open access

Vol 18, No 2 (2013)
Original research articles
Published online: 2013-03-01
Submitted: 2012-03-20
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Pretreatment verification of dose calculation and delivery by means of measurements with PLEXITOM™ phantom

Paweł Wołowiec, Paweł Kukołowicz, Krzysztof Lis
DOI: 10.1016/j.rpor.2012.12.007
·
Rep Pract Oncol Radiother 2013;18(2):95-100.

open access

Vol 18, No 2 (2013)
Original research articles
Published online: 2013-03-01
Submitted: 2012-03-20

Abstract

Aim

To validate a pretreatment verification method of dose calculation and dose delivery based on measurements with Metaplex PTW phantom.

Background

The dose-response relationships for local tumor control and radiosensitive tissue complications are strong. It is widely accepted that an accuracy of dose delivery of about 3.5% (one standard deviation) is required in modern radiotherapy. This goal is difficult to achieve. This paper describes our experience with the control of dose delivery and calculations at the ICRU reference point.

Materials and methods

The calculations of dose at the ICRU reference point performed with the treatment planning system CMS XiO were checked by measurements carried out in the PLEXITOM™ phantom.

All measurements were performed with the ion chamber positioned in the phantom, at the central axis of the beam, at depth equivalent to the radiological depth (at gantry zero position). The source-to-phantom surface distance was always set to keep the source-to-detector distance equal to the reference point depth defined in the ICRU Report 50 (generally, 100[[ce:hsp sp="0.25"/]]cm). The dose was measured according to IAEA TRS 398 report for measurements in solid phantoms. The measurement results were corrected with the actual accelerator's output factor and for the non-full scatter conditions. Measurements were made for 111 patients and 327 fields.

Results

The average differences between measurements and calculations were 0.03% (SD[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]1.4%), 0.3% (SD[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]1.0%), 0.1% (SD[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]1.1%), 0.6% (SD[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]1.8%), 0.3% (SD[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]1.5%) for all measurements, for total dose, for pelvis, thorax and H&N patients, respectively. Only in 15 cases (4.6%), the difference between the measured and the calculated dose was greater than 3%. For these fields, a detailed analysis was undertaken.

Conclusion

The verification method provides an instantaneous verification of dose calculations before the beginning of a patient's treatment. It allows to detect differences smaller than 3.5%.

Abstract

Aim

To validate a pretreatment verification method of dose calculation and dose delivery based on measurements with Metaplex PTW phantom.

Background

The dose-response relationships for local tumor control and radiosensitive tissue complications are strong. It is widely accepted that an accuracy of dose delivery of about 3.5% (one standard deviation) is required in modern radiotherapy. This goal is difficult to achieve. This paper describes our experience with the control of dose delivery and calculations at the ICRU reference point.

Materials and methods

The calculations of dose at the ICRU reference point performed with the treatment planning system CMS XiO were checked by measurements carried out in the PLEXITOM™ phantom.

All measurements were performed with the ion chamber positioned in the phantom, at the central axis of the beam, at depth equivalent to the radiological depth (at gantry zero position). The source-to-phantom surface distance was always set to keep the source-to-detector distance equal to the reference point depth defined in the ICRU Report 50 (generally, 100[[ce:hsp sp="0.25"/]]cm). The dose was measured according to IAEA TRS 398 report for measurements in solid phantoms. The measurement results were corrected with the actual accelerator's output factor and for the non-full scatter conditions. Measurements were made for 111 patients and 327 fields.

Results

The average differences between measurements and calculations were 0.03% (SD[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]1.4%), 0.3% (SD[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]1.0%), 0.1% (SD[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]1.1%), 0.6% (SD[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]1.8%), 0.3% (SD[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]1.5%) for all measurements, for total dose, for pelvis, thorax and H&N patients, respectively. Only in 15 cases (4.6%), the difference between the measured and the calculated dose was greater than 3%. For these fields, a detailed analysis was undertaken.

Conclusion

The verification method provides an instantaneous verification of dose calculations before the beginning of a patient's treatment. It allows to detect differences smaller than 3.5%.

Get Citation

Keywords

Radiotherapy; Quality control; Treatment plan verification; PLEXITOM™

About this article
Title

Pretreatment verification of dose calculation and delivery by means of measurements with PLEXITOM™ phantom

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 18, No 2 (2013)

Pages

95-100

Published online

2013-03-01

DOI

10.1016/j.rpor.2012.12.007

Bibliographic record

Rep Pract Oncol Radiother 2013;18(2):95-100.

Keywords

Radiotherapy
Quality control
Treatment plan verification
PLEXITOM™

Authors

Paweł Wołowiec
Paweł Kukołowicz
Krzysztof Lis

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