Stereotactic radiosurgery-induced changes in brain metastasis patients within two weeks after therapy detected using multi-parametric qMRI

Motivation: Pre-operative stereotactic radiosurgery (SRS) is routinely included in brain metastases (BM) treatment. Early changes in tumor/surrounding tissue after SRS could predict patient outcome but have rarely been reported. Goal(s): Examine early (<2 weeks) qualitative (weighted-images) and quantitative (multi-parametric qMRI) changes in BM after pre-operative SRS. Approach: Six patients were scanned before and after SRS with a standardized Brain Tumor Imaging (BTIP) and mp-qMRI protocol. Results: Contrast-enhanced tumor mask volumes increased for most patients. The oedema-mask volumes, decreased for 50% and increased for 50% of the total patients. Volume changes corresponded to changes in qMRI. qMRI changes did not significantly correlate with radiation dose. Impact: Results demonstrate that qualitative and quantitative (qMRI) changes are detectable in MR scans of BM patients even within two weeks after SRS. The effects of SRS are not dose dependent and may have predictive value for treatment outcome.