bluuebunny/crossref_metadata_2025_split huggingface dataset:
TU‐E‐BRB‐01: Is AcurosXBTM Equivalent in Accuracy to Monte Carlo for Complex IMRT and VMAT Dose Calculations?
Authors: Ansbacher W , Bush K , Gagne I , Zavgorodni S , Beckham W 
Published: November 2011

Purpose: To assess the accuracy of a new algorithm, a deterministic solution of the Boltzmann Transport Equations (AcurosXB,TM, Varian Medical Systems), in intensity‐modulated (IMRT) and volumetric‐modulated (VMAT) planning against a benchmark Monte Carlo system and a standard clinical algorithm (AAA, Varian Medical Systems) Method and Materials: Four sites were chosen: prostate, lung, oropharynx and nasopharynx, each exhibiting characteristic challenges for planning. CT‐based plans using 6MV IMRT and VMAT delivery were developed for each site and calculated as dose‐to‐water using Acuros v. 11 and AAA v. 10. Plans were exported to and calculated on a 36‐CPU implementation of the EGSnrc‐BEAMnrc MonteCarlo code with better than 1% statistical uncertainty. Dose and DVH differences were evaluated in the Varian‐Eclipse environment for the target PTVs and relevant critical OARs. Results: Dosimetric differences between Acuros and MonteCarlo were in general much smaller than between AAA and MonteCarlo. For Acuros, the greatest differences occurred in low density lung (densities < 0.1 g/cc) or in air cavities, and were less than 5% of the target dose, extending over regions no greater than 5mm. Corresponding AAA differences were as high as 7% and extended for up to 10mm into higher‐density tissues. As a result, the mean lung PTV dose difference was less than 0.5% for Acuros, but 1.7% for AAA. For the other three sites, the Acuros dose differences were within 3% over more than 97% of a representative volume defined by the 60% isodose contours. AAA dose differences were within 3% over 94% of the volume. Conclusions: Within normal tissue‐like materials (densities up to 1.6g/cc) and in complex clinical planning scenarios involving dynamic beam modulation, Acuros and MonteCarlo generally agreed within the statistical precision of the MonteCarlo dose calculations. Small discrepancies beyond this level could be attributed to differences in treatment head and MLC modelling between Eclipse and BEAMnrc.Partial funding provided through a research agreement with Varian Medical Systems
TU‐E‐BRB‐07: Feasibility of a Dedicated Breast CT Platform for Orthovoltage Rotational External Beam Radiation Therapy: A Simulation Study
Authors: Prionas N , McKenney S , Boone J 
Published: November 2011

Purpose: To evaluate the feasibility of a dedicated breast computed tomography (bCT) platform to deliver therapeutic dose distributions, specifically for partial breast irradiation (PBI), whole breast irradiation (WBI), and dose painting, through orthovoltage rotational external beam radiation therapy (EBRT).Methods: Rotational EBRT using the geometry of a prototype bCT platform was evaluated by means of MCNPX Monte Carlo simulator. A 178 keV monoenergetic photon source was used to approximate 320 kVp photons filtered by 4 mm of copper, as validated by depth‐dose characteristics in polyethylene. The source was rotated around a 14 cm voxelized polyethylene disk (0.1 cm tall) or cylinder (9 cm tall) to simulate primary and primary + scattered photon interactions, respectively. Simulations were also performed using bCT patient images. Beam collimation was varied in the x‐y plane of rotation (1–14 cm) and in the z‐direction (0.1–10 cm).Results: As x‐y collimation narrowed, 2D dose profiles shifted from a cupped profile with high edge dose (14 cm beam) to an increasingly peaked central dose. A 1 cm beam had a center‐to‐cylinder edge dose ratio of 14.8. Similar distributions were observed experimentally. Dose painting for multiple foci, a line distribution, and a ring distribution was demonstrated using multiple rotations with varying collimation. A homogeneous dose distribution (<5% fluctuation) with skin sparing was demonstrated by weighted summation of four dose profiles. Using 2 cm z‐collimation, scatter tails decreased exponentially towards the cylinder top/bottom to 3% of maximum dose. Simulations using patient bCT images demonstrated the potential for treatment planning and image‐guided therapy. Conclusions: A bCT platform can feasibly deliver orthovoltage rotational EBRT for the treatment of breast cancer. A variety of dose distributions can be generated allowing for PBI to a single focus, dose painting, and WBI with skin sparing. Dedicated bCT is a potential platform for image‐guided radiation therapy.One author is a consultant to Varian Imaging Systems (Palo Alto, Calif) and Artemis (Erlangen, Germany) and receives funding from Varian Imaging Systems, Fuji Medical Systems (Stamford, Conn), and Hologic (Bedford, Mass).
TU‐E‐BRC‐10: Selecting Training Data to Optimize Accuracy of Respiratory Surrogate‐Based Tumor Displacement Models
Authors: Malinowski K , McAvoy T , George R , Dieterich S , DˈSouza W 
Published: November 2011

Purpose: Accuracy of respiratory surrogate models of tumor displacement is influenced by selection of appropriate training data, the simultaneous tumor localizations and respiratory surrogate measurements used to create the model. The object of this study was to explore ways in which (1) varying timing and (2) selectively discarding samples of training data can improve surrogate model accuracy. Methods: Motion from 125 lung, 10 liver, and 47 pancreas SBRT treatment fractions from 92 patients was analyzed. Each treatment fraction dataset included radiographically measured tumor positions, positions of three surrogate markers affixed to the torso, and tumor positions predicted by a commercial tumor tracking system from marker measurements. Partial‐least‐squares regression models of tumor position were trained on samples from 26 Hz position data. Low‐frequency (0.05–0.10 Hz) and high‐frequency (26 Hz) training datasets 5–150 seconds in duration were created. The effect of discarding samples with the highest leverage (as measured by Hotellingˈs T,2</sup> statistic) was evaluated. Tumor localization errors were measured over 20 minutes. Results: The baseline tumor localization error (mean +/− standard deviation) in training data was 1.9 +/− 1.7 mm. Mean errors for high‐frequency training data were 4.7–4.9 mm and did not differ significantly with number (1–2), timing, or duration (5–30 sec) of acquisitions. Mean +/− standard deviation errors for low‐frequency training data varied from 4.4 +/− 2.7 mm (0.10 Hz, 2.5‐min acquisition) to 6.6 +/− 16.1 mm (0.05 Hz, 45‐sec acquisition). Removal of high‐leverage samples reduced tumor localization errors for high‐frequency‐derived models by 4–7% but did not reduce errors for low‐frequency data. Conclusions: Lengthening training data acquisitions improves models derived from low‐frequency but not high‐frequency training data. Conversely, removing high‐leverage training samples benefits high‐frequency data only. Training sample selection involves interplay between sampling rate, acquisition duration, and number of training samples.This work was supported in part by grant # CA124766 from the NIH/NCI and by the Achievement Rewards for College Scientists (ARCS) scholarship.
TU‐E‐110‐03: Inverse Geometry X‐Ray Fluoroscopy Using Scanning‐Beam Digital X‐Ray Technology
Authors: Speidel M 
Published: November 2011

Scanning‐beam digital x‐ray (SBDX) is an inverse geometry x‐ray fluoroscopic system using a sequentially illuminated array of focal spot positions, CdTe photon‐counting detector array, and real‐time image reconstructor. The system design substantially improves the dose efficiency of fluoroscopy by minimizing image degrading x‐ray scatter, maintaining high primary detection efficiency at high kVp, and increasing entrance field area. SBDX also has a unique real‐time tomosynthesis capability that enables 3D catheter tracking, fiducial tracking, and 3D vessel dimension analysis during procedures. Recently, image intensity equalization via adaptive reduction of beam‐on time in more transmissive patient regions has been investigated.These advanced fluoroscopic capabilities stem from a radically different x‐ ray source design. SBDX has a large‐area transmission‐style tungsten target bonded to a water‐cooled beryllium plate. A multihole collimator positioned beyond the target defines a series of narrow overlapping x‐ray beams. As the focal spot is electronically deflected from one collimator hole to the next, detector images are simultaneously acquired. Images of the scanning field‐of‐view are reconstructed in real time at up to 30 Hz. Design challenges include achieving sufficient x‐ray source output, fast readout rates in the detector, and the need for real‐time image reconstruction.This lecture will present the principles of the SBDX system and inverse geometry fluoroscopy. Applications of SBDX tomosynthesis and techniques used to increase signal‐to‐noise ratio and reduce heat loading in the x‐ray source will be discussed.This research was supported by NIH Grant R01 HL084022, NovaRay Medical, Inc., and Triple Ring Technologies, Inc.Learning Objectives:1. Understand how inverse geometry x‐ray fluoroscopy design improves dose efficiency2. Understand the operating principles of the scanning‐beam digital x‐ray system3. Understand applications of real‐time tomosynthesis in fluoroscopically‐guided procedures
TU‐E‐220‐03: 3D Ultrasound Guided Minimally Invasive Prostate Therapy and Biopsy
Authors: Fenster A 
Published: November 2011

The prostate biopsy procedure is plagued by high false negative rates (up to 34%) as early‐stage prostate cancer (PCa) is generally not visible on ultrasound. As a result, a negative biopsy does not rule out a diagnosis of PCa, as many tumors are missed on initial biopsy. In such circumstances, patients will undergo multiple repeat prostate biopsy (RPBx) to find undetected PCa. In a repeat biopsy, the physician must either avoid previously biopsied tissue (in cases of prior negative biopsy) or target the same anatomical site for patients with non‐diagnostic, atypical small acinar proliferations (ASAP).3D TRUS is hypothesized to be superior to 2D TRUS for accurate guidance and recording of the prostate biopsy procedure. Patients undergoing RPBx might benefit most from the hypothesized improvements, as previous Bx core locations can be viewed in 3D and used to guide a RPBx. Accuracy is also important when suspicious findings exist on other diagnostic imaging modalities, such as MRI or PET, are used to direct a TRUS‐guided biopsy. In this paper, we describe a new method to guide prostate biopsy procedures using 3D ultrasound. This new approach allows us to guide the biopsy to specific 3D targets in the prostate, record the biopsy locations in 3D, and register the intra‐biopsy procedural 3D ultrasound image with an MR image to guide the biopsy to specific locations in the prostate.Learning Objectives1. Understanding the limitations of conventional 2D ultrasound guided prostate biopsy2. Understanding the issues related to performing the prostate biopsy procedure with 3D US guidance3. Understanding the issues related to the use of MR in conjunction with 3D US to guide the prostate biopsy procedure
TU‐G‐BRA‐04: Biological Optimization in Carbon Therapy
Authors: Oelfke U 
Published: November 2011

The application of high linear energy transfer (LET) radiation in modern radiation oncology, like carbon‐ion therapy, requires different concepts of treatment plan optimization when compared RT‐planning for photon beams. Although, by far not perfect, the standard strategy employs the concept of relative biological effectiveness (RBE), which converts the delivered physical particle dose into a radio‐biologically equivalent dose of low LET beams. In order to introduce the respective RBE models into the inverse planning process of particle therapy one directly aims to optimize the biological effect, mostly expressed in terms of a linear quadratic model (LQM) for a dose‐effect relationship.We will first introduce the general framework of biological optimization for inverse planning of intensity modulated particle therapy (IMPT). The effects of the intrinsic radiation quality on the design of treatment plans will be demonstrated for various forms of dose delivery methods, like spread‐out Bragg peaks (SOBP), distal edge‐tracking (DET) or 3D‐spot scanning and different clinical treatment sites. So far, the employed models only account for the most important radiobiological factor, the anticipated local LET distribution, while other additional factors like the oxygen enhancement ratio or the influence of different fractionation schemes are not considered explicitly.Finally, another important issue will be briefly mentioned, the robustness of biologically optimized treatment plans versus uncertainties in the dose delivery process or even the limited knowledge of the biological input parameters of the employed models that are predicting the biological effect. Some results in the framework of the worst‐case optimization will be discussed.Learning Objectives:1. To review the framework of biological inverse planning of carbon therapy2. To understand the potential and inherent limitations of the optimization approach
TU‐G‐BRB‐07: Evaluation of Tissue‐Equivalent 3D Polymer Gel Dosimeters as Phantoms for PET/CT Verification of Proton Beam Deliveries
Authors: Lopatiuk‐Tirpak O , Su Z , Li Z , Hsi W , Meeks S , Zeidan O 
Published: November 2011

Purpose: to investigate the potential of polymer gel dosimeters for concurrent measurements of three‐dimensional positron emission activity and dose distributions; to evaluate the ability of this technique to identify dosimetric errors due to delivery uncertainties, including those due to range modification and target motion.Methods: three BANG3‐Pro2 gel dosimeters irradiated by proton beams were imaged in a PET/CT scanner, starting within 3 minutes after irradiation. The radiation was delivered as a pristine beam under static conditions, as well as an SOBP, with and without phantom motion. The motion trace was defined by a sinusoidal curve with 2 cm peak‐to‐peak amplitude and the frequency of 0.25 Hz. The dose was read out using an established optical CT scanning procedure. PET/CT images of activated gels were validated against analytical calculations of activity and correlated to measured dose. The effects of target motion on activity and dose distributions were evaluated by volumetric gamma analysis against the treatment plan. Results: The profiles of positron emission activity along the central beam axis were found to be consistent with analytical calculations. Temporal dependence of activity decay suggests that the observed PET signal is due mainly to decay of 15O and 11C. Lateral profiles were found to exhibit good spatial correlation throughout the beam range. This allowed using a modified gamma analysis method to compare the signatures of target motion in PET and dose images. Mean gamma for static PET and dose datasets was 0.07 and 0.11, respectively. For the motion delivery, the mean gamma value increased to 0.63 for both datasets. The spatial distributions of the gamma criterion for PET and dose datasets were qualitatively similar. Conclusions: Polymer gels can accurately capture both dosimetric and activation information. Dosimetric errors due to target motion can be quantified by PET/CT using a novel method of analysis.This work was supported by the Bankhead‐Coley Florida Biomedical Research Program under Grant No. 1BD10‐34212.
TU‐G‐BRC‐09: A Comparison of Step‐And‐Shoot and DMLC IMRT‐Delivery for Real‐Time Tumor Tracking
Authors: Hofmann K , Krauss A , Nill S , Oelfke U 
Published: November 2011

Purpose: The dose distributions of static and dynamically delivered IMRT fields for real‐time target tracking were evaluated to determine which methods work best for the compensation of breathing‐induced organ motion.Methods: A single IMRT beam of a clinical plan was applied with the step‐and‐shoot delivery technique and the sliding‐window technique with the research Siemens 160MLC in order to account for a two‐dimensional, sinusoidal target motion and for a real patient breathing‐curve. For the sliding‐window dose delivery, two different maximum leaf speeds, as well as synchronized and non‐synchronized leaf trajectories were employed. All fields were delivered without and with tracking of the target using three electromagnetic transponders of the Calypso‐System. The dose distributions were measured with radio‐chromic films in a water equivalent phantom in 5cm depth and were compared to the step‐and‐shoot delivery for a non‐moving phantom. For the dose comparison a gamma criterion of 2%/2mm was utilized.Results: For both motions tracking improved the gamma‐index by 13%–32%. For the dynamic delivery no significant advantage was observed between unsynchronized and synchronized leaf trajectories. Moreover no remarkable differences were found by comparing results obtained with different maximum leaf speeds. For both target motions the step‐and‐shoot delivery shows a better dose distribution using the tracking approach: For the 2D‐motion a gamma‐passing rate of 86.3% can be achieved using step‐and‐shoot compared to 78.2% on average for the dynamic dose delivery. For the patient breathing‐motion 83.3% compared to an average of 77.1% were obtained. When comparing the results of both motion patterns, slightly higher passing rates were found with the periodic 2D‐sinusoidal motion. Conclusions: Only small differences were observed for different IMRT dose delivery modes with organ motion tracking, except for the tracked step‐and‐shoot delivery. However, more experiments have to be performed to investigate other IMRT plans and explicit dependencies on the field modulation.Supported by Siemens Healthcare/CR
TU‐G‐214‐02: Imaging the Biological Effect of Dose in the Liver Normal Tissue
Authors: Cao Y 
Published: November 2011

The potential clinical value of in vivo functional and physiological imaging for assessment of dose response of the liver parenchyma has been explored in recent years. Conventional NTCP models are based upon physics parameters (dose, volume). While providing guidance for treatment planning and permitting safe delivery of higher doses than having previously been possible, they do not account for the broad range of individual patient biological radiosensitivity. Early monitoring of the biological effect of dose in the liver normal tissue via functional and physiological imaging can potentially select patients with pre‐clinical signs of hepatic function changes prior to the onset of symptomatic radiation‐induced injury. In addition, mapping regional distributions of hepatic function and its response to dose would permit re‐arrangement of the dose distribution to preserve functional subunits in the liver. Care must be taken, however, to understand the limits of these imaging techniques, including reproducibility, and to validate the biomarker with adequate endpoints.This lecture will provide an overview on functional imaging for developing a dose‐response model of the liver for individualized therapy. The limitations of these techniques will also be discussed.Learning objectives:1. Understand functional imaging as a biomarker for normal tissue response in the liver;2. Understand the influence of imaging parameters and image quality on quantitative metrics and uncertainty in the dose‐response model of the liver.3. Understand clinical applications and limitations.
TU‐G‐110‐05: Efficacy of Fixed Filtration for Rapid KVp‐Switching Dual Energy X‐Ray Systems
Authors: Yao Y , Wang A , Pelc NJ 
Published: November 2011

Purpose: Dose efficiency of dual kVp imaging can be improved if the beams are filtered to remove photons in the common part of their spectra, thereby increasing spectral separation. While there are a number of advantages to rapid kVp‐switching for dual energy, it may not be feasible to have two different filters for the two spectra. Therefore, we are interested in whether a fixed added filter can improve the dose efficiency of kVp‐switching dual energy x‐ray systems.Methods: Simulations were done to decompose known phantoms into basis materials of aluminum and water, using 80 and 140 kVp x‐ray spectra. Precision of the decomposition was evaluated based on the propagation of the Poisson noise in the detected intensities through the decomposition function. We hypothesized that a K‐edge filter would provide the energy selectivity needed to remove overlap of the spectra and hence increase the precision at constant dose. When optimizing the filter design, we considered filtration material (Z), filter thickness, and the relative power allocated to the two beams. We imposed a constraint of <50% loss of x‐ray output due to filtration while maintaining constant entrance dose. The detector absorption efficiency of a CsI screen was also included in the simulation. Results: An improvement in precision of >30% at fixed dose (or lower dose for the same precision) was achieved with optimal filtration. The optimal filter material depends somewhat on the phantom composition and ranges across the lanthanide series. Increasing filtration thickness increases the average spectral separation. When ignoring tube power limitations, the precision improvement with increasing filtration continues increasing, although sublinearly. Conclusions: This study demonstrates the potential of fixed filtration to improve the dose efficiency and material decomposition precision for rapid kVp‐switching dual energy systems.GE Healthcare
TU‐G‐220‐02: Quantitative Ultrasound Imaging: A Historical Persective
Authors: Hall TJ 
Published: November 2011

Quantitative ultrasound (QUS) analysis attempts to gain further understanding of tissue pathology through analysis of the underlying echo signals. QUS is effectively as old as medical ultrasound imaging. A notable example is the initial application of ultrasound to breast tissue. The developers concurrently attempted to differentiate between benign and malignant tissues through an analysis of the echo signals they saw.There have been a many “successes” and a few “failures” during QUS development, but there has been a great deal of progress in QUS methods. Although Lord Rayleigh described the basics of acoustics in the late 1800ˈs, tissue classification with QUS requires a more detailed analysis of wave propagation in tissue. Modern methods more accurately model the interaction of an acoustic wave propagating in inhomogeneous media (like tissue) and more use more sophisticated models of tissue.We (the UW‐Madison Ultrasound Group) and our collaborators (at the University of Illinois, University of Iowa, Intrermountain Healthcare, Duke, Boston University, and Rensselaer Polytechnic Institute), as well as many others around the world, are actively developing QUS methods. The goals of this presentation are to provide a description of some of the key underlying physical principles involved in QUS, some of the key successes and notable failures. From this, it is clear that a rigorous understanding of both the underlying physical principles and basic biology are necessary for maximizing the potential of QUS techniques. Further, the motivation for system‐independent QUS parameter descriptions of tissue will be presented.The prospects for the future development and application of QUS methods are very encouraging. Current clinical ultrasound systems provide higher center frequency, broader bandwidth, and lower noise echo signals, and these lead to improved QUS accuracy and precision. Some of those developments will also be highlighted.Learning Objectives:1. Understand the basic concept of quantitative ultrasound (QUS) analysis2. Understand the range of QUS parameters that describe tissue properties3. Understand the desire for system‐independent QUS4. Begin to appreciate the prospects for clinical application of QUS