Radiation Medicine Commons^™

Knowledge Based Automated Planning For Non-Coplanar Vmat Stereotactic Radiosurgery In Ocular Malignancies, Chase Cochran, Shane Mccarthy, William St. Clair, Damodar Pokhrel

Radiation Medicine Faculty Publications

Background and Purpose: Stereotactic radiosurgery/radiotherapy (SRS/SRT) has emerged as a less invasive alternative to enucleation in the management of ocular malignancies. SRS/SRT planning is time-consuming, complex, and the plan quality depends on the experience of the treatment planner. We demonstrate the use of RapidPlan modeling in conjunction with HyperArc for the treatment of ocular diseases to improve planning efficiency, consistency, and quality.

Materials and Methods: A HyperArc-based RapidPlan (HARP) model was iteratively trained on 80 patient datasets that simulated ocular malignancies. Twenty additional patient datasets were reserved for model testing and comparison with manual plans. Each testing dataset was both …

Designing Theranostic Radiopharmaceutical Trials For Uterine Cervix Cancer, Denise Fabian, Molly E. Buffington, Brianna S. Cagle, Steve M. Keefe, Michael K. Schultz, Charles A. Kunos

Radiation Medicine Faculty Publications

Designing and interpreting early phase trials of theranostic radiopharmaceuticals remains challenging because it is difficult to isolate effective levels of activity in enriched patient populations that would be worth following up in later-phase development. This study explores the known challenges and emerging opportunities for clinical research on patients with uterine cervical cancer. We identified eight randomized combination trials for advanced-stage uterine cervix cancer that were activated between 2011 and 2022 and tabulated their results to determine whether combinations were better than individual constituents and which suitable study population is best situated for the study of a new theranostic agent. In …

A Knowledge-Based Planning Model To Identify Fraction-Reduction Opportunities In Brain Stereotactic Radiotherapy, Shane Mccarthy, William St. Clair, Damodar Pokhrel

Radiation Medicine Faculty Publications

Objective: To develop and validate a HyperArc-based RapidPlan (HARP) model for three-fraction brain stereotactic radiotherapy (SRT) plans to then use to replan previously treated five-fraction SRT plans. Demonstrating the possibility of reducing the number of fractions while achieving acceptable organs-at-risk (OAR) doses with improved target biological effective dose (BED) to brain lesions. Methods: Thirty-nine high-quality clinical three-fraction HyperArc brain SRT plans (24–27 Gy) were used to train the HARP model, with a separate 10 plans used to validate its effectiveness. Fifty-eight five-fraction HyperArc brain SRT plans (30–40 Gy) attempted to be retrospectively replanned for three fractions scheme using the HARP …

An Investigation Into The Feasibility And Efficacy Of Stereotactic Radiosurgery For 1–3 Cm Single Brain Lesions On The Ring-Mounted Halcyon Linac, Kristin J. Hazelwood, Shane Mccarthy, Josh Misa, David Castelvetere, William St. Clair, Damodar Pokhrel

Radiation Medicine Faculty Publications

Purpose: An evaluation of the accuracy, safety, and efficiency of the Halcyon ring delivery system (RDS) for stereotactic radiosurgery (SRS) treatment to relatively small (1–3 cm) brain lesions.

Methods: After completing the extensive in-house quality assurance checks including Winston–Lutz test and independent dose verification via MD Anderson IROC SRS head phantom irradiation on Halcyon, fifteen brain SRS patients previously treated with a single dose of 20 Gy on TrueBeam (6MV-FFF) with HyperArc geometry were retrospectively replanned on Halcyon (6MV-FFF). Plan quality metrics including conformity index (CI), gradient index (GI), gradient distance (GD), PTV coverage, gross tumor volume (GTV) dose, heterogeneity …

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 …

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 …

Combining Spatially Fractionated Radiation Therapy (Sfrt) And Immunotherapy Opens New Rays Of Hope For Enhancing Therapeutic Ratio, Qiuxia Lu, Weisi Yan, Alan Zhu, Slavisa Tubin, Waleed F. Mourad, Jun Yang

Radiation Medicine Faculty Publications

Spatially Fractionated Radiation Therapy (SFRT) is a form of radiotherapy that delivers a single large dose of radiation within the target volume in a heterogeneous pattern with regions of peak dosage and regions of under dosage. SFRT types can be defined by how the heterogeneous pattern of radiation is obtained. Immune checkpoint inhibitors (ICIs) have been approved for various malignant tumors and are widely used to treat patients with metastatic cancer. The efficacy of ICI monotherapy is limited due to the “cold” tumor microenvironment. Fractionated radiotherapy can achieve higher doses per fraction to the target tumor, and induce immune activation …

A Measure Of Srs/Srt Plan Quality: Quantitative Limits For Intermediate Dose Spill (R50%) In Linac-Based Delivery, Dharmin D. Desai, Ivan L. Cordrey, Ellis L. Johnson

Radiation Medicine Faculty Publications

Stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT) of multiple cranial targets using a single isocenter on conventional C-arm linear accelerators are rapidly developing clinical techniques. However, no universal guidelines for acceptable intermediate dose spill limits are currently available or widely accepted. In this work, we propose an intermediate dose spill guidance range for cranial SRS/SRT delivered on C-arm linacs with MLC collimation for single PTV plans and single isocenter multiple target plans with PTV volumes in the range 0.02–57.9 cm³. We quantify intermediate dose spill with the R50% metric (R50% = volume of 50% of prescription isodose cloud …

Feasibility Of Using Ring-Mounted Halcyon Linac For Single-Isocenter/Two-Lesion Lung Stereotactic Body Radiation Therapy, Damodar Pokhrel, Aaron Webster, Richard Mallory, Justin Visak, Mark E. Bernard, Ronald C. Mcgarry, Mahesh Kudrimoti

Radiation Medicine Faculty Publications

PURPOSE: To demonstrate the plan quality and delivery efficiency of volumetric-modulated arc therapy (VMAT) with the Halcyon Linac ring delivery system (RDS) in the treatment of single-isocenter/two-lesion lung stereotactic body radiation therapy (SBRT).

MATERIALS/METHODS: Sixteen previously treated non-coplanar VMAT single-isocenter/two-lesion lung SBRT plans delivered with SBRT-dedicated C-arm TrueBeam Linac were selected. Prescribed dose was 50 Gy to each lesion over five fractions with treatment delivery every other day and AcurosXB algorithm as the final dose calculation algorithm. TrueBeam single-isocenter plans were reoptimized for Halcyon Linac with coplanar geometry. Both TrueBeam and Halcyon plans were normalized for identical combined target coverage …

Fast Generation Of Lung Sbrt Plans With A Knowledge-Based Planning Model On Ring-Mounted Halcyon Linac, Justin Visak, Aaron Webster, Mark E. Bernard, Mahesh R. Kudrimoti, Marcus E. Randall, Ronald C. Mcgarry, Damodar Pokhrel

Radiation Medicine Faculty Publications

PURPOSE: To demonstrate fast treatment planning feasibility of stereotactic body radiation therapy (SBRT) for centrally located lung tumors on Halcyon Linac via a previously validated knowledge-based planning (KBP) model to support offline adaptive radiotherapy.

MATERIALS/METHODS: Twenty previously treated non-coplanar volumetric-modulated arc therapy (VMAT) lung SBRT plans (c-Truebeam) on SBRT-dedicated C-arm Truebeam Linac were selected. Patients received 50 Gy in five fractions. c-Truebeam plans were re-optimized for Halcyon manually (m-Halcyon) and with KBP model (k-Halcyon). Both m-Halcyon and k-Halcyon plans were normalized for identical or better target coverage than clinical c-Truebeam …

Predicting The Effect Of Indirect Cell Kill In The Treatment Of Multiple Brain Metastases Via Single-Isocenter/Multitarget Volumetric Modulated Arc Therapy Stereotactic Radiosurgery, Allison N. Palmiero, Denise Fabian, Marcus E. Randall, William St. Clair, Damodar Pokhrel

Radiation Medicine Faculty Publications

PURPOSE: Due to spatial uncertainty, patient setup errors are of major concern for radiosurgery of multiple brain metastases (m-bm) when using single-isocenter/multitarget (SIMT) volumetric modulated arc therapy (VMAT) techniques. However, recent clinical outcome studies show high rates of tumor local control for SIMT-VMAT. In addition to direct cell kill (DCK), another possible explanation includes the effects of indirect cell kill (ICK) via devascularization for a single dose of 15 Gy or more and by inducing a radiation immune intratumor response. This study quantifies the role of indirect cell death in dosimetric errors as a function of spatial patient setup uncertainty …

Computer Automation For Physics Chart Check Should Be Adopted In Clinic To Replace Manual Chart Checking For Radiotherapy, Edward L. Clouser, Quan Chen, Yi Rong

Radiation Medicine Faculty Publications

No abstract provided.

An Analytical Expression For R50% Dependent On Ptv Surface Area And Volume: A Cranial Srs Comparison, Dharmin D. Desai, Ellis Lee Johnson, Ivan L. Cordrey

Radiation Medicine Faculty Publications

The intermediate dose spill for a stereotactic radiosurgery (SRS) plan can be quantified with the metric R50%, defined as the 50% isodose cloud volume (V_IDC50%) divided by the volume of the planning target volume (PTV). By coupling sound physical principles with the basic definition of R50%, we derive an analytical expression for R50% for a spherical PTV. Our analytical expression depends on three quantities: the surface area of PTV (SA_PTV), the volume of PTV (V_PTV), and the distance of dose drop-off to 50% (Δr). The value of ∆r was obtained from a simple set …

A Novel And Clinically Useful Dynamic Conformal Arc (Dca)-Based Vmat Planning Technique For Lung Sbrt, Damodar Pokhrel, Justin Visak, Lana Sanford

Radiation Medicine Faculty Publications

PURPOSE: Volumetric modulated arc therapy (VMAT) is gaining popularity for stereotactic treatment of lung lesions for medically inoperable patients. Due to multiple beamlets in delivery of highly modulated VMAT plans, there are dose delivery uncertainties associated with small-field dosimetry error and interplay effects with small lesions. We describe and compare a clinically useful dynamic conformal arc (DCA)-based VMAT (d-VMAT) technique for lung SBRT using flattening filter free (FFF) beams to minimize these effects.

MATERIALS AND METHODS: Ten solitary early-stage I-II non-small-cell lung cancer (NSCLC) patients were treated with a single dose of 30 Gy using 3-6 non-coplanar VMAT arcs (clinical …

Prognostic Factors For Elderly Patients Treated With Stereotactic Body Radiation Therapy For Pancreatic Adenocarcinoma, Philip A. Sutera, Mark E. Bernard, Hong Wang, Dwight E. Heron

Radiation Medicine Faculty Publications

Introduction: Pancreatic ductal adenocarcinoma (PDAC) commonly presents later in life with a median age at diagnosis of 70 years. Unfortunately, elderly patients are significantly underrepresented in clinical trials. Stereotactic body radiation therapy (SBRT) is a promising treatment modality in this population as it has demonstrated excellent local control with minimal toxicity. We aimed to determine prognostic factors associated with outcomes in elderly patients treated with SBRT.

Materials and Methods: Elderly patients older than 70 treated with SBRT for PDAC at our institution, from 2004 to 2014 were included. Our primary endpoints included overall survival (OS) and local-progression-free survival (LPFS). Secondary …