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, …

A Radiotherapy Community Data-Driven Approach To Determine Which Complexity Metrics Best Predict The Impact Of Atypical Tps Beam Modeling On Clinical Dose Calculation Accuracy, Fre'etta Mae Dayo Brooks, Mallory Carson Glenn, Victor Hernandez, Jordi Saez, Hunter Mehrens, Julianne Marie Pollard-Larkin, Rebecca Maureen Howell, Christine Burns Peterson, Christopher Lee Nelson, Catharine Helen Clark, Stephen Frasier Kry

Faculty, Staff and Student Publications

PURPOSE: To quantify the impact of treatment planning system beam model parameters, based on the actual spread in radiotherapy community data, on clinical treatment plans and determine which complexity metrics best describe the impact beam modeling errors have on dose accuracy.

METHODS: Ten beam modeling parameters for a Varian accelerator were modified in RayStation to match radiotherapy community data at the 2.5, 25, 50, 75, and 97.5 percentile levels. These modifications were evaluated on 25 patient cases, including prostate, non-small cell lung, H&N, brain, and mesothelioma, generating 1,000 plan perturbations. Differences in the mean planned dose to clinical target volumes …

Deep Learning-Based Dose Prediction To Improve The Plan Quality Of Volumetric Modulated Arc Therapy For Gynecologic Cancers, Mary P Gronberg, Anuja Jhingran, Tucker J Netherton, Skylar S Gay, Carlos E Cardenas, Christine Chung, David Fuentes, Clifton D Fuller, Rebecca M Howell, Meena Khan, Tze Yee Lim, Barbara Marquez, Adenike M Olanrewaju, Christine B Peterson, Ivan Vazquez, Thomas J Whitaker, Zachary Wooten, Ming Yang, Laurence E Court

Faculty, Staff and Student Publications

Background: In recent years, deep‐learning models have been used to predict entire three‐dimensional dose distributions. However, the usability of dose predictions to improve plan quality should be further investigated.

Purpose: To develop a deep‐learning model to predict high‐quality dose distributions for volumetric modulated arc therapy (VMAT) plans for patients with gynecologic cancer and to evaluate their usability in driving plan quality improvements.

Methods: A total of 79 VMAT plans for the female pelvis were used to train (47 plans), validate (16 plans), and test (16 plans) 3D dense dilated U‐Net models to predict 3D dose distributions. The models received the …

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 …

Quality Assurance Assessment Of Intra-Acquisition Diffusion-Weighted And T2-Weighted Magnetic Resonance Imaging Registration And Contour Propagation For Head And Neck Cancer Radiotherapy, Mohamed A Naser, Kareem A Wahid, Sara Ahmed, Vivian Salama, Cem Dede, Benjamin W Edwards, Ruitao Lin, Brigid Mcdonald, Travis C Salzillo, Renjie He, Yao Ding, Moamen Abobakr Abdelaal, Daniel Thill, Nicolette O'Connell, Virgil Willcut, John P Christodouleas, Stephen Y Lai, Clifton D Fuller, Abdallah S R Mohamed

Faculty, Staff and Student Publications

BACKGROUND/PURPOSE: Adequate image registration of anatomical and functional magnetic resonance imaging (MRI) scans is necessary for MR-guided head and neck cancer (HNC) adaptive radiotherapy planning. Despite the quantitative capabilities of diffusion-weighted imaging (DWI) MRI for treatment plan adaptation, geometric distortion remains a considerable limitation. Therefore, we systematically investigated various deformable image registration (DIR) methods to co-register DWI and T2-weighted (T2W) images.

MATERIALS/METHODS: We compared three commercial (ADMIRE, Velocity, Raystation) and three open-source (Elastix with default settings [Elastix Default], Elastix with parameter set 23 [Elastix 23], Demons) post-acquisition DIR methods applied to T2W and DWI MRI images acquired during the same …

Development And Validation Of A Checklist For Use With Automatically Generated Radiotherapy Plans, Kelly A Nealon, Laurence E Court, Raphael J Douglas, Lifei Zhang, Eun Young Han

Faculty, Staff and Student Publications

Purpose: To develop a checklist that improves the rate of error detection during the plan review of automatically generated radiotherapy plans.

Methods: A custom checklist was developed using guidance from American Association of Physicists in Medicine task groups 275 and 315 and the results of a failure modes and effects analysis of the Radiation Planning Assistant (RPA), an automated contouring and treatment planning tool. The preliminary checklist contained 90 review items for each automatically generated plan. In the first study, eight physicists were recruited from our institution who were familiar with the RPA. Each physicist reviewed 10 artificial intelligence-generated resident …

A Roadmap To Clinical Trials For Flash, Paige A Taylor, Jean M Moran, David A Jaffray, Jeffrey C Buchsbaum

Faculty, Staff and Student Publications

While FLASH radiation therapy is inspiring enthusiasm to transform the field, it is neither new nor well understood with respect to the radiobiological mechanisms. As FLASH clinical trials are designed, it will be important to ensure we can deliver dose consistently and safely to every patient. Much like hyperthermia and proton therapy, FLASH is a promising new technology that will be complex to implement in the clinic and similarly will require customized credentialing for multi-institutional clinical trials. There is no doubt that FLASH seems promising, but many technologies that we take for granted in conventional radiation oncology, such as rigorous …

Knowledge-Based Planning For The Radiation Therapy Treatment Plan Quality Assurance For Patients With Head And Neck Cancer, Wenhua Cao, Mary Gronberg, Adenike Olanrewaju, Thomas Whitaker, Karen Hoffman, Carlos Cardenas, Adam Garden, Heath Skinner, Beth Beadle, Laurence Court

Faculty, Staff and Student Publications

This study aimed to investigate the feasibility of using a knowledge-based planning technique to detect poor quality VMAT plans for patients with head and neck cancer. We created two dose-volume histogram (DVH) prediction models using a commercial knowledge-based planning system (RapidPlan, Varian Medical Systems, Palo Alto, CA) from plans generated by manual planning (MP) and automated planning (AP) approaches. DVHs were predicted for evaluation cohort 1 (EC1) of 25 patients and compared with achieved DVHs of MP and AP plans to evaluate prediction accuracy. Additionally, we predicted DVHs for evaluation cohort 2 (EC2) of 25 patients for which we intentionally …

A Quantitative Method For Reproducible Ionization Chamber Alignment To A Water Surface For External Beam Radiation Therapy Depth Dose Measurements, James Ververs

Theses and Dissertations

Ionization chambers (ICs) are the most commonly used detectors for radiation therapy dose measurements. Typical IC measurements use cylindrical ICs in a water phantom and therefore require initial IC alignment to the water surface. This alignment has long been ignored and only recently has a qualitative governing recommendation been made. This thesis describes a reproducible methodology for quantitative ionization chamber water surface alignment. Depth-ionization measurements are taken with twenty-eight IC designs under varying conditions including, but not limited to, changes in scan direction, speed, and resolution, radiation beam type, field size, energy, and electron contamination. Measurements are acquired using standard …