PROJECT SUMMARY / ABSTRACT The goal of this R03 study is to conduct a pilot study testing whether the variability in quantitative DCE- MRI measurement of glioblastoma across different scanners will be significantly reduced when the UAB-invented perfusion phantom, P4 (Point-of-care Portable Perfusion Phantom), is used for error correction, leading to better differentiation between pseudo-progression and true-progression. This is an essential step before validating the utility of P4 in an extended multi-site clinical trial. Pseudo-progression is known to be associated with better clinical outcomes, thus pseudo-progression mistaken for true-progression may result in discontinuation of an effective therapy. Pseudo-progression is a local inflammatory reaction caused by irradiation and enhanced by concurrent chemotherapy, which leads to transient increase of blood brain barrier (BBB) permeability. The BBB, however, is also disrupted by neoplasm, thus both pseudo- and true-progressions appear with increased contrast enhancement in MRI, and there are no established techniques to differentiate between them. The contrast- enhancing lesions of pseudo-progression are due to inflammatory BBB disruption, whereas those of true- progression are caused by neoplastic BBB disruption. Thus, true-progression typically presents higher perfusion than pseudo-progression does. DCE-MRI has the potential to differentiate between pseudo- and true- progressions of glioblastoma, as it can assess the blood perfusion with minimal susceptibility artifacts, but the measurement variability remains a major concern. The P4 is small enough to be imaged concurrently in the bore of a standard MRI scanner with a patient, serving as an internal reference to measure and compensate the scanner-dependent variation in quantitating perfusion parameters. The P4 successfully reduces the variability in DCE-MRI measurement of various human tissues in our previous studies. We now hypothesize that the variability in quantitative DCE-MRI measurement of glioblastoma across different scanners will also be significantly reduced when MRI system-driven error is corrected using the P4. In this study, a total of 12 patients with a newly (or enlarged) enhancing glioblastoma after adjuvant chemoradiation therapy will be recruited. Each patient will be imaged with two different 3T MRI scanners within a 3-day period, and the two DCE-MRI measurements will be compared to determine the data reproducibility before and after P4-based error correction and to validate the utility of the P4 for accurate quantitative DCE-MRI measurement of glioblastoma. Also it will be examined whether the differentiation between pseudo- and true-progressions of glioblastoma can be improved in quantitative DCE-MRI measurement when the P4 is used for error correction.