open access

Vol 21, No 5 (2016)
Original research articles
Published online: 2016-09-01
Submitted: 2015-12-29
Get Citation

Impact of reduction of flux overlap region on kilovoltage cone-beam computed tomography image quality and patients’ exposure dose

Daisuke Kawahara, Shuichi Ozawa, Yuji Murakami, Takeo Nakashima, Masamichi Aita, Shintaro Tsuda, Yusuke Ochi, Takuro Okumura, Hirokazu Masuda, Yoshimi Ohno, Yasushi Nagata
DOI: 10.1016/j.rpor.2016.04.005
·
Rep Pract Oncol Radiother 2016;21(5):460-465.

open access

Vol 21, No 5 (2016)
Original research articles
Published online: 2016-09-01
Submitted: 2015-12-29

Abstract

Aim

In high-precision radiation therapy, kilovoltage cone-beam computed tomography plays an important role in verifying the position of patient and localization of the target. However, the exposure dose is a problem with kilovoltage cone-beam computed tomography. Flux overlap region increases the patient dose around the center when the scan is performed in a full-scan mode. We assessed the influence of flux overlap region in a full-scan mode to understand the relationship between dose and image quality and investigated methods to achieve a dose reduction.

Method

A Catphan phantom was scanned using various flux overlap region patterns in the pelvis on a full-scan mode. We used an intensity-modulated radiation therapy phantom for measuring the central dose. DoseLab was used to perform image analysis and to evaluate the linearity of the computed tomography values, uniformity, high-contrast resolution, and contrast-to-noise ratio.

Results

The Hounsfield unit value varied by ±40 Hounsfield unit of the acceptance value for the X1 field size of 3.5[[ce:hsp sp="0.25"/]]cm. However, there were no differences in high-contrast resolution and contrast-to-noise ratio among different scan patterns. The absorbed dose decreased by 7% at maximum for the case within the tolerance value.

Conclusion

Dose reduction is possible by reducing the overlap region after calibration and by performing computed tomography in the appropriate overlap region.

Abstract

Aim

In high-precision radiation therapy, kilovoltage cone-beam computed tomography plays an important role in verifying the position of patient and localization of the target. However, the exposure dose is a problem with kilovoltage cone-beam computed tomography. Flux overlap region increases the patient dose around the center when the scan is performed in a full-scan mode. We assessed the influence of flux overlap region in a full-scan mode to understand the relationship between dose and image quality and investigated methods to achieve a dose reduction.

Method

A Catphan phantom was scanned using various flux overlap region patterns in the pelvis on a full-scan mode. We used an intensity-modulated radiation therapy phantom for measuring the central dose. DoseLab was used to perform image analysis and to evaluate the linearity of the computed tomography values, uniformity, high-contrast resolution, and contrast-to-noise ratio.

Results

The Hounsfield unit value varied by ±40 Hounsfield unit of the acceptance value for the X1 field size of 3.5[[ce:hsp sp="0.25"/]]cm. However, there were no differences in high-contrast resolution and contrast-to-noise ratio among different scan patterns. The absorbed dose decreased by 7% at maximum for the case within the tolerance value.

Conclusion

Dose reduction is possible by reducing the overlap region after calibration and by performing computed tomography in the appropriate overlap region.

Get Citation

Keywords

Cone beam CT; Flux overlap region; IGRT

About this article
Title

Impact of reduction of flux overlap region on kilovoltage cone-beam computed tomography image quality and patients’ exposure dose

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 21, No 5 (2016)

Pages

460-465

Published online

2016-09-01

DOI

10.1016/j.rpor.2016.04.005

Bibliographic record

Rep Pract Oncol Radiother 2016;21(5):460-465.

Keywords

Cone beam CT
Flux overlap region
IGRT

Authors

Daisuke Kawahara
Shuichi Ozawa
Yuji Murakami
Takeo Nakashima
Masamichi Aita
Shintaro Tsuda
Yusuke Ochi
Takuro Okumura
Hirokazu Masuda
Yoshimi Ohno
Yasushi Nagata

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