bluuebunny/crossref_metadata_2025 huggingface dataset:
WE‐D‐T‐617‐09: A Novel Approach to the Optimization of Beam Current Modulation for Proton Therapy Beam Using Passive Scattering
Authors: Lu H , Kooy H
Published: June 2005

Purpose: To develop an effective and efficient method for optimizing the beam current modulation (BCM) pattern in commissioning proton beams using passive scattering and range modulation wheels. This modulation pattern is essential in producing beams with properly weighted spread‐out Bragg peaks for the desired depth‐dose distribution. Method and Materials: The proton beam nozzle houses the spinning modulation wheel (600 rpm) and the various scattering components and translates the modulated beam current to a depth‐dose distribution. This translation can be described, for a specific configuration of the nozzle, i.e., with a specific wheel position at a specific time, by a function C(x, t), defined as the dose produced at depth x and time t for a unit beam current at the time t. While the function C(x, t) is difficult to calculate theoretically due to the complex scattering paths in the nozzle and the phantom, it can be easily obtained by measuring the dose as a function of time and by a proper deconvolution taking into account the delays from the measuring circuit. With C(x, t) determined, one can calculate the depth dose distributions for any given BCM. Then the optimal BCM can be found, not by repeated measurements, as was often done before, but by numerical calculations. A window‐based software has been developed to measure the time‐dose functions and to perform numerical BCM optimizations. Results: The method was applied to optimize the BCM for a number of proton beams. The differences between the calculated and measured depth dose distributions are less than 1%, well within the clinical requirement. Conclusion: We have developed an effective and efficient method for optimizing the beam current modulation for proton therapy beams using passive scattering.
WE‐D‐T‐6E‐04: EUD Based Beam Orientation Selection
Authors: Schreibmann E , Levy D , Xing L
Published: June 2005

Purpose: To develop a clinically sensible beam orientation ranking model with incorporation of dose‐volume effects and to show its utility for IMRT beam placement. Materials and methods: Generally, a beamlet/beam is more preferable if it can deliver a higher dose to the target without exceeding the sensitive structure(s) tolerance. In previous geometry‐ or dose‐based approach, the beamlets are treated independently and, to compute the maximally deliverable target dose, each beamlet is pushed to the maximum intensity without considering other beamlets. When volumetric‐structures are involved, there are numerous dose distributions corresponding to the same dose‐volume tolerance and the beamlets are no longer independent. We model a volumetric organ by using EUD and find the beam profile that delivers the maximum target dose without violating the EUD constraints using an iterative algorithm. Four clinical cases are planned with and without the guidance of the angular ranking information and the qualities of the two types of IMRT plans are compared. Results: An angular ranking model with consideration of volumetric effect has been developed. It is shown that the previously reported dose‐based angular ranking represents a special case of the formalism proposed here. Application to four IMRT cases indicated that the proposed technique is capable of producing clinically sensible angular ranking. In all cases, we found that the IMRT plans obtained under the guidance of EUD‐based angular ranking are significantly improved in comparison with that obtained using the conventional uniformly spaced beams. Conclusion: The EUD‐based function is a general approach for angular ranking and allows us to identify the potentially good and bad angles for clinically complicated cases. The ranking can be used either as a guidance to facilitate the beam placement or as prior information to speed up the beam configuration optimization.
WE‐E‐E‐611‐01: Introduction — Goals
Authors: Kelsey C
Published: June 2005

Purpose: To introduce the purpose and topics of the Continuing Education Symposium “Teaching of Physics to Radiology Residents” Method and Materials: The Symposium consists of discussions of A) What physics instruction is attempting to accomplish; B) Where we are now in this endeavor. C) How Physics teaching can be improved; D) How can we measure our success and E) to provide a list of resources and aids physics teaching. The discussions will be based on the premise that the purpose of every teaching program is to provide the Radiology resident with a solid physics foundation both to understand and utilize the technology in practice 25 years from now, and to pass the ABR examination. A look at current and previous physics teaching practices and results will put today's discussions in perspective. Like it or not, most residents will take the ABR examination in their first year. There is a fundamental core base of knowledge including signal to noise effects on images, biologic effects of radiation, sources of artifacts which must be included in any physics curriculum. Questions regarding the depth and breadth of the physics curriculum will be reexamined. The use of computer and web based instruction will be discussed. Results: The results of this symposium are designed to assist current instructors of physics to be aware of changes in the expectations of our customers Conclusion: There are many challenges and opportunities facing today's physics instructors. The teaching of Radiology Residents may be improved through a review of what is being taught both in breadth and depth of material and the use of web based resources.
WE‐A‐I‐618‐01: Recent Advances in Digital Mammography
Authors: Yaffe M
Published: June 2005

Purpose: To familiarize the participants with new developments and applications related to digital mammography. Method and Materials: The ACRIN DMIST results are about to be released and it is expected that a benefit will be demonstrated in terms of the accuracy of digital mammography relative to film mammography. Further technical development in acquisition and display technology will improve the efficiency with which digital mammography can be performed. Additional and possibly larger benefits are likely to come from new applications, including computer‐assisted detection and diagnosis (CAD), tomosynthesis, telemammography, contrast imaging, interventional procedures and risk assessment. These will all be made possible or facilitated by the precise acquisition of mammographic images in digital form. For example, CAD can improve the accuracy and consistency of mammographic interpretation by emulating a second reader. Telemammography can improve access to high‐quality mammography in underserved areas. The problem of reduced accuracy due to the complexity of overlying fibroglandular tissue structures in the dense breast can be addressed by tomosynthesis, which simplifies the image by reconstructing individual tomographic slices. Alternatively, imaging of the effects of tumor angiogenesis can be accomplished by subtraction techniques using intravenous contrast media. This can not only improve conspicuity of lesions, but also better reveal the extent of disease. The risk of breast cancer is highly associated with mammographic density. By quantifying density, risk can be estimated and strategies for screening optimized. In the future, tracking of density may have a role in breast cancer prevention by providing a method for monitoring interventions designed to reduce risk. Conclusion: The benefits of digital mammography are likely to extend in several important directions. Conflict of Interest: Martin Yaffe's laboratory has collaborative research agreements with GE Healthcare and with Fischer Imaging on topics related to digital mammography. Dr. Yaffe also conducts research with R2 Technologies and is on the Scientific Advisory Board of XCounter and ART.
SU‐DD‐A3‐04: Strategies for Respiratory‐Compensated Treatment of Lung Lesions
Authors: Smith V , Chuang C , Petti P , Larson D
Published: June 2005

Purpose: The CyberKnife Synchrony system allows respiratory motion compensated treatment of lung lesions implanted with fiducials, using a model of the relative motion of the fiducials and infrared diodes on the chest. Often implantation of fiducials in the lesion is not feasible because of the potential for pneumothorax. We compare the following two alternative strategies

1. Synchrony treatment with fiducials in the anterior chest wall

2. Non‐Synchrony treatment with fiducials in the posterior chest wall

Method and Materials: The lung lesion patients were scanned using a GE Lightspeed Multi‐Slice scanner to obtain 300 1.25mm thick slices through the area of interest during one breath‐hold. This was performed three times covering full inspiration, full expiration, and mid‐inspiration. Fiducials were implanted percutaneously in the anterior and posterior chest wall. The lesion and position of the fiducials were delineated on all three sets of CT scans. If the motion of the lesion tracked the motion of the anterior chest wall fiducials, then a Synchrony plan was developed to treat the lesion as drawn on the mid‐inspiration CT scan. If the lesion motion did not track with the anterior chest wall fiducials then a non‐Synchrony plan was developed that treated the lesion as seen on all three sets of CT scans using the fiducials in the posterior chest wall for tracking. Results: Using anterior chest wall fiducials, the lesion motion tracked to within 1–2mm in X and Y, and 5–6mm in Z. The target was extended in Z to accommodate this. For non‐Synchrony treatments the target volumes increased by 60 to 75% and the prescription isodose volumes increased by 65 to 90%. Conclusion: The treatment of lung lesions presents a difficult challenge especially if fiducials cannot be implanted in the lesion to allow full Synchrony treatment, but the techniques described will still allow treatment.
MO‐B‐I‐618‐02: Overview of Digital Detector Technology
Authors: Seibert J
Published: June 2005

There are various technologies available for the acquisition and display of digital radiographic images. A division has historically existed between “computed radiography” (CR) using photostimulable storage phosphors placed in a cassette holder with subsequent processing in a reader, and “direct radiography” (DR) using a detector with integrated electronics and direct readout and image display. In 2005, these distinctions are less obvious, as some storage phosphor (PSP) devices are automated with direct image display, and some direct flat‐panel devices are used like a portable cassette. Generally speaking, rather than distinguishing digital detectors based on “CR versus DR”, consideration of cassette versus cassetteless digital radiography is perhaps warranted as the technology advances. Besides the venerable cassette‐based PSP detector and plate reader for large field of view imaging (35 × 43 cm), digital detector technologies now available include PSP line‐scan systems in a cassetteless enclosure, optically coupled CCD‐camera systems, fiber‐optically coupled slot‐scan CCD array detectors, indirect x‐ray conversion scintillators and thin‐film‐transistor (TFT) photodiode arrays, and direct x‐ray conversion semiconductors layered on TFT detector arrays. Dedicated digital mammography detectors use similar technologies, with appropriate tuning for resolution and speed. Detective quantum efficiency measurements, equipment specifications, unique acquisition techniques (e.g., digital tomosynthesis and dual energy radiography), PACS/RIS integration and quality control issues are reviewed in the presentation.

Educational Objectives:

1. To describe digital radiography in general terms, and compare with screen‐film detectors

2. To understand acquisition and information flow of digital radiography devices

3. To compare cassette and cassetteless operation in terms of resolution, dose efficiency and signal to noise ratio

4. To describe new data acquisition and image processing techniques

5. To consider PACS/RIS interface and design features for digital radiography
MO‐B‐T‐6E‐01: Fundamental Issues in IMRT Treatment Planning
Authors: Xia P
Published: June 2005

Inverse planning in intensity‐modulated radiotherapy (IMRT) drastically changes our thinking process in treatment planning because of using computer optimization. Unlike conventional forward planning, which highly depends on the geometric relationship between the tumor and the surrounding normal tissues, inverse planning critically depends on the specification of dose constraints to the target tumor and sensitive structures. For a particular inverse planning system, one has to have a good understanding of the inverse planning system and a good intuition about the relationship between the dose constraints and the resulting dose distributions. This review course session will focus on fundamental issues in IMRT treatment planning. We will try to answer the following questions: What are the basic components of commercial IMRT treatment planning systems, and how do they work? What is typical behavior of an IMRTP system? How can the user systematically search for a proper dose constraint for a specific disease site? How does the planner know when to quit trying to improve the plan? Lastly, to what extent and how can the typical problems with generated plans be ameliorated? Issues specific to head and neck and prostate IMRT treatment planning will be discussed.

Educational Objectives:

1. To understand the basic components of commercial IMRT treatment planning systems;

2. To obtain a good intuition about the relationship between the dose constraints and the resulting dose distributions;

3. To understand methods for developing class solutions for specific disease sites to streamline the planning process;

4. To understand special clinical issues related to IMRT treatment planning.

Research is supported by Siemens and Prowess.
TU‐A‐I‐611‐01: Effect of Scan Parameters in Cardiac Imaging with MDCT
Authors: Mahesh M
Published: June 2005

Cardiac imaging has become a reality with the introduction of multiple‐row detector computed tomography (MDCT) technology. Rapid evolutions in multiple row detectors ranging from 4 to 64 rows have led to the progression towards isotropic resolution imaging. This has become possible with improved technical factors such as sub‐millimeter spatial resolution in z‐direction (< 1mm), shorter scan time (< 400 ms), high temporal resolution (< 250 ms) and fast reconstruction of multiple data sets at various intervals in the cardiac cycle yielding larger 3D image data sets. Recently CT imaging, especially cardiac imaging is not confined only to conventional imaging areas such as Radiology but is also performed outside the conventional imaging areas such as Cardiology. In such cases, medical physicists often become the conduit between imaging and non‐imaging areas in assisting the clinicians to understand key features of MDCT. Therefore, it is critical for the medical physicists to become familiar with the various scan parameters and how they influence the overall image quality, so that he or she can provide valuable contributions towards developing appropriate scan protocols, developing strategies for radiation dose reductions and many other aspects. CT image quality in general is influenced by a variety of scan parameters such as kVp, mAs, pitch, image noise, slice thickness, reconstruction algorithms etc. With cardiac CT imaging in mind, the presentation will discuss the effect of various scan parameters and how it affects the radiation dose and image quality.

Educational Objectives:

1. To become familiar with the advantages and disadvantages of various MDCT data acquisition modes.

2. To describe the effects of scan parameters on image quality and patient radiation dose.

3. To become familiar with spatial, temporal resolution and other key requirements in cardiac imaging.

4. To illustrate the image quality requirements in select clinical imaging sequences.
TU‐A‐T‐6E‐01: Patient QA
Authors: Ramsey C , Mahan S
Published: June 2005

The number of patients treated with Intensity Modulated Radiation Therapy (IMRT) has grown dramatically over the past five years. Recent clinical studies have shown that IMRT has the potential to improve outcomes for multiple disease sites and pathologies. However, the clinical successful or failure of each individual institution's IMRT program is dependant on the correct delivery of the 3D dose distributions calculated by the planning system (Planned Dose) to the correct location in the patient (Delivered Dose). There are many sources for errors that can arise during IMRT planning and delivery, but it is ultimately the responsibility of the Medical Physicist to ensure that the Planned Dose “agrees” with the Delivered Dose. Unlike conventional and 3D conformal radiotherapy, IMRT plans must be verified for each individual patient because of the many sources of potential error. The difference between Planned Dose and Delivered Dose (i.e. Error) in IMRT can originate from at least three different sources: 1.) The Treatment Planning Model, 2.) Treatment Delivery Mechanics, and 3.) Time‐Dependant Target/Tissue Positioning. The only method for determining the cumulative effect of all these potential sources of error is to measure the entire delivery sequence on the linear accelerator for each patient. Patient‐Specific IMRT quality assurance (QA) measurements can be classified into three levels. Level I measurements are taken using film, diode arrays, electronic imaging devices, etc. The measurement device(s) are typically placed at depth in water‐equivalent material. Level II measurements are taken with a phantom that moves to simulate intra‐fraction motion (such as respiration motion). These measurements are typically made with film, diodes, and/or ionization chambers. Level III measurements are performed using daily CT imaging acquired on the delivery system (CT‐on‐Rails, Cone‐Beam CT, Megavoltage CT, etc…). Electronic detector data acquired during treatment delivery is then combined with the daily CT images to reconstruct the doses delivered to the patient. This presentation will discuss commercially available dose measurement tools, phantoms, and techniques for performing Level I and II patient‐specific IMRT quality assurance. The current status of research and development in Level III IMRT quality assurance will also be discussed. Issues associate each technique will be discussed and clarified with practical examples. Recommendations will be presented for acceptable tolerances and testing frequencies.

Educational Objectives:

1. To understand the issues surrounding patient‐specific IMRT quality assurance

2. To understand the difference between patient‐specific QA techniques

3. To identify potential sources of errors in IMRT quality assurance

4. To understand the impact of target localization and patient positioning on IMRT
TU‐C‐T‐6C‐03: Simplifying IMRT Plans Through Efficient Segmentation
Authors: Siochi R
Published: June 2005

Purpose: To analyze the various methods for creating efficient leaf sequences for an IMRT plan, subject to MLC constraints. Method and Materials: An IMRT treatment plan can be simplified at several stages. Careful beam placement can lead to simpler intensity maps. The choice of the dose optimization engine, as well as the spatial and intensity resolution can also affect map complexity. To further reduce the total number of segments and monitor units, an optimal leaf sequence must be used. This reduction is accomplished by a combination of segment extractions and sweeps. The algorithms involve the determination of MLC shape and MUs. Some algorithms use predefined MUs according to a sequence (e.g. Power of two, Half‐Maximum, Triangular numbers), while others optimize the MU selection by evaluating the complexity of the difference between the intensity map and the segment being considered. The selection of the MLC shape can also be achieved through a predetermined geometric process (e.g. largest area, largest area with maximum intensity, leftmost segment, graph theory) or by minimizing the complexity of the difference map. In this step, the machine constraints and the desire to reduce the tongue and groove effect are considered, as they can dramatically increase the number of segments and MUs. Once the leaf sequences have been generated, an examination of the plan may reveal degradation in the DVHs, and appropriate leaf‐sequence modifications can help restore the plan quality. Results: Plans with beams that have minimal critical structure involvement and modulate with more leaves yield less segments and MUs. Optimizers that use gradient methods rather than simulated annealing tend to reduce modulation scaling factors by a factor of 2 to 3. A map resolution of 10 to 15 intensity levels and a leaf spacing of 6 mm produce a reasonably efficient plan without sacrificing its quality, provided that the leaf sequence is optimized by minimizing the difference map complexity. The collision constraint increases the number of segments and MUs by about 20%, and various levels of tongue and groove correction provide an additional increase of about 20 to 30%. Post processing can remove low weight segments, and leaf positions can be adjusted to eliminate hot and cold spots. Conclusion: In order to simplify an IMRT plan, one must take advantage of all the options that affect the leaf sequencing process, including beam placement, map resolution, segmentation algorithm choice and post‐processing.

Educational Objectives:

1. To understand the importance of beam selection and set‐up prior to plan optimization.

2. To know the impact of map resolution set‐up on complexity and the achievement of clinical goals.

3. To know the limitations and strengths of the various algorithms for leaf sequencing and how to choose the appropriate one.

4. To become familiar with the post‐processing of leaf sequences.
TU‐D‐I‐609‐04: Effect of Reader Variability On Improvements in Breast Cancer Detection Rates
Authors: Jiang Y , Miglioretti D , Metz C , Schmidt R
Published: June 2005

Previous investigations have demonstrated variability among radiologists in the interpretation of screening mammograms. This presentation will discuss the extent of this variability and its effect on clinical trials that compare the conventional screening‐film mammography and new technologies such as full‐field digital mammography (FFDM) and computer‐aided detection (CADe). We will present data on breast cancer detection rates at the conventional screen‐film mammography of over 500 practicing community radiologists in the US. By postulating a large improvement in the cancer detection rate that would be achieved with a hypothetical new technology, we predicted the cancer detection rate that would be observed in a hypothetical clinical trial comparing the new technology and the conventional screen‐film mammography. Despite a large postulated improvement in the cancer detection rate, it is difficult for clinical trials to demonstrate this improvement. Variability among radiologists in the observed cancer detection rates is an important cause for this difficulty. Clinical trials need to include large samples of radiologists in addition to large samples of patients to achieve sufficient statistical power to detect an improvement in the breast cancer detection rate in screening mammography. FFDM and CADe clinical trials, many of which appear to lack statistical power, will be discussed.

Educational Objectives:

1. To understand the sources and extent of variability in radiologists' breast cancer detection rates in screening mammography.

2. To understand the impact of reader variability on clinical trials that compare imaging technologies in screening mammography.

3. To understand the need to sample a large number of radiologists in addition to sampling a large number of patients to demonstrate an improvement in breast cancer detection rate in screening mammography.

4. Financial Disclosure: C Metz and R Schmidt are shareholders of R2 Technology, Inc.
WE‐A‐I‐617‐01: PET/CT Attenuation Correction and Image Fusion
Authors: Carney J
Published: June 2005

PET/CT scanners provide intrinsically co‐registered CT and PET images in a single scan session, which can then be viewed together as a fused image showing both anatomy and function. This in particular allows for excellent localization of features in the PET image. Furthermore, with the CT scan performed prior to the PET scan, routine attenuation correction of the acquired PET data is possible. The use of CT images for this purpose in PET/CT scanners has the advantages of shorter scan times and effectively noiseless transmission images as compared to the transmission scans that are used in standalone PET cameras. This does however require the non‐trivial step of transforming the CT images to 511 keV attenuation images that are reprojected to obtain the desired attenuation correction factors. This lecture will describe the use of CT images for attenuation correction in PET/CT scanners and address the advantages and challenges of this procedure and the use of fused images in the clinical environment. Improved attenuation correction procedures to take account of different kVp settings in the CT protocol, as well as the particular challenges in emerging applications such as cardiac PET/CT will be addressed.

Educational Objectives:

1. Review the principles of attenuation correction in PET and the implementation of this procedure using CT images in PET/CT imaging.

2. Understand the particular challenges of CT‐based attenuation correction, including the choice of respiration protocols and other problems of patient motion, the use of CT contrast agent, and the presence of foreign objects in the body.

3. Review the advantages of image fusion in PET/CT, and the clinical challenges of registering the CT and PET imaging modalities that remain, such as respiration.
WE‐B‐I‐617‐01: Optimizing MRI Protocols — Clinical Practice and Compromises
Authors: Clarke G
Published: June 2005

Modern MRI systems are extremely flexible so that optimal usage requires a solid understanding of the physics of the basic processes involved. In the end, determination of the “best” protocol to address a clinical problem requires careful consideration of trade‐offs between image contrast, signal‐to‐ noise ratio (SNR), spatial resolution, temporal resolution and patient safety. The major factors in considering MR image contrast are the relaxation times: T1 & T2, magnetization transfer mechanisms, physiological motion and the radio frequency (rf) pulsing scheme. The most important issues for SNR are field strength, rf coil properties, voxel size, and receiver bandwidth. Factors pertinent to spatial resolution include magnetic field homogeneity, gradient strength, matrix size, slice thickness and field of view. Imaging speed is determined by gradient slew rate, signal digitization rate, number of slices, parallel imaging mode & signal‐to‐ noise ratio. Patient safety issues are related to patient size, field strength, rf pulsing method and gradient slew rate. In this presentation the basic relationships amongst all of these parameters in MRI will be reviewed and their interactions discussed. For instance, the long TR values required for strongly T2‐weighted images is an example of how contrast requirements can limit imaging speed. High‐speed T2‐ weighted images can be obtained using Fast Spin Echo strategies, but only by compromising spatial resolution and the number of slices while increasing rf heating. Specialized clinical imaging protocols that push the envelope in several of these general areas will also be examined. The use of three‐dimensional MR angiography to maximize contrast while preserving good SNR at high imaging speeds will be explored. The conditions under which certain signals from particular types of tissues, such as adipose or cerebrospinal fluid, can be entirely eliminated will be surveyed. Roles for the use of exogenous agents to alter tissue contrast shall also be reviewed. Trade‐offs required to image the heart's motion in real time will be appraised. The implications of rf heating, as measured by the specific absorption rate, will also be considered. At the end of this presentation the attendee shall:

1. understand the primary types of image contrast used in clinical MRI and the relationships between pulse timing parameters and relaxation times of tissue on the acquired MRI signal.

2. know how to consider the interactions between SNR, spatial resolution and imaging speed and their relative weighting in defining image quality for a variety of clinical situations.

3. be conversant with circumstances under which patient physiology and magnet field strength may require modification of image acquisition parameters to achieve optimal image quality.
WE‐C‐P‐618‐01: Radiological Awareness Training for First Responders and Health Care Providers
Authors: Adair J
Published: June 2005

The Washington State Department of Health's Division of Environmental Health has been actively involved in providing radiological training for a broad spectrum of first responders and health care providers since 2003, through its Office of Radiation Protection (ORP). Much of the training is given by ORP staff, which also coordinates training given by outside experts. The topics include response to weapons of mass destruction (U.S. Department of Justice) and radiation emergency medical care (U.S. Department of Energy). Attendees include local public health, doctors and nurses, the Federal Emergency Management Agency, the U.S. Navy, emergency medical technicians, firefighters, hazmat responders, and law enforcement. Classes are customized for each profession, are unique and interactive, and include real radioactive materials at a mock incident scene to incorporate a sense of believability. The Department of Health's goal is to educate Washington's first responders and health care providers about the health risks from incidents involving radioactivity, both to the victims and to themselves.

Educational Objective:

1. To review the current NRC Part 35 training and experience requirements.
WE‐D‐T‐6C‐03: Development of Image Software Tools for Radiation Therapy Assessment
Authors: Cao Y
Published: June 2005

There has been extensive recent interest in the potential power of emerging imaging tools for early prediction of therapy effectiveness, both related to tumor control and normal tissue damage. These prognostic indicators are the results of combining improved imaging hardware, specialized scanning protocols, and advanced image processing and analysis paradigms. In order to study and eventually use these tools routinely in the radiotherapy process, serious consideration needs to be given to the software environment necessary for proper data collection and analysis ties to individual patients' treatments. Imaging for therapy assessment (IAT) presents a multidimensional information environment, requiring data from different imaging modalities and acquisition methods, as well as handling temporal data series, combined over short (breathing, dynamic contrast) and long (temporal changes over weeks of treatment) time periods. The information needed for relating these data sets for analysis (non‐rigid transformations, proper labeling of studies to measurement states) exceeds the capacities of existing DICOM standards. The extraction of analyzed information and relation to regional (radiation) dose should be multidimensional, and not restricted to voxel‐specific regions. Examples of imaging studies underway for therapy assessment will be presented. Software requirements will be demonstrated through an example system currently in use to support clinical trials at the University of Michigan. This system was designed around the unique needs of IAT, and is able to combine information from multiple sources (e.g., MRI, MRS, CT, PET, radiation dose) and time periods in an intuitive interface. This system has been used for studies of blood flow and volume, regional venous perfusion, vascular permeability, water diffusion, metabolite, and local contrast enhancement for high dose radiotherapy trials in the brain, lung, and liver to date.

Educational Objectives:

1. Understanding the unique needs related to imaging for assessment of radiation therapy.

2. Understanding the required tools beyond those found in a typical treatment planning system

3. Understanding a common ground needed for combining efforts of imaging physicists, radiation physicists, physicians and statisticians.

4. Understanding opportunities for novel paradigm and algorithm development
On the relationship between signal bandwidth and frequency correlation for ocean surface forward scattered signals
Authors: Culver R. Lee , Bradley David L.
Published: June 2005

The relationship between the bandwidth of a signal and the correlation of that signal with its ocean surface reflected arrival, a quantity we term frequency correlation, has been investigated experimentally and compared with two theories. Decorrelation of wideband surface scattered signals is a direct consequence of time spread. The acoustic measurement utilized a very short pure tone signal, from which time spread has been estimated, and four broadband signals with different bandwidths, for which correlation with the transmitted signal has been measured. An environment-driven model developed by Dahl was used to predict time spread, which agreed favorably with our time spread measurements. The model was also employed in two theories that predict frequency correlation. The first, a theory published by Reeves in 1974, is based upon the ratio of signal temporal resolution to total time spread. This theory compared well with our measurements for 1 kHz bandwidth signals, but is not applicable for signal bandwidths greater than about 2 kHz. The second, a theory developed by Ziomek, models ocean acoustic propagation as transmission through a linear system. This theory agreed well with our frequency correlation measurements for signal bandwidths of 1–22 kHz.
Modeling the articulatory space using a hypercube codebook for acoustic-to-articulatory inversion
Authors: Ouni Slim , Laprie Yves
Published: June 2005

Acoustic-to-articulatory inversion is a difficult problem mainly because of the nonlinearity between the articulatory and acoustic spaces and the nonuniqueness of this relationship. To resolve this problem, we have developed an inversion method that provides a complete description of the possible solutions without excessive constraints and retrieves realistic temporal dynamics of the vocal tract shapes. We present an adaptive sampling algorithm to ensure that the acoustical resolution is almost independent of the region in the articulatory space under consideration. This leads to a codebook that is organized in the form of a hierarchy of hypercubes, and ensures that, within each hypercube, the articulatory-to-acoustic mapping can be approximated by means of a linear transform. The inversion procedure retrieves articulatory vectors corresponding to acoustic entries from the hypercube codebook. A nonlinear smoothing algorithm together with a regularization technique is then used to recover the best articulatory trajectory. The inversion ensures that inverse articulatory parameters generate original formant trajectories with high precision and a realistic sequence of the vocal tract shapes.
Effects of informational maskers within and across trials
Authors: Lutfi Robert A. , Alexander Joshua M.
Published: June 2005

The across-trial effect of maskers in conditions of informational masking was evaluated from performance on occasional trials in which the signal was presented alone. For 6 of 12 listeners participating in the study, a significant number of errors were obtained on signal-alone trials; in some cases equivalent to that signal+masker trials. On immediately preceding trial blocks for which there were no intervening maskers, performance for these signals was perfect. The results indicate that informational maskers can have a significant effect on signal threshold, both within and across trials.
Perceptual compensation for effects of reverberation in speech identification
Authors: Watkins Anthony J.
Published: June 2005

Listeners were asked to identify modified recordings of the words “sir” and “stir,” which were spoken by an adult male British-English speaker. Steps along a continuum between the words were obtained by a pointwise interpolation of their temporal-envelopes. These test words were embedded in a longer “context” utterance, and played with different amounts of reverberation. Increasing only the test-word’s reverberation shifts the listener’s category boundary so that more “sir”-identifications are made. This effect reduces when the context’s reverberation is also increased, indicating perceptual compensation that is informed by the context. Experiment 1 finds that compensation is more prominent in rapid speech, that it varies between rooms, that it is more prominent when the test-word’s reverberation is high, and that it increases with the context’s reverberation. Further experiments show that compensation persists when the room is switched between the context and the test word, when presentation is monaural, and when the context is reversed. However, compensation reduces when the context’s reverberation pattern is reversed, as well as when noise-versions of the context are used. “Tails” that reverberation introduces at the ends of sounds and at spectral transitions may inform the compensation mechanism about the amount of reflected sound in the signal.
Directional radiation pattern in structural–acoustic coupled system
Authors: Seo Hee-Seon , Kim Yang-Hann
Published: June 2005

In this paper we demonstrate the possibility of designing a radiator using structural-acoustic interaction by predicting the pressure distribution and radiation pattern of a structural-acoustic coupling system that is composed by a wall and two spaces. If a wall separates spaces, then the wall’s role in transporting the acoustic characteristics of the spaces is important. The spaces can be categorized as bounded finite space and unbounded infinite space. The wall considered in this study composes two plates and an opening, and the wall separates one space that is highly reverberant and the other that is unbounded without any reflection. This rather hypothetical circumstance is selected to study the general coupling problem between the finite and infinite acoustic domains. We developed an equation that predicts the energy distribution and energy flow in the two spaces separated by a wall, and its computational examples are presented. Three typical radiation patterns that include steered, focused, and omnidirected are presented. A designed radiation pattern is also presented by using the optimal design algorithm.
Characteristics of distortion product otoacoustic emissions in the frog from L1,L2 maps
Authors: Meenderink Sebastiaan W. F. , van Dijk Pim
Published: June 2005

For a given set of stimulus frequencies (f1,f2), the level of distortion product otoacoustic emissions (DPOAEs) varies with the levels of the stimulus tones. By variation of the stimulus levels, L1,L2-maps for DPOAEs can be constructed. Here, we report on L1,L2-maps for DPOAEs from the frog ear. In general, these maps were similar to those obtained from the mammalian cochlea. We found a conspicuous difference between the equal-level contour lines for low-level and high-level DPOAEs, which could be modeled by a saturating and an expansive nonlinearity, respectively. The transition from the high-level to the low-level response was accompanied by a DPOAE phase-change, which increased from 0 to πrad with increasing frequency. These results suggest that in the frog low-level and high-level DPOAEs are generated by separate nonlinear mechanisms. Also, there was a conspicuous difference in the growth of the low-level emissions from the two anuran auditory papillae. In the basilar papilla, this growth was expansive for the lowest stimulus levels and saturated for intermediate levels. This is consistent with the behavior of a Boltzman nonlinearity. In the amphibian papilla this growth was compressive, suggesting the additional effect of a compressive amplification mechanism on the generation of DPOAEs.
Remote sensing of sediment density and velocity gradients in the transition layer
Authors: Holland Charles W. , Dettmer Jan , Dosso Stan E.
Published: June 2005

The geoacoustic properties of marine sediments, e.g., bulk density and compressional velocity, commonly exhibit large variations in depth near the water–sediment interface. This layer, termed the transition layer, is typically of O(10−1–100)m in thickness. Depth variations within the transition layer may have important implications for understanding and modeling acoustic interaction with the seabed, including propagation and reverberation. In addition, the variations may contain significant clues about the underlying depositional or erosional processes. Characteristics of the transition layer can be measured directly (e.g., coring) or remotely. Remote measurements have the advantage of sampling without disturbing the sediment properties; they also have the potential to be orders of magnitude faster and less expensive than direct methods. It is shown that broadband seabed reflection data can be exploited to remotely obtain the depth dependent density and velocity profiles in the transition layer to high accuracy. A Bayesian inversion approach, which accounts for correlated data errors, provides estimates and uncertainties for the geoacoustic properties. These properties agree with direct (i.e., core) measurements within the uncertainty estimates.
Gender and speaker identification as a function of the number of channels in spectrally reduced speech
Authors: Gonzalez Julio , Oliver Juan C.
Published: June 2005

Considerable research on speech intelligibility for cochlear-implant users has been conducted using acoustic simulations with normal-hearing subjects. However, some relevant topics about perception through cochlear implants remain scantly explored. The present study examined the perception by normal-hearing subjects of gender and identity of a talker as a function of the number of channels in spectrally reduced speech. Two simulation strategies were compared. They were implemented by two different processors that presented signals as either the sum of sine waves at the center of the channels or as the sum of noise bands. In Experiment 1, 15 subjects determined the gender of 40 talkers (20 males + 20 females) from a natural utterance processed through 3, 4, 5, 6, 8, 10, 12, and 16 channels with both processors. In Experiment 2, 56 subjects matched a natural sentence uttered by 10 talkers with the corresponding simulation replicas processed through 3, 4, 8, and 16 channels for each processor. In Experiment 3, 72 subjects performed the same task but different sentences were used for natural and processed stimuli. A control Experiment 4 was conducted to equate the processing steps between the two simulation strategies. Results showed that gender and talker identification was better for the sine-wave processor, and that performance through the noise-band processor was more sensitive to the number of channels. Implications and possible explanations for the superiority of sine-wave simulations are discussed.
Ultrasonic wave propagation across a thin nonlinear anisotropic layer between two half-spaces
Authors: Sadler Jeff , O’Neill Brian , Maev Roman Gr.
Published: June 2005

Boundary conditions and perturbation theory are combined to create a set of equations which, when solved, yield the reflected and transmitted wave forms in the case of a thin layer of material that is perfectly bonded between two isotropic half-spaces. The set of perturbed boundary conditions is created by first using the fully bonded boundary conditions at each of the two interfaces between the thin layer and the half-spaces. Then, by restricting the layer’s thickness to be much smaller than an acoustic wavelength, perturbation theory can be used on these two sets of boundary equations, producing a set of equations which effectively treat the thin layer as a single interface via a perturbation term. With this set of equations, the full range of incident and polar angles can be considered, with results general enough to use with a layer that is anisotropic, nonlinear, or both anisotropic and nonlinear. Finally the validity of these equations is discussed, comparing the computer simulation results of this theory to results from standard methods, and looking at cases where the results (or various properties of the results) are known or can be predicted.
Experiments of high-amplitude and shock-free oscillations of air column in a tube with array of Helmholtz resonators
Authors: Masuda M. , Sugimoto N.
Published: June 2005

This experimental study is made to verify the weakly nonlinear theory for high-amplitude and shock-free oscillations of an air column developed in the previous paper [Sugimoto et al., J. Acoust. Soc. Am., 114, 1772–1784 (2003)]. The experiments use a new tube and resonators designed so as to not only avoid higher harmonic resonances and evanescences but also reduce the values of the coefficient of Q in the amplitude equation, and a rubber diaphragm sandwiched by circular plates to drive the air column. The steady-state pressure field in the tube and in the cavities of the resonators is measured, from which Fourier coefficients are obtained. In spite of nonlinearity, higher harmonics are suppressed significantly as designed, and the frequency response measured shows quantitatively good agreement with the one predicted up to about 170dB (SPL). The first harmonics and the nonoscillatory component in the pressure field are well predicted, though the second harmonics show a quantitative discrepancy with the theory. In view of the good agreement of the frequency response, it is concluded that the theory is valid and useful enough to provide guidelines in designing the tube with the array of resonators.
Airflow noise in telephone handsets and methods for its reduction
Authors: Stinson Michael R. , Daigle Gilles A. , Quaroni John F.
Published: June 2005

The noise in a telephone handset produced by the bursts of airflow that accompany plosive sounds such as a “p” or “t” has been investigated. Measurements have been made on a series of modified handsets, using various arrangements of ports and tubes between microphone and the exterior of the telephone mouthpiece. A narrow stream of air was used to probe the mouthpiece and the signal picked up by the microphone recorded. The use of one, two, and multiple exterior holes was considered. Two-hole approaches alleviate the static pressure buildup that occurs when a single microphone hole is used and in many cases they result in reduced noise generation; for some directions of incident airflow, though, noise can be markedly increased. This was found to be due to interaction between intersecting streams of air. By using a large number of small (less than 0.5mm) exterior holes, the airflow noise can be reduced by over 30dB for all incident directions of airflow. It is also beneficial to ensure that none of the exterior holes is in direct line with the sound tube leading to the microphone.