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Published on: November 9, 2018
Assessment of Brain Tumour Perfusion Using Early-Phase 18F-FET PET: Comparison with Perfusion-Weighted MRI
Christian P Filss1,2,3, Julian Cramer4,5, Saskia Löher4,5
1Department of Nuclear Medicine, RWTH University Hospital, Aachen, Germany. c.filss@fz-juelich.de.
Purpose:
Morphological imaging using MRI is essential for brain tumour diagnostics. Dynamic susceptibility contrast (DSC) perfusion-weighted MRI (PWI), as well as amino acid PET, may provide additional information in ambiguous cases. Since PWI is often unavailable in patients referred for amino acid PET, we explored whether maps of relative cerebral blood volume (rCBV) in brain tumours can be extracted from the early phase of PET using O-(2-18F-fluoroethyl)-L-tyrosine (18F-FET).
Procedure:
Using a hybrid brain PET/MRI scanner, PWI and dynamic 18F-FET PET were performed in 33 patients with cerebral glioma and four patients with highly vascularized meningioma. The time interval from 0 to 2 min p.i. was selected to best reflect the blood pool phase in 18F-FET PET. For each patient, maps of MR-rCBV, early 18F-FET PET (0-2 min p.i.) and late 18F-FET PET (20-40 min p.i.) were generated and coregistered. Volumes of interest were placed on the tumour (VOI-TU) and normal-appearing brain (VOI-REF). The correlation between tumour-to-brain ratios (TBR) of the different parameters was analysed. In addition, three independent observers evaluated MR-rCBV and early 18F-FET maps (18F-FET-rCBV) for concordance in signal intensity, tumour extent and intratumoural distribution.
Results:
TBRs calculated from MR-rCBV and 18F-FET-rCBV showed a significant correlation (r = 0.89, p < 0.001), while there was no correlation between late 18F-FET PET and MR-rCBV (r = 0.24, p = 0.16) and 18F-FET-rCBV (r = 0.27, p = 0.11). Visual rating yielded widely agreeing findings or only minor differences between MR-rCBV maps and 18F-FET-rCBV maps in 93 % of the tumours (range of three independent raters 91-94%, kappa among raters 0.78-1.0).
Conclusion:
Early 18F-FET maps (0-2 min p.i.) in gliomas provide similar information to MR-rCBV maps and may be helpful when PWI is not possible or available. Further studies in gliomas are needed to evaluate whether 18F-FET-rCBV provides the same clinical information as MR-rCBV.
Insights
Early 18F-FET PET scans can generate relative cerebral blood volume (rCBV) maps comparable to MRI-based perfusion-weighted imaging (PWI). This offers a valuable alternative for brain tumor diagnostics when PWI is unavailable.
Area of Science:
- Neuroimaging
- Oncology
- Radiochemistry
Background:
- Morphological MRI is crucial for brain tumor diagnosis.
- Dynamic susceptibility contrast (DSC) perfusion-weighted MRI (PWI) and amino acid PET offer complementary diagnostic information.
- PWI is frequently unavailable for patients undergoing amino acid PET scans.
Purpose of the Study:
- To investigate the feasibility of extracting relative cerebral blood volume (rCBV) maps from the early phase of O-(2-18F-fluoroethyl)-L-tyrosine (18F-FET) PET.
- To compare 18F-FET derived rCBV (18F-FET-rCBV) maps with MR-based rCBV (MR-rCBV) maps in patients with gliomas and meningiomas.
Main Methods:
- Utilized a hybrid PET/MRI scanner for simultaneous PWI and dynamic 18F-FET PET in 37 patients.
- Generated MR-rCBV, early (0-2 min p.i.) 18F-FET PET, and late (20-40 min p.i.) 18F-FET PET maps.
- Analyzed correlations between tumour-to-brain ratios (TBRs) and performed visual concordance assessments of MR-rCBV and 18F-FET-rCBV maps.
Main Results:
- A significant correlation was found between TBRs from MR-rCBV and 18F-FET-rCBV (r = 0.89, p < 0.001).
- No significant correlation was observed between late 18F-FET PET TBRs and MR-rCBV or 18F-FET-rCBV.
- Visual evaluation showed high agreement between MR-rCBV and 18F-FET-rCBV maps in 93% of tumors.
Conclusions:
- Early 18F-FET PET maps provide information comparable to MR-rCBV maps for glioma assessment.
- 18F-FET-rCBV may serve as a valuable alternative when PWI is not accessible.
- Further research is warranted to confirm the clinical utility of 18F-FET-rCBV in comparison to MR-rCBV.
