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Radiochromic Film Dosimetry in Kilovoltage X-­‐ray Beams: A Pre-­‐ Investigation for In Vitro Studies of Bystander Effects

Hossein, Zeinab (2015) MSFT01 20151
Medical Physics Programme
Medical Radiation Physics, Lund
Abstract
Purpose
Intensity modulation of radiation is one of several important conditions to evaluate for full understanding of how cells involved in the bystander effect influence each other when cells are exposed to radiation at low and high dose rates. The aim of this study was to develop and apply a useful and practical dosimetric method for measurement of the absorbed dose to cell cultures exposed to intensity modulated radiation in investigations of the bystander effects.

Material and methods
All irradiations in this study were performed using an orthovoltage x-ray unit at Skåne University Hospital in Lund using 120 kV and 200 kV. Film dosimetry using Gafchromic EBT3 type film was the method of choice for measurement of the absorbed... (More)
Purpose
Intensity modulation of radiation is one of several important conditions to evaluate for full understanding of how cells involved in the bystander effect influence each other when cells are exposed to radiation at low and high dose rates. The aim of this study was to develop and apply a useful and practical dosimetric method for measurement of the absorbed dose to cell cultures exposed to intensity modulated radiation in investigations of the bystander effects.

Material and methods
All irradiations in this study were performed using an orthovoltage x-ray unit at Skåne University Hospital in Lund using 120 kV and 200 kV. Film dosimetry using Gafchromic EBT3 type film was the method of choice for measurement of the absorbed dose. A number of measurements were performed to understand the basic properties of the film with respect to radiation response, including inter- and intra-individual film sheet variations. Furthermore, the effect of different scattering conditions was investigated, including the use of different calibration phantom materials and the amount of nutrition medium in the cell culture flask. Dose calibrations were carried out and to evaluate if the film calibration datasets returned the expected absorbed dose at different dose levels, a depth dose measurement was performed which was compared with ion chamber measurements. For dosimetric analysis of film measurements, three different software tools were evaluated, i.e., (i) the OmniPro software,
(ii) a locally developed MATLAB program called FILMGUI and (iii) the FilmQA Pro software.

Results
Generally, the variations in measured absorbed dose between film sheets, between film pieces within one sheet and between pixels in a ROI was highest for the OmniPro software and the lowest for FilmQA Pro. Evaluation of the inherent properties of EBT3 film showed that the relative deviations under different measurement conditions were ≤ 1 %. In measurement with different calibration phantom materials, i.e., a solid water phantom slab versus a plastic phantom, in which the plastic phantom returned 5 % higher absorbed dose. Finally, the absorbed dose measured under the same conditions as a cell flask exposed to 98 MU (corresponds to 1.0 Gy at the surface) was measured to 1.05 Gy when the flask was fully filled with water and 0.94 Gy when the flask was filled with 5 ml water.

Conclusions
Film dosimetry is a reliable method with high spatial resolution which is expected to work well for measurement of absorbed dose in cell exposure applications. The basic tests were satisfactory, and the inherent variations in radiation response were modest. The depth dose measurements compared to ion chamber measurements implied that film measurements returned the expected absorbed dose using at 200 kV, and this was validated by Monte Carlo simulations. The use of FilmQA Pro appeared to be optimal in this context, and this program is also recommended for analysis by the EBT3 manufacturer due to the use of accurate multi- channel dosimetry. After ensuring accurate measurement of the absorbed dose the cell
irradiation experiments was started. (Less)
Popular Abstract (Swedish)
Inom strålbehandling innebär den s.k. åskådareffekten ("bystander effect") ett relativt nytt tankesätt som betonar de biologiska effekterna av strålning på icke-bestrålade celler i närheten av bestrålade celler. Denna effekt har visat sig påverka inte bara de celler som angränsar till det bestrålade området utan även celler på större avstånd. I Lund pågår just nu ett projekt där man vill undersöka dessa effekter närmare. Användning av intensitetsmodulerad strålning är en av flera viktiga faktorer som måste utvärderas i undersökningar av hur celler påverkar varandra när de exponeras för strålning med låga och höga doshastigheter.

Syftet med denna studie är att etablera en bra och praktisk dosimetrisk metod för mätning av den absorberade... (More)
Inom strålbehandling innebär den s.k. åskådareffekten ("bystander effect") ett relativt nytt tankesätt som betonar de biologiska effekterna av strålning på icke-bestrålade celler i närheten av bestrålade celler. Denna effekt har visat sig påverka inte bara de celler som angränsar till det bestrålade området utan även celler på större avstånd. I Lund pågår just nu ett projekt där man vill undersöka dessa effekter närmare. Användning av intensitetsmodulerad strålning är en av flera viktiga faktorer som måste utvärderas i undersökningar av hur celler påverkar varandra när de exponeras för strålning med låga och höga doshastigheter.

Syftet med denna studie är att etablera en bra och praktisk dosimetrisk metod för mätning av den absorberade dosen till cellkulturer i olika geometriska uppställningar med bestrålade och skärmade celler. För att kunna ta fram förbättrade strålningsgeometrier med mer noggrann dosimetri krävs specifika dosimetriska genomförbarhetsstudier under motsvarande förhållanden. Inför sådana mätningar måste man noggrant överväga lämplig metod och val av dosimeter.

Alla bestrålningsexperiment i denna studie genomfördes med en röntgenapparat vid Skånes universitetssjukhus i Lund vid röntgenspänningar på 120 kV och 200 kV. Film av typen Gafchromic EBT3 användes för mätning av den absorberade dosen. Olika mätningar utfördes för att förstå filmens struktur och konstruktionsegenskaperna och hur dessa faktorer påverkade strålningsresponsen. För analys av filmmätningarna utvärderades tre olika program, d.v.s. OmniPro program, ett eget tillverkat Matlab-program kallat FILMGUI och FilmQA Pro program. Efter att ha säkerställt en procedur för noggrann mätning av den absorberade dosen bestrålades cellkulturer.

Filmdosimetri är en pålitlig metod med hög spatial upplösning som fungerar bra för mätning av absorberad dos. Olika analysprogram undersöktes i detta arbete, och resultaten av denna jämförelse visade att man kan mäta den absorberade dosen med stor noggrannhet. Flera fördelar erhölls vid användning av FilmQA Pro, som också rekommenderades av tillverkaren av EBT3-filmerna. En väsentlig orsak till att detta program ger hög noggrannhet är att det
använder sig av flerkanalsdosimetri. (Less)
Please use this url to cite or link to this publication:
author
Hossein, Zeinab
supervisor
organization
course
MSFT01 20151
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
7865568
date added to LUP
2015-09-13 12:25:02
date last changed
2017-01-09 16:32:08
@misc{7865568,
  abstract     = {Purpose
Intensity modulation of radiation is one of several important conditions to evaluate for full understanding of how cells involved in the bystander effect influence each other when cells are exposed to radiation at low and high dose rates. The aim of this study was to develop and apply a useful and practical dosimetric method for measurement of the absorbed dose to cell cultures exposed to intensity modulated radiation in investigations of the bystander effects.

Material and methods
All irradiations in this study were performed using an orthovoltage x-ray unit at Skåne University Hospital in Lund using 120 kV and 200 kV. Film dosimetry using Gafchromic EBT3 type film was the method of choice for measurement of the absorbed dose. A number of measurements were performed to understand the basic properties of the film with respect to radiation response, including inter- and intra-individual film sheet variations. Furthermore, the effect of different scattering conditions was investigated, including the use of different calibration phantom materials and the amount of nutrition medium in the cell culture flask. Dose calibrations were carried out and to evaluate if the film calibration datasets returned the expected absorbed dose at different dose levels, a depth dose measurement was performed which was compared with ion chamber measurements. For dosimetric analysis of film measurements, three different software tools were evaluated, i.e., (i) the OmniPro software,
(ii) a locally developed MATLAB program called FILMGUI and (iii) the FilmQA Pro software.

Results
Generally, the variations in measured absorbed dose between film sheets, between film pieces within one sheet and between pixels in a ROI was highest for the OmniPro software and the lowest for FilmQA Pro. Evaluation of the inherent properties of EBT3 film showed that the relative deviations under different measurement conditions were ≤ 1 %. In measurement with different calibration phantom materials, i.e., a solid water phantom slab versus a plastic phantom, in which the plastic phantom returned 5 % higher absorbed dose. Finally, the absorbed dose measured under the same conditions as a cell flask exposed to 98 MU (corresponds to 1.0 Gy at the surface) was measured to 1.05 Gy when the flask was fully filled with water and 0.94 Gy when the flask was filled with 5 ml water.

Conclusions
Film dosimetry is a reliable method with high spatial resolution which is expected to work well for measurement of absorbed dose in cell exposure applications. The basic tests were satisfactory, and the inherent variations in radiation response were modest. The depth dose measurements compared to ion chamber measurements implied that film measurements returned the expected absorbed dose using at 200 kV, and this was validated by Monte Carlo simulations. The use of FilmQA Pro appeared to be optimal in this context, and this program is also recommended for analysis by the EBT3 manufacturer due to the use of accurate multi- channel dosimetry. After ensuring accurate measurement of the absorbed dose the cell
irradiation experiments was started.},
  author       = {Hossein, Zeinab},
  language     = {eng},
  note         = {Student Paper},
  title        = {Radiochromic Film Dosimetry in Kilovoltage X-­‐ray Beams: A Pre-­‐ Investigation for In Vitro Studies of Bystander Effects},
  year         = {2015},
}