The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform
Zvi Fuks - One of the best experts on this subject based on the ideXlab platform.
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the effect of setup uncertainties on the treatment of Nasopharynx cancer
International Journal of Radiation Oncology Biology Physics, 1993Co-Authors: Margie Hunt, Gerald J Kutcher, Chloe Burman, Daniel E Fass, Louis B Harrison, Steven A Leibel, Zvi FuksAbstract:Abstract Purpose: As radiation treatment techniques become more complicated, the need to understand the effect of uncertainties on dose distributions increases. This study investigates the effect of positional uncertainities for patients with Nasopharynx Carcinoma treated with a multiple field conformal boost technique. Three dimensional setup errors were measured for six patients and the effect on patient dose was evaluated using dose volume histograms. Methods and Materials: A method is presented for determining 3-dimensional translational and rotational setup errors by identifying anatomical landmarks on two treatment field images and their corresponding simulation images. Measurements were made on a daily basis for six patients undergoing conformal treatment. Results: The average magnitude of the tmnsiational errors was between 1.5 and 3 mm while the average distance between simulation and treatment isocenters was 5 mm. Both systematic and random setup errors were observed. Dose volume histograms incorporating these uncertainties for standard parallel opposed and conformal techniques were generated for patients experiencing random and systematic setup errors. Conclusion: The data imply that positional uncertainties effect the daily dose distributions for target and critical structures differently and that the effect may be treatment technique dependent. These results demonstrate the need to measure setup uncertainties for all sites and to develop techniques for incorporating dose uncertainties in treatment plans.
Margie Hunt - One of the best experts on this subject based on the ideXlab platform.
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sensorineural hearing loss in combined modality treatment of nasopharyngeal Carcinoma
Cancer, 2006Co-Authors: W C Chen, Margie Hunt, Andrew Jackson, Amy Budnick, David G Pfister, Dennis H Kraus, Hilda E Stambuk, Sabine Levegrun, Suzanne L WoldenAbstract:BACKGROUND Combined modality therapy has become the standard of care for nasopharyngeal Carcinoma, yet the combined ototoxic effects of radiation and cisplatin are poorly understood. The incidence and severity of sensorineural hearing loss (SNHL) with combined modality therapy was evaluated and the dose–response relation between radiation and hearing loss was investigated. METHODS Patients with newly diagnosed AJCC Stage II–IVB Nasopharynx Carcinoma treated from 1994–2003 were identified. The records of 44 ears in 22 patients who received a preirradiation pure tone audiogram and followup audiograms 12+ months postirradiation were included in the analysis. All patients were treated with conformal radiotherapy to 70 Gy and received platinum-based chemotherapy similar to the Intergroup 0099 trial. Composite cochlear dose distributions were calculated. Ototoxicity was measured using intrasubject audiogram comparisons and SNHL was defined as per the American Speech and Hearing Association guidelines, with standard range of speech between 2000–4000 Hz. SNHL was analyzed using Fisher exact test and linear and logistic regression models. RESULTS Patient characteristics: median age, 45; 27% Asian; 68% male; 64% WHO III. Median audiologic followup was 29 months (range, 12–76 mos). Mean cochlear dose (Dmean) ranged from 28.4–70.0 Gy (median, 48.5 Gy). SNHL was detected in 25 of the 44 ears (57%) studied. There was an increased risk of SNHL for ears receiving Dmean > 48 Gy compared with those receiving ≤ 48 Gy at all frequencies within the range of speech (P = 0.04). Using univariate logistic regression analysis, Dmean to the cochlea, cycles of cisplatin, and time postradiotherapy were independently significant factors in determining the incidence of SNHL (P = 0.02, P = 0.03, and P = 0.04, respectively). In univariate and multivariate linear regression analysis, Dmean was statistically significant at all frequencies in affecting degree of SNHL, whereas the significance of cisplatin and time was variable. CONCLUSIONS There was a significant increase in risk of SNHL among patients receiving > 48 Gy, suggesting a threshold in cochlear radiation dose–response in the setting of combined modality therapy. This dose should serve as a Dmean constraint maximum for intensity-modulated radiotherapy treatment of Nasopharynx Carcinoma. Cancer 2006. © 2006 American Cancer Society.
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the effect of setup uncertainties on the treatment of Nasopharynx cancer
International Journal of Radiation Oncology Biology Physics, 1993Co-Authors: Margie Hunt, Gerald J Kutcher, Chloe Burman, Daniel E Fass, Louis B Harrison, Steven A Leibel, Zvi FuksAbstract:Abstract Purpose: As radiation treatment techniques become more complicated, the need to understand the effect of uncertainties on dose distributions increases. This study investigates the effect of positional uncertainities for patients with Nasopharynx Carcinoma treated with a multiple field conformal boost technique. Three dimensional setup errors were measured for six patients and the effect on patient dose was evaluated using dose volume histograms. Methods and Materials: A method is presented for determining 3-dimensional translational and rotational setup errors by identifying anatomical landmarks on two treatment field images and their corresponding simulation images. Measurements were made on a daily basis for six patients undergoing conformal treatment. Results: The average magnitude of the tmnsiational errors was between 1.5 and 3 mm while the average distance between simulation and treatment isocenters was 5 mm. Both systematic and random setup errors were observed. Dose volume histograms incorporating these uncertainties for standard parallel opposed and conformal techniques were generated for patients experiencing random and systematic setup errors. Conclusion: The data imply that positional uncertainties effect the daily dose distributions for target and critical structures differently and that the effect may be treatment technique dependent. These results demonstrate the need to measure setup uncertainties for all sites and to develop techniques for incorporating dose uncertainties in treatment plans.
E J Land - One of the best experts on this subject based on the ideXlab platform.
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Redox regulation of tumor cell toxicity by flavones from Lethedon tannaensis.
Free radical biology & medicine, 1999Co-Authors: R V Bensasson, A Jossang, A Zahir, B Bodo, E J LandAbstract:The purpose of the present work has been to seek a correlation of potential predictive value, demonstrating redox control of cytotoxicity toward human Nasopharynx Carcinoma (KB) cells by seven 5-hydroxy-7-methoxyflavones, together with two glycoside derivatives, all extracted from Lethedon tannaensis. In this approach, redox control is characterized by a physicochemical parameter expressing quantitatively the relative electron-donating power of the flavones, this parameter being the second order rate constant, kdelta, for quenching of singlet oxygen O2 (1deltag). This rate constant kdelta is usually related to the ability of a given molecule D to donate an electron and, thus, with the reduction potential E of the couple (D*+/D). Our results show that the flavone toxicity is linearly correlated with ease of oxidation: the higher the rate constant of reaction with singlet oxygen, the easier the oxidation, the less positive or more negative the reduction potential ((D*+/D), the higher the cytotoxicity. The results suggest new screening strategies to identify and improve potential antitumor drugs.
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Redox regulation of tumor cell toxicity by flavones from Lethedon tannaensis.
Free Radical Biology and Medicine, 1999Co-Authors: R V Bensasson, Abdellatif Zahir, Akino Jossang, Bernard Bodo, E J LandAbstract:Abstract The purpose of the present work has been to seek a correlation of potential predictive value, demonstrating redox control of cytotoxicity toward human Nasopharynx Carcinoma (KB) cells by seven 5-hydroxy-7-methoxyflavones, together with two glycoside derivatives, all extracted from Lethedon tannaensis. In this approach, redox control is characterized by a physicochemical parameter expressing quantitatively the relative electron-donating power of the flavones, this parameter being the second order rate constant, kΔ, for quenching of singlet oxygen O2 (1Δg). This rate constant kΔ is usually related to the ability of a given molecule D to donate an electron and, thus, with the reduction potential E of the couple (D•+/D). Our results show that the flavone toxicity is linearly correlated with ease of oxidation: the higher the rate constant of reaction with singlet oxygen, the easier the oxidation, the less positive or more negative the reduction potential ((D•+/D), the higher the cytotoxicity. The results suggest new screening strategies to identify and improve potential antitumor drugs.
Chloe Burman - One of the best experts on this subject based on the ideXlab platform.
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the effect of setup uncertainties on the treatment of Nasopharynx cancer
International Journal of Radiation Oncology Biology Physics, 1993Co-Authors: Margie Hunt, Gerald J Kutcher, Chloe Burman, Daniel E Fass, Louis B Harrison, Steven A Leibel, Zvi FuksAbstract:Abstract Purpose: As radiation treatment techniques become more complicated, the need to understand the effect of uncertainties on dose distributions increases. This study investigates the effect of positional uncertainities for patients with Nasopharynx Carcinoma treated with a multiple field conformal boost technique. Three dimensional setup errors were measured for six patients and the effect on patient dose was evaluated using dose volume histograms. Methods and Materials: A method is presented for determining 3-dimensional translational and rotational setup errors by identifying anatomical landmarks on two treatment field images and their corresponding simulation images. Measurements were made on a daily basis for six patients undergoing conformal treatment. Results: The average magnitude of the tmnsiational errors was between 1.5 and 3 mm while the average distance between simulation and treatment isocenters was 5 mm. Both systematic and random setup errors were observed. Dose volume histograms incorporating these uncertainties for standard parallel opposed and conformal techniques were generated for patients experiencing random and systematic setup errors. Conclusion: The data imply that positional uncertainties effect the daily dose distributions for target and critical structures differently and that the effect may be treatment technique dependent. These results demonstrate the need to measure setup uncertainties for all sites and to develop techniques for incorporating dose uncertainties in treatment plans.
Steven A Leibel - One of the best experts on this subject based on the ideXlab platform.
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the effect of setup uncertainties on the treatment of Nasopharynx cancer
International Journal of Radiation Oncology Biology Physics, 1993Co-Authors: Margie Hunt, Gerald J Kutcher, Chloe Burman, Daniel E Fass, Louis B Harrison, Steven A Leibel, Zvi FuksAbstract:Abstract Purpose: As radiation treatment techniques become more complicated, the need to understand the effect of uncertainties on dose distributions increases. This study investigates the effect of positional uncertainities for patients with Nasopharynx Carcinoma treated with a multiple field conformal boost technique. Three dimensional setup errors were measured for six patients and the effect on patient dose was evaluated using dose volume histograms. Methods and Materials: A method is presented for determining 3-dimensional translational and rotational setup errors by identifying anatomical landmarks on two treatment field images and their corresponding simulation images. Measurements were made on a daily basis for six patients undergoing conformal treatment. Results: The average magnitude of the tmnsiational errors was between 1.5 and 3 mm while the average distance between simulation and treatment isocenters was 5 mm. Both systematic and random setup errors were observed. Dose volume histograms incorporating these uncertainties for standard parallel opposed and conformal techniques were generated for patients experiencing random and systematic setup errors. Conclusion: The data imply that positional uncertainties effect the daily dose distributions for target and critical structures differently and that the effect may be treatment technique dependent. These results demonstrate the need to measure setup uncertainties for all sites and to develop techniques for incorporating dose uncertainties in treatment plans.
