Amino-acid PET imaging of gliomas in the spotlight

Kathy Mahdoubi | | Health Imaging | Molecular Imaging

Amino-acid biomarkers have undergone an evolution in the imaging of gliomas. Several agents have shown to be particularly useful, most notably C-11 MET, F-18 FDOPA, FLT and FET, according to a review of amino-acid imaging published July 8 in the Journal of Nuclear Medicine.

Wolf-Dieter Heiss, MD, PhD, director of the department of neurology at the University of Cologne and also from the department of general neurology at the Max-Planck-Institute for Neurlogical Research, Cologne, provided a breakdown of the current research.

“In summary, with the availability of tracers with longer half-lives, molecular imaging has gained broader access to the management of brain tumors, but its utilization is still more limited in brain oncology than in general oncology,” wrote Heiss. “Compared with CT or MR imaging, amino acid PET permits more precise demarcation of tumors, better definition of malignancy and prognosis, and earlier detection of recurrences. Additionally, amino acid PET can be used to monitor the effects of treatment and to allow early differentiation between responders and nonresponders.”

FDG was the first agent used for amino-acid imaging of gliomas, but Heiss noted that a major difficulty with FDG is non-specific uptake in the brain. C-11 methionine (MET) is the most commonly used agent and it has been found to be very sensitive to imaging not only solid tumors but the infiltration zone, though its short half-life limits its appeal for institutions that do not house a cyclotron. F-18 FET has been shown to differentiate tumor subtypes as well as high- and low-grade gliomas. FDOPA has also been shown to be highly sensitive and specific, but particularly for newly diagnosed gliomas as a sign of proliferating disease. FDOPA may even be superior to FLT for low-grade gliomas.

Amino-acid imaging may be an application well suited for simultaneous PET/MR imaging, indicated Heiss. F-18 FET PET in particular has been found to be superior when coregistered with MR as compared to MR alone. FET PET/MR has been shown to reach a sensitivity of more than 80 percent and a specificity of nearly 100 percent.

“Integrated PET/MR imaging might become the gold standard for diagnosis of gliomas in the future,” concluded Heiss.

Kathy Mahdoubi

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