bluuebunny/crossref_metadata_2025_split huggingface dataset:
TH‐AB‐BRB‐11: A Method of Unwrapping 3D Complex Hollow Organs for Spatial Dose Surface Analysis
Authors: Witztum A , Warren S , Partridge M , Hawkins M A 
Published: June 2015

Purpose:To describe and evaluate (on 15 duodena) a method of mapping 3D surface dose for hollow organs with complex geometry (duodenum) to a 2D plane. Methods have previously been presented for unwrapping tubular organs (oesophagus and rectum) for spatial modelling of toxicity. However, the complex geometry of the duodenum demands a new method for producing 2D surface dose maps (SDMs).Methods:The organ is defined by Delaunay triangulation and voxelised into a 0.085×0.085×0.085 cm3 binary image. This is thinned using a distance transform resulting in a cluster of points approximately down the organ centre. A subset of points is manually selected and a central axis spline (CAS) fit. The CAS is discretised into 30 points and a ray cast from each point (angular step 12°, axial step 0.05 cm) on the plane normal to the vector to the next CAS point and the dose at the closest perimeter point recorded. These perimeter slices are “unwrapped” from the edge distal to the pancreas so the high dose region (proximal to the tumour) falls in the centre of the dose map.Results:A complete methodology has been described that produces 2D SDMs for organs with simple or complex geometries. This method was successfully tested by extracting SDMs for 15 duodena, with one oesophagus illustrating application to simple geometries. Visual comparisons show that a 30×30 map provides sufficient resolution to view features of interest.Conclusion:A new method for unwrapping surface dose in complex hollow organs has been developed and tested on 15 duodenal cases. The method is robust, requires minimal human interaction, and has been shown to be generalisable to simpler geometries (oesophagus). The 2D dose maps produced provide spatial dose distribution information which will be explored to create models that may improve toxicity prediction in treatments for locally‐advanced pancreatic cancer.
TH‐AB‐BRB‐12: A Novel 2D Expansion Technique Based On Beam Geometry for Generating Margins
Authors: Tsang H , Kamerling CP , Nill S , Oelfke U 
Published: June 2015

Purpose:Current practice of using 3D margins in radiotherapy with high‐energy photon beams provides larger‐than‐required target coverage. Negligible dose changes for small CTV displacements in the beam direction allow for the design of 2D‐based CTV‐PTV margins. We investigate the impact of a novel 2D margin concept for prostate radiotherapy treatments.Methods:Our implementation of 2D margins follows van Herk's (2000) margin recipe by considering only geometrical uncertainties perpendicular to the incident beam direction. The union of all beam‐angle‐dependent expansions defines our PTV. Five prostate radiotherapy plans were generated using IMRT inverse planning following clinical protocols with a prescription of 74Gy in 37 fractions. Systematic uncertainties of 1.1, 1.1, 1.5mm in the LR, SI, and AP directions, respectively, and 0.9, 1.1, 1.0mm for the random uncertainties, were used. A verification tool was used to simulate the effects of systematic and random errors, using a population of 10,000 identical geometries. The fraction of the population that satisfies or violates a certain dose or volume constraint was used for comparison.Results:The median observed PTV volume reduction between the 3D and 2D margins is 7.85% (range, 7.14–8.29%). Using the verification tool, all CTVs had close to 100% of the population satisfying D98% > 95% of the prescribed dose. When applying the verification tool to analyse the rectal doses delivered, a median relative reduction of 1.05% (range, 0.66–6.17%) of the population was observed for D2% above 70Gy; similarly for D2% above 74Gy, a median relative reduction of 31.7% (range, 13.3–52.6%) was observed.Conclusion:We are able to ascertain sufficient dose coverage using our 2D margin concept for planning whilst lowering dose to nearby structures, though the amount of sparing depends largely on the patients’ anatomy. With the coverage observed using our novel technique, we believe additional room exists for sparing dose to target‐adjacent OARs.Research at The Institute of Cancer Research is supported by Cancer Research UK under Programme C33589/A19727. We acknowledge NHS funding to the NIHR Biomedical Research Centre at The Royal Marsden and The Institute of Cancer Research.
TH‐AB‐BRA‐03: Development of a Scintillation Dosimetry System Capable of Real‐Time Dosimetry During LDR Brachytherapy Seed Implant
Authors: Therriault‐Proulx F , Beaulieu L , Beddar S 
Published: June 2015

Purpose:To develop a scintillation dosimetry system with sufficient sensitivity for accurate dose measurements during low dose‐rate (LDR) brachytherapy, including single‐seed insertion.Methods:First, the impact of the energy dependence of plastic scintillation detectors (PSDs) was studied using GEANT4 Monte Carlo simulations adapted from the ALGEBRA source code for brachytherapy. The photon energy spectrum was obtained in water around an I‐125 brachytherapy seed and convoluted to a detector response. Secondly, because low dose rate results in a corresponding low light emission, another part of this study focused on optimizing the choice of each component of the system to enhance the signal‐to‐noise ratio. A novel motorized and automated PSD positioning device mounted to a water tank was also developed to minimize uncertainties. Measurements of 15s were performed for distances from 1 cm to 7 cm in different radial and longitudinal directions and compared to the expected values.Results:Even though the photon energy spectrum around the I‐125 source was shown to vary considerably, the effect on dose measurement accuracy was minor (<1%). This holds true as long as the PSD is calibrated using the same brachytherapy isotope. The different components of the PSD probe did not show a significant effect on the calculated spectrum (<0.1%). Proper selection of photodetector and optical components helped improving by over 35X the signal‐to‐noise ratio. The measurements agreed with the expected values in all conditions. The PSD system was shown capable of detecting source misplacements for all clinically relevant conditions of measurement.Conclusion:The system developed in this study allows for accurate dose measurements around an I‐125 seed and could therefore provide valuable information in real‐time during LDR brachytherapy seed implant.Part of this research was supported by the Odyssey Program at The University of Texas MD Anderson Cancer Center.
TH‐AB‐BRA‐04: A Physical Phantom for Experimental Commissioning and Performance Testing of 192Ir MBDCAs
Authors: Pappas E , Moutsatsos A , Zoros E , Peppa V , Zourari K , Karaiskos P , Papagiannis P 
Published: June 2015

Purpose:To present a phantom‐based methodology for the experimental commissioning and performance testing of model‐based dose calculation algorithms (MBDCAs), which have been recently introduced in 192Ir HDR brachytherapy treatment planning systems (TPSs).Methods:The phantom was constructed from PMMA slabs properly machined to accommodate material and density inhomogeneity inserts, as well as TLD detectors (TLD‐100, 1×1×1 mm3), radiochromic films (Gafchromic EBT‐3) and a cylindrical Presage dosimeter (d=6cm, h=8cm). The spatial arrangement of the different dosimeters within the phantom permitted measurements at regions of scatter conditions departing from TG43 assumptions (e.g., at phantom boundary) and/or close to the inhomogeneity inserts. The phantom was CT‐imaged and a multiple 192Ir source position treatment plan was prepared using the Oncentra Brachy v4.5 TPS. Dose calculations of the Oncentra‐ACE MBDCA were exported in DICOM‐RT for further evaluation. The plan was delivered using a microSelectron v.2 192Ir source and 4 plastic catheters embedded in PMMA slabs. The treatment plan data were subsequently imported into an in‐house developed software tool (BrachyGuide) used to obtain corresponding Monte Carlo (MC) simulation dosimetry results with the MCNP code. Detectors’ measurements were compared to both MBDCA‐ and MC‐calculated results in terms of absolute point dose differences, 2D and 3D relative dose and gamma index distributions.Results:Experimental dosimetry results and MC calculations were found in agreement within uncertainties. The corresponding dosimetry comparison between detector measurements and ACE‐calculations showed also a good agreement which deteriorated with increasing distance from the implant due, mainly, to MBDCA assumptions and optimization settings. The latter was highlighted in the comparison of the 3D dose distribution measured by the Presage dosimeter to corresponding ACE calculations.Conclusion:The proposed phantom/methodology can be used for both commissioning and quality assurance of MBDCA‐based TPSs, as well as for benchmarking MC‐calculated reference dose distributions.Research co‐financed by the ESF and Greek funds through the Operational Program Education and Lifelong Learning Investing in Knowledge Society of the NSRF. Research Funding Program: Aristeia.Nucletron, an Elekta company (Veenendaal, The Netherlands) is gratefully acknowledged for providing Oncentra Brachy v4.5 for research purposes.
TH‐AB‐BRA‐05: Infrastructure and Process for Model‐Based Dose Calculation Software Commissioning in Brachytherapy
Authors: Sloboda R , Ballester F , Tedgren A Carlsson , Culberson W , Esthappan J , Haworth A , Lowenstein J , Ma Y , Mourtada F , Papagiannis P , Pike T , Rivard M , Siebert F , Smith R , Spadinger I , Taylor P , Verhaegen F , Vijande J , Beaulieu L 
Published: June 2015

Purpose:To describe a new infrastructure and process that will enable end‐users to commission model‐based dose calculation (MBDC) software for brachytherapy planning, and to invite end‐users to participate in the beta testing phase of this process.Methods:The AAPM working groups on model‐based dose calculation algorithms in brachytherapy (WGDCAB) and brachytherapy source registry (WGBSR) collaboratively implemented the basic MBDC software commissioning workflow described in the AAPM+ESTRO TG‐186 report. For a small number of initial test cases virtual CT image, anatomical structure set, treatment plan, and associated 3D dose data for a single dwell position occupied by a WGDCAB generic high‐dose‐rate Ir‐192 virtual source, with or without a generic shielded applicator, were generated. Dose distributions were calculated using Monte Carlo (MC) code MCNP6, Elekta's Advanced Collapsed cone Algorithm (ACE™), and Varian's Acuros™ BV module. All data were saved in DICOM RT format and uploaded to a provisional, web‐accessible repository in the joint AAPM—IROC Houston brachytherapy source registry. It is envisioned that end‐users will download data for a test case from the repository, verify its correctness, calculate 3D dose locally, and then compare with MCNP6 and MBDC doses obtained from the repository using TPS‐based comparison tools. User guides in preparation for each TPS will facilitate the process.Results:Initial evaluations of DICOM data download, TPS import, MBDC dose calculation, and reference dose comparison indicate that the infrastructure and process described above are both viable and practicable. Ancillary data including generic source and shielded applicator specifications, CAD drawings, and MC code definitions are also available in the repository.Conclusion:With further refinement and beta‐test input from end‐users, a practical MBDC software commissioning process for brachytherapy can be established. A procedure for adding new test cases submitted by end‐users to the repository will be put in place by WGDCAB.
TH‐AB‐BRA‐07: Determination and Evaluation of a Dose‐Rate Conversion Coefficient for the Xoft Axxent® Electronic Brachytherapy Source in the Xoft Titanium Cervical Applicator
Authors: Simiele S , Micka J , Culberson W , DeWerd L 
Published: June 2015

Purpose:A new NIST‐traceable air‐kerma standard has been established for electronic brachytherapy (EBT) sources which has motivated the development of a modified AAPM TG‐43 dosimetry formalism. Due to the low‐energy nature of EBT, it is important to verify that a single dose‐rate conversion coefficient (DRCC) value is appropriate for use with each applicator type, as small changes in applicator thickness between individual applicators due to manufacturing tolerances may have a large impact on the DRCC. This work aims to determine the DRCC for the Xoft source in multiple titanium cervical applicators and verify that a single representative DRCC value is acceptable for clinical use.Methods:The DRCC and radial dose function (RDF) were measured using three titanium cervical applicators and one source. An annulus of Virtual Water™ was used to position TLD‐100 microcubes at 30 ‐degree increments around the source and at radial distances of 1, 2, 3, and 4 cm from the source in a liquid water phantom. A slit collimator, designed to fit inside an HDR1000 Plus well‐ionization chamber, was used to measure the anode‐output profile (AOP) of each source. The measured profile was used with an MCNP5‐simulated AOP to align the manufacturer‐stated anode origin in the plane of the microcubes. A statistical analysis was performed to compare the DRCC values measured in each applicator.Results:Statistical analysis results indicated that there is no significant difference between the DRCCs measured in the different applicators. The RDF values determined in the separate applicators are within 5% of each other at 4 cm depth.Conclusion:The DRCC was measured in three separate applicators to determine if the difference in applicator thickness would require a DRCC specific to each applicator. The results demonstrate that a single representative DRCC, determined with a subset of titanium cervical applicators, is acceptable.This work was partially supported by the NIH radiological sciences training grant T32‐CA009206 and Xoft Inc. (a subsidiary of iCAD).
TH‐CD‐201‐02: Networks, Connectivity, and Interoperability
Authors: Curran B. 
Published: June 2015

Radiation Oncology is a data intensive discipline. Data moves among various systems (imaging, treatment planning, image guidance and delivery) and the development of troubleshooting methods and appropriate QA and QC measures strongly depends on the medical physicists’ understanding of fundamental information technology concepts. This session will cover the concepts involved in networking, data transfer, DICOM and HL7 connectivity, database operations and QA for IT. Databases are at the heart of all modern radiotherapy clinics and are used for planning as well as treatment delivery, and they also drive the observed state of the data at various clients. Querying and reporting from the database is an important skill that medical physicists need to learn. Interactions between clients and databases need to be well understood to ensure that correct, synchronized, and up‐to‐date information is properly communicated amongst all stakeholders involved in the treatment management process. Entrance into the database via DICOM, HL7 and other proprietary transfer mechanisms must also be tested for accuracy of information storage and presentation. Issues with inter‐operability between systems must also be well understood during acceptance testing and commissioning activities. The ongoing efforts of IHE‐RO will be explained in the context of the need for increased engagement on the part of medical physicists.Learning Objectives:

Understand the basic IT infrastructure required to run a radiotherapy department
Become familiar with database concepts to improve troubleshooting skills
Learn the principles of designing a QA program tailored to one's specific clinical IT environment.
Curan: Funding from AAPM for travel and expenses DICOM and Funding from ASTRO for travel and expenses IHE RO
TH‐CD‐210‐00: Nuclear Medicine 102
Authors: MacDougall Robert 
Published: June 2015

There have been significant recent advances in SPECT/CT and PET/CT for Oncology and Cardiology. In oncologic imaging, some commercial SPECT/CT systems now output quantitative uptake values; calibration and calculation of these quantitative uptake values will be discussed. Advances in PET detector design and PET data acquisition modes that have implemented in commercial PET/CT systems will be presented. Innovations in iterative reconstruction of SPECT/CT and PET/CT will also be described.In cardiac imaging, novel collimator designs, such as multi‐pinhole and locally focusing collimators arranged in geometries that are optimized for cardiac imaging have been implemented to reduce imaging time and radiation dose. These new collimators have been coupled with solid‐state photon detectors. The new SPECT scanners demonstrate up to a 7‐fold increase in photon sensitivity and up to 2 times improvement in image resolution. Although PET scanners are used primarily for oncological imaging, cardiac imaging can benefit from the improved PET sensitivity of 3D systems without inter‐plane septa and implementation of the time‐of‐flight reconstruction. Additionally, all major PET vendors now implement resolution recovery techniques. These new methods improve image contrast, image resolution, and reduce image noise for cardiac imaging. New quantification techniques have been proposed for analysis of cardiac SPECT and PET images. These include direct change analysis, motion‐frozen analysis, hybrid quantification of SPECT and anatomical CT angiography data, and integration of several quantitative parameters in composite scores.Learning Objectives:

To discuss clinical implementation of commercial quantitative SPECT/CT systems
To describe advances in PET detector design and data acquisition
To report on innovations in iterative reconstruction of SPECT/CT and PET/CT
4 Describe novel hardware designed for cardiac SPECT
Understand how recent hardware advances in PET/CT are relevant to cardiology
Describe new software techniques for quantification of cardiac SPECT and PET
TH‐CD‐210‐02: Advances in SPECT, SPECT/CT and PET/CT for Cardiology
Authors: Slomka P. 
Published: June 2015

There have been significant recent advances in SPECT/CT and PET/CT for Oncology and Cardiology. In oncologic imaging, some commercial SPECT/CT systems now output quantitative uptake values; calibration and calculation of these quantitative uptake values will be discussed. Advances in PET detector design and PET data acquisition modes that have implemented in commercial PET/CT systems will be presented. Innovations in iterative reconstruction of SPECT/CT and PET/CT will also be described.In cardiac imaging, novel collimator designs, such as multi‐pinhole and locally focusing collimators arranged in geometries that are optimized for cardiac imaging have been implemented to reduce imaging time and radiation dose. These new collimators have been coupled with solid‐state photon detectors. The new SPECT scanners demonstrate up to a 7‐fold increase in photon sensitivity and up to 2 times improvement in image resolution. Although PET scanners are used primarily for oncological imaging, cardiac imaging can benefit from the improved PET sensitivity of 3D systems without inter‐plane septa and implementation of the time‐of‐flight reconstruction. Additionally, all major PET vendors now implement resolution recovery techniques. These new methods improve image contrast, image resolution, and reduce image noise for cardiac imaging. New quantification techniques have been proposed for analysis of cardiac SPECT and PET images. These include direct change analysis, motion‐frozen analysis, hybrid quantification of SPECT and anatomical CT angiography data, and integration of several quantitative parameters in composite scores.Learning Objectives:

To discuss clinical implementation of commercial quantitative SPECT/CT systems
To describe advances in PET detector design and data acquisition
To report on innovations in iterative reconstruction of SPECT/CT and PET/CT
4 Describe novel hardware designed for cardiac SPECT
Understand how recent hardware advances in PET/CT are relevant to cardiology
Describe new software techniques for quantification of cardiac SPECT and PET
TH‐EF‐BRD‐03: Demonstration of a Concurrent Monte Carlo Dose Calculation and Fluence Optimization Platform with Low Memory Footprint
Authors: Yang Y , Svatos M , Zankowski C , Bednarz B 
Published: June 2015

Purpose:To enable a treatment planning solution that utilizes voxel‐specific penalties requires optimizing over a large solution space both quickly and accurately. Although challenging, such methods will enhance the clinical impact of adaptive (online and offline) and biologically guided radiotherapy. Monte Carlo calculations generally provide improved accuracy over deterministic methods, but with increased computation time. Instead, we present a low memory footprint direct Monte Carlo optimization platform that optimizes the fluence concurrently during the MC dose calculation. This reduces the wasted computation time spent on minimally contributing beamlets, and makes the combined optimization and dose calculation tasks both fast and accurate even over a large mathematical space.Methods:The Monte Carlo code Geant4 v9.6 was used to create the Fluence Adjusted Scaled Transport Monte Carlo (FASTMC) platform. The FASTMC platform minimizes clinical cost objectives during the dose calculation using multiple co‐planar sources of arbitrary gantry angle and SID, for rotational or fixed beams. Beamlet particle histories are transported in iterative steps; cost is evaluated after each iteration, with beamlet intensity and dose profile incremented such that the cost is decreased. A Greedy Heuristic algorithm is employed that circumvents the necessity of a dose coefficient matrix, resulting in a memory footprint scaling that is independent of the patient CT resolution, and allows for intelligently biased selection, and calculation of beamlets based on costs in prior iterations.Results:A multi‐field coplanar prostate plan was generated during the MC dose calculation, resulting in an optimized dose profile that is calculated concurrently with the optimized fluence. All clinical constraints for the target and OARs were met for this plan.Conclusion:This study demonstrated the feasibility of optimizing an incident fluence map using voxel‐specific penalties during Monte Carlo dose calculations as a means of treatment planning tailored to emerging radiation therapy delivery paradigms.This work is partially based upon an idea conceived by Varian Medical Systems. This work is partially supported by the NIH Training Grant 2T32CA009206‐36A1.