bluuebunny/crossref_metadata_2025_split huggingface dataset:
WE‐E‐211‐01: X‐Ray Phase Sensitive Imaging Methods
Authors: Chen G , Connor D , Liu H , Zambelli J 
Published: November 2011

The basic principles of image formation and interpretation in x‐ray imaging, including x‐ray computed tomography (CT), have remained essentially unchanged since Roentgen first discovered x‐rays in 1895. As a result, absorption contrast is the sole contrast mechanism for x‐ray biomedical imaging, unlike some other imaging modalities such as magnetic resonance imaging (MRI) where multiple contrast mechanisms are available for use in clinical practice. In recent years, tremendous progress has been made in exploring other contrast mechanisms in x‐ray imaging by studying their wave nature. These methods have been classified as x‐ray phase sensitive imaging methods. To enable practical medical applications, the research of x‐ray phase sensitive imaging methods must overcome the limitations of the requirement of highly temporally and spatially coherent x‐rays. Recently, using laboratory x‐ray tubes, several x‐ray wave imaging methods have been successfully developed, including in‐line holography, diffraction enhanced imaging (DEI), and differential phase contract computed tomography (DPC‐CT).The overall objective of this symposium is to present the AAPM community with an overview of x‐ray phase sensitive imaging methods including basic physics, basic implementation methods, pros and cons for each implementation method, and future research directions. The symposium consists of four lectures presented by invited speakers and a panel discussion with the audience at the end of the symposium.Dr. Guang‐Hong Chen will be presenting an overview of basic x‐ray wave physics and other research directions not covered by the other three invited speakers.Dr. Dean Connor will be presenting the basic principles and applications of diffraction enhanced imaging method (DEI). The most promising application is breast imaging, for which DEI has improved feature contrast relative to conventional mammography and could significantly reduce dose. Though DEI was first implemented only at synchrotron research facilities, Dr. Connor and his collaborators have developed an x‐ray tube‐based DEI system. He will discuss progress towards a clinical DEI mammography system.Dr. Hong Liu and Dr. Xizeng Wu will be presenting the basic principles, newly developed prototype systems and results of experimental investigations on x‐ray in‐line phase contrast; as well as quantitative phase retrieval imaging methods.Dr. Joseph Zambelli will be presenting basic principles and applications of differential phase contrast computed tomography imaging. Fundamentals of system design, measurements of performance on an experimental system, and comparisons this new imaging technique with conventional absorption imaging will be presented. Technical details such as of the fabrication of the specialized x‐ray phase and absorption gratings and unique system requirements imposed by the technique will also be discussed.
WE‐F‐110‐01: Radiation & Cataract: A New Challenge
Authors: Rehani M 
Published: November 2011

We are passing through an era wherein it is certain that the currently accepted threshold for radiation cataract is no longer valid. Radiation cataract has, to date, been considered a deterministic effect with threshold. The International Commission on Radiological Protection (ICRP) has published threshold values for detectable opacities of 5 Gy for chronic and 0.5–2.0 Gy for acute exposures. A number of studies in staff involved in interventional procedures, in particular cardiology and other radiation exposed populations, including astronauts, atomic bomb survivors, X‐ray technologists and clean‐up workers in Chernobyl, have indicated that there is an increased incidence of lens opacities at doses below 1 Gy. The higher workload that is typical now in many cath labs, a lack of training in radiation protection and non‐availability or non‐use of radiation protection devices can result in doses to the eye lens that are high enough to cause lens injuries. International Atomic Energy Agency (IAEA) had launched a project to test the eyes of interventional cardiologists and support staff and results have been published in two papers in 2010. Further there have been publications in 2010 on the efficacy of various shielding strategies for protection of the operatorˈs eyes in the interventional suits. Leaded glasses, scatter‐shielding drapes and leaded shields were evaluated in various combinations and in different (characteristic) operator positions. It is reported that the use of leaded glasses alone reduced the lens dose rate by a factor of five to 10, while scatter‐shielding drapes alone reduced the dose rate by a factor of five to 25. Using both eye‐shielding implements together reduced the dose rate by a factor of 25 or more, and always proved more protective than either used alone.The talk will review the basic information about radiation catactogenesis, epidemiological information and results of recent studies.Learning Objectives:1. To understand the basic information about radiation cataractogenesis2. To understand the efficacy of protective tools3. To become aware about the likely changes in current recommendation that may be brought up by international bodies such as the ICRP.
WE‐G‐BRC‐06: Magnetic Resonance Imaging : Enhancing Concepts through Desktop Models and Supplementing Clinical Rotations with Video Presentations
Authors: Sinha U , Sinha S 
Published: November 2011

Purpose: Magnetic Resonance Imaging is a challenging area of Medical Physics. Concepts presented in didactic lectures can be reinforced if hands‐on laboratory procedures can be simultaneously performed by students. This can be accomplished on a clinical scanner if access is unlimited. However, the constraints of scanner availability usually preclude students from experimenting with different procedures. Further, it is not feasible to allow students to experiment extensively with clinical systems since scanner performance cannot be compromised. Methods: To address the need for hands‐on training as well as the limited availability of MR scanners, we have integrated a desktop Earthˈs field MRI system to reinforce concepts in NMR and MRI and a video presentation of a comprehensive MR Quality Control procedure performed by a MR physicist. The desktop Earthˈs Field MRI system (TerraNova) allows students to learn NMR and MRI fundamentals. The video records a MR QC procedure and takes students through the different steps to perform the comprehensive QC exam for ABR. In addition, the video highlights procedural errors and simulates conditions that result in commonly encountered artifacts. The video and MR images are provided to students so that they can independently analyze the images. The sequence of presentation was as follows: didactic lecture (prior semester), desktop experiments, video of MRQC culminating with the actual clinical rotation. Results: A one hour lecture and 4 hour lab was developed with the desktop model and students successfully completed the lab in groups of two. Video and image analysis were completed individually by each student prior to the clinical lab rotation. Surveys conducted at each step confirmed the additional learning value of the desktop model and the video. Conclusions: In addition to enhancing the learning of MRI, the novel approach also resulted in an improved efficiency of the MR clinical rotation.Funding Support: P1 16V090024, Department of Education, FIPSE.
WE‐G‐214‐07: Proton Beam Range Verification with PET: Comparison of O‐18, O‐16 and C‐12 Activation
Authors: Cho J , Mawlawi O , Gillin M , Titt U , Gonzalez‐Lepera C , Ibbott G 
Published: November 2011

Purpose: Accurate estimation of the Bragg‐peak‐distal‐edge (BPDE) location is crucial in proton therapy dose delivery. Current range verification techniques includes PET imaging which takes advantage of the Beta+ emitters produced following proton interaction within the patient body. However, such interactions produce negligible PET signal at the BPDE due largely to the decrease in proton energy with depth, which reduces the efficiency of Beta+ emitter production. The objective of this study is to investigate the feasibility of overcoming this limitation by infusing 18O into the treatment volume through 18O(p,n)18F interaction while leveraging the longer 18F t1/2 and its lower interaction energy threshold. This study compares PET signals from irradiated 18O water with 16O water and heptane over different depths of BPDE to estimate the improvement 18O water brings about in BPDE estimation. Methods: Petri dishes containing 2 mm depth of 18O water, 16O water, or Heptane (C7H16) were stacked on a water‐equivalent plastic phantom of thickness chosen to position the samples in the distal 99% to 8% dose region of a proton beam. A dose of 10 Gy was delivered to the 100% dose point. The petri dishes were then positioned in FOV of a PET/CT scanner 20 min post irradiation and scanned for 15 min. Mean activities of all samples were obtained over different BPDE region and normalized to maximum of 18O water. MC activity simulation for the three sample materials was performed for comparison. Results: Mean activities for each sample are as follow for BPDE 99%∼87%, 87%∼65%, 65%∼20%, and 39%∼8% regions. 18O water — 100%, 19%, 5%, 2%; 16O water — 29%, 4%, and negligible; heptanes — 12% and negligible. MC simulation showed consistent results with measurements. Conclusions: Strong to reasonable activities from 18O water over all BPDE regions indicates the possibility of using 18O for reliable range verification.Funding provided by the University of Texas MD Anderson Cancer Center.
WE‐G‐220‐02: Ultrasound Symposium: Computational Modeling of High‐Intensity Focused Ultrasound Mediated Drug Delivery
Authors: Haemmerich D , Dreher M , Gasselhuber A 
Published: November 2011

Purpose: Low‐Temperature Sensitive Liposomes (LTSL) are drug delivery vehicles with that release the drug upon heating above ∼40 °C. The combination of LTSL with local heat generated by focused ultrasound may thus allow non‐invasively targeted drug delivery. The complex interplay between heat based cancer treatments like thermal ablation and chemotherapy requires computational models to identify the relationship between heat exposure and pharmacokinetics in order to optimize drug delivery. Methods: We developed mathematical models combining a model of tissue heating with a drug delivery model. Deposited HIFU energy (i.e. SAR) was calculated from phantom experiments, and used as input data for the model. Microvascular perfusion was modeled according to Pennesˈ Bioheat Equation, and was varied with temperature. A spatio‐temporal multi‐compartment pharmacokinetic model was created to describe the release of doxorubicin (DOX) from LTSL into the tumor plasma, subsequent transport into the interstitium, and finally uptake by the cells. Tissue was heated for varying times to target temperatures between 42 °C and 60 °C at the ultrasound focal spot, and spatio‐temporal drug concentration profiles were calculated. Results: At target temperatures in the hyperthermic range, maximum drug concentrations of ∼ 9 ug/g were observed in the central heating area, with very localized drug deposition. At ablative temperatures similar maximum drug concentrations were observed, with a ring‐like spatial concentration profile due to progressive shut‐down of perfusion at temperatures above 45 °C. Concentration increased approximately linearly with time during the examined time periods.Conclusion: HIFU mediated targeted drug delivery via LTSL locally keeps plasma concentration of bioavailable drug high during hyperthermic temperature exposure, allowing for localized cellular uptake at heated locations. Heating induced temperature changes in perfusion considerably affect drug delivery, particularly if cessation of perfusion is induced. Multi‐ physics mathematical models may allow for optimization of heat‐mediated targeted drug delivery from LTSL, as well as for treatment planning.Educational objectives:1. Learn basic components of a drug delivery model2. Learn how computational models allow optimization of drug delivery3. Learn importance of treatment planning in targeted drug delivery
TH‐A‐224‐03: Atlas Based Auto‐Segmentation Based on Deformable Image Registration
Authors: Dong L , Yang J , Zhang Y , Zhang L 
Published: November 2011

Inverse planning based on intensity‐modulated radiation therapy (IMRT) requires the delineation of target volumes and normal critical organs. Anatomy segmentation becomes an important step in modern radiation therapy. Unfortunately, anatomy segmentation is traditionally done by a manual contouring process, which can be labor‐intensive and subject to inter‐observer variations. When many anatomical structures are to be contoured in 3D or 4D CT datasets, the manual contouring process can be a bottleneck for IMRT planning, especially in adaptive radiotherapy which involves multiple, sequential re‐planning. Recently, deformable image registration demonstrates its advantage for auto‐segmentation. The basic assumption is that patientˈs anatomy can be deformably mapped from a previously defined anatomy configuration — the atlas. This reference anatomy can be the same patient (in adaptive radiotherapy) or a different patient within the same class (or a patient with the same type of cancer). Deformable image registration provided a voxel‐by‐voxel transformation field, which can be used to map contours (or the labeled volumes) from the reference patient to the new image. Atlas‐based auto‐segmentation has a special advantage in image‐guided adaptive radiotherapy, because the original atlas contains both target volume and normal structures, and is already defined in the original treatment plan, making treatment adaptation a much simple process. In this presentation, we will discuss our clinical experience for using atlas‐based segmentation for intra‐object (the same patient) contour propagation and inter‐object (a different patient) auto‐ segmentation. Validation of auto‐segmentation is also an important step to be discussed.Educational Objectives:1. Describe deformable image registration for auto‐segmentation2. Understand the achievable accuracy and validation methods for anatomy‐segmentation.3. Illustrate applications of atlas‐based auto‐segmentation in radiation therapy
TH‐A‐220‐02: Improving Localization of Lung Cancer Targets for Radiotherapy Using Semi‐Deformable Featurelet Registration
Authors: Robertson S , Weiss E , Badawi AM , Hugo GD 
Published: November 2011

Purpose: To assess errors in online localization of deforming and regressing target structures, and to evaluate potential error reduction using rigid registration of individual featurelets distributed on the target surface. Methods: Fifteen patients with locally advanced non‐small‐cell lung cancer received weekly CT scans throughout treatment under active breathing control. The primary gross tumor volume (GTV) was contoured on each image by a physician, including two GTVs for one patient. To eliminate patient setup errors during image acquisition, secondary images were manually registered to the reference image using bony anatomy. Initial errors were computed as the distance between centroids of the GTV from reference and secondary images in this alignment. Six separate rigid registrations were then performed to align featurelets contained by the left, right, anterior, posterior, superior, and inferior subvolumes of the GTV, including a 1 cm margin. A final translation was computed by averaging the two registrations along each patient axis. Residual errors were defined as the remaining distance between centroids of the GTV from reference and secondary images in this final orientation. Improvements were gauged relative to bony alignment and to standard whole‐target registration. Results: The mean (standard deviation) of the absolute value of initial errors was 3.0 (2.7) mm, 3.8 (3.7) mm, and 3.6 (3.4) mm in the lateral, anterior‐posterior, and superior‐inferior directions, respectively. Whole‐target registration reduced corresponding errors to as low as 1.6 (1.5) mm, 1.8 (2.0) mm, and 2.4 (2.3) mm. Featurelet registration provided the lowest absolute mean residual errors of 1.5 (1.3) mm, 1.4 (1.2) mm, and 1.9 (1.6) mm. Conclusions: Featurelet registration demonstrated improved tumor centroid reproducibility compared to bony‐anatomy and whole‐target alignments. Future work includes automation and optimization of featurelet detection and subvolume definition.Supported in part by NIH R01CA116249
TH‐A‐220‐03: On the Dosimetric Effect and Correction of Inverse Consistency and Transitivity Errors in Dose Accumulation
Authors: Hardcastle N , Bender E , Tome W 
Published: November 2011

Purpose: To investigate the dosimetric effect of deformable image registration (DIR) inverse consistency and transitivity errors in dose accumulation and to propose a correction strategy to reduce the impact of these errors. Methods: Given three images, A, B and C, deformation maps are defined as third‐order transitive if the deformation A‐>B‐>C‐>A results in the image A. Four tomotherapy MVCT images from a head and neck treatment were selected representing the anatomical change over the duration of the treatment course. A research version of the Pinnacle RTPS (v9.1) was used for all planning, DIR and dose warping. A seven‐field IMRT plan was created delivering 69.3Gy, 60 & 56Gy to the high, intermediate and low‐dose PTVs respectively. This plan was copied to each of the other three images and the dose calculated on all images. All images were deformed to each other using the fast symmetric Demons algorithm. This algorithm is not inverse‐consistent or transitive error‐free. The dose from each image was warped to and accumulated on the fourth image to result in ‘D_AC1’. The dose from each image was then warped to and accumulated on the third image to result in ‘C_AC1’. ‘C_AC1’ was then warped to the fourth image to result in ‘DAC2’. The difference in between ‘D ACT’ and ‘D_AC2’ was measured. This dose accumulation process was then repeated after all deformation maps were made inverse consistent and then transitive. Results: Inverse consistency and transitivity errors lead to an observable difference between ‘D_AC1’ and ‘D_AC2’. The difference decreased with inverse‐consistent DVFs and decreased further with transitive DVFs. Conclusion: Inverse consistency and transitivity errors lead to discrepancies between doses warped to the same image via different pathways. These discrepancies can be significantly reduced by enforcing inverse consistency and transitivity between all DVFs used in dose accumulation.N Hardcastle is funded by Philips Healthcare
TH‐C‐BRC‐03: Comparison of 4D Dose Distribution Delivered with Two Different Tumor Tracking Strategies for Patients with Irregular Breathing: DRRT vs CDRT
Authors: Yang X , Han‐Oh S , Gui M , Niu Y , Yu C , Yi B 
Published: November 2011

Purpose: Dose‐rate‐regulated tracking (DRRT) is a tumor tracking strategy that programs the MLC to track the tumor and adapts to breathing irregularities during delivery using dose rate regulation. Constant‐dose‐rate tracking (CDRT) adjusts the MLC motion based on real‐time detection of tumor displacement. The purpose of this study is to illustrate the differences in the effectiveness and delivery accuracy between these two tracking methods when dealing with breathing irregularities. Methods: Step‐and‐ shoot IMRT plans optimized at a reference phase were extended to the remaining phases to generate 10‐phased 4D‐IMRT plans using segment aperture morphing (SAM) algorithm, where both tumor displacement and deformation were considered. A SAM‐based 4D plan has been demonstrated to provide better plan quality than plans not considering target deformation. However, delivering such a plan requires pre‐programming of the MLC aperture sequence. Delivery of the 4D plans using DRRT and CDRT tracking approaches was simulated assuming the breathing period is either shorter or longer than the planning day. In DRRT, dose rate was regulated to speed‐up or slow down delivery as needed such that each planned segment is delivered at the planned breathing phase. In CDRT strategy, MLC is separately controlled to follow the tumor motion, but dose rate was kept constant. Results: Delivery of preprogrammed 4D plans by the CDRT method resulted in an average of 5% increase in target dose and noticeable increase in OAR dose when patient breathing is either 10% faster or slower than the planning day. In contrast, DRRT method showed less than 1% reduction in target dose and no noticeable change in OAR dose under the same breathing irregularities. Conclusions: In delivery of SAM‐ based 4D‐IMRT treatment plans considering tumor deformation as well as motion irregularities, the DRRT tracking method was found to be much more effective and more accurate than the CDRT strategy.This research was supported in part by NIH grant 1R01CA133539‐01A2.
TH‐C‐214‐03: The Good the Bad and the Ugly about Using PET for Treatment Planning?”
Authors: Visvikis D 
Published: November 2011

The use of PET data into the treatment planning process has been the focus of intense development over the past few years. The availability of multi‐ modality devices such as PET/CT has clearly intensified the interest on the use of PET information for treatment planning and associated research and development. The potential of such functional data includes the identification of tumour specific physiological processes and associated 3D functional volumes which in turn hold the potential of personalized treatment planning. However, there are numerous issues associated with the use of PET derived information in treatment planning, starting from the image acquisition protocols, the tracer or combination of tracers to be used, the fusion of PET and planning CT images, the accurate extraction of 3D functional volumes from the reconstructed PET images, and finally the different scenarios for the incorporation of the functional information in dose planning and delivery. This paper will review, primarily from a technological point of view, the current status of the integration of PET/CT data into the treatment process, discussing current successes and failures, as well as reflecting on the future. The use of PET data must be based upon a clear understanding of the interpretation and limitations of the functional signal. Subsequently consideration will be given to the requirements of PET/CT data acquisition and subsequent image processing accounting for technological limitations associated with current state of the art PET/CT devices. Approaches for the definition of functional/tumour volumes and the mechanisms available to measure and include physiological motion into the imaging process will be also reviewed. Finally the impact of these technological issues on current protocols for the implementation of functional data in the treatment planning process will be presented.Learning objectives:1. Understand the main incentives behind the use of PET in treatment planning.2. Understand the issues associated with the use of PET information in treatment planning.3. Understand the current status and potential future developments for the optimal integration of PET functional data in treatment planning