bluuebunny/crossref_metadata_2025 huggingface dataset:
TU‐EF‐303‐03: Single Cell Measurements of Tanscription Heterogeneity of Highly Mobile Identical Genes
Authors: Gratton E.
Published: June 2015

Many medical physics diagnostic and therapeutic developments have significant overlap with biophysical approaches to measuring and modeling molecular and cellular systems. Although these methods may differ dramatically in terms of temporal and spatial scales, many of the underlying concepts are identical, suggesting potential synergies across the scales. For example, while clinical imaging is typically in the (sub)millimeter and second regime, biophysical imaging technologies reach sub‐nanometer and sub‐picosecond scales. Despite these scale differences, the use of molecular labeling, resulting large datasets, and need for quantitative analysis methods are similar, and solutions developed for one application are easily translated to others. Similarly, mathematical models used to understand clinical responses are often based on molecular and cellular networks that have been elucidated by biophysical studies. In turn, such models are directly useful for guiding on‐going biophysical and biomedical research. Relevant biophysical applications are found in the cancer, neuroscience, and cardiac fields, which are also research focus areas for many AAPM members. Presentations by physicists working in biophysics will explore potential synergies with diagnostic and therapeutic medical physics, as well as help identify areas of common interest that would be ripe for novel collaborations.

Learning Objectives:

1.To learn about differences in temporal and spatial scales of medical physics and biophysics

To learn about common methods used in medical physics and biophysics

To learn about synergistic opportunities between medical physics and biophysics
TU‐EF‐204‐01: Accurate Prediction of CT Tube Current Modulation: Estimating Tube Current Modulation Schemes for Voxelized Patient Models Used in Monte Carlo Simulations
Authors: McMillan K , Bostani M , McCollough C , McNitt‐Gray M
Published: June 2015

Purpose:

Most patient models used in Monte Carlo‐based estimates of CT dose, including computational phantoms, do not have tube current modulation (TCM) data associated with them. While not a problem for fixed tube current simulations, this is a limitation when modeling the effects of TCM. Therefore, the purpose of this work was to develop and validate methods to estimate TCM schemes for any voxelized patient model.

Methods:

For 10 patients who received clinically‐indicated chest (n=5) and abdomen/pelvis (n=5) scans on a Siemens CT scanner, both CT localizer radiograph (“topogram”) and image data were collected. Methods were devised to estimate the complete x‐y‐z TCM scheme using patient attenuation data: (a) available in the Siemens CT localizer radiograph/topogram itself (“actual‐topo”) and (b) from a simulated topogram (“sim‐topo”) derived from a projection of the image data. For comparison, the actual TCM scheme was extracted from the projection data of each patient. For validation, Monte Carlo simulations were performed using each TCM scheme to estimate dose to the lungs (chest scans) and liver (abdomen/pelvis scans). Organ doses from simulations using the actual TCM were compared to those using each of the estimated TCM methods (“actual‐topo” and “sim‐topo”).

Results:

For chest scans, the average differences between doses estimated using actual TCM schemes and estimated TCM schemes (“actual‐topo” and “sim‐topo”) were 3.70% and 4.98%, respectively. For abdomen/pelvis scans, the average differences were 5.55% and 6.97%, respectively.

Conclusion:

Strong agreement between doses estimated using actual and estimated TCM schemes validates the methods for simulating Siemens topograms and converting attenuation data into TCM schemes. This indicates that the methods developed in this work can be used to accurately estimate TCM schemes for any patient model or computational phantom, whether a CT localizer radiograph is available or not.

Funding Support: NIH Grant R01‐EB017095; Disclosures ‐ Michael McNitt‐Gray: Institutional Research Agreement, Siemens AG; Research Support, Siemens AG; Consultant, Flaherty Sensabaugh Bonasso PLLC; Consultant, Fulbright and Jaworski; Disclosures ‐ Cynthia McCollough: Research Grant, Siemens Healthcare
TU‐EF‐204‐09: A Preliminary Method of Risk‐Informed Optimization of Tube Current Modulation for Dose Reduction in CT
Authors: Gao Y , Liu T , Li X , Liu B , Kalra M , Caracappa P , Xu X
Published: June 2015

Purpose:

X‐rays from CT scans can increase cancer risk to patients. Lifetime Attributable Risk of Cancer Incidence for adult patients has been investigated and shown to decrease as patient age. However, a new risk model shows an increasing risk trend for several radiosensitive organs for middle age patients. This study investigates the feasibility of a general method for optimizing tube current modulation (TCM) functions to minimize risk by reducing radiation dose to radiosensitive organs of patients.

Methods:

Organ‐based TCM has been investigated in literature for eye lens dose and breast dose. Adopting the concept in organ‐based TCM, this study seeks to find an optimized tube current for minimal total risk to breasts and lungs by reducing dose to these organs. The contributions of each CT view to organ dose are determined through simulations of CT scan view‐by‐view using a GPU‐based fast Monte Carlo code, ARCHER. A Linear Programming problem is established for tube current optimization, with Monte Carlo results as weighting factors at each view. A pre‐determined dose is used as upper dose boundary, and tube current of each view is optimized to minimize the total risk.

Results:

An optimized tube current is found to minimize the total risk of lungs and breasts: compared to fixed current, the risk is reduced by 13%, with breast dose reduced by 38% and lung dose reduced by 7%. The average tube current is maintained during optimization to maintain image quality. In addition, dose to other organs in chest region is slightly affected, with relative change in dose smaller than 10%.

Conclusion:

Optimized tube current plans can be generated to minimize cancer risk to lungs and breasts while maintaining image quality. In the future, various risk models and greater number of projections per rotation will be simulated on phantoms of different gender and age.

National Institutes of Health R01EB015478
TU‐EF‐210‐03: Real‐Time Ablation Monitoring and Lesion Quantification Using Harmonic Motion Imaging
Authors: Konofagou E.
Published: June 2015

The use of therapeutic ultrasound to provide targeted therapy is an active research area that has a broad application scope. The invited talks in this session will address currently implemented strategies and protocols for both hyperthermia and ablation applications using therapeutic ultrasound. The role of both ultrasound and MRI in the monitoring and assessment of these therapies will be explored in both pre‐clinical and clinical applications.

Katherine Ferrara: High Intensity Focused Ultrasound, Drug Delivery, and Immunotherapy

Rajiv Chopra: Translating Localized Doxorubicin Delivery to Pediatric Oncology using MRI‐guided HIFU

Elisa Konofagou: Real‐time Ablation Monitoring and Lesion Quantification using Harmonic Motion Imaging

Keyvan Farahani: AAPM Task Groups in Interventional Ultrasound Imaging and Therapy

Learning Objectives:

Understand the role of ultrasound in localized drug delivery and the effects of immunotherapy when used in conjunction with ultrasound therapy.

Understand potential targeted drug delivery clinical applications including pediatric oncology.

Understand the technical requirements for performing targeted drug delivery.

Understand how radiation‐force approaches can be used to both monitor and assess high intensity focused ultrasound ablation therapy.

Understand the role of AAPM task groups in ultrasound imaging and therapies.

Chopra: Funding from Cancer Prevention and Research Initiative of Texas (CPRIT), Award R1308 Evelyn and M.R. Hudson Foundation; Research Support from Research Contract with Philips Healthcare; COI are Co‐founder of FUS Instruments Inc

Ferrara: Supported by NIH, UCDavis and California (CIRM and BHCE)

Farahani: In‐kind research support from Philips Healthcare
TU‐G‐304‐01: Things You Wonâ€™t Be Able to Say Someone Should Have Told You
Authors: Sherouse G.
Published: June 2015

As a new member of AAPM, it's easy to feel overwhelmed by the size and complexity of the association and to be unaware of the benefits and opportunities available to members. At this year's AAPM Annual Meeting in Anaheim, we will host a New Member Symposium where you can learn more about the organization, member resources, opportunities to get involved, and about topics of particular interest to new professionals. We encourage you to take advantage of this great opportunity to learn valuable information and to grow your professional network.

Following an introduction from Dr. John Boone, AAPM President; Justin Keener, Chair of the New Professional Subcommittee, will speak on, “Physics of the AAPM.” Next will be Dr. George Sherouse sharing invaluable information in his talk, “Things You Won't Be Able to Say Somebody Should've Told You.”

Registered attendees will receive a raffle ticket. Enter to win a complimentary registration for the 2016 Annual Meeting in Washington, DC!

In addition, all new members who register for the Symposium will receive a drink ticket, good for one complimentary soda or beer served after the New Member Symposium during the social with Committee Chairs from 4 AAPM Councils: Science, Education, Professional and Administrative.

Get your picture taken!!! There will be a photographer there to take pictures for your profile in the AAPM directory.

The New Member Symposium is a (free) ticket option when you register online for the Annual Meeting. We hope that you will plan to attend.
TU‐G‐BRD‐02: Automated Systematic Quality Assurance Program for Radiation Oncology Information System Upgrades
Authors: Zhang B , Yi B , Eley J , Mutaf Y , Rahman S , D'souza W
Published: June 2015

Purpose:

To: (1) describe an independent, automated, systematic software‐based protocol for verifying clinical data accuracy/integrity for mitigation of data corruption/loss risks following radiation oncology information system (ROIS) upgrades; and (2) report on application of this approach in an academic/community practice environment.

Methods:

We propose a robust approach to perform quality assurance on the ROIS after an upgrade, targeting four data sources: (1) ROIS relational database; (2) ROIS DICOM interface; (3) ROIS treatment machine data configuration; and (4) ROIS‐generated clinical reports. We investigated the database schema for differences between pre‐/post‐upgrade states. Paired DICOM data streams for the same object (such as RT‐Plan/Treatment Record) were compared between pre‐/post‐upgrade states for data corruption. We examined machine configuration and related commissioning data files for changes and corruption. ROIS‐generated treatment appointment and treatment parameter reports were compared to ensure patient encounter and treatment plan accuracy. This protocol was supplemented by an end‐to‐end clinical workflow test to verify essential ROI functionality and integrity of components interfaced during patient care chain of activities. We describe the implementation of this protocol during a Varian ARIA system upgrade at our clinic.

Results:

We verified 1,638 data tables with 2.4 billion data records. For 222 under‐treatment patients, 605 DICOM RT plans and 13,480 DICOM treatment records retrieved from the ROIS DICOM interface were compared, with no differences in fractions, doses delivered, or treatment parameters. We identified 82 new data tables and 78 amended/deleted tables consistent with the upgrade. Reports for 5,073 patient encounters over a 2‐week horizon were compared and were identical to those before the upgrade. Content in 12,237 xml machine files was compared, with no differences identified.

Conclusion:

An independent QA/validation approach for ROIS upgrades was developed and implemented at our clinic. The success of this approach ensures a robust QA of ROIS upgrades without manual paper/electronic checks and associated intensive labor.
TU‐G‐BRA‐03: Predicting Radiation Therapy Induced Ventilation Changes Using 4DCT Jacobian Calculations
Authors: Patton T , Du K , Christensen G , Reinhardt J , Bayouth J
Published: June 2015

Purpose:

Longitudinal changes in lung ventilation following radiation therapy can be mapped using four‐dimensional computed tomography(4DCT) and image registration. This study aimed to predict ventilation changes caused by radiation therapy(RT) as a function of pre‐RT ventilation and delivered dose.

Methods:

4DCT images were acquired before and 3 months after radiation therapy for 13 subjects. Jacobian ventilation maps were calculated from the 4DCT images, warped to a common coordinate system, and a Jacobian ratio map was computed voxel‐by‐voxel as the ratio of post‐RT to pre‐RT Jacobian calculations. A leave‐one‐out method was used to build a response model for each subject: post‐RT to pre‐RT Jacobian ratio data and dose distributions of 12 subjects were applied to the subject's pre‐RT Jacobian map to predict the post‐RT Jacobian. The predicted Jacobian map was compared to the actual post‐RT Jacobian map to evaluate efficacy. Within this cohort, 8 subjects had repeat pre‐RT scans that were compared as a reference for no ventilation change. Maps were compared using gamma pass rate criteria of 2mm distance‐to‐agreement and 6% ventilation difference. Gamma pass rates were compared using paired t‐tests to determine significant differences. Further analysis masked non‐radiation induced changes by excluding voxels below specified dose thresholds.

Results:

Visual inspection demonstrates the predicted post‐RT ventilation map is similar to the actual map in magnitude and distribution. Quantitatively, the percentage of voxels in agreement when excluding voxels receiving below specified doses are: 74%/20Gy, 73%/10Gy, 73%/5Gy, and 71%/0Gy. By comparison, repeat scans produced 73% of voxels within the 6%/2mm criteria. The agreement of the actual post‐RT maps with the predicted maps was significantly better than agreement with pre‐RT maps (p<0.02).

Conclusion:

This work validates that significant changes to ventilation post‐RT can be predicted. The differences between the predicted and actual outcome are similar to differences between repeat scans with equivalent ventilation.

This work was supported by NIH grant CA166703 and a Pilot Grant from University of Iowa Carver College of Medicine
TU‐G‐303‐00: Radiomics: Advances in the Use of Quantitative Imaging Used for Predictive Modeling
Authors: Deasy Joseph
Published: June 2015

‘Radiomics’ refers to studies that extract a large amount of quantitative information from medical imaging studies as a basis for characterizing a specific aspect of patient health. Radiomics models can be built to address a wide range of outcome predictions, clinical decisions, basic cancer biology, etc. For example, radiomics models can be built to predict the aggressiveness of an imaged cancer, cancer gene expression characteristics (radiogenomics), radiation therapy treatment response, etc. Technically, radiomics brings together quantitative imaging, computer vision/image processing, and machine learning. In this symposium, speakers will discuss approaches to radiomics investigations, including: longitudinal radiomics, radiomics combined with other biomarkers (‘pan‐omics’), radiomics for various imaging modalities (CT, MRI, and PET), and the use of registered multi‐modality imaging datasets as a basis for radiomics. There are many challenges to the eventual use of radiomics‐derived methods in clinical practice, including: standardization and robustness of selected metrics, accruing the data required, building and validating the resulting models, registering longitudinal data that often involve significant patient changes, reliable automated cancer segmentation tools, etc. Despite the hurdles, results achieved so far indicate the tremendous potential of this general approach to quantifying and using data from medical images. Specific applications of radiomics to be presented in this symposium will include: the longitudinal analysis of patients with low‐grade gliomas; automatic detection and assessment of patients with metastatic bone lesions; image‐based monitoring of patients with growing lymph nodes; predicting radiotherapy outcomes using multi‐modality radiomics; and studies relating radiomics with genomics in lung cancer and glioblastoma.

Learning Objectives:

Understanding the basic image features that are often used in radiomic models.

Understanding requirements for reliable radiomic models, including robustness of metrics, adequate predictive accuracy, and generalizability.

Understanding the methodology behind radiomic‐genomic (‘radiogenomics’) correlations.

Research supported by NIH (US), CIHR (Canada), and NSERC (Canada)
TU‐G‐204‐01: BEST IN PHYSICS (IMAGING): Dynamic CT Myocardial Perfusion Measurement and Its Comparison to Fractional Flow Reserve
Authors: Ziemer B , Hubbard L , Groves E , Sadeghi B , Javan H , Lipinski J , Molloi S
Published: June 2015

Purpose:

To evaluate a first pass analysis (FPA) technique for CT perfusion measurement in a swine animal and its validation using fractional flow reserve (FFR) as a reference standard.

Methods:

Swine were placed under anesthesia and relevant physiologic parameters were continuously recorded. Intra‐coronary adenosine was administered to induce maximum hyperemia. A pressure wire was advanced distal to the first diagonal branch of the left anterior descending (LAD) artery for FFR measurements and a balloon dilation catheter was inserted over the pressure wire into the proximal LAD to create varying levels of stenosis. Images were acquired with a 320‐row wide volume CT scanner. Three main coronary perfusion beds were delineated in the myocardium using arteries extracted from CT angiography images using a minimum energy hypothesis. The integrated density in the perfusion bed was used to calculate perfusion using the FPA technique. The perfusion in the LAD bed over a range of stenosis severity was measured. The measured fractional perfusion was compared to FFR and linear regression was performed.

Results:

The measured fractional perfusion using the FPA technique (P_FPA) and FFR were related as P_FPA = 1.06FFR – 0.06 (r2 = 0.86). The perfusion measurements were calculated with only three to five total CT volume scans, which drastically reduces the radiation dose as compared with the existing techniques requiring 15–20 volume scans.

Conclusion:

The measured perfusion using the first pass analysis technique showed good correlation with FFR measurements as a reference standard. The technique for perfusion measurement can potentially make a substantial reduction in radiation dose as compared with the existing techniques.
TU‐G‐204‐02: Automatic Sclerotic Bone Metastases Detection in the Pelvic Region From Dual Energy CT
Authors: Fehr D , Schmidtlein C , Hwang S , Deasy J , Veeraraghavan H
Published: June 2015

Purpose:

To automatically detect sclerotic bone metastases in the pelvic region using dual energy computed tomography (DECT).

Methods:

We developed a two stage algorithm to automatically detect sclerotic bone metastases in the pelvis from DECT for patients with multiple bone metastatic lesions and with hip implants. The first stage consists of extracting the bone and marrow regions by using a support vector machine (SVM) classifier. We employed a novel representation of the DECT images using multi‐material decomposition, which represents each voxel as a mixture of different physical materials (e.g. bone+water+fat). Following the extraction of bone and marrow, in the second stage, a bi ‐histogram equalization method was employed to enhance the contrast to reveal the bone metastases. Next, meanshift segmentation was performed to separate the voxels by their intensity levels. Finally, shape‐based filtering was performed to extract the possible locations of the metastatic lesions using multiple shape criteria. We used the following shape parameters: area, eccentricity, major and minor axis, perimeter and skeleton.

Results:

A radiologist with several years of experience with DECT manually labeled 64 regions consisting of metastatic lesions from 10 different patients. However, the patients had many more metastasic lesions throughout the pelvis. Our method correctly identified 46 of the marked 64 regions (72%). In addition, our method also identified several other lesions, which can then be validated by the radiologist. The missed lesions were typically very large elongated regions consisting of several islands of very small (<4mm) lesions.

Conclusion:

We developed an algorithm to automatically detect sclerotic lesions in the pelvic region from DECT. Preliminary assessment shows that our algorithm generated lesions agreeing with the radiologist generated candidate regions. Furthermore, our method reveals additional lesions that can be inspected by the radiologist, thereby, reducing radiologist effort in identifying all the lesions with poor contrast from the DECT images.
TU‐G‐204‐07: A Research Pipeline to Simulate a Wide Range of CT Image Acquisition and Reconstruction Parameters and Assess the Performance of Quantitative Imaging and CAD Systems
Authors: Young S , Lo P , Kim G , Hoffman J , Brown M , McNitt‐Gray M
Published: June 2015

Purpose:

Quantitative Imaging and CAD tasks performed with CT (e.g. lung nodule detection, assessment of tumor size, etc.) may be sensitive to image acquisition and reconstruction parameters such as dose level, image thickness and reconstruction method (FBP, iterative, etc.). The purpose of this work was to develop a research pipeline for generating CT image series that represent a wide variety of acquisition and reconstruction conditions under which CAD and Quantitative Imaging performance would be evaluated.

Methods:

With IRB approval, we have collected the raw CT data from hundreds of patients. These raw sinogram files serve as the input to the research pipeline. To simulate a wide range of dose levels, we developed software which adds noise to the sinogram. Multiple reduced‐dose sinograms can be generated for a single patient, and those reduced‐dose sinograms are then fed either to the scanner's reconstruction engine or to our in‐house reconstruction engine; each has conventional filtered back projection (FBP) and iterative reconstruction methods. After generating image series across a range of dose levels and reconstruction methods, we can evaluate the performance of various quantitative imaging or CAD tools in tasks such as automated and semi‐automated lesion segmentation, assessment of lesion size, and measurement of density or texture.

Results:

We have successfully applied this pipeline across a range of clinical CT applications, including: (1) chest oncology, where the pipeline was used to quantify the effects of dose and reconstruction method on nodule volumetry, and (2) lung cancer screening, where the pipeline is being used to measure the robustness of an automated CAD algorithm with respect to dose.

Conclusion:

The acquisition/reconstruction pipeline shows promise for investigating and quantifying the effects of dose and reconstruction method on various clinical CT applications.

NCI grant U01 CA181156 (Quantitative Imaging Network); Tobacco Related Disease Research Project grant 22RT‐0131.
TU‐G‐204‐08: Investigation of Volume Adjustment Techniques in Low Dose CT Lung Densitometry
Authors: Chen‐Mayer H , Fain S , Judy P
Published: June 2015

Purpose:

Low dose CT for lung densitometry has shown utility in evaluating severity and progression of pulmonary emphysema in patients with chronic obstructive pulmonary disease (COPD). Effort is underway at QIBA to standardize measurement protocols based on published longitudinal studies on non‐diseased subjects. The purpose of this report is to assess an important component of the densitometry CT data interpretation: the volume adjustment necessary to reduce the effect of respiration on density.

Methods:

The 15 percentile density scores (Perc 15), defined as a threshold HU containing 15% lowest density in the attenuation histogram of the whole lung, were compiled for 30 subjects obtained from the National Lung Cancer Trial database with baseline and repeat scans one year apart. A model assuming an adapted sponge model, where the relationship between volume (V) and density (rho) is given by m=rhoV^s (Staring et al, Med. Phys. 41, 021905 (2014)). s can be obtained for each subject, and for the entire sample, which allowed adjustment of the Perc15 value at the repeat scan both at the sample level and for each subject.

Results:

The average bias (change between scan 2 and 1) and standard deviation (SD) of the bias for a) unadjusted, b) sample‐level adjusted, and c) subject‐level adjusted Perc 15 (HU) values are 2.0 (13.7), 1.5 (3.6), and 2.4 (9.8), respectively, suggesting that the method of volume adjustment affects the assessment of the accuracy and precision of the measurement. Method b) improves both more than c). The distribution of the value s indicates that less than 1/5 of the subjects followed the sponge‐like behavior (unity s).

Conclusion:

Volume adjustment has a major impact on the assessment of accuracy and precision of quantitative lung density CT, and therefore the interpretation directly influence the decision making in a clinical setting.

Sean Fain receives grant funding from GE Healthcare.
TU‐G‐207‐03: High Spatial Resolution and High Sensitivity X‐Ray Fluorescence Imaging
Authors: Xing L.
Published: June 2015

Last few years has witnessed the development of novel of X‐ray imaging modalities, such as spectral CT, phase contrast CT, and X‐ray acoustic/fluorescence/luminescence imaging. This symposium will present the recent advances of these emerging X‐ray imaging modalities and update the attendees with knowledge in various related topics, including X‐ray photon‐counting detectors, X‐ray physics underlying the emerging applications beyond the traditional X‐ray imaging, image reconstruction for the novel modalities, characterization and evaluation of the systems, and their practical implications. In addition, the concept and practical aspects of X‐ray activatable targeted nanoparticles for molecular X‐ray imaging will be discussed in the context of X‐ray fluorescence and luminescence CT.

Learning Objectives:

Present background knowledge of various emerging X‐ray imaging techniques, such as spectral CT, phase contrast CT and X‐ray fluorescence/luminescence CT.

Discuss the practical need, technical aspects and current status of the emerging X‐ray imaging modalities.

Describe utility and future impact of the new generation of X‐ray imaging applications.
TU‐G‐201‐01: What Therapy Physicists Need to Know About CT and PET/CT: Terminology and Latest Developments
Authors: Hua C.
Published: June 2015

This session will update therapeutic physicists on technological advancements and radiation oncology features of commercial CT, MRI, and PET/CT imaging systems. Also described are physicists’ roles in every stage of equipment selection, purchasing, and operation, including defining specifications, evaluating vendors, making recommendations, and optimal and safe use of imaging equipment in radiation oncology environment.

The first presentation defines important terminology of CT and PET/CT followed by a review of latest innovations, such as metal artifact reduction, statistical iterative reconstruction, radiation dose management, tissue classification by dual energy CT and spectral CT, improvement in spatial resolution and sensitivity in PET, and potentials of PET/MR. We will also discuss important technical specifications and items in CT and PET/CT purchasing quotes and their impacts.

The second presentation will focus on key components in the request for proposal for a MRI simulator and how to evaluate vendor proposals. MRI safety issues in radiation Oncology, including MRI scanner Zones (4‐zone design), will be discussed. Basic MR terminologies, important functionalities, and advanced features, which are relevant to radiation therapy, will be discussed.

In the third presentation, justification of imaging systems for radiation oncology, considerations in room design and construction in a RO department, shared use with diagnostic radiology, staffing needs and training, clinical/research use cases and implementation, will be discussed. The emphasis will be on understanding and bridging the differences between diagnostic and radiation oncology installations, building consensus amongst stakeholders for purchase and use, and integrating imaging technologies into the radiation oncology environment.

Learning Objectives:

Learn the latest innovations of major imaging systems relevant to radiation therapy

Be able to describe important technical specifications of CT, MRI, and PET/CT

Understand the process of budget request, equipment justification, comparisons of technical specifications, site visits, vendor selection, and contract development
TU‐G‐210‐00: Treatment Planning Strategies, Modeling, Control
Authors: Christensen Douglas
Published: June 2015

Modeling can play a vital role in predicting, optimizing and analyzing the results of therapeutic ultrasound treatments. Simulating the propagating acoustic beam in various targeted regions of the body allows for the prediction of the resulting power deposition and temperature profiles. In this session we will apply various modeling approaches to breast, abdominal organ and brain treatments. Of particular interest is the effectiveness of procedures for correcting for phase aberrations caused by intervening irregular tissues, such as the skull in transcranial applications or inhomogeneous breast tissues. Also described are methods to compensate for motion in targeted abdominal organs such as the liver or kidney.

Douglas Christensen – Modeling for Breast and Brain HIFU Treatment Planning

Tobias Preusser – TRANS‐FUSIMO – An Integrative Approach to Model‐Based Treatment Planning of Liver FUS

Tobias Preusser – TRANS‐FUSIMO – An Integrative Approach to Model‐Based Treatment Planning of Liver FUS

Learning Objectives:

Understand the role of acoustic beam modeling for predicting the effectiveness of therapeutic ultrasound treatments.

Apply acoustic modeling to specific breast, liver, kidney and transcranial anatomies.

Determine how to obtain appropriate acoustic modeling parameters from clinical images.

Understand the separate role of absorption and scattering in energy delivery to tissues.

See how organ motion can be compensated for in ultrasound therapies.

Compare simulated data with clinical temperature measurements in transcranial applications.

Supported by NIH R01 HL172787 and R01 EB013433 (DC); EU Seventh Framework Programme (FP7/2007‐2013) under 270186 (FUSIMO) and 611889 (TRANS‐FUSIMO)(TP); and P01 CA159992, GE, FUSF and InSightec (UV).
TU‐G‐210‐01: Modeling for Breast and Brain HIFU Treatment Planning
Authors: Christensen D.
Published: June 2015

Modeling can play a vital role in predicting, optimizing and analyzing the results of therapeutic ultrasound treatments. Simulating the propagating acoustic beam in various targeted regions of the body allows for the prediction of the resulting power deposition and temperature profiles. In this session we will apply various modeling approaches to breast, abdominal organ and brain treatments. Of particular interest is the effectiveness of procedures for correcting for phase aberrations caused by intervening irregular tissues, such as the skull in transcranial applications or inhomogeneous breast tissues. Also described are methods to compensate for motion in targeted abdominal organs such as the liver or kidney.

Douglas Christensen – Modeling for Breast and Brain HIFU Treatment Planning

Tobias Preusser – TRANS‐FUSIMO – An Integrative Approach to Model‐Based Treatment Planning of Liver FUS

Tobias Preusser – TRANS‐FUSIMO – An Integrative Approach to Model‐Based Treatment Planning of Liver FUS

Learning Objectives:

Understand the role of acoustic beam modeling for predicting the effectiveness of therapeutic ultrasound treatments.

Apply acoustic modeling to specific breast, liver, kidney and transcranial anatomies.

Determine how to obtain appropriate acoustic modeling parameters from clinical images.

Understand the separate role of absorption and scattering in energy delivery to tissues.

See how organ motion can be compensated for in ultrasound therapies.

Compare simulated data with clinical temperature measurements in transcranial applications.

Supported by NIH R01 HL172787 and R01 EB013433 (DC); EU Seventh Framework Programme (FP7/2007‐2013) under 270186 (FUSIMO) and 611889 (TRANS‐FUSIMO)(TP); and P01 CA159992, GE, FUSF and InSightec (UV).
TU‐F‐CAMPUS‐T‐02: Risk Assessment of Scattered Neutrons for a Fetus From Proton Therapy of a Brain Tumor During Pregnancy
Authors: Geng C , Moteabbed M , Xu X , Paganetti H
Published: June 2015

Purpose:

To determine the scattered neutron dose and the resulting risk for a fetus from proton therapy for brain tumors during pregnancy.

Methods:

Using the Monte Carlo platform TOPAS, the ICRP reference parameters based anthropomorphic pregnancy phantoms for three stages (3‐, 6‐, 9‐month) were applied to evaluate the scattered neutron dose and dose equivalent. To calculate the dose equivalent, organ specific linear energy transfer (LET) based quality factor was used. Treatment plans from both passive scattering (PS) and pencil beam scanning (PBS) methods were considered in this study.

Results:

For pencil beam scanning, the neutron dose equivalent in the soft tissue of the fetus increases from 1.53x10−3 to 2.84x10−3 mSv per treatment Gy with increasing stage of gestation. This is due to scattered neutrons from the patient as the main contaminant source in PBS and a decrease in distance between the soft tissue of the fetus and GTV with increasing stage of gestation. For passive scattering, neutron dose equivalent to the soft tissue of the fetus shows a decrease from 0.17 to 0.13 mSv per treatment Gy in different stages, while the dose to the brain shows little difference around 0.18 mSv per treatment Gy because scattered neutrons from the treatment head contribute predominantly in passive scattering.

Conclusion:

The results show that the neutron dose to the fetus assuming a prescribed dose of 52.2 Gy is negligible for PBS, and is comparable to the scattered dose (0–10 mSv) from a head and neck CT scan for PS. It can be concluded that the dose to fetus is far lower than the thresholds of malformation, SMR and lethal death. The excess relative risk of childhood cancer induction would be increased by 0.48 and 0.103 using the Oxford Survey of Childhood Cancers and Japanese atomic model, respectively.

Changran Geng is supported by the Chinese Scholarship Council (CSC) and the National Natural Science Foundation of China (Grant No. 11475087).
TU‐F‐CAMPUS‐T‐03: Commissioning of a Custom Fetal Lead Shield for Radiotherapy
Authors: Owrangi A , Roberts D , Covington E , Hayman J , Masi K , Lee C , Moran J , Prisciandaro J
Published: June 2015

Purpose:

To evaluate the peripheral dose (PD) to a fetus during radiation therapy of pregnant patients when using a newly designed fetal lead shield (FLS).

Methods:

A custom FLS has been designed and fabricated for our department. The FLS (1.1 TVLs for 6 MV) is mounted on a mobile frame and can be adjusted vertically with a motor actuator. PD measurements were acquired for multiple simple square fields and for a variety of potential treatment sites a pregnant patient may be treated for including brain, head and neck (H&N) and thorax. For measurements of the brain, H&N, and thorax, an ionization chamber and OSLDs were positioned on average at a distance of 48, 29 and 26 cm, respectively, from the edge of treatment fields to mimic the approximate position of the fundus.

Results:

Based on our measurements, applying a 90° collimator rotation and using tertiary MLCs to define the field aperture in combination with jaws resulted in an average dose reduction of 60%. When using these planning strategies in combination with the FLS, on average, the PD was reduced by additional 25% for simple square fields and 20% for clinical plans.

Conclusion:

The custom FLS is a safe, effective, and relatively easy system to position. Commissioning measurements have demonstrated that the PD to the fetus can be significantly reduced when using the FLS. The comprehensive dataset obviates the need for individual patient pre‐treatment dose measurements as long as the geometry falls within the commissioning limits.
TU‐F‐CAMPUS‐I‐02: Contrast Enhanced Cone Beam CT Imaging with Dual‐ Gantry Image Acquisition and Constrained Iterative Reconstruction‐a Simulation Study for Liver Imaging Application
Authors: Zhong Y , Gupta S , Lai C , Wang T , Shaw C
Published: June 2015

Purpose:

Contrast time‐density curves may help differentiate malignant tumors from normal tissues or benign tumors. Repetitive scans using conventional CT or cone beam CT techniques, which Result in unacceptably high dose, may not achieve the desired temporal resolution. In this study we describe and demonstrate a 4D imaging technique for imaging and quantifying contrast flows requiring only one or two 360° scans.

Methods:

A dual‐gantry system is used to simultaneously acquire two projection images at orthogonal orientations. Following the scan, each or both of the two 360° projection sets are used to reconstruct an average contrast enhanced image set which is then segmented to form a 3D contrast map. Alternatively, a pre‐injection scan may be made and used to reconstruct a pre‐injection image set which is subtracted from the post‐injection image set to form the 3D contrast map. Each of the two 360° projection sets is divided into 12 subsets, thus creating 12 pairs of 30° limited angle projection sets, each corresponding to a time spanning over 1/12 of the scanning time. Each pair of the projection sets are reconstructed as a time specific 3D image set with the maximum likelihood estimation iterative algorithm using the contrast map as the constraint. As a demonstration, a 4D abdominal phantom was constructed from clinical CT images with blood flow through the normal tissue and a tumor modeled and imaging process simulated.

Results:

We have successfully generated a 4D image phantom, and calculated the projection images. The time density curves derived from the reconstructed image set matched well with the flow model used to generate the phantom.

Conclusion:

Dual‐gantry image acquisition and constrained iterative reconstruction algorithm may help to obtain time‐density curves of contrast agents in blood flows, which may help differentiate malignant tumors from normal tissues or benign tumors.
WE‐EF‐BRA‐04: Evaluation of Dosimetric Uncertainties in Individualized Targeted Radionuclide Therapy (TRT) Treatment Planning Using Pre‐Clinical Data
Authors: Besemer A , Grudzinski J , Titz B , Bednarz J B
Published: June 2015

Purpose:

Dosimetry for targeted radionuclide therapy (TRT) is moving away from conventional model‐based methods towards patient‐specific approaches. To address this need, a Monte Carlo (MC) dosimetry platform was developed to estimate patient‐specific therapeutic 3D dose distributions based on pre‐treatment imaging. However, because a standard practice for patient‐specific internal dosimetry has not yet been established, there are many sources of dosimetric uncertainties. The goal of this work was to quantify the sensitivity of various parameters on MC dose estimations.

Methods:

The ‘diapeutic’ agent, CLR1404, was used as a proof‐of‐principle compound in this work. CLR1404 can be radiolabeled with either 12⁴I for PET imaging or 131I for radiotherapy or SPECT imaging. PET/CT images of 5 mice were acquired out to 240 hrs post‐injection of 12⁴I‐CLR1404. The therapeutic 131I‐CLR1404 absorbed dose (AD) distribution was calculated using a Geant4‐based MC dosimetry platform. A series of sensitivity studies were performed. The variables that were investigated included the PET/CT voxel resolution, partial volume corrections (PVC), material segmentation, inter‐observer contouring variability, and the pre‐treatment image acquisition frequency.

Results:

Resampling the PET/CT voxel size between 0.2–0.8 mm resulted in up to a 13% variation in the mean AD. Application of the PVC increased the mean AD by 0.5–11.2%. Less than 1% differences in ROI mean AD were observed between the tissue segmentation schemes using 4 and 27 different material compositions. Inter‐observer contouring variability led to up to a 20% CoV (stdev/mean) in the mean AD between the users. Varying the number and frequency of pre‐treatment images used resulted in changes in mean AD up to 176% compared to the case using all 12 images.

Conclusion:

Voxel resolution, contour segmentation, the image acquisition protocol most significantly impacted patient‐specific TRT dosimetry. Further work is needed to develop a standard protocol that optimizes accuracy and efficiency for patient‐specific internal dosimetry.

BT and JG are affiliated with Cellectar Biosciences which owns the licensing rights to CLR1404 and related compounds.
WE‐EF‐BRA‐05: Experimental Design for High‐Throughput In‐Vitro RBE Measurements Using Protons, Helium and Carbon Ions
Authors: Guan F , Titt U , Patel D , Bronk L , Taleei R , Peeler C , Mirkovic D , Grosshans D , Jakel O , Mohan R
Published: June 2015

Purpose:

To design and validate experimental setups for investigation of dose and LET effects in cell kill for protons, helium and carbon ions, in high throughput and high accuracy cell experiments.

Methods:

Using the Geant4 Monte Carlo toolkit, we designed 3 custom range compensators to simultaneously expose cancer cells to different doses and LETs from selected portions of pristine ion beams from the entrance to points just beyond the Bragg peak. To minimize the spread of LET, we utilized mono‐energetic uniformly scanned beams at the HIT facility with support from the DKFZ. Using different entrance doses and LETs, a matrix of cell survival data was acquired leading to a specific RBE matrix. We utilized the standard clonogenic assay for H460 and H1437 lung‐cancer cell lines grown in 96‐well plates. Using these plates, the data could be acquired in a small number of exposures. The ion specific compensators were located in a horizontal beam, designed to hold two 96‐wells plates (12 columns by 8 rows) at an angle of 30o with respect to the beam direction.

Results:

Using about 20 hours of beam time, a total of about 11,000 wells containing cancer cells could be irradiated. The H460 and H1437 cell lines exhibited a significant dependence on LET when they were exposed to comparable doses. The results were similar for each of the investigated ion species, and indicate the need to incorporate RBE into the ion therapy planning process.

Conclusion:

The experimental design developed is a viable approach to rapidly acquire large amounts of accurate in‐vitro RBE data. We plan to further improve the design to achieve higher accuracy and throughput, thereby facilitating the irradiation of multiple cell types. The results are indicative of the possibility to develop a new degree of freedom (variable RBE) for future clinical ion therapy optimization.

Work supported by the Sister Institute Network Fund (SINF), University of Texas MD Anderson Cancer Center.
WE‐EF‐BRA‐06: Feasibility of Spatially Modulated Proton Beams for Small Animal Research
Authors: Lee E , Meyer J
Published: June 2015

Purpose:

To investigate the feasibility of proton minibeam radiotherapy (pMBRT) for small animal research. The motivation is to explore with protons the extraordinary normal tissue sparing effects to spatially modulated beams as observed on high flux synchrotron beam lines. We hypothesized that we can design a multi‐slit collimator for our proton beam line to produce planar‐parallel dose profiles with high modulation in the entrance region and homogenous dose coverage in the overlap of the Bragg peaks.

Methods:

The high dose rate 50 MeV research proton beamline at the University of Washington was modeled using the TOol for PArticle Simulation (TOPAS) Monte Carlo package. A brass collimator was implemented to generate proton minibeams. The collimator consists of an array of 2 cm long slits to cover an area of 2×2 cm2. The slit widths (0.1–1 mm), center‐to‐center (ctc) distances (1–3 mm) and collimator thickness (1–7 cm) were varied to evaluate the effect on dose rate, the peak‐to‐valley dose ratios (PVDR) and the change of penumbra and peak width (FWHM) with depth.

Results:

The Bragg peak was at a depth of ∼21 mm. The penumbra and FWHM remained relatively constant to a depth of about 10–15 mm. The PVDR ranged from 1.6 to 26 and the dose rate dropped exponentially with collimator thickness. A uniform dose can be achieved at depth with slightly compromised PVDRs and dose rate.

Conclusion:

The technical realization of pMBRT is feasible. The simulations have shown that it is possible to obtain uniform dose at depth while modulation is maintained on the entrance side. While the simulated beam widths are larger than on synchrotron generated microbeams the dosimetric advantage could avoid having to interlace two microbeams to achieve uniform dose in the target. The next steps are to build a collimator and verify the simulations experimentally.
WE‐EF‐BRA‐07: High Performance Preclinical Irradiation Through Optimized Dual Focal Spot Dose Painting and Online Virtual Isocenter Radiation Field Targeting
Authors: Stewart J , Lindsay P , Jaffray D
Published: June 2015

Purpose:

Advances in radiotherapy practice facilitated by collimation systems to shape radiation fields and image guidance to target these conformal beams have motivated proposals for more complex dose patterns to improve the therapeutic ratio. Recent progress in small animal radiotherapy platforms has provided the foundation to validate the efficacy of such interventions, but robustly delivering heterogeneous dose distributions at the scale and accuracy demanded by preclinical studies remains challenging. This work proposes a dual focal spot optimization method to paint spatially heterogeneous dose regions and an online virtual isocenter targeting method to accurately target the dose distributions.

Methods:

Two‐dimensional dose kernels were empirically measured for the 1 mm diameter circular collimator with radiochromic film in a solid water phantom for the small and large x‐ray focal spots on the X‐RAD 225Cx microirradiator. These kernels were used in an optimization framework which determined a set of animal stage positions, beam‐on times, and focal spot settings to optimally deliver a given desired dose distribution. An online method was developed which defined a virtual treatment isocenter based on a single image projection of the collimated radiation field. The method was demonstrated by optimization of a 6 mm circular 2 Gy target adjoining a 4 mm semicircular avoidance region.

Results:

The dual focal spot technique improved the optimized dose distribution with the proportion of avoidance region receiving more than 0.5 Gy reduced by 40% compared to the large focal spot technique. Targeting tests performed by irradiating ball bearing targets on radiochromic film pieced revealed the online targeting method improved the three‐dimensional accuracy from 0.48 mm to 0.15 mm.

Conclusion:

The dual focal spot optimization and online virtual isocenter targeting framework is a robust option for delivering dose at the preclinical level and provides a new experimental option for unique radiobiological investigations

This work is supported, in part, by the Natural Sciences and Engineering Research Council of Canada and a Mitacs‐Accelerate fellowship. P.E. Lindsay, and D.A. Jaffray are listed as inventors of the system described herein. This system has been licensed to Precision X‐Ray Inc. for commercial development.