Radiation Medicine Commons^™

A Dosimetric Comparison Of Halcyon 6x-Fff And Truebeam 6x In Prone Left Whole Breast Radiation Therapy, Maritza Soto, Kelly Labant, M.S., Cmd, Rt(T), Kristen Vu, M.S., Cmd, Rt(T)

Masters Projects

Purpose:

This retrospective study compared dosimetric differences between prone left whole breast radiation (WBRT) treatment plans originally generated for Halcyon using 6X flattening- filter-free (FFF) beams and replanned for a conventional TrueBeam using 6X beams.

Methods:

Ten prone whole left breast treatment plans were paired and retrospectively analyzed. Clinically treated Halcyon 6X flattening filter free plans were replanned on TrueBeam using flattened 6X beams in Eclipse v16.1. Contours for all plans were generated using artificial intelligence-based autosegmentation, reviewed by a medical dosimetrist and radiation oncologist, and forward planned with a tangent technique in EZFluence to achieve identical planning objectives. Dose …

The Impact Of Scar Wires On Dose Distribution Of Electron Fields, Ahmad Nour

Masters Projects

Purpose: This phantom study looked at whether changing the Hounsfield unit (HU) value for radiopaque scar wires in Eclipse changed the calculated electron dose distribution. Methods and Materials: Radiopaque wires were placed in the same abdominal area on an anthropomorphic phantom. The wires were set up in a circle. The CT images were brought into Eclipse, the wires were contoured, and the planning target volume was made 1 cm inside the circle of wire. For every wire size and electron energy, two matching plans were made: one plan with no density override and one plan with a density override applied …

Dosimetric Comparison Between Geometric Centroid And Minimax Isocenter Placement In Single Isocenter Multitarget Stereotactic Radiosurgery Plans In Hyperarc, Matthew Gloudeman

Masters Projects

Single-isocenter multi-target (SIMT) stereotactic radiosurgery (SRS) utilizing Varian HyperArc streamlines clinical workflows but introduces geometric sensitivity for distant outlier lesions when rotational and setup uncertainties are taken into account. The default isocenter location in the HyperArc workspace is the geometric centroid, which is inherently biased toward clusters of lesions. This study evaluates the dosimetric plan quality of an alternative minimax isocenter strategy, which minimizes the maximum lesion-to-isocenter distance, shortening the rotational lever arm to enhance mechanical robustness. Two fractionated SRS (fSRS) plans were generated for ten patients with 3-5 brain metastases using identical beam configurations: one using HyperArc’s default geometric …

Dosimetric Comparison Of Hybrid 3d Conformal Radiation Therapy And Volumetric Modulated Arc Therapy Versus Vmat-Only Planning For Accelerated Partial Breast Irradiation, Erjona Jusufi

Masters Projects

Abstract

Purpose: To compare dosimetric outcomes between volumetric modulated arc therapy (VMAT)-only and hybrid VMAT plus three-dimensional conformal radiotherapy (3D-CRT) techniques for accelerated partial breast irradiation (APBI) in patients with early-stage left-sided breast cancer.

Methods and Materials: Thirty patients treated with APBI at a single institution were retrospectively replanned using both VMAT-only and hybrid (VMAT + 3D-CRT) techniques. All plans were prescribed 26 Gy in 5 fractions. Each patient was planned using the same target volumes, optimization objectives, and evaluation criteria for both techniques. Planning target volume (PTV) coverage, conformity index (CI), homogeneity index (HI), hotspot control, organ-at-risk (OAR) doses, …

Ai Integration In Radiotherapy Workflows: Emerging Trends And Best Practices, Vi T. Dinh

Radiologic Sciences

Purpose To synthesize current evidence on artificial intelligence (AI) integration in radiotherapy workflows, identify emerging application trends, and examine best practices for clinical implementation.

Method A structured literature review was conducted using PubMed, Scopus, and Google Scholar to identify peer-reviewed studies published between 2015 and 2025. Eligible studies evaluated AI applications in radiotherapy workflows, including segmentation, treatment planning, and clinical decision-making. Findings were synthesized using thematic analysis.

Results Three primary themes emerged: (a) AI-based segmentation improved contouring efficiency and reduced interobserver variability; (b) AI-assisted treatment planning enhanced dose prediction consistency and workflow reproducibility; and (c) workflow integration supported clinical decision-making …

Impact Of Mr-Linac Technology On Prostate Cancer Treatment Outcomes, Anhdiep P. Tran

Radiologic Sciences

Purpose To evaluate the impact of magnetic resonance-guided linear accelerator (MR-Linac) technology on treatment precision, clinical outcomes, and operational challenges in prostate cancer radiotherapy.

Method A systematic literature review was conducted using PubMed, Scopus, and Google Scholar to identify peer-reviewed studies published between 2018 and 2026. Eligible studies evaluated MR-Linac technology for prostate cancer and reported outcomes related to treatment precision, toxicity, workflow, and clinical effectiveness.

Results Three primary themes emerged: (a) improved treatment precision through superior soft tissue visualization, real-time target tracking, and adaptive radiotherapy; (b) improved clinical outcomes characterized by reduced radiation exposure to organs at risk, decreased …

Assault Vs. Assistance: Radiologic Technologist Decision-Making When Fall-Risk Patients Decline Assistance, Pamela O'Dowd

Radiologic Sciences

Purpose To explore how radiologic technologists experience and respond to situations involving fall-risk patients who decline assistance during imaging procedures.

Method A cross-sectional survey design was used to collect data from practicing radiologic technologists recruited through the American Society of Radiologic Technologists. Descriptive statistics, including frequencies and percentages, were analyzed using SPSS to summarize participant responses, and a thematic analysis was conducted on open-ended responses.

Results A total of 87 respondents completed the survey. Results indicated that encounters with fall-risk patients who refuse assistance are common in clinical imaging practice. Sixty-three (72.4%) technologists reported having experienced situations in which a …

Magnetic Resonance In Pregnancy: Safety Considerations, Contrast Risks, And Imaging Modality Alternatives, Lizzette Valdez

Radiologic Sciences

Purpose To examine the safety of magnetic resonance (MR) during pregnancy by evaluating fetal outcomes, contrast agent risks, and the comparative roles of MR, ultrasound, and computed tomography (CT) in prenatal imaging.

Method A literature review was conducted using PubMed and peer-reviewed radiology journals to identify studies evaluating MR safety during pregnancy. The review examined fetal and neonatal outcomes following prenatal MR exposure, trimester-specific imaging considerations, risks associated with gadolinium-based contrast agents, and comparisons among MR, ultrasound, and CT.

Results Three primary themes emerged: (a) noncontrast MR demonstrated a strong safety profile with no consistent association with adverse fetal or …

Influence Of Lumpectomy Cavity Depth On Plan Quality In 3d Arc-Based Simultaneous Integrated Boost For Whole-Breast Radiotherapy, Emmett Dwyer

Masters Projects

Abstract

Purpose: Dynamic conformal arc (DCA) is a three-dimensional (3D) radiation therapy technique that can be used to deliver a simultaneous integrated boost (SIB) during whole-breast irradiation (WBI). This study investigated whether the depth of the lumpectomy cavity affects the feasibility of creating a successful DCA SIB treatment plan for breast radiotherapy.

Methods and Materials: 30 patients who previously received WBI followed by a 3D sequential boost (SeqB) were selected for this retrospective study. A DCA plan was created for each patient and combined with the original whole-breast tangent fields to create a SIB plan. Each plan was required to …

Effect Of Hydrogel Rectal Spacers On Bladder Wall And Regional Substructure Dose In Prostate Cancer Patients Undergoing Volumetric Modulated Arc Therapy With Simultaneous Integrated Boost: A Retrospective Planning Study, Geronimo Sosa

Masters Projects

Purpose: Hydrogel rectal spacers reduce rectal dose during prostate radiotherapy, but their effect on bladder wall dose is not well characterized, particularly with volumetric modulated arc therapy with simultaneous integrated boost (VMAT-SIB). This study evaluated the effect of spacer placement on whole and regional bladder wall dose.

Methods: Twenty-nine patients treated with VMAT-SIB (70 Gy in 28 fractions) were analyzed retrospectively: 9 with and 20 without a spacer. The bladder wall was defined as the whole bladder minus a 3-mm inner margin. Primary endpoints were D0.03 cc and D1 cc; secondary endpoints included D2 cc, D3 cc, D10 cc, volume-based …

Ai-Driven Segmentation And Volumetric Response Modeling Of Liver Regions To Radiotherapy, Aashish Chandra Gupta

Dissertations and Theses (Open Access)

In liver-directed radiotherapy (RT), liver regions receiving higher doses typically undergo atrophy while contralateral/adjacent lower-dose regions may exhibit compensatory hypertrophy through regeneration of healthy tissue. Optimizing the RT plan to promote regional hypertrophy while minimizing the risk of developing atrophy has the potential to enhance post-RT liver function and long-term survivorship. However, current clinical practice largely relies on global liver dose-volume metrics during RT-planning, which may obscure favorable dose-response correlation and limit actionable guidance for clinicians. Therefore, we hypothesized that post-RT regional liver response is governed by a combination of region-specific dose-volume and patient clinical features, and that these responses …

Craniospinal Irradiation Volumetric Modulated Arc Therapy (Vmat) Planning: A Dosimetric Contrast Utilizing Anterior Avoidance Sectors, Ashleigh M. Sammataro

Masters Projects

Purpose: Craniospinal irradiation (CSI) is essential for treating pediatric and adult central nervous system malignancies, yet it exposes large volumes of normal tissue to low‑dose radiation, contributing to significant long‑term toxicity. This study evaluated whether incorporating anterior‑avoidance sectors (AVD) into volumetric modulated arc therapy (VMAT) planning would improve normal tissue sparing while maintaining target coverage and plan quality.

Materials and Methods: 8 previously treated CSI patients were retrospectively replanned using two VMAT techniques: Full Arc and AVD. All patients were simulated supine with standardized immobilization and planned in Eclipse. Identical target volumes, optimization structures, and planning objectives were used for …

Study On The Accuracy Of Varian Eclipse Mlc Modeling When Mlcs Are Open Beyond The Jaw In Breast Cancer Patient Planning Using Aaa And Acuros With Both Dual-Isocentric Technique And Mono-Isocentric Technique., Amy Rogers

Masters Projects

Accurate dose delivery at the chest wall-supraclavicular (CW-SCV) junction remains an important challenge in breast irradiation, especially when multileaf collimator (MLC) leaves are intentionally opened beyond the collimator jaws to improve junction coverage. This study evaluated the dosimetric accuracy of the Varian Eclipse treatment planning system (TPS) at the CW-SCV junction using the Anisotropic Analytical Algorithm (AAA) and Acuros XB calculation algorithms with mono-isocentric and dual-isocentric treatment techniques. A prospective phantom-based study was performed using a solid water phantom and a Varian TrueBeam linear accelerator. Twenty-four unique three-dimensional conformal treatment plan configurations were created using combinations of beam energy (6 …

Automated Analysis Of Radiation Oncology Incident Reports Using Large Language Models, Nathan A. Dobranski

LSU Master's Theses

Patient safety incident reporting in radiation oncology requires expert analysis that is time-intensive and subject to variability. This thesis presents the development and technical validation of a locally deployed large language model (LLM) system for automated incident report analysis across multiple cancer centers. The system was designed for automated summarization and taxonomy assignment of Radiation Oncology Incident Learning System (RO-ILS) reports, operating entirely on local infrastructure to preserve patient privacy. A two-round, multi-rater evaluation methodology was employed, incorporating 600 total expert evaluations from two academic cancer centers. Round 1 established baseline performance using Mistral 7B and Mixtral 8x7B models with …

A Framework For Digital Energy Modulation And Translation In Projectional X-Ray Imaging, Richard R. Wargo

Theses and Dissertations

In projectional X-ray imaging, acquisition energy fundamentally influences subject contrast, image noise, and radiation dose. While dual-energy techniques exploit spectral differences to optimize contrast and enable material separation, acquiring multiple images of the same anatomy often requires additional exposures and increased system complexity.

This dissertation presents a framework for digital energy modulation (DEM), in which computational models are trained to translate projection images between energy domains without requiring additional X-ray acquisitions. DEM is conceived as a generalizable strategy for controlled contrast modulation in projection imaging, with potential applications in image optimization, radiation therapy alignment, and dual-energy applications.

The framework was …

Implementation Of Tg-351 Reference Dosimetry For A 6 Mv Photon Beam In An Mr-Guided Radiotherapy System, Nicholas A. Castellano Jr.

Theses and Dissertations

Magnetic resonance guided radiation therapy (MRgRT) combines magnetic resonance imaging (MRI) and radiation therapy to enable the visualization of anatomy in real time during treatment. The presence of a magnetic field in MRgRT affects charged particle radiation and detector responses, necessitating changes to traditional reference dosimetry procedures. The American Association of Physicists in Medicine (AAPM) Task Group 351 (TG-351) provides a formalism for reference dosimetry in MRgRT. In this study, the TG 351 formalism is used to perform reference dosimetry for a 6 MV flattening filter-free (FFF) photon beam from a Viewray MRIdian MR-Linac radiation therapy system. Beam quality determination, …

Practical Real-Time Permanent Magnet Energy Spectrometer Using A Diode Array For Therapeutic Electron Beam Tuning And Quality Assurance, Mason W. Heath

LSU Doctoral Dissertations

Purpose: Develop a practical, real-time permanent magnet electron energy spectrometer and evaluate it for beam tuning and quality assurance (QA) of therapeutic electron beams.

Methods: Aim 1: A 0.55 T permanent magnet was coupled to Sun Nuclear SRS MapCHECK® PC boards, providing two interlaced diode arrays. Detector response, R_meas(z_diode) versus diode position z_diode, was extracted from raw diode array readings, correcting for diode sensitivity and other factors. Using Monte Carlo (MC) computed, monoenergetic detector response functions, a curve-fitting algorithm extracted the energy spectrum, from R_meas(z_diode). The energy spectra for 7-20 …

Optimizing Palliative Spine Radiation: A Dosimetric Comparison Of Hybrid Arc Therapy And Conventional Appa Techniques, Alaina Vaneaton

Masters Projects

This study aimed to evaluate the dosimetric impact of Hybrid Arc Palliative Radiation Therapy (HART) versus conventional anterior-posterior/posterior-anterior (APPA) beam arrangements for thoracic spine metastases. The primary objective was to assess differences in conformity, homogeneity, and organ-at-risk (OAR) sparing between the two techniques. A retrospective plan comparison was conducted using anonymized datasets from twenty patients previously treated with HART. Each case was replanned using a standard APPA technique, normalized to match the target coverage of the original HART plan within 0.1%. All plans were prescribed 20 Gy in 5 fractions. Plan quality was evaluated using conformity index (CI), homogeneity index …

Enhancing Target Dose Conformity While Effectively Sparing The Spinal Cord In Proton Arc Treatment Plans For Cervical Chordomas And Chondrosarcomas, Jon Blalock

Masters Projects

Cervical spinal chordomas and chondrosarcomas present significant therapeutic challenges due to their proximity to the spinal cord and resistance to conventional radiotherapy. This retrospective study investigated the capability of proton arc therapy (PAT) to maintain or improve adequate target coverage while reducing dose to the spinal cord for cervical spinal chordomas and chondrosarcomas over standard fixed beam intensity modulated proton therapy (IMPT). While both IMPT and PAT use pencil beam scanning (PBS) to with energy modulation to deliver dose in discrete layers, IMPT relies on a limited number of fixed beam angles, whereas PAT delivers dose over an arc trajectory. …

Comparison Of Left Breast Accelerated Partial Breast Irradiation Plans: Flattening Filter Free Vmat Vs. Standard Vmat In Deep Inspiration Breath Hold And Free Breathing Techniques, Monica Albeck

Masters Projects

This retrospective planning study compared dosimetric outcomes and treatment efficiency between flattening filter free (FFF) and standard volumetric modulated arc therapy (VMAT) plans for left breast accelerated partial breast irradiation (APBI) under deep inspiration breath hold (DIBH) and free-breathing (FB) conditions. Ten patients with early stage left breast cancer were replanned to create four plans each: FFF VMAT and standard VMAT in DIBH and FB. All plans prescribed 30 Gy in 5 fractions. Measures included planning target volume (PTV) coverage, mean heart dose, ipsilateral lung V30%, contralateral breast maximum dose, and monitor units (MUs). Statistical analysis used repeated-measures ANOVA with …

Evaluating Dosimetric Outcomes In A Prostate Rapid Plan Model: A Comparison Of Prostate Treatment Plans With And Without Standardized Planning Structures, Erica Wartman

Masters Projects

Abstract

Knowledge-based planning (KBP) using RapidPlan (RP) has demonstrated the ability to produce high quality radiation therapy treatment plans while reducing time. This study evaluated whether the inclusion of department specific standardized planning structures, including rings and other optimization tools, improves plan quality when using a prostate and lymph node RP model, or if the model alone is sufficient to provide a quality plan without the use of these additional planning structures.

Ten previously treated Prostate+LN patients were replanned using the departmental RP model in Varian Eclipse treatment planning system.1 For each patient, two plans were created, one with standardized …

Evaluating Parotid Gland Dose Between Electronic Tissue Compensation And Field In Field Treatment Techniques For Parotid Sparing In Whole-Brain Radiotherapy, Joesph E. Bodgonas

Masters Projects

Purpose:

The parotid glands are essential to salivary function and patient quality of life, yet they are not routinely prioritized as organs at risk (OARs) during whole-brain radiotherapy (WBRT). With growing recognition of long-term side effects like xerostomia in patients with prolonged survival after WBRT, parotid-sparing techniques warrant investigation. This study compares radiation dose to the parotid glands using three different 3D conformal WBRT planning approaches: field-in-field (FiF) with blocking, electronic tissue compensation (eCOMP) without blocking, and eCOMP with blocking.

Methods and Materials:

A retrospective study was conducted on 20 patients previously treated with 3D conformal WBRT. Original eCOMP plans …

A Comparative Study Of Vmat Beam Arrangements In Large Field Nodal Prostate Treatment Plans, Laura R. Black

Masters Projects

Treatment of extensive prostate and pelvic lymph node volumes for prostate cancer patients provide unique challenges related to limitations in multileaf collimator (MLC) design in many modern linear accelerators. A strategy to overcome this challenge is by restricting the field size, improving modulation as well as using overlapping arcs to ensure complete coverage of the target. Using too few arcs can result in suboptimal target coverage, while too many arcs can lead to prolonged time on the table, increasing the risk of patient movement and potential side effects that may compromise treatment accuracy. This study aims to evaluate the optimal …

Evaluating Coplanar And Noncoplanar Treatment Plans For The Varian Halcyon And Varian Truebeam For Intact Prostate Patients., Ashley Coppage

Masters Projects

Prostate cancer is among the most treated malignancies with radiation therapy, where precise dose delivery is critical for tumor control and minimizing toxicity. VMAT is widely adopted due to its efficiency and conformity; however, the choice between coplanar and non-coplanar beam arrangements remains an area of ongoing investigation, especially with newer platforms like Halcyon and TrueBeam. This retrospective dosimetric study compares coplanar and non-coplanar volumetric modulated arc therapy (VMAT) treatment plans for intact prostate cancer patients using the Varian Halcyon and Varian TrueBeam systems. Plans were created using a standardized protocol within Eclipse v16.1, with all Halcyon plans employing coplanar …

Dosimetric Comparisons Of 6mv, 6fff, 10mv, And 10fff On Vmat Planning In Patients With Endometrial Cancer, Madisin M. Depas

Masters Projects

Purpose: This study aimed to evaluate the dosimetric and efficiency impacts of different photon beam energies—6MV, 6 flattening filter free (FFF), 10MV, and 10FFF—on volumetric modulated arc therapy (VMAT) plans for endometrial cancer, with attention to target coverage, organ at risk (OAR) sparing, and treatment efficiency.

Methods: A retrospective analysis was conducted on 25 patients with post-hysterectomy endometrial cancer. Each patient received four VMAT plans with varying energies. Planning metrics assessed included planning target volume (PTV) dose maximum (Dmax), conformity index (CI), heterogeneity index (HI), OAR doses (bladder, bowel, rectum), and total monitor units (MU). Correlations were drawn …

Dosimetric Effects Of Pinnacle³ Version 18.0 Advanced Auto-Planning Settings In Oropharyngeal Vmat Optimization, Emily Sanden

Masters Projects

This study evaluated the impact of Pinnacle³ version 18.0 auto-planning advanced settings modulation amount, monitor unit (MU) level, and dose fall-off priority on volumetric modulated arc therapy (VMAT) plan quality for bilateral oropharyngeal cancer. A total of 64 plans were generated using all possible combinations of low, medium, high, and very high settings for each parameter. A standardized base of tongue case was optimized once per plan using a single-time point approach, with planned target volume 1 (PTV1) (6996 cGy) and planned target volume 2 (PTV2) (5412 cGy) coverage evaluated. Each parotid gland, the spinal cord, brainstem, and the oral …

Impact Of Prostate Volume On Dose Fall-Off And Organ-At-Risk Exposure In Vmat For Prostate Cancer, Zhikang Jiang

Masters Projects

Prostate cancer remains one of the most prevalent malignancies among men, with radiotherapy, particularly VMAT—playing a central role in its management. VMAT allows for highly conformal dose delivery, but treatment planning must strike a careful balance between achieving steep dose gradients around the prostate and minimizing radiation exposure to nearby organs at risk (OARs), such as the bladder and rectum. This study aimed to evaluate how prostate volume influences dose fall-off characteristics and OAR dose exposure in VMAT treatment plans, providing insights into optimizing radiotherapy for patients with varying prostate sizes. A retrospective analysis was conducted on 50 prostate cancer …

Comparing Dosimetric Outcomes Of Static Imrt And Vmat In Accelerated Partial Breast Irradiation For Medially Located, Left-Sided Tumor Beds, Rani Jamil

Masters Projects

Abstract

Introduction: Accelerated partial breast irradiation (APBI) has emerged as a targeted alternative to whole-breast irradiation for early-stage breast cancer, particularly for patients with medially located, left-sided tumors. Static intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) offer advanced dose conformity, yet no direct comparisons between static IMRT and VMAT have been conducted specifically for medially located, left-sided APBI, a uniquely challenging anatomical subgroup. This study evaluates dosimetric differences between static IMRT and VMAT plans to determine which modality provides superior target coverage and organ-at-risk (OAR) sparing in left-sided APBI.

Methods: Ten patients with medially located left-sided breast …

Dosimetric Comparisons For Determining Optimal Arc Geometry In Multi Target Thoracic Vmat Sbrt Treatment Plans For Patients With Locally Advanced Inoperable Nsclc, Alexandrea M. Reeves

Masters Projects

Non-coplanar beam arrangements have been used for many years in radiation treatment planning. Their use has been known to show an increase in target conformity and gradient index. However, by using non-coplanar beam arrangements, the treatment planning time as well as the treatment delivery time can increase. Despite the increase in treatment planning and delivery complexity and time, previous studies have shown a decrease in OAR doses resulting in a desire to use non-coplanar beams. Previous studies have looked at various body sites and target locations, though no research has been found specifically studying non-coplanar beam arrangement in multi-target treatment …

Comparing And Evaluating Contralateral Breast Dose Relative To Median Ptv Tumor Bed Dose For Hypo-Fractionated Breast Treatments Using Import High Dose Constraints., Shannon J. Nordby

Masters Projects

This study is aimed to compare two different planning constraints for post-lumpectomy whole breast radiation treatments to evaluate whether or not the mean dose to the contralateral breast can be significantly reduced while maintaining plan quality for treatment. A total of 10 patients who had first undergone a lumpectomy were included into this study. Each patient’s initial treatment plan was created using a conventional approach with a mean dose constraint of < 600 cGy (Plan A) and then was replanned using the Import High protocol of a mean dose constraint, aiming to further push for a mean dose < 150 cGy (Plan B) to the contralateral breast. Both of these plans were analyzed for PTV coverage and dose to the surrounding critical structures. The results have shown that the contralateral mean dose was significantly reduced from an average of 216.32 in Plan A to 126.53 cGy in Plan B. All while meeting the target coverage of > 95% isodose line. Statistical testing showed a significant difference between the two planning techniques of lowering the contralateral dose (p < 0.0001), and normality testing supported the validity of the data analysis. In addition to a substantial dose reduction to the contralateral breast, Plan B maintained equal or improved dose constraint to other surrounding critical organs at risk, including the heart, lungs, spinal cord, and thyroid. The Import High protocol demonstrated consistent outcomes across diverse patient anatomies. These findings suggest that by using the Import High mean dose constraint, it is possible to maintain plan quality while reducing dose to the contralateral breast. This approach may help reduce the risk of long-term side effects and improve the patient’s overall outcomes in whole breast radiation treatments.