Dr. R Glenn Wells, PhD, FCCPM, is a research scientist at the University of Ottawa Heart Institute (www.ottawaheart.ca), Canada’s largest and foremost heart health centre dedicated to understanding, treating, and preventing heart disease. He is an Associate Professor at the University of Ottawa and an Adjunct Professor in Physics at Carleton University.
Dr. Wells’ research interests are in the physics of multimodality imaging with nuclear medicine: the combination of multi-slice X-ray computed tomography (CT) with single-photon emission computed tomography (SPECT) and positron emission tomography (PET). Nuclear medicine imaging is a 3D medical imaging technology that is used to diagnose and evaluate a wide variety of diseases including cancer and heart disease. The technique uses radioactively-labeled compounds that are injected into the patient. Based on how the compound is processed by the body, the images of the distribution of radioactivity can tell us how well the different organs are working and show us where there are abnormalities. Multi-modal cameras such as PET/CT and SPECT/CT combine two types of imaging in a single device. These cameras provide exquisite anatomical images from CT accurately aligned with nuclear medicine functional images from PET or SPECT.
SPECT systems that are specifically designed for cardiac imaging have recently been introduced. These cameras have greater sensitivity, spatial resolution, energy resolution and temporal resolution compared to standard gamma cameras. These capabilities open the door to dose reduction and dynamic SPECT imaging but the camera designs are novel and not well understood. An area of particular interest is using dynamic SPECT to measure absolute myocardial blood flow (MBF). Conventional SPECT using relative assessment of images, that is, it assumes that the ‘brightest’ part of the tissue is normal. When this is not the case, the severity and extent of disease can be badly underestimated. MBF imaging assigns an absolute scale to the images and thereby fixes this problem. Measuring MBF with SPECT is a very new area of development that is receiving great interest from the nuclear medicine community.
Current research projects include:
- Variable resolution and sensitivity in pinhole SPECT. One of the cardiac SPECT camera designs uses pinhole collimation which introduces substantial variation into the sensitivity and spatial resolution of the camera over its field of view. We are studying the impact of these variations on the detection of heart disease and investigating camera design modifications that might reduce the effects of these variations.
- Scatter modeling. The new cardiac cameras use solid-state Cadmium Zinc Telluride detectors which have superior energy resolution compared to traditional crystal detectors but which also have an energy spectrum that complicates standard methods of correcting for scattered photons. Accurate modeling of scatter for this system will allow improved scatter correction in cardiac imaging and may also offer a means to use the scatter photons for image reconstruction. This latter approach could allow improved image quality and/or reduced radiation dose to patients undergoing these important clinical procedures.
- Performance Assessment. The novel camera design makes it difficult to assess the performance of these cameras. We are investigating practical methods of measuring camera performance and thereby ensuring that the image quality is maintained at optimal design levels.
- SPECT Absolute Myocardial Blood Flow. We are evaluating dynamic SPECT for clinical measurement of MBF. Concurrent with these studies, we are investigating methods to improve (simplify) the acquisition protocol to enhance clinical adoption and pursuing advanced reconstruction methods to improve the repeatability (precision) of MBF measurements.
Recent Publications (my trainees are in italics):
- S.G. Cuddy-Walsh, R.G. Wells,”Patient-specific estimation of spatially-variant image noise for pinhole cardiac SPECT camera.” Med Phys 2018 [Accepted].
- R.G. Wells, B. Marvin, M. Poirier, J.M. Renaud, R.A. deKemp, T.D. Ruddy, “Optimization of SPECT Measurement of Myocardial Blood Flow with Corrections for Attenuation, Motion, and Blood-Binding Compared to PET.” J Nucl Med. 2017 Dec;58(12):2013-2019.
- R.G. Wells, M. Trottier, M. Premaratne, K. Vanderwerf, T.D. Ruddy, “Single CT for attenuation correction of rest/stress cardiac SPECT perfusion imaging.” J Nucl Cardiol. 2016 Nov 17. [Epub ahead of print]
- A. Pourmoghaddas, R.G. Wells, “Analytically-Based Photon Scatter Modeling For A Multi-pinhole Cardiac SPECT Camera”. Med Phys 2016 43:6098-6108.
- P.J. Prior, R. Timmins, J. Petryk, J. Strydhorst, Y. Duan, L. Wei, R.G. Wells, “A modified TEW approach to scatter correction for In-111 and Tc-99m dual-isotope small-animal SPECT”. Med Phys 2016 43:5503-5513.
- M. Kamkar, L.Wei, C. Gaudet, M. Bugden, J. Petryk, Y. Duan, H.Wyatt, R.G.Wells, Y. Marcel, N.D. Priest, R. Mitchel, T.D. Ruddy, “Evaluation of Apoptosis with 99mTc-rhAnnexin V-128 and Inflammation with 18FFlurodeoxyglucose in a Low-Dose IrradiationModel of Atherosclerosis in Apolipoprotein E-DeficientMice.”. J. Nucl. Med. 2016; 57(11):1784-1791.
- J. Wang, R. Arulanandam, R. Wassenaar, T. Falls, J. Petryk, J. Paget, K. Garson, C. Cemeus, B.C. Vanderhyden, R.G. Wells, J.C. Bell, F. Le Boeuf, “Enhancing expression of functional human sodium iodide symporter and somatostatin receptor in recombinant oncolytic vaccinia virus for in vivo imaging of tumors”. J Nucl Med 2016 [Epub 2016 Sep 15].
- H.Gabrani-Juma, O.J. Clarkin, A. Pourmoghaddas, B. Driscoll, R.G. Wells, R.A. deKemp, R.Klein,"Validation of a Multimodality Flow Phantom and its Application for Assessment of Dynamic SPECT and PET Technologies". IEEE Trans Med Imaging, 2017; 36:132-141.
- A. Pourmoghaddas, R.G. Wells, “Quantitatively accurate activity measurements with a dedicated cardiac SPECT camera: Physical phantom experiments.” Med Phys, 2016; 43:44-51.
- R. Timmins, R. Klein, J. Petryk, B. Marvin, L. Wei, R.A. deKemp, T.D. Ruddy, R.G. Wells “Reduced dose measurement of absolute myocardial blood flow using dynamic SPECT imaging in a porcine model”. Med Phys, 2015; 42:5075-5083.
- T.L. Miao, V. Kansal, R.G. Wells, I. Ali, T.D. Ruddy, B.J.W. Chow, “Adopting New Gamma Nucl Cardio 2016; 23:807-817.
- R.G. Wells, L. Wei, J. Lockwood, Y. Duan, B. Marvin, R. Timmins, K. Soueidan, C. Bensimon, P. Fernnado,T.D. Ruddy, “Flow-dependent uptake of I-123-CMICE-013, a novel SPECT perfusion agent, compared to standard tracers”. J Nucl Med 2015; 56:764-770.
- J.H. Strydhorst, T.D. Ruddy, R.G. Wells, “Effects of CT-based attenuation correction on rat microSPECT images on relative myocardial perfusion and quantitative tracer uptake”. Med Phys 2015; 42(4):1818-1824.
- R. Timmins, T.D. Ruddy, R.G. Wells, “Patient position alters attenuation effects in multi-pinhole cardiac SPECT” Med Phys 2015; 42(3):1233-1240.
- A Bell, G.A.McRae, R.Wassenaar, R.G.Wells, D. Faber, “nSPECT: a Radioisotope-free Approach to Nuclear Medicine Imaging” IEEE Trans. Nucl. Sci. 2015; 62(3):791-798.
- A. Pourmoghaddas, K. Vanderwerf, T.D. Ruddy, R.G. Wells, “Scatter correction improves concordance in SPECT MPI with a dedicated cardiac SPECT solid state camera”. J Nucl Cardiol, 2015; 22(2):334-343.
- E.J. Orton, I. Al Harbi, R. Klein, R.S.B. Beanlands, R.A. deKemp, and R.G. Wells, “Detection and severity classification of extra-cardiac interference in 82Rb PET myocardial perfusion imaging”.Med. Phys. 2014; 41, 102501 (11 pages).
- R.G. Wells, R. Timmins, R. Klein, J. Lockwood, B. Marvin, R.A. deKemp, and T.D. Ruddy, “Dynamic SPECT measurement of Absolute Myocardial Blood Flow in a Porcine Model”. J Nucl Med 2014; 55:1685-1691.
- M. Lalonde, R.G.Wells, D. Birnie, T.D. Ruddy, and R.Wassenaar, “Development and optimization of SPECT gated blood pool cluster analysis for the prediction of CRT outcome”. Med Phys 2014; 41(7):072506.
- J.H. Strydhorst, R.G. Wells, “Quantitative Measurement of In Vivo Tracer Concentration in Rats with Multiplexed Multi-pinhole SPECT”. IEEE Trans Nucl Sci 2014; 61(3):1136-1142.
- R. Galea, C. Ross, R.G. Wells, “Reduce, reuse and recycle: A green solution to Canada’s medical isotope shortage”. Appl Radiat Isot. 2014; 87:148-51.
- Y. Duan, J. Lockwood, L. Wei, C. Hunter, K. Soueidan, C. Bensimon, P. Fernando, R.G. Wells, T.D. Ruddy, “Biodistribution and radiodosimetry of a novel myocardial perfusion tracer 123I-CMICE-013 in healthy rats”. Eur J Nucl Med Mol Imaging Research 2014; 4(1): 16 (12 pages).
- L. Wei, C. Bensimon, X. Yan, J. Lockwood, W. Gan, R.G. Wells, Y. Duan, P. Fernando, B. Gottlieb, W. Mullett, T.D. Ruddy, ”Characterization of four isomers of 123I-CMICE-013: a Potential SPECT Myocardial Perfusion Imaging Agent”. Bioorganic and Medicinal Chemistry 2014; 22(7): 2033-2044.
- M. Lalonde, D. Birnie, T.D. Ruddy, R. deKemp, R.S. Beanlands, R.Wassenaar and R.G.Wells, “SPECT gated blood pool analysis of lateral wall motion for the prediction of CRT response”. Int J Cardiovasc Imaging 2014; 30(3):559-569.
- P. Fernando, X. Yan, J. Lockwood, Y. Duan, L. Wei, R.G. Wells, C. Bensimon, W.M. Mullett and T.D. Ruddy, “Toxicological evaluation of a rotenone derivative in rodents for clinical myocardial perfusion imaging”. Cardiovasc Toxicol 2014; 14:170-182.