Hybrid PET/MR Imaging of the Heart: Potential, Initial Experiences, and Future Prospects

Abstract

Learning Objectives: On successful completion of this activity, participants should be able to describe (1) advantages and shortcomings of hybrid PET/MR scanners with respect to cardiovascular applications (e.g. myocardial perfusion imaging and viability imaging), (2) additional value of the MR component in cardiac imaging, and (3) technical challenges and workflow considerations regarding hybrid PET/MR scanners in the field of cardiology (e.g. attenuation correction and cardiac/respiratory/patient motion).Financial Disclosure: Dr. Schwaiger is an investigator, meeting participant, and lecturer for Siemens Medical. The authors of this article have indicated no other relevant relationships that could be perceived as a real or apparent conflict of interest. CME Credit: SNMMI is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to sponsor continuing education for physicians. SNMMI designates each JNM continuing education article for a maximum of 2.0 AMA PRA Category 1 Credits. Physicians should claim only credit commensurate with the extent of their participation in the activity. For CE credit, participants can access this activity through the SNMMI Web site (http:// www.snmmi.org/ce_online) through March 2016.PET/CT and other combined scanners have in the past decade rapidly emerged as important research tools and are proving to be invaluable for improved diagnostics in routine nuclear medicine. The design of hybrid PET/MR scanners presented a formidable technical challenge, and only recently were these instruments introduced to the market. Initial expectations of the performance of these scanners have been high, notably because of the potential for superior tissue contrast inherent in the MR modality, as well as the potential for multiparametric functional imaging in conjunction with PET. However, the additional value and potential clinical role that these new systems might bring to the cardiac field have yet to be documented. This review presents a comparative summary of the existing applications for PET and MR in the field of cardiology and suggests potential cardiac applications exploiting unique properties of the newly introduced combined instrumentation. The diverse range of imaging modalities for cardiology includes echocardiography, CT, MR imaging, SPECT, and PET, each of which offers distinct properties and advantages. The demand for combined PET/CT instrumentation in clinical nuclear medicine has grown remarkably, because of the notable advantages presented by hybrid imaging with respect to anatomic localization of lesions. Although these advantages were initially driven by the demands of oncology imaging, the resultant broader availability of PET/CT has provided the opportunity to use these scanners for indications beyond oncology, such as in the field of cardiac imaging (1). Furthermore, CT images are necessary for rapid attenuation correction, which is of particular importance for quantification in myocardial perfusion imaging. Through the use of suitable CT components a...

A case of cardiac sarcoidosis mimicking cardiac amyloidosis on cardiovascular magnetic resonance

“…Recently, hybrid imaging of FDG‐PET and CMR has been applied for non‐invasive imaging of cardiac diseases 13. In particular, cardiac positron emission tomography–magnetic resonance imaging is reported to be clinically feasible for the detection of cardiac inflammation such as active CS 14…”

Cardiovascular Hybrid Imaging using PET/MRI

“…2) [8, 13,14]. One study reported on a patient with early interventional reperfusion after coronary artery occlusion that showed reduced glucose utilization in the perfusion territory of the culprit artery but did not show myocardial necrosis in terms of late gadolinium-enhancement.…”

“…Among other things, this could be utilized as a success parameter in studies regarding cardioprotection. Other studies using PET/MRI have shown that after diet conversion of myocardial metabolism to fatty acid metabolism, the inflammatory reaction in the myocardial scar after myocardial infarction can be observed due to increased glucose utilization [14,16]; this could be used to guide new therapies to modulate infarct healing. Likewise, imaging of angiogenesis in the course of infarct healing uses special PET tracers such as αvβ3 Integrin; in the future this may result in additional applications of cardiac PET/ MRI [17].…”

“…A very promising application in the area of ischemic cardiomyopathy could be the preoperative identification of patients who could benefit from coronary revascularization. Although quantification of myocardial blood flow (MBF) with PET perfusion tracers in integrated PET/MRI appears to be possible [14], it is not yet certain whether this offers significant advantages over perfusion measurement using MRI contrast media. Com-pared to the usual MRI contrast agents, some PET tracers (e. g. 15 O-H 2 O or 18 F-Flurpiridaz) demonstrate an almost linear relationship between MBF and myocardial extraction.…”

Feasibility of using respiration‐averaged MR images for attenuation correction of cardiac PET/MR imaging

“…The advent of hybrid positron emission tomography (PET)/magnetic resonance (MR) imaging systems has brought the potential of superior diagnostic performance over PET/CT (computed tomography) in certain applications, 1 , 2 , 3 , 4 , 5 including cardiac imaging 6 , 7 , 8 , 9 , 10 . However, respiratory motion can compromise the quantification of cardiac PET data using MR data.…”