72 research outputs found
Aniversari Entitat - 1980
No full text111è Aniversari de l’Entitat, El Dr. Narcís Jubany Cardenal Arquebisbe de Barcelona, imposant la insígnia de soci a Joan Subiel
Feasibility studies on the application of relativistic electron beams from a laser plasma wakefield accelerator in radiotherapy
No full textVery high energy electrons (VHEEs) (100-250 MeV) have the potential of becoming an alternative modality in radiotherapy because of their improved dosimetry properties compared with X-ray photons, which could confer possible radiobiological benefits. The rapid development of ultra-compact laser-plasma wakefield accelerators (LWFAs) is now providing a potential low cost device for VHEE radiotherapy. These beams have characteristics unlike any other beams currently used for radiotherapy: femotosecond radiation pulses, small field size and energies that exceed electron energies currently used in clinical applications. A set of Monte Carlo (MC) calculations have been performed to study dosimetric properties of VHEEs propagating in water. To assess radiation protection and safety handling issues, the generation of neutrons, induced activity and equivalent doses have been evaluated. A dosimetry system, consisting of EBT2 Gafchromic® film and EPSON Expression 10000XL scanner, for VHEEs has been established. EBT2 Gafchromic film turns out to be a robust dosimeter with a minor energy-dependent response over a broad range of beam energies and modalities, and can be successfully used for dosimetry of very high energy electron beams. The dosimetric measurements have been carried out using three different accelerators: a 20 MeV clinical LINAC, a 165 MeV conventional LINAC and a 135 MeV laser-plasma wakefield accelerator. The measurements have been compared with Monte Carlo simulations using the FLUKA code. Additionally, the set of dose measurements employing IBA CC04 ionisation chamber has been presented. Dosimetric measurements have been complemented by preliminary cancer cell irradiation studies to determine the toxicity and dose response to LWFA VHEEs of two lung cancer cell lines (A549 and H460). The efficacy of VHEEs on in vitro tumour cells has been assessed by clonogenic assay and γ-H2AX assay employing immunofluorescence detection of signalling molecules has been deployed to indicate DNA double-strand breaks and repair.Very high energy electrons (VHEEs) (100-250 MeV) have the potential of becoming an alternative modality in radiotherapy because of their improved dosimetry properties compared with X-ray photons, which could confer possible radiobiological benefits. The rapid development of ultra-compact laser-plasma wakefield accelerators (LWFAs) is now providing a potential low cost device for VHEE radiotherapy. These beams have characteristics unlike any other beams currently used for radiotherapy: femotosecond radiation pulses, small field size and energies that exceed electron energies currently used in clinical applications. A set of Monte Carlo (MC) calculations have been performed to study dosimetric properties of VHEEs propagating in water. To assess radiation protection and safety handling issues, the generation of neutrons, induced activity and equivalent doses have been evaluated. A dosimetry system, consisting of EBT2 Gafchromic® film and EPSON Expression 10000XL scanner, for VHEEs has been established. EBT2 Gafchromic film turns out to be a robust dosimeter with a minor energy-dependent response over a broad range of beam energies and modalities, and can be successfully used for dosimetry of very high energy electron beams. The dosimetric measurements have been carried out using three different accelerators: a 20 MeV clinical LINAC, a 165 MeV conventional LINAC and a 135 MeV laser-plasma wakefield accelerator. The measurements have been compared with Monte Carlo simulations using the FLUKA code. Additionally, the set of dose measurements employing IBA CC04 ionisation chamber has been presented. Dosimetric measurements have been complemented by preliminary cancer cell irradiation studies to determine the toxicity and dose response to LWFA VHEEs of two lung cancer cell lines (A549 and H460). The efficacy of VHEEs on in vitro tumour cells has been assessed by clonogenic assay and γ-H2AX assay employing immunofluorescence detection of signalling molecules has been deployed to indicate DNA double-strand breaks and repair
Dosimetry of ultra-short high dose-per-pulse very high energy electrons
No full textDetailed characterisation of a standard plane-parallel ionisation chamber has been made when exposed to high dose-per-pulse Very High Energy Electrons (VHEEs). First-of-their kind absolute dosimetry measurements using a graphite calorimeter have been conducted in a novel VHEE beam and ionisation chamber correction factors such as ion recombination have been shown to be significant. Ion recombination has been shown to increase with increasing dose-per-pulse, with a collection efficiency as low as 4% for the highest dose-per-pulse investigated, 5.26 Gy/pulse. Current theoretical recombination models provide a reasonable description of the ion recombination behaviour. Moreover, the free-electron fraction component of ion recombination models was shown to vary with dose-per-pulse, contrary to what is typically expected, and an updated model proposed in this work has been shown to provide a better fit to data than currently available recombination models.
Following the experimental campaigns, Monte Carlo (MC) simulations were conducted to determine stopping-power-ratios, perturbation factors and beam quality correction factors for a reference 12 MeV beam and 200 MeV user VHEE beams using the Geant4 general purpose MC code. A Fano test was conducted and several charged particle transport parameter configurations were found to pass the Fano cavity test. Modifications to current Geant4 default physics parameters were also determined in order to provide a passing Fano test at 200 MeV.
Stopping-power-ratios were found to agree within uncertainties with that found previously using EGSnrc at 12 MeV, however, perturbation factors were found to vary more than previous studies. The stopping-power-ratio at 200 MeV was found to be approximately 6% lower than what is estimated in dosimetry protocols for a reference beam quality with similar measurement depth, with a total perturbation of approximately 5%.
The beam quality correction factor, for the conversion of dose from the reference beam to that of the user beam, was found to lead to an approximately 10% reduction in measured chamber dose in comparison to what was originally determined.
Correction factors for the graphite calorimeter have also been calculated for the 200 MeV VHEE beam with the vacuum gap correction factor shown to be within 1% of unity.
Implementation of these new corrections to early experimental data largely remedies un-physical ion chamber measurements which showed greater than 100% ion collection efficiencies for a number of collecting voltages. It is now clear that improved dosimetry for VHEEs is vital to determine reasonable and accurate characterisations of secondary standard ionisation chambers
Metrology for advanced radiotherapy using particle beams with ultra-high dose rates
No full textDosimetry of ultra-high dose rate beams is one of the critical components which is required for safe implementation of FLASH radiotherapy (RT) into clinical practice. In the past years several national and international programmes have emerged with the aim to address some of the needs that are required for translation of this modality to clinics. These involve the establishment of dosimetry standards as well as the validation of protocols and dosimetry procedures. This review provides an overview of recent developments in the field of dosimetry for FLASH RT, with particular focus on primary and secondary standard instruments, and provides a brief outlook on the future work which is required to enable clinical implementation of FLASH RT.This project 18HLT04 UHDpulse has received funding from the EMPIR programme co-financed by the Participating States and from the European Union\u2019s Horizon 2020 research and innovation programmePeer reviewe
Architecture, flexibility and performance of a special electron linac dedicated to Flash radiotherapy research: electronFlash with a triode gun of the centro pisano flash radiotherapy (CPFR)
No full textThe FLASH effect is a radiobiological phenomenon that has garnered considerable interest in the clinical field. Pre-clinical experimental studies have highlighted its potential to reduce side effects on healthy tissues while maintaining isoeffectiveness on tumor tissues, thus widening the therapeutic window and enhancing the effectiveness of radiotherapy. The FLASH effect is achieved through the administration of the complete therapeutic radiation dose within a brief time frame, shorter than 200 milliseconds, and, therefore, utilizing remarkably high average dose rates above at least 40 Gy/s. Despite its potential in radiotherapy, the radiobiological mechanisms governing this effect and its quantitative relationship with temporal parameters of the radiation beam, such as dose-rate, dose-per-pulse, and average dose-rate within the pulse, remain inadequately elucidated. A more profound comprehension of these underlying mechanisms is imperative to optimize the clinical application and translation of the FLASH effect into routine practice. Due to the aforementioned factors, the undertaking of quantitative radiobiological investigations becomes imperative, necessitating the utilization of sophisticated and adaptable apparatus capable of generating radiation beams with exceedingly high dose-rates and dose-per-pulse characteristics. This study presents a comprehensive account of the design and operational capabilities of a Linear Accelerator (LINAC) explicitly tailored for FLASH radiotherapy research purposes. Termed the “ElectronFlash” (EF) LINAC, this specialized system employs a low-energy configuration (7 and 9 MeV) and incorporates a triode gun. The EF LINAC is currently operational at the Centro Pisano FLASH Radiotherapy (CPFR) facility located in Pisa, Italy. Lastly, this study presents specific instances exemplifying the LINAC’s adaptability, enabling the execution of hitherto unprecedented experiments. By enabling independent variations of the temporal parameters of the radiation beam implicated in the FLASH effect, these experiments facilitate the acquisition of quantitative data concerning the effect’s dependence on these specific parameters. This novel approach hopefully contributes to a more comprehensive understanding of the FLASH effect, shedding light on its intricate radiobiological behavior and offering valuable insights for optimizing its clinical implementation
Standard requirements for clinical very high energy electron and ultra high dose rate medical devices
No full textVery High-Energy Electrons (VHEE) present a promising innovation in radiation therapy (RT), particularly for the treatment of deep-seated tumors using Ultra High Dose Rate (UHDR) within the framework of FLASH-RT. VHEE offers significant advantages, such as improved tumor targeting, reduced treatment times, and potential utilization of the FLASH effect, which may minimize normal tissue toxicity. However, the lack of an international technical standard for VHEE systems, especially for UHDR applications, remains a critical challenge. Current standards for radiation therapy equipment, such as IEC 60601-2-1 and IEC 60601-2-64, do not encompass VHEE technology. This regulatory gap underscores the need for developing a structured international standard to ensure the basic safety and essential performance of VHEE medical devices. Addressing this challenge requires overcoming complex dose delivery issues, such as the interaction of multiple fields and beam conformality and incorporating novel techniques like broad beam or pencil beam scanning. Establishing comprehensive regulatory standards is essential to ensure patient safety, consistent treatment practices, and the successful clinical integration of VHEE systems. These standards must encompass design guidelines, radiation protection protocols, and integration with existing oncology practices. Collaborative research and development efforts are crucial to formulating evidence-based guidelines, fostering the safe and effective use of VHEE in clinical settings. By addressing these challenges, VHEE technology has the potential to revolutionize cancer therapy, particularly for deep-seated tumors, while enhancing therapeutic outcomes for patients
Architecture, flexibility and performance of a special electron linac dedicated to Flash radiotherapy research: electronFlash with a triode gun of the centro pisano flash radiotherapy (CPFR)
No full textThe FLASH effect is a radiobiological phenomenon that has garnered considerable interest in the clinical field. Pre-clinical experimental studies have highlighted its potential to reduce side effects on healthy tissues while maintaining isoeffectiveness on tumor tissues, thus widening the therapeutic window and enhancing the effectiveness of radiotherapy. The FLASH effect is achieved through the administration of the complete therapeutic radiation dose within a brief time frame, shorter than 200 milliseconds, and, therefore, utilizing remarkably high average dose rates above at least 40 Gy/s. Despite its potential in radiotherapy, the radiobiological mechanisms governing this effect and its quantitative relationship with temporal parameters of the radiation beam, such as dose-rate, dose-per-pulse, and average dose-rate within the pulse, remain inadequately elucidated. A more profound comprehension of these underlying mechanisms is imperative to optimize the clinical application and translation of the FLASH effect into routine practice. Due to the aforementioned factors, the undertaking of quantitative radiobiological investigations becomes imperative, necessitating the utilization of sophisticated and adaptable apparatus capable of generating radiation beams with exceedingly high dose-rates and dose-per-pulse characteristics. This study presents a comprehensive account of the design and operational capabilities of a Linear Accelerator (LINAC) explicitly tailored for FLASH radiotherapy research purposes. Termed the "ElectronFlash" (EF) LINAC, this specialized system employs a low-energy configuration (7 and 9 MeV) and incorporates a triode gun. The EF LINAC is currently operational at the Centro Pisano FLASH Radiotherapy (CPFR) facility located in Pisa, Italy. Lastly, this study presents specific instances exemplifying the LINAC's adaptability, enabling the execution of hitherto unprecedented experiments. By enabling independent variations of the temporal parameters of the radiation beam implicated in the FLASH effect, these experiments facilitate the acquisition of quantitative data concerning the effect's dependence on these specific parameters. This novel approach hopefully contributes to a more comprehensive understanding of the FLASH effect, shedding light on its intricate radiobiological behavior and offering valuable insights for optimizing its clinical implementation
A Geant4 Fano test for novel very high energy electron beams
No full textObjective. The boundary crossing algorithm available in Geant4 10.07-p01 general purpose Monte Carlo code has been investigated for a 12 and 200 MeV electron source by the application of a Fano cavity test. Approach. Fano conditions were enforced through all simulations whilst varying individual charged particle transport parameters which control particle step size, ionisation and single scattering. Main Results. At 12 MeV, Geant4 was found to return excellent dose consistency within 0.1% even with the default parameter configurations. The 200 MeV case, however, showed significant consistency issues when default physics parameters were employed with deviations from unity of more than 6%. The effect of the inclusion of nuclear interactions was also investigated for the 200 MeV beam and was found to return good consistency for a number of parameter configurations. Significance. The Fano test is a necessary investigation to ensure the consistency of charged particle transport available in Geant4 before detailed detector simulations can be conducted
Evaluation of a micro ionization chamber for dosimetric measurements in image-guided preclinical irradiation platforms
No full textImage-guided small animal irradiation platforms deliver small radiation fields in the medium energy x-ray range. Commissioning of such platforms, followed by dosimetric verification of treatment planning, are mostly performed with radiochromic film. There is a need for independent measurement methods, traceable to primary standards, with the added advantage of immediacy in obtaining results. This investigation characterizes a small volume ionization chamber in medium energy x-rays for reference dosimetry in preclinical irradiation research platforms. The detector was exposed to a set of reference x-ray beams (0.5 to 4 mm Cu HVL). Leakage, reproducibility, linearity, response to detector's orientation, dose rate, and energy dependence were determined for a 3D PinPoint ionization chamber (PTW 31022). Polarity and ion recombination were also studied. Absorbed doses at 2 cm depth were compared, derived either by applying the experimentally determined cross-calibration coefficient at a typical small animal radiation platform "user's" quality (0.84 mm Cu HVL) or by interpolation from air kerma calibration coefficients in a set of reference beam qualities. In the range of reference x-ray beams, correction for ion recombination was less than 0.1%. The largest polarity correction was 1.4% (for 4 mm Cu HVL). Calibration and correction factors were experimentally determined. Measurements of absorbed dose with the PTW 31022, in conditions different from reference were successfully compared to measurements with a secondary standard ionization chamber. The implementation of an End-to-End test for delivery of image-targeted small field plans resulted in differences smaller than 3% between measured and treatment planning calculated doses. The investigation of the properties and response of a PTW 31022 small volume ionization chamber in medium energy x-rays and small fields can contribute to improve measurement uncertainties evaluation for reference and relative dosimetry of small fields delivered by preclinical irradiators while maintaining the traceability chain to primary standards
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