bluuebunny/crossref_metadata_2025 huggingface dataset:
The Politics of Primary Health Care
Authors: Segall Malcolm
Published: August 2010

SUMMARY All three main elements of the primary health care (PHC) approach — the alleviation of poverty, popular involvement, and health sector reform — involve issues of conflicting social interests, which explain the present slow pace of progress in most countries. The political character of PHC should now be made more explicit to legitimate and support the struggles of PHC protagonists to see official words translated into actual deeds. Six lines of action are discussed.

RESUMEN Las políticas de atención primaria de salud

Los tres elementos principales del enfoque de la atención primaria de salud — el alivio de la pobreza, la incorporación popular y la reforma del sector — involucran intereses sociales conflictivos, hecho que explica el lento progreso que ha tenido en la mayoría de los países. El carácter político de la atención primaria de salud, debería hacerse más explícito ahora, para legitimar y apoyar las luchas de sus protagonistas y, de este modo, ver las palabras oficiales convertidas en realidad. Se examinan seis líneas de acción.

RESUMES La polítique de l'assistance médicale primaire

Les trois principaux éléments d'approche de l'assistance médicale primaire qui sont: ‐l'allégement de la pauvreté, l'engagement populaire et la réforme du secteur de la santé‐, impliquent des controverses nées d'intérêts sociaux en conflit, ce qui explique le lent pas du progrès dans beaucoup de pays, actuellement. Le caractère politique de l'assistance médicale primaire devrait maintenant être rendu plus explicite pour légitimer et supporter les luttes des protagonistes du projet, pour voir la parole officielle traduite en actes réels. Six voies d'action sont présentées.
Third World Initiatives on Pharmaceuticals: a documentation for the record
Authors: Patel Surendra J.
Published: August 2010

SUMMARY The search for rational and equitable pharmaceutical policies has become a worldwide concern in recent years. The Third World countries, particularly through the non‐aligned conferences, have played a key role in bringing this about. They have provided the needed impetus for the development of essential drug lists, bulk buying, use of generic names, and the abolition or dilution of patent and trade mark rights. Their most recent contribution has been to focus international attention on the need for norms and standards in promotion, distribution, trade, and technology in the pharmaceutical sector.

RESUMEN Iniciativas del Tercer Mundo en fármacos: una documentación para el archivo

La búsqueda de una política farmacéutica racional y equitativa se ha transformado en una preocupación mundial en los años recientes. El Tercer Mundo, especialmente en las conferencias de países no alineados, ha desempeñado un rol clave impulsando el desarrollo de listas de medicamentos esenciales, las compras a granel, el uso de nombres genéricos y la abolición de los derechos y patentes de los productos comerciales. Su aporte más reciente consiste en haber concentrado la atención internacional en la necesidad de establecer normas y patrones en la promoción, distribución, comercio y tecnología en el sector farmacéutico.

RESUMES Initiatives du Tier‐Monde sur les pharmaceutiques: une documentation pour le dossier

La recherche pour une politique pharmaceutique rationnelle et équitable est devenue, ces dernières années, d'un intérêt mondial. Les pays du Tiers‐Monde, particulièrement pendant la conférence des non‐alignés, ont joué un rôle clé à cet égard. Ils ont fourni l'impulsion nécessaire pour l'élaboration d'une liste de drogues essentielles et d'autres éléments informatifs sur l'achat massif, l'utilisation des noms génériques et l'abolition ou l'affaiblissement des patentes et des droits de la marque de fabrique. Leur plus récente contribution a été de concentrer l'attention sur le besoin d'un système de normes et de standardisation dans la promotion, la distribution, le commerce et la technologie dans le secteur pharmaceutique.
Histopathology of insulin‐induced laminitis in ponies
Authors: ASPLIN K. E. , PATTERSON‐KANE J. C. , SILLENCE M. N. , POLLITT C. C. , Mc GOWAN C. M.
Published: August 2010

Reasons for performing study: Ponies with laminitis associated with insulin resistance and hyperinsulinaemia lack systemic and/or intestinal inflammatory signs, suggesting a different pathogenesis potentially reflected in differing histopathology.

Objectives: To describe the histological appearance and quantify morphological changes in primary and secondary epidermal lamellae (PEL and SEL) of laminitis lesions from ponies with insulin‐induced laminitis.

Methods: Equine hoof lamellar tissue was obtained from 4 control ponies and 5 ponies with laminitis induced following infusion of insulin (1036 ± 55 µU/ml) while maintaining euglycaemia for 55.4 ± 5.5 h. Sections from all 4 hooves were stained and examined by a veterinary pathologist. Measurements of lamellar length (PEL and SEL) were made in mid‐dorsal sections of the right forefeet by 2 blinded observers. Immunolabelling for calprotectin was performed using a monoclonal antibody.

Results: No lesions were detected in normal ponies. Lesions detected in ponies with laminitis were variable in severity between ponies. Within ponies, SEL lesions were more severe along the axial region of PEL. Lesions included swelling, disorganisation and abnormal keratinisation of epidermal cells, increased mitotic activity and apoptosis. Separation of basement membranes was minimal. Immunostaining revealed inflammatory cells within the lamellar dermis. SEL were significantly elongated in laminitic hooves relative to controls, with the greatest elongation in those attached to abaxial and middle regions of PEL.

Conclusions: Laminitis induced by prolonged infusion of insulin lacked widespread basement membrane disintegration, and increases in epidermal cellular proliferation at axial aspects were marked for this acute stage of disease.

Potential relevance: Defining equine laminitis entirely in terms of separation of the basement membrane may not be appropriate for laminitis associated with hyperinsulinaemia.
The Classical Nature of Thermal Conduction in Nanofluids
Authors: Eapen Jacob , Rusconi Roberto , Piazza Roberto , Yip Sidney
Published: August 2010

We show that a large set of nanofluid thermal conductivity data falls within the upper and lower Maxwell bounds for homogeneous systems. This indicates that the thermal conductivity of nanofluids is largely dependent on whether the nanoparticles stay dispersed in the base fluid, form large aggregates, or assume a percolating fractal configuration. The experimental data, which are strikingly analogous to those in most solid composites and liquid mixtures, provide strong evidence for the classical nature of thermal conduction in nanofluids.
Thermal Characterizations of Fin-Thin Film Systems
Authors: Khaled A.-R. A.
Published: August 2010

This work considers heat transfer in fin-thin film systems. Two types of these systems are analyzed: (A) a thin film sandwiched between two identical fin halves, and (B) a fin sandwiched between two identical thin films. The corresponding coupled energy equations are solved numerically by an implicit, iterative, finite-difference scheme. Comparisons with derived approximate closed-form solutions are performed and good agreement is obtained. A parametric study of all involved parameters is conducted and presented graphically. Useful correlations containing the various physical parameters for both types are reported. It is found that thermal efficiencies of fins can be increased significantly by introducing an internal flow inside the fin material. Moreover, factors producing more internal convections are found to increase the fin-thin film thermal efficiency. In addition, thermal efficiencies of type A systems are found to be higher than those of type B systems. Moreover, the resulting system thermal efficiency is found to have at most one local maximum and one local minimum over the whole relative heights ratio spectrum. Finally, this work paves a way for an effective combined passive and active method for enhancing heat transfer.
Entropy Generation in Thin Films Evaluated From Phonon Radiative Transport
Authors: Bright T. J. , Zhang Z. M.
Published: August 2010

One of the approaches for micro/nanoscale heat transfer in semiconductors and dielectric materials is to use the Boltzmann transport equation, which reduces to the equation of phonon radiative transfer under the relaxation time approximation. Transfer and generation of entropy are processes inherently associated with thermal energy transport, yet little has been done to analyze entropy generation in solids at length scales comparable with or smaller than the mean free path of heat carriers. This work extends the concept of radiation entropy in a participating medium to phonon radiation, thus, providing a method to evaluate entropy generation at both large and small length scales. The conventional formula for entropy generation in heat diffusion can be derived under the local equilibrium assumption. Furthermore, the phonon brightness temperature is introduced to describe the nature of nonequilibrium heat conduction. A diamond film is used as a numerical example to illustrate the distribution of entropy generation at the walls and inside the film at low temperatures. A fundamental knowledge of the entropy generation processes provides a thermodynamic understanding of heat transport in solid microstructures; this is particularly important for the performance evaluation of thermal systems and microdevices.
SU‐DD‐A2‐02: Repair Kinetic Considerations in High‐LET Particle Beam Radiotherapy
Authors: Carabe‐Fernandez A , Dale R , Paganetti H
Published: August 2010

Purpose: Present repair kinetic models are not specifically designed to be applicable to high‐LET radiation beams. They thus inherently assume that full repair always takes place between fractions, with the risk that they may underestimate the increased biological effectiveness of high‐LET treatments. A second‐order repair kinetics model is developed to predict damage repair rates following low‐ or high‐LET irradiations and to assess the amount of unrepairable damage produced by such radiations. Materials and Methods: The model is a further development of an earlier version designed to test if low‐LET radiation repair processes could be quantified in terms of second‐order kinetics. The newer version allows calculation of both, the repair rate of the proportion of cells that repair according to second‐order kinetics and the proportion of cells that do not repair. The original and the present versions, as well as other models presently used in clinical Radiotherapy, are compared in terms of their goodness‐of‐fit to a number of data sets obtained from different ion beams. Results: The analysis demonstrates that the present model provides a better fit to the data in all cases studied. The proportions of unrepairable damage created by radiations of different LET predicted by the new model correspond well with previous studies on the increased effectiveness of high‐LET radiations in inducing reproductive cell death. Conclusion: The results show that the original model may underestimate the proportion of unrepaired damage at any given time after its creation and that it fails to predict very slow or unrepairable damage components which may result from high‐LET irradiation. The low number of parameters present in the new model and its better fit to the data compared to other repair models currently used in clinical Radiotherapy, make it a powerful tool to estimate the impact of incomplete repair effects in fractionated high‐LET radiotherapy.
SU‐DD‐A2‐05: Linear Energy Transfer of Proton Clusters
Authors: Fourkal E , Veltchev I , Ma C
Published: August 2010

Purpose: In conventional particle accelerators protons are produced in long pulses. Therefore, the radiobiology of conventionally accelerated protons is primarily governed by the interaction of a single proton with the cell. In the laser‐plasma interaction scheme, the accelerated protons come as a single bunch of particles with interparticle distances that can be orders of magnitude shorter compared to those in conventional particle accelerators. As laser‐accelerated protons traverse the medium, they not only interact with it but also with each other, which under certain conditions may lead to a coherent interference effect manifested by the increase in their linear stopping power that may eventually lead to higher relative biological effectiveness (RBE) of the cluster. Understanding the exact conditions under which such an effect becomes significant is the main goal of this work. Method and Materials: The dynamic linear response theory of the medium is used to calculate the stopping power of the proton cluster. The proximity function is introduced that defines the enhancement effect in the energy loss of the cluster. The relation between the RBE and the LET is used to predict the cluster's RBE. Results: When the average distance between protons in a cluster is smaller than certain threshold, the enhanced LET of the cluster is found. The increased stopping power is due to the interference effect between the induced fields. It is conjectured that the accelerated proton cluster will have larger RBE values compared to those accelerated through conventional methods. Conclusions: The potential impact of this project lies in the development of a deeper understanding of radiobiology of particle clusters, a question that has not been addressed before. If the main conjecture of this project is experimentally confirmed, this may spawn the development of new proton sources for medical accelerators with increased RBE and thus higher tumor controls.
SU‐DD‐A3‐01: Comparison of Respiration‐Correlated and Uncorrelated Cone‐Beam CT for Correcting Target‐Positioning Errors in Radiotherapy of Thoracic and Abdominal Cancer
Authors: Santoro J , Yorke E , Rosenzweig K , Goodman K , McNamara J , Pham H , Mageras G
Published: August 2010

Purpose: This study compares respiration‐correlated kV cone beam CT (RC‐kVCBCT) image guidance to standard (uncorrelated) kVCBCT for target localization in radiation treatment of thoracic and abdominal tumors. Method and Materials: In an IRB‐approved study, 9 stage II–IV non‐small cell lung cancer (NSCLC) patients and 1 stage III stomach tumor patient with fiducials received a respiration‐correlated planning CT (RCCT) at simulation and five RC‐CBCTs during the first week of treatment. The GTV volumes ranged from 2.8 cm3 – 286 cm3. Kilovoltage RC‐CBCT scans are acquired (Varian Trilogy) while recording respiration and with reduced gantry speed (0.2 rpm), yielding 3D images at six respiratory phases. The tumor in each phase of the RC‐CBCT is registered to the end‐expiration (EE) phase image to obtain the respiration‐averaged tumor displacement relative to its EE position. This process is repeated in the RCCT image set. The RCCT and RC‐CBCT images at EE are registered to obtain the tumor displacement at the EE position. A vector sum of the three displacements yields the correction to the respiration‐averaged tumor position. For comparison, the correction is also computed by matching an uncorrelated CBCT reconstructed with all projections and representing a respiration‐averaged image, to the average intensity projection image computed from the RCCT. Results: The mean difference between the two correction methods in 10 patients was 1.4mm left‐right (L/R), 1.6mm anterior‐posterior (A/P), and 1.7mm superior‐inferior (S/I). The maximum difference was 5.0mm (L/R), 6.0mm (A/P), 7.0mm (S/I). The GTV range‐of‐motion at simulation ranged from 2–14mm. Conclusion: Our preliminary results suggest that for many thoracic and abdominal tumors, position corrections using uncorrelated, respiration‐averaged 3D imaging are consistent with those from respiration‐correlated imaging; however, respiration‐correlated imaging may be indicated for cases of large tumor motion. Research supported by Varian and by NIH grant T32 CA61801.
SU‐EE‐A2‐03: Evaluating AAPM TG‐43 In‐Water HDR 192Ir Brachytherapy Reference Dosimetry: A Comparison Study
Authors: Sarfehnia A , Kawrakow I , Seuntjens J
Published: August 2010

Purpose: To investigate the accuracy of AAPM TG‐43 in HDR 192Ir brachytherapy in water reference dosimetry by comparing the protocol against ionometric and Gafchromic film calibration procedures introduced as well as a water calorimetry‐based primary standard. Methods and Materials: Dose to water Dwater was measured directly in water using an Exradin A1SL farmer‐type chamber and EBT‐1 Gafchromic films. The chamber had a NIST‐traceable 60Co calibration factor while the films were calibrated under 6 MV photons. Accurate Monte Carlo modeling and simulation of the chamber (egs++) and EBT Gafchromic films (DOSRZnrc) were performed to convert calibration factors of the two detectors from their respective conditions into 192Ir brachytherapy. The Dwater results were compared to measurements made using a Standard Imaging well‐type chamber following AAPM TG‐43 protocol and water calorimetry primary standard measurements. Results: By calculating the ratio of dose‐to‐water to dose‐to‐gas for the A1SL chamber under reference 60Co conditions and 192Ir setup conditions, the ionization measurements in 192Ir were converted to dose to water. The Monte Carlo calculations in film dosimetry revealed that if the intrinsic energy dependence of the film is negligible, a sensitometric curve obtained with 6 MV can be used in 192Ir measurements, with the energy dependence correction being 0.9971 (1σ=0.1%). The overall one‐sigma uncertainty on ionization chamber, Gafchromic film, and water calorimetry dose rate measurement amounts to 1.44%, 1.78%, and 1.96%, respectively. The indirect Dwater measurements from TG‐43 agreed to within 1.4% with ionometric measurements, 0.3% with Gafchromic measurements, and 0.6% with Calorimetric absolute dose measurements. Conclusions: Accurate ionometric and Gafchromic film based calibration protocols are introduced. For 192Ir brachytherapy, the 1‐sigma uncertainty of TG‐43 reference dosimetry was found to be better than 1.4%.
SU‐EE‐A3‐04: A Superfluence Approach for EPID‐Guided 3D Dose Verification
Authors: Aristophanous M , Rottmann J , Court L , Berbeco R
Published: August 2010

Purpose: Several methods exist for tracking tumors on EPID images acquired during treatment. Utilizing the tumor tracks, the planned fluence can be averaged to create a “superfluence” that reflects the delivered dose. We investigated the feasibility of 3D dose verification using the superfluence. Method and Materials: The CIRS dynamic phantom was used with 15 MOSFETs inserted in a soft resin tumor model created from a real patient tumor segmented on a CT scan. A real patient breathing pattern with 1.5cm amplitude was set and a 4D CT was acquired. The PTV was obtained by expanding the ITV uniformly by 5mm as typically done in lung SBRT treatments. A 7‐field plan was created with the same coverage as is clinically required. The phantom was irradiated with the tumor static and moving with several amplitudes and set up errors. EPID images were recorded throughout these deliveries and the tumor was tracked post‐treatment with in‐house developed software. The planned fluence was blurred according to the motion tracks to obtain a superfluence from which the delivered dose was calculated. The estimated delivered dose was compared to the dose directly measured by the MOSFETs. Results: The calculation of delivered dose with the superfluence method was in good agreement with the MOSFET measurements. The difference varied on average from 0.8% to 8.3% depending on the proximity of a dose gradient.Conclusions: A novel method is presented for 3D dose verification based on the superfluence concept. The only requirements are the acquisition of EPID images during treatment and a tracking algorithm to obtain the tumor motion. The excellent agreement between the measured and calculated dose indicates the validity of the method.
SU‐GG‐J‐06: Optical and X‐Ray Image Guided Stereotactic Body Irradiator Dedicated to Small Animals
Authors: Song K , Pidikiti R , Stojadinovic S , Speiser M , Seliounine S , Saha D , Solberg T
Published: August 2010

Purpose: To develop a dual modality, optical and x‐ray, image guided stereotactic irradiator, and to improve tumor visualization and the accuracy of target localization in small animal irradiation. Method and Materials: A bioluminescence (BL) optical imaging system has been integrated into an existing x‐ray image‐guided stereotactic irradiator developed previously by our group. The new system provides precise target localization and accurate radiation delivery in three dimensions. All localization procedures are computer‐controlled. An air‐cooled CCD camera with sufficiently reduced dark current for better signal‐to‐noise ratio is employed for bioluminescence imaging. The CCD camera is positioned off‐axis, in the same transverse plane as the x‐ray radiation axis. To acquire BL images, the animal is rotated through a 30 degree angle towards the camera, and then back to the original (treatment) position for the x‐ray imaging. The BL images are registered to the x‐ray images for image guidance. Results: The dual modality image guided irradiator was evaluated using an orthotopic lung tumor in a rat. The anterior and lateral BL images clearly showed the tumor with high contrast, while the same tumor was visible only in the anterior view in the x‐ray images. This indicated that the x‐ray image guidance alone is not sufficient to provide the precise localization. On the other hand, the registered BL and x‐ray images overcome this limitation by combining information of tumor position in the BL image with the anatomy in the x‐ray image. Conclusion: The accuracy of tumor localization in small animal SBRT is dramatically improved by integrating optical imaging with x‐ray imaging. The developed system also enhances the sparing of dose limiting normal tissues and organs‐at‐risk (OARs) and has facilitated accurate assessment of experiments in small animal SBRT investigations.
SU‐GG‐J‐15: Evaluation of Dose Uncertainties Introduced by Dose Mapping Process Implemented in a Commercial 4D Treatment Planning System
Authors: Yan C , Saleh‐Sayah N , Salguero F , Siebers J
Published: August 2010

Purpose: To evaluate dose uncertainties introduced by dose mapping process implemented in a commercial 4D treatment planning system by evaluating integral dose conservation in common volumes between unmapped and mapped images. Method and Materials: CT images corresponding with the peak‐of‐exhale (TO) and peak‐of‐inhale (T5) from a lung patient are used. Physician drawn regions of interest (ROIs) of the rightlung, GTV, spinal cord and heart on TO are propagated via the surface landmark‐based deformable image registration algorithm built into the commercial software to generate deformation vector fields (DVFs). An IMRT treatment plan on T5 and dose distribution on T5 is calculated, and the DVFT0→T5 is used to map the dose from T5 to TO. Cubic ROIs with volumes of 1, 2, 4 and 8 cm3 are selected on T0 and mapped to T5 using bitmaps to evaluate dose uncertainty as follows: let M0, E0, and M5, E5 be the mass and integral dose within the T0 and T5 ROIs. Dose uncertainty, defined as ΔD = ∂D/∂E × ΔE + ∂D/∂M × ΔM = (E5 − E0)/M5 − (M5 − M0)/M02 × E0, is evaluated for each ROI. The mean dose uncertainty, defined as ΔD= E0/M0 − E5/M5, is also evaluated. The mean dose, DVH and Dose‐Mass‐Histograms (DMHs) for critical organs are also compared. Results: The average dose uncertainties detected are: 5.56%, 5.03%, 4.18% and 3.72% for the 1, 2, 4, and 8 cm3 volumes respectively. The average mean dose uncertainty detected are 3.7%, 3.6%, 3.1% and 3.1%. The largest dose uncertainty points are close to the boundary of tumor. Conclusion: Dose uncertainties introduced by the dose mapping process implemented in a commercial 4D treatment planning system are evaluated. Though the average dose uncertainty is small, some large dose uncertainties are observed. More test cases are needed. Work supported by NIH P01CA116602.
SU‐GG‐J‐30: A Novel Scatter Reduction and Correction Method to Improve Cone‐Beam CT (CBCT) Image Quality
Authors: Ren L , Kim J , Liu Q , Movsas B , Chetty I , Jin J
Published: August 2010

Purpose: To develop a novel scatter reduction and correction method to improve the CBCT image quality for IGRT applications. Method and Materials: A one‐dimensional grid composed of lead with equal interspacing was positioned between the x‐ray source and the imaging object during CBCT acquisition. The grid provides direct scatter reduction by blocking half of the beams. Partial image data were obtained from the grid inter‐space (unblocked) region while scatter was measured from the blocked region beneath the grid in the projection images. Scatter was corrected by subtracting the measured scatter from the original projection image. Information in the penumbra region of each grid septa was derived. Three modes were developed to reconstruct full CBCT images from partially blocked projections. In single rotation axial mode, interpolation was used to fill in the missing data in the half‐fan projections. In dual rotation mode, two‐rotation half‐fan scans were acquired with the grid offset by half a grid cycle, and complimentary projections were merged to form complete projections for reconstruction. In single rotation helical mode, one‐rotation full‐fan scan was acquired with the grid offset by half a grid cycle at the scan center. Both CatPhan and anthropomorphic pelvis phantoms were used to evaluate the method. Results: In the CatPhan study, CNR was improved using our approach from 4.3 to 6.4 in comparison to conventional CBCT, and CT‐number linearity correlation coefficient increased from 0.88 to 0.998. Scatter induced streak artifacts were significantly reduced. In the pelvis phantom study, complete sets of CBCT images were reconstructed and scatter related artifacts were significantly reduced in all three modes. Conclusion: Our method enhances CNR and provides much more accurate measurement of scatter with reduced or equivalent dose to conventional CBCT. Scatter‐related artifacts are substantially reduced, and the CBCT images generated are of appropriate quality for adaptive radiation therapy.
SU‐GG‐J‐31: Simultaneous Estimation of Beam Geometry and Radiation/Imaging Isocenter Coincidence in Cone‐Beam CT‐Guided Radiation Therapy
Authors: Ford J , Zheng D , Saleh H , Lu J , Williamson J
Published: August 2010

Purpose: To simultaneously characterize the geometric pose of an on‐board CBCT imaging system and measure the relative positions of the imaging and treatment machine radiation isocenters. Method and Materials: The method is based on an existing technique (Cho, et al, Med Phys 32(4), 968), which utilizes CBCT projections of a fiducial phantom to calculate the source and detector positions and orientations as a function of gantry angle. The algorithm was modified to localize the phantom pose relative to the kV source trajectory, and to transform beam geometry parameters from the phantom to imaging isocenter coordinate system. The method was applied to both CBCT and MV EPID projections acquired during the same imaging session without moving the phantom. The calculated positions of the phantom relative to the CBCT and EPID projection isocenters provide the relative displacement of the imaging and treatment isocenters. Two additional CBCT imaging experiments were then performed with the phantom displaced known distances. Results: Calculated CBCT geometric parameters were consistent over the three experiments, even with the phantom displaced from the machine isocenter by 10mm or misaligned with the gantry rotation axis by 1°. The CBCT beam parameters were close to nominal with small variations with gantry angle, with the exception of a 1 mm detector offset parallel to the gantry axis. Displacement of the CBCT imaging isocenter from the treatment isocenter was found to be (0.07, 1.24, 0.05 mm) in the (L‐R, A‐P, S‐I) direction. Conclusion: The method's output can assist in mitigation of geometric distortion‐related CBCT image artifacts and simultaneously provides the imaging‐to‐treatment isocenter offset. Supported by NCI Grant P01 CA 116602
SU‐GG‐J‐33: Localizing a Moving Tumor Using MV‐CBCT
Authors: Gayou O , Colonias A
Published: August 2010

Purpose: To evaluate mega‐voltage cone‐beam computed tomography (MV‐CBCT) imaging of moving tumors. Method and Materials: Five patients treated for early stage non‐small cell lung cancer using stereotactic body radiation therapy (SBRT) were analyzed. Simulation images were obtained with a Siemens Sensation Open 4D‐CT scanner. The Internal Target Volume (ITV) comprised of the tumor in each phase and on the free‐breathing CT was created. Daily localization was performed with MV‐CBCT on a Siemens Artiste linear accelerator with the in‐line kView system, using a 4.2 MeV electron beam incident on a carbon target without flattening filter to increase the yield of low energy photons. The tumor was contoured on each daily CB image. The size of the ITV contours on the planning CT and MV‐CBCT was compared in the anterior‐posterior (AP), left‐right (LR) and superior‐inferior (SI) directions. Results: In the majority of cases the standard deviation of the MV‐CBCT contour size from day to day was less than 2 mm. The average difference between the planning CT and MV‐CBCT contours varies widely from patient to patient. The largest difference (10.1 mm) was seen in the SI direction for a patient for whom breathing motion was large (18 mm), and the contrast between the tumor and its surroundings in the expected tumor position during the full‐inhale phase was reduced. The second largest difference (7.2 mm) was seen in the SI direction in a patient for whom the proximity of the tumor to a large blood vessel also reduced the contrast. Conclusion: There is a possibility of inaccurate registration between the planning CT and MV‐CBCT and less effective localization when the contrast is adversely affected because of large tumor motion or proximity to other structures. This should be taken into account in the Planning Target Volume margin. Research partially supported by Siemens Medical Solutions.
SU‐GG‐J‐35: A Quantitative Assessment of the Improvement in Lung Treatment Accuracy with IGRT in TomoTherapy
Authors: Bichay T , Chen C , Klynstra N , Meadows J
Published: August 2010

Purpose: The use of extremely high dose gradients in IMRT has made patient positioning accuracy even more critical than in previous modalities. Our purpose is to quantify the improvement in setup accuracy with the use of IGRT for patients undergoing radiation therapy of the lung with TomoTherapy. We also investigate whether the first few imaging sessions could serve as a predictor of subsequent daily shifts for a given patient. Method and Materials: Megavoltage computed tomography (MVCT) was carried out at each treatment fraction immediately prior to treatment. The MVCT was fused to the planning KVCT and the resultant X,Y,Z offsets determined by a combination of automatic registration as well as operator adjustments. A total of 2,496 X,Y,Z measurements from 34 patients were collected for this study. Results: All three axes contributed significantly to the overall mean vector shift of 10.5 mm. The mean vertical shift (Z direction) is 6.5 mm. The mean shift in the longitudinal direction (Y) is 5.2 mm, while the mean in the lateral direction (X) is 3.7 mm. The variation in shifts between different patients was significant and varied by at least a factor of five. We also found that variations in daily position for an individual patient could vary by at least a factor of five. Conclusion: This study demonstrates quantitatively, that the potential improvement in radiotherapy geometric treatment accuracy is approximately 10.5 mm, with the use of IGRT in lung TomoTherapy. Given the variability in daily patient positioning, averaging initial patient shifts is not an accurate predictor of subsequent patient setup position.
SU‐GG‐J‐36: Analysis of Artifacts in Four‐Dimensional CT Images of Phantoms with Regular Motions
Authors: Sheen H , Han Y , Shin E
Published: August 2010

Purpose: The aims of this study were to clarify the factors causes imaging artifacts and investigate the impact of partial volume and truncation artifacts on volume determination. Method and Materials: Moving cylindrical phantoms with 2cm of diameter with different heights, 0.3cm, 0.5cm, 1cm, 2cm, 3 cm, and 10cm were scanned (scan range 2cm/6cm0 by GE (General Electric Healthcare) LightSpeed. GE Advantage. 4D software was used to create 4D‐CT data sets. The artifacts were then visually and quantitatively analyzed. Scan. The target volume was determined by manual contouring and automatic volume detection using a cutoff value of 250 HU (Hounsfield Unit). The conformity index of the target volume was defined as the ratio of the manually contoured volume to the volume defined by HU cutoff. The ratio of volume from static CT to real volume was calculated in order to investigate the partial volume effect and truncation artifacts. The volumes measured in 10 phases of 4D CT images were also compared with true volume. Results: The ratio of static cylinder volume in CT images scanned 2cm length to the real volume was maximally twice by partial volume effect. The correlation between the velocity and target volume was not consistent potentially due to complicate interplay of different artifacts;,partial volume effect, truncation artifact and miss or different matching between adjacent beds . Conclusions: The static CT data volume can be quite different from true volume even in static CT images. If a lesion size is not enough to overcome the impact of the partial effects, significantly larger volume will be presented on static and 4DCT images. Any strong correlation between the velocity and the volume was not found.. The 4DCT images still presents partial volume and truncation artifact that requires the further improvement of imaging technology.
SU‐GG‐J‐44: Estimation of Lateral Scatter Kernels in EPID and Water Equivalent Phantom for Dose Verification in Stereotactic Lung Radiotherapy
Authors: Mizoguchi A , Arimura H , Yoshidome S , Tachibana M , Shioyama Y , Anai S , Nakamura K , Honda H , Higashida Y , Toyofuku F , Ohki M , Hirata H
Published: August 2010

Purpose: Lateral scatter kernels (LSKs) of an electronic portal imaging device (EPID) and a water equivalent phantom are essential data for estimating the three‐dimensional dose distributions in lung cancer patients who receive stereotactic body radiotherapy. The LSKs are used for converting portal images to portal dose images. The purpose of this study was to investigate a method of estimating LSKs of the EPID and water equivalent phantom, and then compare the LSKs between experimental measurements and the Monte Carlo (MC) method. Method and Materials: The experimental LSKs were derived from the differentiation of the signal (mean pixel value or absorbed dose) as a function of equivalent circular radius of irradiation area. Mean pixel values in a region of interest of the EPID and absorbed doses in the water equivalent phantom were measured for estimating the LSKs of the EPID and water equivalent phantom, respectively, by changing the irradiation area of 3×3 to 20×20 cm2. For evaluation of the experimental method, the theoretical LSKs were obtained based on the Monte Carlo method by simulating the same geometry of the experimental set‐up including the EPID and water equivalent phantom. Two x‐ray energies of 6 and 10 MV were employed respectively, at a medical linear accelerator in conjunction with an EPID. Results: The experimental method overestimated the LSKs of the EPID and water equivalent phantom compared with those of the Monte Carlo simulation method. The full width half maximum values at 6 and 10 MV of the theoretical LSKs were 0.166 and 0.193 cm for the EPID, respectively, and 0.177 and 0.211 cm for the water equivalent phantom, respectively. Conclusion: We should continue to investigate the experimental and theoretical methods for estimation of LSKs of the EPID and water equivalent phantom for dose verification in stereotactic lung radiotherapy.
SU‐GG‐J‐45: Application of Virtual Patient Model in 4D IMRT Monte Carlo Treatment Planning
Authors: He W , Guo B , Xu X , Shi C
Published: August 2010

Purpose: 4D IMRT planning using 4D CT images has uncertainties such as image artifacts, image sorting uncertainty and deformable image registration uncertainty. On the other hand, using virtual reality to create patient‐specific virtual model can represent the patient more accurately. Therefore, in this study, we are aiming to investigate the feasibility of 4D IMRT planning using virtual patient model. Method and Materials: The input contours for virtual model was from Pinnacle treatment planning system. The polygon of a structure formed from sampled control points, were used to reconstruct the NURBS surface of this structure. A 4D virtual patient was initially a sequence of 3D NURBS models at different phases. To be applied in real‐time breathing management, a few methods were used to adjust the model to account for the variation of breathing and to give model the ability to predict motion. Kaiman filter was used to predict the breathing curve. Two Monte Carlo codes, MCSIM and EGS4‐VLSI were used to simulate the treatment plan using the opening density matrix exported from Pinnacle optimization results. MCsim used patient's CT in dose calculation while EGS4‐VLSI used a phantom converted from patient's model. DVHS were compared for end‐exhale phase among the results from Pinnacle and the two Monte Carlo codes. Results: Monte Carlo codes benchmark showed good agreement for clinical measured data for 10×10 cm2 PDD and profiles. DVHs showed differences mainly due to the inhomogeneity effects for dose calculation. Conclusion: A virtual model based 4D IMRT method was proposed and preliminary results show the feasibility of this methodology. Varity exits among different calculation method, real clinical benefit of model based planning needs further investigation.

Conflict of interest: Research supported by grant R0I LM009362.
SU‐GG‐J‐48: An Online Replanning Method for Independently Moving Structures
Authors: Ahunbay E , Li X
Published: August 2010

Purpose: The current IGRT repositioning, based on rigid‐bady registration, fails to align organs with independent dislocation and deformation such as those in the abdomen. This work aims to extend a previously developed online replanning method to handle independent multiple organ movement. Methods and Materials: Daily CTs acquired during pancreatic cancer treatments using a respiratory gated CT‐on‐Rails (CTVision, Siemens) were used to test the method. Contours of the target and organs at risk (OAR) were generated on the daily CTs based on deformable registration with manual editing if necessary. A replanning method composed of a segment aperture morphing (SAM) and segment weight optimization (SWO) were applied. The SAM was applied separately on each structure (target and OARs), and the final aperture shape was formed by prioritizing individual aperture shapes. Each structure imposes specific penalties on leaf position deviations from their SAM values which mainly depends on the importance of the particular structure., Penalties for leaf opening vs. closing are different for target vs OAR. Conflict apertures are also detected automatically by SWO, which employs segment splitting along with an objective function scheme that updates the power of individual goals to prevent multiple trial and error runs. Plans for the current patient repositioning were generated for comparison. Results: The mean doses of stomach and duodenum for repositioning plans are increased by 66% and 10% from their planning values, which are reduced to 5% and 1% for the adaptive plans based on modified by SAM without compromising the target coverage. SWO further improved the plan quality resulting in the final plans that are comparable to the original plan. The SAM and SWO algorithms for multiple structures can be executed within 10 min. Conclusion: The modified SAM+SWO algorithms that can handle multiple independent organ motion and deformation can be implemented for online adaptive replanning.
SU‐GG‐J‐54: Evaluation of Residual Errors in Online Guidance of Primary and Nodal Targets in Lung Cancer
Authors: Robertson S , Weiss E , Badawi A , Brown A , Orton M , Hugo G
Published: August 2010

Purpose: To evaluate the accuracy of online guidance for primary and nodal lung cancer targets. Method and Materials: Weekly CT scans under active breathing control were acquired during treatment for 18 patients enrolled as research subjects. Separate primary gross tumor volume (GTVP) and involved lymph node GTVs (GTVLN) were delineated by a physician on all images. Each weekly online image was aligned to the reference (planning) image automatically using a rigid image‐based registration. Four rectangular regions of interest were evaluated for the ability to match the target structures: the whole image; the GTVP + 1 cm; the GTVLN + 1 cm; and both the GTVP and GTVLN + 1 cm. The GTVs on the online images were translated according to this new registration, and the centroid displacements of the delineated GTVs were calculated to measure the residual error after image‐based alignment. Results: The mean absolute error was 5.1 ± 4.7 mm for the GTVP and 6.4 ± 6.9 mm for the GTVLN. The combined mean absolute error was 5.7 ± 5.9 mm for both structures. Rigid registration of GTVP + 1 cm yielded the smallest residual error (RE) for the primary tumor of 3.3 ± 3.9 mm, with a RE of 4.8 ± 4.8 mm for the lymph nodes. Registration of GTVLN + 1 cm provided the smallest RE for the lymph nodes of 4.1 ± 5.8 mm, though the primary tumor RE was 5.0 ± 4.9. The smallest combined RE for both structures was 4.0 ± 4.5, which was obtained using rigid registration of the GTVP + 1 cm. Conclusion: Shape, volume, and relative position change of multiple targets introduces error into soft‐tissue localization in locally‐advanced lung cancer, although tumor regression was the dominant source of error. Deformable registration methods may be required to improve localization accuracy.
SU‐GG‐J‐55: Simultaneous Estimation of Lung Tumor Image and Intrafractional Motion without Implanted Markers Using KV‐X‐Ray Fluoroscopy for Image‐Guided Radiotherapy
Authors: Endo H , Homma N , Takai Y , Yoshizawa M
Published: August 2010

Purpose: The aim of this research is to develop a novel image processing method for accurate estimation of intrafractional lung tumor respiratory motion using kV‐X‐ray fluoroscopy without implanted fiducial makers that have been used and needed for image guided radiotherapy, but their implantation run the risk of pulmonary emphysema and pneumothorax. Method and Materials: We propose a technique for extracting the lung tumor image from the kV‐X‐ray fluoroscopic observation. An essential core of the method is in a simultaneous estimation of tumor image and motion by using sequences of fluoroscopic images that can provide pieces of information needed for the estimation. The tumor images extracted can then easily be used for motion estimation of the tumor by using conventional motion estimation techniques such as block matching (BM) and template matching (TM). Results: We have evaluated the new extraction method with TM using three patient kV‐X‐ray fluoroscopy data. An example of the tumor image extraction is shown in the supporting document. The average error and the standard deviation of the motion estimation were, respectively, 0.72 [mm] and 0.37 [mm] by the proposed method. This is clearly smaller than the average of 1.02 [mm] with the standard deviation 0.23[mm] by the conventional TM. Note that the comparison between the proposed method with TM and the conventional TM demonstrates the effectiveness of the new extraction technique. In addition, this result implies that the method can achieve within 1 [mm] of motion estimation accuracy without implanted markers and it's clinically acceptable. Conclusion: We have developed intrafractional motion estimation method of lung tumor without implanted markers. Any motion estimation technique can be incorporated into the proposed extraction method for accuracy improvement. The proposed method can achieve clinically sufficient accuracy estimation without implanted makers and thus can fundamentally reduce any patient's risk caused by the implantation.
SU‐GG‐J‐56: Can Four Dimensional Cone Beam Computed Tomography (4DCBCT) Improve the Patient Setup for Stereotactic Body Radiation Therapy
Authors: Huang L , Papiez L , Papiez E , Solberg T , Mao W , Ding C , Timmerman R
Published: August 2010

Purpose: To assess the precision of 4DCBCT in patient setup for stereotactic body radiation therapy of lung cancer. Methods and Materials: Eight cases of breathing motion patterns are imposed on phantom imitating the tumor motion in the lung. These simulated phantom motions are scanned by 4DCT. PTV volumes are defined from 4DCT images. At Elekta SynergyS, 3DCBCT images are acquired for phantom reproducing same motions at 4DCT. 3DCBCT data are transferred to XVI 1.51b and reconstructed into 4DCBCT. 4DCBCT images are imported into Pinnacle 8.1y. AVG and MIP images from 4DCBCT data are comparing with 4DCT. Matching are performed between AVG and MIP from 4DCBCT and 4DCT to set standards for accurate 4DCBCT derived irregularly target placement at treatment unit for case of irregular breathing motions for SBRT therapy of the lung. PTV location in laboratory frame of reference derived from known geometry of the phantom and known motion of the target is compared to PTV localization at same reference as derived from 4DCT and 4DCBCT. Results: Images from 4DCBCT for patient setup shows noticeable difference with setup based on standard 3DCBCT. We found up to 5mm difference between 3DCBCT based setup and 4DCBCT setup in case when irregular breathing pattern with over 20 mm range. When comparing static marker location to the tumor location defined by phantom dimensions and phantom motion with respect to PTV location derived from 4DCBCT, we found the center of PTV dislocation relative to its true center up to 4mm. Dosimetric impact of this error will be reported. Conclusions: 4DCBCT is not likely to improve the accuracy of patient positioning relative to 3DCBCT unless considerably slower gantry rotation is used to increase sampling of images needed for 4D binning.