Clinical use of cardiac PET/MRI: current state-of-the-art and potential future applications

Recent Advances in Cardiac Magnetic Resonance for Imaging of Acute Myocardial Infarction

Acute myocardial infarction (AMI) is one of the primary causes of death worldwide, with a high incidence and mortality rate. Assessment of the infarcted and surviving myocardium, along with microvascular obstruction, is crucial for risk stratification, treatment, and prognosis in patients with AMI. Nonionizing radiation, excellent soft tissue contrast resolution, a large field of view, and multiplane imaging make cardiac magnetic resonance (CMR) a "one-stop" method for assessing cardiac structure, function, perfusion, and metabolism. Hence, this imaging technology is considered the "gold standard" for evaluating myocardial function and viability in AMI. This review critically compares the advantages and disadvantages of CMR with other cardiac imaging technologies, and relates the imaging findings to the underlying pathophysiological processes in AMI. A more thorough understanding of CMR technology will clarify their advanced clinical diagnosis and prognostic assessment applications, and assess the future approaches and challenges of CMR in the setting of AMI.

Update on Positron Emission Tomography/Magnetic Resonance Imaging: Cancer and Inflammation Imaging in the Clinic

Hybrid PET/MRI is highly valuable, having made significant strides in overcoming technical challenges and offering unique advantages such as reduced radiation, precise data coregistration, and motion correction. Growing evidence highlights the value of PET/MRI in broad clinical aspects, including inflammatory and oncological imaging in adults, pregnant women, and pediatrics, potentially surpassing PET/CT. This newly integrated solution may be preferred over PET/CT in many clinical conditions. However, further technological advancements are required to facilitate its broader adoption as a routine diagnostic modality.

Practical Guide to Interpreting Cardiac Magnetic Resonance in Patients with Cardiac Masses

It is common for a cardiac mass to be discovered accidentally during an echocardiographic examination. Following the relief of a cardiac mass, being able to evaluate and characterize it using non-invasive imaging methods is critical. Echocardiography, computed tomography (CT), cardiac magnetic resonance imaging (CMR), and positron emission tomography (PET) are the main imaging modalities used to evaluate cardiac masses. Although multimodal imaging often allows for a better assessment, CMR is the best technique for the non-invasive characterization of tissues, as the different MR sequences help in the diagnosis of cardiac masses. This article provides detailed descriptions of each CMR sequence employed in the evaluation of cardiac masses, underlining the potential information it can provide. The description in the individual sequences provides useful guidance to the radiologist in performing the examination.

Emerging molecular imaging targets and tools for myocardial fibrosis detection

Myocardial fibrosis is the heart's common healing response to injury. While initially seeking to optimize the strength of diseased tissue, fibrosis can become maladaptive, producing stiff poorly functioning and pro-arrhythmic myocardium. Different patterns of fibrosis are associated with different myocardial disease states, but the presence and quantity of fibrosis largely confer adverse prognosis. Current imaging techniques can assess the extent and pattern of myocardial scarring, but lack specificity and detect the presence of established fibrosis when the window to modify this process may have ended. For the first time, novel molecular imaging methods, including gallium-68 (68Ga)-fibroblast activation protein inhibitor positron emission tomography (68Ga-FAPI PET), may permit highly specific imaging of fibrosis activity. These approaches may facilitate earlier fibrosis detection, differentiation of active vs. end-stage disease, and assessment of both disease progression and treatment-response thereby improving patient care and clinical outcomes.

Hybrid-PET/MRT bei inflammatorischer Kardiomyopathie

Hintergrund

Die Myokarditis und die inflammatorische Kardiomyopathie sind aufgrund ihrer unterschiedlichen Auslöser, Phänotypen und Stadien diagnostisch häufig schwer zu diagnostizieren.

Methodische Innovationen und Probleme

Die kardiale Positronen-Emissions-Tomographie/Magnetresonanztomographie (PET/MRT) zeichnet sich neben der myokardialen Gewebecharakterisierung mittels MRT durch den möglichen Nachweis einer aktiven myokardialen Entzündung (Inflammation) mittels PET aus. Die Kombination von MRT und PET ist somit eher synergistisch als rein summativ: Die möglicherweise in der MRT vorhandenen kardialen Veränderungen lassen sich durch die PET in aktive inflammatorische (und somit noch potenziell reversible) Prozesse oder ältere chronische (irreversible) Narben unterscheiden. Die kardiale Sarkoidose mit einem potenziellen Nebeneinander von aktiven und chronischen Veränderungen bietet sich an, um die Stärken einer hybriden PET/MRT zur Geltung bringen zu lassen. Wichtig für eine aussagekräftige kardiale PET ist eine gute Vorbereitung mit Low-Carb-Diät, um eine suffiziente Suppression der myokardialen Glukoseaufnahme zu gewährleisten.

Empfehlungen

Die Diagnostik einer inflammatorischen Herzerkrankung sowie deren Charakterisierung in akut vs. chronische Prozesse gelingt mit der kardialen Hybrid-PET/MRT, wie am Beispiel der kardialen Sarkoidose gezeigt werden konnte.

Motion in nuclear cardiology imaging: types, artifacts, detection and correction techniques

In this paper, the authors review the field of motion detection and correction in nuclear cardiology with single photon emission computed tomography (SPECT) and positron emission tomography (PET) imaging systems. We start with a brief overview of nuclear cardiology applications and description of SPECT and PET imaging systems, then explaining the different types of motion and their related artefacts. Moreover, we classify and describe various techniques for motion detection and correction, discussing their potential advantages including reference to metrics and tasks, particularly towards improvements in image quality and diagnostic performance. In addition, we emphasize limitations encountered in different motion detection and correction methods that may challenge routine clinical applications and diagnostic performance.

Quantitative and qualitative evaluation of sequential PET/MRI using a newly developed mobile PET system for brain imaging

PURPOSE

To evaluate the clinical feasibility of a newly developed mobile PET system with MR-compatibility (flexible PET; fxPET), compared with conventional PET (cPET)/CT for brain imaging.

METHODS

Twenty-one patients underwent cPET/CT with subsequent fxPET/MRI using ¹⁸F-FDG. As qualitative evaluation, we visually rated image quality of MR and PET images using a four-point scoring system. We evaluated overall image quality for MR, while we evaluated overall image quality, sharpness and lesion contrast. As quantitative evaluation, we compared registration accuracy between two modalities [(fxPET and MRI) and (cPET and CT)] measuring spatial coordinates. We also examined the accuracy of regional ¹⁸F-FDG uptake.

RESULTS

All acquired images were of diagnostic quality and the number of detected lesions did not differ significantly between fxPET/MR and cPET/CT. Mean misregistration was significantly larger with fxPET/MRI than with cPET/CT. SUVmax and SUVmean for fxPET and cPET showed high correlations in the lesions (R = 0.84, 0.79; P < 0.001, P = 0.002, respectively). In normal structures, we also showed high correlations of SUVmax (R = 0.85, 0.87; P < 0.001, P < 0.001, respectively) and SUVmean (R = 0.83, 0.87; P < 0.001, P < 0.001, respectively) in bilateral caudate nuclei and a moderate correlation of SUVmax (R = 0.65) and SUVmean (R = 0.63) in vermis.

CONCLUSIONS

The fxPET/MRI system showed image quality within the diagnostic range, registration accuracy below 3 mm and regional ¹⁸F-FDG uptake highly correlated with that of cPET/CT.

Long-term follow-up of resection of primary benign right ventricular tumours: a 10-year surgical experience

INTRODUCTION

Primary benign right ventricular tumours are rare. They can cause significant mortality without appropriate and timely treatment. We investigated surgical treatment and survival characteristics for right ventricular tumours.

MATERIALS AND METHODS

From 2007 to 2017, 21 patients with primary benign right ventricular tumours who underwent tumour resection were retrospectively reviewed. Clinical findings and follow-up results were analysed.

RESULTS

Thirteen men and eight women were enrolled, with a mean age of 42.3 ± 15.3 years. The most frequent histotypes were myxoma, haemangioma and papillary fibroelastoma. Eight patients underwent concomitant tricuspid valvuloplasty and one had tricuspid valve replacement. No major adverse events or death occurred during the perioperative period. One patient with haemangioma underwent partial tumour resection; however, the tumour regressed gradually during follow-up. Within the 10-year follow-up period (mean 4.8 ± 2.6 years), the recurrence-free and overall survival rates were 81.0% and 85.7%, respectively.

CONCLUSIONS

Tumour resection for primary benign right ventricular tumours is safe and effective, and has a good prognosis. Tricuspid valvuloplasty or tricuspid valve replacement may be necessary for the resection of right ventricular tumours to improve the haemodynamics. Haemangiomas naturally undergo spontaneous regression.

Applications of PET-MR Imaging in Cardiovascular Disorders

Cardiac PET/MR imaging is an integrated imaging approach that requires less radiation than PET/computed tomography and combines the high spatial resolution and morphologic data from MR imaging with the physiologic information from PET. This hybrid approach has the potential to improve the diagnostic and prognostic evaluation of several cardiovascular conditions, such as ischemic heart disease, infiltrative diseases such as sarcoidosis, acute and chronic myocarditis, and cardiac masses. Herein, the authors discuss the strengths of PET and MR imaging in several cardiovascular conditions; the challenges and potential; and the current data on the application of this powerful hybrid imaging modality.

A case series on inflammatory cardiomyopathy and suspected cardiac sarcoidosis: role of cardiac PET in management

Background

Presentation of life-threatening arrhythmias concomitantly with a new-onset non-ischaemic cardiomyopathy raises concern for an inflammatory cardiomyopathy such as cardiac sarcoidosis or cardiac manifestations of connective tissue disease. Comprehensive workup for specific aetiologies may be unrevealing except for signs of myocardial inflammation identified on cardiac positron emission tomography (PET). Here, we present five cases of such subjects and their clinical course.

Case summary

We collected clinical, imaging, pathological, and follow-up data of five subjects presenting with arrhythmias and unexplained new-onset cardiomyopathy. Mean age was 56.2 ± 5.8 years. Three subjects presented with ventricular tachycardia and two with atrial arrhythmias. Echocardiography showed a mean left ventricular ejection fraction of 37 ± 9%_. Significant coronary artery disease was ruled out in all cases as the cause of the cardiomyopathy. All patients underwent cardiac magnetic resonance imaging (MRI) and PET scan at presentation and follow-up. In all patients, cardiac MRI revealed hyperenhancement in epicardial and mid-myocardial pattern in a non-coronary distribution, while PET scan revealed fluorodeoxyglucose (FDG) mismatch defects in multiple foci in a non-coronary distribution. Right ventricular biopsy was obtained in all patients and revealed interstitial fibrosis and cardiomyocyte hypertrophy. On median follow-up of 210 days, all subjects had improvement in both heart failure symptoms and arrhythmias and repeat PET in four out of five patients showed decreased inflammation.

Discussion

A high level of suspicion for inflammatory cardiomyopathy is needed in patients presenting with new unexplained cardiomyopathy and arrhythmias. A cardiac FDG-PET should be considered for diagnosis if cardiac inflammation is in the differential. This can inform further decisions regarding targeted immunomodulation therapy that may be helpful in this cohort.

Masses in right side of the heart: spectrum of imaging findings

Primary heart tumors are rare, benign tumors represent the majority of these. If a cardiac mass is found, the probability that it is a metastasis or a so-called “pseudo-mass” is extremely higher than a primary tumor. The detection of a heart mass during a transthoracic echocardiography (TE) is often unexpected. The TE assessment can be difficult, particularly if the mass is located at the level of the right chambers. Cardiac Computed Tomography (CCT) can be useful in anatomical evaluation and Cardiac Magnetic Resonance (CMR) for masses characterization as well. We provide an overview of right cardiac masses and their imaging futures. (www.actabiomedica.it)

Multimodality Imaging in the Evaluation of Intracardiac Masses

Intracardiac masses are classified as neoplastic or non-neoplastic. Prognosis varies based on the diagnosis of the mass since treatment options differ greatly. As novel imaging techniques emerge, a multimodality approach to the evaluation of intracardiac masses becomes an important part of non-invasive evaluation prior to potential surgical planning or oncological treatment. The purpose of this article is to compare the available imaging modalities-echocardiography, cardiovascular magnetic resonance, cardiac computed tomography, nuclear imaging, and emerging novel hybrid imaging techniques for future clinical applications-and to review the characteristic features seen on those modalities for the most common intracardiac masses.

Cardiac involvement in disseminated diffuse large B-cell lymphoma, successful management with chemotherapy dose reduction guided by cardiac imaging: A case report and review of literature

BACKGROUND

Secondary cardiac involvement by lymphoma has received limited attention in the medical literature, despite its grave prognosis. Although chemotherapy improves patients’ survival, a subgroup of treated patients dies suddenly due to myocardial rupture following chemotherapy initiation. Reducing the initial chemotherapy dose with dose escalation to standard doses may be effective in minimizing this risk but the data are limited. We report on the successful management of a patient with disseminated diffuse large B-cell lymphoma (DLBCL) involving the heart using such approach.

CASE SUMMARY

An 18-year-old male presented to our hospital with six months history of progressive dyspnea, orthopnea and cough. On physical examination, the patient was found to have a plethoric and mildly edematous face, fixed elevation of the right internal jugular vein, suggestive of superior vena cava obstruction, and a pelvic mass. Investigations during admission including a thoracoabdominal computed tomography (CT) scan with CT guided biopsy of the pelvic mass, echocardiography and cardiac magnetic resonance imaging led to the diagnosis of disseminated DLBCL with cardiac involvement. The patients were successfully treated with chemotherapy dose reduction followed by dose escalation to standard doses, under the guidance of cardiac imaging. The patient completed chemotherapy and underwent a successful bone marrow transplant. He is currently in remission and has a normal left ventricular function.

CONCLUSION

Imaging-guided chemotherapy dosing may minimize the risk of myocardial rupture in cardiac lymphoma. Data are limited. Management should be individualized.