Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT) Imaging

Single photon emission computed tomography (SPECT) and positron emission tomography (PET) imaging of brain tumors continues to evolve and expand as new radiopharmaceuticals become available. Currently, two core tracer compounds, thallium-201 and technetium-99m methoxyisobutylisonitrile (MIBI), are widely available for single photon imaging with SPECT. While PET technology is also widely available, at the present time [¹⁸F]fluorodeoxyglucose (FDG) is the only PET tracer which is approved for oncological imaging in the United States by the Food and Drug Administration. Adoption of new tracer compounds such as [¹²³I]iodo-α-methyltyrosine for SPECT and [¹¹C]methyl-methionine (MET), [¹⁸F]fluoroethyl-l-tyrosine (FET), and [¹⁸F]fluorothymidine (FLT) for PET, is hindered by a morass of regulatory and economic complexity. These compounds, however, provide valuable information and in some cases have been shown to be superior to [¹⁸F]FDG.For SPECT or PET to be viable clinical or research tools for imaging of brain tumors, they must provide information that cannot be obtained by other imaging modalities, primarily MRI. The pertinent information expected to be obtained from SPECT or PET imaging of brain tumors relates to whether: (1) tracer uptake correlates with tumor histological grade and hence tracer uptake may be used as a diagnostic or prognostic indicator; and (2) tracer uptake can be used to indicate postoperative tumor recurrence or it can distinguish between tumor recurrence and radiation necrosis. In the present chapter, the current status of SPECT and PET imaging of brain tumors is summarized with an overview of new radiopharmaceuticals and future research directions.