open access

Vol 23, No 2 (2018)
Original research articles
Published online: 2018-03-01
Submitted: 2017-11-06
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High accuracy dosimetry with small pieces of Gafchromic films

Ryszard Dąbrowski, Izabela Drozdyk, Paweł Kukołowicz
DOI: 10.1016/j.rpor.2018.01.001
·
Rep Pract Oncol Radiother 2018;23(2):114-120.

open access

Vol 23, No 2 (2018)
Original research articles
Published online: 2018-03-01
Submitted: 2017-11-06

Abstract

Aim

To investigate the influence of several factors on the accuracy of dose measurements and feasibility of application of small Gafchromic detectors for postal audit.

Background

Our experience showed that precision of dose measurements with small pieces of Gafchromic films may be significantly improved.

Materials and methods

Gafchromic films with dimensions of 1[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]1, 2[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]2 and 3[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]3[[ce:hsp sp="0.25"/]]cm2 were exposed to 6[[ce:hsp sp="0.25"/]]MV X-rays at dose levels of 50[[ce:hsp sp="0.25"/]]cGy-210[[ce:hsp sp="0.25"/]]cGy. The single- and multichannel methods (MM) were used for dose measurements. Detectors were scanned with an Epson V750PRO flatbed colour scanner. For 1[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]1 and larger detector sizes, separate calibration curves were established. The influence of the following factors was investigated: the heterogeneity of Gafchromic detectors group for single- and MM, ambient thermal detector conditions, the dose delivered on the measurement accuracy, application of two separate calibration curves for the smallest and larger pieces of films.

Results

The MM improves significantly the precision of dose measurement. The uncertainty attributed to detector active layer differences and scanner instabilities was about 1[[ce:hsp sp="0.25"/]]cGy (1 StDev) regardless of dose and detector size. The ambient temperature of the environment in which films were stored after irradiation influenced the dose reading. Significant difference of transmission for detectors sized 1[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]1 and 2[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]2cm2 was observed. The maximal difference between applied dose and dose reading performed was 1.1%.

Conclusions

The MM with a scaling protocol leads to a very high precision of dose measurements. The ambient thermal detector environment causes significant changes of measured signal. The detector size has relevant impact on dose reading.

Abstract

Aim

To investigate the influence of several factors on the accuracy of dose measurements and feasibility of application of small Gafchromic detectors for postal audit.

Background

Our experience showed that precision of dose measurements with small pieces of Gafchromic films may be significantly improved.

Materials and methods

Gafchromic films with dimensions of 1[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]1, 2[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]2 and 3[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]3[[ce:hsp sp="0.25"/]]cm2 were exposed to 6[[ce:hsp sp="0.25"/]]MV X-rays at dose levels of 50[[ce:hsp sp="0.25"/]]cGy-210[[ce:hsp sp="0.25"/]]cGy. The single- and multichannel methods (MM) were used for dose measurements. Detectors were scanned with an Epson V750PRO flatbed colour scanner. For 1[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]1 and larger detector sizes, separate calibration curves were established. The influence of the following factors was investigated: the heterogeneity of Gafchromic detectors group for single- and MM, ambient thermal detector conditions, the dose delivered on the measurement accuracy, application of two separate calibration curves for the smallest and larger pieces of films.

Results

The MM improves significantly the precision of dose measurement. The uncertainty attributed to detector active layer differences and scanner instabilities was about 1[[ce:hsp sp="0.25"/]]cGy (1 StDev) regardless of dose and detector size. The ambient temperature of the environment in which films were stored after irradiation influenced the dose reading. Significant difference of transmission for detectors sized 1[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]1 and 2[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]2cm2 was observed. The maximal difference between applied dose and dose reading performed was 1.1%.

Conclusions

The MM with a scaling protocol leads to a very high precision of dose measurements. The ambient thermal detector environment causes significant changes of measured signal. The detector size has relevant impact on dose reading.

Get Citation

Keywords

Gafchromic films; Multichannel method; High precision measurements; Postal dosimetry audit

About this article
Title

High accuracy dosimetry with small pieces of Gafchromic films

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 23, No 2 (2018)

Pages

114-120

Published online

2018-03-01

DOI

10.1016/j.rpor.2018.01.001

Bibliographic record

Rep Pract Oncol Radiother 2018;23(2):114-120.

Keywords

Gafchromic films
Multichannel method
High precision measurements
Postal dosimetry audit

Authors

Ryszard Dąbrowski
Izabela Drozdyk
Paweł Kukołowicz

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