Mass-density compensation can improve the performance of a range of different detectors under non-equilibrium conditions.
Dosimeters often consist of several components whose mass densities differ substantially from water. These components cause small-field correction factors to vary significantly as lateral electronic equilibrium breaks down. Even amongst instruments designed for small-field dosimetry, inter-detector...
| Main Authors: | , , , |
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| Format: | Journal article |
| Language: | English |
| Published: |
2013
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| _version_ | 1826285036706463744 |
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| author | Underwood, T Winter, H Hill, M Fenwick, J |
| author_facet | Underwood, T Winter, H Hill, M Fenwick, J |
| author_sort | Underwood, T |
| collection | OXFORD |
| description | Dosimeters often consist of several components whose mass densities differ substantially from water. These components cause small-field correction factors to vary significantly as lateral electronic equilibrium breaks down. Even amongst instruments designed for small-field dosimetry, inter-detector variation in the correction factors associated with very small (∼0.5 cm) fields can amount to tens of per cent. For a given dosimeter, small-field correction factors vary not only with field size but also with detector azimuthal angle and position within the field. Furthermore the accurate determination of these factors typically requires time-intensive Monte Carlo simulations. Thus, if achievable, 'correction factor free' small-field dosimetry would be highly desirable. This study demonstrates that a new generation of mass-density compensated detectors could take us towards this goal. Using a 6 MV beam model, it shows that 'mass-density compensation' can be utilized to improve the performance of a range of different detectors under small-field conditions. Non-sensitive material of appropriate mass-density is incorporated into detector designs in order to make the instruments behave as if consisting only of water. The dosimeter perturbative effects are then reduced to those associated with volume averaging. An even better solution-which modifies detectors to obtain profiles that look like those measured by a point-like water structure-is also considered. Provided that adequate sensitivity can be achieved for a small measurement volume, this study shows that it may be possible to use mass-density compensation (and Monte Carlo-driven design) to produce a solid-state dosimeter/ionization chamber with a near-perfect non-equilibrium response. |
| first_indexed | 2024-03-07T01:22:51Z |
| format | Journal article |
| id | oxford-uuid:90f51993-a788-462d-be93-f4bc2bdcc41e |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T01:22:51Z |
| publishDate | 2013 |
| record_format | dspace |
| spelling | oxford-uuid:90f51993-a788-462d-be93-f4bc2bdcc41e2022-03-26T23:15:12ZMass-density compensation can improve the performance of a range of different detectors under non-equilibrium conditions.Journal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:90f51993-a788-462d-be93-f4bc2bdcc41eEnglishSymplectic Elements at Oxford2013Underwood, TWinter, HHill, MFenwick, JDosimeters often consist of several components whose mass densities differ substantially from water. These components cause small-field correction factors to vary significantly as lateral electronic equilibrium breaks down. Even amongst instruments designed for small-field dosimetry, inter-detector variation in the correction factors associated with very small (∼0.5 cm) fields can amount to tens of per cent. For a given dosimeter, small-field correction factors vary not only with field size but also with detector azimuthal angle and position within the field. Furthermore the accurate determination of these factors typically requires time-intensive Monte Carlo simulations. Thus, if achievable, 'correction factor free' small-field dosimetry would be highly desirable. This study demonstrates that a new generation of mass-density compensated detectors could take us towards this goal. Using a 6 MV beam model, it shows that 'mass-density compensation' can be utilized to improve the performance of a range of different detectors under small-field conditions. Non-sensitive material of appropriate mass-density is incorporated into detector designs in order to make the instruments behave as if consisting only of water. The dosimeter perturbative effects are then reduced to those associated with volume averaging. An even better solution-which modifies detectors to obtain profiles that look like those measured by a point-like water structure-is also considered. Provided that adequate sensitivity can be achieved for a small measurement volume, this study shows that it may be possible to use mass-density compensation (and Monte Carlo-driven design) to produce a solid-state dosimeter/ionization chamber with a near-perfect non-equilibrium response. |
| spellingShingle | Underwood, T Winter, H Hill, M Fenwick, J Mass-density compensation can improve the performance of a range of different detectors under non-equilibrium conditions. |
| title | Mass-density compensation can improve the performance of a range of different detectors under non-equilibrium conditions. |
| title_full | Mass-density compensation can improve the performance of a range of different detectors under non-equilibrium conditions. |
| title_fullStr | Mass-density compensation can improve the performance of a range of different detectors under non-equilibrium conditions. |
| title_full_unstemmed | Mass-density compensation can improve the performance of a range of different detectors under non-equilibrium conditions. |
| title_short | Mass-density compensation can improve the performance of a range of different detectors under non-equilibrium conditions. |
| title_sort | mass density compensation can improve the performance of a range of different detectors under non equilibrium conditions |
| work_keys_str_mv | AT underwoodt massdensitycompensationcanimprovetheperformanceofarangeofdifferentdetectorsundernonequilibriumconditions AT winterh massdensitycompensationcanimprovetheperformanceofarangeofdifferentdetectorsundernonequilibriumconditions AT hillm massdensitycompensationcanimprovetheperformanceofarangeofdifferentdetectorsundernonequilibriumconditions AT fenwickj massdensitycompensationcanimprovetheperformanceofarangeofdifferentdetectorsundernonequilibriumconditions |