bluuebunny/crossref_metadata_2025_split huggingface dataset:
WE‐A‐224C‐1: Daily Localization III: Tomotherapy
Authors: Meeks S 
Published: July 2006

Helical tomotherapy using the Hi‐ART II is analogous to helical CT imaging where the gantry and the couch are in simultaneous motion. Hence, beam delivery is continuous over all 360 in transverse planes about the patient. Temporal beam modulation is achieved by using a binary multi‐leaf collimator. In addition to its ability to deliver IMRT, the Hi‐ART II has the ability to obtain helical megavoltage CT (MVCT) images. These MVCT images have adequate spatial and contrast resolution for image guidance, and also for identification of many soft‐tissue structures. The incorporation of daily three dimensional soft‐tissue imaging into the radiotherapy process also enables dose recalculation and periodic evaluation of the treatment delivery during a course of radiotherapy. Hence, the subsequent treatment delivery can be modified using a systematic feedback of the geometric and dosimetric information in the previous fractions. This requires many components as feedback, including CT guidance to achieve soft tissue localization, dose recalculation, dose accumulation, treatment evaluation, re‐contouring, and re‐optimization.This lecture will provide an overview of the physical characteristics of the Hi‐ART II, acceptance testing and commissioning, image quality tests, image registration, basic quality assurance, and an overview of clinical applications. Finally, system limitations and future developments will be addressed.Educational Objectives1. Understand the basics concepts of helical tomotherapy.2. Understand the basic QA requirements and system limitations association with helical tomotherapy.3. Understand the workflow and issues related to clinical applications of helical tomotherapy, including acquisition, reconstruction, registration and patient alignment.4. Understand the possibilities of daily soft‐tissue imaging for patient alignment and evaluation of treatment accuracy.
WE‐A‐230A‐01: NCI Talk On Funding
Authors: Deye J 
Published: July 2006

The National Institutes of Health is composed of 27 Institutes and Centers, with the National Cancer Institute (NCI) being the oldest and the National Institute of Biomedical Imaging and Bioengineering (NIBIB) the youngest. Medical physicists have a major stake in the pursuits of these institutes since they have a large influence on everything from the research that is funded to the clinical protocols and methods that are employed in both therapy and diagnosis.Yet these institutes are themselves experiencing very significant extrinsic and intrinsic factors that affect the ways that they interact with the medical community. A partial list would include: the NIH budget in the post‐doubling period; the creation of NIH‐wide Roadmap Initiatives and NCI‐wide Enterprise Initiatives; the adaptation of the NIBIB to the other Institutes; budget set‐asides for the war on terrorism; the dawning of translational research methods; the blurring of boundaries between disciplines; and an increasing role for industry, to name a few.The ramifications of these changes will be explored with regard to the institute budgets, priorities and relationships; and the presentation will outline some of the current research agendas and the mechanisms which are used to implement them.Educational Objectives:1. Understand the structure and processes involved in NIH funded research.2. Understand the issues surrounding the NIH budget.3. Understand how to develop a research proposal.
WE‐B‐330D‐01: Digital Image Processing in Radiography
Authors: Flynn M 
Published: July 2006

In digital radiography, the transmitted x‐ray beam recorded by a detector is first recorded as raw data related to the energy deposited in the sensitive region of each pixel. Raw data is then transformed to a ‘For Processing’ image by correcting for gain non‐uniformity and bad pixels. Finally, the ‘For Processing’ image is transformed to a ‘For Presentation’ image that is intended for viewing.The processes used in the presentation transformation have become an ssential element of image quality. These processes include exposure recognition, grayscale rendition, edge restoration, noise reduction, and broad area equalization. The numeric methods used to implement these processes will be reviewed and related to current commercial image processing solutions.Educational Objectives:1. Understand how image processing is integrated. into a sequence of steps used in generating a radiograph.2. Conceptually understand the component processing steps and their effect on image quality.3. Learn how certain commercial systems implement processing.4. Understand how processing can be adjusted by a medical physicist to achieve consistent presentation characteristics.
WE‐C‐330A‐01: Robust Tracking of Interventional Tools Under X‐Ray Fluoroscopy Using Particle Filters
Authors: Siddique S , Hatzinakos D , Jaffray D 
Published: July 2006

Purpose: Motion estimation is an important problem. In diagnostic and therapeutic interventions, intraoperative motion estimation is needed to guide interventional tools with high precision. In radiation therapy, intrafraction motion estimation is essential to improve the precision with which therapeutic radiation is delivered. The purpose of this study is to estimate the pose (location and orientation) of interventional tools such as needles in an X‐ray fluoroscopic sequence using a particle filter. Method and Materials: Tracking Algorithm: The tools were tracked using a particle filter. Two models are of concern in such an implementation — (i) the observation model was defined on the output of an edge detector by taking transverse and longitudinal samples of the tool, and (ii) the dynamic model was assumed to be given by Brownian motion.Experimental Setup: The accuracy of the tracking algorithm was validated on an X‐ray fluoroscopy test bench. A modified anthropomorphic Rando™ phantom was placed in the field‐of‐view in order to emulate the background presented by a patient. Two sites on this phantom were used — the pelvis and the thorax. The pelvis presents a case of low signal while the thorax presents a cluttered background. The tool to be tracked was attached to a linear actuator and moved in known increments while capturing fluoroscopic images. The acquired image sequence was then sampled to generate new image sequences for testing the tracking algorithm. Results: The algorithm was robustly able to track the tool under a low signal in the abdomen, and under dense clutter presented by the ribs in the thorax. The rms error in each case was found to be as little as 0.7mm and 0.12mm, respectively. Conclusion: This study demonstrates the robustness of estimation under noise and clutter that can be achieved when tracking tools in a fluoroscopic sequence using a particle filtering approach.
WE‐C‐330A‐10: Brightness‐Based Methods for Correcting Beam‐Former Sound Speeds
Authors: Al‐Sadah J , Zagzebski J 
Published: July 2006

Purpose: The speed of sound (SOS) varies among patients and spatially within a patient. Differences between the SOS assumed in the beam former and that of tissue defocuses B‐mode images. A global effective SOS value can be chosen to maximize image quality. This study investigates brightness based methods for SOS corrections. Method and Materials: The beam former assumed SOS in a Siemens Antares machine was varied while imaging two phantoms having different SOS's (ATS539‐1440m/s and RMI403‐1540m/s). Three methods were used to quantify resultant image quality changes: visual inspection, zeroth order statistics over a region of interest (ROI) and axial/lateral variation of echo signals arising from discrete reflectors. Peak brightness (PB), mean brightness (MB) and mean of brightness squared (MBS) were measured. Results: Visual inspection showed image sharpness improvement at an appropriate SOS. The optimal SOS values correlate with phantom specifications, but are lower (30–70m/s). Operating conditions affect the optimal SOS. The brightness varies partially due to the fractional overlap of the transmission/reception focal zones, drifting apart with depth.MBS over a ROI proved superior to MB in distinguishing an optimal SOS. Both measures suffered drift problems with SOS for ROI's far from the transmit focus. Including structures in the ROI affects the ability to generate an SOS peak.The lateral extent of a bright spot/glint selected either visually or by a simple search, varies with the assumed SOS. PB and MBS of line signals showed a peak around the optimal SOS. Axial signals are more robust. The maxima at glints result in minima for neighboring axial lines demonstrating good focusing. Conclusions: Visual inspection and glint analysis yield consistent SOS's that improve image quality. SOS accuracy for diagnostic use is limited due to effects of operating conditions of the machine and needs further investigation.
WE‐C‐330D‐02: Image Science and CAD: In Pursuit of a Fundamental Theoretical Basis for CAD Development
Authors: Nishikawa R 
Published: July 2006

Computer‐aided diagnosis is still a very immature field, with very little theoretical framework upon which it is based. This is a major limitation in both developing systems and in evaluating them in a meaningful way. It is clear that in the future CAD will play a greater role in radiology, both as secondary reader and as a primary reader. The current clinical implementation of CAD is as second reader to radiologists. This will shift to CAD being used by a physician assistant and CAD as the primary reader and the radiologist as the secondary reader. Ultimately, CAD will be the only reader, at least for a subset of cases.However, to increase the development and adoption of new CAD systems, the field needs a better fundamental foundation. This foundation will come from several areas. First, as we gain a better understanding of human observers, we can use this information not only to develop more accurate CAD algorithms, but also importantly, to design CAD systems that can be integrated into the radiologists' workflow more fully. Second, models of CAD techniques need to be developed. In analogy to modeling ideal observers and human observers, much can be gained from modeling CAD schemes. Third, a thorough understanding of the interaction between the image and the CAD technique is needed. For example, if the shape of the NEQ curve of the image receptor changes, can we predict how the performance of the CAD technique will change.Medical imaging technology is rapidly changing. The current paradigm for developing CAD systems — try different techniques on hundreds of images — cannot keep pace with these changes, especially as new imaging systems are developed, where clinical images are scarce. Our goal should be to develop the field to the stage where it will be possible to model the imaging system's characteristics and then, guided by models of human observer performance, select from an array of image processing, artificial intelligence and pattern recognition techniques a group of techniques that will produce the optimum CAD system.This talk will present my vision for the future of CAD and what is necessary for the field to make rapid progress.Educational Objectives:1. Discuss future roles of CAD as both a secondary and the primary reader.2. Explain the fundamental limitations of CAD development.3. Discuss one possible approach to overcoming the limitations in the future.
WE‐C‐ValA‐03: The Use of CT Density Changes at Internal Tissue Interfaces to Monitor Respiratory Induced Lung Tumor Motion
Authors: Gaede S , Carnes G , Yu E , Van Dyk J , Battista J , Lee T 
Published: July 2006

Purpose: To describe a non‐invasive method to monitor the motion of internal organs affected by respiration without using external markers or spirometry, to apply the method to construct 4D‐CT datasets, to test the correlation with external markers, and to calculate any time shift between the datasets.Method and Materials: Ten lung cancer patients were CT scanned with a General Electric Fast 4‐Slice CT scanner operating in ciné mode. An external signal was also acquired simultaneously using the Real‐Time Position Management (RPM) Respiratory Gating System (Varian Medical Systems). We retrospectively reconstructed the raw CT data to obtain consecutive 0.5s reconstructions at 0.1s intervals to increase image sampling. We defined regions of interest containing tissue interfaces that move due to breathing on each axial slice and measured the mean CT number as a function of respiratory phase. We constructed 4D‐CT data sets by retrospectively sorting each image set based on the respiratory phase determined by the mean CT number curve. The external marker and tumor motion were directly correlated using the sample coefficient of determination, r2. Any time shift between the two data sets was calculated by shifting the tumor motion curve until r2 was maximized. Results: Only three of the ten patients showed correlation higher than r2=0.80 between tumor motion and external marker position. However, after taking into account time shifts (ranging between 0s and 0.4s) between the two data sets, all ten patients showed correlation better than r2=0.8. Conclusions: 4D‐CT acquisition using an internal method improves the temporal registration of CT images affected by respiratory motion without the need for external markers or spirometry. A non‐invasive method to directly correlate the motion of external markers and internal organs can be used to help guide decisions regarding the validity of the RPM system for respiratory gated radiotherapy on a patient‐specific basis.
WE‐C‐ValA‐06: Characterizing and Modeling Patient Respiratory Patterns for Radiation Therapy
Authors: Repp J , Lu W , Hubenschmidt J , Parikh P , Mutic S , Bradley J , Low D 
Published: July 2006

Purpose: Lung tumor breathing motion is a function of both the breathing depth (tidal volume) and breathing rate (airflow). Treatment planning for lung tumors will require a patient‐specific tumor motion model. An understanding of the patient's typical breathing cycle will be critical to accurate treatment planning predictions for linear‐accelerator gating or tracking. This work examines patient‐breathing characteristics to determine the patterns and stability of the breathing cycle. Method and Materials: A total of 34 patients (with and without lung cancer) were scanned with a previously described 4DCT protocol under synchronized tidal breathing monitoring. We examined the scatter plot of air flow against tidal volume for the entire scan session. A 2D histogram was then generated by calculating the frequency of data points falling into each tidal volume‐airflow window. The 2D histogram depicted the probability that the patient breathed at certain tidal volume and air flow window. We evaluated the breathing consistency of the three patients with multiple scans. Results: There was no significant differences in the breathing period (P=0.11) or in the peak‐to‐peak amplitude (P=0.22) between patients with lung cancers and patients with upper‐abdomen cancers. The 2D histogram revealed two different breathing patterns: patients who spent more time breathing at the end of exhalation (20 patients), exhibiting a characteristic volume‐flow curve, and patients who spent the majority of time inhaling and exhaling (14 patients). The latter patients did not spend any appreciable amount of time between successive breaths. For the three patients with two sessions, the mean frequency difference between corresponding tidal volume‐airflow windows was <0.3%. Conclusion: We characterized patient breathing by examining the tidal volume‐airflow plot and histogram. The results showed two different breathing patterns suggesting that not all patients are appropriate for gated radiotherapy. All three patients showed high consistency in two scan sessions.Supported by NIH R01CA96679.
WE‐C‐224A‐01: Peter Wootton: A Personal and Professional Remembrance
Authors: Kalet I 
Published: July 2006

Peter Wootton was a legendary figure in the field of medical physics. He is known for early work on the foundations of dosimetry, for pioneering neutron therapy, for establishing regional medical physics services in the Pacific Northwest, and for many years leading the medical physics training program at the University of Washington. The American Association of Physicists in Medicine (AAPM) was incorporated in 1965, with Peter as a member of the initial Board of Directors, and signer of the organization's articles of incorporation. He also served a term as AAPM President in 1978. Under his leadership, in the early 1980's the University of Washington acquired, installed and operated what was then the most sophisticated neutron therapy facility in the entire world. This facility, still in service over 20 years later, continues to be state of the art. Peter was a superb teacher, and left a legacy of many M.S., Ph.D. and postdoctoral trainees, of which the author is one. His kind and wise spirit is greatly missed and remembered with awe and appreciation.Educational Objectives:1. Understand the role of Peter Wootton in the development of the field of medical physics.
TH‐A‐224A‐01: QA for Imaging Systems Used for Planning (CT, PET, MR)
Authors: Mutic S 
Published: July 2006

Imaging for radiation therapy treatment planning has different goals than diagnostic imaging. Quality assurance (QA) of imaging devices (CT, PET, MR) which are used for radiation therapy imaging will therefore have different or additional goals compared to QA for diagnostic imaging purposes. Use of PET and MR imaging in radiation therapy is constantly increasing and reliable performance of these imaging modalities is important to avoid potentially significant errors.Quality assurance for CT scanners used for radiation therapy scanning is relatively well established and defined. This process remains to be adequately defined for PET and MR scanners that are used for treatment planning. Evaluation of image quality of CT, PET, and MR scanners is generally adequately addressed by procedures which were established for diagnostic imaging. Design of QA protocols for radiation therapy scanning should be founded on procedures which are used for diagnostic imaging. Evaluation of mechanical accuracy and image spatial integrity is unfortunately not a major concern in diagnostic imaging and these parameters are often not sufficiently addressed in diagnostic QA protocols. All three imaging modalities have multiple potential sources of spatial and geometric errors and understanding of these parameters is necessary for design of an effective quality assurance program. The design of QA programs for these devices will be affected by the location of individual scanner and distribution of its utilization for diagnostic and radiation therapy imaging. Scanners which have dual purpose (diagnostic and treatment planning imaging) should have a QA program designed jointly by diagnostic and radiation therapy physicists to ensure that the program meets the needs of both groups.The quality assurance for these imaging modalities in the radiation therapy goes beyond the QA of the scanners and should include evaluation of implementation of images in the treatment planning process. This should include evaluation of data transfer, image registration, potential degradation in image quality, image distortions, and evaluation of process for delineation of tumor and normal structure volumes. MR and PET images can contain biologically active regions which may not correlate with any readily visible anatomic features. Correct identification and use of these regions in the treatment planning process should be a major concern of the QA program.This lecture will provide an outline and description of QA program for CT, PET, and MR scanners used in radiation therapy. The fundamental goals of such program will be described and information which can be used for establishment institution specific QA programs will be provided.Educational Objectives:1. Describe goals of QA programs for CT, PET, and MR scanners used for radiation therapy imaging.2. Describe QA process for individual imaging devices.3. Describe a concerns for verification of correct implementation of these imaging modalities in the treatment planning process.
TH‐A‐224C‐01: Long Term Clinical Experience Using Ultrasound Alignment
Authors: McNeeley S 
Published: July 2006

The use of ultrasound localization in radiotherapy has been in wide clinical use since the late 90's. It is the one of the first imaged guided radiotherapy (IGRT) systems to be widely used. The most common site of localization has been the prostate using a transabdominal approach. The technique makes use of treatment planning contour volumes with their associated isocenter overlaid on spatially localized ultrasound images. The ultrasound images are localized to the linac isocenter using various methods that include: a robotic arm, inferred stereotactic cameras, or various optical tracking methods. The difference in position between the overlaid contours and the observed ultrasound structures provides the three dimensional patient correction.Ultrasound localization has shown to be an efficient method of alignment but it does have limitations. Ultrasound images are often difficult to interpret. For prostate, the transabdominal approach takes advantage of the increased resolution when imaging through the bladder, typically positioned anterior and superior to the prostate. When patient's bladders are empty, degradation in prostate imaging typically occurs. Often, large patients necessitate using lower frequency ultrasound, which also degrades the image quality. Large patients may also limit the ability to perform a transabdominal ultrasound with the presence of a pannis. Additionally, the operator's capacity to capture and interoperate ultrasound images can vary, limiting the quality of the alignment.This lecture will touch on some of the techniques used to improve ultrasound alignment quality. These techniques were developed at an institution where over 100,000 ultrasound alignments have been performed since 1998. Also, the results from several clinical studies will be presented. These include abdominal pressure effects, procedural changes improving alignment quality, comparison with daily CT, and complication rates of a hypo‐fractionated prostate protocol using ultrasound alignment.Educational Objectives:1. Techniques in improving ultrasound image quality during alignment.2. Understanding the limitations in performing ultrasound alignment.3. Procedural changes that can improve alignment quality.
TH‐B‐330D‐01: Quality Assurance Procedures for Digital Radiography
Authors: Peck D 
Published: July 2006

The use of digital radiography is becoming the normal form of image capture replacing film. With film there are numerous Quality Assurance (QA) procedures that have been developed that cover the film processor, retake analysis, patient dose and overall system image quality. The QA procedures for digital systems are just now being developed. Since the digital detector technologies vary and with variations in image processing methods it may seem difficult to develop standardized QA procedures. Yet the endpoints of optimized image quality and minimized patient dose need to be obtained. Therefore the Physicist needs to use the knowledge of the detector characteristics and processing methods as tools to maintain QA on digital systems. These procedures need to be rigorous enough to provide QA, yet they must be flexible enough to work for different detectors, processing methods and system applications. This lecture will provide an overview of the testing procedures for digital radiographic systems and suggest procedures that can be used to provide QA in digital radiography.Educational Objectives1. Review detector testing procedures used to assess digital systems.2. Review QA procedures used in radiography and relate these to digital technologies.3. Suggest QA procedures that can be used to evaluate digital systems.