Delta T1 (dT1) method as a tool to evaluate tumor progression in patients with brain cancer.

Abstract

e21056 Background: Evaluation of pre- and post-contrast T1-weighted images is the primary approach to monitoring patients with brain tumors. The pre-contrast images are used to distinguish enhancing lesions on the post-contrast images from other sources of bright signal such as subacute hemorrhage or protein-containing fluid, which appear bright on the T1-weighted pre-contrast image. However, in some cases additional enhancement observed on the post-contrast images, above and beyond the brightness observed on the pre-contrast images, can be quite subtle and thus difficult to detect by direct inspection. Methods: As a solution we have developed an automatic method, the delta T1 (dT1) method, for selection of regions of interest by creating difference maps between standardized pre- and post-contrast T1-weighted images. The dT1 method is a fast, reliable and objective method to detect even subtly enhancing tumors free of blood products. Results: In this study we report the use of technique, dT1 method, for two main applications: a) Detection of tumor residual upon surgery: The dT1 method can aid in distinguishing blood products from residual tumor. b) Early detection of tumor recurrence: The dT1 is highly sensitive to even subtle changes in post-contrast images that can be missed by direct inspection. This condition occurs more frequently with the increasing use of anti-angiogenic agents which make it increasingly difficult to monitor patients with brain tumors simply by visually comparing differences in enhancement. Conclusions: We calculated dT1 maps for patients and correlated dT1 results with time to progression as seen on clinical scans. For all cases for which the dT1 maps were suggestive of the presence of tumor the time to progression was much shorter (3-7 months) compared to dT1 maps with a negative (-) ROI status. We therefore conclude that dT1 method has the potential to serve valuable tool for monitoring patients over time. Patient No. Gender Age Diagnosis dT1 map (ROI status) Time to progression 1 M 50 Glioblastoma + 5 months 2 F 65 Glioblastoma + 3 months 3 F 67 Anaplastic oligodendroglioma + 7 months 4 M 45 Astrocytoma + 4 months 5 M 60 Anaplastic oligoastrocytoma + 3 months 6 F 53 Glioblastoma - 18 months 7 F 41 Oligodendroglioma - 13 months