AJR July 2018
Stony Brook University School of Medicine
Stony Brook, NY
“Added Value of Including Entire Brain on Body Imaging With FDG PET/MRI”
Routine body imaging with FDG PET/MRI of the area from the skull base to the mid-thigh may miss important brain abnormalities when the head is not included. A study in the July 2018 issue of the American Journal of Roentgenology (AJR) concludes that the additional brain abnormalities identified on whole-body imaging may provide added clinical value to the management of oncology patients.
Researchers led by Robert Matthews, Associate Professor of Radiology, Division of Nuclear Medicine and PET Imaging, at Stony Brook University Hospital, retrospectively identified 269 patients with FDG PET/MRI whole-body scans that included the head. PET/MR images of the brain were reviewed by a nuclear medicine physician and neuroradiologist, first individually and then concurrently. Both PET and MRI findings were identified, including abnormal FDG uptake, standardized uptake value, lesion size, and MRI signal characteristics. For each patient, relevant medical history and prior imaging were reviewed.
Of the 269 subjects, 173 were women and 96 were men (mean age, 57.4 years). Only the initial PET/MR image of each patient was reviewed. A total of 37 of the 269 patients (13.8%) had abnormal brain findings noted on the PET/MRI whole-body scan. Sixteen patients (5.9%) had vascular disease, nine patients (3.3%) had posttherapy changes, and two (0.7%) had benign cystic lesions in the brain. Twelve patients (4.5%) had serious nonvascular brain abnormalities, including cerebral metastasis in five patients and pituitary adenomas in two patients. Only nine subjects (3.3%) had a new neurologic or cognitive symptom suggestive of a brain abnormality.
The authors concluded that the routine PET/MRI protocol that images the area from the skull base to the mid-thigh may miss many important brain abnormalities that are easily detected with PET/MRI body sequences. These abnormalities could change patient management or alter patient prognosis.
The amount of time required to include the entire head was only an additional 3–5 minutes of imaging time for the standard scan covering the skull base to the mid-thigh, and the radiologist needed only 2–3 minutes to review the images. Dedicated brain radiofrequency coils were not required, and no additional radiation was accrued by its implementation. An FDG PET/MRI whole-body scan that includes the head provides added value to the management of these patients.
In this Q&A, Matthews discusses the origin of the study and the outlook for further research.
How did you and your co-authors come up with the idea for this study?
Matthews: When we first started using PET-MR imaging at our facility in Stony Brook, we inquired at many institutions on what their protocols were for various types of studies. What we found out was that there was a wide variety of protocols and MRI sequences being used in PET-MR with no consistency between institutions and even within the same institution.
Although we lacked knowledge in which sequences to use, what we did want to do was to acquire PET-MR imaging starting at the top of the head. At the time we did not know if it would be important, but we had a feeling that even with MRI body sequences, PET-MR with inclusion of the head might show something useful or interesting in the brain that would help patient care. When I first started working in nuclear medicine, there was a year-long debate at the meetings on whether the entire head should be included with PET-CT scans. I don’t think that debate was ever decided, but I think with PET-MR we are closer to an answer.
What should readers take away from your article?
Matthews: Most patients undergoing PET imaging have cancer and are often very sick. These patients have undergone very toxic treatments in the form of radiation therapy and chemotherapy, among other treatments. Brain malignancy and brain pathology occur at a higher rate in these patients than the general population. As physicians, we should make use of all the tools that we have. For PET-MR imaging with inclusion of the entire skull, this required only a few minutes of extra imaging time and reading time.
What recommendations do you have for future research as a result of this article?
Matthews: Using PET-MR is a continuous learning process, not for just the individual physician or institution, but for the nuclear medicine community. I think we are only at the beginning to knowing the full potential of PET-MR imaging especially with the introduction of new non-FDG clinical tracers. With preclinical research, the future is even more promising. Nowadays, look at how fast our technology is changing, a smart phone that is only 10 years old is considered obsolete. PET-MR imaging is still an unrealized field.
Is there anything else you would like to add?
Matthews: PET-MR is still a growing field and there is a lot of interest for good reason. When going to a radiology or nuclear medicine meeting, the session discussing PET-MR are still packed and often standing room only. It is great to see the interest and enthusiasm revolving around PET-MR. I think this will only increase with time.
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