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Colloquia and Seminars
Schedule

2012-2013 (.pdf)
The Department of Physics hosts two popular on-going lecture series.
The Physics Colloquium features invited speakers, generally specializing in topics in Medical
Physics. These talks are aimed at the broad academic audience in the Greater Toronto Area.
The Medical Physics Graduate Seminar Series consists of seminars with an emphasis on
current research in the emerging areas of Medical Physics. Faculty and students, both graduate
and undergraduate, from Physics and other Ryerson departments are encouraged to attend.
Biomedical Super‐resolved Sensing
Submitted by Graham on Thu, 10/11/2012 - 2:14pm

colloquia
Location:
POD 368
Presenter: Zeev Zalevsky, Professor
Bar-Ilan University, Israel
Abstract:
The talk will be divided into two parts. In the first part I will show how to use novel photonic
means for non contact sensing of biomedical parameters such as blood pulse pressure, heart beats
shape and rate, breathing, glucose and alcohol concentration in the blood stream as well as for
measuring intra-ocular pressure. I will also present how the same technology is applied for early
detection of malaria.
In the second part of the talk I will show several novel techniques of overcoming the geometrical
and the diffraction limits of lateral resolution in microscope systems. The proposed
configurations will be demonstrated for super resolved imaging of biological samples. I will also
show how one may extend the depth of focus of given imaging configuration and how to use this
property in order to enhance performance of microscopes, of optical coherent tomography
systems and of ophthalmic contact and intra ocular lenses.
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Nonlinear Optical Characterization of
Ultrafast Phenomena in Nanoscale Systems
Submitted by Graham on Wed, 10/03/2012 - 7:40pm
Location:
VIC 200
Presenter: Euclides Almeida
Federal University of Pernambuco, Brazil
National Institute of Technology (INT-NE/CETENE), Brazil
Abstract:
The theoretical deduction and the experimental characterization of the physical properties of
nanostructured material are challenging as the mesoscopic matter can behave differently
compared to the large (bulk) or the molecular and atomic scale. In particular, dynamical
processes are also affected and several interesting phenomena arising from the miniaturization
occur on the femto/picosecond temporal regime, such as plasmon and exciton dephasing, charge
transfer and transport. The interest in understanding and controlling these processes are
justified by the potential photonics applications of nanostructures. In the talk, we will report the
temporal investigation of such phenomena in different nanosystems using nonlinear optical
techniques, which have the advantage of extracting parameters that are often hidden in linear
optical measurements performed in ensembles.
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Seminar: Design and optimization of gold nanoparticles for
photo-acoustic imaging and photo-thermal therapy
Submitted by Graham on Mon, 10/01/2012 - 12:17pm
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seminars
Location:
KHE 225
Presenter: Yevgeniy Davletshin, PhD Candidate Department of Physics, Ryerson University
Supervisor: Dr. Carl Kumaradas
Abstract:
Recently, different types of gold nanoparticles (GNPs), such as gold nanorods, nanocages and
nanoshells, are being investigated for their unique optical and thermal properties for biomedical
applications such as photo-acoustic (PA) imaging and photo-thermal (PT) therapy. Their unique
properties are based on the ability to tune their plasmon resonance absorption peak to nearinfrared wavelengths where biological tissue is most transparent to incident laser light. Targeted
PT therapy can be delivered through laser irradiation at the plasmon resonance wavelength,
which causes heating of the particles and coagulation of the surrounding tissue. For PA imaging
short duration pulsed laser irradiation at the plasmon resonance wavelength will cause rapid
nanoparticle heating and expansion, which causes ultrasound waves to be produced and can be
detected by ultrasound imaging systems.
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Read more
Seminar: Photoacoustic Characterization of Single Red
Blood Cells
Submitted by Graham on Mon, 10/01/2012 - 12:14pm

seminar
Location:
KHE 225
Presenter: Eric Strohm, PhD Candidate Department of Physics, Ryerson University
Supervisor: Dr. Michael Kolios
Abstract:
Red blood cells (RBCs) have a unique biconcave disk shape that enables efficient flow through
the narrow tortuous blood vessels of the human body to deliver oxygen. Abnormal size and
shape can compromise blood flow and decrease their ability to absorb oxygen. A variety of
diseases can alter the RBC shape, including sickle cell disease, malaria infection and
spherocytosis. The RBC shape is also influenced by the physiological variations in blood
conditions such as pH and osmolarity. Clinical examination of the RBC size and shape are
commonly used to diagnose blood-related illness and disease. We introduce a photoacoustic
method to determine the size and shape of single RBCs. When a RBC is irradiated with a laser, it
absorbs the energy and undergoes a thermoelastic expansion resulting in the emission of a
photoacoustic wave. This wave has frequency components spanning from 20 to over 1000 MHz.
Using a photoacoustic microscope, these photoacoustic waves were recorded using transducers
ranging from 200 to 750 MHz. Analysis of the power spectrum showed periodically varying
minima and maxima that were directly related to the size and orientation of the RBC relative to
the transducer. To verify these findings were due to the RBC morphology, a finite element model
was developed to compare the measured signals to theoretical predictions. Good agreement in
the periodically varying power spectrum between measured and theory were observed for a
variety of RBC shapes and sizes. In this seminar, a preliminary study of the photoacoustic
measurements and numerical simulations of RBCs of varying shapes and sizes for the detection
of abnormal RBCs is presented.
Colloquium: Quantum Tomography and its role in
Quantum Information Science
Submitted by Graham on Mon, 09/24/2012 - 1:22am

colloquia
Location:
KHE 225
Speaker: Dr. Peter Turner, Assistant Professor
Department of Physics
University of Tokyo
Abstract:
Despite the similarities in terminology, quantum tomography is fundamentally different from the
field of computed tomography that inspired it. This is because quantum tomography addresses a
different question: instead of attempting to reconstruct a real, physical object from indirect
observations, it seeks to reconstruct a manifestly probabilistic object (a quantum state), which we
observe even less directly -- through its influence on the statistics of delicate measurements on
quantum systems. This challenging task is motivated by the relatively new field of quantum
information science, which promises some truly impressive advances over classical computer
and information science. I will give an introduction to this field for non-specialists, with the goal
of understanding the role quantum tomography plays, as well as some new developments. In the
process, I hope to stimulate some informal discussion regarding the differences and any
similarities with tomography in medical physics.
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Thesis Defense: Assessing the clinical application of the van
Herk margin formula for lung radiotherapy
Submitted by Graham on Tue, 09/04/2012 - 11:24am
Location:
KHE 329A
Presenter: Gillian Ecclestone
Supervisor: Dr. Emily Heath
Abstract:
In radiation therapy treatment planning, margins are added to the tumour volume to ensure that
the correct radiation dose is delivered to the tumour in the presence of geometrical uncertainties.
The van Herk margin formula (VHMF) was developed to calculate the minimum margin on the
target to provide full coverage by 95% of the prescribed dose to 90% of the population.
However, this formula is based on an ideal dose profile model that is not realistic for lung
radiotherapy. The purpose of this study was to investigate the validity of the VHMF for lung
radiotherapy with accurate dose calculation algorithms and respiratory motion modeling.
Ultimately, the VHMF ensured sufficient target coverage, with the exception of small lesions in
soft tissue; however, the derived PTV margins were larger than necessary. A novel planning
approach using the VHMF was tested indicating the need to account for tumour motion
trajectory and plan conformity.
Thesis Defense: Evaluating the effect of implementing
biologically realistic delays on hepatitis C kinetics and
associated estimates of antiviral efficacy
Submitted by Graham on Tue, 08/28/2012 - 1:14pm
Location:
KHE 216
Presenter: Shabnam Shamloo
Supervisor: Dr. Catherine Beauchemin
Abstract:
Mathematical modelling of viral kinetics has played an important role in the analysis of hepatitis
C virus (HCV) RNA decay after the initiation of antiviral therapy. Models have allowed for the
determination of antiviral efficacy; estimating parameters such as the rates of virions clearance
and production, and the rate of loss of infected cells; and the identification of the mechanisms
behind observed viral kinetic (VK) profiles under therapy. Current models of HCV infection are
based on a set of ordinary differential equations (ODEs) and assume that infectious cell lifespans
are exponentially distributed over time, meaning that every infected cell has an equal probability
of dying over a given time interval. Here, we introduce a new model for HCV VK which: (1)
allows for a realistic “eclipse” phase delay between the moment of cell infection and the release
of new virus; and (2) considers both exponential and gamma- distributed delays for the time
spent by infected cells in the infectious phase, continuously producing virus. To allow for the
simplest mathematical form, we consider a multiple-stage ODE model which yields gammadistributed delays. The gamma distribution enables us to enforce a minimum waiting period
before a cell can transition from one infected state to another. The application of this model to
viral titer data for patients undergoing antiviral therapy leads to different conclusions when
predicting parameter values.
Thesis Defense: Non-invasive Measurement of Cerebral
Blood Flow Using Broadband Continuous Wave Nearinfrared Spectroscopy
Submitted by Graham on Tue, 08/28/2012 - 1:07pm

thesis defense
Location:
KHE 216
Presenter: Hadi Zabihi-Yeganeh
Supervisor: Dr. Vladislav Toronov
Abstract:
We present a broad-band, continuous wave spectral approach to quantify the baseline optical
properties of tissue, in particular the absolute absorption and scattering properties and changes in
the concentration of a chromophore, which can assist to quantify the regional blood flow from
dynamic contrast-enhanced near-infrared spectroscopy data. As one of the most important
biomedical applications of this technique is the measurement of cerebral blood flow (CBF).
Experiments were conducted on phantoms and piglets. The baseline optical properties of tissue
were determined by a multi-parameter wavelength-dependent; by performing differential data fit
analysis of the near infrared (NIR) reflectance spectrum between 680 nm and 970 nm of a photon
diffusion equation solution for a semi-infinite homogeneous medium. These baseline optical
properties were used to find the changes in Indocyanine Green (ICG) concentration time course
in the tissue. The changes were obtained by fitting the dynamic data at the peak wavelength of
the chromophore absorption. These changes were used to estimate the cerebral blood flow by a
bolus tracking method.
Thesis Defense
Submitted by Graham on Mon, 08/20/2012 - 9:55am

thesis defense
Location:
KHS 335
M.Sc. Candidate: Nada Younis
Supervisor: Dr. Catherine Beauchemin
Title: A Spatial Model for the Spread of Influenza within the Human Respiratory Tract
Abstract:
Several mathematical models with varying degrees of complexity are dedicated to characterizing
influenza virus infection kinetics. The majority of existing mathematical models of in-host
kinetics are non-spatial and do not incorporate viral transport modes. Virus diffusion in the liquid
layer covering respiratory cells and this liquids entrainment by mucus towards the top of the
respiratory tract remains unaccounted for. Some of these models incorporate cellular
regeneration and an immune response in their dynamics. However, most of these models can
only reproduce seasonal infections, although severe and chronic infections sometimes occur in
humans. So they do not describe the full spectrum of infection kinetics. To address these issues,
a spatial mathematical model was developed that includes viral transport modes, cellular
regeneration and a simplified immune response. This new model successfully reproduces
observed infection profiles within realistic biological parameters consistently with their natural
causes.
Thesis Defense: Photoacoustic detection of red blood cell
aggregation
Submitted by Graham on Wed, 06/13/2012 - 6:08pm

defense
Location:
KHE 225
Presenter: Eno Hysi
Abstract: This work explores the potential of photoacoustic (PA) imaging as a tool for the
detection and monitoring of red blood cell (RBC) aggregation. It occurs during periods of
increased plasma fibrinogen and periods of decreased blood flow. Aggregation impairs the
release of oxygen from the RBCs into the surrounding environment. It also remains an essential
marker for making clinical decisions in disorders such as myocardial infarction. No current
technique is capable of simultaneously measuring the degree of aggregation and oxygenation
level. In this study, a Monte Carlo based theoretical model and an experimental protocol using
porcine and human RBCs were developed for investigating the effect of hematocrit and
aggregation level on the power spectra of PA signals while assessing the oxygen saturation of the
same sample. Frequency-domain analysis of the simulated and measured PA signals were used to
derive the spectral slope and midband fit of the normalized power spectra. The samples were
illuminated with 750 and 1064 nm lasers and changes in spectral parameters were compared to
the oxygen-dependent optical absorption coefficients to assess the oxygenation level. Good
agreement between the theoretical and experimental spectral parameters was obtained with
regards to the spectral slope of non-aggregated spectra (~0.3 dB/MHz). The experimental
midband fit was increased by ~5 dB when the aggregation size reached the largest level. The
results provide a framework for using PA radio-frequency spectroscopic parameters for
monitoring the aggregation and oxygenation levels of RBCs.
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