open access

Vol 23, No 5 (2018)
Original research articles
Published online: 2018-09-01
Submitted: 2017-12-06
Get Citation

The effect of beam shape on physical parameters of head and neck simultaneous-integrated boost intensity-modulated radiation therapy

Toshiro Tsubouchi, Masashi Yagi, Iori Sumida, Keisuke Tamari, Yuji Seo, Kazuhiko Ogawa
DOI: 10.1016/j.rpor.2018.08.008
·
Rep Pract Oncol Radiother 2018;23(5):425-432.

open access

Vol 23, No 5 (2018)
Original research articles
Published online: 2018-09-01
Submitted: 2017-12-06

Abstract

Aim

To evaluate the influence of the beam shape created by X-rays with “flat beams” and without “flattening-filter-free [FFF] beams” a flattening filter, and the isocenter locations for FFF beams on the treatment of a large irradiated volume for tumours.

Background

The increase of dose rate and the decrease of out-of-field dose can be expected for FFF beams and lead to effective and safety radiotherapy. On the other hand, the bell-shaped dose profile is thought to be a factor of negating these advantages.

Materials and methods

Treatment plans for 15 patients with head and neck cancer were created using XiO (Elekta, Stockholm AB, Sweden) in fixed-gantry step-and-shoot delivery under the same dose constraints. Seven fields of FFF beams with 7 MV and flat beams with 6 MV were used with the technique of intensity-modulated radiation therapy (IMRT). We compared the dose homogeneity and conformity of targets and dose constraints for organs as the plan quality and evaluated physical parameters: monitor unit (MU) values, number of segments and their locations from the isocenter in beam's-eye-view.

Results

No significant differences were found in the plan quality. The isocenter locations do not affect the physical parameters for FFF beams. It has been confirmed that the number of segments and MU values were 40% higher with FFF beams than with flat beams (p < 0.05).

Conclusion

This study demonstrates flat dose distribution is more suitable for IMRT with large and complex targets.

Abstract

Aim

To evaluate the influence of the beam shape created by X-rays with “flat beams” and without “flattening-filter-free [FFF] beams” a flattening filter, and the isocenter locations for FFF beams on the treatment of a large irradiated volume for tumours.

Background

The increase of dose rate and the decrease of out-of-field dose can be expected for FFF beams and lead to effective and safety radiotherapy. On the other hand, the bell-shaped dose profile is thought to be a factor of negating these advantages.

Materials and methods

Treatment plans for 15 patients with head and neck cancer were created using XiO (Elekta, Stockholm AB, Sweden) in fixed-gantry step-and-shoot delivery under the same dose constraints. Seven fields of FFF beams with 7 MV and flat beams with 6 MV were used with the technique of intensity-modulated radiation therapy (IMRT). We compared the dose homogeneity and conformity of targets and dose constraints for organs as the plan quality and evaluated physical parameters: monitor unit (MU) values, number of segments and their locations from the isocenter in beam's-eye-view.

Results

No significant differences were found in the plan quality. The isocenter locations do not affect the physical parameters for FFF beams. It has been confirmed that the number of segments and MU values were 40% higher with FFF beams than with flat beams (p < 0.05).

Conclusion

This study demonstrates flat dose distribution is more suitable for IMRT with large and complex targets.

Get Citation

Keywords

Flat beams; Flattening-filter-free (FFF) beams; Treatment plans; Beam profile

About this article
Title

The effect of beam shape on physical parameters of head and neck simultaneous-integrated boost intensity-modulated radiation therapy

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 23, No 5 (2018)

Pages

425-432

Published online

2018-09-01

DOI

10.1016/j.rpor.2018.08.008

Bibliographic record

Rep Pract Oncol Radiother 2018;23(5):425-432.

Keywords

Flat beams
Flattening-filter-free (FFF) beams
Treatment plans
Beam profile

Authors

Toshiro Tsubouchi
Masashi Yagi
Iori Sumida
Keisuke Tamari
Yuji Seo
Kazuhiko Ogawa

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