bluuebunny/crossref_metadata_2025 huggingface dataset:
WE‐C‐BRD‐01: Automated Segmentation for Radiotherapy Volume Definition
Authors: Brock K , Dong L , Low D , Lu W
Published: April 2010

One of the more exciting advances in radiation therapy is the potential for customizing therapy for each patient through the model of adaptive radiation therapy (ART). This includes obtaining 3‐dimensional functional and anatomic images throughout the course of therapy using both in‐room and conventional imaging platforms. Image acquisition is only the first step in monitoring the quality and efficacy of treatments. The images need to be segmented to allow dosimetric evaluations and comparisons with earlier image datasets. The comparisons will be conducted both to evaluate dose distribution delivery and radiation response and may require acquisition and analysis of multiple image datasets throughout therapy. One of the greatest time consuming aspects of radiation therapy treatment planning is the process of segmenting tumors and normal organs. The expectation that the manpower bandwidth will be available to significantly increase this workload is not realistic, so automated and validated technologies will be necessary to enable wide‐spread implementation of ART. One of the greatest challenges for ART will be to develop efficient and effective methods for reviewing the automated segmentation output. The current paradigm of evaluating structure contours on a slice‐by‐slice basis is too time consuming and does not take advantage of the natural anatomic characteristics of the structures being reviewed. A more efficient method for segmentation review will be required. Automated techniques will also be necessary to map tissue deformation that occurs due to normal day‐to‐day setup and internal organ variations as well as radiation response and disease progression or regression. This symposium will present the state‐of‐the art in automated segmentation, deformable image registration, and segmentation review technologies, technologies that will be critical to the effective implementation of ART.
WE‐C‐BRC‐03: Evaluating Extent of Cell Death in 3D Mid‐To‐High Frequency Ultrasound by Registration with Whole‐Mount Tumor Histopathology
Authors: Vlad R , Kolios M , Moseley J , Czarnota G , Brock K
Published: April 2010

Purpose: In this study, we investigate the precision and accuracy of mid‐to‐high frequency ultrasound imaging to assess non‐invasively cell death for incorporation of this method in pre‐clinical and clinical practice to characterize tumor response to radiotherapy. Method and Materials: Tumor xenografts (n=8) of head and neck cancer were exposed to radiation doses of 2, 4 and 8Gy. Ultrasound images were collected with an ultrasound scanner using frequencies of 15–35MHz before and 24 hours after exposure to radiation. Irradiated tumors exhibited large hyperechoic regions in ultrasounds images 24 hours after exposure to radiation that corresponded to areas of cell death in histology. The ultrasound images were registered with the histological images of the tumor slices taken at regular intervals. The tumor was contoured on histological slices and ultrasound images, the regions of cell death were contoured on histological slices and the hyperechoic regions were contoured on ultrasound images. Each set of contours was converted to a surface mesh. The volume and center of mass were calculated for each representation determined by a surface mesh. Results: The average difference between the relative (to histology) volume representations in histology and ultrasound were 10.7%±8.9% for tumor and 21.7%±12.2% for cell death. The average differences between the relative (to the maximum dimension of the tumor) center of mass of volume representations in histology and ultrasound images were 2.7%±2.0% for tumor and 15.5%±8.9 % for cell death. Conclusion: The method provides the correspondence between the volumes of cell death assessed from histology and from ultrasound imaging and can be used to assess early tumor response to radiotherapy. Part of the differences associated with cell death representation in histological and ultrasound images (21.7%) was caused by the differences in tumor representation (10.7%) in these images. The effect of these uncertainties is the subject of ongoing investigation.
WE‐C‐BRC‐09: Targeting Accuracy in Real‐Time Tumor Tracking Via External Surrogates: A Retrospective Clinical Study
Authors: Riboldi M , Seregni M , Sharp G , Baroni G , Chen G
Published: April 2010

Purpose: To quantify the accuracy of real‐time tumor tracking via external surrogates in a large patient population. Method and Materials: A database of 339 fractions in 86 patients, who received hypofractionated stereotactic body radiotherapy with a robotic linear accelerator (CyberKnife®) between July 2005 and June 2007, was analyzed. The system tracks the tumor in real‐time by using a correspondence model between external marker motion and implanted fiducials. Such model is updated during treatment by intermittent stereoscopic X‐ray imaging, providing ground truth tumor position. The corresponding model includes prediction in the future in order to account for the time lag due to data processing and robot motion (∼115 ms). Predicted tumor positions were compared to ground truth data acquired during treatment to quantify the achieved targeting accuracy. Results: Intermittent imaging provided a statistically robust description of tumor motion 89% of the fractions. Clinical data show that the mean error contribution due to the need for prediction is approximately 0.5 mm. The overall average accuracy in tumor tracking, expressed as the 95% confidence interval of targeting errors, is ∼3.4 mm. We proved that the targeting error increases as a function of the tumor range of motion and treatment site. Larger effects were measured in the superior‐inferior direction, with a 3 mm error increase per 1 cm range of motion variation. Also, unevenly spaced model updating was found to significantly reduce the accuracy in tumor tracking. Conclusion: The accuracy of a state of the art solution for tumor tracking, developed for high precision radiotherapy with a robotic linear accelerator, has been analyzed. Adequate accuracy can be achieved, with caveats when the range of motion is large and the model updating scheme is irregular. Future work will include detailed analysis on progressive upgrades in the correlation model.
WE‐D‐213A‐01: Establishing a Stereotactic Body Radiation Therapy (SBRT) Clinical Program, Part 1: Physics and Dosimetry
Authors: Lovelock D , Benedict S
Published: April 2010

Stereotactic body radiation therapy (SBRT) is a technique in which dose is delivered using either in a single fraction or a hypo‐fractionated schedule. The technique is characterized by the use of high doses per fraction, increased spatial accuracy of the radiation delivery, and a rapid fall‐off of dose outside the treatment volume. The overall goal is to minimize the direct effects of radiation on the surrounding normal tissue while delivering a dose biologically equivalent (or greater) to several weeks of conventionally fractionated radiation therapy to the treatment volume. The intent of SBRT treatment has been to deliver noninvasive tumor‐ablative doses to sharply demarcated lesions so that clinical outcomes comparable to surgery could be achieved without surgical complications. The majority of published clinical data describes the treatment of lung, liver and spinal tumors. The radiobiology of short‐course, high‐dose‐per‐fraction regimens suggests that utilizing SBRT, with significant local dose escalation even to curative doses, is feasible. The number of fractions and total doses currently in clinical use varies widely in the literature, typically ranging from 60 Gy delivered in 10 fractions to 30 Gy delivered in a single fraction.

The Physics and Dosimetry section of the session is to advise medical physicists establishing such a program. The presentation will include an overview of the AAPM Task Group No. 101 on recommendations for SBRT, which has been charged with (1) review the literature and identify the range of historical experiences, reported clinical findings and expected outcomes, (2) review the relevant commercial products and associated clinical findings for an assessment of system capabilities and technology limitations, (3) determine required criteria for setting‐up and establishing an SBRT facility, including protocols, equipment, resources, and QA procedures, and (4) to develop consistent documentation for prescribing, reporting, and recording SBRT treatment delivery.

Learning Objectives:

1. Present the recommended guidelines on establishing an SBRT clinic as presented in the current version of the AAPM Task Group No. 101.

2. Present the technical issues for clinical implementation of SBRT equipment, space considerations, time and personnel considerations.

3. Review the commercial products commonly employed for SBRT with regard to image guidance, localization devices, patient alignment and verification systems

4. Understand the limitation of some treatment planning systems and dose calculation alogorithms as they apply to the highly heterogenous doses within a small target volume typically planned for SBRT.

5. Review the overall quality assurance procedures for systems and patient specific parameters for SBRT deliveries.
WE‐E‐BRD‐05: EGSnrc Benchmarking Against High‐Precision Lateral Distributions of X‐Rays Produced in Thick Targets
Authors: Cojocaru C , Ross C , McEwen M , Faddegon B
Published: April 2010

Purpose: The EGSnrc Monte Carlo code was benchmarked against newly measured angular distributions of x‐rays produced by electron beams stopping in thick targets. Method and Materials: The electron beam was generated using the National Research Council Canada (NRC) Vickers linear accelerator. Five materials: Be, Al, Cu, Ta and Pb, were used as targets and measurements were made at 20 MeV. The absolute absorbed dose was measured at different lateral positions with various ionization chambers (PTW 30013, Exradin A19, and NE2505/3) using various build‐up caps made of PMMA, Brass, Cu, Sn and W alloy. The BEAMnrc code was used to simulate the experimental setup. The geometry, beam and material properties were implemented in BEAMnrc, while the “cavity” user code was used to score the absorbed dose in the ionization chamber air cavity per incident electron up to angles of 25°. Results: For medium‐Z targets the shape agreement between measured and simulated distributions is better than 1 % for the entire scanning range. In terms of absolute dose, it was found that there are differences of up to 4 % related to the build‐up caps used for the ionization chamber. When considering the five targets, a trend with Z of the target material is noticed. For medium‐Z targets the ratio of calculated to measured dose has a variation below 1 %, for the Be target the ratio increases 12 % with the scanning position, while for the Pb target the ratio decreases 5 %. Conclusion: The present study shows that the EGSnrc code predicts x‐ray angular distributions with shapes in agreement with the measured data at the 1 % level for medium‐Z targets. There are still unresolved discrepancies in the absolute dose related to the build‐up cap used for the ionization chamber and the target material.

Partial support from NIH R01 CA104777‐01A2.
WE‐E‐BRB‐01: Impact Or No Impact of Respiratory Motion On Helical Tomotherapy Dose Delivery
Authors: Ngwa W , Shah A , Meeks S , Kupelian P , Langen K
Published: April 2010

Purpose: In this work, the dosimetric consequences of respiratory motion on helical tomotherapy (HT) treatment delivery are comprehensively investigated. The dependence of dose errors on respiratory‐motion parameters: amplitude, period, phase, and motion direction is examined. The impact of characteristic breathing‐motion induced offsets and drifts on dose errors is also scrutinized, and the influence of target margin and field size on the results evaluated. Method and Materials: Treatment delivery into a moving patient was simulated by incorporating synthetic motion data in the HT dose calculation engine, which includes all relevant treatment dynamics such as MLC opening times, gantry rotation, and couch translations. This allowed for a realistic evaluation of the dosimetric sensitivity of over 12 HT plans (3 margins, 2 field sizes, two clinical lung cancer cases), retrospectively. The prescription dictated a minimum dose of 50 Gy delivered to 95% of the planning target volume (PTV). Results: For PTV equal to the internal target volume (ITV) (which, takes only breathing motion amplitude into account), the results show that mean regular breathing amplitudes engender GTV D95% errors less than 1.5 %, regardless of period, phase or motion direction. Meanwhile, average practical offsets generate less than 3.6 % GTV D95% errors. Results also show that for SI breathing motion, the GTV D95% dose error is virtually the same regardless of margin size. If the gantry period to breathing period ratio is an integer, GTV (or PTV) dose errors may sometimes be sensitive to the breathing phase. Overall, the dose error magnitude is plan specific, increases with increase in amplitude, offset or drift, and depends on motion direction and field size. Conclusion: The dosimetric impact of respiratory motion on HT treatment delivery is plan specific. However, for non phase‐sensitive plans with PTV equal ITV, average regular breathing motion and offsets engender insignificant dosimetric consequences.
WE‐E‐304A‐06: The Influence of Initial Outlines On Observers
Authors: Sensakovic W , Starkey A , Roberts R , Straus C , Caligiuri P , Armato S
Published: April 2010

Purpose: When manually segmenting structures in medical images, an observer identifies the structure and then traces the structure's boundary. When an observer instead is presented with an initial segmentation boundary from a computerized method, the expectation is that the observer will alter that outline as necessary to fit their own perception of the boundary, which should not be substantially influenced by the initial, computer‐defined segmentation. This expectation is implicit when observers modify computerized outlines to establish “truth,” measure the area/volume of a structure, or use a computerized system as an initial reader. The goal of this study was to quantifying the extent to which initial outlines influence human observers. Method and Materials: A database of 30 thoracic CT scans from different mesothelioma patients was collected. For each scan, 5 sections were randomly selected for analysis, and three experienced observers independently outlined all mesothelioma tumor in each of these 150 sections to produce “truth outlines.” After a three‐month period, each observer was presented with all 450 truth outlines, which served as “initial outlines” in this second component of the study, and observers could alter these initial outlines to produce “modified outlines” that best captured their perception of tumor boundary. The area‐of‐overlap measure (AOM) between pairwise combinations of outlines was calculated. Results: The average AOM between the truth outlines of a given observer and the modified outlines derived from the initial outline of that same observer was 0.842 ± 0.009 across all observers. In comparison, the average AOM between the truth outlines of a given observer and the modified outlines derived from the initial outlines of the other two observers was 0.443 ± 0.006 across all observers. Conclusion: The substantial difference between the two mean AOM values implies that observers are strongly impacted by the presence of an initial outline.
WE‐E‐213A‐03: Practical Aspects of Commissioning and Calibration of Clinical Orthovoltage Units
Authors: Abdel‐Rahman W , Liang L , AlDahlawi I , Seuntjens J
Published: April 2010

Despite the emphasis on megavoltage radiation therapy, kV units are still being acquired and used in clinical radiation therapy for superficial lesions and specialized treatment techniques. The dosimetry of kV X‐ray beams is tricky and subject to increased uncertainties due to the energy dependence of many quantities involved in determination of absorbed dose at the reference point. In addition, there are a large variety of beam modifiers and applicators used each of which requires separate relative output measurements sometimes affected by issues such as electron contamination and scatter. This presentation concentrates on the practical aspects of a typical clinical AAPM TG61 protocol implementation. Following aspects will be discussed: (1) a review of the calibration protocol formalism; (2) ionization chamber types and calibration; (3) beam quality measurements; (4) relative measurements for open and closed applicators; (5) other clinical aspects such as tertiary collimation, etc.

Educational goals:

1. understanding of the concepts and formalism of the TG61 protocol

2. understanding the characteristics of ionization chambers with respect to kV dosimetry

3. elucidating aspects of the commissioning of orthovoltage units

4. illustrating special clinical situations
TH‐SAM‐BRB‐01: HDR and LDR Brachytherapy: Everything You Need to Know
Authors: Thomadsen B , Miller R
Published: April 2010

The development of Brachytherapy began about 1899 following the purification of radium by Pierre and Marie Curie and has been developing rapidly and continually since. The focus of this presentation will be on the most common current utilizations and aspects that present new and controversial issues: brachytherapy applications in breast, prostate, intra‐operative lung and for macular degeneration; electronic brachytherapy, error management and reduction; and some quality management issues. The discussion will consider how the physical nature of brachytherapy enhances and limits the treatments. A list of resources will be provided covering the basics and history of Brachytherapy.

Learning Objectives:

1. Compare and contrast the advantages of LDR vs. HDR in the treatment of prostate cancer

2. Compare electronic brachytherapy to traditional brachytherapy

3. Review the more recent brachytherapy options for the treatment of breast cancer

4. Introduce brachytherapy for intra‐operative lung and macular degeneration

5. Review management of errors and reporting in brachytherapy and how to perform a root cause analysis

6. Review guidelines for quality assurance
TH‐A‐BRD‐01: The Future of NIH Research Funding
Authors: Kitt C , Williamson J , Paganetti H
Published: April 2010

The National Institute of Health (NIH) is the most important source for funding medical physics research in the US. Consequently it has a profound impact on careers in medical physics. Most medical physicists rely on NIH funding to support their research ideas and launch or maintain research projects. While innovative research ideas are a pre‐requisite to attract funding, it is also important to understand the mechanisms of grant application.

For this year the NIH has made significant changes to its grant review and submission process. These changes were driven by three aims:

1. Engage the Best Reviewers

Reviewing grant applications can be a huge burden for scientists. Consequently, new reviewers will be given additional flexibility regarding their tour of duty. Further, efforts will be undertaken to improve retention of standing review members. Studies will be conducted on the feasibility of using high‐bandwidth support for review meetings to provide greater flexibility and alternatives for in‐person meetings.

2. Improve the Quality and Transparency of Review

A new criterion‐based scoring on a 1‐7 scale, using structured critiques, will be introduced. The reviewers will provide feedback through scores and critiques for each criterion in a structured summary statement. Streamlined applications will receive a preliminary score. Applications will be shortened significantly to for example a 12‐page research plan for an R01 application.

3. Ensure Balanced and Fair Reviews across Scientific Fields and Career Stages, and Reduce Administrative Burden

To ensure that the largest number of high quality and meritorious applications receive funding earlier and to improve system efficiency, NIH is considering separate percentiling of new and resubmitted applications and permitting one amended application. NIH is establishing an Early Stage Investigator designation for which clustering of applications is considered. The same approach will be considered for clinical research applications.

This educational session is divided into three presentations followed by a panel discussion with questions from the audience. It will address newcomers and established researchers. The presentations will cover the following topics:

1. “Overall strategies for successful NIH grant applications.”

2. “Imminent changes in the NIH grant submission and review.”

3. “Impact of the changes from an applicant's point of view.”

Learning Objectives:

1. Understand the new NIH grant submission and review process

2. Understand the imminent changes in the NIH grant submission and review process
TH‐C‐BRC‐06: Implementation of An Image‐Guided System for Conformal Small Animal Irradiation: Characterization, QA, and Workflow
Authors: Lindsay P , Ansell S , Jelveh S , Clarkson R , Wilson G , Hill R , Jaffray D
Published: April 2010

Purpose: To implement a custom built system for image‐guided conformal pre‐clinical irradiation. Method and Materials: The system consists of variable kVp x‐ray tube (5–225 kVp), mounted on a rotating gantry with a flat‐panel detector (detector element size: 0.4 mm). Animal positioning is achieved through a three‐dimensional translational stage. Dosimetric characterization of the system was performed for two beam qualities: 100 kVp, HVL 2.8 mm Al, and 225 kVp, HVL 0.9 mm Cu. Winston‐Lutz tests were performed to evaluate isocentricity. In‐house software was designed to support fluoroscopic and cone‐beam CT (CBCT) imaging, and static and arc treatment using preset treatment protocols. These tools allow high throughput image‐guided set‐up and treatment of animals. The overall workflow was characterized by hidden‐targets tests, including localization and dosimetric accuracy. Results: The absolute output of the x‐ray tube was verified by 3rd party TLD measurements. Output and energy agreed with calibration to within 2% upon monthly quality assurance tests. Flexmaps repeated over 8 months were consistent within ± 0.1 mm. Winston‐Lutz tests revealed a residual system flex of ±0.5 mm and ±0.1 mm in the cone and fan directions, respectively. Target localization accuracy in repeated tests using both fluoroscopic and CBCT imaging was sub‐millimeter. CBCT images were reconstructed with 0.2 mm isotropic voxels. This system has been in use for small animal irradiations for 10 months, during which time over 600 animal irradiations have been performed. Conclusion: Image‐guided conformal irradiation systems provide an important tool for translational research in radiation oncology. This system recapitulates the clinical tools for radiation oncology, and provides a versatile and easy‐to‐use platform for conformal image‐guided treatment of small animals. Conflict of Interest: Some of the co‐authors are inventors of this system, and may financially benefit through its successful commercialization by Precision X‐Ray, Inc.
TH‐C‐303A‐05: Development of a Dynamic KV Collimator for Low Diagnostic Dose Real‐Time 3D Motion Tracking During Radiation Therapy by Combined MV‐KV Imaging
Authors: Wiersma R , Pearson E , Pelizzari C
Published: April 2010

Purpose: Currently, real‐time 3D MV‐kV monitoring requires the use of continuous kV imaging throughout the treatment process leading to high diagnostic dose costs. For MV‐kV tracking purposes the only needed kV image information are the projected images of the metallic fiducial markers. Generally these markers are small (3mm in length and 0.8mm in diameter), and for a standard 40cm × 30cm kV image comprise less than 1% of the total area. The proposed technique here uses a dynamic kV aperture to confine the kV exposure to a small region of interest (ROI) encompassing only the markers. As the internal markers move, the aperture is dynamically updated using feedback information provided by the last known marker positions. Method: A Varian Trilogy equipped with both an EPID and a kV imaging system was used. The kV collimator was mounted over the kV source and consists of four lead blades placed orthogonally on low friction linear guide rails. The position of each blade was controlled independently using a servomotor. MV‐kV imaging was performed and software was used to calculate a suitable ROI that will be used as an input for the kV collimator. As the internal markers move, the aperture will be dynamically updated using the last known marker positions. Results: The combination of controller circuitry and chosen servomotors allows for blade travel speed of up to 11mm/s, depending on orientation, with an accuracy of 0.2mm in the collimator plane. This should be sufficient to keep the ROI properly centered on nearly any fiducial cluster. Conclusion: The technique proposed here would potentially lower the kV exposure by a factor of 50–500 depending on the speed, number, and spatial separation of the fiducials. The technology is directly applicable to any kV imaging system where only selective ROI information is required.
TH‐C‐304A‐05: A Fast Deformable Model Based 3D Registration Algorithm for Image Guided Prostate Radiotherapy
Authors: Zhou J , Kim S , Jabbour S , Goyal S , Haffty B , Chen T , Chang S , Metaxas D , Yue N
Published: April 2010

Purpose: To present a novel and fast registration method based on soft tissue, i.e., prostate, to capture the transformation between the planning 3D CT images and treatment 3D cone‐beam CT images for external beam radiotherapy of the prostate. Method and Materials: We present a global‐to‐local shape registration framework as well as an automatically segmentation method in the 3D CBCT images. The global registration is based on mutual information method and the local registration is based a deformable superquadric framework to minimize the Euclidian distance of the corresponding nodes from global transformation. The method is applied on 6 datasets consisting of both planning CT and CBCT images of prostate patients. The target volumes delineated by a same radiation oncologist were chosen as the gold standards and were compared with the segmented and registered results. Results: The quantitative segmentation results are summarized in Table 1 and 2 of the supporting materials. Table 1 shows the distance‐based estimator and volume‐based estimator between the segmentation results of our algorithm and those of the gold standards. The mean distance ranges from −0.17 mm to −0.85 mm and the overlap ratio ranges from 79% to 91%. These results demonstrate reasonably good agreement between the segmentation results and the gold standards. Table 2 shows that the mean overlap ratio ranges from 85.2% to 95% of the prostate volumes after registration. On the average, the entire segmentation and registration time was about 2 minutes. Conclusions: We present a novel and fast deformable registration method to capture the transformation between the planning and treatment images for external beam radiotherapy. We also present the promising results of our method applied to clinical datasets. These preliminary results show that the proposed method is robust and reasonably fast for the registration of the deformable soft tissue of prostate.
TH‐D‐211A‐01: Reimbursement for Medical Physics Services
Authors: Goodwin J
Published: April 2010

As health care costs continue to escalate and reimbursements rates tighten, medical physicists must be prepared to demonstrate their economic value as well as their clinical value. This talk will review the major reimbursement processes that exist and the fundamental differences in how payment rates are established for hospital outpatient departments, free standing facilities and physicians. The CPT® coding system will be reviewed with special emphasis on the Continuing Medical Physics Consultation code 77336 and the Special Medical Radiation Physics Consultation code 77370. Proper reporting documentation will be discussed. Sources of information on reimbursement and coding will be identified. Finally, current activities of the AAPM Professional Economic Committee will be highlighted.

Learning Objectives:

1. To understand the major reimbursement systems and how payment rates are established

2. To understand the CPT® coding system and the need for proper documentation in the clinic

3. To identify authoritative sources of reimbursement and coding information

4. To learn about AAPM PEC activities and how they benefit the membership
TH‐D‐BRD‐03: Experience with Error Reporting and Tracking Database Tool for Process Improvement in Radiation Oncology
Authors: Mutic S , Oddiraju S , Parikh P , Brame S , El Naqa I , Low D , Wu B
Published: April 2010

Purpose: To present long‐term results of systematic near‐miss and actual error reporting and analysis system based on a web‐based tool and effects of formal process improvement structure on error rates and safety culture in radiation therapy (RT). Materials and Methods: An internally developed web‐based system was used to report, track, and analyze errors and near‐misses in a large RT department for almost two years. The system was designed as an efficient and effective process for collecting, storing, and analyzing the failure rate data in individual RT facilities. The aim of the system was to support process improvement in patient care and safety. The reporting tool was designed so individual events could be reported in as little as two minutes. Events were categorized based on functional area, type, and severity of failure. The events were processed and analyzed by a formal process improvement group which used the data and statistics collected through the web‐based tool for guidance in reengineering clinical processes. The results for the first nineteen months of clinical use of the system are presented. Results: The collected data and the process improvement structure resulted in measureable safety and error rate improvements in several clinical areas. The collected data was also very effective in identifying ineffective measures and efforts which did not produce improvements in clinical processes. The overall process demonstrated that it was possible to establish and maintain a high functioning safety culture in radiation oncology. The error reporting compliance, though voluntary, was very high and consistent from the inception of the process through the date of this report. Conclusions: Near‐miss and actual error collection process in RT can result in quantifiable safety and error rate improvements and more importantly it can result in a sustainable safety culture.
Wind noise in hearing aids with directional and omnidirectional microphones: Polar characteristics of custom-made hearing aids
Authors: Chung King , McKibben Nicholas , Mongeau Luc
Published: April 2010

The purpose of this study was to examine the characteristics of wind noise at the output of in-the-ear, in-the-canal, and completely-in-the-canal hearing aids. The hearing aids were programed to have linear amplification with matching flat frequency responses for directional (DIR) and omnidirectional (OMNI) microphones. The microphone output was then recorded in a quiet wind tunnel when the Knowles electronic manikin for acoustic research (KEMAR) head was turned from 0° to 360°. The overall, 125, 500, and 2000 Hz one-third octave band flow noise levels were calculated and plotted in polar patterns. Correlation coefficients, average differences, and level differences between DIR and OMNI were also calculated. Flow noise levels were the highest when KEMAR was facing the direction of the flow and angles between 190° and 250°. The noise levels were the lowest when the hearing aids were facing the direction of the flow. The polar patterns of DIR and OMNI had similar shapes and DIR generally had higher levels than OMNI. DIR, however, could have lower levels than OMNI in some angles because of its capability to reduce noise in the far field. Comparisons of polar characteristics with behind-the-ear hearing aids, and clinical and engineering design applications of current results are discussed.
Influence of an oscillating circuit on the radiation of transient acoustic waves by an electroelastic cylinder
Authors: Babaev A. E. , Babaev A. A. , Yanchevskiy I. V.
Published: April 2010

The problem of nonstationary wave radiation in an infinitely long thick-wall piezoelectric cylinder in fluid medium is considered. The influence of an oscillating circuit with lumped parameters on characteristics of transient process is taken into consideration. Problem formulation is executed within the forced electrostatic theory, acoustic approximations, and quasistatic theory for electric circuit. The solution method is based on the integral Laplace transform in time. This allows analytically reducing the problem to solving a system of Volterra integral equations with retarded arguments. The numerical results of calculations are presented and analyzed.
A detailed analysis about penumbra caustics
Authors: Marchiano Régis
Published: April 2010

A penumbra caustic is an interrupted fold caustic. It looks like a fold caustic but with a finite size. This kind of caustic results from the focusing of a semi-infinite concave wavefront. The pressure around the extremity of the penumbra caustic can be expressed analytically in terms of incomplete Airy function for linear monochromatic waves. Using asymptotic expansions in the vicinity of the extremity, that classical result is rederived. It can be matched with the classical Fresnel diffraction before the extremity and with the classical diffraction catastrophe theory after the extremity. Nevertheless the linear modeling is not valid for incoming shock waves. A theoretical description of the phenomenon of focusing of shock waves at a penumbra caustic is given. It relies on the Zabolotskaya–Khokhlov equation. Numerical simulations are used to compute the behavior of this phenomenon. In particular, the numerical simulations show the presence of a triple point inside the pressure field. Finally, the theory and the numerical simulations are applied to explain the apparent paradox of non-causality around fold caustic.
On wavemodes at the interface of a fluid and a fluid-saturated poroelastic solid
Authors: van Dalen K. N. , Drijkoningen G. G. , Smeulders D. M. J.
Published: April 2010

Pseudo interface waves can exist at the interface of a fluid and a fluid-saturated poroelastic solid. These waves are typically related to the pseudo-Rayleigh pole and the pseudo-Stoneley pole in the complex slowness plane. It is found that each of these two poles can contribute (as a residue) to a full transient wave motion when the corresponding Fourier integral is computed on the principal Riemann sheet. This contradicts the generally accepted explanation that a pseudo interface wave originates from a pole on a nonprincipal Riemann sheet. It is also shown that part of the physical properties of a pseudo interface wave can be captured by loop integrals along the branch cuts in the complex slowness plane. Moreover, it is observed that the pseudo-Stoneley pole is not always present on the principal Riemann sheet depending also on frequency rather than on the contrast in material parameters only. Finally, it is shown that two additional zeroes of the poroelastic Stoneley dispersion equation, which are comparable with the P¯-poles known in nonporous elastic solids, do have physical significance due to their residue contributions to a full point-force response.
Sound production by singing humpback whales
Authors: Mercado Eduardo , Schneider Jennifer N. , Pack Adam A. , Herman Louis M.
Published: April 2010

Sounds from humpback whale songs were analyzed to evaluate possible mechanisms of sound production. Song sounds fell along a continuum with trains of discrete pulses at one end and continuous tonal signals at the other. This graded vocal repertoire is comparable to that seen in false killer whales [Murray et al. (1998). J. Acoust. Soc. Am. 104, 1679–1688] and human singers, indicating that all three species generate sounds by varying the tension of pneumatically driven, vibrating membranes. Patterns in the spectral content of sounds and in nonlinear sound features show that resonating air chambers may also contribute to humpback whale sound production. Collectively, these findings suggest that categorizing individual units within songs into discrete types may obscure how singers modulate song features and illustrate how production-based characterizations of vocalizations can provide new insights into how humpback whales sing.
Initialization method for speech separation algorithms that work in the time-frequency domain
Authors: Sarmiento Auxiliadora , Durán-Díaz Iván , Cruces Sergio
Published: April 2010

This article addresses the problem of the unsupervised separation of speech signals in realistic scenarios. An initialization procedure is proposed for independent component analysis (ICA) algorithms that work in the time-frequency domain and require the prewhitening of the observations. It is shown that the proposed method drastically reduces the permuted solutions in that domain and helps to reduce the execution time of the algorithms. Simulations confirm these advantages for several ICA instantaneous algorithms and the effectiveness of the proposed technique in emulated reverberant environments.
The direct field boundary impedance of two-dimensional periodic structures with application to high frequency vibration prediction
Authors: Langley Robin S. , Cotoni Vincent
Published: April 2010

Large sections of many types of engineering construction can be considered to constitute a two-dimensional periodic structure, with examples ranging from an orthogonally stiffened shell to a honeycomb sandwich panel. In this paper, a method is presented for computing the boundary (or edge) impedance of a semi-infinite two-dimensional periodic structure, a quantity which is referred to as the direct field boundary impedance matrix. This terminology arises from the fact that none of the waves generated at the boundary (the direct field) are reflected back to the boundary in a semi-infinite system. The direct field impedance matrix can be used to calculate elastic wave transmission coefficients, and also to calculate the coupling loss factors (CLFs), which are required by the statistical energy analysis (SEA) approach to predicting high frequency vibration levels in built-up systems. The calculation of the relevant CLFs enables a two-dimensional periodic region of a structure to be modeled very efficiently as a single subsystem within SEA, and also within related methods, such as a recently developed hybrid approach, which couples the finite element method with SEA. The analysis is illustrated by various numerical examples involving stiffened plate structures.
Data-driven automated acoustic analysis of human infant vocalizations using neural network tools
Authors: Warlaumont Anne S. , Oller D. Kimbrough , Buder Eugene H. , Dale Rick , Kozma Robert
Published: April 2010

Acoustic analysis of infant vocalizations has typically employed traditional acoustic measures drawn from adult speech acoustics, such as f0, duration, formant frequencies, amplitude, and pitch perturbation. Here an alternative and complementary method is proposed in which data-derived spectrographic features are central. 1-s-long spectrograms of vocalizations produced by six infants recorded longitudinally between ages 3 and 11 months are analyzed using a neural network consisting of a self-organizing map and a single-layer perceptron. The self-organizing map acquires a set of holistic, data-derived spectrographic receptive fields. The single-layer perceptron receives self-organizing map activations as input and is trained to classify utterances into prelinguistic phonatory categories (squeal, vocant, or growl), identify the ages at which they were produced, and identify the individuals who produced them. Classification performance was significantly better than chance for all three classification tasks. Performance is compared to another popular architecture, the fully supervised multilayer perceptron. In addition, the network’s weights and patterns of activation are explored from several angles, for example, through traditional acoustic measurements of the network’s receptive fields. Results support the use of this and related tools for deriving holistic acoustic features directly from infant vocalization data and for the automatic classification of infant vocalizations.
Psychophysical and electrophysiological aerial audiograms of a Steller sea lion (Eumetopias jubatus)
Authors: Mulsow Jason , Reichmuth Colleen
Published: April 2010

A within-subject comparison of auditory steady-state response (ASSR) and psychophysical measurements of aerial hearing sensitivity was conducted with an individual of the largest otariid species, the Steller sea lion. Psychophysical methods were used to obtain an unmasked aerial audiogram at 13 frequencies, spanning a range of 0.125–34 kHz. The subject had a hearing range (frequencies audible at 60 dBrms re 20 μPa) of about 0.250–30 kHz, and a region of best hearing sensitivity from 5–14.1 kHz. The psychophysical aerial audiogram of this Steller sea lion was remarkably similar to aerial audiograms previously obtained for California sea lions and northern fur seals, suggesting that the otariid pinnipeds form a functional hearing group. ASSR thresholds, measured at frequencies of 1, 2, 5, 10, 20, and 32 kHz, were elevated relative to corresponding psychophysical thresholds, ranging from +1 dB at 20 kHz, to +31 dB at 1 kHz. The ASSR audiogram accurately predicted the subject’s high-frequency cutoff, and provided a reasonable estimate of hearing sensitivity at frequencies above 2 kHz. In testing situations where psychophysical methods are not possible, ASSR methods may provide an objective and efficient estimate of behavioral hearing sensitivity in otariid pinnipeds.
Adaptive phase calibration of a microphone array for acoustic holography
Authors: Teal Paul D. , Poletti Mark A.
Published: April 2010

Previous work has indicated that a limitation on the performance of a circular microphone array for holographic sound field recording at low frequencies is phase mismatch between the microphones in the array. At low frequencies these variations become more significant than at mid-range and high frequencies because the high order phase mode responses at low frequencies are lower in amplitude. This paper demonstrates the feasibility of a “self-calibration” method. The basis of the calibration is to estimate the location of one or more wide-band sources using mid-range frequencies and to use this source location information to perform correction to the array at low frequencies. In its simplest form the calibration must be performed in an anechoic environment, since multipath effects at widely differing frequencies are uncorrelated. The approach is first demonstrated in such an environment using recordings from an array of high quality microphones. The technique is then extended to an adaptive calibration that can be used in an environment that is somewhat reverberant. The validity of the adaptive approach is demonstrated using recordings from an array of inexpensive microphones.
Radiation impedance of condenser microphones and their diffuse-field responses
Authors: Barrera-Figueroa Salvador , Rasmussen Knud , Jacobsen Finn
Published: April 2010

The relation between the diffuse-field response and the radiation impedance of a microphone has been investigated. Such a relation can be derived from classical theory. The practical measurement of the radiation impedance requires (a) measuring the volume velocity of the membrane of the microphone and (b) measuring the pressure on the membrane of the microphone. The first measurement is carried out by means of laser vibrometry. The second measurement cannot be implemented in practice. However, the pressure on the membrane can be calculated numerically by means of the boundary element method. In this way, a hybrid estimate of the radiation impedance is obtained. The resulting estimate of the diffuse-field response is compared with experimental estimates of the diffuse-field response determined using reciprocity and the random-incidence method. The different estimates are in good agreement at frequencies below the resonance frequency of the microphone. Although the method may not be of great practical utility, it provides a useful validation of the estimates obtained by other means.
Detecting cavitation in mercury exposed to a high-energy pulsed proton beam
Authors: Manzi Nicholas J. , Chitnis Parag V. , Holt R. Glynn , Roy Ronald A. , Cleveland Robin O. , Riemer Bernie , Wendel Mark
Published: April 2010

The Oak Ridge National Laboratory Spallation Neutron Source employs a high-energy pulsed proton beam incident on a mercury target to generate short bursts of neutrons. Absorption of the proton beam produces rapid heating of the mercury, resulting in the formation of acoustic shock waves and the nucleation of cavitation bubbles. The subsequent collapse of these cavitation bubbles promote erosion of the steel target walls. Preliminary measurements using two passive cavitation detectors (megahertz-frequency focused and unfocused piezoelectric transducers) installed in a mercury test target to monitor cavitation generated by proton beams with charges ranging from 0.041 to 4.1 μC will be reported on. Cavitation was initially detected for a beam charge of 0.082 μC by the presence of an acoustic emission approximately 250 μs after arrival of the incident proton beam. This emission was consistent with an inertial cavitation collapse of a bubble with an estimated maximum bubble radius of 0.19 mm, based on collapse time. The peak pressure in the mercury for the initiation of cavitation was predicted to be 0.6 MPa. For a beam charge of 0.41 μC and higher, the lifetimes of the bubbles exceeded the reverberation time of the chamber (∼300 μs), and distinct windows of cavitation activity were detected, a phenomenon that likely resulted from the interaction of the reverberation in the chamber and the cavitation bubbles.
An improved method to determine the onset timings of reflections in an acoustic impulse response
Authors: Usher John
Published: April 2010

Determining the absolute onset time of reflections in an acoustic impulse response (IR) has applications for both subjective and physical acoustics problems. Although computationally simple, a first-order energetic analysis of the IR can lead to false-positive identification of reflections. This letter reports on a method to determine reflection onset timings using a modified running local kurtosis analysis to identify regions in the IR where the distribution is non-normal. IRs from both real and virtual rooms are used to validate the method and to find optimum analysis window sizes.
Open and Closed Case
Authors: Vinson Valda
Published: April 2010

An occluded site stabilizes charged amino acids as they cross the membrane field to achieve a switchlike channel opening.
Localized Readiness
Authors: Ray L. Bryan
Published: April 2010

Specific sites within the nucleus may promote maintenance of genes in a state of enhanced responsiveness.
Klf15
Deficiency Is a Molecular Link Between Heart Failure and Aortic Aneurysm Formation
Authors: Haldar Saptarsi M. , Lu Yuan , Jeyaraj Darwin , Kawanami Daiji , Cui Yingjie , Eapen Sam J. , Hao Caili , Li Yan , Doughman Yong-Qiu , Watanabe Michiko , Shimizu Koichi , Kuivaniemi Helena , Sadoshima Junichi , Margulies Kenneth B. , Cappola Thomas P. , Jain Mukesh K.
Published: April 2010

The co-occurrence of heart failure and aortic aneurysms may be explained by their common dependence on a transcriptional regulator, which now presents a possible therapeutic target.