open access

Vol 19, No 6 (2014)
Original research articles
Published online: 2014-11-01
Submitted: 2013-12-03
Get Citation

Estimation of optimal matching position for orthogonal kV setup images and minimal setup margins in radiotherapy of whole breast and lymph node areas

Marko Laaksomaa, Mika Kapanen, Tanja Skyttä, Seppo Peltola, Simo Hyödynmaa, Pirkko-Liisa Kellokumpu-Lehtinen
DOI: 10.1016/j.rpor.2014.05.001
·
Rep Pract Oncol Radiother 2014;19(6):369-375.

open access

Vol 19, No 6 (2014)
Original research articles
Published online: 2014-11-01
Submitted: 2013-12-03

Abstract

Aim

The aim was to find an optimal setup image matching position and minimal setup margins to maximally spare the organs at risk in breast radiotherapy.

Background

Radiotherapy of breast cancer is a routine task but has many challenges. We investigated residual position errors in whole breast radiotherapy when orthogonal setup images were matched to different bony landmarks.

Materials and methods

A total of 1111 orthogonal setup image pairs and tangential field images were analyzed retrospectively for 50 consecutive patients. Residual errors in the treatment field images were determined by matching the orthogonal setup images to the vertebrae, sternum, ribs and their compromises. The most important region was the chest wall as it is crucial for the dose delivered to the heart and the ipsilateral lung. Inter-observer variation in online image matching was investigated.

Results

The best general image matching position was the compromise of the vertebrae, ribs and sternum, while the worst position was the vertebrae alone (p[[ce:hsp sp="0.25"/]]≤[[ce:hsp sp="0.25"/]]0.03). The setup margins required for the chest wall varied from 4.3[[ce:hsp sp="0.25"/]]mm to 5.5[[ce:hsp sp="0.25"/]]mm in the lung direction while in the superior–inferior (SI) direction the margins varied from 5.1[[ce:hsp sp="0.25"/]]mm to 7.6[[ce:hsp sp="0.25"/]]mm. The inter-observer variation increased the minimal margins by approximately 1[[ce:hsp sp="0.25"/]]mm. The margin of the lymph node areas should be at least 4.8[[ce:hsp sp="0.25"/]]mm.

Conclusions

Setup margins can be reduced by proper selection of a matching position for the orthogonal setup images. To retain the minimal margins sufficient, systematic error of the chest wall should not exceed 4[[ce:hsp sp="0.25"/]]mm in the tangential field image.

Abstract

Aim

The aim was to find an optimal setup image matching position and minimal setup margins to maximally spare the organs at risk in breast radiotherapy.

Background

Radiotherapy of breast cancer is a routine task but has many challenges. We investigated residual position errors in whole breast radiotherapy when orthogonal setup images were matched to different bony landmarks.

Materials and methods

A total of 1111 orthogonal setup image pairs and tangential field images were analyzed retrospectively for 50 consecutive patients. Residual errors in the treatment field images were determined by matching the orthogonal setup images to the vertebrae, sternum, ribs and their compromises. The most important region was the chest wall as it is crucial for the dose delivered to the heart and the ipsilateral lung. Inter-observer variation in online image matching was investigated.

Results

The best general image matching position was the compromise of the vertebrae, ribs and sternum, while the worst position was the vertebrae alone (p[[ce:hsp sp="0.25"/]]≤[[ce:hsp sp="0.25"/]]0.03). The setup margins required for the chest wall varied from 4.3[[ce:hsp sp="0.25"/]]mm to 5.5[[ce:hsp sp="0.25"/]]mm in the lung direction while in the superior–inferior (SI) direction the margins varied from 5.1[[ce:hsp sp="0.25"/]]mm to 7.6[[ce:hsp sp="0.25"/]]mm. The inter-observer variation increased the minimal margins by approximately 1[[ce:hsp sp="0.25"/]]mm. The margin of the lymph node areas should be at least 4.8[[ce:hsp sp="0.25"/]]mm.

Conclusions

Setup margins can be reduced by proper selection of a matching position for the orthogonal setup images. To retain the minimal margins sufficient, systematic error of the chest wall should not exceed 4[[ce:hsp sp="0.25"/]]mm in the tangential field image.

Get Citation

Keywords

Radiotherapy; Breast cancer; Setup errors; Image guidance; Setup margins; Free breathing

About this article
Title

Estimation of optimal matching position for orthogonal kV setup images and minimal setup margins in radiotherapy of whole breast and lymph node areas

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 19, No 6 (2014)

Pages

369-375

Published online

2014-11-01

DOI

10.1016/j.rpor.2014.05.001

Bibliographic record

Rep Pract Oncol Radiother 2014;19(6):369-375.

Keywords

Radiotherapy
Breast cancer
Setup errors
Image guidance
Setup margins
Free breathing

Authors

Marko Laaksomaa
Mika Kapanen
Tanja Skyttä
Seppo Peltola
Simo Hyödynmaa
Pirkko-Liisa Kellokumpu-Lehtinen

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