Lawrence John Schreiner

• PhD
• Professor Emeritus at Queen's University

Purpose Medical physics professional development is limited in parts of the globe and can be aided by virtual mentoring. A global online perception survey was conducted to elucidate the characteristics of the preferred virtual mentoring program. Methods Informed by a literature review and pilot testing by focus groups, the survey was electronicall...

End-to-End (E2E) testing is a method originating from computer science that is designed to determine whether an application communicates as required with hardware, networks, databases, and other applications. This paper is to advocate that the quality management (QM) of modern radiation therapy (RT) would benefit from more regular use of E2E based...

The development of three-dimensional (3D) dosimetry was motivated by its promise as an effective methodology for the validation of the complex dose distributions achieved by modern techniques such as Intensity Modulated and Volumetric Arc Radiation Therapy. 3D techniques were first proposed in the 1980s when clinics were just starting to move from...

In the clinic, routine quality assurance tests ensure the proper functioning of each individual aspect of a radiation therapy treatment delivery. However, these tests may not guarantee an accurate treatment delivery. In this work, we present the design and application of a head phantom (using 3D printing technology) developed for end-to-end quality...

Voxelizing three-dimensional surfaces into binary image volumes is a frequently performed operation in medical applications. In radiation therapy (RT), dose-volume histograms (DVHs) calculated within such surfaces are used to assess the quality of an RT treatment plan in both clinical and research settings. To calculate a DVH, the 3D surfaces need...

The accuracy of Eclipse TM -calculated head and neck VMAT plan dose delivery was assessed in the situation when there is a gap between placed bolus on a head and neck thermoplastic mask and the body surface. GafchromicEBT3 film dosimetry was used for dose delivery validation. The results from 3%, 3 mm 2D gamma comparison indicate better than 95% ag...

The cause and removal of streaking artifacts from catheters within radiochromic 3D dosimeters was investigated to allow the use of these dosimeters for high dose rate (HDR) brachytherapy applications. The OSC-TV iterative reconstruction algorithm’s ability to remove the streaking artifacts from one or more catheters was validated using external bea...

Since 1999 it has been convention at the IC3Ddose conferences to provide an opportunity for interested attendees to come together for an early morning session to review the basic properties of one family of 3D dosimeters: volumetric chemical dosimeters. Seasoned workers in the field benefit from a refreshed perspective, while those new to the field...

It has been suggested that modern radiation therapy could benefit from adopting the “End to End” (E2E) type of testing developed originally in computer science to determine whether applications and systems work as required under real-world scenarios. The motivation for adopting E2E techniques for image guided adaptive radiation therapy validation i...

Three dimensional dosimetry is being used in an increasingly wide variety of clinical applications as more gel and radiochromic plastic dosimeters become available. However, accessible 3D dosimetry analysis tools have not kept pace. 3D dosimetry data analysis is time consuming and laborious, creating a barrier to entry for busy clinical environment...

The Canadian Organization of Medical Physicists (COMP), in close partnership with the Canadian Partnership for Quality Radiotherapy (CPQR) has developed a series of Technical Quality Control (TQC) guidelines for radiation treatment equipment. These guidelines outline the performance objectives that equipment should meet in order to ensure an accept...

Although contemporary cardiac X-ray exams are typically set so benefits outweighs the risk, the growing use and increasing complexity of the cardiovascular interventional radiological (CVIR) procedures does increase the risk of radiation-related tissue effects and stochastic effects to the individual patients and the population. In view of these ra...

This paper offers best practice recommendations for the maintenance and retention of radiotherapy health records and technical information for cancer programmes. The recommendations are based on a review of the published and grey literature, feedback from key informants from seven countries and expert consensus. Ideally, complete health records sho...

Designed experiments were performed to produce empirical models for the dose sensitivity, initial absorbance, and dose-rate dependence respectively for leucocrystal violet (LCV) micelle gel dosimeters containing cetyltrimethylammonium bromide (CTAB) and 2,2,2-trichloroethanol (TCE). Previous gels of this type showed dose-rate dependent behaviour, p...

For seventeen years a community of basic and clinical scientists and researchers has been meeting bi-annually to promote the clinical advance of techniques to measure radiation dose in three dimensions. The interest in this dosimetry was motivated by its promise as an effective methodology for 3D measurement of the complex conformal dose distributi...

Radiochromic film dosimetry has been widely adopted in the clinic as it is a convenient option for dose measurement and verification. Film dosimetry analysis is typically performed using expensive commercial software, or custom made scripts in Matlab. However, common clinical film analysis software is not transparent regarding what corrections/opti...

A series of experiments are conducted to evaluate the effects of refractive index (RI) mismatch in readout with a Vista cone beam optical CT scanner. The changing optical attenuation in cuvettes of different colours and RI are quantified using a spectrophotometer, which shows decreasing attenuation as RI increases. A small jar of a colourless solut...

The impact of changing anatomy due to tumour shrinkage was assessed for a VMAT head & neck plan optimized according to our centre's planning protocol. A custom-built wax phantom accommodating ion chamber, MOSFET, EBT3 film and Fricke-xylenol orange-gelatin (FXG) gel dosimeters and a variable size bolus 'tumour' was used in the investigation. Result...

A radiochromic silicone based dosimeter has been fabricated that allows for three-dimensional (3D) dose verification. This paper characterizes the silicone dosimeter and verifies previous results found by other research groups. Using a recipe found to be dose rate independent, we identify the spectra of the dosimeter irradiated to different doses a...

Medical physics is a rapidly developing, technologically dependent, field. New discoveries are being made almost daily, as demonstrated by papers in this and other similar journals. Many of the authors are early in their careers. Some are concerned, however, that more famous medical physicists often get credit for discoveries due to their fame rath...

A close partnership between the Canadian Partnership for Quality Radiotherapy (CPQR) and the Canadian Organization of Medical Physicist's (COMP) Quality Assurance and Radiation Safety Advisory Committee (QARSAC) has resulted in the development of a suite of Technical Quality Control (TQC) guidelines for radiation treatment equipment; they outline s...

The Canadian Partnership for Quality Radiotherapy (CPQR) and the Canadian Organization of Medical Physicist's (COMP) Quality Assurance and Radiation Safety Advisory Committee (QARSAC) have worked together in the development of a suite of Technical Quality Control (TQC) Guidelines for radiation treatment equipment and technologies, that outline spec...

Purpose:Radiochromic film dosimetry is a standard technique used in clinics to verify modern conformal radiation therapy delivery, and sometimes in research to validate other dosimeters. We are using film as a standard for comparison as we improve high-resolution three-dimensional gel systems for small field dosimetry; however, precise film dosimet...

A close partnership between the Canadian Partnership for Quality Radiotherapy (CPQR) and the Canadian Organization of Medical Physicist’s (COMP) Quality Assurance and Radiation Safety Advisory Committee (QARSAC) has resulted in the development of a suite of Technical Quality Control (TQC) Guidelines for radiation treatment equipment, that outline s...

The aim of this study was to investigate the nature and causes of radiation dose imparted to patients undergoing barium-based X-ray fluoroscopy procedures in Tanzania and to compare these doses to those reported in the literature from other regions worldwide. The air kerma area product (KAP) to patient undergoing barium investigations of gastrointe...

Full three-dimensional (3D) dosimetry using volumetric chemical dosimeters probed by 3D imaging systems has long been a promising technique for the radiation therapy clinic, since it provides a unique methodology for dose measurements in the volume irradiated using complex conformal delivery techniques such as IMRT and VMAT. To date true 3D dosimet...

Full three-dimensional (3D) dosimetry using volumetric chemical dosimeters probed by 3D imaging systems has long been a promising technique for the radiation therapy clinic, since it provides a unique methodology for dose measurements in the volume irradiated using complex conformal delivery techniques such as IMRT and VMAT. To date true 3D dosimet...

Lung cancer is the most common cancer worldwide and the fifth most common cause of death globally. Its incidence continues to increase, especially within low- and middle-income countries (LMICs), which have limited capacity to address the growing need for treatment. The standard of care for lung cancer treatment often involves radiation therapy (RT...

Moving the computational analysis for 3D gel dosimetry into the 3D Slicer (www.slicer.org) environment has made gel dosimetry more clinically accessible. To ensure accuracy, we cross-validate the 3D gamma comparison module in 3D Slicer with an independently developed algorithm using simulated and measured dose distributions. Two reference dose dist...

Radiochromic leuco crystal violet (LCV) micelle gel dosimeters are promising three-dimensional radiation dosimeters because of their spatial stability and suitability for optical readout. The effects of surfactant type and surfactant concentration on dose sensitivity of LCV micelle gels are tested, demonstrating that dose sensitivity and initial co...

In this study, recipe optimization of Leuco Crystal Violet (LCV) micelle gels made with the surfactant Cetyl Trimethyl Ammonium Bromide (CTAB) and the chemical sensitizer 2,2,2-trichloroethanol (TCE) was aided by a two-level three-factor designed experiment. The optimized recipe contains 0.75 mM LCV, 17.0 mM CTAB, 120 mM TCE, 25.0 mM tri-chloro ace...

In contemporary high-dose-rate brachytherapy treatment of superficial tumors, catheters are placed in a wax mould. The creation of current wax models is a difficult and time consuming proces.The irradiation plan can only be computed post-construction and requires a second CT scan. In case no satisfactory dose plan can be created, the mould is disca...

The effects of the various components of leuco crystal violet (LCV) micelle gels on dose sensitivity and initial colour are tested. Dose sensitivity and gel turbidity are influenced by tri-chloro acetic acid (TCAA) concentration, with the highest dose sensitivity obtained at ~21.5 mM. Increasing Triton x-100 (Txl00) concentration improved dose sens...

Since the introduction of volumetric chemical dosimetry with Fricke gel dosimeters in the 1980s, three-dimensional (3D) dosimetry has been a promising technique for the clinic, since it provides a unique methodology for 3D dose measurement of the complex conformal dose distributions achieved by modern techniques such as Intensity Modulated and Volu...

Designed experiments and empirical models are used to optimize a Leuco Crystal Violet (LCV) micelle gel recipe to improve dose sensitivity and initial colour. The optimized recipe contains 0.75 mM LCV, 17.0 mM Cetyl Trimethyl Ammonium Bromide (CTAB), 120 mM 2,2,2-trichloroethanol (TCE), 25.0 mM tri-chloro acetic acid (TCAA), 4 wt% gelatin and ~96 w...

An extension tailored to dose data processing and analysis has been developed in the open source imaging application 3D Slicer to aid in routine clinical use of gel dosimetry. This extension allows for registration, calibration, and comparison of 3D gel dosimeter data (imaged using an optical CT scanner) to treatment planning data. In this work, we...

One challenge in gel dosimetry is the manipulation and analysis of complex data sets from different systems. In this paper, we describe a simple and fast gel dosimetry analysis tool for radiation therapy dose deliveries. Using the open source medical imaging software 3D Slicer, an extension was designed and implemented for the purpose of importing...

The dynamics of the hydration of a white cement with negligible iron content and of Portland cement with a considerable amount of iron has been studied by proton magnetic resonance. The presence of iron in Portland cement results in the protons close to the free electron spins of iron being out of resonance and their signal being suppressed. The ev...

Image guidance capability is an important feature of modern radiotherapy linacs, and future cobalt-60 units will be expected to have similar capabilities. Imaging with the treatment beam is an appealing option, for reasons of simplicity and cost, but the dose needed to produce cone beam CT (CBCT) images in a Co-60 treatment beam is too high for thi...

High density concrete is usually used for radiation shielding around radiotherapy treatment rooms. Because the concrete is specified differently at the design, construction, and verification stages, the relationship between the intended performance and the actual performance of the shielding material might not be entirely clear. In this study, cyli...

Purpose: Investigations have shown that a Cobalt-60 (Co-60) radioactive source has the potential to play a role in intensity modulated radiation therapy (IMRT). In this paper, Co-60 tomotherapy's conformal dose delivery potential is evaluated by delivering conformal dose plans on a cylindrical homogeneous phantom containing clinical structures sim...

Emulsified diacetylenes as reporter molecules in micelle gel dosimeters were evaluated in the current article. It was observed that gels containing PCDA emulsified in deionized water using SDS changed from colourless to blue upon irradiation. Unfortunately, recipes that led to turbid gels resulted in a colour change, but transparent gels did not ch...

This work describes the use of a motion phantom and 1D, 2D, and 3D ion chamber, EBT3 film, electronic portal imaging device (EPID) and FXG gel measurements for dosimetric validation of a stereotactic ablative radiation therapy (SBRT) technique in our clinic. Results show good agreement between the measurements and calculated treatment plan dose.

One component of clinical treatment validation, for example in the commissioning of new radiotherapy techniques or in patient specific quality assurance, is the evaluation and verification of planned and delivered dose distributions. Gamma and related tests (such as the chi evaluation) have become standard clinical tools for such work. Both functio...

This work describes the use of a motion phantom and 1D, 2D, and 3D ion chamber, EBT3 film, electronic portal imaging device (EPID) and FXG gel measurements for dosimetric validation of a stereotactic ablative radiation therapy (SBRT) technique in our clinic. Results show good agreement between the measurements and calculated treatment plan dose.

A custom in-house built multi-purpose phantom has been designed and built to investigate the integrity of the 2D Matrixx ion chamber (Scanditronix-Welhoffer, Bartlett, TN) and 3D electronic portal image device (EPID) techniques employed for patient specific IMRT delivery QA at our centre. Single ion chamber, EBT3 film and FXG gel dose measurements...

Purpose: In this paper we present work to further develop and characterize a novel method of reading radiochromic film. The technique is benchmarked against imaging on a clinically used Epson 10000XL scanner, using well characterized standard dose deliveries and patient IMRT QA results. Methods: A purpose-built CCD camera-based film digitizer wa...

Purpose: Sophisticated dose calculation algorithms based on principles of convolution theory are commonly used in commercial treatment planning systems for calculating photon dose from point-like radiation sources. However, not much has been studied regarding the modeling of distributed sources such as a Cobalt-60 (Co-60) source of 2 cm diameter....

Radiochromic micelle gel dosimeters are promising for three-dimensional (3D) radiation dosimetry because they can be read out by optical CT techniques and they have superior spatial stability compared to polymer and Fricke gel dosimeters. This study evaluates the use of diacetylenes as reporter molecules in micelle gel dosimeters. Several gels cont...

Radiation therapy treatment modalities continue to develop and have become increasingly complex. With this, dose verification and quality assurance (QA) is of great importance to ensure that a prescribed dose is accurately and precisely delivered to a patient. Radiochromic film dosimetry has been adopted as a convenient option for QA, because it is...

Image guidance capability is an important feature of modern radiotherapy machines. Cobalt‐60 units will require some form of image guidance if they are to be brought up to modern standards. Imaging in the treatment beam is an appealing option, for reasons of simplicity and cost, but the dose needed to produce cone beam CT images in a Co‐60 treatmen...

The January 2010 articles in The New York Times generated intense focus on patient safety in radiation treatment, with physics staffing identified frequently as a critical factor for consistent quality assurance. The purpose of this work is to review our experience with medical physics staffing, and to propose a transparent and flexible staffing al...

The finite size pencil beam (FSPB) superposition method is a commonly used dose calculation method in intensity modulated radiation therapy (IMRT). The FSPB model assumes that dose for a broad intensity modulated beam can be calculated by superposition of dose from small, pencil-like beams. However, this model is limited to point-like radiation sou...

A model is developed to simulate the response of polyacrylamide gel (PAG) dosimeters to single spherical brachytherapy seeds. The model predicts the amount of polymer formed and crosslink density as a function of radial distance and time, using either a HDR Ir192 seed or a LDR I125 seed. Results indicate that PAG dosimeters should provide accurate...

A dynamic PDE model is developed to simulate the effects of radiation depth doses on polymer formation in polyacrylamide gel dosimeters. Depth doses are simulated using different types of radiation including Co60 g and 6 and 15 MV X-ray photon beams, along with 6, 9, 12, 16 and 20 MeV electron beams. Effects of monomer diffusion (edge enhancement)...

Purpose: To investigate possible applications of a Cobalt‐60 (Co 60) cone‐beam megavoltage computed tomography (CoCBCT) imaging system, developed for patient positioning on Co‐60 teletherapy machines, in non‐clinical fields such as archaeology and non‐destructive testing. Methods: CoCBCT scans were performed on a series of dense objects requiring n...

Purpose: To develop and use a common phantom system to characterize and compare 2D and 3D data from different intensity modulated radiation therapy(IMRT)quality assurance (QA) measurement tools. Method and Materials:The IMRT QA tools under consideration in this work are: a) Single ion chamber, b) 2D matrix ion chamber, c) Gafchromic film, d) EPID‐b...

Purpose: To describe an algorithm for determining appropriate physics staffing for radiation treatment. Motivation for this work came from the age of current guidelines which predate the recent evolution in techniques and technology, and also several significant adverse incidents where a lack of physics staffing was identified as a contributing fac...

Purpose: To develop a novel DNAdosimeter for accurate dose measurements in a broad spectrum of therapeutics beams including contaminated x?ray fields. Methods: Monte Carlo simulations were used to evaluate the DNAdosimeter for surface dosedetection. The dosedeposited to the detector while on the surface of a cylindrical tissue phantom was compared...

Brachytherapy is an important mode of breast cancer treatment; however, improvements in both treatment planning and delivery are needed. In order to meet these specific needs, integration of pre-operative imaging, supplemented by computerized surgical planning and mathematical optimization were used to develop and test an intra-operative immobiliza...

This work develops imaging protocols for improved dose readout of a Fricke-xylenol orange-gelatin (FXG) gel-filled 1 L polyethylene terephthalate (PETE) jar dosimeter using a commercial Vista(TM) cone-beam optical computed tomography (CT) scanner from Modus Medical Devices Inc. (London, ON, Canada). To ensure good management of light source-detecto...

This study reports new N-isopropylacrylamide (NIPAM) polymer gel recipes with increased dose sensitivity and improved dose resolution for x-ray CT readout. NIPAM can be used to increase the solubility of N, N'-methylenebisacrylamide (Bis) in aqueous solutions from approximately 3% to 5.5% by weight, enabling the manufacture of dosimeters containing...

This paper explores the combination of cone beam optical computed tomography with an N-isopropylacrylamide (NIPAM)-based polymer gel dosimeter for three-dimensional dose imaging of small field deliveries. Initial investigations indicate that cone beam optical imaging of polymer gels is complicated by scattered stray light perturbation. This can lea...

In wet hen egg white lysozyme (HEWL), the molecular dynamics at the lysozyme–water interface was studied using a proton NMR line-shape-relaxation correlation approach that employed selective inversion of the proton magnetization. The intrinsic lysozyme proton spin-lattice relaxation rate, the intrinsic water proton spin-lattice relaxation rate, and...

A reporter molecule consisting of a synthetic oligonucleotide is being characterised for a novel damage detection scenario for its potential use as a field-deployable, personal deoxyribonucleic acid (DNA) dosemeter for radiation detection. This dosemeter is devoid of any biological properties other than being naked DNA and therefore has no DNA repa...

Linear dose response in the range 0–30 Gy was observed in spin-lattice and spin-spin relaxation rates of water protons in 10 wt% sugar Fricke solutions at 300 MHz and 25 MHz. Spin-lattice dose sensitivities were higher at 300 MHz (0.058 s−1 Gy−1 with xylenol orange, 0.024 s−1 Gy−1 without) than at 25 MHz (0.047 s−1 Gy−1 with xylenol orange, 0.026 s...

Polymer gels are chemical dosimeters based on dose dependent radiation-induced polymerization and cross-linking of monomers in an irradiated volume. The changes are spatially localized in the volume by incorporating the initial monomers in an aqueous gel matrix in the dosimeter and can be probed by various imaging techniques such as magnetic resona...

The details of a calibration basis for the Fricke-xylenol orange-gelatin (FXG) gel dosimeter combined with the fast, easily accessible readout tool of cone beam optical computed tomography (CT) are described in this report. With proper controls in place, the results from a test intensity modulated radiation therapy (IMRT) treatment plan evaluation...

In-phantom Fricke-xylenol orange-gelatin (FXG) gel dosimetry yields three dimensional (3D) dose data for intensity modulated radiation therapy (IMRT) treatment plan verification within 18–24 hours from the point of request. The information obtained from a 3% dose difference, 3 mm distance-to-agreement gamma function comparison between treatment pla...

A dynamic partial differential equation (PDE) model is used to simulate effects of a single Ir192 brachytherapy seed on the amount and composition of polymer formed during polyacrylamide gel (PAG) dosimetry. Simulations are conducted for a point-source brachytherapy seed placed at the center of a 6%T 50% C anoxic PAG phantom. The seed is removed af...

A dynamic partial differential equation (PDE) model is used to simulate the effects of radiation depth-doses on polymer formation in Polyacrylamide Gel (PAG) dosimeters. Depth-doses are simulated using different types of radiation including Co60 gamma and 6 and 15 MV X-ray photon beams, along with 6, 9, 12, 16 and 20 MeV electron beams. Effects of...

The finite size pencil beam (FSPB) superposition method is commonly used to calculate dose for intensity modulated beams in IMRT. The FSPB model assumes that broad beam dose from a radiation originating from a point source can be calculated by a superposition of dose from pencil beams. For finite size sources, such as a Cobalt‐60 (Co‐60) source of...

Our centre is currently undergoing a major expansion, including the construction of two new linear acceleratorradiotherapy bunkers and the addition of extra shielding to existing bunkers. While shielding material is typically specified by Tenth?Value Layer (TVL) at the design stage, the concrete supplier will specify the (wet) densities of the conc...

Accessibility is essential to providing quality health care. Our research work has shown that Cobalt‐60 (Co‐60) treatment can be modernized to provide intensity modulated radiation therapy(IMRT). The use of Co‐60 as a radiationsource could provide a solution in parts of the world with limited infrastructure to support linac therapy. Previous work h...

Purpose: Cobalt?60 (Co?60) based radiation therapy continues to play a significant role in a large number of countries due its simplicity and robustness. However, it has not been developed to accommodate modern techniques that provide intensity modulated radiation therapy(IMRT). In this paper we present the results of investigations of Co?60 based...

The ongoing development of easily accessible, fast optical readout tools promises to remove one of the barriers to acceptance of gel dosimetry as a viable tool in cancer clinics. This paper describes the characterization of a number of basic properties of the Vista cone beam CCD-based optical scanner, which can obtain high resolution reconstructed...

Underdosing of treatment targets can occur in radiation therapy due to electronic disequilibrium around air-tissue interfaces when tumors are situated near natural air cavities. These effects have been shown to increase with the beam energy and decrease with the field size. Intensity modulated radiation therapy (IMRT) and tomotherapy techniques emp...

Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. These gel dosimeters, with the capacity to uniquely record the radiation dose distribution in three-dimensions (3D), have specific advantages when compared to one-dimensional dosimeters, such as...

A mathematical model for crosslinking copolymerization of acrylamide (or NIPAM) and N,N ' ‐ methylenebisacrylamide is extended to account for contamination by oxygen and the inhibitor MEHQ. This model improves basic understanding of interactions among oxygen, MEHQ and polymerization reactions in gel dosimeters that are used to verify radiation dose...

Three dimensional geldosimetry has become more clinically practical with the development of normoxic and less toxic polymergels and of new accessible imaging techniques for dose readout. In this paper we describe the application of NIPAM polymer and Fricke xylenol (FXG) gels to image?guidedadaptive radiation therapy (IGART). The geldosimetry was pe...

Intensity Modulated Radiation Therapy(IMRT) is becoming the standard of care for a number of cancer sites. Our research work has focused on developing Co?60 based IMRT as an alternative for those areas in the world with limited infrastructure for supporting LINAC based systems. We have, to date, considered Co?60 IMRT based on the tomotherapy approa...

The ability for megavoltage computed tomography patient setup verification using a cobalt‐60 (Co‐60) gamma ray source has already been established in the context of cobalt tomotherapy by our group. However, it would be beneficial to establish improved cobaltimaging that could be used on more conventional units. Digital tomosynthesis (DT) is an imag...

The advances in modern radiation therapy with techniques such as intensity-modulated radiation therapy and image-guided radiation therapy (IMRT and IGRT) have been limited almost exclusively to linear accelerators. Investigations of modern Cobalt-60 (Co-60) radiation delivery in the context of IMRT and IGRT have been very sparse, and have been limi...

Cobalt-60 (Co-60) based radiation therapy continues to play a significant role in not only developing countries, where access to radiation therapy is extremely limited, but also in industrialized countries. Howver, technology has to be developed to accommodate modern techniques, including image guided and adaptive radiation therapy (IGART). In this...

For over a decade our community has considered gel dosimetry a promising technique for the clinic, since it provides a unique methodology for three dimensionally dose measurement of the complex conformal dose distributions achieved by modern techniques such as Intensity Modulated Radiation Therapy. Even with improved gel dosimeters (such as normoxi...

Cone beam optical computed tomography (OptCT) employing the VISTA scanner (Modus Medical, London, ON) has been shown to have significant promise for fast, three dimensional imaging of polymer gel dosimeters. One distinct challenge with this approach arises from the combination of the cone beam geometry, a diffuse light source, and the scattering po...

Standard water-based acrylic emulsion scattering solutions have been developed for use in optical scattering gel phantoms. These solutions display good uniformity and long term stability, and can be index matched to polymer gels through the addition of propylene glycol or molten gelatin. Preliminary quality assurance (QA) performed on the Vista con...

Nuclear magnetic resonance was critical to the development of gel dosimetry, as it established the potential for three dimensional dosimetry with chemical dosimeter systems through magnetic resonance imaging [1]. In the last two decades MRI has served as the gold standard for imaging, while NMR relaxometry has played an important role in the develo...