open access

Vol 24, No 6 (2019)
Original research articles
Published online: 2019-11-01
Submitted: 2019-06-03
Get Citation

Dosimetric impact of uncorrected systematic yaw rotation in VMAT for peripheral lung SABR

Sarah Barrett, Pierre Thirion, Dean Harper, Andrew J. Simpkin, Michelle Leech, Kim Hickey, Laoise Ryan, Laure Marignol
DOI: 10.1016/j.rpor.2019.07.010
·
Rep Pract Oncol Radiother 2019;24(6):520-527.

open access

Vol 24, No 6 (2019)
Original research articles
Published online: 2019-11-01
Submitted: 2019-06-03

Abstract

Aim

This study aimed to evaluate the dosimetric impact of uncorrected yaw rotational error on both target coverage and OAR dose metrics in this patient population.

Background

Rotational set up errors can be difficult to correct in lung VMAT SABR treatments, and may lead to a change in planned dose distributions.

Materials and methods

We retrospectively applied systematic yaw rotational errors in 1° degree increments up to −5° and +5° degrees in 16 VMAT SABR plans. The impact on PTV and OARs (oesophagus, spinal canal, heart, airway, chest wall, brachial plexus, lung) was evaluated using a variety of dose metrics. Changes were assessed in relation to percentage deviation from approved planned dose at 0 degrees.

Results

Target coverage was largely unaffected with the largest mean and maximum percentage difference being 1.4% and 6% respectively to PTV D98% at +5 degrees yaw.

Impact on OARs was varied. Minimal impact was observed in oesophagus, spinal canal, chest wall or lung dose metrics. Larger variations were observed in the heart, airway and brachial plexus. The largest mean and maximum percentage differences being 20.77% and 311% respectively at −5 degrees yaw to airway D0.1cc, however, the clinical impact was negligible as these variations were observed in metrics with minimal initial doses.

Conclusions

No clinically unacceptable changes to dose metrics were observed in this patient cohort but large percentage deviations from approved dose metrics in OARs were noted. OARs with associated PRV structures appear more robust to uncorrected rotational error.

Abstract

Aim

This study aimed to evaluate the dosimetric impact of uncorrected yaw rotational error on both target coverage and OAR dose metrics in this patient population.

Background

Rotational set up errors can be difficult to correct in lung VMAT SABR treatments, and may lead to a change in planned dose distributions.

Materials and methods

We retrospectively applied systematic yaw rotational errors in 1° degree increments up to −5° and +5° degrees in 16 VMAT SABR plans. The impact on PTV and OARs (oesophagus, spinal canal, heart, airway, chest wall, brachial plexus, lung) was evaluated using a variety of dose metrics. Changes were assessed in relation to percentage deviation from approved planned dose at 0 degrees.

Results

Target coverage was largely unaffected with the largest mean and maximum percentage difference being 1.4% and 6% respectively to PTV D98% at +5 degrees yaw.

Impact on OARs was varied. Minimal impact was observed in oesophagus, spinal canal, chest wall or lung dose metrics. Larger variations were observed in the heart, airway and brachial plexus. The largest mean and maximum percentage differences being 20.77% and 311% respectively at −5 degrees yaw to airway D0.1cc, however, the clinical impact was negligible as these variations were observed in metrics with minimal initial doses.

Conclusions

No clinically unacceptable changes to dose metrics were observed in this patient cohort but large percentage deviations from approved dose metrics in OARs were noted. OARs with associated PRV structures appear more robust to uncorrected rotational error.

Get Citation

Keywords

Lung SABR; VMAT; Setup error; Rotational error

About this article
Title

Dosimetric impact of uncorrected systematic yaw rotation in VMAT for peripheral lung SABR

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 24, No 6 (2019)

Pages

520-527

Published online

2019-11-01

DOI

10.1016/j.rpor.2019.07.010

Bibliographic record

Rep Pract Oncol Radiother 2019;24(6):520-527.

Keywords

Lung SABR
VMAT
Setup error
Rotational error

Authors

Sarah Barrett
Pierre Thirion
Dean Harper
Andrew J. Simpkin
Michelle Leech
Kim Hickey
Laoise Ryan
Laure Marignol

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