Abstract
597
Objectives Typical FDG PET-CT imaging for oncology is performed from the base of the skull to the mid thighs. Both benign and malignant brain findings can occur in the oncology patient that would be missed on the typical PET scan. In our institution, when we perform whole body PET-MRI for cancer patients, we routinely include the entire head. In this retrospective study, we wished to characterize both PET and MRI brain findings that we encountered on the included head portion.
Methods We retrospectively identified 192 FDG PET-MRI body imaging that included the head. Images were obtained on a dedicated PET-MRI camera with simultaneous acquisition. Images were obtained using a body coil without IV contrast and sequences were tailored for body pathology. Of these studies, there were 168 patients, 99 female and 69 male, in which we reviewed only the patient’s first PET-MRI body studies acquired at our institution. The mean age of these 168 patients was 52 years with range 7-89. 156 studies were for cancer assessment with 62 staging and 94 restaging. The other 12 studies included 4 paraneoplastic evaluation, 3 adenopathy, 3 lung nodule evaluation, 1 vasculitis, and 1 IgG4 disease. Of the 12 studies, 3 were later diagnosed to have cancer. Images of the brain were reviewed by a neuroradiologist in conjunction with a nuclear radiologist. Lesions were characterized based on both MRI and PET findings. A chart review was performed.
Results Of the 168 patients, 27 patients (16.1 %) had positive brain findings on PET-MRI body sequences. 10 (6.0%) had vascular disease (mean age 68 yrs) with 6 showing chronic microvascular ischemic changes and 4 had brain infarcts. One of the infarcts was a subacute stroke in a paraneoplastic patient. The average age of vascular disease was 68 yr with one newly discovered infarct in a 38 yr female. The detection rate for microvascular ischemic changes was likely lower due to the body MRI sequences. 6 patients had post therapy changes in the brain due to either radiation or surgery. There were 5 with benign lesions (mean age 41 yrs) include 2 perivascular space lesions, 2 probable chemotherapy changes, and 1 benign cystic mass. 6 had more serious brain pathologies including the 3 other paraneoplastic patients (leptomeningeal thickening with FDG cortical changes, metabolic encephalopathy, Creutzfeld-Jakob disease), 2 pituitary tumors, and 1 chronic subdural collection. Patients with more serious findings including the subacute infarct composed 4.2% with mean age 67 yrs. No incidental metastatic lesions were detected.
Conclusions FDG PET-MRI imaging is a rapidly evolving modality that is most commonly employed for cancer evaluation. The standardized base of skull to mid thigh imaging may miss many important pathologies that are discovered even with MRI body sequences. We propose that PET-MRI body sequences that include the head may show added value in the management of patients.