open access

Vol 25, No 2 (2020)
Original research articles
Published online: 2020-03-01
Submitted: 2019-04-02
Get Citation

Prospective evaluation of the setup errors and its impact on safety margin for cervical cancer pelvic conformal radiotherapy

Avinash Badajena, Vijay Parshuram Raturi, Kirti Sirvastava, Hidehiro Hojo, Hajime Ohyoshi, Yanping Bei, Toshiya Rachi, Chen-Ta Wu, Taku Tochinai, Masayuki Okumura, Haiqin Zhang, Hirotaki Kouta, Pragya Verma, Geeta Singh, Abhishek Anand, Anjali Sachan
DOI: 10.1016/j.rpor.2020.02.006
·
Rep Pract Oncol Radiother 2020;25(2):260-265.

open access

Vol 25, No 2 (2020)
Original research articles
Published online: 2020-03-01
Submitted: 2019-04-02

Abstract

Aim

The primary objective was to assess set-up errors (SE) and secondary objective was to determine optimal safety margin (SM)

Background

To evaluate the SE and its impact on the SM utilizing electronic portal imaging (EPI) for pelvic conformal radiotherapy.

Material and methods

20 cervical cancer patients were enrolled in this prospective study. Supine position with ankle and knee rest was used during CT simulation. The contouring was done using consensus guideline for intact uterus. 50 Gy in 25 fractions were delivered at the isocenter with ≥95% PTV coverage. Two orthogonal (Anterior and Lateral) digitally reconstructed radiograph (DRR) was constructed as a reference image. The pair of orthogonal [Anterior-Posterior and Right Lateral] single exposure EPIs during radiation was taken. The reference DRR and EPIs were compared for shifts, and SE was calculated in the X-axis, Y-axis, and Z-axis directions.

Results

320 images (40 DRRs and 280 EPIs) were assessed. The systematic error in the Z-axis (AP EPI), X-axis (AP EPI), and Y-axis (Lat EPI) ranged from -12.0 to 11.8 mm, -10.3 to 7.5 mm, and -8.50 to 9.70 mm, while the random error ranged from 1.60 to 6.15 mm, 0.59 to 4.93 mm, and 1.02 to –4.35 mm. The SM computed were 7.07, 6.36, and 7.79 mm in the Y-axis, X-axis, and Z-axis by Van Herk’s equation, and 6.0, 5.51, and 6.74 mm by Stroom’s equation.

Conclusion

The computed SE helps defining SM, and it may differ between institutions. In our study, the calculated SM was approximately 8 mm in the Z-axis, 7 mm in X and Y axis for pelvic conformal radiotherapy.

Abstract

Aim

The primary objective was to assess set-up errors (SE) and secondary objective was to determine optimal safety margin (SM)

Background

To evaluate the SE and its impact on the SM utilizing electronic portal imaging (EPI) for pelvic conformal radiotherapy.

Material and methods

20 cervical cancer patients were enrolled in this prospective study. Supine position with ankle and knee rest was used during CT simulation. The contouring was done using consensus guideline for intact uterus. 50 Gy in 25 fractions were delivered at the isocenter with ≥95% PTV coverage. Two orthogonal (Anterior and Lateral) digitally reconstructed radiograph (DRR) was constructed as a reference image. The pair of orthogonal [Anterior-Posterior and Right Lateral] single exposure EPIs during radiation was taken. The reference DRR and EPIs were compared for shifts, and SE was calculated in the X-axis, Y-axis, and Z-axis directions.

Results

320 images (40 DRRs and 280 EPIs) were assessed. The systematic error in the Z-axis (AP EPI), X-axis (AP EPI), and Y-axis (Lat EPI) ranged from -12.0 to 11.8 mm, -10.3 to 7.5 mm, and -8.50 to 9.70 mm, while the random error ranged from 1.60 to 6.15 mm, 0.59 to 4.93 mm, and 1.02 to –4.35 mm. The SM computed were 7.07, 6.36, and 7.79 mm in the Y-axis, X-axis, and Z-axis by Van Herk’s equation, and 6.0, 5.51, and 6.74 mm by Stroom’s equation.

Conclusion

The computed SE helps defining SM, and it may differ between institutions. In our study, the calculated SM was approximately 8 mm in the Z-axis, 7 mm in X and Y axis for pelvic conformal radiotherapy.

Get Citation

Keywords

Set-up errors; Set-up margin; Pelvic conformal radiotherapy

About this article
Title

Prospective evaluation of the setup errors and its impact on safety margin for cervical cancer pelvic conformal radiotherapy

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 25, No 2 (2020)

Pages

260-265

Published online

2020-03-01

DOI

10.1016/j.rpor.2020.02.006

Bibliographic record

Rep Pract Oncol Radiother 2020;25(2):260-265.

Keywords

Set-up errors
Set-up margin
Pelvic conformal radiotherapy

Authors

Avinash Badajena
Vijay Parshuram Raturi
Kirti Sirvastava
Hidehiro Hojo
Hajime Ohyoshi
Yanping Bei
Toshiya Rachi
Chen-Ta Wu
Taku Tochinai
Masayuki Okumura
Haiqin Zhang
Hirotaki Kouta
Pragya Verma
Geeta Singh
Abhishek Anand
Anjali Sachan

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