Grants and Contributions:

Grant or Award spanning more than one fiscal year. (2017-2018 to 2022-2023)

My research relates to improving position emission tomography (PET) for small animal and human brain imaging. PET is a “functional imaging” technique using molecules labelled with positron emitting atoms to investigate regional metabolism of that molecule by the formation of images of its utilization rate as opposed to the underlying anatomy. Recently this has been combined with magnetic resonance imaging (MRI) which provides images of the anatomy over which the PET image is superimposed.

Working in collaboration with colleagues in Winnipeg and Vancouver, I have helped commercialize an insert for an MRI scanner which is a PET scanner in order to enable simultaneous PET and MRI imaging The commercial success of this project has provided an incentive for us to work towards a scaled-up version on our PET insert suitable for human brain imaging. It will be much faster and have better spatial resolution than current PET brain scanners, and be adaptable to any MRI scanner. My application covers the research I intend to undertake to support this project.

1) Improve the timing accuracy of the detectors in the PET scanner so that the advantages of time-of-flight PET as demonstrated in whole body PET images will apply to human brain imaging. This requires a timing resolution of about 200 psec FWHM. Using my very fast signal digitizing system, I will explore polynomial fitting to the samples before and during rising edge of the detector pulses. This should give a very robust estimate of the event time. I will then determine the optimal sample rate which provides the desired performance with the lowest sampling rate in order to reduce the complexity and cost of the instrument.

2) Most PET detectors are made from a large number of small scintillation crystals separated with reflective material. The cutting and polishing of these crystals is wasteful of material and labour intensive. An alternative is to use a single crystal, and a large number of independently read-out light sensors which is complicated and expensive compared with the multiplexing method we prefer. Recently I saw that a group in Japan used sub-surface laser engraving of a scintillation crystal to create “walls” which serve as light-guides. I will use the services of a laser ornament and jewellery manufacturer to etch walls in a single crystal in the same positions we segment our crystals into 409 elements. If successful, this would result in significant cost reductions in the manufacture of PET detectors.

3) Finally I will make a new version of my patented PET timing alignment technique to calibrate PET/MRI scanners. Now I use a fast photomultiplier (PMT) to detect the decay of positron emitting isotopes embedded in a plastic scintillator. The time between this and the detection of the annihilation photon by the PET scanner’s detectors is used to build a time offset correction table. I will test very fast silicon PMTs rather than a PMT to make an MRI compatible version.