Diagnosis of brain tumors is often delayed, jeopardizing therapeutic outcomes. Improved early diagnosis by conventional magnetic resonance spectroscopy (MRS), in which a unique tumor bio-marker, choline is monitored, is currently limited to larger, untreatable tumors by poor sensitivity. We propose to develop ultra- fast 13C choline magnetic resonance molecular micro-imaging, capable of real-time in vivo monitoring of tumor choline metabolism, PASADENA, a new generation of ultra-sensitive, ultra-fast in vivo MR imaging techniques optimized in our Laboratory for use in oncology, provides an increased signal to noise over 10,000 fold. It is our goal to determine the efficacy of hyperpolarized PASADENA reagents, using ultra-fast multinuclear imaging techniques in rat models of malignant brain tumor. This will be accomplished through the following aims:
Aim 1 : Characterization of hyperpolarization of PASADENA reagents in vitro. 15N-choline, 13C-choline, and 13C-glucose will be polarized and imaged to determine the degree of polarization and confirm depolarization rates from the calculated T1 relaxation times. This will be accomplished using established techniques of polarization transfer and multinuclear imaging in vitro and in vivo in normal rat.
Aim 2 : Determine the uptake and kinetics of each PASADENA reagent in tumors in vivo. Using a conventional 9L brain tumor rat model, 13C and 15N MRI and MRS will be acquired after infusion of the PASADENA reagent. Through defined End-Points, uptake and kinetics for each metabolite will be compared in cross-sectional and longitudinal studies, to establish improved sensitivity of PASADENA compared to conventional MRI and histology.
Aim 3 : Determine the specificity of the PASADENA reagents. 13C and 15N MRI and MRS of PASADENA reagents will be acquired in the more aggressive 9L-VEGF+ rats and tumor localization, uptake, and kinetics will be compared with those measured in Aim 2 to determine the specificity of the parameters and for diagnosis of more aggressive brain tumors. By achieving these aims we expect to open a new era of real-time molecular imaging which when translated for human use will provide earlier diagnosis, staging and therapeutic monitoring and improved long-term survival for patients with malignant brain tumors.
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