The first full morning of the meeting was dedicated to a symposium entitled "Medical Isotopes and Imaging: Where do we go from here?". The session addressed today's problems with the supply of the imaging isotope technetium-99m (Tc-99m) – an issue that's felt keenly here in Ottawa, with the currently-closed Chalk River nuclear reactor only a two-hour drive away.
The question posed in the symposium's title was addressed in a number of ways by the featured speakers. First up, Glenn Wells from the University of Ottawa Heart Institute gave a presentation entitled "Imaging More with Less". Wells showed how developments in image processing software and camera hardware can provide equivalent image quality with reduced signal.
The hardware in question, based on pixellated cadmium-zinc-telluride solid state detectors, was particularly impressive, providing improved energy resolution and reduced dead-time. These advances allow either shorter scan times (invaluable for 4D measurements) or a reduction in the injected activity, thus enabling scanning of more patients with less tracer.
Alternatives to SPECT imaging using Tc-99m, focusing on the PET techniques pioneered by Wells and colleagues, were also discussed. The Heart Institute's on-site cyclotron is fundamental to these techniques and meeting delegates had an opportunity to tour the facility later in the week.
Meanwhile, Carl Ross of the National Research Council (NRC) described progress made by a Canadian-US collaboration on developing an accelerator-based method for Tc-99m production that eliminates the need for nuclear reactors. The NRC group has demonstrated all the steps in the process, from irradiation of molybdenum-100 with a high-energy linac X-ray beam, to extraction of the Tc-99m in a form that's suitable for use in a nuclear medicine scanner.
Ross also outlined the steps required to establish a national facility and surprised a number of delegates by indicating that a facility comprising just two 100 kW linacs (similar to machines routinely used for industrial radiation processing) could supply Canada's requirement for Tc-99m.
Emerging talent
A highlight of every COMP annual meeting is the quality of presentations from graduate students and this was definitely a vintage year. Ten participants competed in the "J R Cunningham Young Investigators Symposium". Presentations covered a wide range of topics, including PET mammography, quality assurance for intensity-modulated radiotherapy, ultrasound imaging for abdominal surgery and helical dose delivery using cobalt-60.
The winner was Joel St Aubin from the University of Alberta, whose work on magnetically shielding a linac is crucial to the development of an integrated linac-MR system. St Aubin is part of the group led by Gino Fallone at the Cross Cancer Institute in Edmonton that's racing to develop a system that will combine the dose delivery of a linac with the imaging capability of an MRI scanner.
One major challenge in creating such as system is to address the effect of the scanner's magnet on the electron beam of the linac. In his winning presentation, "Magnetically shielding the linac in a bi-planar linac-MR system", St Aubin used finite element modelling to show that magnetic shielding of the linac was possible.
Award winning
The winner of the COMP Gold Medal was also honoured during the annual meeting. The Gold Medal is the highest award given by COMP and recognizes a member who has made a significant contribution to the field of medical physics in Canada. This year, it was bestowed upon Aaron Fenster, the founding director of the Imaging Research Laboratories (IRL) at the Robarts Research Institute and professor at the University of Western Ontario.
Over the past 22 years, Fenster has built the Robarts Imaging Laboratories into an internationally recognized group. His research output includes 225 peer-reviewed papers, more than 20 patents and two commercial spin-offs, and in 2007 he received the Ontario Premier's Award for Innovative Leadership.
Continuing with the theme of awards, there were prizes for the best oral and poster presentations at the conference. The former was awarded to Jason St-Hilaire from Université Laval in Quebec City. St-Hilaire showed that when treating lung cancer using external-beam radiation therapy, healthy lung tissue could be spared by using non-coplanar beam delivery with SPECT imaging employed to determine lung function. This method could lead to the long-desired goal of patient-specific treatment planning.
The winner of the best poster presentation was Arman Sarfehnia from McGill University for his work on water calorimetry in proton beams – a topic recently highlighted by medicalphysicsweb (see: Pulsed protons no problem for calorimetry). The McGill researchers operated their water calorimeter at the proton facility at the Massachusetts General Hospital in Boston, MA, and obtained excellent results for both scattered and scanned proton beams.
Sarfehnia reported the overall uncertainty (one sigma) on the absorbed dose determination as 0.38% (scattered) and 0.64% (scanned) – impressive results that compare well to those reported recently in the literature. He noted that with improvements already in development, an uncertainty of less than 0.4% for both scattered and scanned beams is achievable.
This is but a sampling of the excellent work presented at the Ottawa meeting. Next year, the COMP annual meeting will be held jointly with that of the American Association of Physicists in Medicine (AAPM), from 31 July to 4 August in the beautiful city of Vancouver.