Radiation Medicine Commons^™

Commissioning And Validation Of A Monte Carlo Algorithm For Spine Stereotactic Radiosurgery, C Knill, R Sandhu, B Loughery, L Lin, R Halford, D Drake, M Snyder

Conference Presentation Abstracts

Purpose: A 6FFF Monte Carlo (MC) dose calculation algorithm was commissioned for spine stereotactic radiosurgery (SRS) planning on the Versa HD. Initial model generation, validation, and ensuing model tuning will be presented. Methods: The model was generated by the manufacturer, Brainlab, using both in-air and in-water commissioning measurements of field sizes between 6mm and 400mm on the Versa HD. Initial model validation was performed by simulating a water tank in the planning system, calculating commissioning fields, and comparing calculations to measured data. Model accuracy was quantified for output factors, PDDs, profile sizes, and profile penumbras. Nine previously treated Spine SRS …

Clinical Experience Of Exactrac To Guide Six Degree Of Freedom Fiducial Marker Based Patient Positioning For Hypo-Prostate Fractionation, R Sandhu, C Knill, B Loughery, L Lin, Z Seymour

Conference Presentation Abstracts

Purpose: ExacTrac is clinically used for inter- and intra- fraction shift corrections for hypofractionated prostate patients by registering to implanted fiducial markers. ExacTrac corrections for thirty-three prostate patients were collated and analyzed. Methods: ExacTrac shifts were exported for prostate patients (140 total fractions) who were treated with two 180° partial arcs with beam-on time less than 60seconds/arc. Prior to each treatment fraction, a cone beam computed tomography (CBCT) image was acquired to verify bladder and rectal filling against simulation. Following CBCT, ExacTrac was used for initial prostate localization and shifts were applied using a 6 degree-of-freedom (6D) couch. Following initial …

A Novel Simultaneous Plan Quality And Beam Delivery Time Sparc Optimization Platform Using Primal Dual Active Set With Continuation (Pdasc), Lewei Zhao, J You, Gang Liu, X Lu, Xuanfeng Ding

Conference Presentation Abstracts

Purpose: Proton arc is a new treatment modality that delivers proton beams while continuously rotating the gantry. This study proposed a regularized l0-minimization primal dual active set with continuation (PDASC) algorithm for proton arc spot sparsity optimization to simultaneously optimize the plan quality and the beam delivery time (BDT). Methods: Based on the previously published beam delivery sequence model of IBA ProteusONE®, proton treatment delivery time is actually dominated by spot switching time (SSWT). SSWT is approximately linearly dependent on spot numbers. So we used a non-convex l0-norm to control the sparsity level of the regularized solution. The clinical objective …

Validation And Implementation Of A Dedicated Spine Stereotactic Radiosurgery Treatment Planning System, C Knill, R Sandhu, B Loughery, L Lin, Z Seymour, P Chinnaiyan, T Quinn, M Almahariq, R Deraniyagala

Conference Presentation Abstracts

Purpose: A dedicated spine stereotactic radiosurgery optimization algorithm was commissioned for 6FFF Versa HD deliveries. Plan comparisons with the existing clinical optimization algorithm along with the dosimetric validation of the deliveries were investigated. Methods: Nine stereotactic spine patients, previously treated with Pinnacle generated plans, were re-optimized using Brainlab’s SRS spine planning Element. Three additional Elements plans were created for each patient: 1) initial optimization using a pencil beam calculation algorithm (PBC), 2) Monte Carlo (MC) recalculation of the PBC plan, and 3) re-optimization of the PBC plan using Monte Carlo. Patient dose from PBC plans was compared to MC recalculated …

A Team Learning Initiative In Undergraduate Medical Physics, B Loughery, J Mcbrady, M Joiner

Conference Presentation Abstracts

Purpose: To improve comprehension in traditionally difficult subjects for a senior-level undergraduate medical physics course, we designed and implemented a Team Learning technique. This work evaluates the translation of Team Learning to medical physics.  Methods: At the beginning of the term, students were sorted into 3 even teams (students/year = 14.5).  The class met twice weekly: a traditional lecture was taught first, and each team was assigned a specific 1/3 of the lecture material in which to specialize.  Each team was assigned to create a PowerPoint presentation on their material using outside references and without copying the original figures or …

Evaluation Of 4pi Arc Positioning For Cranial Vmat Srs In Elements, B Loughery, C Knill, R Sandhu, L Lin, Z Seymour

Conference Presentation Abstracts

Purpose: Brainlab’s Elements Cranial VMAT (CVMAT) v3.0 introduces a 4Pi optimization that includes automated gantry and couch positioning alongside collimator optimization. In contrast, v1.5 uses a fixed collimator angle and predefined templates for gantry and couch angles that are manually modified by the planner. This study evaluates the 4Pi generated plans for clinical acceptability in terms of plan quality and delivery accuracy on a VersaHD. Methods: We chose a recent sample of 9 clinical plans that represent our catalog of target locations, fractionation schemes, and target sizes. Cases were replanned in CVMAT v3.0 using 4Pi optimization. These plans were evaluated …

Does Lung Function Imaging Modality Have A Dosimetric Impact On Functional Avoidance Treatment Planning: Assessment Using Prospective Clinical Trial Data, J Belardo, S Zhang, E Castillo, R Castillo, C Rusthoven, B Jones, M Miften, T Guerrero, I Grills, Y Chen

Conference Presentation Abstracts

Purpose: Functional avoidance radiotherapy proposes to use functional imaging to design treatment plans that reduce doses to functional regions of lung. Prospective data has shown that reducing doses to functional lung results in reduced pulmonary toxicity. Various lung function imaging modalities have been proposed for functional avoidance; however, there have been no studies evaluating whether using different imaging modalities results in dosimetrically different functional avoidance plans. The purpose of this study was to quantify the differences in treatment plans as a function of lung function imaging modality. Methods: 25 lung cancer patients enrolled on a prospective trial underwent nuclear medicine …

A Novel Technique To Evaluate Skin Toxicity In Breast Cancer Radiotherapy, R Culcasi, M Vlachaki, M Snyder

Conference Presentation Abstracts

Purpose: To evaluate skin toxicity throughout breast radiotherapy by visualizing variations in Eulerian amplified microcirculation and correlating to skin temperature as measured by a thermal camera. Methods: High-resolution monochrome video recordings and thermal images were acquired for four breast cancer patients prior to radiation treatment followed weekly over 3-5 weeks. During these visits, the radiation oncologist assessed the patient’s skin following the CTCAE scoring system. Videos were amplified by a factor of 100 for frequencies near the patient's measured heart rate (as measured by a fingertip pulse oximeter) with a bandwidth of 0.2Hz, based on a technique developed by CSAIL …

Real-Time Tracking Diaphragm Motion On During-Treatment Kv Cone Beam Projection Images Using Resnet50, J Liang, Q Liu, E Porter, D Yan

Conference Presentation Abstracts

Purpose: Diaphragm manifested on Cone Beam projection image has been used as surrogate to monitor lung tumor position. We propose a deep learning method to detect diaphragm apex position of the ipsilateral lung in real-time on KV projections acquired during Lung SBRT delivery. Methods: 7 hypo-lung SBRT patients with right lower lobe tumor were selected in this retrospective study. The imaging projection angle ranges from about -270 to 112 degrees. The right lung diaphragm apex was manually labeled as ground-truth on KV projections acquired during-treatment sessions with 899±167 projections per session. The backbone of our machine learning model is 50 …

A Novel Ultra-High Dose Rate Proton Therapy Technology: Spot-Scanning Proton Arc Therapy Flash (Splash), Gang Liu, Lewei Zhao, Xiaoqiang Li, S Zhang, S Dai, X Lu, Xuanfeng Ding

Conference Presentation Abstracts

Purpose: The flash dose rate on the order of 40 Gy/s has the potential to spare normal tissue with iso-effective tumor growth delay. Meanwhile, the spot-scanning proton arc therapy(SPArc), demonstrated its superior dosimetric conformity and plan robustness compared to the conventional intensity modulated proton therapy(IMPT). To take the full advantage of flash dose rate and the high dose conformity, we introduce a novel optimization and delivery technique, SPArc FLASH (SPLASH). Methods: SPLASH framework was implemented in an open-source proton planning platform (matRad). It optimizes the spot moniter unit(MU) weighting and cyclotron beam current per spot simultaneously. More specifically, it simultaneously …

During-Treatment Imaging Feasibility For Intrafraction Stereotactic Spine Treatment Evaluations, M Liu, D Drake, D Lack, M Sigler, J Sliwinski, K Barton, D To, I Grills, J Liang

Conference Presentation Abstracts

Purpose: On Elekta linacs, cone-beam CTs (CBCT) can be acquired during VMAT delivery to monitor intrafraction motion during treatment. Stereotactic spine treatments can be lengthy, increasing patient motion likelihood during treatment. We evaluated during-treatment CBCT (DT-CBCT) feasibility to assess patient motion for stereotactic spine treatments in place of a mid-treatment CBCT. Methods: CBCTs from seven spine treatments were analyzed retrospectively. Various fractionation schemes were used (16-25Gy delivered in 1-5 fractions). All plans contained two VMAT arcs of 2209.5-13,332.4 MUs with treatment times of 7-58 minutes. Projections from pre-correction CBCTs were combined with post-correction CBCT to simulate patient motion (1cm, 2 …

Comparison Of Aperture Complexity Between Vmat Plans Using Conventionally Flattened (Ff) And Flattening-Filter-Free (Fff) Beams, Q Liu, J Liang

Conference Presentation Abstracts

Purpose: VMAT plans with high amount of complex apertures could lead to less confidence in dose calculation accuracy due to machine modelling and dose algorithm limitations. It was hypothesized that VMAT plans generated with FFF beams would result in more complex aperture shapes due to the non-flattened beam profile. The purpose of this study was to test this hypothesis by assessing various plan complexity metrics. Methods: Target and organ-at-risk structures were created on an anthropomorphic phantom in various sites: lung, prostate, spine, pancreas, breast, rectum and HN. Hypo-fractioned VMAT plans were generated using Elekta Agility MLC in Pinnacle TPS. Both …

Physics-Informed Machine Learning For Estimating Pulmonary Perfusion From Non-Contract 4dct, Y Liu, A Nowacki, R Castillo, Y Vinogradskiy, G Nair, C Stevens, E Castillo

Conference Presentation Abstracts

Purpose: Novel methods have been developed for functional avoidance that proposes to use 4DCT to derive lung ventilation and perfusion images. Previous methods for quantifying lung perfusion on non-contrast 4DCT rely either on HU-based physical models or black-box deep learning models. While deep learning typically achieves higher accuracies in image processing tasks, physical models provide a rationale for model predictions. The purpose of this study is to introduce a biophysics-informed machine learning method for estimating pulmonary perfusion from noncontrast 4DCT. Our approach is designed to combine the predictive power of neural networks with the interpretability of physical modeling, with the …

Quantifying Copd Disease Severity With Ct-Derived Perfusion Imaging, A Nowacki, G Nair, Y Liu, C J. Galban, C Stevens, E Castillo

Conference Presentation Abstracts

Purpose: CT-derived perfusion (CTP) is a novel image processing modality that quantifies pulmonary perfusion from non-contrast inhale/exhale CT image pairs. While existing imaging markers for COPD primarily depend on morphological features or HU thresholding, CTP provides a quantitative marker of blood flow and has been shown to identify disease progression prior to the appearance structural abnormalities. In this study, we assess the potential utility of CTP as a disease severity marker for COPD. Methods: CTP was computed from high-resolution inhale-exhale CT scans for 785 patients with a Global Initiative for Obstructive Lung Disease (GOLD) score ranging from 0 to 4 …

Per-Fraction Deviation In Logfile Parameters Reported In A Single Vmat Arc, M Snyder, D To, D Drake, J Liang, D Lack

Conference Presentation Abstracts

Purpose: Measurement-based QA identifies large deviations between planned and delivered dose, but subtle—yet clinically unacceptable—deviations can pass through the conventional QA process unnoticed. Incorporating logfilebased information into pre-treatment QA should result in more robust QA overall, provided such information is stable across the entire treatment course. We present here a case-study of logfile stability to investigate the potential of logfiles as useful adjuncts in the QA process. Methods: We analyzed logfiles from six fractions of a VMAT plan delivered on an Elekta Infinity linac with an Agility MLC. To simplify the analysis, we considered a single 52 control point VMAT …

Variation In Molecularly Defined Prostate Tumor Subtypes By Self-Identified Race, Kevin H. Kensler, H. Lee Moffitt Cancer Center And Research Institute, Mohamed Alshalalfa, Bruce J. Trock, Stephen J. Freedland, Michael R. Freeman, Sungyong You, Brandon A. Mahal, Robert Den, Adam Dicker, R. Jeffrey Karnes, Eric A. Klein, Priti Lal, Yang Liu, Elai Davicioni, Walter Rayford, Kosj Yamoah, Timothy R. Rebbeck

Department of Radiation Oncology Faculty Papers

Background: Socioeconomic and health care utilization factors are major drivers of prostate cancer (PC) mortality disparities in the USA; however, tumor molecular heterogeneity may also contribute to the higher mortality among Black men. Objective: To compare differences in PC subtype frequency and genomic aggressiveness by self-identified race. Design, setting, and participants: Five molecular subtype classifiers were applied for 426 Black and 762 White PC patients in the Decipher Genomics Resource Information Database (GRID). Outcome measurements and statistical analysis: Differences in subtype frequency and tumor genomic risk (Decipher score >0.6) by race were evaluated using χ2 tests and multivariable-adjusted logistic regression …

Financial Toxicity Tumor Board: A Multi-Disciplinary Team Activity Required In Low And Middle-Income Countries (Lmic), Ahmed Nadeem Abbasi, Sohail Rasool, Laraib Khan

Department of Radiation Oncology

No abstract provided.

In-Phantom Film Measurements Of Two Treatment Planning Systems For Single-Fraction Spine Sbrt, Michael J. Taylor

LSU Master's Theses

Purpose: Treatment planning accuracy for spine stereotactic body radiation therapy (SBRT) varies depending on the dose calculation algorithm utilized in the treatment planning system (TPS). This project compared the end-to-end accuracy between spine SBRT plans calculated in a convolution-superposition based TPS (TPS_CS) and Monte Carlo based TPS (TPS_MC) with radiochromic film measurements. The hypothesis was that TPS_MC would calculate the dose gradient in the critical region between the vertebral body and the spinal cord more accurately than TPS_CS.

Methods: Single-fraction spine SBRT treatments following RTOG 0631 and local institutional guidelines were planned in …

Functional Lung Segmentation From Computed Tomography Images Using Deep Learning, Duyen M. Quach, Evan Porter, Thomas M. Guerrero

Posters

INTRODUCTION
Functional avoidance treatment planning allows radiation oncologists to intentionally minimize radiation dose to higher-functioning lung areas while favoring radiation dose towards lower-functioning regions. This treatment planning method has been shown to reduce pulmonary toxicity for patients receiving radiation therapy. Functional lung information, traditionally ventilation or perfusion SPECT scans, is required to plan for functional avoidance.

The Prognostic Significance Of Glucose-6-Phosphate Dehydrogenase As A Biomarker In Head And Neck Squamous Cell Carcinomas Treated With Conventional Chemoradiation, Kenneth H. Barker, Barbara L. Pruetz, Jessica D. Arden, Thomas J. Quinn, George D. Wilson

Posters

INTRODUCTION
The prognosis of patients with head and neck squamous cell carcinoma (HNSCC) treated with chemoradiation can be predicted using p16 as a surrogate biomarker of Human Papilloma Virus (HPV) status, but a subset of patients continues to do poorly despite a positive or negative p16 status. This project attempted to identify another biomarker, glucose-6-phosphate dehydrogenase (G6PD) as a marker for prognosis in HNSCC patients. Radiation induces oxidative damage to destroy tumor cells, and G6PD is a key enzyme involved in protecting cells from oxidative damage. The goal of this project was to identify a prognostic biomarker that would aid …