bluuebunny/crossref_metadata_2025_split huggingface dataset:
MO‐D‐330A‐07: A Stationary Scanning X‐Ay Imaging System Based On Carbon Nanotube Field Emitters
Authors: Zhang J , Yang G , Rajaram R , Quan E , Lee Y , Lalush D , Lu J , Chang S , Zhou O 
Published: July 2006

Purpose: Most tomographic imaging systems available today use a single x‐ray source and multiple projection images are obtained by rotating the x‐ray source around the object. Therefore the data acquisition rate is limited by the gantry rotation speed, which is approaching the physical limit. We proposed to develop a novel stationary scanning x‐ray imaging system based on carbon nanotube field emission x‐ray (FEX) technology. Instead of a single x‐ray source the proposed system is based on a multi‐pixel FEX source. The new scanner promises a dramatically faster data acquisition rate by reducing or totally eliminating the mechanical motion. Method and Materials: We have constructed a prototype stationary scanning x‐ray imaging system with an array of 9 individually addressable x‐ray source pixels, each of which can produce a different projection image of the object. The core of this novel x‐ray imaging technology is a gated carbon nanotube field emission cathode array. By programming the gate voltage of the cathode array, the multi‐pixel x‐ray source can generate an electronically triggered scanning x‐ray beam and produce multiple projection images from different viewing angles without mechanical motion. A Hamamatsu C7921 flat panel x‐ray sensor was used to collect all 9 projection images. Results: Tomosynthesis images of a mouse and a standard breast‐imaging phantom (Stereotactic Needle‐biopsy Tissue Equivalent Phantom, Nuclear Associates, NY) using the prototype stationary scanning x‐ray imaging system are acquired. Tomosynthesis reconstructions were applied to the breast phantom. The slice images reconstructed using an iterative reconstruction algorithm clearly show the internal structures of the breast‐imaging phantom at different depths. Conclusion: We have developed a stationary scanning x‐ray imaging system using a carbon nanotube based multi‐pixel FEX source. The mechanical motion free approach can lead to a faster and simplified tomographic imaging system.Conflict of Interest: Research partially supported by Xintek Inc.
MO‐D‐ValB‐07: Comparison of Inline and Orthogonal Imaging and Treatment Beam Geometries for Monitoring the Motion of Implanted Markers
Authors: Suh Y , Dieterich S , Keall P 
Published: July 2006

Purpose: The purpose of this study is to investigate the accuracy of different 2D methods monitoring implanted markers, compared to 3D method for real‐time tumor tracking radiotherapy. The different imaging‐treatment beam geometries were the imaging beam parallel to treatment beam (inline) and orthogonal to treatment beam.Method and Materials: The 3D motion datasets of ten patients from Cyberknife treatments were used. For given beam angles, the positions of implanted markers were calculated and its geometric uncertainty was quantified for two 2D monitoring methods. Since neither can monitor the motion of markers in the imaging beam axis, the geometric errors were determined in that direction with respect to the treatment beam. Assuming that 3D pre‐treatment online positioning was performed and thus errors are predominantly random, treatment margins due to the limitations of 2D methods were quantified. For the orthogonal monitoring, margin, M=1.65σ, was used with the assumption of zero systematic errors; while for the inline, the required margin can be calculated by integrating the probability density function of the geometric uncertainty with the dose falloff along the beam direction. Results: In terms of couch motion, the positioning uncertainty is lowest for coplanar treatments, consistent with predominantly superior‐inferior motion. Regarding gantry angles, it is lowest for lateral beams, consistent with the smallest left‐right motion. The average positioning uncertainty along the imaging beam axis is 0.05–0.16cm (1 SD) with maximum values for individual patients ranging 0.09–0.33cm, which result in 0.08–0.26cm margins for orthogonal monitoring.Conclusion: The impact of the geometric relationship between the imaging and treatment beam has been studied by quantifying the error from out of plane motion for inline and orthogonal imaging‐treatment geometries. The errors for inline geometry result in negligible additional margin required. In the absence of other errors, the orthogonal monitoring contributes up to 0.26cm to the total margin.
MO‐D‐ValB‐08: Fluoroscopic Tracking of Lung Tumor Mass Without Implanted Fiducial Markers
Authors: Cui Y , Dy J , Sharp G , Alexander B , Jiang S 
Published: July 2006

Purpose: To develop techniques for direct lung tumor tracking in fluoroscopic images without implanted markers. Method and Materials: During the patient setup session, a pair of 15 second orthogonal fluoroscopic images are taken and processed off‐line to generate reference templates. Each breathing cycle is divided into 12 phase bins. Setup image frames falling in a specific bin are motion‐enhanced and averaged, and an ROI that contains the tumor is selected to be the reference template for that phase bin. Each reference template corresponds to a tumor position in the image. During the treatment, as soon as a fluoroscopic image is acquired, the cross‐correlation score between each reference template and this image is maximized by allowing small shifts of the template in both X and Y directions. Then the tumor position is derived by averaging the tumor centroid coordinates in those templates of high scores (above 85% of the maximum score). For comparison, tumor position in each image frame was also marked by a clinician. Results: We tested our algorithm on six sequences of fluoroscopic images from six lung cancer patients. The automatically detected tumor centroid coordinates agree well with the manually marked results, with an average error of 1 mm. Conclusion: This study demonstrates the feasibility of tracking lung tumor mass in fluoroscopic images without implanted fiducial markers. Future research will concentrate on further improvement of the accuracy and robustness, and reducing the computational cost.The project is partially supported by NCI grant (1 R21 CA110177 A 01A1) and NSF Grant No. IIS‐0347532.
MO‐D‐ValA‐03: Inverse Planning Optimization with Organ Motion Probability
Authors: Bortfeld T , Trofimov A , Chan T , Martin B , Paganetti H , Jiang S 
Published: July 2006

Organ motion blurs dose distributions. The blurring can be described in a statistical way by use of a motion probability (density) function (PDF). The motion‐blurred dose distribution is obtained by a convolution of the “sharp” (static case) dose distribution with the motion PDF. This holds true for both inter‐ and intra‐fraction motions. In the case of intra‐fraction motions an “interplay” effect is superimposed on top of the blurring effect. It has been shown that the interplay effect averages out during the course of a fractionated treatment, and that it is usually negligible after a typical number of fractions. The convolution model relies on the linear superimposition principle, which holds true for dose values but not for the biological effect. This issue has recently been addressed and will be discussed.Several investigations have now looked at the feasibility of un‐doing the motion blur through the use if intensity‐modulation. In principle it should indeed be possible to de‐convolve the motion PDF from the intensity maps, in order to compensate motion effects. This approach has been called 4D optimization or 4D inverse planning. Motion de‐convolution cannot, however, compensate motion effects exactly and it cannot be applied in a naïve straight‐forward way, because that would lead to undeliverable intensity maps with sharp spikes and negative values. The method of choice is rather to include the motion PDF in the IMRT optimization process. It has been shown that this can indeed yield a surprisingly high degree of motion compensation and it can even compete with other motion compensation methods such as gated delivery. However, this is only true if the motion characteristics (the PDF) are known with great precision. If the actually realized motion PDF deviates substantially from the planned PDF, the method becomes less useful and can, in principle, make things worse. More recently, uncertainties in the knowledge of the motion characteristics have been taken into account by use of robust optimization techniques. With these one can now compensate for motion effects in an approximate way for a large class of motion characteristics. In terms of the sparing of normal structures, the results are in between the use of conventional margins and the idealistic case of perfect motion compensation. The resulting intensity maps exhibit “horns”, which can shave off a few mm from the margins.Educational Objectives:1. Understand the concepts of motion blur and PDF.2. Understand the idea of de‐blurring a dose distribution through “4D” motion optimization.3. Be able to discuss the relative potential and limitations of 4D motion optimization in comparison with margins and gating.
MO‐D‐230A‐07: Analysis of Couch Sag and Couch Deflection in Several EXACT Couches
Authors: Movahed A , Sen A , Podgorsak M , Paliwal B 
Published: July 2006

Purpose: To measure couch sag and couch deflection in several EXACT Couches. Method and Materials: Couch sag was evaluated for EXACT Couches at three positions: tip, center and base with the couch fully extended in treatment position. In each case, measurements were made with no weight and with 84, 142, and 319 lbs uniformly distributed over the couch surface. Couch deflection was evaluated with SSD readings to the couch surface using the mechanical backpointer at isocenter and digital read out. Measurement were repeated with the couch at nominal SSDs of 100 cm, 110 cm and 120 cm and with rails closed together in the middle. Same measurements were performed with Picker CT couch for comparison. Results: We found 9 mm deflection from the tip to the base of couch (fully extended) with no weight on the surface. According to Varian service personnel, design of EXACT Couches follows IEC specification and Exact Couch manufacturers provided a +5mm deflection to counter weight the patient's weight. Our couch was shimmed and brought the sag down to +5mm. EXACT Couch deflection with no weight on surface varied between 5ndash;9mm at five different centers. Sag was same at nominal SSDs. Up to 7mm sag variation was noticed depending upon the weight.With rails closed together in the middle, about 1mm decrease was noted for the above values. Upto 4mm sag was noticed in CT couch. Unlike Exact couch, CT couch sag decreased at the base. Conclusions: Study demonstrated that the +5mm deflection does not completely counter weight the patient's weight for having leveled surface at the isocenter.2–5mm sag at tip and up to −7mm at base relative to the amount of weight on couch was noticed. In time +5mm‐shimmed deflection was deteriorated to +7mm. Same results were obtained when couch was loaded.
MO‐D‐230C‐01: Evaluation of Medical Displays
Authors: Samei E 
Published: July 2006

Participants:J Charette, Barcoview, LLC;E Samei, Duke University;N Hashimoto, Eizo Nanao;K Compton, National Display Systems;A Abileah, Planar Systems;D Sorensen, Richardson Electronics / Image Systems;C Lipfert, Scanditronix Wellhofer GmbH;M Hasegawa, Totoku;H Roehrig, University of ArizonaElectronic display is a key component of modern medicine, providing soft‐copy viewing of medical images. Being the last component of the image chain, display quality can have a notable impact on overall accuracy and efficiency of the diagnostic process. Thus, it is necessary to ensure that the physical performance of a medical display is adequate for its intended use. Led by a task group initiative by the American Association of Physicists in Medicine (AAPM TG18), new guidelines have recently been published defining objective and standardized assessment procedures and criteria for acceptance testing and quality control of medical display devices (Samei et al, Med Phys 32:1205–25, 2005). The guidelines include detailed visual and quantitative methods and specific acceptance criteria for basic display characteristics including luminance, luminance spatial and angular response, resolution, noise, veiling glare, reflection, color uniformity, geometrical distortions, and display artifacts. The TG18 guidelines are also being gradually reflected in a number of other national and international directives including those by the IEC and the ACR. The goal of this demonstration workshop is multi‐fold: 1) to present a tutorial on the TG18 guidelines and its adaptations, 2) to discuss its implementation by specific vendors, 3) to offer an opportunity for hands‐on exposure to the practical aspects of display performance evaluation, 4) to provide an opportunity to informally interact with experts and ask questions, and 5) to offer a panel discussion on the issues about which there might be less consensus among experts. Representatives from the TG18 committee and from industry will be present to demonstrate and discuss display evaluation issues.Part I1:30–2:20 IntroductionEvaluation of Medical Displays, E Samei, Duke University2:20–3:20 Vendor lectures2:20–2:30 Compensation for ambient conditions, K Compton, National Display Systems2:30–2:40 AAPM implementation using Barco software, J Charette, Barcoview, LLC2:40–2:50 Quality Control Solutions based on AAPM TG18 from Eizo Nanao, N Hashimoto, Eizo Nanao Corp2:50–3:00 The CFS (Calibration Feedback System) Toolkit, D Sorensen, Richardson Electronics3:00–3:10 Totoku's Medical Display QA Solutions “i‐model”, M Hasegawa, Totoku Electric Co., Ltd.3:10–3:20 The Priorities in the Medical Displays Parameters, A Abileah, Planar Systems
MO‐E‐330D‐01: Overview of Recent Technology Developments in CT
Authors: Hsieh J 
Published: July 2006

Cone Beam CT (CBCT) is one of the most recent technical advancements in x‐ray computed tomography. The state‐of‐the‐art 64‐slice scanners provide isotropic sub‐millimeter spatial resolution, significantly improved dose efficiency, large volumetric coverage, and markedly improved temporal resolution. These capabilities open doors to new clinical applications.This presentation provides an overview of the recent technical advancements in CBCT. The discussion first covers technical challenges that face CBCT, such as detector complexity, electrical and mechanical design, image reconstruction algorithms, dose, and information management.The second part discusses some of the recent developments in CBCT. These include the advanced dose‐reduction techniques, the dual‐source CT scanner, more advanced reconstruction algorithms that break the traditional noise vs. dose tradeoffs, larger volume coverage, and dual‐energy CT for material decomposition and presentation. If the past 10 years of CT development can be characterized by the “slice‐war”, new technology developments are pointing to different directions.Learning Objective:1. Overview of the recent technology developments in CBCT.2. Understand major technical challenges in CBCT development.3. Explore future directions in CBCT technology.
MO‐E‐ValB‐01: Visualization of Anatomical Structures for Image Guided Surgery
Authors: Grimson E 
Published: July 2006

Algorithmic methods from computer vision and machine learning are dramatically changing the practice of health care and the exploration of fundamental issues in neuroscience. By coupling knowledge of tissue response, atlases of normal anatomy, and statistical models of shape variation, these methods are used to build detailed, patient‐specific reconstructions of neuroanatomical structure from MRI imagery. Such structural models can be automatically augmented with information about function (using fMRI), and about connectivity (using DT‐MRI) to create detailed models of a patient's brain. These models are routinely used for surgical planning — how to reach the target tumor with minimal damage to nearby critical structures; and for surgical navigation — guiding the surgeon to the target site rapidly and safely.By combining with statistical models of population variation, these methods can also be used to investigate basic neuroscience questions — how different are the shapes of subcortical structures between normal subjects and patients with a specific disease (such as schizophrenia or Alzheimer's); how do these shapes change with development in children, or with administration of pharmaceuticals; how do physiological properties differ between populations (such as the local structure of fiber orientation in white matter tracts). These computational methods provide a toolkit for exploring the structure and connectivity of neuroanatomical structures, in normal subjects and in diseased patients.This lecture will review current methods for image segmentation and shape analysis.Educational Objectives:1. Understand algorithmic methods for image segmentation by tissue type;2. Understand methods for analyzing shapes of anatomical structures across populations;3. Understand the application of reconstructed anatomy for surgical guidance and navigation.
MO‐E‐ValB‐02: Hybrid Imaging for Guidance of Interventional Procedures
Authors: Fahrig R 
Published: July 2006

The last decade has seen an explosion in the number of procedures carried out using minimally invasive approaches, as devices and techniques develop. The promise of these new procedures is realized only with a parallel improvement in imaging techniques. Hybrid systems that combine real‐time acquisition with cross‐sectional and/or functional data are one response to the need, and several such systems have now reached the clinic. Depending on the application, different combinations can be used to greater advantage. The interventionalist's familiarity with x‐ray fluoroscopy and the real‐time and projection capability makes it a logical first choice to marry with others such as ultrasound, CT or MR.The combination of fluoroscopy with C‐arm CT for application to 3D vascular imaging was first implemented in the mid‐90's. New flat‐panel detector technology is now expanding the role of C‐arm CT into low‐contrast imaging applications such as detection of fresh bleeds during treatment of intracranial abnormalities and guidance of vascular and percutaneous abdominal interventions. Highest image quality depends on correction algorithms for lag, truncation, scatter etc. all of which are still under investigation. Recent investigations indicate that contrast resolution as low as 5 HU is possible under clinically realistic conditions.The combination of fluoroscopy with MR has also been under investigation since the mid‐90's with several prototype long‐travel systems installed in research clinics. While feasibility of such systems has been shown, patient transport between imaging FOVs has been complicated and enthusiasm for the systems has been limited. New flat‐panel detectors which are immune to static magnetic fields, and new x‐ray tube designs are now under development that allow close integration of fluoroscopy and MR systems. Using a double‐donut interventional magnet and a static‐anode x‐ray tube, good image quality can be achieved from both modalities if care is taken to maintain magnetic field homogeneity, rf noise is limited, and the electron optics of the x‐ray tube are controlled. Switching between modalities can take a little as one minute.The current status of X‐ray/MR, and of X‐ray/CT and C‐arm fluoroscopy/C‐arm CT will be discussed and described. New hardware and software for X‐ray/MR and new image correction and visualization algorithms for fluoroscopy/C‐arm CT will be described. Current challenges in the area will be outlined.Educational Objectives:1. Understand the options available for hybrid interventional guidance.2. Understand the issues related to image quality in C‐arm‐based CT and XMR.3. Understand the current challenges relating to clinical workflow, multi‐modality registration and image visualization.Disclosure:The work presented here has been supported by NIH R01 EB003524, P41 RR 09784, R01 EB000198, Siemens Medical Solutions, GE Medical Systems and the Lucas Foundation.
MO‐E‐224C‐05: Comparison of TomoTherapy with Conventional Electron/X‐Ray Treatment Plans for Chest Wall
Authors: Ashenafi M , Boyd R , Lo K , Lee T , Hogstrom K 
Published: July 2006

Purpose: Post‐mastectomy radiotherapy (PMRT) of the chest wall (CW) often will involve use of electron beams due to their rapid fall‐off of dose near the practical range of the electron energy. The TomoTherapy helical, fan‐beam delivery system, along with the inverse‐planning optimizer, has the potential to provide planning and delivery of 6 MV x‐rays to superficial target volumes conventionally treated with electrons. In the present study, five chest wall patients were planned for TomoTherapy and compared to their conventional plan that utilized electron beams. Analysis of breathing motion were not included. Methods and Materials: Five PMRT patients treated with electron beams and planned on the Pinnacle treatment planning system (TPS) were selected. A planning target volume (PTV) was generated to follow the isodose contour defined by 90% of the prescribed dose on the Pinnacle plan. Target dose homogeneity in the Tomotherapy TPS dose optimizer was relaxed to better achieve critical structure dose objectives when necessary. Normal tissue complication probabilities (NTCP) were calculated for the lung and the heart. A questionnaire form was provided for the radiation oncologist to evaluate each plan. Results: For all cases, the TomoTherapy plan was rated superior to the Pinnacle plan by the radiation oncologists. The TomoTherapy TPS produced a significantly more uniform dose distribution in the PTV. The average volume of ipsilateral lung receiving dose above 20 Gy was reduced from 21.5% to 17.7%. The average volume of heart receiving dose above 30 Gy was reduced from 2.2% to 1.3%. NTCP for the lung and heart were also reduced in the TomoTherapy plan. Conclusion: The results of this study demonstrated that TomoTherapy is able to deliver clinically‐acceptable dose distributions to a “static” model of PMRT patients conventionally treated with electron beams.Supported in part by a research agreement with TomoTherapy, Inc.