Set Of Contours Research Articles

Helical Tomotherapy Delivery of an IMRT Boost in Lieu of Interstitial Brachytherapy in the Setting of Gynecologic Malignancy: Feasibility and Dosimetric Comparison

Interstitial brachytherapy is an important means by which to improve local control in gynecologic malignancy when intracavitary brachytherapy is untenable. Patients unable to receive brachytherapy have traditionally received conventional external beam radiation alone with modest results. We investigated the ability of Tomotherapy (Tomotherapy Inc., Madison, WI) to replace interstitial brachytherapy. Six patients were selected. The planning CT of each patient was contoured with the planning target volume (PTV), bladder, rectum, femoral heads, and bowel. Identical contour sets were exported to Tomotherapy and Nucletron PLATO (Nucletron B.V., Veenendaal, The Netherlands). With Tomotherapy, the PTV was prescribed 31 Gy in 5 fractions to 90% of the volume. With PLATO, 600 cGy × 5 fractions was prescribed to the surface of the PTV. Dose delivered was normalized to 2 Gy fractions (EQD2) and added to a hypothetical homogenous 45-Gy pelvic dose. Tomotherapy achieved a D90 of 87 Gy EQD2 versus 86 Gy with brachytherapy. PTV dose was more homogeneous with tomotherapy. The dose to the most at-risk 2 mL of bladder and rectum with Tomotherapy was of 78 and 71 Gy EQD2 versus 81 and 75 Gy with brachytherapy. Tomotherapy delivered more dose to the femoral heads (mean 1.23 Gy per fraction) and bowel. Tomotherapy was capable of replicating the peripheral dose achieved with brachytherapy, without the PTV hotspots inherent to interstitial brachytherapy. Similar maximum doses to bowel and bladder were achieved with both methods. Excessive small bowel and femoral head toxicity may result if previous pelvic irradiation is not planned accordingly. Significant challenges related to interfraction and intrafraction motion must be overcome if treatment of this nature is to be contemplated.

Prospective Randomized Double-Blind Pilot Study of Site-Specific Consensus Atlas Implementation for Rectal Cancer Target Volume Delineation in the Cooperative Group Setting

Variations in target volume delineation represent a significant hurdle in clinical trials involving conformal radiotherapy. We sought to determine the effect of a consensus guideline-based visual atlas on contouring the target volumes. A representative case was contoured (Scan 1) by 14 physician observers and a reference expert with and without target volume delineation instructions derived from a proposed rectal cancer clinical trial involving conformal radiotherapy. The gross tumor volume (GTV), and two clinical target volumes (CTVA, including the internal iliac, presacral, and perirectal nodes, and CTVB, which included the external iliac nodes) were contoured. The observers were randomly assigned to receipt (Group A) or nonreceipt (Group B) of a consensus guideline and atlas for anorectal cancers and then instructed to recontour the same case/images (Scan 2). Observer variation was analyzed volumetrically using the conformation number (CN, where CN = 1 equals total agreement). Of 14 evaluable contour sets (1 expert and 7 Group A and 6 Group B observers), greater agreement was found for the GTV (mean CN, 0.75) than for the CTVs (mean CN, 0.46-0.65). Atlas exposure for Group A led to significantly increased interobserver agreement for CTVA (mean initial CN, 0.68, after atlas use, 0.76; p = .03) and increased agreement with the expert reference (initial mean CN, 0.58; after atlas use, 0.69; p = .02). For the GTV and CTVB, neither the interobserver nor the expert agreement was altered after atlas exposure. Consensus guideline atlas implementation resulted in a detectable difference in interobserver agreement and a greater approximation of expert volumes for the CTVA but not for the GTV or CTVB in the specified case. Visual atlas inclusion should be considered as a feature in future clinical trials incorporating conformal RT.

Globally inconsistent figure/ground relations induced by negative parts

In conventional accounts of figure/ground organization, and in traditional Gestalt theory, figure/ground assignment is assumed to be globally consistent along the entire contour of a figure. If figure and ground reverse at one point on an object boundary, the entire boundary reverses, as in classical bistable figures such as the Rubin face/vase. Here we investigate a situation where local configural cues to figure/ground conflict with global cues: “negative parts.” We constructed displays in which a circular shape included a “bay” or cut-out region. We tested figure/ground interpretation locally by using a moving probe (a region of the contour set in “trembling” motion). We asked subjects which color (the interior or exterior color) seemed to be moving; their response reflects figure/ground assignment, as the motion is perceived to be perceptually owned by the figural side of the boundary. We manipulated the shape and size of the bay, and the position of the probe (inside the bay or elsewhere along the contour). Subjects were significantly more likely to perceive the exterior as figural (that is, to invert the normal figure/ground assignment) when the probe was inside the bay than when it was outside, suggesting that the bay was indeed perceived as a “negative part.” Moreover the shape (convexity) of the bay influenced figure/ground assignment when the probe was inside the bay, but not when it was outside; that is, the figure/ground inversion was local to the negative part itself, resulting in a globally inconsistent figure/ground interpretation. Two followup studies suggest that this phenomenon involved a local inversion of perceived depth, not mere contour ownership. The results suggest that figure/ground interpretation is a dynamic and complex process in which local and global cues combine and compete to produce an ultimate percept that may not be globally consistent.

Evaluation of Automatic Atlas-Based Lymph Node Segmentation for Head-and-Neck Cancer

To evaluate if automatic atlas-based lymph node segmentation (LNS) improves efficiency and decreases inter-observer variability while maintaining accuracy. Five physicians with head-and-neck IMRT experience used computed tomography (CT) data from 5 patients to create bilateral neck clinical target volumes covering specified nodal levels. A second contour set was automatically generated using a commercially available atlas. Physicians modified the automatic contours to make them acceptable for treatment planning. To assess contour variability, the Simultaneous Truth and Performance Level Estimation (STAPLE) algorithm was used to take collections of contours and calculate a probabilistic estimate of the "true" segmentation. Differences between the manual, automatic, and automatic-modified (AM) contours were analyzed using multiple metrics. Compared with the "true" segmentation created from manual contours, the automatic contours had a high degree of accuracy, with sensitivity, Dice similarity coefficient, and mean/max surface disagreement values comparable to the average manual contour (86%, 76%, 3.3/17.4 mm automatic vs. 73%, 79%, 2.8/17 mm manual). The AM group was more consistent than the manual group for multiple metrics, most notably reducing the range of contour volume (106-430 mL manual vs. 176-347 mL AM) and percent false positivity (1-37% manual vs. 1-7% AM). Average contouring time savings with the automatic segmentation was 11.5 min per patient, a 35% reduction. Using the STAPLE algorithm to generate "true" contours from multiple physician contours, we demonstrated that, in comparison with manual segmentation, atlas-based automatic LNS for head-and-neck cancer is accurate, efficient, and reduces interobserver variability.

The tuning of vision to natural contours: Straighter is better

Contour smoothness is a fundamental constraint in the visual interpretation of images. We aimed to quantify the human visual system's intrinsic model for contour curvature and to test whether this model corresponds to that determined from measurements of natural images. We did this by measuring how well observers could estimate contours in visual noise as a function of contour curvature. Contours were generated by appending line segments that could turn 45 deg left, remain straight, or turn 45 deg right. Contour models were generated by assigning various turning probabilities. Thus, for example, one model might generate contours that tended to zigzag, and another model contours that tended to be straight. Images were generated by assigning intensity values, y, to pixels according to probability distributions p(y|on) or p(y|off) depending on whether the pixel was on or off a contour. Observers were asked to estimate the pixels belonging to the contour by tracing a path through a sample image. In a given session, the contour probability model was fixed and known to the subject. To assess subjects' use of the prior information we measured efficiency by comparing human to ideal performance for several models, i.e. several sets of contour turning probabilities. There are two plausible predictions for efficiency. If an observer uses his or her knowledge of the turning probabilities, we would expect no difference in efficiency across turning probabilities. On the other hand, if the observer uses a fixed prior model, we predict a peak in efficiency for turning probabilities matched to the observer's prior. We found: 1) efficiencies were peaked and high (50–77%), indicating use of a fixed intrinsic prior model; 2) the intrinsic prior favored straight contours; and 3) the computed turning probabilities from a set of natural image contours were also biased toward straight contours.

The dB[EQL]: An alternative sound pressure weighting according to the equal loudness contours of the international standard ISO 226-2003.

The conventional spectral weightings applicable to sound pressure [dB(A), etc.] are fixed in spectral shape and intended for use over certain ranges of unweighted sound pressure level: for example, the A-weighting from threshold of hearing up to 65 dB(SPL). In general, these weightings’ spectral shapes match the sensitivity of hearing as a function of frequency within “use-level” ranges, although the strong effect of the cavum conchae resonance of the ear, apparent in the equal-loudness contours of ISO 226, is not considered except in the rarely Used D-weighting. Particularly for sounds with tonal content and within the general level range of the A-weighting, the authors propose a new spectral weighting assembled from the Phon values of the complete set of equal-loudness contours calculated for each frequency within the human auditory range. It will be shown that although giving values similar to those of the A-weighting, the dB[EQL] or equal-loudness weighting is situation dependent rather than fixed, and better represents subjective impressions at all frequencies. Although based on perceived loudnesses, the dB[EQL] sound pressure weighting is not a specific loudness measurement, does not consider critical band formation, and does not yield masking or psychoacoustic loudness data.

Dose Gradient Near Target–Normal Structure Interface for Nonisocentric CyberKnife and Isocentric Intensity-Modulated Body Radiotherapy for Prostate Cancer

The treatment planning quality between nonisocentric CyberKnife (CK) and isocentric intensity modulation treatment was studied for hypofractionated prostate body radiotherapy. In particular, the dose gradient across the target and the critical structures such as the rectum and bladder was characterized. In the present study, patients treated with CK underwent repeat planning for nine fixed-field intensity-modulated radiotherapy (IMRT) using identical contour sets and dose-volume constraints. To calculate the dose falloff, the clinical target volume contours were expanded 30 mm anteriorly and posteriorly and 50 mm uniformly in other directions for all patients in the CK and IMRT plans. We found that all the plans satisfied the dose-volume constraints, with the CK plans showing significantly better conformity than the IMRT plans at a relative greater dose inhomogeneity. The rectal and bladder volumes receiving a low dose were also lower for CK than for IMRT. The average conformity index, the ratio of the prescription isodose volume and clinical target volume, was 1.18 +/- 0.08 for the CK plans vs. 1.44 +/- 0.11 for the IMRT plans. The average homogeneity index, the ratio of the maximal dose and the prescribed dose to the clinical target volume, was 1.45 +/- 0.12 for the CK plans vs. 1.28 +/- 0.06 for the IMRT plans. The average percentage of dose falloff was 2.9% +/- 0.8%/mm for CK and 3.1% +/- 1.0%/mm for IMRT in the anterior direction, 3.8% +/- 1.6%/mm for CK and 3.2% +/- 1.9%/mm for IMRT in the posterior direction, and 3.6% +/- 0.4% for CK and 3.6% +/- 0.4% for IMRT in all directions. Nonisocentric CK was as capable of producing equivalent fast dose falloff as high-number fixed-field IMRT delivery.

Pruning algorithm for Voronoi skeletons

A robust and efficient binary image shape skeleton computation procedure in 2D, including a pruning procedure, is presented. The procedure is as follows: first the shape contour is subsampled along its arclength, then the Voronoi skeleton is computed from the resulting reduced contour set of points, and finally a novel two-stage pruning procedure is applied to obtain a simplified skeleton. Besides the information reduction, this pruning makes the skeleton more robust to noise. Pruning can be done in real time thanks to some useful properties of Voronoi skeletons. Here it is proved that if the two end points of a Voronoi segment are inside the shape, then the entire segment is contained in the shape. A prototype implementation performs in real-time (60 frames per second) on an off-the-shelf computer. Testing it on an in-house but publicly available image database shows the stability and robustness of the approach.

Real-time gait classification based on fuzzy associative memory

Gait classification has a potential to be used for recognition. This paper describes a method for classifying the gaits of human bodies in video sequence and deals with the classification of human gait types based on the notion that gait types can be analysed into a series of consecutive posture types. First, according to the different sorts of movements, we make a set of standard image contours using recursion method and put them into the database. Through the hidden Markov models (HMM), different behaviour matrices based on spatio-temporal are acquired. Then, according to the video sequence, silhouettes are extracted using the background subtraction. A moment distance method is presented to obtain the similarity degree of silhouettes, which is estimated by comparing the incoming silhouettes to the database silhouettes. Finally, fuzzy associative memory (FAM) classifier is proposed to infer the gait classification of a walker. An evaluation of ten kinds of gaits involving walk, stand, faint, sit, run, bench, jump, crouch, wander and punch are given. The experiment tests show some encouraging results, which indicate that the method can be a choice for solving the problem described although more tests are required.

Contour Extraction of Human with Single-Pixel Width

A novel algorithm is presented to acquire accurate human contour. For current algorithms extracting contour with multi-pixels width, it is difficulty in obtaining accurate distance between centroid and any point on human contour for gait recognition. For connective human contour, we use candidate regions and vectors to calculate and compare the angles of adjoining vectors, so that we get point set of human contour and describe human contour of single-pixel width. For disjoint contour, image pre-processing is implemented to fuse disjoint silhouettes with their centroids. Subsequently, we go on performing the algorithm of complete contour to get accurate contour. This algorithm solves the problem that any point on human contour locates accurately. It takes the advantages in image processing of human silhouette, particularly in accurate extraction of human contour for gait or posture recognition.

Contour representation of sound signals

Event Abstract Back to Event Contour representation of sound signals Yoonseob Lim1*, Barbara G. Shinn-Cunningham1 and Timothy Gardner2 1 Boston University, Department of Cognitive and Neural Systems, United States 2 Boston University, Faculty of Electrical Engineering and Computing, United States Continuous edges, or contours, are powerful features for object recognition, both in neural and machine vision. Similarly, auditory signals are characterized by sharp edges in some classes of time-frequency analysis. Linking these edges to form contours could be relevant for auditory signal processing. However, the mathematical foundations of a general contour representation of sound have not been established. Sinusoidal representations of voiced speech and music have been explored, but these approaches do not represent broadband signals efficiently. Here we construct a two-dimensional contour representation that is generally applicable to any time series, including sound. Starting with the Short Time Fourier Transform (STFT), the method defines edges by coherent phase structure at local points in the time-frequency plane (zero crossings of a complex reassignment matrix). Continuous edges are grouped to form contours that follow the ridges and valleys of the traditional STFT. Local amplitudes are assigned by calculation of fixed points in an iterated reassignment mapping. The representation is additive; the complex amplitudes of the contours can be directly summed to reproduce the original signal. This re-synthesis matches the original signal with a signal-to-noise ratio of 15 dB or higher, even in the challenging case of white noise. In practice, this level of precision provides perceptually equivalent representations of speech and music. For many sounds of interest, a subset of the full contour collection can provide an accurate representation. To find this compact subset, an over-complete set of contours are calculated using multiple filter bandwidths. Contours are then ranked by power, length and curvature, and subject to lateral inhibition from neighboring contours. The top-ranking contours in this distribution provide a sparse representation that emerges without any prior suppositions about the nature of the original signal. By combining contours from multiple bandwidths, the representation achieves high precision in both time and frequency. As such, the method is relevant to a wide range of time-frequency tasks such as constructing receptive fields of auditory neurons, characterizing animal vocalizations, pattern recognition and signal de-noising. We speculate that neural auditory processing involves a similar contour representation. Each stage in the analysis is a plausible operation for neurons: parallel and redundant primary processing in multiple bandwidths, grouping by phase coherence, linking by continuity and lateral inhibition. Conference: Computational and Systems Neuroscience 2010, Salt Lake City, UT, United States, 25 Feb - 2 Mar, 2010. Presentation Type: Poster Presentation Topic: Poster session I Citation: Lim Y, Shinn-Cunningham BG and Gardner T (2010). Contour representation of sound signals. Front. Neurosci. Conference Abstract: Computational and Systems Neuroscience 2010. doi: 10.3389/conf.fnins.2010.03.00133 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 01 Mar 2010; Published Online: 01 Mar 2010. * Correspondence: Yoonseob Lim, Boston University, Department of Cognitive and Neural Systems, Boston, United States, yslim@bu.edu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Yoonseob Lim Barbara G Shinn-Cunningham Timothy Gardner Google Yoonseob Lim Barbara G Shinn-Cunningham Timothy Gardner Google Scholar Yoonseob Lim Barbara G Shinn-Cunningham Timothy Gardner PubMed Yoonseob Lim Barbara G Shinn-Cunningham Timothy Gardner Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Head and neck lymph node region delineation with image registration

BackgroundThe success of radiation therapy depends critically on accurately delineating the target volume, which is the region of known or suspected disease in a patient. Methods that can compute a contour set defining a target volume on a set of patient images will contribute greatly to the success of radiation therapy and dramatically reduce the workload of radiation oncologists, who currently draw the target by hand on the images using simple computer drawing tools. The most challenging part of this process is to estimate where there is microscopic spread of disease.MethodsGiven a set of reference CT images with "gold standard" lymph node regions drawn by the experts, we are proposing an image registration based method that could automatically contour the cervical lymph code levels for patients receiving radiation therapy. We are also proposing a method that could help us identify the reference models which could potentially produce the best results.ResultsThe computer generated lymph node regions are evaluated quantitatively and qualitatively.ConclusionsAlthough not conforming to clinical criteria, the results suggest the technique has promise.

A Dosimetric Selectivity Intercomparison of HDR Brachytherapy, IMRT and Helical Tomotherapy in Prostate Cancer Radiotherapy

Dose escalation in order to improve the biochemical control in prostate cancer requires the application of irradiation techniques with high conformality. The dosimetric selectivity of three radiation modalities is compared: high-dose-rate brachytherapy (HDR-BT), intensity-modulated radiation radiotherapy (IMRT), and helical tomotherapy (HT). Ten patients with prostate adenocarcinoma treated by a 10-Gy HDR-BT boost after external-beam radiotherapy were investigated. For each patient, HDR-BT, IMRT and HT theoretical treatment plans were realized using common contour sets. A 10-Gy dose was prescribed to the planning target volume (PTV). The PTVs and critical organs' dose-volume histograms obtained were compared using Student's t-test. HDR-BT delivers spontaneously higher mean doses to the PTV with smaller cold spots compared to IMRT and HT. 33% of the rectal volume received a mean HDR-BT dose of 3.86 + or - 0.3 Gy in comparison with a mean IMRT dose of 6.57 + or - 0.68 Gy and a mean HT dose of 5.58 + or - 0.71 Gy (p < 0.0001). HDR-BT also enables to better spare the bladder. The hot spots inside the urethra are greater with HDR-BT. The volume of healthy tissue receiving 10% of the prescribed dose is reduced at least by a factor of 8 with HDR-BT (p < 0.0001). HDR-BT offers better conformality in comparison with HT and IMRT and reduces the volume of healthy tissue receiving a low dose.

Comparison of Virtual HDR Prostate Treatment Plans Created with Fixed and Variable Aperture Collimators

We previously compared Virtual HDR prostate CyberKnife System (CK) SBRT plans versus simulated HDR brachytherapy plans, based on identical contour sets for each comparison plan pair, in 10 consecutive patients (Int J Radiat Oncol Biol Phys 2008; 70: 1588-1597). In the current analysis, for the same patient cohort, we assess the same endpoints for plans created using the recently released Iris™ Variable Aperture Collimator. The 10 Virtual HDR prostate CK cases were planned and treated using one or two fixed collimators (“Fixed”). The prescription dose was 38 Gy delivered in 4 fractions. These cases were replanned using the Iris Collimator and the recently released Sequential Optimization inverse planning algorithm (“Iris”). The Iris Collimator allows the use of any of 12 field sizes between 5 and 60 mm for each beam in a single traversal of the robotic manipulator. Replanning objectives included maintaining or improving the conformality and normal tissue sparing of the original plan, increasing extraurethral-intraprostatic dose escalation, and minimizing the number of beams and monitor units (MU). Median (range): Non-zero beams: 266 (234-318), Fixed; 191 (141-208), Iris; median difference 92, 10/10 cases lower with Iris. MU: 101.2K (76.0K-116.6K), Fixed; 76.4K (67.1K-89.2K), Iris; 10/10 cases lower with Iris. Beam-on time: 42.2 min, Fixed (600 MU/min CK platform); 23.9 min, Iris (800 mu/min CK platform). Rx isodose line: 57% (49-67%), Fixed; 53% (47-60%), Iris; 10/10 cases same or lower with Iris. V125: 43.95% (28.4-55.5%), Fixed; 45.6% (35.5-55.9%), Iris; 7/10 cases higher with Iris. V150: 8.45% (0.1-20.5%), Fixed; 18.05% (3.0-22.0%), Iris; 9/10 cases higher with Iris. nCI: 1.14 (1.10-1.23), Fixed; 1.12 (1.10-1.20), Iris; 8/10 cases same or lower with Iris. Urethra Dmax: 44.25 Gy (43.1-46.1 Gy), Fixed; 42.05 Gy (40.6-43.4 Gy), Iris; 9/10 cases lower with Iris. Rectum Dmax, Bladder Dmax, Urethra D50: No significant difference. Treatment plans generated using the Iris Collimator and Sequential Optimization consistently have considerably fewer beams and MU than plans generated using one or two fixed collimators, with a median 43% reduction of beam on time per case. Part of the time reduction is due to a higher dose rate linac (800 vs. 600 MU/min). Simultaneously, the Iris Collimator plans typically have similar or better conformality, higher maximum intraprostatic doses, lower maximum urethral doses, and similar maximum doses to the bladder and rectum. In summary, using multiple field sizes enabled by the Iris Collimator can produce treatment plans with a more tailored, HDR-like dose distribution and that can be delivered more efficiently than plans created with one or two fixed collimators.

The Diabatic Contour-Advective Semi-Lagrangian Algorithms for the Spherical Shallow Water Equations

Abstract The diabatic contour-advective semi-Lagrangian (DCASL) algorithm is extended to the thermally forced shallow water equations on the sphere. DCASL rests on the partitioning of potential vorticity (PV) to adiabatic and diabatic parts solved, respectively, by contour advection and a grid-based conventional algorithm. The presence of PV in the source term for diabatic PV makes the shallow water equations distinct from the quasigeostrophic model previously studied. To address the more rapid generation of finescale structures in diabatic PV, two new features are added to DCASL: (i) the use of multiple sets of contours with successively finer contour intervals and (ii) the application of the underlying method of DCASL at a higher level to diabatic PV. That is, the diabatic PV is allowed to have both contour and grid parts. The added features make it possible to make the grid part of diabatic PV arbitrarily small and thus pave the way for a fully Lagrangian DCASL in the presence of forcing. The DCASL algorithms are constructed using a standard semi-Lagrangian (SL) algorithm to solve for the grid-based part of diabatic PV. The 25-day time evolution of an unstable midlatitude jet triggered by the action of thermal forcing is used as a test case to examine and compare the properties of the DCASL algorithms with a pure SL algorithm for PV. Diagnostic measures of vortical and unbalanced activity as well as of the relative strength of the grid and contour parts of the solution for PV indicate that the superiority of contour advection can be maintained even in the presence of strong, nonsmooth forcing.

Shape Guided Contour Grouping with Particle Filters.

We propose a novel framework for contour based object detection and recognition, which we formulate as a joint contour fragment grouping and labeling problem. For a given set of contours of model shapes, we simultaneously perform selection of relevant contour fragments in edge images, grouping of the selected contour fragments, and their matching to the model contours. The inference in all these steps is performed using particle filters (PF) but with static observations. Our approach needs one example shape per class as training data. The PF framework combined with decomposition of model contour fragments to part bundles allows us to implement an intuitive search strategy for the target contour in a clutter of edge fragments. First a rough sketch of the model shape is identified, followed by fine tuning of shape details. We show that this framework yields not only accurate object detections but also localizations in real cluttered images.

Pillars of World Christianity: A Review Essay

Pillars of World Christianity:A Review Essay Robert Eric Frykenberg (bio) Lamin Sanneh, Disciples of All Nations: Pillars of World Christianity (Oxford University Press, 2008). "Christianity triumphs by the relinquishing of Jerusalem or any fixed universal centre, be it geographical, linguistic or cultural, with the result that we have a proliferation of centers, languages and cultures within the Church. Christian ecumenism is a pluralism of the periphery with only God at the center."1 "I . . . have reversed the argument by speaking of the indigenous discovery [and appropriation] of Christianity rather than the Christian discovery of indigenous societies."2 Avast, overarching pavilion of world Christianity now covers more than 2 billion people. Christianity, Lamin Sanneh makes clear, is not only the world's first truly global religion, but also "among the world's fastest growing religions." Sanneh describes key pillars that support this pavilion. These serve to explain—in mingled chronological, geographical, and topical perspectives—how world Christianity came into being and how it has become what it now is. Each pillar defines a crucial set of contours for gaining a clearer understanding of world Christianity. The first pillar examined by Sanneh is biblical or scriptural. This arises out of the New Testament itself. Unless one sees the New Testament as primarily a missionary document, one cannot explain the expansion or the nature of world Christianity. Christian faith, while it was initially linked to Jewish culture, quickly became cross-cultural and pluralistic, rapidly spreading beyond its initial matrix in Jerusalem and moving out into Judea, Samaria, and the Hellenistic world. Deep interpenetrations within the Greco Roman world were followed by encounters with the cultures of Mesopotamia, Armenia, Ethiopia, India, Persia, and China in the east, and Celtic, Germanic, and Slavic peoples in the west. Each encounter led to unique challenges, and resulted in a further metamorphosing of the gospel itself. Christianity is no more inherently European (Western) than it is Asian (Eastern), or African (Southern). The origins of Christian faith, after all, lay not in Europe but in the Middle East. The key feature of Sanneh's second pillar is its unbounded non-territoriality. Christianity abolished territoriality as a requirement of faith. The Jewish temple, hitherto hallowed as God's sanctuary, an immutable and permanent structure located in Jerusalem, ceased to exist. Instead, the abode of God's indwelling spirit was located within each redeemed person. As a consequence, the temple became mobile, personal, and non-territorial. No longer was the promised land a fixed geographical place on Earth. By sincere and true conviction, each convert became a free agent. Ultimately, therefore, Christendom became the antithesis of true Christianity. Perhaps the central pillar of this entire work, linking all other pillars as structural supports for world Christianity, is translatability. As the faith expanded and spread into new environments, it had to face new challenges. Christian communities, both beneath and beyond Hellenistic culture and Roman imperial rule, established themselves as minorities within non-Christian societies. Translatability meant that faith could no longer remain enshrined, encapsulated, idolized, or imprisoned within any single language. Rather, it was possible for God's spirit to move into any language and transform the hearts and minds of individuals. Pentecost, that singular occasion in Jerusalem when each person heard what was being spoken "in his own tongue," reversed Babel. From within the genius of each language and culture, special new features could be grafted into ever new and emerging forms of Christianity. "[T]he eventual result" of the fermentation of the faith within Hellenistic cultures in Antioch and Alexandria, Sanneh writes, "was Christian theology as we know it." An "intellectual shift" opened the way forward "for other cultures and societies, and a break from the obligation to follow precedent" or "imitate past examples" (10). In the words of Paul: "There is neither Jew nor Greek, there is neither slave nor free, there is neither male nor female: for you are all one the Christ [End Page 7] Jesus. And if you are Christ's, then you are Abraham's offspring, heir according to promise" (Galatians 3: 24-29). Such is the importance Sanneh attaches to this pillar that, in one way or another, allusions to it crop up...

SU-FF-I-90: A Clinical Evaluation of the M-Rep-Based Automatic Prostate Segmentation

Purpose: To evaluate the clinical application readiness of a statistically trainable deformable shape model, called an m‐rep, for automatic segmentation of the prostate from CTimages by comparison with manual contouring. Method and Materials: ConStruct, an in‐house automatic prostate segmentation tool featuring m‐rep (medial representations) models, was used in this study. This study is to test the robustness of the m‐rep models for prostate treatment planning segmentation in routine use. For each patient case, an m‐rep was initialized and automatically deformed to segment the prostate. Ground truth was taken to be the contour set used for treatment planning. Two radiation oncologists each manually created an additional contour set. The average distance between m‐rep segmentation (or manual segmentation) and the ground truth was calculated. Retrospective clinical validation was also carried out in all cases. Two radiation oncologists blindly scored all the contour sets including the ground truth. Score 1: perfect contour—no corrections needed; 2: minor correction—less than one third of the slices require correction; 3: major correction—more efficient than redrawing all the contours from scratch; 4: not acceptable. Results: Averaged over five patients, the average distances between m‐rep, set 1 and 2 manual contour sets and the ground truth are 0.51, 0.45, and 0.42 cm, respectively. The average scores for m‐rep, set 1, set 2 contour sets, and the ground truth are 2.4, 2.4, 2.0, and 2.1, respectively. Conclusion: The qualitative and clinical validations were performed on m‐rep‐based automatic segmentation by comparing it to manual contouring. M‐reps appeared to produce reasonable and acceptable prostate contour sets when compared to those generated by clinicians. We propose that m‐reps be used to improve clinical efficiency by automatically contouring the prostate as a starting shape and then manually editing when needed. Further validation on a larger patient cohort is indicated.

WE‐C‐BRC‐03: Evaluating Extent of Cell Death in 3D Mid‐To‐High Frequency Ultrasound by Registration with Whole‐Mount Tumor Histopathology

Purpose: In this study, we investigate the precision and accuracy of mid‐to‐high frequency ultrasound imaging to assess non‐invasively cell death for incorporation of this method in pre‐clinical and clinical practice to characterize tumor response to radiotherapy. Method and Materials: Tumor xenografts (n=8) of head and neck cancer were exposed to radiation doses of 2, 4 and 8Gy. Ultrasound images were collected with an ultrasound scanner using frequencies of 15–35MHz before and 24 hours after exposure to radiation. Irradiated tumors exhibited large hyperechoic regions in ultrasounds images 24 hours after exposure to radiation that corresponded to areas of cell death in histology. The ultrasound images were registered with the histological images of the tumor slices taken at regular intervals. The tumor was contoured on histological slices and ultrasound images, the regions of cell death were contoured on histological slices and the hyperechoic regions were contoured on ultrasound images. Each set of contours was converted to a surface mesh. The volume and center of mass were calculated for each representation determined by a surface mesh. Results: The average difference between the relative (to histology) volume representations in histology and ultrasound were 10.7%±8.9% for tumor and 21.7%±12.2% for cell death. The average differences between the relative (to the maximum dimension of the tumor) center of mass of volume representations in histology and ultrasound images were 2.7%±2.0% for tumor and 15.5%±8.9 % for cell death. Conclusion: The method provides the correspondence between the volumes of cell death assessed from histology and from ultrasound imaging and can be used to assess early tumor response to radiotherapy. Part of the differences associated with cell death representation in histological and ultrasound images (21.7%) was caused by the differences in tumor representation (10.7%) in these images. The effect of these uncertainties is the subject of ongoing investigation.

SU-FF-T-571: A Dosimetric Comparison of Stereotactic Body Radiation Therapy Irradiation Techniques: CyberKnife Versus Conventional Linac-Based Systems

Purpose: The purpose of this study is to compare the different dosemetric characteristics of Linac‐based SBRT and that of Cyberknife for lungtumortreatment.Methods: Eight patients with lungtumors received Linac‐based SBRT were retrospectively included in this study. 60Gy photondose delivered in 5 frictions was prescribed to each target. To minimize respiratory motion impact, Synchrony™ (AccurayInc., Sunnyvale, CA) and a 4D dose calculation program were used for Cyberknife and Linac‐based SBRTtreatment planning respectively. Identical patients' image (50% phase image of 4DCT corresponding to the end of exhalation) and contour sets were used for dose calculation. The DVHs of PTV, GTV, and lung were studied. Results: Both modalities can provide satisfactory dose coverage to target tumor. The lungdose (2.1±0.8Gy to 1500cc and 4.3±2.1Gy to 1000cc) is well below institutional constrains. Lungdose of Cyberknife plans is more susceptible to the tumor location than that of Linac‐based SBRT plan. When tumor attaches to anterior chest wall, Cyberknife may deliver less dose to patient lung than Linac‐based SBRT. When the tumor becomes more posterior, lungdose of Cyberknife plan increases much more quickly than that of Linac‐based SBRT plan. Cyberknife may delivery higher dose to lung than Linac‐based SBRT when the tumor is located close to the posterior chest wall. The dose distribution of Cyberknife is more heterogeneous than Linac‐based SBRT in all cases. Conclusion: Both Linac‐based SBRT and Cyberknife can provide adequate dose coverage for target tumor while sparing normal tissue. Cyberknife may delivery less dose to lung than Linac‐based SBRT when the tumor is close to anterior chest wall but more dose to lung when tumor attached to posterior chest wall. This study may provide useful information to help radiation oncologist to choose SBRT modalities for lungtumortreatment.