Research Interests: Development of advanced radiation detectors for the nuclear industry and in space

My research group has been focusing on advanced radiation detector and nuclear instrumentation developments. Particularly, we developed the THick Gas Electron Multiplier (THGEM) detector, an advanced gaseous radiation detector, which showed an outstanding performance in contrast to the traditional gaseous detectors. We also developed new digital signal processing systems for radiation spectrometry and imaging. Selected current research projects are listed below.

THGEM neutron imaging detector development In 2013, we successfully developed a THGEM X-ray imaging detector.

The core work of this project was to devise a simple and efficient 2-D position readout board. For 2-D position encoding, we developed a digital signal processing system using time to digital converters and a field programmable gate array processor, which required an extensive amount of work in terms of circuit fabrication and processor programming. The detector was successfully tested for alpha and X-ray imaging. Founded on this work, we are currently designing an efficient neutron converter in order to develop a digital neutron imaging detector.

THGEM multi-element neutron dosemeter and 2-D neutron-gamma dosemeter developments

Tissue-equivalent gaseous proportional counters are made of tissue-equivalent plastics and filled with tissue-equivalent gases, which makes them the most accurate device for measuring neutron dose. However, their neutron detection efficiency is pretty low and therefore, they have not been employed for weak neutron field measurements typically encountered at nuclear power plants. To address this fundamental low efficiency problem, we have developed a “multi-element” detector consisting of a number of gaseous sensitive volumes using our THGEM technology. In order to optimize the multi-element design, we carried out extensive Monte Carlo simulations. With this Monte Carlo outcome, we accomplished a quantitative analysis for the neutron efficiency dependence on the multi-element geometry for the first time. We have built a prototype multi-element detector consisting of 7*3 gaseous volumes and its tests are currently underway.

Another advanced dosemeter we have been developing is a 2-D neutron-gamma dosemeter, which aims to measure a spatial distribution of the neutron and gamma-ray doses. The core work of this project was to build a multi-input digital signal processing system which can analyze signals from 25 detectors in parallel and real time. A preliminary result showed that the 2-D dosemeter shows the spatial neutron and gamma dose distributions quite accurately. Moreover, the digital processing system showed an excellent processing speed and energy resolution. Comprehensive tests for this 2-D detector are currently underway.

Low-level gamma-ray spectrometry

In ultra-low level gamma spectrometry, a common challenge is that owing to its weak activity, the counts from a sample are buried under background radiation counts. For the multi-photon emitters like ⁶⁰Co and ²⁶Al, important radionuclides of interests for meteorites and/or nuclear reactor samples, this challenge can be overcome by operating detectors in coincidence mode, in which case a large fraction of the background counts can be rejected while most cascade gamma-ray counts from a sample are saved. Although this principle has been well known, no systematic studies have been done in terms of optimizing the detector arrangement and segmentation to accomplish the best analytical performance.

This study will focus on measuring low level ²⁶Al, ⁶⁰Co and others radionuclides of interests. We will optimize the detector size and array pattern through an extensive Monte Carlo simulation study. The project scope also includes pulse processing development for multiple detectors in a digital architecture and investigation of optimizing time pickoff algorithm.

Research Interests: Non invasive elemental analysis of the human body; x-ray fluorescence; neutron activation analysis

Measuring the Elemental Composition of the Human Body

We develop and use techniques based in atomic and nuclear physics for non destructive elemental analysis of bulk samples. Specifically, we use x-ray fluorescence and neutron activation analysis with the aim of finding out the elemental content of living human subjects. I work closely with Fiona McNeill on many of these projects and we both collaborate with Soo-Hyun Byun, particularly drawing on his expertise in nuclear instrumentation and pulse processing. These measurements involve ionising radiation (photons or neutrons) so a key preliminary to any proposed measurement is to ensure that the dose is acceptably low, typically well within the range employed by established medical diagnostic procedures.

The most widely applied of our techniques is the analysis of lead in bone using x-ray fluorescence. In this we collaborate with industry, with academic colleagues in the US and, in a study headed by Fiona McNeill, with Health Canada. Our work has contributed to a change in thinking about long term lead exposure, particularly highlighting the importance of endogenous exposure, that is what happens when lead stored over time in bone is released back into the body via the blood.

In another example, we recently completed a pilot study, using neutron activation to measure aluminum in bone of a group of people suffering from Alzheimer’s Disease and a comparison group with no signs of dementia.

Strontium seems to be ambiguous with regards to bone health. In excess it causes a rickets-like condition. However, people suffering from osteoporosis administered a strontium supplement had fewer fractures than a comparison group. We have developed an x-ray fluorescence method to measure strontium in bone and we are seeking to find ways (and funding!) to use this further in exploring the interaction of strontium with bone health.

I have a strong interest in the interaction between science and faith from the perspective of an activate participant in both communities. With colleagues I help to run the Hamilton Science and Faith Forum, the local chapter of the Canadian Scientific and Christian Affiliation.

Research Interests: Radiation therapy & dosimetry, Medical Physicist at the Juravinski Cancer Centre

Research Interests: Development of radiation-based biomedical devices for the painless, in vivo measurement of toxic metals such as Pb, As, F, Al and Gd in bone, liver, and kidney.

Trace Toxic Elements

The main focus of my research is the development of biomedical devices based on radiation physics techniques for the in vivo measurement of trace toxic elements. In the last few years, my graduate students have built the first in vivo systems in the world for the painless, non-invasive and low dose measurement of arsenic, gadolinium and fluoride. We use two main techniques for these devices; neutron activation analysis (NAA) and x-ray fluorescence (XRF) analysis.

In addition to building biomedical systems, I apply them to studies of human health and exposure. My research has helped the understanding of human health effects from lead (Pb) exposure; my work has shown that Pb can result in elevated blood pressure and early menopause in women. Recently we discovered that people living in Hamilton have measurable levels of fluoride in their bones and a major source of exposure is tea drinking. We have been studying gadolinium and this element is used in image enhancement drugs for MRI. The Gd may be detaching from the chelate which could be potentially toxic, so we are developing systems to measure long term uptake of detached Gd in bone.

Some of the reasons I study toxic metals are explained in the Research2Reality video which can be found at http://research2reality.com/video-categories/health/ under ‘measuring health effects of metal exposure’.

Radiation Tools in Cultural Heritage

In recent years, I have used radiation tools in the study of art and cultural heritage. I was a member of a team who studied nine works of art from the McMaster Museum of Art. This resulted in an exhibition, The Unvarnished Truth: Exploring the Material History of Paintings, which is travelling across Canada until 2017. The work is also presented in the interactive website http://theunvarnishedtruth.mcmaster.ca/ .

Low Dose Radiation Effects

For the last few years, I have been collaborating with Professors Colin Seymour and Carmel Mothersill from the Department of Biology. We have been studying the effects of low level exposure to radiation types that include x- and Œ?-rays and neutrons. We have recently shown that cells, when exposed to radiation, emit a UV signal which can cause effects in nearby cells that were not exposed to the initial radiation. The UV causes a ‚Äòhalo‚Äô of effect. We are continuing to explore whether this UV signaling is an important aspect of low dose radiation effects.

Research Interests: Magnetic Resonance Imaging (MRI) and medical physics