The recent introduction of hybrid PET/MRI scanners in clinical practice has shown promising initial results for several clinical scenarios. However, the first generation of combined PET/MRI lacks time-of-flight (TOF) technology. Here we report the results of the first patients to be scanned on a completely novel fully integrated PET/MRI scanner with TOF.
We analyzed data from patients who underwent a clinically indicated 18F FDG PET/CT, followed by PET/MRI. Maximum standardized uptake values (SUVmax) were measured from 18F FDG PET/MRI and 18F FDG PET/CT for lesions, cerebellum, salivary glands, lungs, aortic arch, liver, spleen, skeletal muscle, and fat. Two experienced radiologists independently reviewed the MR data for image quality.
Thirty-six patients (19 men, 17 women, mean [±standard deviation] age of 61 ± 14 years [range: 27–86 years]) with a total of 69 discrete lesions met the inclusion criteria. PET/CT images were acquired at a mean (±standard deviation) of 74 ± 14 minutes (range: 49–100 minutes) after injection of 10 ± 1 mCi (range: 8–12 mCi) of 18F FDG. PET/MRI scans started at 161 ± 29 minutes (range: 117 – 286 minutes) after the 18F FDG injection. All lesions identified on PET from PET/CT were also seen on PET from PET/MRI. The mean SUVmax values were higher from PET/MRI than PET/CT for all lesions. No degradation of MR image quality was observed.
The data obtained so far using this investigational PET/MR system have shown that the TOF PET system is capable of excellent performance during simultaneous PET/MR with routine pulse sequences. MR imaging was not compromised. Comparison of the PET images from PET/CT and PET/MRI show no loss of image quality for the latter. These results support further investigation of this novel fully integrated TOF PET/MRI instrument.
From the *Division of Nuclear Medicine and Molecular Imaging, Stanford University Medical Center; †Stanford University Medical Center, Molecular Imaging Program at Stanford (MIPS); ‡Stanford University Medical Center, Department of Radiology; §Stanford University Medical Center, Departments of Radiology, Bioengineering, Materials Science and Engineering, Molecular Imaging Program at Stanford (MIPS), Stanford, CA.
Received for publication August 6, 2014; revision accepted September 3, 2014.
Conflicts of interest and sources of funding: none declared.
Reprints: Andrei Iagaru, MD, Division of Nuclear Medicine and Molecular Imaging, Stanford University Medical Center, 300 Pasteur Dr, Room H-0101, Stanford, CA 94305 USA. E-mail: firstname.lastname@example.org.