Stéphanie Corde | University of Wollongong (original) (raw)

Papers by Stéphanie Corde

Research paper thumbnail of In Vivo Measurement of Gadolinium Concentration in a Rat Glioma Model by Monochromatic Quantitative Computed Tomography

Investigative Radiology, 2004

Monochromatic quantitative computed tomography allows a nondestructive and quantitative measureme... more Monochromatic quantitative computed tomography allows a nondestructive and quantitative measurement of gadolinium (Gd) concentration. This technique was used in the C6 rat glioma model to compare gadopentetate dimeglumine and gadobutrol. Rats bearing late-stage gliomas received 2.5 mmol/kg (392.5 mg Gd/kg) of gadopentetate dimeglumine (n = 5) and gadobutrol (n = 6) intravenously before the imaging session performed at the European Synchrotron Radiation Facility. Monochromatic quantitative computed tomography enabled in vivo follow-up of Gd concentration as a function of time in specified regions of interest. Surprisingly, after gadobutrol injection, Gd concentrations in the center and periphery of the tumor were higher than those after gadopentetate injection, although identical in normal and contralateral area of the brain. The in vivo assessment of absolute Gd concentrations revealed differences in gadobutrol and gadopentetate dimeglumine behaviors in tumoral tissues despite injections in the same conditions. These differences might be attributed to different characteristics of the contrast agents.

Research paper thumbnail of I-125 ROPES eye plaque dosimetry: Validation of a commercial 3D ophthalmic brachytherapy treatment planning system and independent dose calculation software with GafChromic® EBT3 films

Medical Physics, 2013

The purpose of this study was to measure the dose distributions for different Radiation Oncology ... more The purpose of this study was to measure the dose distributions for different Radiation Oncology Physics and Engineering Services, Australia (ROPES) type eye plaques loaded with I-125 (model 6711) seeds using GafChromic(®) EBT3 films, in order to verify the dose distributions in the Plaque Simulator™ (PS) ophthalmic 3D treatment planning system. The brachytherapy module of RADCALC(®) was used to independently check the dose distributions calculated by PS. Correction factors were derived from the measured data to be used in PS to account for the effect of the stainless steel ROPES plaque backing on the 3D dose distribution. Using GafChromic(®) EBT3 films inserted in a specially designed Solid Water™ eye ball phantom, dose distributions were measured three-dimensionally both along and perpendicular to I-125 (model 6711) loaded ROPES eye plaque's central axis (CAX) with 2 mm depth increments. Each measurement was performed in full scatter conditions both with and without the stainless steel plaque backing attached to the eye plaque, to assess its effect on the dose distributions. Results were compared to the dose distributions calculated by Plaque Simulator™ and checked independently with RADCALC(®). The EBT3 film measurements without the stainless steel backing were found to agree with PS and RADCALC(®) to within 2% and 4%, respectively, on the plaque CAX. Also, RADCALC(®) was found to agree with PS to within 2%. The CAX depth doses measured using EBT3 film with the stainless steel backing were observed to result in a 4% decrease relative to when the backing was not present. Within experimental uncertainty, the 4% decrease was found to be constant with depth and independent of plaque size. Using a constant dose correction factor of T = 0.96 in PS, where the calculated dose for the full water scattering medium is reduced by 4% in every voxel in the dose grid, the effect of the plaque backing was accurately modeled in the planning system. Off-axis profiles were also modeled in PS by taking into account the three-dimensional model of the plaque backing. The doses calculated by PS and RADCALC(®) for uniformly loaded ROPES plaques in full and uniform scattering conditions were validated by the EBT3 film measurements. The stainless steel plaque backing was observed to decrease the measured dose by 4%. Through the introduction of a scalar correction factor (0.96) in PS, the dose homogeneity effect of the stainless steel plaque backing was found to agree with the measured EBT3 film measurements.

Research paper thumbnail of Pilot dose intercomparisons of 3D and 4D advanced lung radiotherapy

Physica Medica, 2014

ABSTRACT As part of an evaluation of advanced radiotherapy (RT) technology, a number of pilot int... more ABSTRACT As part of an evaluation of advanced radiotherapy (RT) technology, a number of pilot intercomparisons have been developed and carried out of planning and ‘treatment’ delivery for advanced lung treatments ( FFF beams, VMAT, SBRT and 4D RT, etc). There are few, or no, reported audits/intercomparisons of many of these combinations.

Research paper thumbnail of The evaluation of a 2D diode array in “magic phantom” for use in high dose rate brachytherapy pretreatment quality assurance

Medical physics, 2015

High dose rate (HDR) brachytherapy is a treatment method that is used increasingly worldwide. The... more High dose rate (HDR) brachytherapy is a treatment method that is used increasingly worldwide. The development of a sound quality assurance program for the verification of treatment deliveries can be challenging due to the high source activity utilized and the need for precise measurements of dwell positions and times. This paper describes the application of a novel phantom, based on a 2D 11 × 11 diode array detection system, named “magic phantom” (MPh), to accurately measure plan dwell positions and times, compare them directly to the treatment plan, determine errors in treatment delivery, and calculate absorbed dose. The magic phantom system was CT scanned and a 20 catheter plan was generated to simulate a nonspecific treatment scenario. This plan was delivered to the MPh and, using a custom developed software suite, the dwell positions and times were measured and compared to the plan. The original plan was also modified, with changes not disclosed to the primary authors, and measu...

Research paper thumbnail of Experimental radiotherapy by photon activation at ESRF. Study of human tumor cells radiosensitivity after resonant excitation of a DNA hetero atom, the platinum

Research paper thumbnail of SESSION 12-CONTRAST AGENTS--REACTION AND TOXICITY-Enhanced Radio Sensitivity with Iodinated Contrast Agents Using Monochromatic Synchrotron X-Rays on Human Cancerous Cells

Research paper thumbnail of Synchrotron photoactivation of cis-platin (PAT-Plat): radiobiological results

Research paper thumbnail of Rats with brain F98 glioma treated with cisplatinum and monochromatic synchrotron X-rays in conditions able to trigger Auger effect

Research paper thumbnail of Repositioning of the patient in stereotaxic radiotherapy: contribution of a radiological imaging system

Research paper thumbnail of Multi-centre assessment of a 4D radiotherapy quality assurance phantom

Research paper thumbnail of Multi-centre assessment of a 4D radiotherapy quality assurance, verification and audit phantom

Research paper thumbnail of Synchrotron radiation computed tomography station at the ESRF biomedical beamline

The different tomography imaging modalities of the ESRF Medical Beamline are described and resear... more The different tomography imaging modalities of the ESRF Medical Beamline are described and research applications are presented

Research paper thumbnail of Research at the European Synchrotron Radiation Facility medical beamline

Cellular and molecular biology (Noisy-le-Grand, France), 2000

The application of synchrotron radiation in medical research has become a mature field of researc... more The application of synchrotron radiation in medical research has become a mature field of research at synchrotron facilities worldwide. In the relatively short time that synchrotrons have been available to the scientific community, their characteristic beams of UV and X-ray radiation have been applied to virtually all areas of medical science which use ionizing radiation. The ability to tune intense monochromatic beams over wide energy ranges differentiates these sources from standard clinical and research tools. At the European Synchrotron Radiation Facility (Grenoble, France), a major research facility is operational on an advanced wiggler radiation beamport, ID17. The beamport is designed to carry out a broad range of research ranging from cell radiation biology to in vivo human studies. Medical imaging programs at ID17 include transvenous coronary angiography, computed tomography, mammography and bronchography. In addition, a major research program on microbeam radiation therapy...

Research paper thumbnail of In vivo K-edge imaging with synchrotron radiation

Cellular and molecular biology (Noisy-le-Grand, France), 2000

We present in this paper two imaging techniques using contrast agents assessed with in vivo exper... more We present in this paper two imaging techniques using contrast agents assessed with in vivo experiments. Both methods are based on the same physical principle, and were implemented at the European Synchrotron Radiation Facility medical beamline. The first one is intravenous coronary angiography using synchrotron radiation X-rays. This imaging technique has been planned for human studies in the near future. We describe the first experiments that were carried out with pigs at the ESRF. The second imaging mode is computed tomography using synchrotron radiation on rats bearing brain tumors. Owing to synchrotron radiation physical properties, these new imaging methods provide additional information compared to conventional techniques. After infusion of the contrast agent, it is possible to derive from the images the concentration of the contrast agent in the tumor area for the computed tomography and in any visible vessel for the angiography method.

Research paper thumbnail of Synchrotron photoactivation of cisplatin elicits an extra number of DNA breaks that stimulate RAD51-mediated repair pathways

Cancer research, Jan 15, 2003

Combination of cis-platinum with ionizing radiation is one of the most promising anticancer treat... more Combination of cis-platinum with ionizing radiation is one of the most promising anticancer treatments that appears to be more efficient than radiotherapy alone. Unlike conventional X-ray emitters, accelerators of high energy particles like synchrotrons display powerful and monochromatizable radiation that makes the induction of an Auger electron cascade in cis-platinum molecules [also called photoactivation of cis-platinum (PAT-Plat)] theoretically possible. Here, we examined the molecular consequences of one of the first attempts of synchrotron PAT-Plat, performed at the European Synchrotron Research Facility (Grenoble-France). PAT-Plat was found to result in an extra number of slowly repairable DNA double-strand breaks, inhibition of DNA-protein kinase activity, dramatic nuclear relocalization of RAD51, hyperphosphorylation of the BRCA1 protein, and activation of proto-oncogenic c-Abl tyrosine kinase.

Research paper thumbnail of 4D lung SBRT: Dosimetric assessment using Gafchromic films

Any information contained in this pdf file is automatically generated from digital material submi... more Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to third-party sites or information are provided solely as a convenience to you and do not in any way constitute or imply RANZCR/AIR/ACPSEM's endorsement, sponsorship or recommendation of the third party, information, product or service. RANZCR/AIR/ ACPSEM is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold RANZCR/AIR/ACPSEM harmless from and against a...

Research paper thumbnail of Synchrotron stereotactic radiotherapy: dosimetry by Fricke gel and Monte Carlo simulations

Physics in medicine and biology, 2004

Synchrotron stereotactic radiotherapy (SSR) consists in loading the tumour with a high atomic num... more Synchrotron stereotactic radiotherapy (SSR) consists in loading the tumour with a high atomic number element (Z), and exposing it to monochromatic x-rays from a synchrotron source (50-100 keV), in stereotactic conditions. The dose distribution results from both the stereotactic monochromatic x-ray irradiation and the presence of the high Z element. The purpose of this preliminary study was to evaluate the two-dimensional dose distribution resulting solely from the irradiation geometry, using Monte Carlo simulations and a Fricke gel dosimeter. The verification of a Monte Carlo-based dosimetry was first assessed by depth dose measurements in a water tank. We thereafter used a Fricke dosimeter to compare Monte Carlo simulations with dose measurements. The Fricke dosimeter is a solution containing ferrous ions which are oxidized to ferric ions under ionizing radiation, proportionally to the absorbed dose. A cylindrical phantom filled with Fricke gel was irradiated in stereotactic conditions over several slices with a continuous beam (beam section = 0.1 x 1 cm2). The phantom and calibration vessels were then imaged by nuclear magnetic resonance. The measured doses were fairly consistent with those predicted by Monte Carlo simulations. However, the measured maximum absolute dose was 10% underestimated regarding calculation. The loss of information in the higher region of dose is explained by the diffusion of ferric ions. Monte Carlo simulation is the most accurate tool for dosimetry including complex geometries made of heterogeneous materials. Although the technique requires improvements, gel dosimetry remains an essential tool for the experimental verification of dose distribution in SSR with millimetre precision.

Research paper thumbnail of Synchrotron radiation-based experimental determination of the optimal energy for cell radiotoxicity enhancement following photoelectric effect on stable iodinated compounds

British journal of cancer, 2004

This study was designed to experimentally evaluate the optimal X-ray energy for increasing the ra... more This study was designed to experimentally evaluate the optimal X-ray energy for increasing the radiation energy absorbed in tumours loaded with iodinated compounds, using the photoelectric effect. SQ20B human cells were irradiated with synchrotron monochromatic beam tuned at 32.8, 33.5, 50 and 70 keV. Two cell treatments were compared to the control: cells suspended in 10 mg ml(-1) of iodine radiological contrast agent or cells pre-exposed with 10 microM of iodo-desoxyuridine (IUdR) for 48 h. Our radiobiological end point was clonogenic cell survival. Cells irradiated with both iodine compounds exhibited a radiation sensitisation enhancement. Moreover, it was energy dependent, with a maximum at 50 keV. At this energy, the sensitisation calculated at 10% survival was equal to 2.03 for cells suspended in iodinated contrast agent and 2.60 for IUdR. Cells pretreated with IUdR had higher sensitisation factors over the energy range than for those suspended in iodine contrast agent. Also, their survival curves presented no shoulder, suggesting complex lethal damages from Auger electrons. Our results confirm the existence of the 50 keV energy optimum for a binary therapeutic irradiation based on the presence of stable iodine in tumours and an external irradiation. Monochromatic synchrotron radiotherapy concept is hence proposed for increasing the differential effect between healthy and cancerous tissue irradiation.

Research paper thumbnail of In vivo measurement of gadolinium concentration in a rat glioma model by monochromatic quantitative computed tomography: comparison between gadopentetate dimeglumine and gadobutrol

Investigative radiology, 2004

Monochromatic quantitative computed tomography allows a nondestructive and quantitative measureme... more Monochromatic quantitative computed tomography allows a nondestructive and quantitative measurement of gadolinium (Gd) concentration. This technique was used in the C6 rat glioma model to compare gadopentetate dimeglumine and gadobutrol. Rats bearing late-stage gliomas received 2.5 mmol/kg (392.5 mg Gd/kg) of gadopentetate dimeglumine (n = 5) and gadobutrol (n = 6) intravenously before the imaging session performed at the European Synchrotron Radiation Facility. Monochromatic quantitative computed tomography enabled in vivo follow-up of Gd concentration as a function of time in specified regions of interest. Surprisingly, after gadobutrol injection, Gd concentrations in the center and periphery of the tumor were higher than those after gadopentetate injection, although identical in normal and contralateral area of the brain. The in vivo assessment of absolute Gd concentrations revealed differences in gadobutrol and gadopentetate dimeglumine behaviors in tumoral tissues despite injections in the same conditions. These differences might be attributed to different characteristics of the contrast agents.

Research paper thumbnail of Development of phantom and methodology for 3D and 4D dose intercomparisons for advanced lung radiotherapy

Journal of Physics: Conference Series, 2015

There are few reported intercomparisons or audits of combinations of advanced radiotherapy method... more There are few reported intercomparisons or audits of combinations of advanced radiotherapy methods, particularly for 4D treatments. As part of an evaluation of the implementation of advanced radiotherapy technology, a phantom and associated methods, initially developed for in-house commissioning and QA of 4D lung treatments, has been developed further with the aim of using it for end-to-end dose intercomparison of 4D treatment planning and delivery. The respiratory thorax phantom can house moving inserts with variable speed (breathing rate) and motion amplitude. In one set-up mode it contains a small ion chamber for point dose measurements, or alternatively it can hold strips of radiochromic film to measure dose distributions. Initial pilot and feasibility measurements have been carried out in one hospital to thoroughly test the methods and procedures before using it more widely across a range of hospitals and treatment systems. Overall, the results show good agreement between measured and calculated doses and distributions, supporting the use of the phantom and methodology for multi-centre intercomparisons. However, before wider use, refinements of the method and analysis are currently underway particularly for the film measurements.

Research paper thumbnail of In Vivo Measurement of Gadolinium Concentration in a Rat Glioma Model by Monochromatic Quantitative Computed Tomography

Investigative Radiology, 2004

Monochromatic quantitative computed tomography allows a nondestructive and quantitative measureme... more Monochromatic quantitative computed tomography allows a nondestructive and quantitative measurement of gadolinium (Gd) concentration. This technique was used in the C6 rat glioma model to compare gadopentetate dimeglumine and gadobutrol. Rats bearing late-stage gliomas received 2.5 mmol/kg (392.5 mg Gd/kg) of gadopentetate dimeglumine (n = 5) and gadobutrol (n = 6) intravenously before the imaging session performed at the European Synchrotron Radiation Facility. Monochromatic quantitative computed tomography enabled in vivo follow-up of Gd concentration as a function of time in specified regions of interest. Surprisingly, after gadobutrol injection, Gd concentrations in the center and periphery of the tumor were higher than those after gadopentetate injection, although identical in normal and contralateral area of the brain. The in vivo assessment of absolute Gd concentrations revealed differences in gadobutrol and gadopentetate dimeglumine behaviors in tumoral tissues despite injections in the same conditions. These differences might be attributed to different characteristics of the contrast agents.

Research paper thumbnail of I-125 ROPES eye plaque dosimetry: Validation of a commercial 3D ophthalmic brachytherapy treatment planning system and independent dose calculation software with GafChromic® EBT3 films

Medical Physics, 2013

The purpose of this study was to measure the dose distributions for different Radiation Oncology ... more The purpose of this study was to measure the dose distributions for different Radiation Oncology Physics and Engineering Services, Australia (ROPES) type eye plaques loaded with I-125 (model 6711) seeds using GafChromic(®) EBT3 films, in order to verify the dose distributions in the Plaque Simulator™ (PS) ophthalmic 3D treatment planning system. The brachytherapy module of RADCALC(®) was used to independently check the dose distributions calculated by PS. Correction factors were derived from the measured data to be used in PS to account for the effect of the stainless steel ROPES plaque backing on the 3D dose distribution. Using GafChromic(®) EBT3 films inserted in a specially designed Solid Water™ eye ball phantom, dose distributions were measured three-dimensionally both along and perpendicular to I-125 (model 6711) loaded ROPES eye plaque's central axis (CAX) with 2 mm depth increments. Each measurement was performed in full scatter conditions both with and without the stainless steel plaque backing attached to the eye plaque, to assess its effect on the dose distributions. Results were compared to the dose distributions calculated by Plaque Simulator™ and checked independently with RADCALC(®). The EBT3 film measurements without the stainless steel backing were found to agree with PS and RADCALC(®) to within 2% and 4%, respectively, on the plaque CAX. Also, RADCALC(®) was found to agree with PS to within 2%. The CAX depth doses measured using EBT3 film with the stainless steel backing were observed to result in a 4% decrease relative to when the backing was not present. Within experimental uncertainty, the 4% decrease was found to be constant with depth and independent of plaque size. Using a constant dose correction factor of T = 0.96 in PS, where the calculated dose for the full water scattering medium is reduced by 4% in every voxel in the dose grid, the effect of the plaque backing was accurately modeled in the planning system. Off-axis profiles were also modeled in PS by taking into account the three-dimensional model of the plaque backing. The doses calculated by PS and RADCALC(®) for uniformly loaded ROPES plaques in full and uniform scattering conditions were validated by the EBT3 film measurements. The stainless steel plaque backing was observed to decrease the measured dose by 4%. Through the introduction of a scalar correction factor (0.96) in PS, the dose homogeneity effect of the stainless steel plaque backing was found to agree with the measured EBT3 film measurements.

Research paper thumbnail of Pilot dose intercomparisons of 3D and 4D advanced lung radiotherapy

Physica Medica, 2014

ABSTRACT As part of an evaluation of advanced radiotherapy (RT) technology, a number of pilot int... more ABSTRACT As part of an evaluation of advanced radiotherapy (RT) technology, a number of pilot intercomparisons have been developed and carried out of planning and ‘treatment’ delivery for advanced lung treatments ( FFF beams, VMAT, SBRT and 4D RT, etc). There are few, or no, reported audits/intercomparisons of many of these combinations.

Research paper thumbnail of The evaluation of a 2D diode array in “magic phantom” for use in high dose rate brachytherapy pretreatment quality assurance

Medical physics, 2015

High dose rate (HDR) brachytherapy is a treatment method that is used increasingly worldwide. The... more High dose rate (HDR) brachytherapy is a treatment method that is used increasingly worldwide. The development of a sound quality assurance program for the verification of treatment deliveries can be challenging due to the high source activity utilized and the need for precise measurements of dwell positions and times. This paper describes the application of a novel phantom, based on a 2D 11 × 11 diode array detection system, named “magic phantom” (MPh), to accurately measure plan dwell positions and times, compare them directly to the treatment plan, determine errors in treatment delivery, and calculate absorbed dose. The magic phantom system was CT scanned and a 20 catheter plan was generated to simulate a nonspecific treatment scenario. This plan was delivered to the MPh and, using a custom developed software suite, the dwell positions and times were measured and compared to the plan. The original plan was also modified, with changes not disclosed to the primary authors, and measu...

Research paper thumbnail of Experimental radiotherapy by photon activation at ESRF. Study of human tumor cells radiosensitivity after resonant excitation of a DNA hetero atom, the platinum

Research paper thumbnail of SESSION 12-CONTRAST AGENTS--REACTION AND TOXICITY-Enhanced Radio Sensitivity with Iodinated Contrast Agents Using Monochromatic Synchrotron X-Rays on Human Cancerous Cells

Research paper thumbnail of Synchrotron photoactivation of cis-platin (PAT-Plat): radiobiological results

Research paper thumbnail of Rats with brain F98 glioma treated with cisplatinum and monochromatic synchrotron X-rays in conditions able to trigger Auger effect

Research paper thumbnail of Repositioning of the patient in stereotaxic radiotherapy: contribution of a radiological imaging system

Research paper thumbnail of Multi-centre assessment of a 4D radiotherapy quality assurance phantom

Research paper thumbnail of Multi-centre assessment of a 4D radiotherapy quality assurance, verification and audit phantom

Research paper thumbnail of Synchrotron radiation computed tomography station at the ESRF biomedical beamline

The different tomography imaging modalities of the ESRF Medical Beamline are described and resear... more The different tomography imaging modalities of the ESRF Medical Beamline are described and research applications are presented

Research paper thumbnail of Research at the European Synchrotron Radiation Facility medical beamline

Cellular and molecular biology (Noisy-le-Grand, France), 2000

The application of synchrotron radiation in medical research has become a mature field of researc... more The application of synchrotron radiation in medical research has become a mature field of research at synchrotron facilities worldwide. In the relatively short time that synchrotrons have been available to the scientific community, their characteristic beams of UV and X-ray radiation have been applied to virtually all areas of medical science which use ionizing radiation. The ability to tune intense monochromatic beams over wide energy ranges differentiates these sources from standard clinical and research tools. At the European Synchrotron Radiation Facility (Grenoble, France), a major research facility is operational on an advanced wiggler radiation beamport, ID17. The beamport is designed to carry out a broad range of research ranging from cell radiation biology to in vivo human studies. Medical imaging programs at ID17 include transvenous coronary angiography, computed tomography, mammography and bronchography. In addition, a major research program on microbeam radiation therapy...

Research paper thumbnail of In vivo K-edge imaging with synchrotron radiation

Cellular and molecular biology (Noisy-le-Grand, France), 2000

We present in this paper two imaging techniques using contrast agents assessed with in vivo exper... more We present in this paper two imaging techniques using contrast agents assessed with in vivo experiments. Both methods are based on the same physical principle, and were implemented at the European Synchrotron Radiation Facility medical beamline. The first one is intravenous coronary angiography using synchrotron radiation X-rays. This imaging technique has been planned for human studies in the near future. We describe the first experiments that were carried out with pigs at the ESRF. The second imaging mode is computed tomography using synchrotron radiation on rats bearing brain tumors. Owing to synchrotron radiation physical properties, these new imaging methods provide additional information compared to conventional techniques. After infusion of the contrast agent, it is possible to derive from the images the concentration of the contrast agent in the tumor area for the computed tomography and in any visible vessel for the angiography method.

Research paper thumbnail of Synchrotron photoactivation of cisplatin elicits an extra number of DNA breaks that stimulate RAD51-mediated repair pathways

Cancer research, Jan 15, 2003

Combination of cis-platinum with ionizing radiation is one of the most promising anticancer treat... more Combination of cis-platinum with ionizing radiation is one of the most promising anticancer treatments that appears to be more efficient than radiotherapy alone. Unlike conventional X-ray emitters, accelerators of high energy particles like synchrotrons display powerful and monochromatizable radiation that makes the induction of an Auger electron cascade in cis-platinum molecules [also called photoactivation of cis-platinum (PAT-Plat)] theoretically possible. Here, we examined the molecular consequences of one of the first attempts of synchrotron PAT-Plat, performed at the European Synchrotron Research Facility (Grenoble-France). PAT-Plat was found to result in an extra number of slowly repairable DNA double-strand breaks, inhibition of DNA-protein kinase activity, dramatic nuclear relocalization of RAD51, hyperphosphorylation of the BRCA1 protein, and activation of proto-oncogenic c-Abl tyrosine kinase.

Research paper thumbnail of 4D lung SBRT: Dosimetric assessment using Gafchromic films

Any information contained in this pdf file is automatically generated from digital material submi... more Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to third-party sites or information are provided solely as a convenience to you and do not in any way constitute or imply RANZCR/AIR/ACPSEM's endorsement, sponsorship or recommendation of the third party, information, product or service. RANZCR/AIR/ ACPSEM is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold RANZCR/AIR/ACPSEM harmless from and against a...

Research paper thumbnail of Synchrotron stereotactic radiotherapy: dosimetry by Fricke gel and Monte Carlo simulations

Physics in medicine and biology, 2004

Synchrotron stereotactic radiotherapy (SSR) consists in loading the tumour with a high atomic num... more Synchrotron stereotactic radiotherapy (SSR) consists in loading the tumour with a high atomic number element (Z), and exposing it to monochromatic x-rays from a synchrotron source (50-100 keV), in stereotactic conditions. The dose distribution results from both the stereotactic monochromatic x-ray irradiation and the presence of the high Z element. The purpose of this preliminary study was to evaluate the two-dimensional dose distribution resulting solely from the irradiation geometry, using Monte Carlo simulations and a Fricke gel dosimeter. The verification of a Monte Carlo-based dosimetry was first assessed by depth dose measurements in a water tank. We thereafter used a Fricke dosimeter to compare Monte Carlo simulations with dose measurements. The Fricke dosimeter is a solution containing ferrous ions which are oxidized to ferric ions under ionizing radiation, proportionally to the absorbed dose. A cylindrical phantom filled with Fricke gel was irradiated in stereotactic conditions over several slices with a continuous beam (beam section = 0.1 x 1 cm2). The phantom and calibration vessels were then imaged by nuclear magnetic resonance. The measured doses were fairly consistent with those predicted by Monte Carlo simulations. However, the measured maximum absolute dose was 10% underestimated regarding calculation. The loss of information in the higher region of dose is explained by the diffusion of ferric ions. Monte Carlo simulation is the most accurate tool for dosimetry including complex geometries made of heterogeneous materials. Although the technique requires improvements, gel dosimetry remains an essential tool for the experimental verification of dose distribution in SSR with millimetre precision.

Research paper thumbnail of Synchrotron radiation-based experimental determination of the optimal energy for cell radiotoxicity enhancement following photoelectric effect on stable iodinated compounds

British journal of cancer, 2004

This study was designed to experimentally evaluate the optimal X-ray energy for increasing the ra... more This study was designed to experimentally evaluate the optimal X-ray energy for increasing the radiation energy absorbed in tumours loaded with iodinated compounds, using the photoelectric effect. SQ20B human cells were irradiated with synchrotron monochromatic beam tuned at 32.8, 33.5, 50 and 70 keV. Two cell treatments were compared to the control: cells suspended in 10 mg ml(-1) of iodine radiological contrast agent or cells pre-exposed with 10 microM of iodo-desoxyuridine (IUdR) for 48 h. Our radiobiological end point was clonogenic cell survival. Cells irradiated with both iodine compounds exhibited a radiation sensitisation enhancement. Moreover, it was energy dependent, with a maximum at 50 keV. At this energy, the sensitisation calculated at 10% survival was equal to 2.03 for cells suspended in iodinated contrast agent and 2.60 for IUdR. Cells pretreated with IUdR had higher sensitisation factors over the energy range than for those suspended in iodine contrast agent. Also, their survival curves presented no shoulder, suggesting complex lethal damages from Auger electrons. Our results confirm the existence of the 50 keV energy optimum for a binary therapeutic irradiation based on the presence of stable iodine in tumours and an external irradiation. Monochromatic synchrotron radiotherapy concept is hence proposed for increasing the differential effect between healthy and cancerous tissue irradiation.

Research paper thumbnail of In vivo measurement of gadolinium concentration in a rat glioma model by monochromatic quantitative computed tomography: comparison between gadopentetate dimeglumine and gadobutrol

Investigative radiology, 2004

Monochromatic quantitative computed tomography allows a nondestructive and quantitative measureme... more Monochromatic quantitative computed tomography allows a nondestructive and quantitative measurement of gadolinium (Gd) concentration. This technique was used in the C6 rat glioma model to compare gadopentetate dimeglumine and gadobutrol. Rats bearing late-stage gliomas received 2.5 mmol/kg (392.5 mg Gd/kg) of gadopentetate dimeglumine (n = 5) and gadobutrol (n = 6) intravenously before the imaging session performed at the European Synchrotron Radiation Facility. Monochromatic quantitative computed tomography enabled in vivo follow-up of Gd concentration as a function of time in specified regions of interest. Surprisingly, after gadobutrol injection, Gd concentrations in the center and periphery of the tumor were higher than those after gadopentetate injection, although identical in normal and contralateral area of the brain. The in vivo assessment of absolute Gd concentrations revealed differences in gadobutrol and gadopentetate dimeglumine behaviors in tumoral tissues despite injections in the same conditions. These differences might be attributed to different characteristics of the contrast agents.

Research paper thumbnail of Development of phantom and methodology for 3D and 4D dose intercomparisons for advanced lung radiotherapy

Journal of Physics: Conference Series, 2015

There are few reported intercomparisons or audits of combinations of advanced radiotherapy method... more There are few reported intercomparisons or audits of combinations of advanced radiotherapy methods, particularly for 4D treatments. As part of an evaluation of the implementation of advanced radiotherapy technology, a phantom and associated methods, initially developed for in-house commissioning and QA of 4D lung treatments, has been developed further with the aim of using it for end-to-end dose intercomparison of 4D treatment planning and delivery. The respiratory thorax phantom can house moving inserts with variable speed (breathing rate) and motion amplitude. In one set-up mode it contains a small ion chamber for point dose measurements, or alternatively it can hold strips of radiochromic film to measure dose distributions. Initial pilot and feasibility measurements have been carried out in one hospital to thoroughly test the methods and procedures before using it more widely across a range of hospitals and treatment systems. Overall, the results show good agreement between measured and calculated doses and distributions, supporting the use of the phantom and methodology for multi-centre intercomparisons. However, before wider use, refinements of the method and analysis are currently underway particularly for the film measurements.