Allison Toltz

Name: Allison Toltz, MSc

Level at MPU: PhD

Email: allison.toltz [at] mail.mcgill.ca

Website: researchgate.net/profile/AllisonToltz

Supervisor(s): Dr. Jan Seuntjens

Research interests: Proton therapy range verification

Link to CV

 

Research summary

Quantification of physical uncertainties in calculating the position of the Bragg peak, known as range verification, is essential to the safe and effective use of proton therapy.  To achieve our research objectives of establishing clinical methods to reduce range uncertainty for proton therapy, we propose two complementary methods of range verification: (1) polymer gel dosimeters analyzed with both optical computed tomography (OCT) and magnetic resonance imaging (MRI) to evaluate the three-dimensional dose distribution of a therapeutic proton delivery prior to treatment, and (2) in vivo point detector measurements to perform adaptive beam energy adjustments for pediatric patients receiving passively scattered proton craniospainal irradiation.

Experimental Approach: The project cultivates an interdisciplinary approach involving particle simulation, radiation dosimetry, imaging, clinical oncology, prototype design, and a multi-institutional collaboration to achieve the research objectives. Particle simulation studies using the Tool for Particle Simulation (TOPAS) platform will optimize positioning of the point detector in the patient, establish minimum requisite dose for positional accuracy, and quantify range-mixing uncertainty. Design of a clinically compatible prototype will be achieved through consultation with radiation oncology and pediatric anesthesiology. A fabrication protocol for the polymer gels will be established and validated in photon and electron beams at our institution using OCT for imaging as well as MRI since the collaborating proton facility is at the Massachusetts General Hospital (MGH) in Boston, Massachusetts. A T2 sequencing protocol for a 3.0 T MRI scanner to image the gels will be optimized by working with our institution’s MR physicist and the scanner manufacturer. This will allow for the polymer gel dosimeter to be imaged at the proton facility at MGH (which is not equipped with an OCT). The project is an amalgamation of my PhD thesis work; my role is to conduct the simulation studies, evaluate the clinical requirements of the point detector system with clinicians, manufacture and validate the polymer gels, calibrate the OCT, optimize the MRI sequencing protocol, and design and analyze all experimental measurements, in addition to coordinating all collaborators.

Impact: The point detector array system aims to reduce range uncertainty for pediatric craniospinal irradiation cases by inserting the detector into the esophagus of the anesthetized patient immediately prior to treatment. A very low dose (on the order of 2 cGy) would allow for the characterized system to perform a final range verification measurement and potentially result in an adaptive adjustment of the beam energy to ensure target coverage while confirming adequate sparing of the esophagus, which may reduce the risk of acute esophagitis. For sites where an intracavitary measurement is impractical, a streamlined fabrication and imaging protocol for polymer gels could provide three-dimensional range verification for patient-specific quality assurance prior to treatment. 

 

Key publications

  1. Toltz, A., Hoesl, M., Schuemann, J., et al.(2017). Time-resolved diode dosimetry for in vivo proton therapy range verification: calibration through numerical modeling. J Appl Clin Med Phys. {Accepted for publication 2017.}
  2. A Toltz, N Shin, C Laude, C Freeman, J Seuntjens, W Parker, D Roberge. Late radiation toxicity in Hodgkin lymphoma patients; proton therapy’s potential.” Journal of Applied Clinical Medical Physics 2015; 16:5.

 

Awards

(2016-2018) Alumnus, Strategic Training in Transdisciplinary Radiation Science for the 21st Century, Department of Radiation Oncology, University of Toronto

(2015) Scholar, Excellence in Radiation Research in the 21st Century, Department of Radiation Oncology, University of Toronto

(2013-2016) Scholar, CREATE Medical Physics Research Training Network, Medical Physics Unit, McGill University

(2012-2017) Graduate Travel Awards, Department of Physics, McGill University

(2011) Principal’s Graduate Fellowship, Medical Physics Unit, McGill University

(2011) Provost’s Graduate Fellowship, Medical Physics Unit, McGill University

 

 

 

 

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