bluuebunny/crossref_metadata_2025 huggingface dataset:
To Integrate or…? Agricultural Development in Sierra Leone
Authors: Airey A. , Binns J. A. , Mitchell P. K.
Published: August 2010

SUMMARY Semi‐subsistence peasant farming in the forest regions of Sierra Leone does not lend itself to ready understanding by western‐trained fieldworkers. But that understanding is essential if development objectives and procedures are to be successful. Some progress has been achieved through the application of systems‐based modes of analysis of detailed empirical material. Although growth in the agricultural sector has long been part of government policies, achievement has fallen short – partly at least through errors in basic philosophy. The Integrated Agricultural Development Project Eastern Area (IADPEA) may prove to be a more realistic and successful vehicle for developing, rather than replacing, traditional farm production.

RÉSUMÉ Intégrer ou …? Le développement agricole de la Sierra Leone

L'agriculture de semi‐subsistance des régions forestières de la Sierra Leone ne se prête pas facilement à l'interprétation pour des enquêteurs formés dans les pays occidentaux. Mais il est indispensable de la comprendre pour assurer le succès des procédures et objectifs de développement. Certains progrès ont pu être accomplis grâce au recours à la systématisation des modes d'analyse des données empiriques détaillés. Bien que la croissance du secteur agricole fasse depuis longtemps partie des buts du gouvernement, les résultats laissent à désirer, en partie du moins à cause d'erreurs d'orientation fondamentales. Le Projet de développement agricole intégré de la zone est (IADPEA) pourrait devenir un instrument plus réaliste, et ayant plus de chances de succès, pour développer, plutôt que pour remplacer la production agricole traditionnelle.

RESUMEN ¿ Integrar o …? Desarrollo agrícola en Sierra Leona

Las condiciones campesinas de semisubsistencia en las regiones forestales de Sierra Leona no se prestan a una fácil comprensión por parte de los expertos agrícolas entrenados en Occidente. No obstante, este entendimiento es esencial si han de llevarse a cabo de manera fructífera los objetivos y procedimientos del desarrollo. Se ha logrado cierto progreso mediante la aplicación de los análisis de materiales empíricos detallados basados en sistemas. Aunque el crecimiento en el sector agrícola ha formado parte desde hace mucho tiempo de las políticas gubernamentales, los logros han sido escasos – en parte a causa de los errores que se cometieron en la filosofía empleada. El proyecto de desarrollo agrícola integrado para la zona oriental puede que sea un vehículo para el desarrollo con bases más realistas y mayores posibilidades de triunfar, en lugar de reemplazar los sistemas tradicionales de producción agrícola.
Effect of Upstream Shear on Flow and Heat (Mass) Transfer Over a Flat Plate—Part II: Mass Transfer Measurements
Authors: Ghosh K. , Goldstein R. J.
Published: August 2010

Mass transfer measurements on a flat plate downstream of a belt moving in the same direction of the freestream study the effect of the upstream shear on the heat (mass) transfer for four belt-freestream velocity ratios. With an increase in this ratio, the “virtual origin” of the turbulent boundary layer “moves” downstream toward the trailing edge of the belt. This is verified from the variation of the Stanton number versus the Reynolds number plots. As the “inner” region of the boundary layer is removed for a belt speed of uw=10 m/s (freestream velocity uin≈15.4 m/s), a corresponding local minimum in the variation of the Stanton number is observed. Downstream of this minimum, the characteristics of the turbulent boundary layer are restored and the data fall back on the empirical variation of Stanton with Reynolds number.
Hierarchical Modeling of Heat Transfer in Silicon-Based Electronic Devices
Authors: Goicochea Javier V. , Madrid Marcela , Amon Cristina
Published: August 2010

A hierarchical model of heat transfer for the thermal analysis of electronic devices is presented. The integration of participating scales (from nanoscale to macroscales) is achieved by (i) estimating the input parameters and thermal properties to solve the Boltzmann transport equation (BTE) for phonons using molecular dynamics (MD), including phonon relaxation times, dispersion relations, group velocities, and specific heat, (ii) applying quantum corrections to the MD results to make them suitable for the solution of BTE, and (iii) numerically solving the BTE in space and time subject to different boundary and initial conditions. We apply our hierarchical model to estimate the silicon out-of-plane thermal conductivity and the thermal response of an silicon on insulator (SOI) device subject to Joule heating. We have found that relative phonon contribution to the overall conductivity changes as the dimension of the domain is reduced as a result of phonon confinement. The observed reduction in the thermal conductivity is produced by the progressive transition of modes in the diffusive regime (as in the bulk) to transitional and ballistic regimes as the film thickness is decreased. In addition, we have found that relaxation time expressions for optical phonons are important to describe the transient response of SOI devices and that the characteristic transport regimes, determined with Holland and Klemens phonon models, differ significantly.
Revisit of Laminar Film Condensation Boundary Layer Theory for Solution of Mixed Convection Condensation With or Without Noncondensables
Authors: Liao Y.
Published: August 2010

This work presents a unique and unified formulation to solve the laminar film condensation two-phase boundary layer equations for the free, mixed, and forced convection regimes in the absence or presence of noncondensables. This solution explores the vast space of mixed convection across the four cornerstones of laminar film condensation boundary layer theory, two established by Koh for pure vapor condensation in the free or forced convection regimes and the other two established by Sparrow corresponding to condensation with noncondensables. This formulation solves the space of mixed convection completely with Koh and Sparrow’s solutions shown to be merely four specific cases of the current solution.
Influence of Intense Symmetric Heating and Variable Physical Properties on the Thermo-Buoyant Airflow Inside Vertical Parallel-Plate Channels
Authors: Morrone Biagio , Campo Antonio
Published: August 2010

This paper deals with the steady, laminar, and two-dimensional natural convection inside vertical parallel-plate channels with isoflux heating. The main objective of this paper is to assess the joint influence of intense heating and variable physical properties on the flow and heat transfer characteristics of the upward air. To capture the physics of the problem, the discretized conservation equations are solved by the finite-volume technique in an aggrandized computational domain that is much larger than the physical domain. Representative numerical results based on the FLUENT computer program are presented in terms of local quantities such as air velocity and temperature profiles, as well as global quantities such as the average heat transfer coefficients and mass flow rates, all in response to the controlling geometrical and thermal parameters. A detailed comparison of these results is made against those produced by the simple model limited to constant physical properties.
SU‐DD‐A3‐03: How Accurately Can the Internal Target Volume (ITV) from a Free‐Breathing Cone Beam Computed Tomography (FB‐CBCT) Scan Be Used for Target Verification?
Authors: Vergalasova I , Maurer J , Yin F
Published: August 2010

Purpose: An internal target volume (ITV) is often identified by acquiring a free‐breathing cone‐beam computed tomography scan (FB‐CBCT) to verify patient setup of tumors affected by respiratory motion. However, its accuracy is not well understood. The purpose of this study is to characterize the potential underestimation of the ITV when a FB‐CBCT is acquired with irregular respiratory cycles. Methods & Materials: Five patient respiratory profiles were programmed into a 4D Dynamic Thorax (CIRS Model 008) phantom containing a spherical target, 2cm in diameter. The superior‐inferior motion was 3cm with respiratory cycles approximately 5 seconds in length. Five 360° CBCT scans of each profile were acquired using a gantry mounted kV imaging system. A FB‐CBCT, as well as a 4DCBCT of 10 phase bins with 10% phase windows were reconstructed for each profile. Inspiration (0%) and expiration (50%) phase images were compared to FB‐CBCT images. The ITV of each FB‐CBCT displayed a sharp and a smeared region. The percent reduction in contrast‐to‐noise ratio (CNR) between these regions was calculated, as well as the ratio of the average time spent in inspiration versus expiration. The relationship between contrast reduction and the ratio of time spent per phase was investigated. Results: For the five profiles studied, the CNR reductions ranged from 37% to 70%, corresponding to ratios of average time spent in inspiration versus expiration that ranged from 0.42 to 0.12, respectively. As the difference between time spent in expiration versus inspiration increased, the reduction in contrast also generally increased (r2=0.873). Conclusions: The observed loss of contrast in the ITV for irregular respiratory cycles may lead to the potential underestimation of this volume obtained from a FB‐CBCT. Extra caution is required when using an ITV for on‐board target localization when respiratory cycles exhibit large time differences between inspiration and expiration periods.
SU‐EE‐A3‐02: Retrospective Dose Reconstruction for Respiration‐Gated VMAT
Authors: Qian J , Choi K , Liu W , Xing L
Published: August 2010

Purpose: The Varian Trilogy MX linac allows respiration‐gated volumetric modulated arc therapy (VMAT). The aim of this work is to develop a technique to reconstruct the actual dose delivered in gated‐VMAT treatment using on‐treatment 4D cone‐beam CT (CBCT) that supplies the most updated anatomy and dynamic log‐files which record the actual leaf positions, gantry angles, and cumulative monitor units (MUs) during the delivery. Method and Materials: 4D CBCT was acquired before the dose delivery and systematic log‐files were retrieved after the gated‐VMAT delivery. Actual delivery at a control point including MLC leaf positions, gantry angles and cumulative monitor units (MUs) were recorded in the log‐files and the information was extracted using an in‐house software. The extracted information was then embedded into the original DICOM‐radiotherapy (RT) plan file to replace the original control point parameters. The reconstituted DICOM‐RT file was imported into the treatment planning system (TPS) and dose was computed on the treatment phase of the 4D CBCT. A series of 4D phantom experiments was performed to show the feasibility and efficacy of this dose reconstruction technique. Results: A dose reconstruction procedure has been established for respiration‐gated VMAT. The studies indicate that 4D CBCT‐based VMAT dose reconstruction is achievable and provides a valuable tool for monitoring the dose actually delivered to the tumor target as well as the sensitive structures. In the ideal situation where the 4D phantom is set up identically in planning CT and on‐treatment CBCT, the reconstructed dose distributions on 4D CBCT show no significant difference (<3%) from the planned. It is also elucidated that the proposed method is capable of revealing the dosimetric changes in the presence of setup errors and irregular motion during the treatment. Conclusion: The proposed methodology affords an objective means for dosimetric evaluation of newly available respiration‐gated VMAT.
SU‐GG‐I‐130: National Assessment of Research Imaging Centers for Design of the C‐TRIC
Authors: Fullerton G
Published: August 2010

Purpose: The expanding capacity of biomedical imaging devices such as CT, MRI, US, PET, SPECT to measure in vivo distributions of tissue characteristics, blood flow, molecular concentrations, and other parameters in 4 and more dimensions increases demand and cost of research imaging. Past funding at NIH and NSF favored proliferation in multiple departments and/or centers. The University of Colorado Denver (UCD) has six such independent centers. Lack of coordination caused excessive charge‐back fees and inefficiencies. The purpose of this study was to review the structure and organization of research imaging centers of excellence to recommend restructuring of UCD research imaging resources to make researchers more competitive for future funding. Methods and Materials: A planning grant from the UCD School of Medicine funded nine 1.5 day events 1) 3‐person team visits to three research imaging centers of excellence, 2) participation of three Directors of Centers as visiting Professors to UCD, and 3) consultation with the research teams of three major imaging equipment manufacturers. In addition, 36 UCD research leaders were interviewed one‐on‐one to measure need. Results: The national study of architectural plans showed that ALL major medical research centers have consolidated research imaging resources. The research in Centers of Excellence has two major goals, 1) Design and construction of new, cutting‐edge imaging instrumentation and 2) Facilitation of biomedical imaging research by investigators from medical specialties outside of radiology. Conclusions: Following presentation of this report to research faculty of the University of Colorado the decision was made to incrementally consolidate existing research imaging resources into a single operational unit and initiate the process of physically consolidating research imaging resources to increase the productivity of research projects from the Rocky Mountain region as well as the UCD Anschutz Medical Campus.
SU‐GG‐I‐138: Quantitative Fat Fraction Change in Pelvic Bone Marrow in Response to Concurrent Chemoradiotherapy
Authors: Liang Y
Published: August 2010

Purpose: To quantify changes in pelvic bone marrow (BM) fat fraction (FF) during concurrent chemoradiotherapy for patients with pelvic malignancies. Method and Materials: The study includes 6 patients with stage I–III cervical cancer and 4 patients with stage II–III anal cancer. For cervical cancer patients, treatment consisted of IMRT, 45 Gy in 1.8 Gy daily fractions with concurrent weekly cisplatin, followed by intracavitary brachytherapy boost. For anal cancer patients, treatment consisted of IMRT, 50.4–54.0 Gy in 1.8 Gy daily fractions, with concurrent 5‐fluorouracil and mitomycin C. All patients underwent CT simulation and baseline quantitative FF magnetic resonance imaging (MRI) with the technique called Iterative Decomposition of water and fat with Echo Asymmetry and Least‐Squares Estimation (IDEAL) within 3 weeks of initiating CRT. In addition, patients underwent mid‐ (week 3–4) and post‐treatment (week 6–7) MRI‐IDEAL scans. Rigid image registration was applied to the pre‐, mid‐, post‐ treatment FF image volume, using a commercial software Velocity AI (Velocity Medical Solutions, Atlanta, GA), to achieve accurate alignment and account for local heterogeneity in red BM. Results: All 10 patients had the baseline MRI‐IDEAL scans. All 6 cervical cancer patients and 3 anal cancer patients had mid‐treatment scans. And 4 cervical cancer patients and 2 anal cancer patients had post‐treatment scans. The mean pelvic bone FF of the cervical cancer patients at pre‐, mid‐, and post‐ treatment were 46%, 61%, and 72%, respectively. The mean pelvic bone FF of the anal cancer patients at pre‐, mid‐, and post‐ treatment were 63%, 72%, and 68%, respectively. Conclusion: Pelvic BM FF increases significantly during chemoradiation for pelvic malignancies. As a putative indicator for functional BM, this imaging technique may be useful for guiding IMRT plans and for quantifying local changes in BM resulting from treatment.
SU‐GG‐I‐152: Rapid Evaluation of X‐Ray/Light Field Alignment for Digital Radiographic Systems
Authors: Hoerner M , Hintenlang D
Published: August 2010

Purpose: This study investigated the development of a device to rapidly quantify x‐ray and light field alignment. The device is a useful alternative to traditional measurement techniques requiring film and is particularly useful for all‐digital facilities that no longer have film processors. The system that is investigated provides rapid and accurate evaluation of the difference between x‐ray and light fields. Method and Materials: A fiber‐optic coupled (FOC) dosimetry system was adapted to evaluate the misalignment between the light and x‐ray fields of mammography imaging systems. An FOC detector element providing a variable output as a function of exposed dosimeter length is used to measure the deviation of each side of the X‐ray/light field. Each detector element incorporates two FOC dosimeters which were constructed by coupling plastic scintillator fibers, 500 microns in diameter, one 2mm and the other 5cm in length, to sensitive photomultiplier tubes (PMTs). The detector element is positioned such that the 5 cm dosimeter intersects the edge of the light and X‐ray fields. The second dosimeter (2mm) is positioned entirely in the X‐ray field to provide a relative measure of beam intensity. Characterization involved varying the length of the 5 cm dosimeter exposed within the x‐ray field. Results: The system consistently demonstrated linearity with tube output and exposed length. Trials have shown a linear response of detected counts to length of scintillation material in the light field over the range of interest. The system's spatial resolution is evaluated and characterized for a variety of exposure parameters. Conclusion: Multiple PMTs allow all edges of the light field to be evaluated simultaneously, permitting x‐ray/light field alignment for a typical digital mammography system to be completed in approximately ten minutes. The time savings and improved accuracy over current alternatives makes the device an attractive tool for digital mammography quality control.
SU‐GG‐I‐158: A Comparison of F‐18 FDG‐PET Imaging in Differential Diagnosis of Alzheimer's Disease with Parkinsonism and Dementia with Lewy Bodies Disease
Authors: Juh R , Suh T , Kim S
Published: August 2010

Purpose: Dementia with Lewy bodies (DLB) is the second most common cause of degenerative dementia after Alzheimer's disease (AD). The aim of this study was to investigate the diagnostic value of metabolism in the diagnosis of DLB and AD in comparison with [F‐18]fluoro‐2‐deoxy‐D‐glucose(FDG)—PET imaging. Investigations which could help improve the accuracy of discrimination between DLB and AD would be a major advance. Methods: All Subjects underwent 18F‐FDG‐PET and MRI. We compared regional cerebral metabolic images by a voxel‐by‐voxel analysis with statistical parametric mapping (SPM) among DLBD, AD and NC subjects, and evaluated differences of hypometabolic regions. All PET scans be visually rated from equivalent slices, each image volume was registered to match a 18F‐FDG‐PET template in standard MNI (Montreal Neurological Institute) space using statistical parametric mapping. Accurate normalization is essential for quantitative pattern analysis to neurodegenerative disease; the cerebellum or pons was often used as a reference region in the MR image, which assumed no significant regional influence of physiological fluctuations for quantitative. Results: 18F‐FDG‐PET revealed evidence of diffuse hypometabolism in both DLBD and AD with Parkinsonism marked declines in association cortices with relative sparing of subcortical structures and primary somatomotor cortex, a pattern reported previously in AD. Unlike AD, DLBD subjects also had hypometabolism in the occipital association cortex and primary visual cortex. Significant changes in hypometabolism in the volume of interest were assessed in the posterior cingulate gyrus, precuneus and parietal cortices. The severity of the decrease in metabolism in AD patients was significantly greater than in vascular dementia and frontotemporal dementia patients and controls. Conclusion: These findings indicate the presence of diffuse cortical abnormalities in DLBD and suggest that FDG‐PET may be useful in discriminating DLBD from AD.
SU‐GG‐I‐162: Development and Verification of Functions Correlating PET Image Noise to Scan Duration and Image Smoothing for Patients with Different BMI
Authors: Chang T , Chang G , Clark J , Mawlawi O
Published: August 2010

Objectives: PET image noise is affected by scan duration (SD), image smoothing (IS) and patient BMI. The aim of this abstract is to develop and verify functions that describe the inter‐relationships among these variables. Methods: 50 patients were imaged on a GE DRX PET/CT scanner. These patients were divided into 5 BMI ranges: <20, 20–25, 25–30, 30–35 and >35kg/m2, resulting in 10 patients/subgroup. PET images of the bed position covering the patient liver were acquired in 3D for 5 minutes using LIST mode and then rebinned into 5 SD ranging from 1 to 5min with 1min interval. Each PET acquisition was then reconstructed using 3D OSEM (2 iterations 21 subsets) with varying Gaussian post filter (6, 8 and 10mm FWHM). Image noise in the liver (measured in units of g/ml) was determined as the STD of a fixed‐size VOI for each patient BMI, SD, and IS. Functions correlating the image noise to the SD & IS for each BMI subgroup were then generated. These functions were verified using data from 4 other patients (2 with BMI 20–25, 2 with BMI 30–35) that had PET SD and IS ranging from 1 to 9min with a 2min intervals and 5 to 13mm with a 2mm interval respectively. The verification was based on comparing the noise in these 4 patients' liver at each SD and IS to that determined from the derived functions. Results: The inter‐relationship among noise, SD, and IS has the following functional form: noise=k1−k2/(SD)0.5−k3/IS+k4/(SD)0.5/IS. The average difference of the noise between the 4 additional patients and the derived function is −0.0136±0.0289 g/ml. Conclusion: We derived unique and robust functions correlating PET image noise to SD and IS for patients with different BMI. These functions can be used to optimize image quality by minimizing image noise for patients with different BMIs.
SU‐GG‐I‐164: Flies for PET: An Artificial Evolution Strategy for Image Reconstruction in Nuclear Medicine
Authors: Vidal F , Louchet J , Rocchisan J‐M , Lutton E
Published: August 2010

Purpose: We propose an evolutionary approach for image reconstruction in nuclear medicine. Our method is based on a cooperative coevolution strategy (also called Parisian evolution): the “fly algorithm”. Method and Materials: Each individual, or fly, corresponds to a 3D point that mimics a radioactive emitter, i.e. a stochastic simulation of annihilation events is performed to compute the fly's illumination pattern. For each annihilation, a photon is emitted in a random direction, and a second photon is emitted in the opposite direction. The line between two detected photons is called line of response (LOR). If both photons are detected by the scanner, the fly's illumination pattern is updated. The LORs of every fly are aggregated to form the population total illumination pattern. Using genetic operations to optimize the position of positrons, the population of flies evolves so that the population total pattern matches measured data. The final population of flies approximates the radioactivity concentration. Results: We have developed numerical phantom models to assess the reconstruction algorithm. To date, no scattering and no tissue attenuation have been considered. Whilst this is not physically correct, it allows us to test and validate our approach in the simplest cases. Preliminary results show the validity of this approach in both 2D and fully‐3D modes. In particular, the size of objects, and their relative concentrations can be retrieved in the 2D mode. In fully‐3D, complex shapes can be reconstructed. Conclusions: An evolutionary approach for PET reconstruction has been proposed and validated using simple test cases. Further work will therefore include the use of more realistic input data (including random events and scattering), which will finally lead to implement the correction of scattering within our algorithm. A comparison study against ML‐EM and/or OS‐EM methods will also need to be conducted.
SU‐GG‐J‐42: Development of an EPID‐Based Machine and IMRT QA System
Authors: Chen X , Shi C , Buckey C , Stathakis S , Alkhatib H , Papanikolaou N
Published: August 2010

Purpose: Interests in electronic portal imaging devices (EPIDs) for radiation dosimetry increase over the past decade, particularly with recent technique advances in amorphous‐silicon EPID. For a clinical quality assurance (QA) program, EPIDs may provide a useful tool with benefits of reduced cost and added convenience, e.g., shortening setup time. This study is to investigate the clinical application of EPID in routine machine and IMRT QA and develop an EPID‐based QA system. Materials and Methods: EPID images were acquired using Varian aS1000 EPID (integrated mode; 6 MV beam; 600 MU/min dose rate). Signal intensity of EPID images were converted to dose maps using a calibrated linear signal‐dose relationship. An integrated EPID‐based QA system was designed, which include functions for machine QA and IMRT QA. For routine machine QA, recommendations by TG‐40 and TG‐45 reports were used. Specific EPID‐based QA procedures and image analysis algorithms were designed and developed for basic QA tasks, e.g., beam flatness/symmetry test and Winston‐Lutz isocenter test. For IMRT QA, a phantom‐less method was proposed, which used fluence maps reconstructed from EPID‐measured fluence as input to treatment plan system for dose calculation and comparison. Results: EPID‐measured machine QA results were comparable to those measured monthly using films in our institute. For example, EPID‐measured parameters were: flatness = 0.9–1.45%; symmetry = 0.48–1.31%; penumbra = 3.2–4 mm at SSD = 150 cm. Star‐shot images were well reconstructed for isocenter check from EPID images acquired at different gantry or collimator angles. The EPID‐based IMRT QA method was able to verify the treatment plan and capture the reasonable plan‐versus‐QA dose difference. Conclusion: The results show that EPID may be properly used as a tool for clinical QA tasks and the developed EPID‐based QA system may be used for machine and IMRT QA. (Research sponsored by Oncology Data Systems, Inc, Oklahoma City, OK)
SU‐GG‐J‐46: Lower Spinal Cord Dosimetric Effects of Upper Field Image‐Guided Alignment in Split‐Field EMRT Technique
Authors: Yock A , Zhang L , Garden A , Rosenthal D , Dong L
Published: August 2010

Purpose: To investigate the lower spinal cord dosimetric effects of setup errors in split‐field head and neck radiation therapy which persist after upper field daily bone alignment (IGRT) due to body rotation and non‐rigid anatomy. Method and Materials: Information from twelve patients who underwent daily CT‐guided radiation therapy was used to evaluate lower field dosimetric margins. Cumulative dose distributions were calculated by mapping daily dose from IGRT alignment onto the planning CT. Lateral dose profiles were measured across the blocks of the larynx and spinal cord. The profile inflection points marked the dosimetric field edges of the blocks. The midpoint between the field edges of the original plan was defined as the block center. The dose gradients at the field edges were measured and compared with the original plan to indicate penumbra variation. Results: Cumulative dose to the lower cord never exceeded 40.5Gy. The average lateral shift of the field edge was 0.6mm (σ=1.7mm; range: −3.0mm to 4.0mm) and 0.4mm (σ=1.6mm; range: −3.5mm to 3.5mm) for the larynx and spinal cord, respectively. The magnitude of the edge gradient increased on average −4.97Gy/mm (σ=4.01Gy/mm; range: −12.1Gy/mm to 1.31Gy/mm) and −0.74Gy/mm (σ=1.43Gy/mm; range: − .59Gy/mm to 3.03Gy/mm) for the larynx and spinal cord, respectively. Conclusion: Despite residual setup errors after upper field alignment, the lower field treatment is safe and clinically acceptable. The field edge shift was observed to be as large as 4mm, however the lower cord remained within the dose shadow of the cord block. Motion induced dose smearing was also observed to decrease the steepness of the edge gradient by nearly 5Gy/mm.
SU‐GG‐J‐51: A New Image Guided Radiation Therapy Scheme Using Spatially Weighted Mutual Information Image Registration and a Semi‐Automatic PET Segmentation Tool
Authors: Park S B , Sohn J W
Published: August 2010

Purpose:_To enhance the automatic image registration process for Image Guided Radiation Therapy (IGRT) using biological information acquired by PET imaging. Methods and Materials: We developed an image registration tool which is incorporated with a three‐dimensional semi‐automatic segmentation tool for Positron Emission Tomography (PET) image set. Firstly we registered PET image set to the planning CT image set. Contours for the high uptake volumes were generated by a semi‐automatic segmentation tool. User can choose an intensity profile with a pointing device in Graphical User Interface. Then, region growing algorithm was utilized. Threshold for segmentation can be adjusted in GUI. We exported the segmented volumes and fused into a DICOM‐RT structure set generated in a planning CT. We formulated Spatially Weighted Mutual Information (SWMI) image registration with Structure‐Of‐Interest (SOI) based weight function (SWMI‐SOI) because assigning various importance weight values to geometric locations is not possible with mutual information image registration. SWMI method allows the user can assign the importance weights through the geometric space. A user can choose how much importance weight will be assigned to each SOI. We expanded the organ contours so that each SOI included enough image features such as organ edges. We assigned the higher importance value to Clinical Target Volumes (CTV) and the Organs‐At‐Risks (OAR). The highest importance value was assigned to the volumes which were delineated using PET segmentation tool. Lower weight values were assigned to other structures so that they would not dominate the registration. This insures that PET defined volumes will get a full treatment dose in every fraction. Results and Discussion: We successfully used biological information in IGRT process and SWMI‐SOI registration algorithm. Our method showed consistency between users and was very useful when multiple lesions were considered during image registration process. Further clinical research is necessary to determine optimal weight assignment.
SU‐GG‐J‐77: The Use of a Commercial Quality Assurance Device for Daily Output and Positioning Checks of Three Image‐Guided Stereotactic Positioning Systems
Authors: Peng J , Kahler D , Li J , Liu C
Published: August 2010

Purpose: To develop a simple, comprehensive daily QA program for a linac and three image‐guided stereotactic positioning systems (IGSPSs) and to summarize the results over extended periods. Method and Materials: The daily output check on a linac is commonly performed utilizing a chamber embedded in a phantom. Three IGSPSs; the AlignRT 3D surface imaging system, the Frameless SonArray System (FSA), and the Elekta kV CBCT are installed in a treatment room housing an Elekta linac. For daily QA, therapists routinely perform dosimetric checks of the linac and geometric accuracy tests of the IGSPSs using different vendor‐provided phantoms. We investigated the feasibility of using the commercially available Sun Nuclear DailyQA3™ (DQA3) phantom to perform this task. The QA program encompasses three components: dosimetry, mechanical, and imaging geometry. Results:The coincidence of the isocenter coordinate for AlignRT, FSA, and the linac mechanical isocenter was within 0.7 mm/0.6° of that of the CBCT system. We used the three imaging systems to inspect the laser alignment and optical distance indicator, which each localized to within 0.5 mm. For gantry and table angles of 0°, the mean displacement vectors were within 0.4 mm and 0.1° for each axis between systems. The differences in couch angles using AlignRT and FSA were within 0.3°. Over a period of eight months, the output remained within 2%, the photon and electron energy remained within 2%, and the symmetry and flatness remained within 1%. The field size and light‐radiation field coincidence were within 1mm. The total measurement time for each QA session took 20 minutes or less. Conclusion: The use of the DQA3 simplifies daily QA measurements, shortening the set‐up time, and eliminating systematic errors introduced by switching phantoms. Clinical use of this device has improved the efficiency and thoroughness of our daily QA program for both the linacs and the IGSPSs.
SU‐GG‐J‐109: A Study on Image Guided Radiotherapy Using Cone‐Beam Computed Tomography (CBCT) for Head and Neck Cancer IMRT Patient Setup
Authors: Tang X , Chera B , Lian J , Deschesne K , Chang S
Published: August 2010

Purpose: To use our CBCT shift results to determine how much of the CTV to PTV margin is necessary to compensate for the daily setup uncertainty inherent in the treatment of head and neck cancer patients. Method and Materials: To accommodate the daily setup uncertainly, a 3–6 mm uniform margin is used for head and neck IMRT patients to expand CTV to PTV. In order to verify patient setup accuracy, CBCT is taken prior to the treatment. Our protocol calls for CBCT for the first five consecutive fractions, followed by two CBCT every week. Each CBCT is registered to the planning CT to determine the corresponding translational shift. The registration is based on the region‐of‐interest—the rigid bones near the tumor. On the days no CBCT is taken, the average of the previous three calculated translational shifts is used instead. No rotational correction is considered. Results: A total of 22 head and neck IMRT patients were studied with a Siemens Artiste linear accelerator using an MVision CBCT scanner. Each patient had approximately 14 sets of CBCT images taken over the entire course of treatment. The average interfraction shift was 0.6±1.6, 1.4±1.5, 0.1±1.6 mm in the anterior‐posterior, left‐right, and superior‐inferior dimensions, respectively. These data indicate that in the absence of CBCT image guided radiotherapy, a CTV to PTV margin of 2.5, 4.7 and 1.3 mm is needed in the anterior‐posterior, left‐right, and superior‐inferior dimensions, respectively. Conclusion: Our results have shown that asymmetric margins of 2.5, 4.7 and 1.3 mm can be used for CTV to PTV expansion for head and neck cancer radiotherapy if no IGRT presented. Our CBCT protocol will allow a reduction in the CTV to PTV margin. Further investigation needs to be done to find out the specific CTV to PTV margin with different CBCT frequency.
SU‐GG‐J‐113: Considering Respiration Motion in Radiation Treatment Planning for Pancreatic Cancers
Authors: Liang Z , Tai A , Erickson B , Kelly T , Li X
Published: August 2010

Purpose: To quantify respiration induced organ motions for pancreatic cancer patients and to explore strategies to account for these motions in the treatment planning using 4DCT.Method and Materials: Both 3DCT and 4DCT scans were acquired sequentially for ten pancreatic patients using a CT scanner (LightSpeed, GE). The 4DCT data were sorted into ten respiratory phases. The 3DCTs were fused with 2 sets of 4DCT data at the end of exhale phase (50%) and the end of inhale phase (0%). The target (pancreas) was delineated on the 50%‐ and 0%‐phase CT sets and the organs at risk were drawn on the 3DCT. These contours were populated to the CT sets at other respiratory phases by a software (ABAS, CMS Inc) based on deformable image registration. The ABAS‐generated contours were carefully reviewed and manually modified if necessary. Internal target volumes (ITV) were generated by tracing the target contours of all phases (ITV10), three phases of 0%, 20% and 50% (ITV3) and two phases of 0% and 50% (ITV2) with a zero margin. Results: Volume variations of pancreas, kidney and liver were found to be small (<5%) during respiration. The centriod motions of liver, left kidney, right kidney and the target in the superior‐inferior direction were 7.9±3.2 mm, 7.1±3.1 mm, 5.7±3.2 mm and 5.6±2.7 mm, respectively. The volume overlap and dice coefficient were 92%±1% and 96%±1% between ITV10 and ITV2 and 95%±1% and 98%±1% between ITV10 and ITV3, respectively. It was found that the positions of the liver and kidneys on the images of 3DCT and 20% of phase are similar. Conclusion: Respiration motion for target can be accounted for by using ITV generated based on CTs acquired at the ends of exhale and inhale. The 4DCT at mid exhale (20%) may be used for treatment planning as a substitute of 3DCT.
SU‐GG‐J‐123: Dose Increase in Radiotherapy Evaluated to Biocompatible Levels of Gold Nanoparticle: A Quantitative Analysis by MRI Gel Dosimetry and Monte Carlo Spectrometry
Authors: Marques T , Schwarcke M , Garrido C , Zucolotto V , Baffa O , Nicolucci P
Published: August 2010

Purpose: Apply gel dosimetry to evaluate the dose‐increase dependency with nanoparticle concentration in a tissue‐simulator dosimeter irradiated with 250kV Radiotherapy beam. Quantify the components of dose contribution by Monte Carlo spectrometry. Material and Methods: Gold nanoparticles (AuNP) were embedded in MAGIC‐f gel in different biocompatible concentrations: 0.11mM(A), 0.06mM(B) and 0.03mM(C). Dosimetric control measures with gel without AuNP were made in the 250kV x‐ray beam studied. An acrylic box was positioned behind the gel samples to guarantee backscattered conditions similar to clinical situations accessed with the beam studied. A dose of 5Gy was delivered to all samples. Polymer gel readings were proffered in a 3Tesla nuclear‐magnetic‐resonance by relaxometry: 5 echoes; Echo‐time=20ms; Repetition‐time=4000ms; Pixel‐size=250μm; Time‐delay‐to‐reading: 12h. Monte Carlo simulations were performed in PENELOPE code precisely reproducing all experimental conditions. Results: Signal of non‐irradiated gel samples (with and without AuNP) presents no significant variation (<0.5%), evidencing no influences of AuNP in MRI reading. Concentrations A, B and C presents a 106%, 90% and 77% of signal increase, respectively. Comparing with the dose calibration curve of gel, the signal growth represents dose enhancements of 5.3Gy, 4.5Gy and 3.9Gy to concentrations A, B and C respectively. Monte Carlo shows a dose increase of 10.2keV/g, 9.1eV/g and 7.3eV/g, representing 105%, 93% and 75% of perceptual dose growth to concentrations A, B and C respectively. Spectrometry analysis revel a fluorescence dose fraction that contributes to dose increase of 0.98, 0.89 and 0.73 and low‐energy Compton events that contributes to local dose increase in fractions of 0.66, 0.38 and 0.12 to concentrations A, B and C respectively. Conclusions: Dose increase in Radiotherapy due to AuNP presence has a non‐linear dependency with the concentration. The growth of local doses may be high expressed indicating possible clinical benefits of using AuNP added Radiotherapy.
SU‐GG‐J‐131: Immobilization Bed for Multi‐Modality Image Registration
Authors: Nelson G , Bazalova M , Vilalta M , Perez J , Graves E
Published: August 2010

Purpose: To construct an immobilization bed for mice that will allow for longitudinal multimodality imaging studies as well as conformai radiotherapy. The bed must be capable of both intra‐examination immobilization as well as inter‐examination positioning reproducibility. It must also accommodate mice of various sizes and facilitate image registration. Method and Materials: An immobilization bed was manufactured from clear acrylic to enable use with optical imaging modalities. Measurements of multiple mice of various ages and species were made in order to find the optimal size for the bed and for the restrainer pegs. The pegs were placed in stationary positions that effectively immobilize the majority of mice and enable high throughput imaging by avoiding adjustments for every mouse. The pegs were placed such that the front legs of the subject are each placed between two pegs as are the hind legs. An additional set of pegs were placed laterally and posteriorly to guide the hind legs in a reproducible direction. Na‐22 PET/CT fiducials were put into the pegs at unique depths to provide a three‐dimensional reference to allow fast and accurate image registration. Results: An average sized nude mouse without anesthesia (a worst case scenario test) was only capable of 3mm of movement vertically. Serial CT scans in‐between which the bed was moved showed no shifts in bony anatomy or external soft tissues. When PET and CT scans were registered without use of the fiducials, the heart was misplaced medially by ∼1mm and inferiorly by ∼1mm. The fiducials have allowed for accurate CT registration. Conclusion: The bed is effective in immobilization and image registration. The use of this bed will be enable the elucidation of minute changes in the PET scans and the use of molecular imaging data for radiation treatment planning and followup.
SU‐GG‐J‐140: Magnetic Resonance Spectroscopy of the Prostate: One Institutional Experience
Authors: Hossain M , Buyyounouski M , Richardson T , Schirmer T , Chen L , Ma C
Published: August 2010

Purpose: Tumor volume is an important predictor of patient outcome following radiotherapy for prostate cancer. Previously, we have shown that the percentage of adenocarcioma in the pretreatment biopsy specimen predicts for biochemical failure and local persistence of disease following radiotherapy. The purpose of this study is to determine the correlation of magnetic resonance spectroscopic imaging (MRSI) to the percentages of adenocarinoma in pretreatment biopsy and the predictive ability of the former. Method and Materials: Twenty two patients underwent transrectal ultrasound guided biopsy of the prostate and MRSI. For each patient, the percentage of adenocarcinoma (PAC) was calculated using a weighted average of the core length involvement in the specimen from each of six regions, namely, the right and left half of base, middle, and the apex regions of the prostate. MRSI was performed with a GE 1.5T MRI scanner (typical voxel size is 0.33 cc, TR=1000 ms, TE=130 ms). MRSI data was acquired using the PROSE protocol. Volume‐averaged ratio of choline and creatine to citrate (CC/Ci) was taken over the six regions of the prostate. Results: Unprocessed data show a correlation of 0.31 between CC/Ci and PAC. The sensitivity and specificity of CC/Ci is found to be 70% and 69%. A cutoff value of CC/Ci=l .0 or higher may predict radiotherapy failure. Areas of the prostate with CC/Ci values higher than the cutoff can be boosted to a higher dose or can be used as guidance for performing targeted biopsy. Conclusion: There is a correlation between the various PAC, predictors of treatment failure, and the CC/Ci. CC/Ci may be able to predict radiotherapy failure or identify areas of the prostate for dose escalation.
SU‐GG‐J‐146: Evaluation of Parotid Density Changes during IMRT of Head‐And‐Neck Cancer
Authors: Cheung J , Chen YP , Lindberg ME , Cannon B , Dong L
Published: August 2010

Purpose: To evaluate the change in parotid gland density over the course of treatment for patients who have undergone adaptive radiation therapy to the head‐and‐neck. Method and Materials: Computed tomography (CT) images from sixteen patients were analyzed to assess the change in mean parotid density and parotid volume over the course of treatment. Daily CT images were acquired for a group of patients treated with adaptive radiation therapy using a CT‐on‐rails unit. A total of 529 CT scans (∼33 fractions per patient) were analyzed. Parotid contours were deformed from the planning CT to each treatment day CT image using an in‐house deformable image registration tool. The parotid volume, and average and standard deviation in CT number (HU) were obtained for each treatment fraction. Linear regression analysis was performed with a 95% confidence interval to determine the rate and trend of parotid density change. The Pearson correlation coefficient was used to evaluate possible correlations with parotid volume and function measurements. Results: Eleven of the sixteen patients showed a steady decrease in density for both parotids over the course of treatment. Two patients showed a steady decrease only in their ipsilateral parotid. The linear regression analysis for this subset of patients (p‐value <0.01) revealed an average rate of decrease of 0.30 HU/fraction (range 0.13–0.70 HU/fraction). The density reduction correlated well with parotid volume change (in 24/32 instances), and was moderately correlated with patient follow‐up saliva‐flow measurements (9 patients, correlation coefficient range 0.27–0.63) for the first two follow‐up appointments. Conclusion: The mean parotid density decreased steadily and correlated well with the volume shrinkage in most patients observed in this study. In the limited available data, the density change also correlated with saliva‐flow, which warrants future studies with a larger patient population and additional treatment parameters.
SU‐GG‐J‐149: Feasibility of In‐Room PET Imaging for in Vivo Proton Beam Range Verification
Authors: España S , Zhu X , Daartz J , Liebsch N , El Fakhri G , Bortfeld T , Paganetti H
Published: August 2010

Purpose: Investigating the advantage of in‐room PET imaging for in‐vivo range verification in proton therapy in comparison with an off‐line protocol. Considering in‐room data acquisition, the signal from short‐lived 15O (t1/2=2.03 min) isotopes, which are dominant in soft tissues, can be measured and 11C (t1/2=20.33 min) signal is increased. Furthermore, the movement of the patient during the PET scanning as well as the biological washout is minimized. Method and Materials: Two patients were scanned with a mobile PET scanner designed for neurological studies, NeuroPET, 2–3 minutes after the irradiation of a single field fraction (2Gy(RBE)) with passive scattering proton therapy. For each patient, two PET scans were acquired after two treatment sessions ∼1 week apart, with the same treatment plan. The scanner was positioned into the treatment room and for the PET scan the patient remained on the treatment couch for the PET scan, which had to be rotated and shifted from the treatment position. Measured and calculated (GEANT4 simulation of the nozzle and patient delivery) PET images were compared to evaluate the range verification accuracy. Results: A very similar number of coincidences were obtained for the in‐room (2 min delay, 5 min PET scan) and off‐line (17 min delay, 30 min scan) measurements. A ten‐fold increase of the count rate at the beginning of the acquisition on in‐room measurements has been observed due to the contribution of the 15O. A mean difference up to 5 mm has been observed between falloff positions of in‐room and off‐line images. Conclusions: We have identified an optimal timeframe for compromising signal strength versus noise. Experimental and calculational uncertainties are being reduced for future patient studies by means of a better co‐registration accuracy, attenuation correction, washout model, and conversion from CT numbers into tissue materials.