NI-08 OPTIMIZATION OF MOLECULAR MR IMAGING OF GLIOMA

BACKGROUND: MRI has been widely recognized as a diagnostic tool for early cancer detection, treatment monitoring and image guided surgery. Of particular interest is imaging of high-grade gliomas due to their rapid growth and very poor prognosis with a median survival rate of only 9 months. Standard contrast enhanced MRI, not provide sufficiently high specificity for tumor diagnosis and thus require targeted contrast agents which can be applied to provide information on tumor status. Therefore we applied targeted contrast agents based on iron oxide, that shorten mostly T2 relaxation time. The aim of this study was to optimize contrast-to-noise ratio (CNR) using spin-echo (SE), gradient echo (GE) and GE with flow compensation (GEFC) pulse sequences in T2 contrast-enhanced molecular MRI of glioma. METHODS: A mouse model of glioma and 9.4T MRI were used. MR imaging was performed. The CNR was measured prior, 20 min, 2 hrs and 24 hrs post intravenous tail administration of the glioma targeted paramagnetic nanoparticles (NPs) using spin-echo (SE), gradeint-ech (GE), gradient-echo flow compensation (GEFC) pulse sequences. Susceptibility weighted images (SWI) based on GEFC were also obtained for comparison. RESULTS: The results showed significant differences in CNR among all pulse sequences prior injection. GEFC provided higher CNR post contrast agent injection when compared to GE and SE. Post injection CNR was the highest with SWI and significantly different from any other pulse sequence. The optimum CNR was found to be TE = 7 ms for GE and GEFC pulse sequences and TE = 60 ms for SE. CONCLUSION: The study showed, that molecular MR imaging using targeted contrast agents can enhance the detection of glioma cells at 9.4T if the optimal pulse sequence is used. Hence, the use of flow compensated pulse sequences, beside SWI, should to be considered in the molecular imaging studies.