Gliomas: Motexafin Gadolinium-enhanced Molecular MR Imaging and Optical Imaging for Potential Intraoperative Delineation of Tumor Margins.

PURPOSE To investigate the possibility of using motexafin gadolinium (MGd)-enhanced molecular magnetic resonance (MR) imaging and optical imaging to identify the true margins of gliomas. MATERIALS AND METHODS The animal protocol was approved by the institutional animal care and use committee. Thirty-six Sprague-Dawley rats with gliomas were randomized into six groups of six rats. Five groups were euthanized 15, 30, 60, 120, and 240 minutes after intravenous administration of 6 mg/kg of MGd, while one group received only saline solution as a control group. After craniotomy, optical imaging and T1-weighted MR imaging were performed to identify the tumor margins. One-way analysis of variance was used to compare optical photon intensity and MR imaging signal-to-noise ratios. Histologic analysis was performed to confirm the intracellular uptake of MGd by tumor cells and to correlate the tumor margins delineated on both optical and MR images. RESULTS Both optical imaging and T1-weighted MR imaging showed tumor margins. The highest optical photon intensity (2.6 × 10(8) photons per second per mm(2) ± 2.3 × 10(7); analysis of variance, P < .001) and MR signal-to-noise ratio (77.61 ± 2.52; analysis of variance, P = .006) were reached at 15-30 minutes after administration of MGd, with continued tumor visibility at 2-4 hours. Examination with confocal microscopy allowed confirmation that the fluorescence of optical images and MR imaging T1 enhancement exclusively originated from MGd that accumulated in the cytoplasm of tumor cells. CONCLUSION MGd-enhanced optical and MR imaging can allow determination of glioma tumor margins at the optimal time of 15-120 minutes after administration of MGd. Clinical application of these results may allow complete removal of gliomas in a hybrid surgical setting in which intraoperative optical and MR imaging are available.