Evaluating the Diagnostic Efficacy of 99mTc-Methionine Single-Photon Emission Computed Tomography-Computed Tomography: A Head-to-Head Comparison with 11C-Methionine Positron Emission Tomography-Magnetic Resonance Imaging in Glioma Patients.

Background: Amino acid positron emission tomography (PET) imaging plays a significant role in the diagnosis of gliomas and in differentiating tumor recurrence from necrosis. In this study, the authors evaluated the diagnostic efficacy of [^99mTc]Tc-methionine single-photon emission computed tomography-computed tomography (SPECT-CT) in comparison with [¹¹C]methionine PET-magnetic resonance imaging (MRI) in delineating tumors. Methods: Thirty-one (primary: 16 and postoperative: 15) patients of confirmed (either MRI or histopathological proven) glioma underwent both [^99mTc]Tc-methionine SPECT-CT and [¹¹C]methionine PET-MRI. A comparative analysis was performed between SPECT, PET, and MR images to calculate the concordance between the modalities and to evaluate the diagnostic efficacy of the [^99mTc]Tc-methionine SPECT. Results: [^99mTc]Tc-methionine SPECT showed comparable uptake in the tumor lesions in comparison to [¹¹C]methionine PET. A significant and strong positive correlation was observed between the volume of tumor (Vt) in PET and Vt MR (p < 0.004). Likewise, a significant and strong positive correlation was found between Vt SPECT and Vt MR. [^99mTc]-methionine has a sensitivity and specificity of 91% and 75%, respectively, compared with 82% and 100% for [¹¹C]methionine in postoperative cases to differentiate the tumor recurrence from necrosis. The sensitivity and specificity of [^99mTc]Tc-methionine was 92% and 100%, respectively, compared with 92% and 67% for [¹¹C]methionine in primary tumors. Conclusion: [^99mTc]Tc-methionine SPECT-CT is as equally good as [¹¹C]methionine for diagnosing and differentiating it from necrosis especially in high-grade glioma.