bluuebunny/crossref_metadata_2025_split huggingface dataset:
WE‐DE‐201‐10: Pitfalls When Using Ruby as An Inorganic Scintillator Detector for Ir‐192 Brachytherapy Dosimetry
Authors: Kertzscher G , Beddar S 
Published: July 2016

Purpose:To study the promising potential of inorganic scintillator detectors (ISDs) and investigate various unwanted luminescence properties which may compromise their accuracy.Methods:The ISDs were comprised of a ruby crystal coupled to a polymethyl methacrylate (PMMA) fiber‐optic cable and a charged coupled device camera. A new type of ISD was manufactured and included a long‐pass filter that was sandwiched between the crystal and the fiber‐optic cable. The purpose of the filter was to suppress the Cerenkov and fluorescence background light induced in the PMMA (the stem signal) from striking the ruby crystal, generating unwanted ruby excitation. A variety of experiments were performed to characterize the ruby based ISDs. The relative contribution of the induced ruby signal and the stem signal were quantified while exposing the detector and a bare fiber‐optic cable to a high dose rate (HDR) brachytherapy (BT) source, respectively. The unwanted ruby excitation was quantified while irradiating the fiber‐optic cable with the detector volume shielded. Other experiments addressed time‐dependent luminescence properties and a comparison to other commonly used organic scintillator detectors (BCF‐12, BCF‐60).Results:When the BT source dwelled 0.5 cm away from the fiber‐optic cable, the unwanted ruby excitation amounted to >5% of the total signal if the source‐distance from the scintillator was >7 cm. However, the unwanted excitation was suppressed to <1% if the ISD incorporated an optic filter. The stem signal was suppressed with a 20 nm band‐pass filter and was <3% as long as the source‐distance was <7 cm. The ruby based ISDs generated signal up to 20(40) times that of BCF‐12(BCF‐60).Conclusion:The study presents solutions to unwanted luminescence properties of ruby based ISDs for HDR BT. An optic filter should be sandwiched between the scintillator volume and the fiber‐optic cable to prevent the stem signal to excite the ruby crystal.
WE‐D‐BRB‐04: Clinical Applications of CBCT for Proton Therapy
Authors: Teo B. 
Published: July 2016

The goal of this session is to review the physics of proton therapy, treatment planning techniques, and the use of volumetric imaging in proton therapy. The course material covers the physics of proton interaction with matter and physical characteristics of clinical proton beams. It will provide information on proton delivery systems and beam delivery techniques for double scattering (DS), uniform scanning (US), and pencil beam scanning (PBS). The session covers the treatment planning strategies used in DS, US, and PBS for various anatomical sites, methods to address uncertainties in proton therapy and uncertainty mitigation to generate robust treatment plans. It introduces the audience to the current status of image guided proton therapy and clinical applications of CBCT for proton therapy. It outlines the importance of volumetric imaging in proton therapy.

Learning Objectives:
Gain knowledge in proton therapy physics, and treatment planning for proton therapy including intensity modulated proton therapy.
The current state of volumetric image guidance equipment in proton therapy.
Clinical applications of CBCT and its advantage over orthogonal imaging for proton therapy.B. Teo, B.K Teo had received travel funds from IBA in 2015.
WE‐DE‐201‐12: Thermal and Dosimetric Properties of a Ferrite‐Based Thermo‐Brachytherapy Seed
Authors: Warrell G , Shvydka D , Parsai E I 
Published: July 2016

Purpose:The novel thermo‐brachytherapy (TB) seed provides a simple means of adding hyperthermia to LDR prostate permanent implant brachytherapy. The high blood perfusion rate (BPR) within the prostate motivates the use of the ferrite and conductive outer layer design for the seed cores. We describe the results of computational analyses of the thermal properties of this ferrite‐based TB seed in modelled patient‐specific anatomy, as well as studies of the interseed and scatter (ISA) effect.Methods:The anatomies (including the thermophysical properties of the main tissue types) and seed distributions of 6 prostate patients who had been treated with LDR brachytherapy seeds were modelled in the finite element analysis software COMSOL, using ferrite‐based TB and additional hyperthermia‐only (HT‐only) seeds. The resulting temperature distributions were compared to those computed for patient‐specific seed distributions, but in uniform anatomy with a constant blood perfusion rate. The ISA effect was quantified in the Monte Carlo software package MCNP5.Results:Compared with temperature distributions calculated in modelled uniform tissue, temperature distributions in the patient‐specific anatomy were higher and more heterogeneous. Moreover, the maximum temperature to the rectal wall was typically ∼1 °C greater for patient‐specific anatomy than for uniform anatomy. The ISA effect of the TB and HT‐only seeds caused a reduction in D90 similar to that found for previously‐investigated NiCu‐based seeds, but of a slightly smaller magnitude.Conclusion:The differences between temperature distributions computed for uniform and patient‐specific anatomy for ferrite‐based seeds are significant enough that heterogeneous anatomy should be considered. Both types of modelling indicate that ferrite‐based seeds provide sufficiently high and uniform hyperthermia to the prostate, without excessively heating surrounding tissues. The ISA effect of these seeds is slightly less than that for the previously‐presented NiCu‐based seeds.
WE‐D‐BRB‐00: Basics of Proton Therapy
Authors: Arjomandy Bijan , Hua Chia‐Ho 
Published: July 2016

The goal of this session is to review the physics of proton therapy, treatment planning techniques, and the use of volumetric imaging in proton therapy. The course material covers the physics of proton interaction with matter and physical characteristics of clinical proton beams. It will provide information on proton delivery systems and beam delivery techniques for double scattering (DS), uniform scanning (US), and pencil beam scanning (PBS). The session covers the treatment planning strategies used in DS, US, and PBS for various anatomical sites, methods to address uncertainties in proton therapy and uncertainty mitigation to generate robust treatment plans. It introduces the audience to the current status of image guided proton therapy and clinical applications of CBCT for proton therapy. It outlines the importance of volumetric imaging in proton therapy.

Learning Objectives:
Gain knowledge in proton therapy physics, and treatment planning for proton therapy including intensity modulated proton therapy.
The current state of volumetric image guidance equipment in proton therapy.
Clinical applications of CBCT and its advantage over orthogonal imaging for proton therapy.B. Teo, B.K Teo had received travel funds from IBA in 2015.
WE‐DE‐BRA‐01: SCIENCE COUNCIL JUNIOR INVESTIGATOR COMPETITION WINNER: Acceleration of a Limited‐Angle Intrafraction Verification (LIVE) System Using Adaptive Prior Knowledge Based Image Estimation
Authors: Zhang Y , Yin F , Zhang Y , Ren L 
Published: July 2016

Purpose:To develop an adaptive prior knowledge based image estimation method to reduce the scan angle needed in the LIVE system to reconstruct 4D‐CBCT for intrafraction verification.Methods:The LIVE system has been previously proposed to reconstructs 4D volumetric images on‐the‐fly during arc treatment for intrafraction target verification and dose calculation. This system uses limited‐angle beam's eye view (BEV) MV cine images acquired from the treatment beam together with the orthogonally acquired limited‐angle kV projections to reconstruct 4D‐CBCT images for target verification during treatment. In this study, we developed an adaptive constrained free‐form deformation reconstruction technique in LIVE to further reduce the scanning angle needed to reconstruct the CBCT images. This technique uses free form deformation with energy minimization to deform prior images to estimate 4D‐CBCT based on projections acquired in limited angle (orthogonal 6°) during the treatment. Note that the prior images are adaptively updated using the latest CBCT images reconstructed by LIVE during treatment to utilize the continuity of patient motion.The 4D digital extended‐cardiac‐torso (XCAT) phantom was used to evaluate the efficacy of this technique with LIVE system. A lung patient was simulated with different scenario, including baseline drifts, amplitude change and phase shift. Limited‐angle orthogonal kV and beam's eye view (BEV) MV projections were generated for each scenario. The CBCT reconstructed by these projections were compared with the ground‐truth generated in XCAT.Volume‐percentage‐difference (VPD) and center‐of‐mass‐shift (COMS) were calculated between the reconstructed and the ground‐truth tumors to evaluate the reconstruction accuracy.Results:Using orthogonal‐view of 6° kV and BEV‐ MV projections, the VPD/COMS values were 12.7±4.0%/0.7±0.5 mm, 13.0±5.1%/0.8±0.5 mm, and 11.4±5.4%/0.5±0.3 mm for the three scenarios, respectively.Conclusion:The technique enables LIVE to accurately reconstruct 4D‐CBCT images using only orthogonal 6° angle, which greatly improves the efficiency and reduces dose of LIVE for intrafraction verification.
WE‐DE‐BRA‐03: Construction of An Ultrasound Guidance Platform for Image‐Guided Radiotherapy with the Intent to Treat Transitional Cell Carcinoma
Authors: Sick J , Rancilio N , Fulkerson C , LaPetina P , Poulson J , Knapp D , Stantz K 
Published: July 2016

Purpose:Ultrasound (US) is a noninvasive, nonradiographic imaging technique with high spatial and temporal resolution that can be used for localizing soft‐tissue structures and tumors in real‐time during radiotherapy (inter‐ and intra‐fraction). A detailed methodology integrating 3D‐US within RT is presented. This method is easier to adopt into current treatment protocol than current US based systems and reduces user variability for image acquisition, thus eliminating transducer induced changes that limit CT planning system.Methods:We designed an in‐house integrated US manipulator and platform to relate CT, 3D‐US and linear accelerator coordinate systems. To validate the platform, an agar‐based phantom with measured densities and speed‐of‐sound consistent with tissues surrounding the bladder, was rotated (0–45°) resulting in translations (up to 55mm) relative to the CT and US coordinate systems. After acquiring and integrating CT and US images into the treatment planning system, US‐to‐US and US‐to‐CT images were co‐registered to re‐align the phantom relative to the linear accelerator. Errors in the transformation matrix components were calculate to determine precision of this method under different patient positions.Results:Statistical errors from US‐US registrations for different patient orientations ranged from 0.06–1.66mm for x, y, and z translational components, and 0.00–1.05° for rotational components. Statistical errors from US‐CT registrations were 0.23–1.18mm for the x, y and z translational components, and 0.08–2.52° for the rotational components.Conclusion:Based on our result, this is consistent with currently used techniques for positioning prostate patients if couch re‐positioning is less than a 5 degree rotation. We are now testing this on a dog patient to obtain both inter and intra‐fractional positional errors. Additional design considerations include the future use of ultrasound‐based functionality (photoacoustics, radioacoustics, Doppler) to monitor blood flow and hypoxia and/or in‐vivo dosimetry for applications in other therapeutic techniques, such as hyperthermia, anti‐angiogenesis, and particle therapy.
WE‐DE‐BRA‐05: Monte Carlo Simulation of a Novel Multi‐Layer MV Imager
Authors: Myronakis M , Rottmann J , Hu Y , Wang A , Shedlock D , Morf D , Star‐Lack J , Berbeco R 
Published: July 2016

Purpose:To develop and validate a Monte Carlo (MC) model of a novel multi‐layer imager (MLI) for megavolt (MV) energy beams. The MC model will enable performance optimization of the MLI design for clinical applications including patient setup verification, tumor tracking and MVCBCT.Methods:The MLI is composed of four layers of converter, scintillator and light detector, each layer similar to the current clinical AS1200 detector (Varian Medical Systems, Inc). The MLI model was constructed using the Geant4 Application for Tomographic Emission (GATE v7.1) and includes interactions for x‐ray photons, charged particles and optical photons. Computational experiments were performed to assess Modulation Transfer Function (MTF), Detective Quantum Efficiency (DQE) and Noise Power Spectrum normalized by photon fluence and average detector signal (qNNPS). Results were compared with experimental measurements. The current work incorporates, in one model, the complete chain of events occurring in the imager; i.e. starting from x‐ray interaction to charged particle transport and energy deposition to subsequent generation, interactions and detection of optical photons.Results:There is good agreement between measured and simulated MTF, qNNPS and DQE values. Normalized root mean squared error (NRMSE) between measured and simulated values over all four layers was 2.18%, 2.43% and 6.05% for MTF, qNNPS and DQE respectively. The relative difference between simulated and measured values for qNNPS(0) was 1.68% and 1.57% for DQE(0). Current results were obtained using a 6MV Varian Truebeam™ spectrum.Conclusion:A comprehensive Monte Carlo model of the MLI prototype was developed to allow optimization of detector components. The model was assessed in terms of imaging performance using standard metrics (i.e. MTF, qNNPS, DQE). Good agreement was found between simulated and measured values. The model will be used to assess alternative detector constructions to facilitate advanced clinical imaging applications including MV‐CBCT and tumor tracking.The project was supported, partially, by a grant from Varian Medical Systems, Inc., and Award No. R01CA188446‐01 from the National Cancer Institute. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Cancer Institute or the National Institutes of Health.
WE‐DE‐BRA‐06: Evaluation of the Imaging Performance of a Novel Water‐Equivalent EPID
Authors: Blake SJ , Cheng J , Vial P , Lu M , Atakaramians S , Meikle S , Kuncic Z 
Published: July 2016

Purpose:To evaluate the megavoltage imaging performance of a novel, water‐equivalent electronic portal imaging device (EPID) developed for simultaneous imaging and dosimetry applications in radiotherapy.Methods:A novel EPID prototype based on active matrix flat panel imager technology has been developed by our group and previously reported to exhibit a water‐equivalent dose response. It was constructed by replacing all components above the photodiode detector in a standard clinical EPID (including the copper plate and phosphor screen) with a 15 × 15 cm2 array of plastic scintillator fibers. Individual fibers measured 0.5 × 0.5 × 30 mm3. Spatial resolution was evaluated experimentally relative to that of a standard EPID with the thin slit technique to measure the modulation transfer function (MTF) for 6 MV x‐ray beams. Monte Carlo (MC) EPID models were used to benchmark simulated MTFs against the measurements. The zero spatial frequency detective quantum efficiency (DQE(0)) was simulated for both EPID configurations and a preliminary optimization of the prototype was performed by evaluating DQE(0) as a function of fiber length up to 50 mm.Results:The MC‐simulated DQE(0) for the prototype EPID configuration was ∼7 times greater than that of the standard EPID. The prototype's DQE(0) also increased approximately linearly with fiber length, from ∼1% at 5 mm length to ∼11% at 50 mm length. The standard EPID MTF was greater than the prototype EPID's for all spatial frequencies, reflecting the trade off between x‐ray detection efficiency and spatial resolution with thick scintillators.Conclusion:This study offers promising evidence that a water‐equivalent EPID previously demonstrated for radiotherapy dosimetry may also be used for radiotherapy imaging applications. Future studies on optimising the detector design will be performed to develop a next‐generation prototype that offers improved megavoltage imaging performance, with the aim to at least match that of current clinical EPIDs.Funding for this project was provided by an Australian Research Council Linkage Project grant (2015) between The University of Sydney, South Western Sydney Local Health District and Perkin‐Elmer Pty Ltd.
WE‐DE‐BRA‐07: Megavoltage Spectral Imaging with a Layered Detector
Authors: Myronakis M , Rottmann J , Hu Y , Wang A , Shedlock D , Morf D , Star‐Lack J , Berbeco R 
Published: July 2016

Purpose:The aim of the current work is to investigate the feasibility of megavoltage spectral imaging using a multiple layered detector for enhancement of low contrast detectability through material segmentation and discrimination (such as bone, markers and metal implants). Potentially the technique can be applied to improve detection and reduce dose in Megavoltage Cone Beam Computed Tomography (MV‐CBCT).Methods:Experiments were performed with a prototype multi‐layer imager (MLI) which has higher detective efficiency and lower noise characteristics than conventional Electronic Portal Imaging Devices (EPIDs). Images of a solid water phantom were acquired at 2.5 MV, 6MV and 6MV without flattening filter (FFF). The following materials were placed within a stack of solid water: aluminum, copper and gold. Material separation was assessed based on Contrast‐to‐Noise Ratio (CNR) of the weighted image, formed by a weighted subtraction of the images from two layers of the MLI. A range of weighting factors were investigated for material separation.Results:CNR can be minimized for each material by appropriate selection of the subtraction weighting factor. This is equivalent to a selective subtraction of specific materials from the image. Using multiple layers simultaneously also decreases the dose requirement and removes any registration errors. The minimum CNR for aluminum, copper and gold at the weighted image formed with 2.5MV was obtained at weighting factors equal to 0.92, 0.76 and 0.64 respectively. The corresponding values at 6MVFFF were 0.99, 0.92 and 0.78 respectively.Conclusion:In the current work, an MV spectral imaging feasibility study was attempted using a novel multi‐layer prototype EPID imager. Initial results suggest that material separation based on spectral differences between different layers is possible. This spectral imaging technique has potential advantages in MV‐CBCT for real‐time target tracking, patient set‐up imaging and adaptive radiotherapy.The project was supported, partially, by a grant from Varian Medical Systems, Inc., and Award No. R01CA188446‐01 from the National Cancer Institute. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Cancer Institute or the National Institutes of Health
WE‐DE‐202‐03: Modeling of Biological Processes ‐ What Happens After Early Molecular Damage?
Authors: McMahon S. 
Published: July 2016

Radiation therapy for the treatment of cancer has been established as a highly precise and effective way to eradicate a localized region of diseased tissue. To achieve further significant gains in the therapeutic ratio, we need to move towards biologically optimized treatment planning. To achieve this goal, we need to understand how the radiation‐type dependent patterns of induced energy depositions within the cell (physics) connect via molecular, cellular and tissue reactions to treatment outcome such as tumor control and undesirable effects on normal tissue.Several computational biology approaches have been developed connecting physics to biology. Monte Carlo simulations are the most accurate method to calculate physical dose distributions at the nanometer scale, however simulations at the DNA scale are slow and repair processes are generally not simulated. Alternative models that rely on the random formation of individual DNA lesions within one or two turns of the DNA have been shown to reproduce the clusters of DNA lesions, including single strand breaks (SSBs), double strand breaks (DSBs) without the need for detailed track structure simulations. Efficient computational simulations of initial DNA damage induction facilitate computational modeling of DNA repair and other molecular and cellular processes. Mechanistic, multiscale models provide a useful conceptual framework to test biological hypotheses and help connect fundamental information about track structure and dosimetry at the sub‐cellular level to dose‐response effects on larger scales.In this symposium we will learn about the current state of the art of computational approaches estimating radiation damage at the cellular and sub‐cellular scale. How can understanding the physics interactions at the DNA level be used to predict biological outcome? We will discuss if and how such calculations are relevant to advance our understanding of radiation damage and its repair, or, if the underlying biological processes are too complex for a mechanistic approach. Can computer simulations be used to guide future biological research? We will debate the feasibility of explaining biology from a physicists’ perspective.

Learning Objectives:
Understand the potential applications and limitations of computational methods for dose‐response modeling at the molecular, cellular and tissue levels
Learn about mechanism of action underlying the induction, repair and biological processing of damage to DNA and other constituents
Understand how effects and processes at one biological scale impact on biological processes and outcomes on other scalesJ. Schuemann, NCI/NIH grantsS. McMahon, Funding: European Commission FP7 (grant EC FP7 MC‐IOF‐623630)
WE‐DE‐206‐03: MRI Image Formation ‐ Slice Selection, Phase Encoding, Frequency Encoding, K‐Space, SNR
Authors: Lin C. 
Published: July 2016

Magnetic resonance imaging (MRI) has become an essential part of clinical imaging due to its ability to render high soft tissue contrast. Instead of ionizing radiation, MRI use strong magnetic field, radio frequency waves and field gradients to create diagnostic useful images. It can be used to image the anatomy and also functional and physiological activities within the human body. Knowledge of the basic physical principles underlying MRI acquisition is vitally important to successful image production and proper image interpretation.This lecture will give an overview of the spin physics, imaging principle of MRI, the hardware of the MRI scanner, and various pulse sequences and their applications. It aims to provide a conceptual foundation to understand the image formation process of a clinical MRI scanner.

Learning Objectives:
Understand the origin of the MR signal and contrast from the spin physics level.
Understand the main hardware components of a MRI scanner and their purposes
Understand steps for MR image formation including spatial encoding and image reconstruction
Understand the main kinds of MR pulse sequences and their characteristics.