open access

Vol 20, No 4 (2015)
Original research articles
Published online: 2015-07-01
Submitted: 2014-06-04
Get Citation

Effects of remedies made in patient setup process on residual setup errors and margins in head and neck cancer radiotherapy based on 2D image guidance

Mika Kapanen, Marko Laaksomaa, Tapio Tulijoki, Pirkko-Liisa Kellokumpu-Lehtinen, Simo Hyödynmaa
DOI: 10.1016/j.rpor.2015.03.002
·
Rep Pract Oncol Radiother 2015;20(4):292-298.

open access

Vol 20, No 4 (2015)
Original research articles
Published online: 2015-07-01
Submitted: 2014-06-04

Abstract

Aim

Patient setup errors were aimed to be reduced in radiotherapy (RT) of head-and-neck (H&N) cancer. Some remedies in patient setup procedure were proposed for this purpose.

Background

RT of H&N cancer has challenges due to patient rotation and flexible anatomy. Residual position errors occurring in treatment situation and required setup margins were estimated for relevant bony landmarks after the remedies made in setup process and compared with previous results.

Materials and methods

The formation process for thermoplastic masks was improved. Also image matching was harmonized to the vertebrae in the middle of the target and a 5[[ce:hsp sp="0.25"/]]mm threshold was introduced for immediate correction of systematic errors of the landmarks. After the remedies, residual position errors of bony landmarks were retrospectively determined from 748 orthogonal X-ray images of 40 H&N cancer patients. The landmarks were the vertebrae C1–2, C5–7, the occiput bone and the mandible. The errors include contributions from patient rotation, flexible anatomy and inter-observer variation in image matching. Setup margins (3D) were calculated with the Van Herk formula.

Results

Systematic residual errors of the landmarks were reduced maximally by 49.8% (p[[ce:hsp sp="0.25"/]]≤[[ce:hsp sp="0.25"/]]0.05) and the margins by 3.1[[ce:hsp sp="0.25"/]]mm after the remedies. With daily image guidance the setup margins of the landmarks were within 4.4[[ce:hsp sp="0.25"/]]mm, but larger margins of 6.4[[ce:hsp sp="0.25"/]]mm were required for the mandible.

Conclusions

Remarkable decrease in the residual errors of the bony landmarks and setup margins were achieved through the remedies made in the setup process. The importance of quality assurance of the setup process was demonstrated.

Abstract

Aim

Patient setup errors were aimed to be reduced in radiotherapy (RT) of head-and-neck (H&N) cancer. Some remedies in patient setup procedure were proposed for this purpose.

Background

RT of H&N cancer has challenges due to patient rotation and flexible anatomy. Residual position errors occurring in treatment situation and required setup margins were estimated for relevant bony landmarks after the remedies made in setup process and compared with previous results.

Materials and methods

The formation process for thermoplastic masks was improved. Also image matching was harmonized to the vertebrae in the middle of the target and a 5[[ce:hsp sp="0.25"/]]mm threshold was introduced for immediate correction of systematic errors of the landmarks. After the remedies, residual position errors of bony landmarks were retrospectively determined from 748 orthogonal X-ray images of 40 H&N cancer patients. The landmarks were the vertebrae C1–2, C5–7, the occiput bone and the mandible. The errors include contributions from patient rotation, flexible anatomy and inter-observer variation in image matching. Setup margins (3D) were calculated with the Van Herk formula.

Results

Systematic residual errors of the landmarks were reduced maximally by 49.8% (p[[ce:hsp sp="0.25"/]]≤[[ce:hsp sp="0.25"/]]0.05) and the margins by 3.1[[ce:hsp sp="0.25"/]]mm after the remedies. With daily image guidance the setup margins of the landmarks were within 4.4[[ce:hsp sp="0.25"/]]mm, but larger margins of 6.4[[ce:hsp sp="0.25"/]]mm were required for the mandible.

Conclusions

Remarkable decrease in the residual errors of the bony landmarks and setup margins were achieved through the remedies made in the setup process. The importance of quality assurance of the setup process was demonstrated.

Get Citation

Keywords

Radiotherapy; Head and neck cancer; Patient setup; Image guidance; Setup margins

About this article
Title

Effects of remedies made in patient setup process on residual setup errors and margins in head and neck cancer radiotherapy based on 2D image guidance

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 20, No 4 (2015)

Pages

292-298

Published online

2015-07-01

DOI

10.1016/j.rpor.2015.03.002

Bibliographic record

Rep Pract Oncol Radiother 2015;20(4):292-298.

Keywords

Radiotherapy
Head and neck cancer
Patient setup
Image guidance
Setup margins

Authors

Mika Kapanen
Marko Laaksomaa
Tapio Tulijoki
Pirkko-Liisa Kellokumpu-Lehtinen
Simo Hyödynmaa

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