Applying Amide Proton Transfer MR Imaging to Hybrid Brain PET/MR: Concordance with Gadolinium Enhancement and Added Value to [18F]FDG PET

Purpose

The purpose of this study is to evaluate the diagnostic concordance and metric correlations of amide proton transfer (APT) imaging with gadolinium-enhanced magnetic resonance imaging (MRI) and 2-deoxy-2-[¹⁸F-]fluoro-D-glucose ([¹⁸F]FDG) positron emission tomography (PET), using hybrid brain PET/MRI.

Procedures

Twenty-one subjects underwent brain gadolinium-enhanced [¹⁸F]FDG PET/MRI prospectively. Imaging accuracy was compared between unenhanced MRI, MRI with enhancement, APT-weighted (APTW) images, and PET based on six diagnostic criteria. Among tumors, the McNemar test was further used for concordance assessment between gadolinium-enhanced imaging, APT imaging, and [¹⁸F]FDG PET. As well, the relation of metrics between APT imaging and PET was analyzed by the Pearson correlation analysis.

Results

APT imaging and gadolinium-enhanced MRI showed superior and similar diagnostic accuracy. APTW signal intensity and gadolinium enhancement were concordant in 19 tumors (100 %), while high [¹⁸F]FDG avidity was shown in only 12 (63.2 %). For the metrics from APT imaging and PET, there was significant correlation for 13 hypermetabolic tumors (P < 0.05) and no correlation for the remaining six [¹⁸F]FDG-avid tumors.

Conclusions

APT imaging can be used to increase diagnostic accuracy with no need to administer gadolinium chelates. APT imaging may provide an added value to [¹⁸F]FDG PET in the evaluation of tumor metabolic activity during brain PET/MR studies.