open access

Vol 23, No 4 (2018)
Original research articles
Published online: 2018-07-01
Submitted: 2017-09-07
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Immobilization versus no immobilization for pelvic external beam radiotherapy

Avinash H. Udayashankar, Shibina Noorjahan, Nirmala Srikantia, K. Ravindra Babu, Sandeep Muzumder
DOI: 10.1016/j.rpor.2018.04.007
·
Rep Pract Oncol Radiother 2018;23(4):233-241.

open access

Vol 23, No 4 (2018)
Original research articles
Published online: 2018-07-01
Submitted: 2017-09-07

Abstract

Aim

To identify the most reproducible technique of patient positioning and immobilization during pelvic radiotherapy.

Background

Radiotherapy plays an important role in the treatment of pelvic malignancies. Errors in positioning of patient are an integral component of treatment. The present study compares two methods of immobilization with no immobilization with an aim of identifying the most reproducible method.

Materials and methods

65 consecutive patients receiving pelvic external beam radiotherapy were retrospectively analyzed. 30, 21 and 14 patients were treated with no-immobilization with a leg separator, whole body vacuum bag cushion (VBC) and six point aquaplast immobilization system, respectively. The systematic error, random error and the planning target volume (PTV) margins were calculated for all the three techniques and statistically analyzed.

Results

The systematic errors were the highest in the VBC and random errors were the highest in the aquaplast group. Both systematic and random errors were the lowest in patients treated with no-immobilization. 3D Systematic error (mm, mean±1SD) was 4.31±3.84, 3.39±1.71 and 2.42±0.97 for VBC, aquaplast and no-immobilization, respectively. 3D random error (mm, 1SD) was 2.96, 3.59 and 1.39 for VBC, aquaplast and no-immobilization, respectively. The differences were statistically significant between all the three groups. The calculated PTV margins were the smallest for the no-immobilization technique with 4.56, 4.69 and 4.59mm, respectively, in x, y and z axes, respectively.

Conclusions

Among the three techniques, no-immobilization technique with leg separator was the most reproducible technique with the smallest PTV margins. For obvious reasons, this technique is the least time consuming and most economically viable in developing countries.

Abstract

Aim

To identify the most reproducible technique of patient positioning and immobilization during pelvic radiotherapy.

Background

Radiotherapy plays an important role in the treatment of pelvic malignancies. Errors in positioning of patient are an integral component of treatment. The present study compares two methods of immobilization with no immobilization with an aim of identifying the most reproducible method.

Materials and methods

65 consecutive patients receiving pelvic external beam radiotherapy were retrospectively analyzed. 30, 21 and 14 patients were treated with no-immobilization with a leg separator, whole body vacuum bag cushion (VBC) and six point aquaplast immobilization system, respectively. The systematic error, random error and the planning target volume (PTV) margins were calculated for all the three techniques and statistically analyzed.

Results

The systematic errors were the highest in the VBC and random errors were the highest in the aquaplast group. Both systematic and random errors were the lowest in patients treated with no-immobilization. 3D Systematic error (mm, mean±1SD) was 4.31±3.84, 3.39±1.71 and 2.42±0.97 for VBC, aquaplast and no-immobilization, respectively. 3D random error (mm, 1SD) was 2.96, 3.59 and 1.39 for VBC, aquaplast and no-immobilization, respectively. The differences were statistically significant between all the three groups. The calculated PTV margins were the smallest for the no-immobilization technique with 4.56, 4.69 and 4.59mm, respectively, in x, y and z axes, respectively.

Conclusions

Among the three techniques, no-immobilization technique with leg separator was the most reproducible technique with the smallest PTV margins. For obvious reasons, this technique is the least time consuming and most economically viable in developing countries.

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Keywords

3DCRT; IMRT; VBC; EPID; CBCT; PTV; CTV; SD; TE; Setup errors; Pelvic radiotherapy; Immobilization; No-immobilization; Aquaplast; Vacuum bag cushion

About this article
Title

Immobilization versus no immobilization for pelvic external beam radiotherapy

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 23, No 4 (2018)

Pages

233-241

Published online

2018-07-01

DOI

10.1016/j.rpor.2018.04.007

Bibliographic record

Rep Pract Oncol Radiother 2018;23(4):233-241.

Keywords

3DCRT
IMRT
VBC
EPID
CBCT
PTV
CTV
SD
TE
Setup errors
Pelvic radiotherapy
Immobilization
No-immobilization
Aquaplast
Vacuum bag cushion

Authors

Avinash H. Udayashankar
Shibina Noorjahan
Nirmala Srikantia
K. Ravindra Babu
Sandeep Muzumder

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