finding infection focus in critically ill patients following the PRISMA guidelines. The bivariate mixed-effects model was used to pool the measure for diagnostic performance. Publication bias was evaluated by Deeks' method.

RESULTS

A total of 4 studies with 87 patients were included. All the four studies evaluated FDG PET. Majority of the patients were either mechanically ventilated (76%) or shocked requiring vasopressors (61%). Test and transportation related adverse events were rare (2%). The summary sensitivity and specificity were 0.94 (95% CI, 0.79-0.99) and 0.66 (95% CI, 0.45-0.83), respectively. The AUC for summary ROC curve was 0.83.

CONCLUSION

FDG PET was a very sensitive tool with acceptable specificity for detecting the origin of infection in critically ill patients. However, current available studies have limitation in evaluating safety issue. Further research should investigate both benefit and risk of doing this test for this group of vulnerable patients.

Left Ventricular Diastolic Dysfunction in a Rat Model of Diabetic Cardiomyopathy using ECG-gated 18F-FDG PET

In diabetic cardiomyopathy, left ventricular (LV) diastolic dysfunction is one of the earliest signs of cardiac involvement prior to the definitive development of heart failure (HF). We aimed to explore the LV diastolic function using electrocardiography (ECG)-gated ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET) imaging beyond the assessment of cardiac glucose utilization in a diabetic rat model. ECG-gated ¹⁸F-FDG PET imaging was performed in a rat model of type 2 diabetes (ZDF fa/fa) and ZL control rats at age of 13 weeks (n = 6, respectively). Under hyperinsulinemic-euglycemic clamp to enhance cardiac activity, ¹⁸F-FDG was administered and subsequently, list-mode imaging using a dedicated small animal PET system with ECG signal recording was performed. List-mode data were sorted and reconstructed into tomographic images of 16 frames per cardiac cycle. Left ventricular functional parameters (systolic: LV ejection fraction (EF), heart rate (HR) vs. diastolic: peak filling rate (PFR)) were obtained using an automatic ventricular edge detection software. No significant difference in systolic function could be obtained (ZL controls vs. ZDF rats: LVEF, 62.5 ± 4.2 vs. 59.4 ± 4.5%; HR: 331 ± 35 vs. 309 ± 24 bpm; n.s., respectively). On the contrary, ECG-gated PET imaging showed a mild but significant decrease of PFR in the diabetic rats (ZL controls vs. ZDF rats: 12.1 ± 0.8 vs. 10.2 ± 1 Enddiastolic Volume/sec, P < 0.01). Investigating a diabetic rat model, ECG-gated ¹⁸F-FDG PET imaging detected LV diastolic dysfunction while systolic function was still preserved. This might open avenues for an early detection of HF onset in high-risk type 2 diabetes before cardiac symptoms become apparent.

Mitochondrial metabolism in pulmonary hypertension: beyond mountains there are mountains

Pulmonary hypertension (PH) is a heterogeneous and fatal disease of the lung vasculature, where metabolic and mitochondrial dysfunction may drive pathogenesis. Similar to the Warburg effect in cancer, a shift from mitochondrial oxidation to glycolysis occurs in diseased pulmonary vessels and the right ventricle. However, appreciation of metabolic events in PH beyond the Warburg effect is only just emerging. This Review discusses molecular, translational, and clinical concepts centered on the mitochondria and highlights promising, controversial, and challenging areas of investigation. If we can move beyond the "mountains" of obstacles in this field and elucidate these fundamental tenets of pulmonary vascular metabolism, such work has the potential to usher in much-needed diagnostic and therapeutic approaches for the mitochondrial and metabolic management of PH.