bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐J‐155: Learning Based Tumor Motion Tracking in MV Images Using Cone‐Beam CT Projections
Authors: Yue Y , Mamon H , Berbeco R 
Published: November 2011

Purpose: Tumor motion tracking in liver stereotactic body radiation therapy (SBRT) is highly desirable for improvement of treatment accuracy, dose conformity and sparing of healthy tissue. On‐board megavoltage (MV) x‐ray imaging has unique advantages for assessment of tumor location during treatment. This work proposes a novel method to track tumor motion in MV images using cone‐beam CT (CBCT) projections as prior knowledge. Methods: The learning based tumor tracking method consists of main two steps. First, a prior of 3D tumor motion is estimated from CBCT projections. Relying on the detection of implanted kV fiducials, the tumor motion trajectory is constructed along the CBCT projection angles. 3D tumor locations are then reconstructed from the trajectory. Further, a prior for tumor motion in EPID images are generated by projecting 3D motion on the MV imager plane. Second, tracking is carried out in an incremental learning framework, which adapts the sequential tracking knowledge into current estimation. The prior knowledge of tumor motion obtained in the first step is therefore integrated into estimation. For robust real‐time tracking, the algorithm is implemented by a sequential incremental update technique. Results: Patient data acquired from a liver SBRT treatment is used to validate our algorithm. Half‐fan CBCT projections acquired in three fractions were used to estimate 3D tumor motion. A total of 700 EPID images were analyzed for tumor tracking. All results were evaluated by clinician‐defined tumor positions and manual tumor tracks. The average root mean square error for tumor tracking is 0.89 ± 0.21 mm. Conclusions: A novel learning based tracking algorithm has been developed for tumor tracking in MV images. With the fast incremental online updating technique, our algorithm is well suited for real‐time tumor tracking and in‐treatment applications.Varian Medical Systems, Inc.
SU‐E‐J‐159: Correlation of Respiration‐Induced Motion of an External Surrogate and Implanted Internal Markers
Authors: Lu J , Brackbill E , Zheng D , Weiss E , Hugo G , Keall P , Poulsen P , Fledelius W , Williamson J 
Published: November 2011

Purpose: To investigate the correlation between the respiratory motion of implanted internal markers (IM) and external RPM traces for lung cancer patients in dynamic imaging. Methods: Under an IRB‐approved research protocol, 3 patients with VISICOIL marker (10 mm long) implants near/in their lung tumor were scanned with a daily single‐slow gantry rotation arc 4D‐CBCT acquisition. The Varian Real‐time Position Management system (RPM) was used as an external respiratory motion surrogate, with the marker block placed on the patient abdominal surface near the diaphragm. The IM motion was segmented in all 2D projections with an in‐house built Matlab program. The positions in the 3D spatial domain of the markers were extracted to (LR: left‐right, CC: cranial‐caudal, AP: anterior‐posterior). A Pearson‐type auto‐correlation function of the RPM AP trace and cross‐ correlation functions between RPM AP motion and the IM motions in three orthogonal directions was used to analyze the time series. Results: Our data shows that there is a strong positive correlation between the RPM AP motion and the IM motion in the CC direction. The correlation between the external motion and the IM motions in LR and AP directions varied from fraction to fraction. In addition, phase shift is observed in LR and AP directions. Different implanted markers in the same patient presented the very similar correlations, especially in the CC direction. This result suggests that multiple implanted markers can be used to provide supplementary information of the tumor motion. When the patient coughs during their respiratory cycle, internal motion and external motion may become uncorrelated. Conclusions: The RPM respiratory trace provides a good surrogate of the internal respiratory motion in the CC direction when the patient maintains a normal breathing pattern.Supported by NIH grant P01 CA 116602.
SU‐E‐J‐162: Tomotherapy Real‐Time Tumor Tracking: An Innovative Method for Magnetic Tracking in Enclosed Bores
Authors: McGary J , Chen J , Zubiao X 
Published: November 2011

Purpose: Real‐time tumor tracking for Tomotherapy systems is a problem in need of a solution. Currently, magnetic tracking systems, such as Calypso, are unable to localize a magnetic source due to the conducting bore. Eddy currents generated in response to the source create additional magnetic fields, at the source frequency, that are difficult to model and filter from the signal. Therefore, we are presenting an innovative method to solve this problem. Method: We have developed a localization algorithm based on a transponder source within a conducting cylinder, and a cost effective sensor configuration. The algorithm uses magnetic field gradients, as well as the magnetic fields, to effectively filter magnetic fields generated from surrounding eddy currents induced along the gantry. Solution accuracy depends on the sensor geometry and configuration; and therefore, the method is a combination of algorithm and sensor parameters to maximize accuracy, while minimizing cost to create a practical system. We modeled the gantry and transponder system to simulate the magnetic fields throughout the environment. The sensor fields were used as algorithm input to calculate the transponder location. The location of the transponder was compared with the calculation. Results: We investigated different algorithms, sensor geometry, and sensor configuration. We compared our method to traditional localization methods of Wilson, Nara, Chao, Hashi, and McGary. Those methods were unable to attain suitable clinical treatment accuracy due to the conducting bore. The method presented here was able to locate the transponder within 1–2 mm over a large extent of possible transponder positions and orientations. In certain regions, the localization error increased to about 3–4 mm due to the nearby eddy currents. Conclusions: The method, algorithm and sensor design, is capable of locating a transponder, for real‐time tumor tracking, in a modeled Tomotherapy gantry bore within 2–4 mm.Financial support from Tomotherapy, Inc. was provided, in part, to fund some of the research presented here. Other support came from the Golfers Against Cancer.
SU‐E‐T‐21: Repair of DNA Damage from Ionizing Radiation in the Range of Doses Experienced in CT Studies
Authors: Saxon S , McNitt‐Gray M , Ruehm S , Iwamoto K 
Published: November 2011

Purpose: To quantify the kinetics of the cellular response to low, CT‐relevant doses of ionizing radiation (IR) in U87MG human glioblastoma multiforme cancer cells in vitro. Method and Materials:U87MG cells were irradiated with 0Gy (controls), 20mGy (in typical CT range), or 2Gy (exceeding CT dose range) using an X‐ray cabinet irradiator at 150kVp. The cellular kinetics of DNA damage and response were quantified by flow cytometric quantitation of &#61543;H2AX foci at two time points (1hr and 6hrs post‐IR); using flow cytometry allows a much higher throughput than conventional methods. An auto‐fluorescence control was performed for each sample. Collected flow cytometry data, corrected for debris and dead cells using side and forward scatter gating, were analyzed with CellQuest Pro Software. Fluorescence histograms were generated for each sample and the respective auto‐fluorescence histogram was subtracted from each. The percentage of gated cells staining positive for &#61543;H2AX (beyond an a priori threshold based on the IgG negative control) was determined. Results: In cells exposed to 2Gy, &#61543;H2AX substantially increased within 1h and returned to control levels 6h post‐irradiation. In contrast, although cells exposed to 20mGy showed a measureable increase in &#61543;H2AX formation within 1h, there was no significant decrease 6h later. Conclusion: Our results suggest DNA damage induced by low, CT‐relevant doses is repaired at a slower rate than damage induced by higher doses. This altered kinetic response could have marked biological effects for current radio‐diagnostic procedures. Our study, therefore, underscores the importance of understanding the different repair mechanisms at different dose regions in order to accurately assess risk estimates and biological dose. Future work will investigate longer observation times to assess DNA repair in more detail in the current cell model as well as in normal lymphocyte cell lines.This work is partially supported by a SIEMENS Corporation research grant.
SU‐E‐T‐23: Ontological Representation of Radiation Treatment Guidelines
Authors: Ge Y , Minta T , Kirkpatrick J , Yuan L , Wu Q 
Published: November 2011

Purpose: To develop a Radiation Treatment Guidelines Ontology (RTGO) that represents the concepts, knowledge, and guidelines in radiation therapy using a formal and computable framework. This ontology will serve as the foundation of a decision support system for radiation oncologists. Method and Materials: The ontology framework chosen to represent RTGO is the Web Ontology Language (OWL) (www.w3.org/TR/owl‐guide). The OWL is rooted in the rigorous foundation of Description Logic and represents the latest development in ontology languages. The Protégé‐OWL ontology editor and knowledge‐base framework (http://protégé.stanford.edu) is used to build the ontology. The ontology is developed in a multi‐layered, modular, and iterative fashion. Upper ontologies are used to provide a sound structure. Concepts from standard ontologies are adopted whenever possible. Salient concepts and relationships are incorporated into the ontology through multiple iterations of extraction, modeling, implementation, and evaluation. Each iteration examines increasingly detailed concepts and relationships. The concepts are asserted in a strict subsumption hierarchy and are carefully formulated to be at a proper level of abstraction consistent with anticipated questions addressed by the ontology. Major ontology resources used in this project include National Center Biomedical Ontologyˈs Bioportal (bioportal.bioontology.org) and National Library of Medicineˈs Universal Medical Language System (UMLS) (www.nlm.nih.gov/research/umls). Major ontologies consulted include FMA for anatomical concepts, SNOMED for clinical findings and symptoms, and Semantic Network for relationships. Results: The initial focus is on modeling the concepts and knowledge summarized in the Quantitative Analysis of Normal Tissue Effects in the Clinic (QUANTEC) papers. Starting with the organ specific papers on bladder and rectum, the ontology has so far captured 171 concepts, 80 relationships, and 21 individuals. The development is proceeding to include other organs in the QUANTEC literature. Conclusion: Early results demonstrate that major concepts in QUANTEC papers regarding dose volume effects can be successfully captured in an ontological framework.Duke University has a Master Research Agreement with Varian Medical Systems, INC.
SU‐E‐T‐27: An Ontology‐Based Framework for Radiation Oncology Patient Management
Authors: McShan D , Kessler M , Fraass B 
Published: November 2011

Purpose: To describe the benefits of the use of an ontology (a semantic description of concepts, properties, and relationships) as the base of a data management system which provides the (often missing) connecting information regarding goals and process used for patient management. Method and Material: The ontology has been defined with an OWL ontology model using Protégé and Oracle. The ontology database consists of the ontology model and the instances (actual data). Supporting code which forms the distributed components is written in Java, C, C++,and Fortran. Messaging between components uses an open‐source AMQP broker. To retrieve and update data, SPARQL queries are messaged to the ontology access components. Results: Initial ontology construction has been based on standard and departmental concepts. Guidelines used include making the ontology of sufficient (and extensible) scope to tie together key concepts with enough depth to be useful for study retrieval (queries), and with enough attribution to identify related source material (files, URLs, other databases, PACS…) when additional detail is desired. Integration of this new knowledge‐modeling mechanism into our clinical/research infrastructure framework is underway. Current efforts focus on modeling and implementing more sophisticated management of planning and delivery for adaptive therapies based on biomarker assessments that identify or predict changed response to the dose received during treatment. In these complex protocols, treatment plans must be organized by treatment directives that specify treatment goals, must include detailed knowledge of prior treatment, and manage all new patient‐specific data acquired during the treatment course. Conclusions: An ontology‐based knowledge base has been developed as the information framework of a new treatment planning and workflow management system. This ontology provides the extensible means to describe and manage highly complex adaptive treatment protocols for unique and advanced clinical studies.Supported in part by NIH grant CA‐P01‐59827
SU‐E‐T‐28: Task Tracking and Messaging for Workflow Optimization of Treatment Planning Process
Authors: Kantor M , Kanke J , Dong L 
Published: November 2011

Purpose: The entire radiotherapy treatment planning process, from simulation, target definition, planning, to treatment, requires a collaborative effort from a multidisciplinary team of highly specialized professionals. Although treatment planning is a highly sequential process for an individual patient, professionals are consistently multi‐tasking to support on‐going patient care activities. As a result, treatment planning is a lengthy process, which often results in delay of new treatment start or poor quality treatment plans. Methods: To improve accountability and optimize workflow, a novel electronic messaging solution using event triggering and automatic information processing was designed to improve the effectiveness of collaboration among different professionals for treatment planning. In order to reduce the burden of data entry, we have made efforts to develop software interfaces to other clinical systems, such as the electronic medical record (EMR), integrated scripts executed in the planning system, or Active Directory to obtain plannerˈs information. Professionals receive e‐notice from the system immediately following the completion of the previous step. Results: In our initial deployment of the system clinical wide, the system tracked 2500 planning assignments in the main campus and regional cancer centers with 50+ practicing radiation oncologists and approximately equal numbers of dosimetrists and physicists. The system provided an electronic media to communicate with physicians, dosimetrists, and physicists to improve communication on prescription, dose tolerance, or just simply the timeline for the planning activities. The average simulation‐to‐treatment start time was 3 business days in 50% patients, but IMRT took extra 2 business days to complete. IMRT contouring was completed in one business day in 72% of patients. Workflow bottleneck was identified in certain services for which dominant Monday new starts and rushed plans on Friday were observed. Conclusions: We designed a novel workflow enhancement tool to assist collaboration and process improvement.Research partially supported by Philips Medical Systems
SU‐E‐T‐34: Time Series Analysis of Skin Reactions during Heck and Neck IMRT
Authors: Glennie D , Doerwald‐Munoz L , Ostapiak O , Patterson M , Hayward J , Farrell T 
Published: November 2011

Purpose: To quantitatively characterize the time sequence of skin erythema in head and neck patients undergoing intensity modulated radiation therapy (IMRT) treatments using optical reflectance spectroscopy. The overall goal is to identify patients who will develop extreme skin responses earlier than is possible by visual inspection alone. Methods: Ten (10) patients undergoing IMRT for the treatment of head and neck cancers were followed throughout the course of their intervention. Daily spectral skin reflectance measurements were made in order to track changes in the tissue optical properties. Weekly thermoluminescent detector (TLD) readings were performed in the measurement area to verify the dose calculated by the treatment planning system. Patients also completed a weekly questionnaire on factors that may have affected their skin reaction, and were visually inspected by a radiation oncologist.Results: The data were fit by a 2‐component principle component analysis (PCA) model. The preliminary results show that absorbed dose is the largest contributor to changes in the spectral reflectance and that those changes are seen primarily at wavelengths above 600 nm. Differences among patient skin responses were seen and accounted for in the model Conclusions: The PCA model indicates that it may be possible to predict a patientˈs spectral skin reflectance measurement on the final day of treatment given an initial spectrum and the dose. Therefore, further analysis of the data may yield a method of determining patient reactions before visible signs are detected.Partial funding through Varian, Inc. and the Natural Sciences and Engineering Research Council of Canada.
SU‐E‐T‐38: Validating the Use of a New Tumor Irradiation Quality Metric for Lung and Head and Neck Tumors: Total Clonogen Survival
Authors: Zuniga AA , Thorstad WL , Oh JH , Apte AP , Bradley JD , Deasy JO 
Published: November 2011

PURPOSE: Ideally, a single factor would allow objective ranking of dose distributions with respect to the probability of local control. The purpose of this work is to study the applicability of a new metric as a predictor of local control (LC) indicator in head and neck tumors and lung tumors. MATERIALS: Two datasets were used: (A) 80 head and neck (H&N) patients using IMRT, and (B) 56 non‐small cell lung cancer who received 3D conformal RT both treated at Washington University in Saint Louis at standard fractionation. 23 H&N and 22 lung patients failed locally. A simple model was used to derive the expectation value of the number of surviving clonogens per initial clonogen density (not initial number). Other dose‐volume parameters were compared to TCS. Correlation with LC for univariate and multivariate logistic models of the available parameters was assessed using the area under receiver operating characteristic curve (AUC) and Spearmanˈs rank correlation coefficient (Rs). We also tested bootstrap cross‐validation of the models. Results: Total Clonogen Survival was the most predictive variable on univariate analysis in both datasets using an optimal value of SF2=0.8 ((A) Rs=0.444 p‐value<0.0001 (B) Rs=0.441 p‐value<0.0001). In logistic regression for both datasets, all statistically significant multivariate models included TCS parameter. Multivariate logistic regression for (A) shows that a two parameter (TCS and stage_group) model was the most significant when cross‐validated (RsCV=0.4644, pCV‐value=0.02). Higher order models did not appear more predictive after cross‐validation. However, we report in an abstract at this meeting that machine learning using TCS can improve predictive power. Conclusions: TCS was shown to be a simple and useful parameter when predicting LC in these two datasets. It differs from cell‐kill based EUD by mechanistically accounting for tumor volume variation.Partially supported by NIH R01 grant CA85181.
SU‐E‐T‐110: Quantitative Image Based Measurement of Electron Beam Spot Position
Authors: Nyiri B , Smale J , Gerig L 
Published: November 2011

Purpose: Develop an image based method to measure electron beam spot position w.r.t the Collimator Axis Of Rotation (CAOR). Methods: Two stainless steel rods, 3 mm in diameter, are mounted in a jig attached to the linac collimator. The rods lay in different planes normal to the CAOR, one at 159 cm SSD and the other at 70 cm SSD, and are offset 10 and 6 cm from the CAOR respectively. Images of both rods are acquired at multiple coll rotations. At each angle the rods project a tangent to an inscribed circle, the centre of which is calculated. The lower rod is very close the plane of the EPID and the centre of its inscribed circle defines the mechanical CAOR. The centre of the inscribed circle calculated from multiple images of the upper rod will be displaced from the CAOR by some distance proportional to the distance the beam source is from the CAOR. Test measurements were performed on an Elekta 6 MV where the In Plane beam spot position was moved a known distance using steering fine and beam spot position was measured.Results: Independent beam spot measurement (Flexmap Image Registration ball bearing) reported the initial beam spot at 0.29 mm from CAOR, moving to 0.91 mm (delta =0.62 mm) with steering. The rod tests showed the initial beam spot to be .31 mm from the CAOR and 1.17 mm from CAOR after adjustment. Note that in our companion paper we report similar values (initial 0.13mm going to 0.92 mm and initial value of 0.09mm going to 0.79) with our two co‐rotational dosimetric beam spot tests Conclusions: A simple method for measuring beam spot position with respect to CAOR is described. It provides its own internal reference and could be incorporated into routine QA using the EPID.Jason Smale is an employee of Elekta Canada
SU‐E‐T‐125: VMAT Monthly Quality Assurance Using a 2D Ionization Chamber Array
Authors: Myers P , Buckey C , Mihailidis D , Mavroidis P , Esquivel C , Gutiérrez A , Papanikolaou N , Stathakis S 
Published: November 2011

Purpose: Periodic quality assurance is essential for the accurate and consistent operation of dynamic multileaf collimators (DMLC) for volume modulated arc therapy (VMAT). Varian RapidArc is a system for delivering VMAT that can vary gantry speed and dose rate as the DMLCs quickly change position in order to obtain a conformal dose. A more time efficient and reproducible method for verifying the RapidArc capabilities has been developed building upon previous work by Ling et. al. using a 2D ionization chamber array. Methods: The PTW seven29 2D‐ARRAY was used in conjunction with an isocentric gantry mount, removing directional dependence, to complete three tests. Tests included evaluating machine performance while varying dose rate and gantry speed, while varying DMLC speed and the dose rate, and DMLC position accuracy. Reproducibility of each test was also evaluated. Results: Dose rate (111–600 MU/min) and gantry speed (5.5–4.3 degrees/s) capability was studied with a RapidArc picket fence pattern consisting of 7 different sections of combinations and compared to a corresponding open field and was found to agree within 0.84%. DMLC speed (0.46, 0.92, 1.84, and 2.76 cm/s) evaluation was performed similarly and agreed within 3.66% (2.93–3.66%). A RapidArc picket fence was compared with a static gantry picket fence to evaluate DMLC position accuracy to within 2.91%. Reproducibility of each of the three RapidArc tests was found to be within 0.57%, 1.78%, and 2.70% respectively. Conclusions: The seven29 detector was able to perform the RapidArc quality assurance tests efficiently and accurately and the results were reproducible. Periodic verification of DMLC movement, dose rate variation, and gantry speed variation relating to RapidArc delivery can be completed in a timelier manner using this equipment.This work partially supported by PTW, Freiburg, Germany.