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Semi-quantitative Assessment Using [18F]FDG Tracer in Patients with Severe Brain Injury
Published on: November 9, 2018
Diagnostic approach in suspected recurrent primary brain tumors using (18)FDG-PET/MRI, perfusion MRI, visual and
G Estrada1, L González-Maya, M A Celis-López
1PET-Cyclotron Unit, National Autonomous University of Mexico (UNAM). Mexico. dragiselaus@yahoo.com
Unlabelled:
Thirty patients with primary cerebral tumors WHO III and IV previously treated, undergoing evaluation for tumoral recurrence, they underwent (18)FDG-PET study, MRI and PMRI. PET uptake was determined by visual inspection and was quantified by use of standard uptake values, the ratio of tumor uptake to normal tissue and were z scored using automated voxel-based comparison. PMRI was quantified by use of ratios of cerebral blood volume (rCBV). The accuracies were determined by comparing imaging data with histologic findings and clinical follow up of up to 21 mo.
Results:
Sensitivity (Se), specificity (Sp), positive predictive value (PPV), negative predictive value (NPV) and accuracy were 100 %, 82 %, 90 %, 100 % and 93 % respectively for the PET/MRI fusion and 68 %, 82 %, 87 %, 60 % and 73 % respectively for PMRI. There were two false positive cases for PET/MRI fusion that were confirmed by biopsy: chronic inflammation; and foreign body granulomas. The receiver operating characteristic (ROC) curve analysis showed statistically significant difference (p = 0.0225).
Conclusions:
(18)FDG SUVs, glucose uptake ratios and 3D stereotactic surface projections in brain tumors were not a reliable measure for evaluating recurrent tumors. PET/MRI fusion was more sensitive and accurate than PMRI for imaging recurrent primary brain tumors. The region of interest can be visually analyzed on the PET/MRI fusion images and described as recurrent tumor when any activity (lower, equal or greater than the contralateral cortex) is presented in the zone of hyperintensity seen on the post-gadolinium T1-weighted MRI.
Insights
PET/MRI fusion is a more sensitive and accurate imaging method for detecting recurrent brain tumors compared to perfusion MRI alone. Standard uptake values from (18)FDG PET are unreliable for evaluating tumor recurrence.
Area of Science:
- Neuro-oncology
- Medical Imaging
- Nuclear Medicine
Background:
- Evaluating tumoral recurrence in primary cerebral tumors (WHO III and IV) is critical for patient management.
- Previous treatments necessitate reliable methods to distinguish recurrent tumors from treatment effects.
Purpose of the Study:
- To compare the diagnostic accuracy of (18)FDG-PET/MRI fusion and perfusion MRI (PMRI) in identifying recurrent primary brain tumors.
- To assess the utility of standard uptake values (SUVs) and glucose uptake ratios in evaluating tumor recurrence.
Main Methods:
- Thirty patients with treated primary cerebral tumors underwent (18)FDG-PET, MRI, and PMRI.
- PET uptake was assessed visually and quantitatively (SUVs, ratios, z-scores).
- PMRI was quantified using ratios of cerebral blood volume (rCBV). Imaging data were compared with histologic findings and clinical follow-up.
Main Results:
- PET/MRI fusion demonstrated high sensitivity (100%) and accuracy (93%), outperforming PMRI (Se 68%, accuracy 73%).
- PET/MRI fusion showed a statistically significant difference in ROC curve analysis (p=0.0225).
- Two false positive cases for PET/MRI fusion were biopsy-confirmed as chronic inflammation and foreign body granulomas.
Conclusions:
- (18)FDG SUVs and related metrics are unreliable for evaluating recurrent brain tumors.
- PET/MRI fusion is a more sensitive and accurate imaging modality than PMRI for recurrent primary brain tumors.
- Recurrent tumors can be identified on PET/MRI fusion by visual analysis of activity within MRI-defined hyperintense regions.
