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

详细信息    查看全文

• 作者：Daisuke Kawahara^a ; ^b ; Shuichi Ozawa^c ; ^{ozawa@hiroshima-u.ac.jp" class="auth_mail" title="E-mail the corresponding author} ; Yuji Murakami^c ; Takeo Nakashima^a ; Masamichi Aita^a ; Shintaro Tsuda^a ; Yusuke Ochi^a ; Takuro Okumura^a ; Hirokazu Masuda^a ; Yoshimi Ohno^a ; Yasushi Nagata^c
• 关键词：Cone beam CT ; Flux overlap region ; IGRT
• 刊名：Reports of Practical Oncology & Radiotherapy
• 出版年：2016
• 出版时间：September-October 2016
• 年：2016
• 卷：21
• 期：5
• 页码：460-465
• 全文大小：2178 K

文摘

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 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.