MR can be employed for PET attenuation correction, and PET/MR assessment for cardiac muscle viability delivered comparable results to PET acquired using PET/CT, according to research presented at the annual meeting of the Society of Nuclear Medicine and Molecular Imaging (SNMMI) in Vancouver.
Since the development of PET/MR, researchers have recognized its potential value in cardiac imaging, given that the hybrid system weds the highly sensitive soft tissue contrast of MR with the functional and metabolic imaging of PET. However, translating potential to practice requires an understanding of how MR attenuation correction compares with CT.
Jeffery M. C. Lau, MD, PhD, from Washington University in St. Louis, and colleagues devised a study to examine the feasibility of MR attenuation correction in cardiac-gated FDG PET.
The researchers enrolled 31 patients with no history of heart problems undergoing PET/CT and PET/MR for oncologic indications.
MR attenuation correction was performed via a specialized dual-echo MR sequence that orders radiofrequency magnetic fields interacting with atomic nuclei in the body to discriminate between water and fat.
The researchers measured the uptake of FDG in the myocardium by reviewing a cross section of the left ventricle and reported an average measurement of 4.68 for PET/MR and 4.62 for PET/CT. The nearly identical measurements advance cardiac PET/MR toward clinical applications, such as imaging scarring of heart tissue and subsequent complications after cardiac arrest.
“Our research provides the groundwork for future research in cardiac PET/MR imaging,” Lau said in a press release. “PET/MR provides powerful cardiac imaging and requires a lower radiation dose than PET/CT. Also, the MRI component, which can be acquired simultaneously, provides excellent heart muscle signal for imaging scar tissue caused by heart attacks. In particular, our group is most interested in applying the PET/MR technology to evaluate the likelihood of arrhythmia or irregular heart beat development in patients who have had heart attacks.
“Our hope is that in the future PET/MR will become the imaging modality of choice for certain cardiac diseases,” Lau continued. “One potential use of cardiac PET/MR is to guide the patient selection process when deciding if patients who have suffered ischemic cardiomyopathy are good candidates for cardiac defibrillator implantation. We hope that a better understanding of the metabolic and anatomic correlation of PET/MR in the myocardial scar and scar border can provide more insight into arrhythmias that lead to sudden cardiac death.”
Studies have indicated that implanted cardiac defibrillators are related to the development of ventricular arrhythmias in up to one-third of implanted patients within three years.