Room: AAPM ePoster Library
Purpose: To measure the tumour oxygenation following VEGF ablation-induced changes in tumour models using dynamic oxygen-enhanced MRI (dOE-MRI) and independent component analysis.
Methods: Mice were implanted with SCCVII murine squamous cell carcinoma tumors in the dorsal subcutaneous region. Mice (n=8) were treated with 5mg/kg mouse anti-VEGF antibody (bevacizumab) 48h prior to imaging. Imaging was performed using a 7T scanner (Tx: quadrature volume coil Rx: custom-built surface receive coil). dOE- MRI scans were acquired using 2D FLASH with TE/TR=2.67/133, NR=90, a=40, 16 slices each 1mm thick, FOV of 3.84cm x 2.16 cm, matrix=128x72, and a temporal resolution of 9.6s for a total scan time of about 14 minutes. Tumour ROIs were outlined on a RARE image. While imaging, breathing gas was alternated between medical air and 100% oxygen every 2 minutes using a 3-channel gas mixer (CWE, Philadelphia, USA) for a total of 3 air-oxygen-air cycles. The signal changes were detected using independent component analysis (ICA). ICA is a blind-source separation algorithm that separates multiple signal sources by maximizing statistical independence of individual components. The normalized component weighting factor (NCWF) is the primary metric for assessing tumour oxygenation.
Results: Treatment of SCCVII tumours with the anti-angiogenic agent bevacizumab resulted in an increased oxygenation compared to untreated controls. Eight control tumours had a mean NCWF value of 0.037±0.011 and nine treated tumours had a mean of 0.094±0.037. This difference was statistically significant and the effect size was large with Hedge's g=1.08. However, considerable heterogeneity was observed between mice and within a single slice.
Conclusion: We showed that dOE-MRI detects change in tumour oxygenation following VEGF ablation therapy in SCCVII tumours. These changes to the tumour microenvironment are quantitatively assessed by applying ICA to the data.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by NSERC and CIHR.