open access

Vol 23, No 1 (2018)
Original research articles
Published online: 2018-01-01
Submitted: 2017-08-09
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Absorption ratio of treatment couch and effect on surface and build-up region doses

Taylan Tuğrul
DOI: 10.1016/j.rpor.2017.10.004
·
Rep Pract Oncol Radiother 2018;23(1):1-5.

open access

Vol 23, No 1 (2018)
Original research articles
Published online: 2018-01-01
Submitted: 2017-08-09

Abstract

Aim

In this study, at different fields, energies and gantry angles, treatment couch and rails dose absorption ratio and treatment couch effect on surface and build-up region doses were examined.

Background

It is assumed that radiation attenuation is minimal because the carbon fiber couches have low density and it is not generally accounted for during treatment planning. Consequently, it leads to a major dosimetric mistake.

Materials and methods

Solid water phantom was used for relative dose measurement. The measurements were done using a Farmer ion chamber with 0.6[[ce:hsp sp="0.25"/]]cc volume and a parallel plane ion chamber starting from surface with 1[[ce:hsp sp="0.25"/]]mm depth intervals at 10[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]10[[ce:hsp sp="0.25"/]]cm2 field, SSD 100[[ce:hsp sp="0.25"/]]cm. Measurements were taken for situations where the beams intersect the couch and couch rails.

Results

Dose absorption ratio of carbon fiber couch obtained at gantry angle of 180° was 1.52%, 0.69%, 0.33% and 0.25% at different field sizes for 6[[ce:hsp sp="0.25"/]]MV. For 15[[ce:hsp sp="0.25"/]]MV, this ratio was 0.95%, 0.27%, 0.20% and 0.05%. The absorption ratio is between 3.4% and 1.22% when the beams intersect with couch rails. The couch effect increased surface dose from 14% to 70% for 6[[ce:hsp sp="0.25"/]]MV and from 11.34% to 53.03% for 15[[ce:hsp sp="0.25"/]]MV.

Conclusions

The results showed that the carbon fiber couch increased surface dose during posterior irradiation. Therefore, the skin-sparing effect of the high energy beams was decreased. If the effect of couch is not considered, it may cause significant differences at dose which reaches the patient and may cause tissue problems such as erythema.

Abstract

Aim

In this study, at different fields, energies and gantry angles, treatment couch and rails dose absorption ratio and treatment couch effect on surface and build-up region doses were examined.

Background

It is assumed that radiation attenuation is minimal because the carbon fiber couches have low density and it is not generally accounted for during treatment planning. Consequently, it leads to a major dosimetric mistake.

Materials and methods

Solid water phantom was used for relative dose measurement. The measurements were done using a Farmer ion chamber with 0.6[[ce:hsp sp="0.25"/]]cc volume and a parallel plane ion chamber starting from surface with 1[[ce:hsp sp="0.25"/]]mm depth intervals at 10[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]10[[ce:hsp sp="0.25"/]]cm2 field, SSD 100[[ce:hsp sp="0.25"/]]cm. Measurements were taken for situations where the beams intersect the couch and couch rails.

Results

Dose absorption ratio of carbon fiber couch obtained at gantry angle of 180° was 1.52%, 0.69%, 0.33% and 0.25% at different field sizes for 6[[ce:hsp sp="0.25"/]]MV. For 15[[ce:hsp sp="0.25"/]]MV, this ratio was 0.95%, 0.27%, 0.20% and 0.05%. The absorption ratio is between 3.4% and 1.22% when the beams intersect with couch rails. The couch effect increased surface dose from 14% to 70% for 6[[ce:hsp sp="0.25"/]]MV and from 11.34% to 53.03% for 15[[ce:hsp sp="0.25"/]]MV.

Conclusions

The results showed that the carbon fiber couch increased surface dose during posterior irradiation. Therefore, the skin-sparing effect of the high energy beams was decreased. If the effect of couch is not considered, it may cause significant differences at dose which reaches the patient and may cause tissue problems such as erythema.

Get Citation

Keywords

Carbon fiber couch; Surface dose; Build-up region dose; Effect of couch

About this article
Title

Absorption ratio of treatment couch and effect on surface and build-up region doses

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 23, No 1 (2018)

Pages

1-5

Published online

2018-01-01

DOI

10.1016/j.rpor.2017.10.004

Bibliographic record

Rep Pract Oncol Radiother 2018;23(1):1-5.

Keywords

Carbon fiber couch
Surface dose
Build-up region dose
Effect of couch

Authors

Taylan Tuğrul

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