Health and Medical Physics Commons^™

Developing Reference Plans For Evaluating Global Clinical Trials Credentialing And Psqa Systems, Fre'etta M D Brooks, Mohammad Hussein, Jessica Lye, Christopher L Nelson, Nakamura Mitsuhiro, Mallory C Glenn, Patricia Diez, Rushil Patel, Maddison Shaw, Ileana Silvestre Patallo, Miriam Barry, Catharine H Clark, Joerg Lehmann, Stephen F Kry

Faculty, Staff and Student Publications

Purpose: To develop a practical framework for creating a diverse set of validated reference plans (varying in complexity) and implement a workflow to introduce beam modeling, calibration, and delivery errors into the reference cohort to test and compare various dosimetry audit methodologies.

Methods: Sixteen IMRT and VMAT reference plans were created, using RayStation software, for four phantom geometries based on established credentialing cases from participating Global Harmonization Group (GHG) members. These reference plans were first validated in a multi-ion-chamber phantom. Nine dosimetric errors (perturbations) were introduced into the plans by modifying beam model and/or delivery parameters (MLC-offset, MLC-transmission, leaf-tip-width, PDD, …

Robust Automated Method Of Spatial Resolution Measurement In Radiotherapy Ct Simulation Images, Pavel Govyadinov, Rick R Layman, Tucker Netherton, Raymond Mumme, Aaron K Jones, Laurence E Court, Moiz Ahmad

Faculty, Staff and Student Publications

Background: Variation in imaging protocol, patient positioning, and the presence of artifacts can vary image quality in CT images used for radiotherapy planning. Automated methods for spatial resolution (SR) estimation exist but require further investigation and validation for wider adoption.

Purpose: To validated previously existing algorithm for SR estimation and introduce improvements that make it robust to patient positioning, CT protocol, site, and artifacts.

Method: A reference algorithm based on the previous gold standard was recreated and modified to improve robustness. The algorithms were tested on three different datasets: (1) a cylindrical ACR CT QC phantom scanned using a Siemens …

Clinical Use Of Gafchromic Ebt4 Film For In Vivo Dosimetry For Total Body Irradiation, Emily Draeger, Fada Guan, Min-Young Lee, Dae Yup Han, William Donahue, Zhe Jay Chen

Faculty, Staff and Student Publications

Purpose: In vivo dosimetry is a common requirement to validate dose accuracy/uniformity in total body irradiation (TBI). Several detectors can be used for in vivo dosimetry, including thermoluminescent dosimeters (TLDs), diodes, ion chambers, optically stimulated luminescent dosimeters (OSLDs), and film. TLDs are well established for use in vivo but required expertise and clinical system availability may make them impractical for multifractionated TBI. OSLDs offer quick readout, but recalls have restricted their use. The purpose of this work was to validate the newly available Gafchromic EBT4 film for TBI in vivo dosimetry.

Methods: Film calibration curves were created under standard conditions …

Imaging Lung Tumor Motion Using Integrated-Mode Proton Radiography-A Phantom Study Towards Tumor Tracking In Proton Radiotherapy, Ryan Fullarton, Mikaël Simard, Lennart Volz, Allison Toltz, Savanna Chung, Christoph Schuy, Daniel G Robertson, Gary Royle, Sam Beddar, Colin Baker, Christian Graeff, Charles-Antoine Collins-Fekete

Faculty, Staff and Student Publications

BACKGROUND: Motion of lung tumors during radiotherapy leads to decreased accuracy of the delivered dose distribution. This is especially true for proton radiotherapy due to the finite range of the proton beam. Methods for mitigating motion rely on knowing the position of the tumor during treatment.

PURPOSE: Proton radiography uses the treatment beam, at an energy high enough to traverse the patient, to produce a radiograph. This work shows the first results of using an integrated-mode proton radiography system to track the position of moving objects in an experimental phantom study; demonstrating the potential of using this method for measuring …

A Multiple X-Ray-Source Array (Mxa) System With A Planar Two-Dimensional Source Distribution For Digital Breast Tomosynthesis, Alejandro Sisniega, Andrew M Hernandez, Shadi A Shakeri, Elizabeth A Morris, John M Boone, Jeffrey H Siewerdsen, Paul R Schwoebel

Faculty, Staff and Student Publications

Background: Digital breast tomosynthesis (DBT) has outpaced digital mammography in clinical adoption in the United States; however, substantial technological limitations remain to image quality in DBT, including undersampling from a one-dimensional (1D) scan geometry, x-ray source motion during acquisition, and patient motion artifacts from long exam times.

Purpose: A thermionic cathode x-ray system employing two-dimensional (2D, planar) multiple x-ray-source arrays (MXA) is proposed to improve DBT image quality.

Methods: A 1D MXA, consisting of a linear array of thermionic cathodes was used to simulate a 2D MXA. The 1D MXA included 11 focal spots separated by a distance of Δd …

Optimized Scoring Of End-To-End Dosimetry Audits For Passive Motion Management – A Simulation Study Using The Iroc Thorax Phantom, Alex Burton, Mathieu Gaudreault, Nicholas Hardcastle, Jessica Lye, Sabeena Beveridge, Stephen F Kry, Rick Franich

Faculty, Staff and Student Publications

Dosimetry audits for passive motion management require dynamically-acquired measurements in a moving phantom to be compared to statically calculated planned doses. This study aimed to characterise the relationship between planning and delivery errors, and the measured dose in the Imaging and Radiation Oncology Core (IROC) thorax phantom, to assess different audit scoring approaches. Treatment plans were created using a 4DCT scan of the IROC phantom, equipped with film and thermoluminescent dosimeters (TLDs). Plans were created on the average intensity projection from all bins. Three levels of aperture complexity were explored: dynamic conformal arcs (DCAT), low-, and high-complexity volumetric modulated arcs …

Girth-Based Administered Activity For Pediatric 99mtc-Dmsa Spect, Ye Li, Justin L Brown, Jingyan Xu, Junyu Chen, Michael Ghaly, Monet Dugan, Xinhua Cao, Yong Du, Frederic H Fahey, Wesley Bolch, George Sgouros, Eric C Frey

Faculty, Staff and Student Publications

Background: Pediatric molecular imaging requires a balance between administering an activity that will yield sufficient diagnostic image quality while maintaining patient radiation exposure at acceptable levels. In current clinical practice, this balance is arrived at by the current North American Consensus Guidelines in which patient weight is used to recommend the administered activity (AA).

Purpose: We have previously demonstrated that girth (waist circumference at the level of the kidneys) is better at equalizing image quality than patient weight for pediatric Tc-99m DMSA renal function imaging. However, the correlation between image quality (IQ), AA, and patient girth has not been rigorously …

Quantitative Dual-Energy Computed Tomography With Cesium As A Novel Contrast Agent For Localization Of Thermochemical Ablation In Phantoms And Ex Vivo Models, Emily A Thompson, Megan C Jacobsen, David T Fuentes, Rick R Layman, Erik N K Cressman

Faculty, Staff and Student Publications

Background: Thermochemical ablation (TCA) is a minimally invasive therapy under development for hepatocellular carcinoma. TCA simultaneously delivers an acid (acetic acid, AcOH) and base (sodium hydroxide, NaOH) directly into the tumor, where the acid/base chemical reaction produces an exotherm that induces local ablation. However, AcOH and NaOH are not radiopaque, making monitoring TCA delivery difficult.

Purpose: We address the issue of image guidance for TCA by utilizing cesium hydroxide (CsOH) as a novel theranostic component of TCA that is detectable and quantifiable with dual-energy CT (DECT).

Materials and methods: To quantify the minimum concentration of CsOH that can be positively …

Analysis Of Performance And Failure Modes Of The Iroc Proton Liver Phantom, Hunter Mehrens, Paige Taylor, Paola Alvarez, Stephen Kry

Faculty, Staff and Student Publications

Purpose: To analyze trends in institutional performance and failure modes for the Imaging and Radiation Oncology Core’s (IROC’s) proton liver phantom.

Materials and Methods: Results of 66 phantom irradiations from 28 institutions between 2015 and 2020 were retrospectively analyzed. Univariate analysis and random forest models were used to associate irradiation conditions with phantom results. Phantom results included pass/fail classification, average thermoluminescent dosimeter (TLD) ratio of both targets, and percentage of pixels passing gamma of both targets. The following categories were evaluated in terms of how they predicted these outcomes: irradiation year, treatment planning system (TPS), TPS algorithm, treatment machine, number …

Monte Carlo-Derived 99m Tc Uptake Quantification With Commercial Planar Mbi: Tumor And Breast Activity Concentrations, Benjamin P Lopez, S Cheenu Kappadath

Faculty, Staff and Student Publications

BACKGROUND: Current molecular breast imaging (MBI) images are limited to qualitative evaluation, not absolute measurement, of

PURPOSE: This work assesses the accuracy of previously-published and newly-proposed tumor and normal breast tissue

METHODS: Quantification techniques were tested in over 4000 simulated acquisitions of spherical and ellipsoid tumors with clinically relevant uptake conditions using a validated Monte Carlo application of the GE Discovery NM750b system. The evaluated techniques consisted of four tumor total activity methodologies (two single-detector-based and two geometric-mean-based), two tumor MBI volume methodologies (diameter-based and ROI-based), and two normal tissue activity concentration methodologies (single-detector-based and geometric-mean-based). The most accurate of …

A Virtual Audit System For Intensity-Modulated Radiation Therapy Credentialing In Japan Clinical Oncology Group Clinical Trials: A Pilot Study, Mitsuhiro Nakamura, Dejun Zhou, Toshiyuki Minemura, Satoshi Kito, Hiroyuki Okamoto, Naoki Tohyama, Masahiko Kurooka, Yu Kumazaki, Masayori Ishikawa, Catharine H Clark, Elizabeth Miles, Joerg Lehmann, Nicolaus Andratschke, Stephen Kry, Satoshi Ishikura, Takashi Mizowaki, Teiji Nishio

Faculty, Staff and Student Publications

Purpose: The Medical Physics Working Group of the Radiation Therapy Study Group at the Japan Clinical Oncology Group is currently developing a virtual audit system for intensity-modulated radiation therapy dosimetry credentialing. The target dosimeters include films and array detectors, such as ArcCHECK (Sun Nuclear Corporation, Melbourne, Florida, USA) and Delta4 (ScandiDos, Uppsala, Sweden). This pilot study investigated the feasibility of our virtual audit system using previously acquired data.

Methods: We analyzed 46 films (32 and 14 in the axial and coronal planes, respectively) from 29 institutions. Global gamma analysis between measured and planned dose distributions used the following settings: 3%/3 …

A Model For Gastrointestinal Tract Motility In A 4d Imaging Phantom Of Human Anatomy, Ergys Subashi, Paul Segars, Harini Veeraraghavan, Joseph Deasy, Neelam Tyagi

Faculty, Staff and Student Publications

BACKGROUND: Gastrointestinal (GI) tract motility is one of the main sources for intra/inter-fraction variability and uncertainty in radiation therapy for abdominal targets. Models for GI motility can improve the assessment of delivered dose and contribute to the development, testing, and validation of deformable image registration (DIR) and dose-accumulation algorithms.

PURPOSE: To implement GI tract motion in the 4D extended cardiac-torso (XCAT) digital phantom of human anatomy.

MATERIALS AND METHODS: Motility modes that exhibit large amplitude changes in the diameter of the GI tract and may persist over timescales comparable to online adaptive planning and radiotherapy delivery were identified based on …

Monte Carlo-Derived 99m Tc Uptake Quantification With Commercial Planar Mbi: Absolute Tumor Activity, Benjamin P Lopez, Srinivas Cheenu Kappadath

Faculty, Staff and Student Publications

BACKGROUND: Molecular breast imaging (MBI) of 99mTc-sestamibi is an emerging adjunct qualitative tool in the detection and diagnosis of breast cancer.

PURPOSE: This work outlines the development and performance evaluation of a methodology to absolutely quantify tumor 99mTc activity uptake using a commercially available dual-headed MBI system by implementing corrections for background, scatter, attenuation, and detector characteristics.

METHODS: A validated Monte Carlo application of a commercial MBI system was used to simulate over 7000 unique acquisitions of spherical and ellipsoidal tumors in breast tissue. Tumor absolute activity was calculated following background, scatter, and attenuation corrections of tumor region of interest …

Development Of A Qa Plan For A 3.0t Cannon Galan Mr-Sim, Nathaniel D. Teague

Theses and Dissertations

Purpose: To develop and incorporate a QA (quality assurance) program for a Canon Galan 3 tesla MR Simulator for applications in radiation therapy.

Methods and materials: The QA program was centered around tests performed with three separate levels of frequency. The daily QA procedure consisted of scanning a vendor provided daily QA cube phantom that measures basic performance parameters. Additionally, a series of basic safety check were performed. The monthly QA procedure consisted of several tests, including scanning the ACR MRI large accreditation phantom and manually performing its corresponding image quality tests. Scanning the MagPhan RT for its detailed geometric …

Adding Customized Electron Energy Beams To Truebeam Linear Accelerators, Song Gao, Manickam Muruganandham, Weiliang Du, Jared Ohrt, Rajat J Kudchadker, Peter A Balter

Faculty, Staff and Student Publications

Purpose: To better meet clinical needs and facilitate optimal treatment planning, we added two new electron energy beams (7 and 11 MeV) to two Varian TrueBeam linacs.

Methods: We worked with the vendor to create two additional customized electron energies without hardware modifications. For each beam, we set the bending magnet current and then optimized other beam-specific parameters to achieve depths of 50% ionization (I50 ) of 2.9 cm for 7 MeV and 4.2 cm for the 11 MeV beam with the 15 × 15 cm2 cone at 100 cm source-to-surface distance (SSD) by using an ionization chamber profiler (ICP) …