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Dynamic Oxygen-Enhanced MRI (dOE-MRI): A Method to Detect Tumour Oxygenation Changes After VEGF-Ablation Therapy

F Moosvi1*, JHE Baker2, AI Minchinton2, SA Reinsberg1, (1) The University of British Columbia, Vancouver, BC, CA, (2) BC Cancer Research Centre, Vancouver, BC, CA

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

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.

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Funding Support, Disclosures, and Conflict of Interest: This work was supported by NSERC and CIHR.

Keywords

Hypoxia, High-field NMR, Image Analysis

Taxonomy

IM- MRI : Development (New technology and techniques)

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