Comparison of Amino Acid PET to Advanced and Emerging MRI Techniques for Neurooncology Imaging: A Systematic Review of the Recent Studies

Abstract

Introduction. Standard neuroimaging protocols for brain tumors have well-known limitations. The clinical use of additional modalities including amino acid PET (aaPET) and advanced MRI (aMRI) techniques (including DWI, PWI, and MRS) is emerging in response to the need for more accurate detection of brain tumors. In this systematic review of the past 2 years of the literature, we discuss the most recent studies that directly compare or combine aaPET and aMRI for brain tumor imaging. Methods. A PubMed search was conducted for human studies incorporating both aaPET and aMRI and published between July 2018 and August 2020. Results. A total of 22 studies were found in the study period. Recent studies of aaPET with DWI showed a superiority of MET, FET, FDOPA, and AMT PET for detecting tumor, predicting recurrence, diagnosing progression, and predicting survival. Combining modalities further improved performance. Comparisons of aaPET with PWI showed mixed results about spatial correlation. However, both modalities were able to detect high-grade tumors, identify tumor recurrence, differentiate recurrence from treatment effects, and predict survival. aaPET performed better on these measures than PWI, but when combined, they had the strongest results. Studies of aaPET with MRS demonstrated that both modalities have diagnostic potential but MET PET and FDOPA PET performed better than MRS. MRS suffered from some data quality issues that limited analysis in two studies, and, in one study that combined modalities, overall performance actually decreased. Four recent studies compared aaPET with emerging MRI approaches (such as CEST imaging, MR fingerprinting, and SISTINA), but the initial results remain inconclusive. Conclusions. aaPET outperformed the aMRI imaging techniques in most recent studies. DWI and PWI added meaningful complementary data, and the combination of aaPET with aMRI yielded the best results in most studies.

Can High b Value Diffusion Be a Surrogate Marker for PET—A MR/PET Study in Neurooncology Set Up

“…In lesion based sensitivity, the specificity of DWI was comparable with those of PET and in agreement with earlier published studies (5,6).…”

“…Many MR/PET studies correlate with multiple advanced imaging parameters like diffusion-weighted imaging (DWI) and Perfusion weighted imaging (PWI) studies on the grading of gliomas, enabling the prediction of recurrence. It is possible to differentiate recurrence vs. radiation necrosis and the false negative in each modality is known (3)(4)(5)(6). PET also has many tracers, each with its specificity and sensitivity (7)(8)(9)(10).…”

Use of multimodality imaging, histology, and treatment feasibility to characterize a transgenic Rag2-null rat model of glioblastoma

“…In the second published clinical study, 11 C-methionine, another well-characterized amino acid PET agent that utilizes the LAT receptor, was compared with amide-CEST MRI in 43 patients with gliomas in the posttreatment period to determine the diagnostic performance of the two modalities (68). Amide-CEST MRI appears to perform better than 11 C-methionine in distinguishing recurrent disease in high-grade gliomas, although a rationale has been made for the continued use of multimodality imaging to crossreference imaging properties for higher overall diagnostic accuracy (69). The findings of these studies are significant because they suggest that CEST MRI can better define the infiltration of GBM, in particular, and glioma, in general, in the tumor periphery.…”

PET Imaging in Neuro-Oncology: An Update and Overview of a Rapidly Growing Area

“…Most of these studies highlight the fact that the information provided by PET imaging and advanced MRI techniques is not redundant but provides complementary information. Available evidence from the literature calls for better performances of amino acid PET over perfusion MRI to detect high-grade tumors, identify tumor recurrence, differentiate recurrence from treatment effects and predict survival, even though both imaging methods are able to discern these indications to some extent [ 129 ]. The better performances related to the use of amino acid PET are much more appreciated when compared to diffusion MRI or spectroscopy [ 129 ].…”

“…Available evidence from the literature calls for better performances of amino acid PET over perfusion MRI to detect high-grade tumors, identify tumor recurrence, differentiate recurrence from treatment effects and predict survival, even though both imaging methods are able to discern these indications to some extent [ 129 ]. The better performances related to the use of amino acid PET are much more appreciated when compared to diffusion MRI or spectroscopy [ 129 ]. These reported differences do, however, underpin the need for prospective studies on larger cohorts and neuropathological validation to further evaluate the differences between these two imaging systems.…”