bluuebunny/crossref_metadata_2025 huggingface dataset:
WE‐DE‐BRC‐04: Fault‐Tree Analysis
Authors: Thomadsen B.
Published: July 2016

This SAMs Therapy Educational Course will introduce participants to the tools recommended by TG 100 for use in the development of a risk‐based Quality Management Program. The Course will start with an Overview of the background and rationale behind the TG 100 initiative, from which its charge was developed. After setting the scene, four 15 minute presentations will introduce the principal components of the soon to be published Report of TG 100. These are Process Mapping, Failure Modes and Effects Analysis, Fault Tree Analysis and the development of a QA/QM risk‐based Program. There will be time for two short exercises based on Failure Modes and Effects Analysis and a Discussion before the SAMs questions which will conclude the session.

Learning Objectives:

To appreciate the underlying philosophy of the TG 100 initiative.

To gain a brief overview of the principal risk‐based tools recommended by TG 100.

In an informal workshop format, to explore, at an introductory level, the use of risk analysis as proposed by TG 100 as a prelude to the development of a Quality Management Program.
WE‐DE‐BRC‐05: Risk‐Based QA/QM Programs
Authors: Yorke E.
Published: July 2016

This SAMs Therapy Educational Course will introduce participants to the tools recommended by TG 100 for use in the development of a risk‐based Quality Management Program. The Course will start with an Overview of the background and rationale behind the TG 100 initiative, from which its charge was developed. After setting the scene, four 15 minute presentations will introduce the principal components of the soon to be published Report of TG 100. These are Process Mapping, Failure Modes and Effects Analysis, Fault Tree Analysis and the development of a QA/QM risk‐based Program. There will be time for two short exercises based on Failure Modes and Effects Analysis and a Discussion before the SAMs questions which will conclude the session.

Learning Objectives:

To appreciate the underlying philosophy of the TG 100 initiative.

To gain a brief overview of the principal risk‐based tools recommended by TG 100.

In an informal workshop format, to explore, at an introductory level, the use of risk analysis as proposed by TG 100 as a prelude to the development of a Quality Management Program.
WE‐DE‐BRA‐08: A Linear Accelerator Target Allowing Rapid Switching Between Treatment and High‐Contrast Imaging Modes
Authors: Yewondwossen M , Robar J , Parsons D
Published: July 2016

Purpose:

During radiotherapy treatment, lung tumors can display substantial respiratory motion. This motion usually necessitates enlarged treatment margins to provide full tumour coverage. Unfortunately, these margins limit the dose that can be prescribed for tumour control and cause complications to normal tissue. Options for real‐time methods of direct detection of tumour position, and particularly those that obviate the need for inserted fiducial markers, are limited. We propose a method of tumor tracking without implanted fiducial markers using a novel fast switching‐target that toggles between a FFF copper/tungsten therapy mode and a FFF low‐Z target mode for imaging. In this work we demonstrate proof‐of‐concept of this new technology.

Methods:

The prototype includes two targets: i) a FFF copper/tungsten target equivalent to that in the Varian 2100 EX 6 MV, and ii) a low‐Z (carbon) target with a thickness of 110% of continuous slowing down approximation range (CSDA) at 7 MeV. The two targets can be exchanged with a custom made linear slide and motor‐driven actuator. The usefulness of the switching‐target concept is demonstrated through experimental BEV Planar images acquired with continual treatment and imaging at a user‐defined period.

Results:

The prototype switching‐target demonstrates that two recent advances in linac technology (FFF target for therapy and low‐Z target) can be combined with synergy. The switching‐target approach offers the capacity for rapid switching between treatment and high‐contrast imaging modes, allowing intrafractional tracking, as demonstrated in this work with dynamic breathing phantom. By using a single beam‐line, the design is streamlined and may obviate the need for an auxiliary imaging system (e.g., kV OBI.)

Conclusion:

This switching‐target approach is a feasible combination of two current advances in linac technology (FFF target for therapy and a FFF low‐Z target) allowing new options in on‐line IGRT.
WE‐DE‐BRA‐09: Fast Megavoltage CT Imaging with Rapid Scan Time and Low Imaging Dose in Helical Tomotherapy
Authors: Magome T , Haga A , Takahashi Y , Nakagawa K , Dusenbery K , Hui S
Published: July 2016

Purpose:

Megavoltage computed tomography (MVCT) imaging has been widely used for daily patient setup with helical tomotherapy (HT). One drawback of MVCT is its very long imaging time, owing to slow couch speed. The purpose of this study was to develop an MVCT imaging method allowing faster couch speeds, and to assess its accuracy for image guidance for HT.

Methods:

Three cadavers (mimicking closest physiological and physical system of patients) were scanned four times with couch speeds of 1, 2, 3, and 4 mm/s. The resulting MVCT images were reconstructed using an iterative reconstruction (IR) algorithm. The MVCT images were registered with kilovoltage CT images, and the registration errors were compared with the errors with conventional filtered back projection (FBP) algorithm. Moreover, the fast MVCT imaging was tested in three cases of total marrow irradiation as a clinical trial.

Results:

Three‐dimensional registration errors of the MVCT images reconstructed with the IR algorithm were significantly smaller (p < 0.05) than the errors of images reconstructed with the FBP algorithm at fast couch speeds (3, 4 mm/s). The scan time and imaging dose at a speed of 4 mm/s were reduced to 30% of those from a conventional coarse mode scan. For the patient imaging, a limited number of conventional MVCT (1.2 mm/s) and fast MVCT (3 mm/s) reveals acceptable reduced imaging time and dose able to use for anatomical registration.

Conclusion:

Fast MVCT with IR algorithm maybe clinically feasible alternative for rapid 3D patient localization. This technique may also be useful for calculating daily dose distributions or organ motion analyses in HT treatment over a wide area.
WE‐DE‐202‐01: Connecting Nanoscale Physics to Initial DNA Damage Through Track Structure Simulations
Authors: Schuemann J.
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 scales

J. Schuemann, NCI/NIH grantsS. McMahon, Funding: European Commission FP7 (grant EC FP7 MC‐IOF‐623630)
WE‐DE‐202‐02: Are Track Structure Simulations Truly Needed for Radiobiology at the Cellular and Tissue Levels?
Authors: Stewart R.
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 scales

J. Schuemann, NCI/NIH grantsS. McMahon, Funding: European Commission FP7 (grant EC FP7 MC‐IOF‐623630)
WE‐DE‐209‐05: Self‐Held Breath Control with Respiratory Monitoring and Feedback Guidance
Authors: Gifford K.
Published: July 2016

Breast radiation therapy is associated with some risk of lung toxicity as well as cardiac toxicity for left‐sided cases. Radiation doses to the lung and heart can be reduced by using the deep inspiration breath hold (DIBH) technique, in which the patient is simulated and treated during the deep inspiration phase of the breathing cycle. During DIBH, the heart is usually displaced posteriorly, inferiorly, and to the right, effectively expanding the distance between the heart and the breast/chest wall. As a result, the distance between the medial treatment field border and heart/lung is increased. Also, in a majority of DIBH patients, the air drawn into the thoracic cavity increases the total lung volume.

The DIBH was discussed by an AAPM Task Group 10 years ago in the AAPM TG 76 report. However, DIBH is still not the standard of care in many clinics, which may be partially due to challenges associated with its implementation. Therefore, this seccion will focus primarily on how to clinically implement four different DIBH techniques: (1) Active Breathing Control, (2) Spirometric Motion Management, (3) 3D Surface Image‐Guided, and (4) Self‐held Breath Control with Respiratory Monitoring and Feedback Guidance.

Learning Objectives:

Describe the physical displacement of the heart and the change in lung volume during DIBH and discuss dosimetric consequences of those changes.

Provide an overview of the technical aspects.

Describe work flow for patient simulation and treatment.

Give an overview of commissioning and routine.

Provide practical tips for clinical implementation.
WE‐DE‐206‐02: MRI Hardware ‐ Magnet, Gradient, RF Coils
Authors: Kocharian A.
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.
WE‐DE‐209‐00: Practical Implementation of Deep Inspiration Breath Hold Techniques for Breast Radiation Therapy
Authors: Howell Rebecca
Published: July 2016

Breast radiation therapy is associated with some risk of lung toxicity as well as cardiac toxicity for left‐sided cases. Radiation doses to the lung and heart can be reduced by using the deep inspiration breath hold (DIBH) technique, in which the patient is simulated and treated during the deep inspiration phase of the breathing cycle. During DIBH, the heart is usually displaced posteriorly, inferiorly, and to the right, effectively expanding the distance between the heart and the breast/chest wall. As a result, the distance between the medial treatment field border and heart/lung is increased. Also, in a majority of DIBH patients, the air drawn into the thoracic cavity increases the total lung volume.

The DIBH was discussed by an AAPM Task Group 10 years ago in the AAPM TG 76 report. However, DIBH is still not the standard of care in many clinics, which may be partially due to challenges associated with its implementation. Therefore, this seccion will focus primarily on how to clinically implement four different DIBH techniques: (1) Active Breathing Control, (2) Spirometric Motion Management, (3) 3D Surface Image‐Guided, and (4) Self‐held Breath Control with Respiratory Monitoring and Feedback Guidance.

Learning Objectives:

Describe the physical displacement of the heart and the change in lung volume during DIBH and discuss dosimetric consequences of those changes.

Provide an overview of the technical aspects.

Describe work flow for patient simulation and treatment.

Give an overview of commissioning and routine.

Provide practical tips for clinical implementation.
WE‐DE‐209‐01: Dosimetric Benefits of DIBH
Authors: Howell R.
Published: July 2016

Breast radiation therapy is associated with some risk of lung toxicity as well as cardiac toxicity for left‐sided cases. Radiation doses to the lung and heart can be reduced by using the deep inspiration breath hold (DIBH) technique, in which the patient is simulated and treated during the deep inspiration phase of the breathing cycle. During DIBH, the heart is usually displaced posteriorly, inferiorly, and to the right, effectively expanding the distance between the heart and the breast/chest wall. As a result, the distance between the medial treatment field border and heart/lung is increased. Also, in a majority of DIBH patients, the air drawn into the thoracic cavity increases the total lung volume.

The DIBH was discussed by an AAPM Task Group 10 years ago in the AAPM TG 76 report. However, DIBH is still not the standard of care in many clinics, which may be partially due to challenges associated with its implementation. Therefore, this seccion will focus primarily on how to clinically implement four different DIBH techniques: (1) Active Breathing Control, (2) Spirometric Motion Management, (3) 3D Surface Image‐Guided, and (4) Self‐held Breath Control with Respiratory Monitoring and Feedback Guidance.

Learning Objectives:

Describe the physical displacement of the heart and the change in lung volume during DIBH and discuss dosimetric consequences of those changes.

Provide an overview of the technical aspects.

Describe work flow for patient simulation and treatment.

Give an overview of commissioning and routine.

Provide practical tips for clinical implementation.
WE‐DE‐209‐02: Active Breathing Control
Authors: Comsa D.
Published: July 2016

Breast radiation therapy is associated with some risk of lung toxicity as well as cardiac toxicity for left‐sided cases. Radiation doses to the lung and heart can be reduced by using the deep inspiration breath hold (DIBH) technique, in which the patient is simulated and treated during the deep inspiration phase of the breathing cycle. During DIBH, the heart is usually displaced posteriorly, inferiorly, and to the right, effectively expanding the distance between the heart and the breast/chest wall. As a result, the distance between the medial treatment field border and heart/lung is increased. Also, in a majority of DIBH patients, the air drawn into the thoracic cavity increases the total lung volume.

The DIBH was discussed by an AAPM Task Group 10 years ago in the AAPM TG 76 report. However, DIBH is still not the standard of care in many clinics, which may be partially due to challenges associated with its implementation. Therefore, this seccion will focus primarily on how to clinically implement four different DIBH techniques: (1) Active Breathing Control, (2) Spirometric Motion Management, (3) 3D Surface Image‐Guided, and (4) Self‐held Breath Control with Respiratory Monitoring and Feedback Guidance.

Learning Objectives:

Describe the physical displacement of the heart and the change in lung volume during DIBH and discuss dosimetric consequences of those changes.

Provide an overview of the technical aspects.

Describe work flow for patient simulation and treatment.

Give an overview of commissioning and routine.

Provide practical tips for clinical implementation.
WE‐DE‐207B‐06: Artifact Reduction in Digital Breast Tomosynthesis with the Denoised Ordered‐Subset Statistically Penalized Algebraic Reconstruction Technique (DOS‐SPART) Algorithm
Authors: Garrett J , Li Y , Li K , Chen G
Published: July 2016

Purpose:

Digital breast tomosynthesis (DBT) is an emerging breast imaging modality. It uses x‐ray absorption projection images acquired over a narrow angular span to provide high spatial resolution pseudo‐three dimensional images for breast cancer screening and diagnosis. Unfortunately, the narrow range used to acquire data (typically <30 degrees) results in significant out of plane artifacts for high contrast objects when conventional reconstruction techniques are used. In this work, the denoised ordered‐subset statistically penalized algebraic reconstruction technique (DOS‐SPART) algorithm was adapted to breast tomosynthesis imaging to reduce out‐of‐plane blurring artifacts.

Methods:

The DOS‐SPART algorithm was implemented for use with DBT datasets. The ACR mammography accreditation phantom was imaged for quantitative measurement and subjective image analysis. The artifact spread function (ASF) was measured for images generated by the commercial reconstruction method as well as DOS‐SPART with different total number of iterations (5, 10, 15, and 20). The FWHM of the ASF was used to quantify out‐of‐plane blurring. A cluster of calcifications in the ACR phantom was also inspected subjectively, and images above and below the feature were examined for artifacts.

Results:

The DOS‐SPART algorithm was able to efficiently reconstruct sharp image at the in‐focus plane, while significantly reducing out‐of‐plane blurring artifacts (total reconstruction time <90 seconds for a 1996×2457×70 voxel volume with 5 iterations). The FWHM of the ASF was reduced by as much as 35% using the algorithm. Subjectively, the out‐of‐plane artifacts from the high contrast calcification are still clearly visible in the commercial reconstruction at 1 cm above or below the in‐focus plane, whereas no artifacts from the calcification are detectable in the out‐of‐plane images generated with DOS‐SPART.

Conclusion:

The application of DOS‐SPART to DBT can help limit out‐of‐plane artifacts in DBT imaging, potentially improving localization of microcalcifications and image contrast for adjacent structures.

Funding support: This work was support in part by NIH R01 EB020521. Disclosures: J Garrett: None. Y. Li: None. K. Li: None. GH Chen: Research funded, GE Healthcare and Siemens AX
WE‐DE‐207B‐07: Hotelling Templates Without Additional Training Data for Breast Tomosynthesis Observer Models
Authors: Zeng R , Badano A
Published: July 2016

Purpose:

To describe and test a practical approach that uses minimal training data for estimating signal mean and background statistics to compute the Hotelling observer (HO) in digital breast tomosynthesis (DBT).

Methods:

Best among all linear observers, Hotelling observer (HO) is desired for many detection tasks. However, training data cost is usually high for obtaining prior information regarding the signal and data covariance. This limits the HO's utility in many practical situations. We propose that, in breast tomosynthesis images, it is feasible to estimate priors without using additional training data. The approach consists of obtaining the signal mean from a subtraction of noiseless reconstructions of a uniform background with and without signal and the noise power spectrum (NPS) computed from each breast tomosynthesis image itself, and implementing the HO in the Fourier domain. We call this approach no‐additional‐training Fourier HO (FHO). We compare this approach to the usual‐training approach with pre‐acquired training data to examine whether the resulting performances are comparable. We utilize a baseline model observer (MO) without prewhitening and an efficient MO with Laguerre‐Gauss channelized HO (LG‐CHO) to examine the efficiency of the no‐additional‐training FHO. Performance is evaluated in terms of lesion detectability using simulated DBT images corresponding to the UPENN breast phantoms with spherical lesions and two types of reconstruction.

Results:

The no‐additional‐training FHO yielded similar and even higher performance compared to the usual‐training approach in all the simulated imaging conditions. The performance improvement over non‐prewhitening MO was substantial and over LG‐CHO was also moderate, indicating a higher efficiency of the no‐additional‐training FHO in detecting lesions from the simulated DBT images.

Conclusion:

The approach to estimate HO templates without additional training data shows excellent performance with simulated breast tomosynthesis data. Its efficiency will be further tested on virtual and real patient breast tomosynthesis image sets.
WE‐DE‐207B‐09: Scatter Radiation Measurement From a Digital Breast Tomosynthesis System and Its Impact On Shielding Consideration
Authors: Yang K , Li X , Liu B
Published: July 2016

Purpose:

To accurately measure the scatter radiation from a Hologic digital breast tomosynthesis (DBT) system and to provide updated scatter distribution to guide radiation shielding calculation for DBT rooms.

Methods:

A high sensitivity GOS‐based linear detector was used to measure the angular distribution of scatter radiation from a Hologic Selenia Dimensions DBT system. The linear detector was calibrated for its energy response of typical DBT spectra. Following the NCRP147 approach, the measured scatter intensity was normalized by the primary beam area and primary air kerma at 1m from the scatter phantom center and presented as the scatter fraction. Direct comparison was made against Simpkin's initial measurement. Key parameters including the phantom size, primary beam area, and kV/anode/target combination were also studied.

Results:

The measured scatter‐to‐primary‐ratio and scatter fraction data closely matched with previous data from Simpkin. The measured data demonstrated the unique nonisotropic distribution of the scattered radiation around a Hologic DBT system, with two strong peaks around 25° and 160°. The majority scatter radiation (>70%) originated from the imaging detector assembly, instead of the phantom. With a workload from a previous local survey, the scatter air kerma at 1m from the phantom center for wall/door is 0.018mGy/patient, for floor is 0.164mGy/patient, and for ceiling is 0.037mGy/patient.

Conclusion:

Comparing to Simpkin's previous data, the scatter air kerma from Holgoic DBT is at least two times higher. The main reasons include the harder primary beam with higher workload, added tomosynthesis acquisition, and strong small angle forward scattering. Due to the highly conservative initial assumptions, the shielding recommendation from NCRP147 is still sufficient for the Hologic DBT system given the workload from a previous local survey. With the data provided from this study, accurate shielding calculation can be performed for Hologic DBT systems with specific workload and barrier distance.
WE‐C‐TOUR‐I‐01: Dosimters for QC in Diagnostic Imaging
Authors: Jiang X.
Published: July 2016

Tour Leader: Xia Jiang, Ohio State University, Columbus, OH

Tour Guides:

Xia Jiang, Ohio State University, Columbus, OH

Kevin Little, The University of Chicago, Chicago, IL

Adrien Sanchez, University of Chicago, Chicago, IL

Participating Vendors:

IBA

PTW ‐ New York

Radcal Corporation

RTI Electronics, Inc.

Exhibit Hall Guided Tours is a new program launching this year at the Annual Meeting. The Guided Tours are designed to enhance the interaction between meeting attendees and exhibitors. This year's Imaging Guided Tours are organized around the theme of dosimeters for quality control in diagnostic imaging. Tours will begin with an introduction and background given by Dr. Xia Jiang, the Tour Leader. The introduction will cover the types and properties of different radiation dosimeters used for quality assurance in clinical radiology. Attendees will then break into smaller groups, each lead by an AAPM‐member Tour Guide. The tour groups will visit the exhibit booths of vendors who provide appropriate dosimeters, and a vendor representative will give a presentation to the group about their particular product(s). The vendor representatives as well as the Tour Guides will be available to answer questions.

Outline:

Types and properties of radiation detectors and dosimeters

Ionization chamber dosimeters

Solid state dosimeters

Dosimeter calibration: Primary and secondary standards dosimetry laboratories

Instruments for measuring tube voltage and exposure time

Vendor presentations will likely cover features and innovations of different dosimeter systems, as well as their practical use.

Learning Objectives:

Understand the types and properties of different instrumentations used for quality control in diagnostic imaging.

Understand the process of dosimeter calibration.

Gain familiarity with the latest commercial dosimeter systems from different vendors.
WE‐FG‐206‐12: Enhanced Laws Textures: A Potential MRI Surrogate Marker of Hepatic Fibrosis in a Murine Model
Authors: Li B , Yu H , Jara H , Soto J , Anderson S
Published: July 2016

Purpose:

To compare enhanced Laws texture derived from parametric proton density (PD) maps to other MRI‐based surrogate markers (T2, PD, ADC) in assessing degrees of liver fibrosis in a murine model of hepatic fibrosis using 11.7T scanner.

Methods:

This animal study was IACUC approved. Fourteen mice were divided into control (n=1) and experimental (n=13). The latter were fed a DDC‐supplemented diet to induce hepatic fibrosis. Liver specimens were imaged using an 11.7T scanner; the parametric PD, T2, and ADC maps were generated from spin‐echo pulsed field gradient and multi‐echo spin‐echo acquisitions. Enhanced Laws texture analysis was applied to the PD maps: first, hepatic blood vessels and liver margins were segmented/removed using an automated dual‐clustering algorithm; secondly, an optimal thresholding algorithm was applied to reduce the partial volume artifact; next, mean and stdev were corrected to minimize grayscale variation across images; finally, Laws texture was extracted. Degrees of fibrosis was assessed by an experienced pathologist and digital image analysis (%Area Fibrosis). Scatterplots comparing enhanced Laws texture, T2, PD, and ADC values to degrees of fibrosis were generated and correlation coefficients were calculated. Unenhanced Laws texture was also compared to assess the effectiveness of the proposed enhancements.

Results:

Hepatic fibrosis and the enhanced Laws texture were strongly correlated with higher %Area Fibrosis associated with higher Laws texture (r=0.89). Only a moderate correlation was detected between %Area Fibrosis and unenhanced Laws texture (r=0.70). Strong correlation also existed between ADC and %Area Fibrosis (r=0.86). Moderate correlations were seen between %Area Fibrosis and PD (r=0.65) and T2 (r=0.66).

Conclusions:

Higher degrees of hepatic fibrosis are associated with increased Laws texture. The proposed enhancements improve the accuracy of Laws texture. Enhanced Laws texture features are more accurate than PD and T2 in assessing fibrosis, and can potentially serve as an accurate surrogate marker for hepatic fibrosis.
WE‐F‐209‐00: A Practical Guide to Radiation Safety Surveys
Authors: Dillon Chad
Published: July 2016

Over the past few years, numerous Accreditation Bodies, Regulatory Agencies, and State Regulations have implemented requirements for Radiation Safety Surveys following installation or modification to x‐ray rooms. The objective of this session is to review best practices in performing radiation safety surveys for both Therapy and Diagnostic installations, as well as a review of appropriate survey instruments.

This session will be appropriate for both therapy and imaging physicists who are looking to increase their working knowledge of radiation safety surveys.

Learning Objectives:

Identify Appropriate Survey Meters for Radiation Safety Surveys

Develop best practices for Radiation Safety Surveys for Therapy units that include common areas of concern.

Develop best practices for Radiation Safety Surveys of Diagnostic and Nuclear Medicine rooms.

Identify acceptable dose levels and the factors that affect the calculations associated with performing Radiation Safety Surveys.
WE‐FG‐207B‐01: BEST IN PHYSICS (IMAGING): Abdominal CT with Three K‐Edge Contrast Materials Using a Whole‐Body Photon‐Counting Scanner: Initial Results of a Large Animal Experiment
Authors: Lakshmanan M , Symons R , Cork T , Davies‐Venn C , Rice K , Malayeri A , Sandfort V , Bluemke D , Pourmorteza A
Published: July 2016

Purpose:

To demonstrate the feasibility of in vivo three‐material decomposition techniques using photon‐counting CT (PCCT) with possible advantage of resolving arterial and venous flow of an organ simultaneously.

Methods:

Abdominal PCCT scans were acquired using a prototype whole‐body PCCT with four energy thresholds (25/50/75/90keV) in a canine. Bismuth subsalicylate (60 mg) was administered orally one day prior to scanning. Immediately prior to CT scan, gadoteric acid (60 ml, Dotarem, Guerbet) was intravenously injected, followed in ten minutes by a 20mL injection of iodinated contrast (iopamidol 370 mg/mL, Bracco). Scans were acquired every ∼20 seconds, starting from the time of iodine injection. Linear material decomposition was performed using the least mean squares method to create concentration maps of iodine, gadolinium, and bismuth. The method was calibrated to vials with known concentrations of materials placed next to the animal. The accuracy of this method was tested on vials with known concentrations.

Results:

The material decomposition algorithm's accuracy was confirmed to be within ±4mM in the test vials. In the animal, we could estimate the concentration of gadolinium in delayed‐enhanced phase (10 minutes post‐injection) in the abdomen. We could follow the wash‐in and wash‐out of iodine in arterial, venous, and excretory flow of the kidneys (20s, 80s, and 120s post‐iodine injection) while gadolinium was present in the delayed‐enhanced phase. Bismuth, which was used as a contrast agent for the gastro‐intestinal tract, was easily differentiable from the other two contrast agents in the small intestine.

Conclusion:

This study shows the feasibility of using photon‐counting CT with four energy thresholds to differentiate three k‐edge contrast agents in vivo. This can potentially reduce radiation dose to patients by combining arterial and venous phases into a single acquisition.
WE‐FG‐207B‐05: Iterative Reconstruction Via Prior Image Constrained Total Generalized Variation for Spectral CT
Authors: Niu S , Zhang Y , Ma J , Wang J
Published: July 2016

Purpose:

To investigate iterative reconstruction via prior image constrained total generalized variation (PICTGV) for spectral computed tomography (CT) using fewer projections while achieving greater image quality.

Methods:

The proposed PICTGV method is formulated as an optimization problem, which balances the data fidelity and prior image constrained total generalized variation of reconstructed images in one framework. The PICTGV method is based on structure correlations among images in the energy domain and high‐quality images to guide the reconstruction of energy‐specific images. In PICTGV method, the high‐quality image is reconstructed from all detector‐collected X‐ray signals and is referred as the broad‐spectrum image. Distinct from the existing reconstruction methods applied on the images with first order derivative, the higher order derivative of the images is incorporated into the PICTGV method. An alternating optimization algorithm is used to minimize the PICTGV objective function. We evaluate the performance of PICTGV on noise and artifacts suppressing using phantom studies and compare the method with the conventional filtered back‐projection method as well as TGV based method without prior image.

Results:

On the digital phantom, the proposed method outperforms the existing TGV method in terms of the noise reduction, artifacts suppression, and edge detail preservation. Compared to that obtained by the TGV based method without prior image, the relative root mean square error in the images reconstructed by the proposed method is reduced by over 20%.

Conclusion:

The authors propose an iterative reconstruction via prior image constrained total generalize variation for spectral CT. Also, we have developed an alternating optimization algorithm and numerically demonstrated the merits of our approach. Results show that the proposed PICTGV method outperforms the TGV method for spectral CT.
WE‐FG‐207B‐08: Dual‐Energy CT Iodine Accuracy Across Vendors and Platforms
Authors: Jacobsen M , Wood C , Cody D
Published: July 2016

Purpose:

Although a major benefit of dual‐energy CT is its quantitative capabilities, it is critical to understand how results vary by scanner manufacturer and/or model before making clinical patient management decisions. Each manufacturer utilizes a specific dual‐energy CT approach; cross‐calibration may be required for facilities with more than one dual‐energy CT scanner type.

Methods:

A solid dual‐energy quality control phantom (Gammex, Inc.; Appleton, WI) representing a large body cross‐section containing three Iodine inserts (2mg/ml, 5mg/ml, 15 mg/ml) was scanned on these CT systems: GE HD‐750 (80/140kVp), prototype GE Revolution CT with GSI (80/140kVp), Siemens Flash (80/140kVp and 100/140kVp), and Philips IQon (120kVp and 140kVp). Iodine content was measured in units of concentration (mg/ml) from a single 5mm‐thick central image. Three to five acquisitions were performed on each scanner platform in order to compute standard deviation. Scan acquisitions were approximately dose‐matched (∼25mGy CTDIvol) and image parameters were as consistent as possible (thickness, kernel, no noise reduction applied).

Results:

Iodine measurement error ranges were −0.24ߝ0.16 mg/ml for the 2mg/ml insert (−12.0 − 8.0%), −0.28–0.26 mg/ml for the 5mg/ml insert (−5.6 − 5.2%), and −1.16−0.99 mg/ml for the 15mg/ml insert (−7.7 − 6.6%). Standard deviations ranged from 0 to 0.19 mg/ml for the repeated acquisitions from each scanner. The average iodine measurement error and standard deviation across all systems and inserts was −0.21 ± 0.48 mg/ml (−1.5 ± 6.48%). The largest absolute measurement error was found in the 15mg/ml iodine insert.

Conclusion:

There was generally good agreement in Iodine quantification across 3 dual‐energy CT manufacturers and 4 scanner models. This was unexpected given the widely different underlying dual‐energy CT mechanisms employed. Future work will include additional scanner platforms, independent verification of the Iodine insert standard concentrations (especially the 15 mg/ml insert), and how much measurement variability can be clinically tolerated.

This research has been supported by funds from Dr. William Murphy, Jr., the John S. Dunn, Sr. Distinguished Chair in Diagnostic Imaging at MD Anderson Cancer Center.
WE‐G‐204‐00: Post‐Graduate Training of the Next Generation of Academic Medical Physicists
Authors: Hazle John
Published: July 2016

While many indicators for academic medical physics are distressing – jobs are tight, demands on clinical time are high (and getting worse) and national funding has been flat for several years (meaning less money in reality) the present is perhaps one of the most exciting times in cancer research history, and medical physicists have an opportunity to make a difference.

Many of us predict the impact of medical physics on cancer research over the next decade to be more significant than ever. Why is that? First, medical imaging is used for every cancer patient in developed countries. Every improvement in the acquisition, processing or analysis of radiological images has the potential to impact patients. The use of radiation therapy is at an all‐time high – and virtually cannot be performed without medical physics. Many of the advances in both biomedical imaging and radiation oncology are the result of the hard work of academic medical physicists who are thinking of the next generation of technologies that will be used against cancer or an even broader spectrum of diseases.

A career in academic medical physics is demanding, particularly for those with clinical responsibilities. As the demands for justification of their clinical effort become increasingly metricized, the ability to do “unfunded research” will become even more difficult. This means that many will have to generate external salary support to justify their efforts in research and development. This comes at a time when funding for research is compressed and harder to obtain. Generally speaking, if you are not contributing 50% or more of your effort to research, you are competing at a disadvantage and it is very unlikely you will get an NIH/NCI/NIBIB grant.

Furthermore, in the ongoing effort to improve patient care and safety, we have developed credentialing pathways that now require at least two‐years of residency training. This full‐time clinical training creates a gap in the research trajectory of graduate students who aspire to academic positions with an expectation for extramural funding. To address this, several residency programs have created hybrid programs where the two‐years of clinical training is combined with one or two years of research effort to allow candidates to further establish an academic identity and to ensure adequate academic productivity to compete for a beginning faculty position.

In conclusion, while the path to a successful career in academic medical physics is steep and sometimes hard to follow, reaching the apex is worth the journey. Different paths to a career in medical physics are available, you just have to decide which one is right for you. If improving cancer care is your goal as a physicist, then academic medical physics is the job for you!
WE‐H‐BRC‐01: Failure Mode and Effects Analysis of Skin Electronic Brachytherapy Using Esteya Unit
Authors: Ibanez‐Rosello B , Bautista‐Ballesteros J , Bonaque J , Lliso F , Carmona V , Gimeno J , Ouhib Z , Perez‐Calatayud J
Published: July 2016

Purpose:

A failure mode and effect analysis (FMEA) of skin lesions treatment process using Esteya™ device (Elekta Brachyterapy, Veenendaal, The Netherlands) was performed, with the aim of increasing the quality of the treatment and reducing the likelihood of unwanted events.

Methods:

A multidisciplinary team with experience in the treatment process met to establish the process map, which outlines the flow of various stages for such patients undergoing skin treatment. Potential failure modes (FM) were identified and the value of severity (S), frequency of occurrence (O), and lack of detectability (D) of the proposed FM were scored individually, each on a scale of 1 to 10 following TG‐100 guidelines of the AAPM. These failure modes were ranked according to our risk priority number (RPN) and S scores. The efficiency of existing quality management tools was analyzed through a reassessment of the O and D made by consensus.

Results:

149 FM were identified, 43 of which had RPN ≥ 100 and 30 had S ≥ 7. After introduction of the tools of quality management, only 3 FM had RPN ≥ 100 and 22 FM had RPN ≥ 50. These 22 FM were thoroughly analyzed and new tools for quality management were proposed. The most common cause of highest RPN FM was associated with the heavy patient workload and the continuous and accurate applicator‐patient skin contact during the treatment. To overcome this second item, a regular quality control and setup review by a second individual before each treatment session was proposed.

Conclusion:

FMEA revealed some of the FM potentials that were not predicted during the initial implementation of the quality management tools. This exercise was useful in identifying the need of periodic update of the FMEA process as new potential failures can be identified.
WE‐H‐BRC‐02: Failure Mode and Effect Analysis of Liver Stereotactic Body Radiotherapy
Authors: Rusu I , Thomas T , Roeske J , Price J , Perino C , Mescioglu I , Surucu M
Published: July 2016

Purpose:

To identify areas of improvement in our liver stereotactic body radiation therapy (SBRT) program, using failure mode and effect analysis (FMEA).

Methods:

A multidisciplinary group consisting of one physician, three physicists, one dosimetrist and two therapists was formed. A process map covering 10 major stages of the liver SBRT program from the initial diagnosis to post treatment follow‐up was generated. A total of 102 failure modes, together with their causes and effects, were identified. The occurrence (O), severity (S) and lack of detectability (D) were independently scored. The ranking was done using the risk probability number (RPN) defined as the product of average O, S and D numbers for each mode. The scores were normalized to remove inter‐observer variability, while preserving individual ranking order. Further, a correlation analysis on the overall agreement on rank order of all failure modes resulted in positive values for successive pairs of evaluators. The failure modes with the highest RPN value were considered for further investigation.

Results:

The average normalized RPN values for all modes were 39 with a range of 9 to 103. The FMEA analysis resulted in the identification of the top 10 critical failures modes as: Incorrect CT‐MR registration, MR scan not performed in treatment position, patient movement between CBCT acquisition and treatment, daily IGRT QA not verified, incorrect or incomplete ITV delineation, OAR contours not verified, inaccurate normal liver effective dose (Veff) calculation, failure of bolus tracking for 4D CT scan, setup instructions not followed for treatment and plan evaluation metrics missed.

Conclusion:

The application of FMEA to our liver SBRT program led to the identification and possible improvement of areas affecting patient safety.
WE‐H‐BRC‐04: Implement Lean Methodology to Make Our Current Process of CT Simulation to Treatment More Efficient
Authors: Boddu S , Morrow A , Krishnamurthy N , McVicker A , Deb N , Rangaraj D
Published: July 2016

Purpose:

Our goal is to implement lean methodology to make our current process of CT simulation to treatment more efficient.

Methods:

In this study, we implemented lean methodology and tools and employed flowchart in excel for process‐mapping. We formed a group of physicians, physicists, dosimetrists, therapists and a clinical physics assistant and huddled bi‐weekly to map current value streams. We performed GEMBA walks and observed current processes from scheduling patient CT Simulations to treatment plan approval. From this, the entire workflow was categorized into processes, sub‐processes, and tasks. For each process we gathered data on touch time, first time quality, undesirable effects (UDEs), and wait‐times from relevant members of each task. UDEs were binned per frequency of their occurrence. We huddled to map future state and to find solutions to high frequency UDEs. We implemented visual controls, hard stops, and documented issues found during chart checks prior to treatment plan approval.

Results:

We have identified approximately 64 UDEs in our current workflow that could cause delays, re‐work, compromise the quality and safety of patient treatments, or cause wait times between 1 – 6 days. While some UDEs are unavoidable, such as re‐planning due to patient weight loss, eliminating avoidable UDEs is our goal. In 2015, we found 399 issues with patient treatment plans, of which 261, 95 and 43 were low, medium and high severity, respectively. We also mapped patient‐specific QA processes for IMRT/Rapid Arc and SRS/SBRT, involving 10 and 18 steps, respectively. From these, 13 UDEs were found and 5 were addressed that solved 20% of issues.

Conclusion:

We have successfully implemented lean methodology and tools. We are further mapping treatment site specific workflows to identify bottlenecks, potential breakdowns and personnel allocation and employ tools like failure mode effects analysis to mitigate risk factors to make this process efficient.