Polarity effect on surface dose measurement for an attix parallel plate ionisation chamber

M. J. Butson; P. K. N. Yu; T. Cheung

doi:10.1007/bf03178463

Polarity effect on surface dose measurement for an attix parallel plate ionisation chamber

M. J. Butson^*, P. K. N. Yu, T. Cheung

^*Corresponding author for this work

Research output: Journal Publications and Reviews › RGC 21 - Publication in refereed journal › peer-review

6 Citations (Scopus)

Abstract

The effects of chamber polarity have been investigated for the measurement of 6MV and 18MV x-ray surface dose using a parallel plate ionization chamber. Results have shown that a significant difference in measured ionization is recorded between polarities at 6MV and 18MV at the phantom surface. A polarity ratio ranging from 1.062 to 1.005 is seen for 6MV x-rays at the phantom surface for field sizes 5cm × 5cm to 40cm × 40cm when comparing positive to negative polarity. These ratio's range from 1.024 to 1.004 for 18MV x-rays with the same field sizes. When these charge reading are compared to the D_max readings of the same polarity it is found that these polarity effects are minimal for the calculation of percentage dose results with variations being less than 1% of maximum.

Original language	English
Pages (from-to)	84-86
Journal	Australasian Physical and Engineering Sciences in Medicine
Volume	26
Issue number	2
DOIs	https://doi.org/10.1007/bf03178463
Publication status	Published - Jun 2003

Research Keywords

Polarity
Radiotherapy
Surface dose

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title = "Polarity effect on surface dose measurement for an attix parallel plate ionisation chamber",

abstract = "The effects of chamber polarity have been investigated for the measurement of 6MV and 18MV x-ray surface dose using a parallel plate ionization chamber. Results have shown that a significant difference in measured ionization is recorded between polarities at 6MV and 18MV at the phantom surface. A polarity ratio ranging from 1.062 to 1.005 is seen for 6MV x-rays at the phantom surface for field sizes 5cm × 5cm to 40cm × 40cm when comparing positive to negative polarity. These ratio's range from 1.024 to 1.004 for 18MV x-rays with the same field sizes. When these charge reading are compared to the Dmax readings of the same polarity it is found that these polarity effects are minimal for the calculation of percentage dose results with variations being less than 1% of maximum.",

keywords = "Polarity, Radiotherapy, Surface dose",

author = "Butson, {M. J.} and Yu, {P. K. N.} and T. Cheung",

year = "2003",

month = jun,

doi = "10.1007/bf03178463",

language = "English",

volume = "26",

pages = "84--86",

journal = "Australasian Physical and Engineering Sciences in Medicine",

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publisher = "Australasian Coll. of Phys. Scientists and Engineers",

number = "2",

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TY - JOUR

T1 - Polarity effect on surface dose measurement for an attix parallel plate ionisation chamber

AU - Butson, M. J.

AU - Yu, P. K. N.

AU - Cheung, T.

PY - 2003/6

Y1 - 2003/6

N2 - The effects of chamber polarity have been investigated for the measurement of 6MV and 18MV x-ray surface dose using a parallel plate ionization chamber. Results have shown that a significant difference in measured ionization is recorded between polarities at 6MV and 18MV at the phantom surface. A polarity ratio ranging from 1.062 to 1.005 is seen for 6MV x-rays at the phantom surface for field sizes 5cm × 5cm to 40cm × 40cm when comparing positive to negative polarity. These ratio's range from 1.024 to 1.004 for 18MV x-rays with the same field sizes. When these charge reading are compared to the Dmax readings of the same polarity it is found that these polarity effects are minimal for the calculation of percentage dose results with variations being less than 1% of maximum.

AB - The effects of chamber polarity have been investigated for the measurement of 6MV and 18MV x-ray surface dose using a parallel plate ionization chamber. Results have shown that a significant difference in measured ionization is recorded between polarities at 6MV and 18MV at the phantom surface. A polarity ratio ranging from 1.062 to 1.005 is seen for 6MV x-rays at the phantom surface for field sizes 5cm × 5cm to 40cm × 40cm when comparing positive to negative polarity. These ratio's range from 1.024 to 1.004 for 18MV x-rays with the same field sizes. When these charge reading are compared to the Dmax readings of the same polarity it is found that these polarity effects are minimal for the calculation of percentage dose results with variations being less than 1% of maximum.

KW - Polarity

KW - Radiotherapy

KW - Surface dose

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U2 - 10.1007/bf03178463

DO - 10.1007/bf03178463

M3 - RGC 21 - Publication in refereed journal

C2 - 12956191

SN - 0158-9938

VL - 26

SP - 84

EP - 86

JO - Australasian Physical and Engineering Sciences in Medicine

JF - Australasian Physical and Engineering Sciences in Medicine

IS - 2

ER -

Polarity effect on surface dose measurement for an attix parallel plate ionisation chamber

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