The Experts below are selected from a list of 93 Experts worldwide ranked by ideXlab platform

Carsten Herskind - One of the best experts on this subject based on the ideXlab platform.

  • Relative Biologic Effectiveness rbe of 50 kv x rays measured in a phantom for intraoperative tumor bed irradiation
    International Journal of Radiation Oncology Biology Physics, 2013
    Co-Authors: Qi Liu, Frank Schneider, Frederik Wenz, Carsten Herskind
    Abstract:

    Purpose Intraoperative radiation therapy (IORT) with low-energy x-rays is used to treat the tumor bed during breast-conserving surgery. The purpose was to determine the Relative Biologic Effectiveness (RBE) of 50-kV x-rays for inactivation of cells irradiated in a tumor-bed phantom. Methods and Materials The RBE was determined for clonogenic inactivation of human tumor and normal cells (MCF7, human umbilical vein endothelial cells, normal skin fibroblasts), and hamster V79 cells. The 50-kV x-rays from the Intrabeam machine (Carl Zeiss Surgical) with a spherical 4-cm applicator were used. Cells were irradiated in a water-equivalent phantom at defined distances (8.1-22.9 mm) from the applicator surface. The 50-kV x-rays from a surface therapy machine (Dermopan, Siemens) were included for comparison; 6-MV x-rays were used as reference radiation. Results At 8.1-mm depth in the phantom (dose rate 15.1 Gy/h), mean RBE values of 50-kV x-rays from Intrabeam were 1.26 to 1.42 for the 4 cell types at doses yielding surviving fractions in the range of 0.01 to 0.5. Confidence intervals were in the range of 1.2 and 1.5. Similar RBE values were found for 50-kV x-rays from Dermopan for V79 (1.30, CI 1.25-1.36, P =.74) and GS4 (1.42, CI 1.30-1.54, P =.67). No significant dependence of RBE on dose was found for Intrabeam, but RBE decreased at a larger distance (12.7 mm; 9.8 Gy/h). Conclusions An increased clinically relevant RBE was found for cell irradiation with Intrabeam at depths in the tumor bed targeted by IORT. The reduced RBE values at larger distances may be related to increased repair of sublethal damage during protracted irradiation or to hardening of the photon beam energy.

  • Relative Biologic Effectiveness rbe of 50 kv x rays measured in a phantom for intraoperative tumor bed
    2013
    Co-Authors: Qi Liu, Frank Schneider, Frederik Wenz, Carsten Herskind
    Abstract:

    Summary IORTwith low-energy x-rays differs from conventional radiation therapy with respect to photon energy and dose rate, both of which influence the RBE. This experimental study determined RBE of 50-kV x-rays for inactivation of cells under conditions simulating tumorbed irradiation. The RBE was found to be increased Relative to 6-MV x-rays and was influenced by depth in the tumor-bed phantom, whereas no significant variation with dose was observed. Purpose: Intraoperative radiation therapy (IORT) with low-energy x-rays is used to treat the tumor bed during breast-conserving surgery. The purpose was to determine the Relative Biologic Effectiveness (RBE) of 50-kV x-rays for inactivation of cells irradiated in a tumor-bed phantom. Methods and Materials: The RBE was determined for clonogenic inactivation of human tumor and normal cells (MCF7, human umbilical vein endothelial cells, normal skin fibroblasts), and hamster V79 cells. The 50-kV x-rays from the Intrabeam machine (Carl Zeiss Surgical) with a spherical 4-cm applicator were used. Cells were irradiated in a water-equivalent phantom at defined distances (8.1-22.9 mm) from the applicator surface. The 50-kV x-rays from a surface therapy machine (Dermopan, Siemens) were included for comparison; 6-MV x-rays were used as reference radiation. Results: At 8.1-mm depth in the phantom (dose rate 15.1 Gy/h), mean RBE values of 50-kV xrays from Intrabeam were 1.26 to 1.42 for the 4 cell types at doses yielding surviving fractions in the range of 0.01 to 0.5. Confidence intervals were in the range of 1.2 and 1.5. Similar RBE values were found for 50-kV x-rays from Dermopan for V79 (1.30, CI 1.25-1.36, PZ.74) and GS4 (1.42, CI 1.30-1.54, PZ.67). No significant dependence of RBE on dose was found for Intrabeam, but RBE decreased at a larger distance (12.7 mm; 9.8 Gy/h). Conclusions: An increased clinically relevant RBE was found for cell irradiation with Intrabeam at depths in the tumor bed targeted by IORT. The reduced RBE values at larger distances may be related to increased repair of sublethal damage during protracted irradiation or to hardening of the photon beam energy. 2013 Elsevier Inc.

  • sphere of equivalence a novel target volume concept for intraoperative radiotherapy using low energy x rays
    International Journal of Radiation Oncology Biology Physics, 2008
    Co-Authors: Carsten Herskind, J Griebel, U Kraustiefenbacher, Frederik Wenz
    Abstract:

    Purpose Accelerated partial breast radiotherapy with low-energy photons from a miniature X-ray machine is undergoing a randomized clinical trial (Targeted Intra-operative Radiation Therapy [TARGIT]) in a selected subgroup of patients treated with breast-conserving surgery. The steep radial dose gradient implies reduced tumor cell control with increasing depth in the tumor bed. The purpose was to compare the expected risk of local recurrence in this nonuniform radiation field with that after conventional external beam radiotherapy. Methods and Materials The Relative Biologic Effectiveness of low-energy photons was modeled using the linear-quadratic formalism including repair of sublethal lesions during protracted irradiation. Doses of 50-kV X-rays (Intrabeam) were converted to equivalent fractionated doses, EQD2, as function of depth in the tumor bed. The probability of local control was estimated using a logistic dose–response relationship fitted to clinical data from fractionated radiotherapy. Results The model calculations show that, for a cohort of patients, the increase in local control in the high-dose region near the applicator partly compensates the reduction of local control at greater distances. Thus a "sphere of equivalence" exists within which the risk of recurrence is equal to that after external fractionated radiotherapy. The spatial distribution of recurrences inside this sphere will be different from that after conventional radiotherapy. Conclusions A novel target volume concept is presented here. The incidence of recurrences arising in the tumor bed around the excised tumor will test the validity of this concept and the efficacy of the treatment. Recurrences elsewhere will have implications for the rationale of TARGIT.

Yoshiya Shimada - One of the best experts on this subject based on the ideXlab platform.

  • high Relative Biologic Effectiveness of carbon ion radiation on induction of rat mammary carcinoma and its lack of h ras and tp53 mutations
    International Journal of Radiation Oncology Biology Physics, 2007
    Co-Authors: Tatsuhiko Imaoka, Mayumi Nishimura, Shizuko Kakinuma, Yukiko Hatano, Yasushi Ohmachi, Shinji Yoshinaga, Akihiro Kawano, Akihiko Maekawa, Yoshiya Shimada
    Abstract:

    Purpose The high Relative Biologic Effectiveness (RBE) of high-linear energy transfer (LET) heavy-ion radiation has enabled powerful radiotherapy. The potential risk of later onset of secondary cancers, however, has not been adequately studied. We undertook the present study to clarify the RBE of therapeutic carbon ion radiation and molecular changes that occur in the rat mammary cancer model. Methods and Materials We observed 7–8-week-old rats (ACI, F344, Wistar, and Sprague-Dawley) until 1 year of age after irradiation (0.05–2 Gy) with either 290 MeV/u carbon ions with a spread out Bragg peak (LET 40–90 keV/μm) generated from the Heavy-Ion Medical Accelerator in Chiba or 137 Cs γ-rays. Results Carbon ions significantly induced mammary carcinomas in Sprague-Dawley rats but less so in other strains. The dose–effect relationship for carcinoma incidence in the Sprague-Dawley rats was concave downward, providing an RBE of 2 at a typical therapeutic dose per fraction. In contrast, ∼10 should be considered for radiation protection at low doses. Immunohistochemically, 14 of 18 carcinomas were positive for estrogen receptor α. All carcinomas examined were free of common H- ras and Tp53 mutations. Importantly, lung metastasis (7%) was characteristic of carbon ion–irradiated rats. Conclusions We found clear genetic variability in the susceptibility to carbon ion–induced mammary carcinomas. The high RBE for carbon ion radiation further supports the importance of precise dose localization in radiotherapy. Common point mutations in H- ras and Tp53 were not involved in carbon ion induction of rat mammary carcinomas.

Frederik Wenz - One of the best experts on this subject based on the ideXlab platform.

  • Relative Biologic Effectiveness rbe of 50 kv x rays measured in a phantom for intraoperative tumor bed irradiation
    International Journal of Radiation Oncology Biology Physics, 2013
    Co-Authors: Qi Liu, Frank Schneider, Frederik Wenz, Carsten Herskind
    Abstract:

    Purpose Intraoperative radiation therapy (IORT) with low-energy x-rays is used to treat the tumor bed during breast-conserving surgery. The purpose was to determine the Relative Biologic Effectiveness (RBE) of 50-kV x-rays for inactivation of cells irradiated in a tumor-bed phantom. Methods and Materials The RBE was determined for clonogenic inactivation of human tumor and normal cells (MCF7, human umbilical vein endothelial cells, normal skin fibroblasts), and hamster V79 cells. The 50-kV x-rays from the Intrabeam machine (Carl Zeiss Surgical) with a spherical 4-cm applicator were used. Cells were irradiated in a water-equivalent phantom at defined distances (8.1-22.9 mm) from the applicator surface. The 50-kV x-rays from a surface therapy machine (Dermopan, Siemens) were included for comparison; 6-MV x-rays were used as reference radiation. Results At 8.1-mm depth in the phantom (dose rate 15.1 Gy/h), mean RBE values of 50-kV x-rays from Intrabeam were 1.26 to 1.42 for the 4 cell types at doses yielding surviving fractions in the range of 0.01 to 0.5. Confidence intervals were in the range of 1.2 and 1.5. Similar RBE values were found for 50-kV x-rays from Dermopan for V79 (1.30, CI 1.25-1.36, P =.74) and GS4 (1.42, CI 1.30-1.54, P =.67). No significant dependence of RBE on dose was found for Intrabeam, but RBE decreased at a larger distance (12.7 mm; 9.8 Gy/h). Conclusions An increased clinically relevant RBE was found for cell irradiation with Intrabeam at depths in the tumor bed targeted by IORT. The reduced RBE values at larger distances may be related to increased repair of sublethal damage during protracted irradiation or to hardening of the photon beam energy.

  • Relative Biologic Effectiveness rbe of 50 kv x rays measured in a phantom for intraoperative tumor bed
    2013
    Co-Authors: Qi Liu, Frank Schneider, Frederik Wenz, Carsten Herskind
    Abstract:

    Summary IORTwith low-energy x-rays differs from conventional radiation therapy with respect to photon energy and dose rate, both of which influence the RBE. This experimental study determined RBE of 50-kV x-rays for inactivation of cells under conditions simulating tumorbed irradiation. The RBE was found to be increased Relative to 6-MV x-rays and was influenced by depth in the tumor-bed phantom, whereas no significant variation with dose was observed. Purpose: Intraoperative radiation therapy (IORT) with low-energy x-rays is used to treat the tumor bed during breast-conserving surgery. The purpose was to determine the Relative Biologic Effectiveness (RBE) of 50-kV x-rays for inactivation of cells irradiated in a tumor-bed phantom. Methods and Materials: The RBE was determined for clonogenic inactivation of human tumor and normal cells (MCF7, human umbilical vein endothelial cells, normal skin fibroblasts), and hamster V79 cells. The 50-kV x-rays from the Intrabeam machine (Carl Zeiss Surgical) with a spherical 4-cm applicator were used. Cells were irradiated in a water-equivalent phantom at defined distances (8.1-22.9 mm) from the applicator surface. The 50-kV x-rays from a surface therapy machine (Dermopan, Siemens) were included for comparison; 6-MV x-rays were used as reference radiation. Results: At 8.1-mm depth in the phantom (dose rate 15.1 Gy/h), mean RBE values of 50-kV xrays from Intrabeam were 1.26 to 1.42 for the 4 cell types at doses yielding surviving fractions in the range of 0.01 to 0.5. Confidence intervals were in the range of 1.2 and 1.5. Similar RBE values were found for 50-kV x-rays from Dermopan for V79 (1.30, CI 1.25-1.36, PZ.74) and GS4 (1.42, CI 1.30-1.54, PZ.67). No significant dependence of RBE on dose was found for Intrabeam, but RBE decreased at a larger distance (12.7 mm; 9.8 Gy/h). Conclusions: An increased clinically relevant RBE was found for cell irradiation with Intrabeam at depths in the tumor bed targeted by IORT. The reduced RBE values at larger distances may be related to increased repair of sublethal damage during protracted irradiation or to hardening of the photon beam energy. 2013 Elsevier Inc.

  • sphere of equivalence a novel target volume concept for intraoperative radiotherapy using low energy x rays
    International Journal of Radiation Oncology Biology Physics, 2008
    Co-Authors: Carsten Herskind, J Griebel, U Kraustiefenbacher, Frederik Wenz
    Abstract:

    Purpose Accelerated partial breast radiotherapy with low-energy photons from a miniature X-ray machine is undergoing a randomized clinical trial (Targeted Intra-operative Radiation Therapy [TARGIT]) in a selected subgroup of patients treated with breast-conserving surgery. The steep radial dose gradient implies reduced tumor cell control with increasing depth in the tumor bed. The purpose was to compare the expected risk of local recurrence in this nonuniform radiation field with that after conventional external beam radiotherapy. Methods and Materials The Relative Biologic Effectiveness of low-energy photons was modeled using the linear-quadratic formalism including repair of sublethal lesions during protracted irradiation. Doses of 50-kV X-rays (Intrabeam) were converted to equivalent fractionated doses, EQD2, as function of depth in the tumor bed. The probability of local control was estimated using a logistic dose–response relationship fitted to clinical data from fractionated radiotherapy. Results The model calculations show that, for a cohort of patients, the increase in local control in the high-dose region near the applicator partly compensates the reduction of local control at greater distances. Thus a "sphere of equivalence" exists within which the risk of recurrence is equal to that after external fractionated radiotherapy. The spatial distribution of recurrences inside this sphere will be different from that after conventional radiotherapy. Conclusions A novel target volume concept is presented here. The incidence of recurrences arising in the tumor bed around the excised tumor will test the validity of this concept and the efficacy of the treatment. Recurrences elsewhere will have implications for the rationale of TARGIT.

Akihiro Kawano - One of the best experts on this subject based on the ideXlab platform.

  • high Relative Biologic Effectiveness of carbon ion radiation on induction of rat mammary carcinoma and its lack of h ras and tp53 mutations
    International Journal of Radiation Oncology Biology Physics, 2007
    Co-Authors: Tatsuhiko Imaoka, Mayumi Nishimura, Shizuko Kakinuma, Yukiko Hatano, Yasushi Ohmachi, Shinji Yoshinaga, Akihiro Kawano, Akihiko Maekawa, Yoshiya Shimada
    Abstract:

    Purpose The high Relative Biologic Effectiveness (RBE) of high-linear energy transfer (LET) heavy-ion radiation has enabled powerful radiotherapy. The potential risk of later onset of secondary cancers, however, has not been adequately studied. We undertook the present study to clarify the RBE of therapeutic carbon ion radiation and molecular changes that occur in the rat mammary cancer model. Methods and Materials We observed 7–8-week-old rats (ACI, F344, Wistar, and Sprague-Dawley) until 1 year of age after irradiation (0.05–2 Gy) with either 290 MeV/u carbon ions with a spread out Bragg peak (LET 40–90 keV/μm) generated from the Heavy-Ion Medical Accelerator in Chiba or 137 Cs γ-rays. Results Carbon ions significantly induced mammary carcinomas in Sprague-Dawley rats but less so in other strains. The dose–effect relationship for carcinoma incidence in the Sprague-Dawley rats was concave downward, providing an RBE of 2 at a typical therapeutic dose per fraction. In contrast, ∼10 should be considered for radiation protection at low doses. Immunohistochemically, 14 of 18 carcinomas were positive for estrogen receptor α. All carcinomas examined were free of common H- ras and Tp53 mutations. Importantly, lung metastasis (7%) was characteristic of carbon ion–irradiated rats. Conclusions We found clear genetic variability in the susceptibility to carbon ion–induced mammary carcinomas. The high RBE for carbon ion radiation further supports the importance of precise dose localization in radiotherapy. Common point mutations in H- ras and Tp53 were not involved in carbon ion induction of rat mammary carcinomas.

Iuliana Tomadasu - One of the best experts on this subject based on the ideXlab platform.