Development of MRF for Characterization of Brain Tumors After Radiotherapy

Although Stereotactic radiosurgery (SRS) is utilized as an effective treatment method, after several months to over 1 year following SRS, 33% of treated brain metastases increase in size on imaging, which is suspicious for tumor progression. However, based on findings in follow-up biopsies, the majority of newly detected metastases on imaging are radiation treatment effects instead of active tumor. So far, the only gold standard to differentiate active tumor and radiation necrosis is surgical resection for pathologic confirmation, which is invasive, not favored for poor surgical candidates, and should be avoided in cases of necrosis. The existing clinical imaging techniques have poor sensitivity or specificity in differentiating these two types of tissues. Recently, a novel MRI data acquisition approach, namely MR Fingerprinting (MRF), has been introduced for the simultaneous measurement of multiple important parameters in a single MRI scan. In addition, quantitative diffusion MRI, such as the intravoxel incoherent motion (IVIM) technique, can provide a noninvasive and powerful tool to quantify microstructural information by measuring water diffusion and microcirculation perfusion in vivo. This study aims to demonstrate the clinical feasibility of combining MRF with state-of-the-art parallel imaging techniques to achieve high-resolution quantitative imaging within a reasonable scan time of 5 min for whole brain coverage. It also aims to apply the developed quantitative approach in combination with IVIM MRI for the differentiation of tumor recurrence and radiation necrosis. The multi-parametric quantitative measures developed in this study could establish a new fundamental biomarker for the diagnosis and monitoring of brain tumors.