The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform

A Schramm - One of the best experts on this subject based on the ideXlab platform.

  • SU‐GG‐T‐77: Application and Dosimetric Analysis of Multiple Static Tangential Intensity‐Modulated Radiotherapy Beams in An Elliptic Paraboloid‐Shaped Superficial Tumor
    Medical Physics, 2008
    Co-Authors: Charles Shang, T Williams, R Girouard, A Schramm
    Abstract:

    Purpose is to evaluate dosimetric efficacy for LINAC‐based IMRT for an Elliptic Paraboloid‐shaped shallow target. Method and Materials: This study includes a case with advanced facial multi‐focal basal cell carcinoma. The lesion variably extended entire face, up to 3.5 cm deep. A simulation target was created in a cylindrical water phantom for evaluating different plans. All IMRT plans comprised of eleven coplanar 6‐MV photon beams with 5mm sMLC. Only outer portion of each beam opens to the PTV. Identical beam constraints with 4mm MLC stepping were used. In group A, the MLC travels along the shorter dimension of PTV cross section, while in group B, MLC moves alone the longer dimension. 50.0 Gy is normalized to 95% of PTV in all plans. Results:Dose for the organ at risk (OAR) was shown reduction in both groups, when the independent jaw blocks more open field. The mean dose reduction was 15.9% and 18.9% respectively when the jaw moved from +2 cm to 0 cm (half beam blocked. More significant improvement (> 27%) in dose sparing was indicated with the jaw set further into the field. No consistent trend of changes in dose homogeneities was found, except when the jaw partially blocked the PTV. In the final clinic case, more than 90% of PTV received the prescribed 45Gy dose with about 19% meaningful dose heterogeneity (effective 50Gy for majority of treated areas), and satisfactory dose conformity. Treatments were comfortably fitted in 15‐minute daily schedule. The treatment resulted in an excellent clinical outcome without cosmetic complications seen during the first 12 month follow‐ups. Conclusion: This study demonstrates the feasibility of the application of LINAC based individualized IMRT for an Elliptic Paraboloid‐shaped superficial target. Further clinical trials will be designed for the treatment of chest malignancy.

  • su gg t 77 application and dosimetric analysis of multiple static tangential intensity modulated radiotherapy beams in an Elliptic Paraboloid shaped superficial tumor
    Medical Physics, 2008
    Co-Authors: Charles Shang, T Williams, R Girouard, A Schramm
    Abstract:

    Purpose is to evaluate dosimetric efficacy for LINAC‐based IMRT for an Elliptic Paraboloid‐shaped shallow target. Method and Materials: This study includes a case with advanced facial multi‐focal basal cell carcinoma. The lesion variably extended entire face, up to 3.5 cm deep. A simulation target was created in a cylindrical water phantom for evaluating different plans. All IMRT plans comprised of eleven coplanar 6‐MV photon beams with 5mm sMLC. Only outer portion of each beam opens to the PTV. Identical beam constraints with 4mm MLC stepping were used. In group A, the MLC travels along the shorter dimension of PTV cross section, while in group B, MLC moves alone the longer dimension. 50.0 Gy is normalized to 95% of PTV in all plans. Results:Dose for the organ at risk (OAR) was shown reduction in both groups, when the independent jaw blocks more open field. The mean dose reduction was 15.9% and 18.9% respectively when the jaw moved from +2 cm to 0 cm (half beam blocked. More significant improvement (> 27%) in dose sparing was indicated with the jaw set further into the field. No consistent trend of changes in dose homogeneities was found, except when the jaw partially blocked the PTV. In the final clinic case, more than 90% of PTV received the prescribed 45Gy dose with about 19% meaningful dose heterogeneity (effective 50Gy for majority of treated areas), and satisfactory dose conformity. Treatments were comfortably fitted in 15‐minute daily schedule. The treatment resulted in an excellent clinical outcome without cosmetic complications seen during the first 12 month follow‐ups. Conclusion: This study demonstrates the feasibility of the application of LINAC based individualized IMRT for an Elliptic Paraboloid‐shaped superficial target. Further clinical trials will be designed for the treatment of chest malignancy.

Charles Shang - One of the best experts on this subject based on the ideXlab platform.

  • SU‐GG‐T‐77: Application and Dosimetric Analysis of Multiple Static Tangential Intensity‐Modulated Radiotherapy Beams in An Elliptic Paraboloid‐Shaped Superficial Tumor
    Medical Physics, 2008
    Co-Authors: Charles Shang, T Williams, R Girouard, A Schramm
    Abstract:

    Purpose is to evaluate dosimetric efficacy for LINAC‐based IMRT for an Elliptic Paraboloid‐shaped shallow target. Method and Materials: This study includes a case with advanced facial multi‐focal basal cell carcinoma. The lesion variably extended entire face, up to 3.5 cm deep. A simulation target was created in a cylindrical water phantom for evaluating different plans. All IMRT plans comprised of eleven coplanar 6‐MV photon beams with 5mm sMLC. Only outer portion of each beam opens to the PTV. Identical beam constraints with 4mm MLC stepping were used. In group A, the MLC travels along the shorter dimension of PTV cross section, while in group B, MLC moves alone the longer dimension. 50.0 Gy is normalized to 95% of PTV in all plans. Results:Dose for the organ at risk (OAR) was shown reduction in both groups, when the independent jaw blocks more open field. The mean dose reduction was 15.9% and 18.9% respectively when the jaw moved from +2 cm to 0 cm (half beam blocked. More significant improvement (> 27%) in dose sparing was indicated with the jaw set further into the field. No consistent trend of changes in dose homogeneities was found, except when the jaw partially blocked the PTV. In the final clinic case, more than 90% of PTV received the prescribed 45Gy dose with about 19% meaningful dose heterogeneity (effective 50Gy for majority of treated areas), and satisfactory dose conformity. Treatments were comfortably fitted in 15‐minute daily schedule. The treatment resulted in an excellent clinical outcome without cosmetic complications seen during the first 12 month follow‐ups. Conclusion: This study demonstrates the feasibility of the application of LINAC based individualized IMRT for an Elliptic Paraboloid‐shaped superficial target. Further clinical trials will be designed for the treatment of chest malignancy.

  • su gg t 77 application and dosimetric analysis of multiple static tangential intensity modulated radiotherapy beams in an Elliptic Paraboloid shaped superficial tumor
    Medical Physics, 2008
    Co-Authors: Charles Shang, T Williams, R Girouard, A Schramm
    Abstract:

    Purpose is to evaluate dosimetric efficacy for LINAC‐based IMRT for an Elliptic Paraboloid‐shaped shallow target. Method and Materials: This study includes a case with advanced facial multi‐focal basal cell carcinoma. The lesion variably extended entire face, up to 3.5 cm deep. A simulation target was created in a cylindrical water phantom for evaluating different plans. All IMRT plans comprised of eleven coplanar 6‐MV photon beams with 5mm sMLC. Only outer portion of each beam opens to the PTV. Identical beam constraints with 4mm MLC stepping were used. In group A, the MLC travels along the shorter dimension of PTV cross section, while in group B, MLC moves alone the longer dimension. 50.0 Gy is normalized to 95% of PTV in all plans. Results:Dose for the organ at risk (OAR) was shown reduction in both groups, when the independent jaw blocks more open field. The mean dose reduction was 15.9% and 18.9% respectively when the jaw moved from +2 cm to 0 cm (half beam blocked. More significant improvement (> 27%) in dose sparing was indicated with the jaw set further into the field. No consistent trend of changes in dose homogeneities was found, except when the jaw partially blocked the PTV. In the final clinic case, more than 90% of PTV received the prescribed 45Gy dose with about 19% meaningful dose heterogeneity (effective 50Gy for majority of treated areas), and satisfactory dose conformity. Treatments were comfortably fitted in 15‐minute daily schedule. The treatment resulted in an excellent clinical outcome without cosmetic complications seen during the first 12 month follow‐ups. Conclusion: This study demonstrates the feasibility of the application of LINAC based individualized IMRT for an Elliptic Paraboloid‐shaped superficial target. Further clinical trials will be designed for the treatment of chest malignancy.

T Williams - One of the best experts on this subject based on the ideXlab platform.

  • SU‐GG‐T‐77: Application and Dosimetric Analysis of Multiple Static Tangential Intensity‐Modulated Radiotherapy Beams in An Elliptic Paraboloid‐Shaped Superficial Tumor
    Medical Physics, 2008
    Co-Authors: Charles Shang, T Williams, R Girouard, A Schramm
    Abstract:

    Purpose is to evaluate dosimetric efficacy for LINAC‐based IMRT for an Elliptic Paraboloid‐shaped shallow target. Method and Materials: This study includes a case with advanced facial multi‐focal basal cell carcinoma. The lesion variably extended entire face, up to 3.5 cm deep. A simulation target was created in a cylindrical water phantom for evaluating different plans. All IMRT plans comprised of eleven coplanar 6‐MV photon beams with 5mm sMLC. Only outer portion of each beam opens to the PTV. Identical beam constraints with 4mm MLC stepping were used. In group A, the MLC travels along the shorter dimension of PTV cross section, while in group B, MLC moves alone the longer dimension. 50.0 Gy is normalized to 95% of PTV in all plans. Results:Dose for the organ at risk (OAR) was shown reduction in both groups, when the independent jaw blocks more open field. The mean dose reduction was 15.9% and 18.9% respectively when the jaw moved from +2 cm to 0 cm (half beam blocked. More significant improvement (> 27%) in dose sparing was indicated with the jaw set further into the field. No consistent trend of changes in dose homogeneities was found, except when the jaw partially blocked the PTV. In the final clinic case, more than 90% of PTV received the prescribed 45Gy dose with about 19% meaningful dose heterogeneity (effective 50Gy for majority of treated areas), and satisfactory dose conformity. Treatments were comfortably fitted in 15‐minute daily schedule. The treatment resulted in an excellent clinical outcome without cosmetic complications seen during the first 12 month follow‐ups. Conclusion: This study demonstrates the feasibility of the application of LINAC based individualized IMRT for an Elliptic Paraboloid‐shaped superficial target. Further clinical trials will be designed for the treatment of chest malignancy.

  • su gg t 77 application and dosimetric analysis of multiple static tangential intensity modulated radiotherapy beams in an Elliptic Paraboloid shaped superficial tumor
    Medical Physics, 2008
    Co-Authors: Charles Shang, T Williams, R Girouard, A Schramm
    Abstract:

    Purpose is to evaluate dosimetric efficacy for LINAC‐based IMRT for an Elliptic Paraboloid‐shaped shallow target. Method and Materials: This study includes a case with advanced facial multi‐focal basal cell carcinoma. The lesion variably extended entire face, up to 3.5 cm deep. A simulation target was created in a cylindrical water phantom for evaluating different plans. All IMRT plans comprised of eleven coplanar 6‐MV photon beams with 5mm sMLC. Only outer portion of each beam opens to the PTV. Identical beam constraints with 4mm MLC stepping were used. In group A, the MLC travels along the shorter dimension of PTV cross section, while in group B, MLC moves alone the longer dimension. 50.0 Gy is normalized to 95% of PTV in all plans. Results:Dose for the organ at risk (OAR) was shown reduction in both groups, when the independent jaw blocks more open field. The mean dose reduction was 15.9% and 18.9% respectively when the jaw moved from +2 cm to 0 cm (half beam blocked. More significant improvement (> 27%) in dose sparing was indicated with the jaw set further into the field. No consistent trend of changes in dose homogeneities was found, except when the jaw partially blocked the PTV. In the final clinic case, more than 90% of PTV received the prescribed 45Gy dose with about 19% meaningful dose heterogeneity (effective 50Gy for majority of treated areas), and satisfactory dose conformity. Treatments were comfortably fitted in 15‐minute daily schedule. The treatment resulted in an excellent clinical outcome without cosmetic complications seen during the first 12 month follow‐ups. Conclusion: This study demonstrates the feasibility of the application of LINAC based individualized IMRT for an Elliptic Paraboloid‐shaped superficial target. Further clinical trials will be designed for the treatment of chest malignancy.

R Girouard - One of the best experts on this subject based on the ideXlab platform.

  • SU‐GG‐T‐77: Application and Dosimetric Analysis of Multiple Static Tangential Intensity‐Modulated Radiotherapy Beams in An Elliptic Paraboloid‐Shaped Superficial Tumor
    Medical Physics, 2008
    Co-Authors: Charles Shang, T Williams, R Girouard, A Schramm
    Abstract:

    Purpose is to evaluate dosimetric efficacy for LINAC‐based IMRT for an Elliptic Paraboloid‐shaped shallow target. Method and Materials: This study includes a case with advanced facial multi‐focal basal cell carcinoma. The lesion variably extended entire face, up to 3.5 cm deep. A simulation target was created in a cylindrical water phantom for evaluating different plans. All IMRT plans comprised of eleven coplanar 6‐MV photon beams with 5mm sMLC. Only outer portion of each beam opens to the PTV. Identical beam constraints with 4mm MLC stepping were used. In group A, the MLC travels along the shorter dimension of PTV cross section, while in group B, MLC moves alone the longer dimension. 50.0 Gy is normalized to 95% of PTV in all plans. Results:Dose for the organ at risk (OAR) was shown reduction in both groups, when the independent jaw blocks more open field. The mean dose reduction was 15.9% and 18.9% respectively when the jaw moved from +2 cm to 0 cm (half beam blocked. More significant improvement (> 27%) in dose sparing was indicated with the jaw set further into the field. No consistent trend of changes in dose homogeneities was found, except when the jaw partially blocked the PTV. In the final clinic case, more than 90% of PTV received the prescribed 45Gy dose with about 19% meaningful dose heterogeneity (effective 50Gy for majority of treated areas), and satisfactory dose conformity. Treatments were comfortably fitted in 15‐minute daily schedule. The treatment resulted in an excellent clinical outcome without cosmetic complications seen during the first 12 month follow‐ups. Conclusion: This study demonstrates the feasibility of the application of LINAC based individualized IMRT for an Elliptic Paraboloid‐shaped superficial target. Further clinical trials will be designed for the treatment of chest malignancy.

  • su gg t 77 application and dosimetric analysis of multiple static tangential intensity modulated radiotherapy beams in an Elliptic Paraboloid shaped superficial tumor
    Medical Physics, 2008
    Co-Authors: Charles Shang, T Williams, R Girouard, A Schramm
    Abstract:

    Purpose is to evaluate dosimetric efficacy for LINAC‐based IMRT for an Elliptic Paraboloid‐shaped shallow target. Method and Materials: This study includes a case with advanced facial multi‐focal basal cell carcinoma. The lesion variably extended entire face, up to 3.5 cm deep. A simulation target was created in a cylindrical water phantom for evaluating different plans. All IMRT plans comprised of eleven coplanar 6‐MV photon beams with 5mm sMLC. Only outer portion of each beam opens to the PTV. Identical beam constraints with 4mm MLC stepping were used. In group A, the MLC travels along the shorter dimension of PTV cross section, while in group B, MLC moves alone the longer dimension. 50.0 Gy is normalized to 95% of PTV in all plans. Results:Dose for the organ at risk (OAR) was shown reduction in both groups, when the independent jaw blocks more open field. The mean dose reduction was 15.9% and 18.9% respectively when the jaw moved from +2 cm to 0 cm (half beam blocked. More significant improvement (> 27%) in dose sparing was indicated with the jaw set further into the field. No consistent trend of changes in dose homogeneities was found, except when the jaw partially blocked the PTV. In the final clinic case, more than 90% of PTV received the prescribed 45Gy dose with about 19% meaningful dose heterogeneity (effective 50Gy for majority of treated areas), and satisfactory dose conformity. Treatments were comfortably fitted in 15‐minute daily schedule. The treatment resulted in an excellent clinical outcome without cosmetic complications seen during the first 12 month follow‐ups. Conclusion: This study demonstrates the feasibility of the application of LINAC based individualized IMRT for an Elliptic Paraboloid‐shaped superficial target. Further clinical trials will be designed for the treatment of chest malignancy.

Pericles S. Theocaris - One of the best experts on this subject based on the ideXlab platform.

  • 1. A CONCISE REVIEW OF FAILURE CRITERIA BASED ON TENSOR POLYNOMIALS
    2016
    Co-Authors: Pericles S. Theocaris
    Abstract:

    ABSTRACT: Several interesting versions of the tensor polynomial failure criterion for composites were compared with the family of the Elliptic Paraboloid failure criteria (EPFS), with symmetry axes parallel to the hydrostatic axis. A critical appraisal of the most important theories was presented and a comparison was made with existing experi-mental data in triaxial stress states. The superiority of the EPFS over any other criterion was established. Furthermore, the more flexible ellipsoid failure surface criterion, an ex-tension of EPFS, may be used for special types of material such as foams, porous material and other materials that fail under internal buckling in general compression

  • The Variation of the Elliptic Paraboloid Failure Locus Beyond the Elastic Limit
    International Journal of Damage Mechanics, 1996
    Co-Authors: Pericles S. Theocaris
    Abstract:

    A method is presented by defining an isotropic hardening plasticity through an appropriate sequence of an isotropic problems. Assuming a stepwise form of loading or unloading, we measure the instantaneous tension and compression yield stresses along the transient principal-stress directions. These parameters completely define the instantaneous state of anisotropy of the body for the corresponding loading step, by applying the theory of Elliptic Paraboloid failure locus (EPFS). The parameter identification problem is formulated on the constitutive expressions for this most general failure criterion, and by applying convenient constraints derived from the EPFS theory, which are serving as filters throughout the whole procedure of evaluating the characteristic values of terms defining the variable components of the failure tensor polynomial, as the material is continuously loaded from the elastic into the plastic region and up to the ultimate failure load.Accurate simple tests in uniaxial tension and compres...

  • Failure modes of closed-cell polyurethane foams
    International Journal of Fracture, 1992
    Co-Authors: Pericles S. Theocaris
    Abstract:

    The failure modes of closed-cell polyurethane foams were studied by applying the Elliptic Paraboloid failure surface criterion. A series of three polyurethane rigid foams (PUR-foams) were examined presenting different amounts of porosity from a highly porous material having a low density of 64 kg/m^3 to a compact one with a density of 192 kg/m^3. All these PUR-foams were of the same batch of material presenting a cell-wall density ϱ_5=1200 kg/m^3. Samples were tested in simple tension and compression along the three principal axes of anisotropy of the materials. It was shown that all three types of foams may be closely represented by transversely isotropic materials. The Elliptic Paraboloid failure surfaces (EPFS) for these three materials were defined from the six values of principal failure stresses in tension and compression. It was shown that the theoretically plotted Paraboloid surfaces along all their principal-plane intersections were in good agreement with experiments. Since cellular materials collapse, either under elastic buckling in the compressive octant of the principal stress space, or under fast brittle fracture in the tensile octant, it was shown that the Elliptic Paraboloid failure surface is truncated by the intersection of the EPFS and an ellipsoid whose position and dimensions are interrelated with those of the EPFS. Again, experimental evidence with elastic buckling of foams corroborated the results of this theory. An important feature for the failure behavior of the foams was derived by this study according to which the foamed materials change mode of failure from a compression strong to a tension strong mode as their porosity is increased. In between they pass through a quasi-isotropic state.

  • Weighing Failure Tensor Polynomial Criteria for Composites
    International Journal of Damage Mechanics, 1992
    Co-Authors: Pericles S. Theocaris
    Abstract:

    Several interesting versions of the tensor polynomial failure criterion for composites were compared with the family of the Elliptic Paraboloid failure criteria (EPFS), with symmetry axes parallel to the hydrostatic axis. A critical appraisal of the most important theories was presented and a comparison was made with existing experi- mental data in triaxial stress states. The superiority of the EPFS over any other criterion was established. Furthermore, the more flexible ellipsoid failure surface criterion, an ex- tension of EPFS, may be used for special types of material such as foams, porous material and other materials that fail under internal buckling in general compression.

  • Positive and negative failure-shears in orthotropic materials
    Journal of Reinforced Plastics and Composites, 1992
    Co-Authors: Pericles S. Theocaris
    Abstract:

    Failure predictions of off-axis loaded fiber composite laminae are given according to the Elliptic Paraboloid failure criterion for anisotropic solids [1]. The failure condition assumes that for any anisotropic solid a safe triaxial loading path exists, along the hydrostatic compression, and thus the failure surface must be open-ended. By appropriately formulating the failure criterion, it is shown that the geometric interpretation of the failure surface in the principal stress space is an Elliptic Paraboloid (EPFS) whose axis of symmetry is parallel to the hydrostatic axis in the principal stress space. Because of the shape and position of the EPFS, the intersections by principal stress planes corresponding to loadings of off-axis laminae of a fiber composite are represented by ellipses whose origins are displaced from the origin of the stress reference frame. This fact creates unequal shear yield stresses in the positive and negative sense clearly manifested in a pure shear failure loading.The predictio...