Aaron Fenster


Imaging Director

Why I Became a Scientist

No other profession would provide me with the freedom and opportunities to generate new techniques and technology and allow development of the ideas to a point where they can be translated into clinical practice and the commercial sector.

Research Summary

My research is focused on 2 broad research programs: Vascular Imaging and Image Guidance in Oncology. My research program spans the spectrum from idea generation to translation to the clinic and to the private sector.  We have generated numerous publications and inventions, which have advanced the state of knowledge in the field and are used worldwide in diagnosis and management of human diseases.

Prostate Cancer: We are focused on improved methods to manage patients with possible prostate cancer: (a) diagnose clinically relevant cancers at a stage when they are curable, (b) stage the disease accurately, and (c) apply appropriate therapy accurately to optimize destruction of cancer cells while preserving normal tissues.

Carotid atherosclerosis: We are developing and validating cost-effective, non-invasive and direct measurements of carotid atherosclerotic plaque to use as efficacy targets for treatment and for more accurately stratifying risk. To meet this challenge, we invented and developed a 3D carotid ultrasound imaging technology, which provides cost-effective and sensitive atherosclerosis measurement tools that are critically needed to define novel risk factors that aggravate atherosclerosis, and to assess efficacy of therapies for carotid atherosclerosis. 

Research Questions

The current prostate biopsy procedure is suboptimal as cancerous lesions are not usually visualized in ultrasound.  Thus, the false negative biopsy rate for cancer can be as high as 34%.  We are developing a system to allow recording of the biopsy location for improved planning for the subsequent therapy, and allow registration with other modalities to help guide the biopsy.

Upon the successful completion of our research, ultrasound-guided prostate biopsy will be less operator-dependent, more reproducible, have improved positive yield on the first biopsy, and improved planning and guidance on repeat biopsy. This would represent a major improvement over current practice. In addition, the tools developed here could also be adapted to 3D US-guided biopsy of other organs such as the liver and breast. Based on our earlier experience with 3D ultrasound-guided prostate cryosurgery and brachytherapy, these innovations could be used routinely clinically within about 2 years after completion of the prototype development.

Better ways to identify patients with increased risk for stroke, and better ways to treat and monitor these patients will have an enormous impact. We are developing 3D carotid ultrasound imaging that can provide cost-effective, sensitive and specific atherosclerosis measurement tools, which are critically needed to define novel risk factors that aggravate atherosclerosis, and to assess efficacy and safety of therapies for carotid atherosclerosis.

Our goal is to make 3D carotid ultrasound a routine and reproducible tool for physicians monitoring their patients for carotid plaque progression/regression in response to therapy, and for quantifying changes in carotid atherosclerosis in clinical trials. Our tools will be used: i) to help identify the important factors that will distinguish patients who have vulnerable plaques; ii) to provide a cost-effective and sensitive method to assess carotid plaque progression and regression; iii) to provide useful information of the response of plaques to plaque stabilization therapies, and iv) to provide validated and reproducible biologic endpoints for therapeutic trials that could significantly reduce the sample sizes required to achieve statistical significance.

Advances in imaging with the potential to identify all prostate lesions, and improvements in biopsy techniques, have allowed physicians to consider the option of a properly executed focal ablative prostate cancer therapy on rigorously selected patients.  This therapy approach could provide definitive management with minimal treatment-related morbidity.

Our research promises to provide an accurate 3D ultrasound and MRI-guided focal prostate therapy system with  improved planning and guidance, and allow patients with enlarged prostates to be treated. This would represent a major improvement over current practice as the improved targeting and needle guidance with combined 3D TRUS and MR images would allow accurate and precise cancer foci to be targeted.  Thus, technology would provide a viable option for patients who are candidates for focal prostate cancer ablation with its reduced treatment morbidity.


  • Ph.D., University of Toronto, Toronto, Ontario


  • Ontario Cancer Institute, Toronto, Ontario


  • Canada Researcy Chair, Tier 1, Canadian Foundation for Innovation (2000-2007)
  • Ontario Distinguished Researcher Award, Ontario Innovation Trust (2001-2007)
  • Fellow of the American Association of Physicists in Medicine (AAPM) (2003)
  • Premier’s Discovery Award for Innovation and Leadership, Ontario Ministry of Research and Innovation (2007-2009)
  • Canada Research Chair, Tier 1, Canadian Foundation for Innovation (2008-2015)
  • Hellmuth Prize for Achievement in Research, UWO (2008)
  • Canadian Organization of Medical Physicists (COMP) Gold Medal Award, Jun. 17, 2010 (2010)
  • Fellow of the Institute of Physics (IOP) (2011)
  • Fellow of the Canadian Academy of Health Sciences (2011)


  1. Awad J, Owrangi A, Villemaire L, O’Riordan E, Parraga G, Fenster A. Three-dimensional lung tumour segmentation from x-ray computed tomography using sparse field active models. Med Phys. 39(2): 851-865, Feb 2012.

  2. Ward AD, Crukley C, McKenzie CA, Montreuil J, Gibson E, Romagnoli C, Gomez JA, Moussa M, Chin J, Bauman G, Fenster A. Prostate: Registration of digital histopathologic images to in vivo MR images acquired by using endorectal receive coil. Radiology. 263(3): 856-864, Jun 2012.

  3. Buchanan DN, Lindenmaier T, McKay S, Bureau Y, Hackam DG, Fenster A, Parraga G. The relationship of carotid three-dimensional ultrasound vessel wall volume with age and sex: Comparison to carotid intima-media thickness. Ultrasound Med Biol. 38(7): 1145-1153, Jul 2012.

  4. Ryu B, Bax J, Edirisinghe C, Lewis C, Chen J, D’Souza D, Fenster A, Wong E. Prostate brachytherapy with oblique needles to treat large glands and overcome pubic arch interference. Int J Radiat Oncol Biol Phys. 83(5): 1463-1472, Aug 2012.

  5. Waring CS, Bax JS, Samarabandu A, Holdsworth DW, Fenster A, Lacefield JC. Traceable micro-CT scaling accuracy phantom for applications requiring exact measurement of distances or volumes. Med Phys. 39(10): 6022-6027, Oct 2012. PMID: 23039640.

  6. Gibson E, Crukley C, Gaed M, Gómez JA, Moussa M, Chin JL, Bauman GS, Fenster A, Ward AD. Registration of prostate histology images to ex vivo MR images via strand-shaped fiducials.  J Magn Reson Imaging. 36(6): 1402-1412, Dec 2012. PMID: 22851455.

  7. Qiu W, Yuan J, Ukwatta E, Tessier D, Fenster A. Rotational-slice-Based prostate segmentation using level set with shape constraint for 3D end-firing TRUS guided biopsy. Med Image Comput Assist Interv. 15 (Pt 1): 537-544. 2012. PMID: 23285593.

  8. Sun Y, Yuan J, Rajchl M, Qiu W, Romagnoli C, Fenster A. Efficient convex optimization approach to 3D non-rigid MR-TRUS registration. Med Image Comput Comput Assist Interv. 16(Pt 1): 195-202, 2013.  PMID: 24505666.

  9. Miles B, Ben Ayed I, Law MW, Garvin G, Fenster A, Li S. Spine image fusion via graph cuts. IEEE Trans Biomed Eng. Jan 2013. [Epub ahead of print] PMID: 23372071.

  10. Bax JS, Waring CS, Sherebrin S, Stapleton S, Hudson TJ, Jaffray DA, Lacefield JC, Fenster A. 3D image-guided robotic needle positioning system for small animal interventions. Med Phys. Med Phys. 40(1): 011909, Jan 2013. PMID: 23298100.

  11. Qiu W, Yuan J, Ukwatta E, Fenster A.   Rotationally Resliced 3D Prostate TRUS Segmentation Using Convex Optimization with Shape Priors.  Medical Physics. 42(2): 877, Feb 2015.  PMID: 25652500. 

  12. Cepek J, Chronik BA, Lindner U, Trachtenberg J, Davidson SR, Bax J, Fenster A. A system for MRI-guided transperineal delivery of needles to the prostate for focal therapy. Med Phys. 40(1):012304, Jan 2013. PMID: 23298109.

  13. Imani F, Abolmaesumi P, Gibson E, Galesh-Khale AK, Gaed M, Moussa M, Gomez JA, Romagnoli C, Siemens DR, Leviridge M, Chang S, Fenster A, Ward AD, Mousavi P. Ultrasound-based characterization of prostate cancer: an in vivo clinical feasibility study. Med Image Comput Comput Assist Interv. 16(Pt 2): 279-286, Jan 2013.  PMID: 24579151.

  14. Qiu W, Yuan J, Ukwatta E, Sun Y, Rajchl M, Fenster A.  Fast globally optimal segmentation of 3D prostate MRI with axial symmetry prior.  Med Image Comput Comput Assist Interv. 16(Pt 2): 198-205, Jan 2013.  PMID: 24579141.

  15. De Silva T, Cool DW, Yuan J, Romognoli C, Fenster A, Ward AD.  Improving 2D-3D registration optimization using learned prostate motion data. Med Image Comput Comput Assist Interv. 16(Pt 2): 124-131, Jan 2013.  PMID: 24579132.

  16. Qiu W, Yuan J, Kishimoto J, Ukwatta E, Fenster A.   Lateral ventricle segmentation of 3D pre-term neonates US using convex optimization. Med Image Comput Comput Assist Interv. 16(Pt 3): 559-566, Jan 2013. PMID: 24505806. 

  17. Ukwatta E, Yuan J, Qiu W, Rajchl M, Chiu B, Shavakh S, Xu J, Fenster A.   Joint segmentation of 3D femoral lumen and outer wall surfaces from MR images.  Med Image Comput Comput Assist Interv. 16(Pt 1): 534-541, Jan 2013.  PMID: 24505708.

  18. Qiu W, Yuan J, Ukwatta E, Sun Y, Rajchl M, Fenster A.   Efficient 3D multi-region prostate MRI segmentation using dual optimization.   Inf Process Med Imaging. 23: 304-315, Jan 2013.  PMID: 24683978.

  19. De Silva T, Fenster A, Cool D, Romagnoli C, Samarabandu J, Ward A. 2D-3D rigid registration to compensate for prostate motion during 3D TRUS-guided biopsy. Med Phys. 40(2):022904, Feb 2013. PMID: 23387775.

  20. Tardif JC, Spence JD, Heinonen TM, Moody A, Pressacco J, Frayne R, L’Allier P, Chow BJ, Friedrich M, Black SE, Fenster A, Rutt B, Beanlands R. Atherosclerosis imaging and the Canadian Atherosclerosis Imaging Network. Can J Cardiol. 10.1016/j.cjca.2012.09.017. (29)3: 297-303, March 2013. PMID: 23245557.

  21. Ukwatta E, Yuan J, Rajchl M, Qiu W, Tessier D, Fenster A. 3-D carotid multi-region MRI segmentation by globally optimal evolution of coupled surfaces. IEEE Trans Med Imag. 32(4): 770-785. Apr 2013. PMID: 23303689.

  22. Qiu W, Yuchi M, Ding M, Tessier D, Fenster A. Needle segmentation using 3D hough transform in 3D TRUS guided prostate transperineal therapy. Med Phys. 40(4): 042902, April 2013. PMID: 23556924

  23. Karimi H, Fenster A, Samani A. A novel fast full inversion based breast ultrasound elastography technique. Phys Med Biol. 58(7): 2219-2233, April 2013. PMID: 23475227

  24. Ukwatta E, Yuan J, Buchanan D, Chiu B, Awad J, Qiu W, Parraga G, Fenster A. Three-dimensional segmentation of three-dimensional ultrasound carotid atherosclerosis using sparse field level sets. Med Phys. 40(5): 2903-2920, May 2013. PMID: 23635296.

  25. Chiu B, Ukwatta E, Shavakh S, Fenster A. Quantification and visualization of carotid segmentation accuracy and precision using a 2D standardized carotid map. Phys. Med. Biol. 58(11): 3671-3703, June 2013. PMID: 23656804.

  26. Wannarong T, Parraga G, Buchanan D, Fenster A, House A, Hackam D, Spence D. Progression of carotid plaque volume predicts cardiovascular events. Stroke. 44(7): 1859-1865, July 2013. PMID: 23735956.

  27. Qiu W, Yuan J, Ukwatta E, Tessier D, Fenster A. Three-dimensional prostate segmentation using level set with shape constraint based on rotational slices for 3D end-firing TRUS guided biopsy. Medical Physics.  40(7): 072903, July 2013. PMID: 23822454. 

  28. Miles B, Ayed IB, Law MW, Garvin G, Fenster A, Li S. Spine image fusion via graph cuts.  IEEE Trans Biomed. 60(7):  1841 - 1850, July 2013.  PMID: 23372071. 

  29. Girtler MT, Krasinski A, Dejaco C, Kitzler HH, Cui LG, Sherebrin S, Gardi L, Chhem RK, Fenster A, Romagnoli C, De Zordo T. Feasibility of 3D ultrasound to evaluate upper extremity nerves. Ultraschall Med. 34(4): 382-387, Aug 2013.  PMID: 23023451.

  30. Gibson E, Gaed M, Gómez-Lemus JA, Moussa M, Romagnoli C, Pautler, Chin JL, Crukley C, Bauman GS, Fenster A, Ward AD. 3D prostate histology reconstruction: an evaluation of image-based and fiducial-based algorithms. Medical Physics 40(9): 093501, September 2013.  PMID: 24007184. 

  31. Yuan J, Miles B, Shi J, Garvin G, Tai XC, Fenster A. Efficient convex optimization approaches to variational image fusion. Numer Math Theor Meth Appl. 7:  234-250, May 16, 2014. [Epub ahead of print]. 

  32. Kramers M, Armstrong R, Bakhshmand SM, Fenster A, de Ribaupierre S, Eagleson R.  A mobile augmented reality application for image guidance of neurosurgical interventions.  American Journal of Biomedical Engineering 3(6): 169-174, 2013. DOI: 10.5923/j.ajbe.20130306.

  33. Gibson E, Fenster A, Ward AD.  The impact of registration accuracy on imaging validation study design: A novel statistical power calculation. Med Image Anal.  17(7): 805-815, October 2013.  doi: 10.1016/j.media.2013.04.008. PMID: 23706752.

  34. Gorelick L, Veksler O, Gaed M, Gomez JA, Moussa M, Bauman G, Fenster A, Ward AD. Prostate histopathology: Learning tissue component histograms for cancer detection and classification. IEEE Trans Med Imaging.  32(10): 1804-1818.  October 2013.  PMID: 23739794.

  35. Gibson E, Gaed M, Gómez JA, Moussa M, Pautler S, Chin JL, Crukley C, Bauman GS, Fenster A, Ward AD. 3D prostate histology image reconstruction: Quantifying the impact of tissue deformation and histology section location.  J Pathol Inform.  4:31, doi: 10.4103/2153-3539.120874. eCollection 2013, Oct. 31, 2013.  PMID: 24392245.

  36. Sadeghi Neshat HR, Cool DW, Barker K, Gardi L, Kakani N, Fenster A A 3D ultrasound scanning system for image guided liver interventions.  Medical Physics.  40(11): 112903, November 2013.    PMID: 24320470. 

  37. Poulin E, Fekete CA, Létourneau M, Fenster A, Pouliot J, Beaulieu L.  Adaptation of the CVT algorithm for catheter optimization in high dose rate brachytherapy.  Medical Physics.  40(11): 111724, November 2013.  PMID: 24320432.    

  38. Kishimoto J, De Ribaupierre S, Lee DS, Mehta R, St Lawrence KS, Fenster A 3D ultrasound system to investigate intraventricular hemorrhage in preterm neonates.  Physics in Medicine and Biology. 58(21): 7513-7526, November 7, 2013. doi: 10.1088/0031-9155/58/21/7513.  PMID: 24099882.

  39. Cheng J, Li H, Fenster A, Zhang X, He X, Li L, Ding M. Fully automatic plaque segmentation in 3-D carotid ultrasound images. Ultra Med Biol. 39(12): 2431-2446, December 2013. PMID: 24063959. 

  40. Cepek J, Lindner U, Davidson SRH, Haider MA, Ghai S, Trachtenberg J, Fenster A Treatment planning for prostate focal laser ablation in the face of needle placement uncertainty.  Medical Physics.  41(1): 013301. doi: 10.1118/1.4842535, January 2014.  PMID: 24387531. 

  41. Kramers M, Armstrong R, Bakhshmand SM, Fenster A, de Ribaupierre S, Eagleson R. Evaluation of a mobile augmented reality application for image guidance of neurosurgical interventions. Stud Health Technol Inform. 196: 204-208, Jan. 2014.  PMID: 24732507. 

  42. Qiu W, Yuan J, Ukwatta E, Sun Y, Rajchl M, Fenster A Prostate segmentation: An efficient convex optimization approach with axial symmetry using 3-D TRUS and MR images.  IEEE Trans Med Imaging.  33(4): 947-960, April 2014.  doi: 10.1109/TMI.2014.2300694.  PMID: 24710163.         

  43. Qiu W, Yuan J, Ukwatta E, Sun Y, Rajchl M, Fenster A Dual optimization based prostate zonal segmentation in 3D MR images.  Medical Image Analysis.  18(4): 660-673, May 2014.  doi: 10.1016/j.media.2014.02.009.  PMID: 24721776. 

  44. Kuk M, Wannarong T, Beletsky V, Parraga G, Fenster A, Spence JD.  Volume of carotid artery ulceration as a predictor of cardiovascular events.  Stroke.  45(5):  1437-1441, May 2014.  doi: 10.1161.  PMID: 24713529. 

  45. Cepek J, Chronik BA, Fenster A The effects of magnetic field distortion on the accuracy of passive device localization frames in MR imaging. Medical Physics.  41(5): 052301, May 2014.  PMID: 24784394. 

  46. Pike D, Kirby M, Lindenmaier TJ, Sheikh K, Neron CE, Hackam DG, Spence JD, Fenster A, Paterson NA, Sin DD, Coxson HO, McCormack DG, Parraga G.  Pulmonary Abnormalities and Carotid Atherosclerosis in Ex-Smokers without Airflow Limitation.  COPD.  June 12, 2014 [Epub ahead of print].  PMID: 24921977. 

  47. Van Engelen A, Wannarong T, Parraga G, Niessen WJ, Fenster A, Spence JD, de Bruijne M.  Three-dimensional carotid ultrasound plaque texture predicts vascular events.  Stroke. pii: STROKEAHA.114.005752. [Epub ahead of print]. July 2014.  PMID: 25034714.

  48. Martin PR, Cool DW, Romagnoli C, Fenster A, Ward AD.  Magnetic resonance imaging-targeted, 3D transrectal ultrasound-guided fusion biopsy for prostate cancer: quantifying the impact of needle delivery error on diagnosis.  Medical Physics. 41(7): 073504. doi: 10.1118/1.4883838, July 2014.  PMID: 24989418. 

  49. Fenster A, Bax J, Neshat H, Cool D, Kakani N, Romagnoli C.  3D ultrasound imaging in image-guided intervention. Conf Proc IEEE Eng Biol Soc. 2014: 6151-6154, doi: 10.1109/EMBC.2014.6945033, Aug. 2014.  PMID: 25571401. 

  50. De Silva T, Cool DW, Romagnoli C, Fenster A, Ward AD.  Evaluating the utility of intraprocedural 3D TRUS image information in guiding registration for displacement compensation during prostate biopsy.  Medical Physics. 41(8): 082901, Aug. 2014.  doi: 10.1118/1.4885959.  PMID: 25086558.

  51. Cepek J, Lindner U, Louis AS, Ghai S, Davidson SRH, Gertner M, Hlasny E, Sussman MS, Trachtenerg J, Fenster A Mechatronic System for In-Bore MRI-Guided Insertion of Needles to the Prostate: An in vivo Needle Guidance Accuracy Study.  Journal of Magnetic Resonance Imaging. Journal of Magnetic Resonance Imaging.  doi: 10.1002/jmri.24742. [Epub ahead of print], September 4, 2014. 

  52. Qiu W, Yuan J, Kishimoto J, McLeod J, Chen Y, de Ribaupierre S, Fenster A User-Guided Segmentation of Preterm Neonate Ventricular System from 3-D Ultrasound Images Using Convex Optimization.  Ultrasound in Medicine and Biology. 41(2): 542-556, Feb. 2015.  PMID: 25542486.

  53. Podder T, Beaulieu L, Caldwell B, Cormack RA, Crass JB, Dicker AP, Fenster A, Fichtinger G, Meltsner MA, Moerland MA, Nath R, Rivard MJ, Salcudean T, Song DY, Thomadsen BR, Yu Y.  AAPM and GEC-ESTRO Guidelines for Image-Guided Robotic Brachytherapy: Report of Task Group 192.  Medical Physics.  41(10):  101501, October 2014.  DOI: 10.1118/1.4895013.  PMID: 25281939. 

  54. Qiu W, Rajchl M, Guo F, Sun Y, Ukwatta E, Fenster A, Yuan J.  3D prostate TRUS segmentation using globally optimized volume-preserving prior.  Med Image Computing Computer Assist Interv. 17(Pt 1): 796-803, 2014.  PMID: 25333192. 

  55. Shahedi M, Cool DW, Romagnoli C, Bauman GS, Bastian-Jordan M, Gibson E, Rodrigues G, Ahmad B, Lock M, Fenster A, Ward AD.  Spatially Varying Accuracy and Reproducibility of Prostate Segmentation in Magnetic Resonance Images using Manual and Semi-Automated Methods.  Medical Physics.  41 (11): 113503, Nov. 2014.  doi: 10.1118/1.4899182. PMID:   25370674. 

  56. Sun Y, Yuan J, Qiu W, Rajchl M, Romagnoli C, Fenster A Three-Dimensional Non-Rigid MR-TRUS Registration Using Dual Optimization.   IEEE Trans. Med. Imaging.  2014 Nov 26. [Epub ahead of print].  PMID: 25438308.

  57. Shahedi M, Cool DW, Romagnoli C, Bauman GS, Bastian-Jordan M, Gibson E, Rodrigues G, Ahmad B, Lock M, Fenster A, Ward AD.  Spatially varying accuracy and reproducibility of prostate segmentation in magnetic resonance images using manual and semiautomated methods. Med Phys. 41(11): 113503. doi: 10.1118/1.4899182, Nov. 2014.  PMID: 25370674. 

  58. Marami B, Sirouspour S, Ghoul S, Cepek J, Davidson SRH, Capson DW, Trachtenberg J, Fenster A. Elastic registration of prostate MR images based on estimation of deformation states.  Medical Image Analysis. pii: S1361-8415(14)00191-1. doi: 10.1016/j.media.2014.12.007. [Epub ahead of print], Jan. 8, 2015.  PMID: 25624044. 

  59. Cool DW, Zhang X, Romagnoli C, Izawa JI, Romano WM, Fenster A Evaluation of MRI-TRUS Fusion Versus Cognitive Registration Accuracy for MRI-Targeted, TRUS-Guided Prostate Biopsy.  AJR American Journal Roentgenol.  204(1): 83-91, Jan. 2015.  PMID: 25539241.

Contact Info

Aaron Fenster, PhD, FCCPM
Email: afenster@robarts.ca