bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evolutionary and ecological feedbacks of the survival cost of reproduction
Authors: Kuparinen Anna , Hardie David C. , Hutchings Jeffrey A. 
Published: November 2011

AbstractArguably the most fundamental of trade‐offs in life‐history evolution is the increase in natural mortality resulting from sexual maturity and reproduction. Despite its central importance, this increase in mortality, a survival cost, garners surprisingly little attention in fish and fisheries modeling studies. We undertook an exploratory analysis to evaluate the consequences of this omission for life‐history projections. To this end, we developed a simulation approach that integrates quantitative genetics into the ecological dynamics of a fish population and parameterized the model for Atlantic cod (Gadus morhua, L.). When compared to simulations in which the mortality of immature and mature individuals is equal, the inclusion of a survival cost results in larger asymptotic body size, older age at maturity, and larger size at maturity. We also find that measures of population productivity (spawning stock biomass, recruits‐per‐spawner) are overestimated if the survival cost is excluded. This sensitivity of key metrics of population growth rate and reproductive capacity to the magnitude of the survival cost of reproduction underscores the need to explicitly account for this trade‐off in projections of fish population responses to natural and anthropogenic environmental change, including fisheries.
Modeling intraspecific adaptation ofAbies sachalinensisto local altitude and responses to global warming, based on a 36‐year reciprocal transplant experiment
Authors: Ishizuka Wataru , Goto Susumu 
Published: November 2011

AbstractIntraspecific adaptation inAbies sachalinensiswas examined using models based on long‐term monitoring data gathered during a reciprocal transplant experiment with eight seed source populations and six transplantation sites along an altitudinal gradient. The consequence of local adaptation was evaluated by testing the home‐site advantage for upslope and downslope transplants at five ages. The populations’ fitness‐linked trait was set as their productivity (tree height × survival rate) at each age. The effects of global warming were evaluated on the basis of the 36‐year performance of downslope transplants. Evidence was found for adaptive genetic variation affecting both height and survival from an early age. Increasing the distance between seed source and planting site significantly reduced productivity for both upslope and downslope transplantation, demonstrating the existence of a significant home‐site advantage. The decrease in productivity was most distinct for upslope transplantations, indicating strong local adaptation to high altitudes. Global warming is predicted to increase the productivity of high‐altitude populations. However, owing to their existing local adaptation, all tested populations exhibited lower productivity under warming than demes that were optimal for the new climate. These negative predictions should be considered when planning the management of locally adapted plant species such asA. sachalinensis.
SU‐C‐224‐06: Investigation of a Modified Backscatter‐Shielded EPID Dosimetry System for Improved IMRT Verification
Authors: King B , Morf D , Greer P 
Published: November 2011

Purpose: To investigate the performance of a modified backscatter‐shielded Electronic Portal Imaging Device (BS‐EPID) system and to develop a model to convert the BS‐EPID images to water‐equivalent dose. Methods: Images were acquired with a modified Varian aS‐1000 BS‐EPID and compared to those from a comparable clinical EPID. The asymmetry of in‐plane profiles was examined as a measure of how well the system reduces the effect of the support arm backscatter. A new pixel‐sensitivity correction method was assessed by comparing BS‐EPID images of the same fields at different detector offset positions. A model was developed to determine the water equivalent dose from images acquired with the BS‐EPID. The model converts the BS‐EPID image to fluence using a deconvolution kernel, then to dose in water using a convolution kernel. The model was optimized based on experimental measurements and can be applied to construct dose in water at any depth. The validity of the model was tested using gamma analysis to compare 28 two‐dimensional dose maps of IMRT fields measured with the BS‐EPID at different depths to those predicted by the Eclipse TPS. Results: The BS‐EPID profiles gave reduced asymmetry (0.6% compared to 3.3%), showing that the backscatter shielding is effective. BS‐EPID images were consistent with different detector offsets within 0.4% on average. The IMRT dose maps measured with the BS‐EPID gave good agreement with those predicted by the TPS, with mean values of 94.6%, 91.8%, 94.0% and 95.3% of pixels meeting the gamma criteria of 2%, 2mm at depths of 1.5, 5, 10 and 20 cm respectively. Conclusions: The BS‐EPID performs effectively in reducing the effect of the backscatter from the support arm in Varian EPIDs. The BS‐EPID dosimetry system and model allows high‐resolution water equivalent doses to be measured with the BS‐EPID, streamlining IMRT quality assurance.The authors have received support, in the form of equipment loans and technical information, from Varian Medical Systems iLab GmbH.
SU‐E‐I‐97: A Protocol for Attenuation Characterization of Neurovascular Devices under Fluoroscopic Conditions
Authors: Vedantham S , Gounis M , Wakhloo A , Karellas A 
Published: November 2011

Purpose: Current approaches for ensuring adequate visualization of neuroendovascular devices that are implanted under fluoroscopic guidance, such as stents and flow diverters, are based on ad hoc methods and measures. Lack of specific standards makes it difficult to determine the adequacy of device contrast under clinical conditions. Inadequate device contrast due to low attenuation may result in increased radiation dose to the patient either due to prolonged fluoroscopy or due to the use of high dose‐ rate imaging sequence. Alternatively, this may lead to inaccurate positioning of these devices within cerebrovascular structures with potential impact on clinical outcome. We developed a protocol and applied it for evaluating such devices. Methods: The protocol comprises three parts: quantitative measurement of equivalent attenuation (in mm of Al) under conditions used for characterizing imaging system performance (RQA5 of IEC standards), visual assessment of device contrast in homogenous background (water phantom) of anatomically relevant thickness, and visual assessment of the device contrast with anatomic background. Ten devices (2 Ni‐Ti stents, 7 Co‐Cr and 1 Ni‐Ti flow diverters) were assessed using this protocol. Results: Quantitative assessment of the stents showed substantial equivalent attenuation of the device end/tip marker (Pt) bands but poor attenuation characteristics of the device body. The flow diverters demonstrated improved attenuation along the device body than the stents. The newer generation of flow diverters with Pt wires interwoven with the Co‐Cr wires demonstrated improved attenuation characteristics compared to previous generation which did not include Pt wires. Visual assessment under homogenous (16 cm water phantom) and anatomic background (skull phantom immersed in 16 cm water) provided qualitative confirmation. Conclusions: The proposed protocol with further refinements can serve as the basis for evaluating the adequacy of x‐ray contrast of neuroendovascular devices that are implanted under fluoroscopic guidance.Devices provided by Surpass Medical LTD. (Tel Aviv, Israel). Research supported in part by NIH/NCI R01CA128906 and NIH/NIBIB R21EB007767. The contents are sole responsibility of the authors and do not reflect the official views of the NIH, NCI or NIBIB.MG: Has been a consultant per hour for Micrus Endovascular and Codman Neurovascular; receives research support from Stryker Neurovascular, Micrus Endovascular, Codman Neurovascular, Neurointerventional Technologies, Neuravi, Thrombolysis Scientific Inc, and Concentric Medical.AW: Has been a consultant per hour for Codman Neurovascular, Stryker Neurovascular, Boston Medical Associates, Surpass Medical Ltd; holds ownership interest in Surpass Medical Ltd; receives research support from Philips Healthcare.
SU‐E‐I‐136: MR Imaging Techniques with Reduced Metal Artifact for Improved Brachytherapy Device Visualization
Authors: Warner L , Kotys‐Traughber M , Blume U 
Published: November 2011

Purpose: Applicators and seeds for brachytherapy composed of metal have very short T2/T2* species, that induce severe susceptibility artifacts in the surrounding tissue with conventional MR imaging turbo spin echo (TSE) methods, making accurate dose planning and treatment assessment difficult. Nevertheless, recent advances may facilitate imaging of these short T2/T2* species and simplify the current workflow. We propose to use these techniques for improved visualization of brachytherapy devices using MRI. Various imaging strategies for metal artifact reduction, such as an ultrashort echo time (UTE), slice encoding for metal artifact correction (SEMAC), view angle tilting (VAT), and multi acquisition variable resonance image combination (MAVRIC) were investigated. Methods: The tandem from an MR‐compatible FSD‐style applicator set (Varian Medical Systems, Palo Alto, CA, USA) was embedded in 20% gelatin. Scanning was performed on an Achieva 3.0T TX system using a 16 element phased array coil (Philips Healthcare, Best, NL). Images were acquired along the plane parallel to the tandem axis. Sequences parameters are summarized in Table 1. Studies were repeated for a gold seed embedded in 20% gelatin and seed dimensions quantified by the profile image full width half maximum along longitudinal and transverse seed axes. Results: The SEMAC sequence imaged the tandem tip exceptionally well, Figure 1. The gold seed was distinctly visible with all sequences, Figure 2, and the SEMAC dimensions were closest to the true dimensions. Conclusions: All investigated sequences outperform conventional TSE imaging. Overall, the SEMAC sequence is timely (6x< MAVRIC) with superior metal artifact reduction, and the UTE sequence is ideally suited for quick survey scans and may be useful for distinguishing seeds. MAVRIC has the greatest SNR, but requires long scan times. Although VAT limits in‐plane metal artifact, it is poorly suited for brachytherapy planning. Therefore, the use of a SEMAC sequence is beneficial in brachytherapy planning.I have the following conflict of interest to disclose with regard to the subject matter of this presentation: Company Name: Philips Healthcare, Type of Relationship: Employer
SU‐E‐I‐161: Quantifying the Viscoelastic Properties of Human Hepatic Malignancies Using Dynamic Compression Testing
Authors: DeWall R , Bharat S , Varghese T , Hanson M , Kliewer M 
Published: November 2011

Purpose: Manual palpation is often used to qualitatively assess the presence of diseases because of known correlations between tissue stiffness and pathological state. Ultrasound elastographic techniques provide an objective form of palpation and include strain imaging, acoustic radiation force imaging (ARFI), and transient elastography. However, tissue compression can affect tissue stiffness estimates. In this study, we dynamically compress several different hepatic malignancies through a range of compressional loads to determine the effect of strain hardening on modulus estimates and modulus contrast.Methods: Fourteen hepatic tissue samples with various pathologies were obtained from the UW Pathology lab from patients undergoing surgical resection. Among them were hepatocellular carcinomas (HCCs; n=2), colon metastases (METs; n=7), rectal METs (n=1), gastrointestinal (GIST) METs (n=1), neuroendocrine METs (n=1), and cirrhosis (n=2). Samples were dynamically tested using an Enduratec ELF 3220 (Bose Corp., Minnetonka, MN) from 1 to 6% precompression at 1, 10, 20, and 30 Hz.Results: The storage modulus, a measure of the elastic energy stored each compression cycle, was quantified for pathological and normal tissue. The average storage modulus for normal tissue tested at 1% compression and 1 Hz was 3.3 kPa. The storage moduli for pathological tissue were 3.5, 23.1, 30.9, 4.3, 3.9, and 13.7 kPa for HCCs, colon METs, rectal METs, GIST METs, neuroendcrine METs, and cirrhosis, respectively Conclusions: These results show the effects of strain hardening on normal and pathological human liver tissue. Some cancers were significantly stiffer than the surrounding background, indicating that elastographic techniques may be useful in delineating the pathology. Some cancers, such as HCCs, were approximately the same stiffness as the surrounding background. Strain hardening observed with some cancers suggests that compression may increase contrast between the cancer and the surrounding tissue.This work is supported by NIH grants R01 CA112192‐04, R01 CA112192‐ S103, and T32 CA09206‐31.
SU‐E‐J‐57: Clinical Protocol for DTS‐Based APBI Setup: Optimal Data Acquisition, Reconstruction and Registration Parameters Using Varian DTS Software
Authors: Ng SK , Lyatskaya Y , Hesser J , Jeung A , Mostafavi H , Bellon J , Wong J , Zygmanski P 
Published: November 2011

Purpose: Digital tomosynthesis (DTS) was evaluated as an alternative to CBCT for minimizing possibility of collisions and reducing imaging dose. While feasibility of DTS was demonstrated for APBI patient setup, clinical implementation has not been optimized for this technique. This work characterizes data acquisition/registration parameters and establishes clinical protocol for accurate setup using: Varian OBI system for data acquisition; and non‐clinical Varian DTS software for DTS reconstruction/registration for APBI patient setup. Methods: Backprojection‐and‐deblurring algorithms were used for DTS volume reconstructions. DTS volume registrations were done manually and automatically (cross‐correlation). Subsequent triangulation on two short DTS arcs was done to improve registration accuracy. Software performance was evaluated on a breast phantom and nine breast cancer patients, under an IRB‐approved protocol. Parameters investigated include arc lengths, arc orientations, number of arcs, reconstruction slice spacing and other limiting factors relevant to clinical practice. Shifts determined from the registration of DTS volumes were compared to the shifts based on registration between planning CT and CBCT. The difference between these shifts was used to evaluate the software performance and accuracy. The findings were quantified and optimal parameters for clinical use of DTS technique were determined. Results: At least two arcs were necessary for accurate setup evaluation. Registration accuracy of 2 mm was achieved when reconstruction arc length was > 5 deg for clips with HU>1000; larger arc length (> 8 deg) was required for low HU clips. Optimal arc separation was found to be > 20 deg. Optimal arc length was determined to be 8–10 deg. No dependence on DTS slice spacing was found. Time required for DTS reconstruction was 10s– 45 s and it was less than 20s for registration. Conclusions: Optimal data acquisition/registration parameters were determined for DTS imaging utilized for APBI patient setup, and performance of the software was objectively quantified.This study is supported by grant from Varian Medical Systems Inc. and Kayes grant
SU‐E‐J‐65: Order of Magnitude Reduction of Radiation Exposure in Fluoroscopically Guided Interventional Procedures
Authors: Rowlands JA , Robert N 
Published: November 2011

Purpose: The role of fluoroscopic imaging is important and expanding for diagnostic and image guided therapy application. However, fluoroscopic imaging requires significant amounts of radiation leading to increased risk of cancer induction as well as non‐stochastic effects such as radiation burns. Our purpose is to reduce the exposure and dose to the patient by an order of magnitude by the simultaneous application of previously established methods in a manner which alleviates the shortcomings of each. Method and Materials:Pulsed fluoroscopy can reduce dose and exposure rate by replacing a 30 frame per second sequence by a 15 or 7.5 frames per second rate, but the unnatural jumpy nature of the reduced update rate disturbs the natural eye/brain comprehension of the image sequence. Region of interest fluoroscopy is where the central region of the image has full exposure and the peripheral image, there to provide context only, has been reduced in dose. It has been shown in several studies to reduce exposure rate and dose to the patient by an interesting but not compelling amount of ∼2 times. The scientific reason for this unimpressive result is the very poor DQE(0) of flat panel imagers at low exposure rates. Results: A newly designed collimator which permits the exposure of only the region of interest to be inserted or removed between images at the 30 frame/second rate used in real time imaging has permitted a new approach to ROI imaging where the peripheral image can be obtained at very low frame rates and hence low total exposure while the central region can be obtained at full frame rate and normal exposure rates. Conclusions: A practical technical solution to reduction of exposure and dose during fluoroscopic procedures has been identified and tested.IKON Inc. have agreed to provide prototype ROI collimators for use in this work at no cost to the authors.
SU‐E‐J‐82: MRI‐Guided Lung Tumor Tracking
Authors: Cerviño L , Du J , Jiang S 
Published: November 2011

Purpose: To track lung tumor in cine MR images. Methods: 5 healthy volunteers underwent sessions of a single sagittal‐slice cine‐MRI with image acquisition frequency of 4Hz. A slice with a visible vascular structure (target) was imaged, and the field of view was adjusted so that the diaphragm was visible in all the slices. Volunteers were asked to breathe under 4 different breathing patterns, each one of 5‐minute duration: free breathing; normal inspiration followed by elongated expiration; irregular breathing; and inhale through the nose and impeded exhale through the mouth. Targetˈs location was manually identified in all the frames. Two tracking algorithms were implemented and evaluated: a template matching (TM) algorithm in combination with surrogate tracking using the diaphragm (surrogate was used when the maximum correlation between the template and the image in the search window was less than specified); and an artificial neural network (ANN) model based on the principal components of a region of interest that encompasses the target motion. Mean tracking error e and error at 95% confidence level e95 were evaluated for each model. Results: The ANN model led to e=1.5mm and e95=4.2mm, while TM led to e=0.6mm and e95=1.1mm. A series with out‐of‐plane motion was considered separately to evaluate the benefit of using surrogate tracking in combination with TM. For this series, the mean error was 7.2mm using only TM and 1.7mm then the surrogate was used in combination with TM (due to out‐of‐plane motion, the ground truth in this has an inherent error component). Conclusions: As opposed to tracking with other imaging modalities, ANN does not perform well in MR‐guided tracking. TM, however, leads to highly accurate tracking results. Preliminary results suggest that out‐of‐plane motion could be addressed by surrogate tracking using the diaphragm, which is easily identified in the images.This work was supported by Varian Medical Systems, Inc.
SU‐E‐J‐98: PTV Margin Required for Head and Neck IGRT Derived from Deformable Image Registration
Authors: Yock A , Zhang L , Dong L 
Published: November 2011

Purpose: To reconstruct the planning target volume margin necessary in head and neck image‐guided radiation therapy. Methods: For two patients, deformable image registration was used to identify voxels of corresponding anatomy in 35 daily in‐room CTs with reference to the planning CT. The resulting vector fields were applied to the original high‐, medium‐, and low‐risk clinical target volumes to devise daily CTVs relative to the isocenter. A volume equivalent to the union of the daily CTVs was considered an effective planning target volume (PTVeff) that retrospectively provided complete geometric coverage of the original CTV while minimizing the inclusion of normal tissue. 0mm, 1mm, 2mm, 3mm, and 4mm isotropic expansions to the original CTVs (CTVexp) were compared with each PTVeff, and evaluated based on the percent coverage of PTVeff provided by CTVexp as well as the volume of normal tissue included in CTVexp but external to PTVeff. An anisotropic expansion of 1mm in the transverse plane and 2.5mm in the superior‐inferior direction was also evaluated. Results: Both the percent coverage of PTVeff provided by CTVexp and the volume of normal tissue included in CTVexp were proportional to the expanded margin. The values from the anisotropic expansion lay between those from the 1mm and 2mm isotropic expansions. For one patient, an isotropic expansion of 2mm was required to cover at least 95% of PTVeff and actually covered at least 97% for the original CTVs. For the other patient, 3mm and 4mm expansions were necessary to provide 95% coverage of PTVeff. Conclusion: Deformable image registration may be utilized to retrospectively evaluate the efficacy of various CTV margin expansions. The two patients studied demonstrated different margin requirements for the desired coverage. Additional patients will be incorporated to establish empirically derived, clinically appropriate margins.Funding provided by the University of Texas Graduate School of Biomedical Sciences at Houston.
SU‐E‐J‐156: A Feasibility Study for Real‐Time Tumor Tracking Using Positron Emission Tomography (PET)
Authors: Yang J , Yamamoto T , Thielemans K , Mazin S , Graves E , Keall P 
Published: November 2011

Purpose: To evaluate the feasibility of a real‐time position estimation algorithm using positron emission tomography (PET) and investigate the geometric accuracy of the proposed algorithm. Method and Materials:The algorithm was implemented using listmode PET and RPM respiratory tracking data acquired from a phantom programmed to move with measured respiratory traces from five human subjects, for which the ground truth target position was known as a function of time. The phantom consisted of fluid filled cylinder containing six hollow spheres of diameters 10, 13, 17, 22, 28, and 37 mm with a target background ratio of 8:1. Motion of the phantom was synchronized to respiratory motion during data acquisition. Images were continuously reconstructed with increasing acquisition time (steps of 100 msec) based on displacement gating. We evaluated the geometric accuracy of the algorithm by quantifying errors between the center of mass (COM) trajectory determined by the proposed algorithm and actual motion of the target. Results: The COM trajectory by the proposed algorithm converged to actual motion within the accuracy of 1.08±1.26 mm (average error), although shape distortion persisted due to the low number of coincidence events. The largest errors occurred 1) at the beginning of scans due to small number of coincidence events and 2) outside of gate boundaries. Better results were obtained for larger targets due to the partial volume effect. The average error over all subjects for the 10 and 37 mm targets was 1.68±1.88 mm and 0.78±0.74 mm, respectively. Conclusion: We investigated the potential to use PET for real‐time tumor tracking by estimating tumor positions. Even if a fast reconstruction algorithm is required, PET has the potential to enable real‐time tumor tracking for IGRT.This work was supported by NIH/NCI R01 93626, Stanford Bio‐X and Kwanjeong Educational Foundation (KEF) in Korea