Radiation Medicine Commons^™

A Predictive Quality Assurance Model For Patient-Specific Gamma Passing Rate Of Hyperarc-Based Stereotactic Radiotherapy And Radiosurgery Of Brain Metastases, Shane Mccarthy, Brent Harrison, Damodar Pokhrel

Radiation Medicine Faculty Publications

Objective: Measurement-based patient specific quality assurance (PSQA) is an increasingly debated topic among medical physicists. Developments like online adaptive radiotherapy and same-day stereotactic treatments limit the time to do measurement-based PSQA. Herein, we develop a predictive machine learning model to supplement PSQA by predicting the gamma passing rate (GPR) per stereotactic arc. This streamlines PSQA, providing planners the insight to replan potentially sub-optimal plans, to mitigate machine time inefficiencies.

Methods: 122 patients that had previously received HyperArc stereotactic radiosurgery/radiotherapy on a TrueBeam LINAC (Millenium 120 MLCs, 6MV-FFF) were used to generate a long short-term memory (LSTM) recurrent neural network to …

Automated Hippocampal Sparing Whole Brain Radiotherapy With Simultaneous Integrated Boost For Multiple Brain Metastases: Halcyon, Hyperarc On Truebeam, And Coplanar Truebeam, Shane Mccarthy, Ryan Clark, Anthony Magliari, William St. Clair, Damodar Pokhrel

Radiation Medicine Faculty Publications

Purpose: To demonstrate the ease and feasibility that hippocampal sparing whole brain (WB) simultaneous integrated boost (HSWB-SIB) plans can be generated using knowledge-based planning and Eclipse Scripting Application Programming Interface (ESAPI) for three different modalities, HyperArc on TrueBeam (TB-HA), a coplanar beam arrangement on TrueBeam (TB-Co), and the ring-mounted Halcyon LINAC (Hal).

Methods: Twelve patients with 2–14 brain metastases were retrospectively replanned for HSWB-SIB using a published HSWB RapidPlan model with modifications for the automated addition of SIB to metastases. Prescribed dose was 30 Gy to the WB planning target volume (PTV) and 50 Gy to the metastases in 10 …

Feasibility Of Treatment Planning With Hyperarc Stereotactic Radiosurgery Methods For Ocular Tumors, Chase Cochran, Shane Mccarthy, William St. Clair, Damodar Pokhrel

Radiation Medicine Faculty Publications

Purpose/objectives

Currently, ocular disease is primarily managed with COMS plaque brachytherapy. Various stereotactic radiosurgery (SRS) platforms have also been employed, yet widespread access remains a challenge. Herein, we demonstrate the feasibility of using the HyperArc SRS system to provide an additional platform for the treatment of ocular malignancies.

Materials/methods

Twenty previously treated COMS patients with ocular melanoma were selected for a retrospective HyperArc SRS planning study. The average gross tumor volume (GTV) derived from MRI was 1.19 ± 0.60 cc. Planning target volumes (PTV) were generated from a 2 mm expansion of the GTVs. HyperArc plans were created for a …

A Two-Hit Model Of Executive Dysfunction: Simulated Galactic Cosmic Radiation Primes Latent Deficits Revealed By Sleep Fragmentation, Richard A. Britten, Ella N. Tamgue, Paola Arriaga Alvarado, Arriyam S. Fesshaye, Larry D. Sanford

Department Radiation Oncology & Biophysics Faculty Publications

Future Artemis-class missions to Mars will expose astronauts to prolonged space radiation (SR), sleep disruption, and operational demands requiring greater autonomy, placing decision making and executive function at heightened risk. Both SR and sleep fragmentation (SF) independently impair cognition, yet their combined effects remain poorly understood. Using the Associative Recognition Memory and Interference (ARMIT) task, we assessed cognitive performance in male rats exposed to 10 cGy of Galactic Cosmic Ray simulation (GCRsim), SF, or both. Under well-rested conditions, GCRsim-exposed rats exhibited overt deficits in the C.1.2 stage, performing at chance when reinforcement contingencies shifted, consistent with impaired cognitive flexibility. In …

Demonstration Of An Enhanced Dosing Pattern For Debulking Large And Bulky Unresectable Tumors Via Differential Hole-Size Spatially Fractionated Radiotherapy, Joshua Misa, William St. Clair, Damodar Pokhrel

Radiation Medicine Faculty Publications

Purpose/objective

We propose a novel lattice deployment for spatially fractionated radiotherapy (SFRT) treatments. In this approach, a larger diameter high-dose sphere is centrally placed in the bulky tumor mass and surrounded by smaller diameter high-dose spheres.

Materials/methods

Thirty SFRT patients (10 head and neck [HN], 10 abdominal/pelvis, and 10 chest/lung cases) treated with an MLC-based crossfire method were retrospectively analyzed. Eleven differential hole-size lattice patterns were benchmarked against the clinically delivered SFRT plans (1 cm diameter cylinders, 2 cm spacing) and the standard uniform lattice pattern (1.5 cm diameter spheres, 3 cm spacing). These patterns varied in core diameter (C: …

In Vitro Α/Β Ratio Variations In Cervical Cancer, With Consequent Effects On Equivalent Dose In 2 Gy Fraction In High-Dose-Rate Brachytherapy, Cameron Thayer-Freeman, Brien Washington, Denise Fabian, Dennis C. Cheek, William St. Clair, Mark E. Bernard, Wei Luo

Radiation Medicine Faculty Publications

Purpose: To determine the distributions of published α/β values measured in vitro and the resulting uncertainties in the equivalent dose in 2 Gy fractions (EQD ₂ ) when applied to high-dose-rate brachytherapy (HDR-BT) for cervical cancer.

Methods and Materials: An analysis of 98 published α/β values from 31 papers was conducted, spanning 23 cervical cancer cell lines. Values were further divided into squamous cell carcinoma and adenocarcinoma histologies. Probability distributions were fit to histograms using the bootstrapped Kolmogorov-Smirnov goodness-of-fit test. Both average and most probable α/β values for cervical cancer were determined. The probability distributions were then applied to three …

Development And Clinical Validation Of Automated Same-Day Stereotactic Treatment Procedures For Multiple Brain Metastases And Recurrent Head And Neck Cancers, Shane Mccarthy

Theses and Dissertations--Radiation Medicine

As technology advances, more and more cancer patients are benefiting from the use of stereotactic radiosurgery and radiotherapy (SRS/SRT) to treat their disease. One such technology, Varian’s HyperArc high-definition radiosurgery module, a tool to help facilitate the treatment of brain metastases on a medical linear accelerator (LINAC), has been demonstrated to achieve comparable low dose spillage and target conformity compared to the current gold standard for intracranial malignancies, the Elekta Gamma Knife. Furthermore, due to HyperArc’s single-isocenter multiple lesion approach, the treatment can be delivered in a significantly shorter amount of time. Unfortunately, the manual process of creating these stereotactic …

A Fast Framework For Generating Radioactive Mixture Spectra And Its Application To Remote High-Performance Mixture Identification, Chiman Kwan, Bulent Ayhan, Adam Stavola, Kazi Aminul Islam, Hongfang Zhang, Jiang Li

Electrical & Computer Engineering Faculty Publications

Remote detection of radioactive materials in mixtures using handheld or portal detectors remains a challenge because of factors such as low concentration, environmental interference, sensor noise, and other complications. This work introduces a fast framework for generating realistic mixture spectra. Moreover, we present mixture isotope identification using data generated by the fast framework. Researchers have examined a range of conventional and recent algorithms within the fields of machine learning and deep learning. An application to uranium enrichment-level prediction has been included. Extensive simulation experiments validated the efficacy of the proposed framework.

Three-Dimensional Deep Learning Normal Tissue Complication Probability Model To Predict Late Xerostomia In Patients With Head And Neck Cancer, Hung Chu, Suzanne P M De Vette, Hendrike Neh, Nanna M Sijtsema, Roel J H M Steenbakkers, Amy Moreno, Johannes A Langendijk, Peter M A Van Ooijen, Clifton D Fuller, Lisanne V Van Dijk

Faculty, Staff and Student Publications

Purpose: Conventional normal tissue complication probability (NTCP) models for patients with head and neck cancer are typically based on single-value variables, which, for radiation-induced xerostomia, are baseline xerostomia and mean salivary gland doses. This study aimed to improve the prediction of late xerostomia by using 3-dimensional information from radiation dose distributions, computed tomography imaging, organ-at-risk segmentations, and clinical variables with deep learning (DL).

Methods and materials: An international cohort of 1208 patients with head and neck cancer from 2 institutes was used to train and twice validate DL models (deep convolutional neural network, EfficientNet-v2, and ResNet) with 3-dimensional dose distribution, …

Reduced Set-Shifting Processing Speed In Male Rats Following Low Dose (10 Cgy) Proton Exposure, Hui Ho Vanessa Chang, Gyutae Kim, Kyu-Sung Kim, Richard A. Britten

Center for Integrative Neuroscience and Inflammatory Diseases (CINID) Faculty Publications

Space radiation (SR) exposure poses significant biomedical risks, including effects on the central nervous system (CNS). These risks are particularly relevant to cognitive function during long-duration space missions. One critical cognitive skill is decision-making, which requires attentional set-shifting (ATSET)—the ability to quickly assess problems, evaluate options, and select the best actions. Previous studies have shown that exposure to However, the impact of low LET (< 1 keV/μm) protons, which significantly contribute to the total radiation flux astronauts encounter within spacecraft, on ATSET performance is unknown. To address this gap, we evaluated the effects of cranial irradiation with 10 cGy of 100 MeV/n protons (LET = 0.732 keV/μm) on ATSET performance in male Sprague-Dawley rats. We also investigated whether concurrent exposure to variable gravity (hypergravity step-up, step down, purported to have the same effect as exposure to microgravity (another major spaceflight stressor) exacerbated SR-induced cognitive deficits. Our findings indicate that proton exposure alone significantly impaired ATSET performance, as evidenced by decreased processing speed while performing compound discrimination reversal and extra-dimensional shifting. Notably, no additive or synergistic effects were observed when hypergravity was combined with proton exposure. The impact that low-dose proton exposure has on CNS functionality, particularly in reducing processing speed during complex tasks, warrant further investigation. If similar cognitive deficits were to occur in astronauts exposed to galactic cosmic rays, mission success and safety could be significantly compromised.

Machine Learning Models For Pancreatic Cancer Survival Prediction: A Multi-Model Analysis Across Stages And Treatments Using The Surveillance, Epidemiology, And End Results (Seer) Database, Aditya Chakraborty, Mohan D. Pant

Epidemiology, Biostatistics, & Environmental Health Faculty Publications

Background: Pancreatic cancer is among the most lethal malignancies, with poor prognosis and limited survival despite treatment advances. Accurate survival modeling is critical for prognostication and clinical decision-making. This study had three primary aims: (1) to determine the best-fitting survival distribution among patients diagnosed and deceased from pancreatic cancer across stages and treatment types; (2) to construct and compare predictive risk classification models; and (3) to evaluate survival probabilities using parametric, semi-parametric, non-parametric, machine learning, and deep learning methods for Stage IV patients receiving both chemotherapy and radiation. Methods: Using data from the SEER database, parametric models (Generalized Extreme Value, …