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Developing a Statistical Method of Quantifying Vascular Response after Radiotherapy

Developing a Statistical Method of Quantifying Vascular Response after Radiotherapy. Supervised by Dr. Glenn Bauman and Dr. Slav Yartsev. Michal Stankiewicz Medical Biophysics 3970Z Western University March 26, 2013. Purpose and Motivation. Brain Cancer Survival Radiotherapy technology

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Developing a Statistical Method of Quantifying Vascular Response after Radiotherapy

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  1. Developing a Statistical Method of Quantifying Vascular Response after Radiotherapy Supervised by Dr. Glenn Bauman and Dr. Slav Yartsev Michal Stankiewicz Medical Biophysics 3970Z Western University March 26, 2013

  2. Purpose and Motivation • Brain Cancer Survival • Radiotherapy technology • Vascular response after radiotherapy on glioma tumours • CT perfusions scans before and after radiotherapy • Physiological information Coleman. M.P, et al, Trends and socioeconomic inequalities in cancer survival in England and Wales up to 2001. Br J Cancer, 2004. 90(7): p.1367-73.

  3. Purpose and Motivation • Highly heterogeneous after treatment • Averaging response may not show a difference • Waste of data Pre • Parametric Response Map (PRM) • Voxel-by-voxel analysis • Good predictor of patient survival Post Galbán C.J., Ross B.D., et al. Nat Med, 2009;15(5):572-576

  4. Statistically quantifying voxels • increased or decreased based on threshold • tumour region of interest Objective

  5. Tumour regions will show lower vascular function after radiotherapy • Blood volume • Blood flow • Permeability-surface area product (PS) Hypothesis

  6. How CT Perfusion Works • Tracer kinetics • Iodinated contrast agent injected • Serial CT images of each section • Subtraction of baseline intensity • Time-enhancement curve for each pixel Courtesy of Timothy Yeung Lee, T. Trends in Biotechnology, 2002;20(8):S3-S10

  7. TDC Example Courtesy of Timothy Yeung

  8. Parametric Maps Blood Flow Blood Volume PS Pre Post

  9. Methods

  10. Methods

  11. Methods • Contour normal brain

  12. Methods - = Pre Post Difference map for PS (Pre - Post) • Upper and lower thresholds • Using pre treatment image to contour tumour ROI

  13. Results BV difference in normal brain Lower 5th percentile Upper 95th percentile

  14. Results Increased PS No difference Decreased PS Parametric response map of PS • Showing pixels that significantly decreased, increased and no difference in PS

  15. Results Response: Decreased PS in tumour ROI Response: Increased PS in tumour ROI No difference in tumour ROI response

  16. Responses PS Response Pre Map Post Map PRM SRS14 Decrease SRS12 No change Increase D4

  17. Future Work • Repeat for blood volume and flow • Peri-tumoural region Pre Post

  18. Thank you.

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