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Marcel Van Herk - One of the best experts on this subject based on the ideXlab platform.
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Quantification of Shape Variation of prostate and seminal vesicles during external beam radiotherapy.
International journal of radiation oncology biology physics, 2005Co-Authors: Kirsten E.i. Deurloo, R. Steenbakkers, Lambert Zijp, Josien De Bois, Peter J.c.m. Nowak, Coen R.n. Rasch, Marcel Van HerkAbstract:PURPOSE: The prostate is known to translate and rotate under influence of rectal filling changes and many studies have addressed the magnitude of these motions. However, prostate Shape Variations also have been reported. For image-guided radiotherapy, it is essential to know the relative magnitude of translations, rotations, and Shape Variation so that the most appropriate correction strategy can be chosen. However, no quantitative analysis of Shape Variation has been performed. It is, therefore, the purpose of this article to develop a method to determine Shape Variation of complex organs and apply it to determine Shape Variation during external beam radiotherapy of a GTV (gross tumor volume) consisting of prostate and seminal vesicles. METHODS AND MATERIALS: For this study, the data of 19 patients with prostate cancer were used. Each patient received a planning computed tomography (CT) scan and 8-12 (11 on average) repeat CT scans that were made during the course of conformal radiotherapy. One observer delineated the GTV in all scans, and volume Variations were measured. After matching the GTVs for each patient for translation and rotation, a coverage probability matrix was constructed and the 50% isosurface was taken to determine the average GTV surface. Perpendicular distances between the average GTV and the individual GTVs were calculated for each point of the average GTV, and their Variation was expressed in terms of local standard deviation (SD). The local SDs of the Shape Variation of all 19 patients were mapped onto a reference case by matching and morphing of the individual average GTVs. Repeated delineation of the GTV was done for 6 patients to determine intraobserver Variation. Finally, the measured Shape Variation was corrected for intraobserver Variation to estimate the "real" Shape Variation. RESULTS: No significant Variations in GTV volume were observed. The measured Shape Variation (including delineation Variation) was largest at the tip of the vesicles (SD = 2.0 mm), smallest at the left and right side of the prostate (SD = 1.0 mm), and average elsewhere (SD = 1.5 mm). At the left, right, and cranial sides of the prostate, the intraobserver Variation was of the same order of magnitude as the measured Shape Variation; elsewhere it was smaller. However, the accuracy of the estimated SD for intraobserver Variation was about half of the accuracy of the estimated SD for the measured Shape Variation, giving an overall uncertainty of maximum 0.6 mm SD in the estimate of the "real" Shape Variation. The "real" Shape Variation was small at the left, right, and cranial side of the prostate (SD
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quantification of Shape Variation of prostate and seminal vesicles during external beam radiotherapy
International Journal of Radiation Oncology Biology Physics, 2005Co-Authors: Kirsten E.i. Deurloo, R. Steenbakkers, Lambert Zijp, Josien De Bois, Peter J.c.m. Nowak, Coen R.n. Rasch, Marcel Van HerkAbstract:PURPOSE: The prostate is known to translate and rotate under influence of rectal filling changes and many studies have addressed the magnitude of these motions. However, prostate Shape Variations also have been reported. For image-guided radiotherapy, it is essential to know the relative magnitude of translations, rotations, and Shape Variation so that the most appropriate correction strategy can be chosen. However, no quantitative analysis of Shape Variation has been performed. It is, therefore, the purpose of this article to develop a method to determine Shape Variation of complex organs and apply it to determine Shape Variation during external beam radiotherapy of a GTV (gross tumor volume) consisting of prostate and seminal vesicles. METHODS AND MATERIALS: For this study, the data of 19 patients with prostate cancer were used. Each patient received a planning computed tomography (CT) scan and 8-12 (11 on average) repeat CT scans that were made during the course of conformal radiotherapy. One observer delineated the GTV in all scans, and volume Variations were measured. After matching the GTVs for each patient for translation and rotation, a coverage probability matrix was constructed and the 50% isosurface was taken to determine the average GTV surface. Perpendicular distances between the average GTV and the individual GTVs were calculated for each point of the average GTV, and their Variation was expressed in terms of local standard deviation (SD). The local SDs of the Shape Variation of all 19 patients were mapped onto a reference case by matching and morphing of the individual average GTVs. Repeated delineation of the GTV was done for 6 patients to determine intraobserver Variation. Finally, the measured Shape Variation was corrected for intraobserver Variation to estimate the "real" Shape Variation. RESULTS: No significant Variations in GTV volume were observed. The measured Shape Variation (including delineation Variation) was largest at the tip of the vesicles (SD = 2.0 mm), smallest at the left and right side of the prostate (SD = 1.0 mm), and average elsewhere (SD = 1.5 mm). At the left, right, and cranial sides of the prostate, the intraobserver Variation was of the same order of magnitude as the measured Shape Variation; elsewhere it was smaller. However, the accuracy of the estimated SD for intraobserver Variation was about half of the accuracy of the estimated SD for the measured Shape Variation, giving an overall uncertainty of maximum 0.6 mm SD in the estimate of the "real" Shape Variation. The "real" Shape Variation was small at the left, right, and cranial side of the prostate (SD <0.5 mm) and between 0.5 mm and 1.6 mm elsewhere. CONCLUSIONS: We developed a method to quantify Shape Variation of organs with a complex Shape and applied it to a GTV consisting of prostate and seminal vesicles. Deformation of prostate and seminal vesicles during the course of radiotherapy is small (relative to organ motion). Therefore, it is a valid approximation in image-guided radiotherapy of prostate cancer, in first order, to correct only for setup errors and organ motion. Prostate and seminal vesicles deformation can be considered as a second-order effect.
Marcelo R. Sánchez-villagra - One of the best experts on this subject based on the ideXlab platform.
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Shape Variation and modularity of skull and teeth in domesticated horses and wild equids
Frontiers in Zoology, 2018Co-Authors: Laura Heck, Laura A. B. Wilson, Allowen Evin, Madlen Stange, Marcelo R. Sánchez-villagraAbstract:Background In horses, the morphological changes induced by the process of domestication are reportedly less pronounced than in other species, such as dogs or pigs – although the horses’ disparity has rarely been empirically tested. We investigated Shape differences and modularity of domesticated horses, Przewalski’s horses, donkeys and zebras. Mandibular and tooth Shape have been shown to be valuable features for differentiating wild and domesticated forms in some mammals. Results Both mandible and teeth, show a pattern of Shape space occupation analogous to that of the cranium, with domesticated horses occupying a similar extension in Shape space to that of wild equids. Only cranial Shape data exhibit a tendency to separate domesticated horses and Przewalski’s horses from donkeys and zebras. Maximum likelihood model-based tests confirm the horse cranium is composed of six developmental modules, as reported for placental mammals in general. The magnitude of integration in domesticated horse skull was lower than in wild equids across all six cranial modules, and lower values of integration were associated with higher disparity values across all modules. Conclusion This is the first study that combines different skeletal features for the description and comparison of Shape changes in all living equid groups using geometric morphometrics. We support Darwin’s hypothesis that the Shape Variation in the skull of domesticated horses is similar to the Shape Variation of all wild equid species existing today. Lower magnitudes of module integration are recovered in domesticated horses compared to their wild relatives.
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Shape Variation and modularity of skull and teeth in domesticated horses and wild equids.
Frontiers in zoology, 2018Co-Authors: Laura Heck, Laura A. B. Wilson, Allowen Evin, Madlen Stange, Marcelo R. Sánchez-villagraAbstract:In horses, the morphological changes induced by the process of domestication are reportedly less pronounced than in other species, such as dogs or pigs – although the horses’ disparity has rarely been empirically tested. We investigated Shape differences and modularity of domesticated horses, Przewalski’s horses, donkeys and zebras. Mandibular and tooth Shape have been shown to be valuable features for differentiating wild and domesticated forms in some mammals. Both mandible and teeth, show a pattern of Shape space occupation analogous to that of the cranium, with domesticated horses occupying a similar extension in Shape space to that of wild equids. Only cranial Shape data exhibit a tendency to separate domesticated horses and Przewalski’s horses from donkeys and zebras. Maximum likelihood model-based tests confirm the horse cranium is composed of six developmental modules, as reported for placental mammals in general. The magnitude of integration in domesticated horse skull was lower than in wild equids across all six cranial modules, and lower values of integration were associated with higher disparity values across all modules. This is the first study that combines different skeletal features for the description and comparison of Shape changes in all living equid groups using geometric morphometrics. We support Darwin’s hypothesis that the Shape Variation in the skull of domesticated horses is similar to the Shape Variation of all wild equid species existing today. Lower magnitudes of module integration are recovered in domesticated horses compared to their wild relatives.
Elizabeth H. Harmon - One of the best experts on this subject based on the ideXlab platform.
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Size and Shape Variation in the proximal femur of Australopithecus africanus
Journal of human evolution, 2009Co-Authors: Elizabeth H. HarmonAbstract:Aside from use as estimates of body mass dimorphism and fore to hind limb joint size comparisons, postcranial elements have not often contributed to assessments of Variation in Australopithecus africanus. Meanwhile, cranial, facial, and dental size Variation is interpreted to be high or moderately high. Further, the cranial base and face express patterns of structural (Shape) Variation, which are interpreted by some as evidence for the presence of multiple species. Here, the proximal femur is used to consider postcranial size and Shape Variation in A. africanus. Original fossils from Makapansgat and Sterkfontein, and samples from Homo, Pan, Gorilla, and Pongo were measured. Size Variation was assessed by comparing the A. africanus coefficient of Variation to bootstrapped distributions of coefficient of Variation samples for each taxon. Shape Variation was assessed from isometrically adjusted Shape variables. First, the A. africanus standard deviation of log transformed Shape variables was compared to bootstrapped distributions of logged standard deviations in each taxon. Second, Shape variable based Euclidean distances between fossil pairs were compared to pairwise Euclidean distance distributions in each reference taxon. The degree of size Variation in the A. africanus proximal femur is consistent with that of a single species, and is most comparable to Homo and Pan, lower than A. afarensis, and lower than some estimates of cranial and dental Variation. Some, but not all, Shape variables show more Variation in A. africanus than in extant taxa. The degree of Shape difference between some fossils exceeds the majority of pairwise differences in the reference taxa. Proximal femoral Shape, but not size, Variation is consistent with high estimates of A. africanus cranial Variation.
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Size and Shape Variation in Australopithecus afarensis proximal femora
Journal of human evolution, 2006Co-Authors: Elizabeth H. HarmonAbstract:Abstract The degree of size and Shape Variation in the A. afarensis fossil sample has been interpreted in a variety of ways. Size Variation has been described as exceeding that of extant hominoids, similar to that of strongly sexually dimorphic hominoids, and best matched to modern humans. The degree of Shape Variation has been characterized both as great and negligible. Recent fieldwork has increased the proximal femoral sample, providing new data with which to examine Variation. The proximal femur of A. afarensis is analyzed in a comparative framework in order to gauge the magnitude of size and Shape Variation in this element. Seven of the best-preserved A. afarensis proximal femora contribute to the analysis (A.L. 128-1, A.L. 152-2, A.L. 211-1, A.L. 288-1ap, A.L. 333-3, A.L. 333-123, A.L. 827-1). Comparative samples from Pan , Pongo , Gorilla , and Homo provide context for interpreting Variation among the fossils. The coefficient of Variation (CV) of linear measurements is used to estimate size Variation. Bootstrap resampling of CVs from extant hominoids provides distributions for comparison to A. afarensis CVs. Ratios of linear measurements provide scale-free Shape variables that are used in pairwise comparisons. The Euclidean distance between pairs of A. afarensis are compared to the Euclidean distances between extant hominoid pairs. As found in some earlier analyses, size Variation in A. afarensis is accommodated best in gorillas and orangutans. The magnitude of difference in Shape between A. afarensis pairs is exceeded by most taxa, indicating that Shape Variation is not extreme. These general findings are contradicted by a few instances of excessive size and Shape Variation. These are uncharacteristic results and could point to temporal bias, although other alternatives are explored. The signal from the proximal femur is that size Variation in A. afarensis is like that of the strongly sexually dimorphic apes, and Shape Variation is well within the range of most hominoids irrespective of their degree of size dimorphism.
Kirsten E.i. Deurloo - One of the best experts on this subject based on the ideXlab platform.
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Quantification of Shape Variation of prostate and seminal vesicles during external beam radiotherapy.
International journal of radiation oncology biology physics, 2005Co-Authors: Kirsten E.i. Deurloo, R. Steenbakkers, Lambert Zijp, Josien De Bois, Peter J.c.m. Nowak, Coen R.n. Rasch, Marcel Van HerkAbstract:PURPOSE: The prostate is known to translate and rotate under influence of rectal filling changes and many studies have addressed the magnitude of these motions. However, prostate Shape Variations also have been reported. For image-guided radiotherapy, it is essential to know the relative magnitude of translations, rotations, and Shape Variation so that the most appropriate correction strategy can be chosen. However, no quantitative analysis of Shape Variation has been performed. It is, therefore, the purpose of this article to develop a method to determine Shape Variation of complex organs and apply it to determine Shape Variation during external beam radiotherapy of a GTV (gross tumor volume) consisting of prostate and seminal vesicles. METHODS AND MATERIALS: For this study, the data of 19 patients with prostate cancer were used. Each patient received a planning computed tomography (CT) scan and 8-12 (11 on average) repeat CT scans that were made during the course of conformal radiotherapy. One observer delineated the GTV in all scans, and volume Variations were measured. After matching the GTVs for each patient for translation and rotation, a coverage probability matrix was constructed and the 50% isosurface was taken to determine the average GTV surface. Perpendicular distances between the average GTV and the individual GTVs were calculated for each point of the average GTV, and their Variation was expressed in terms of local standard deviation (SD). The local SDs of the Shape Variation of all 19 patients were mapped onto a reference case by matching and morphing of the individual average GTVs. Repeated delineation of the GTV was done for 6 patients to determine intraobserver Variation. Finally, the measured Shape Variation was corrected for intraobserver Variation to estimate the "real" Shape Variation. RESULTS: No significant Variations in GTV volume were observed. The measured Shape Variation (including delineation Variation) was largest at the tip of the vesicles (SD = 2.0 mm), smallest at the left and right side of the prostate (SD = 1.0 mm), and average elsewhere (SD = 1.5 mm). At the left, right, and cranial sides of the prostate, the intraobserver Variation was of the same order of magnitude as the measured Shape Variation; elsewhere it was smaller. However, the accuracy of the estimated SD for intraobserver Variation was about half of the accuracy of the estimated SD for the measured Shape Variation, giving an overall uncertainty of maximum 0.6 mm SD in the estimate of the "real" Shape Variation. The "real" Shape Variation was small at the left, right, and cranial side of the prostate (SD
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quantification of Shape Variation of prostate and seminal vesicles during external beam radiotherapy
International Journal of Radiation Oncology Biology Physics, 2005Co-Authors: Kirsten E.i. Deurloo, R. Steenbakkers, Lambert Zijp, Josien De Bois, Peter J.c.m. Nowak, Coen R.n. Rasch, Marcel Van HerkAbstract:PURPOSE: The prostate is known to translate and rotate under influence of rectal filling changes and many studies have addressed the magnitude of these motions. However, prostate Shape Variations also have been reported. For image-guided radiotherapy, it is essential to know the relative magnitude of translations, rotations, and Shape Variation so that the most appropriate correction strategy can be chosen. However, no quantitative analysis of Shape Variation has been performed. It is, therefore, the purpose of this article to develop a method to determine Shape Variation of complex organs and apply it to determine Shape Variation during external beam radiotherapy of a GTV (gross tumor volume) consisting of prostate and seminal vesicles. METHODS AND MATERIALS: For this study, the data of 19 patients with prostate cancer were used. Each patient received a planning computed tomography (CT) scan and 8-12 (11 on average) repeat CT scans that were made during the course of conformal radiotherapy. One observer delineated the GTV in all scans, and volume Variations were measured. After matching the GTVs for each patient for translation and rotation, a coverage probability matrix was constructed and the 50% isosurface was taken to determine the average GTV surface. Perpendicular distances between the average GTV and the individual GTVs were calculated for each point of the average GTV, and their Variation was expressed in terms of local standard deviation (SD). The local SDs of the Shape Variation of all 19 patients were mapped onto a reference case by matching and morphing of the individual average GTVs. Repeated delineation of the GTV was done for 6 patients to determine intraobserver Variation. Finally, the measured Shape Variation was corrected for intraobserver Variation to estimate the "real" Shape Variation. RESULTS: No significant Variations in GTV volume were observed. The measured Shape Variation (including delineation Variation) was largest at the tip of the vesicles (SD = 2.0 mm), smallest at the left and right side of the prostate (SD = 1.0 mm), and average elsewhere (SD = 1.5 mm). At the left, right, and cranial sides of the prostate, the intraobserver Variation was of the same order of magnitude as the measured Shape Variation; elsewhere it was smaller. However, the accuracy of the estimated SD for intraobserver Variation was about half of the accuracy of the estimated SD for the measured Shape Variation, giving an overall uncertainty of maximum 0.6 mm SD in the estimate of the "real" Shape Variation. The "real" Shape Variation was small at the left, right, and cranial side of the prostate (SD <0.5 mm) and between 0.5 mm and 1.6 mm elsewhere. CONCLUSIONS: We developed a method to quantify Shape Variation of organs with a complex Shape and applied it to a GTV consisting of prostate and seminal vesicles. Deformation of prostate and seminal vesicles during the course of radiotherapy is small (relative to organ motion). Therefore, it is a valid approximation in image-guided radiotherapy of prostate cancer, in first order, to correct only for setup errors and organ motion. Prostate and seminal vesicles deformation can be considered as a second-order effect.
Laura Heck - One of the best experts on this subject based on the ideXlab platform.
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Shape Variation and modularity of skull and teeth in domesticated horses and wild equids
Frontiers in Zoology, 2018Co-Authors: Laura Heck, Laura A. B. Wilson, Allowen Evin, Madlen Stange, Marcelo R. Sánchez-villagraAbstract:Background In horses, the morphological changes induced by the process of domestication are reportedly less pronounced than in other species, such as dogs or pigs – although the horses’ disparity has rarely been empirically tested. We investigated Shape differences and modularity of domesticated horses, Przewalski’s horses, donkeys and zebras. Mandibular and tooth Shape have been shown to be valuable features for differentiating wild and domesticated forms in some mammals. Results Both mandible and teeth, show a pattern of Shape space occupation analogous to that of the cranium, with domesticated horses occupying a similar extension in Shape space to that of wild equids. Only cranial Shape data exhibit a tendency to separate domesticated horses and Przewalski’s horses from donkeys and zebras. Maximum likelihood model-based tests confirm the horse cranium is composed of six developmental modules, as reported for placental mammals in general. The magnitude of integration in domesticated horse skull was lower than in wild equids across all six cranial modules, and lower values of integration were associated with higher disparity values across all modules. Conclusion This is the first study that combines different skeletal features for the description and comparison of Shape changes in all living equid groups using geometric morphometrics. We support Darwin’s hypothesis that the Shape Variation in the skull of domesticated horses is similar to the Shape Variation of all wild equid species existing today. Lower magnitudes of module integration are recovered in domesticated horses compared to their wild relatives.
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Shape Variation and modularity of skull and teeth in domesticated horses and wild equids.
Frontiers in zoology, 2018Co-Authors: Laura Heck, Laura A. B. Wilson, Allowen Evin, Madlen Stange, Marcelo R. Sánchez-villagraAbstract:In horses, the morphological changes induced by the process of domestication are reportedly less pronounced than in other species, such as dogs or pigs – although the horses’ disparity has rarely been empirically tested. We investigated Shape differences and modularity of domesticated horses, Przewalski’s horses, donkeys and zebras. Mandibular and tooth Shape have been shown to be valuable features for differentiating wild and domesticated forms in some mammals. Both mandible and teeth, show a pattern of Shape space occupation analogous to that of the cranium, with domesticated horses occupying a similar extension in Shape space to that of wild equids. Only cranial Shape data exhibit a tendency to separate domesticated horses and Przewalski’s horses from donkeys and zebras. Maximum likelihood model-based tests confirm the horse cranium is composed of six developmental modules, as reported for placental mammals in general. The magnitude of integration in domesticated horse skull was lower than in wild equids across all six cranial modules, and lower values of integration were associated with higher disparity values across all modules. This is the first study that combines different skeletal features for the description and comparison of Shape changes in all living equid groups using geometric morphometrics. We support Darwin’s hypothesis that the Shape Variation in the skull of domesticated horses is similar to the Shape Variation of all wild equid species existing today. Lower magnitudes of module integration are recovered in domesticated horses compared to their wild relatives.
