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Long-term stability of the Hounsfield unit to electron density calibration curve in cone-beam computed tomography images for adaptive radiotherapy treatment planning

Published online by Cambridge University Press:  15 July 2015

Akihiro Takemura ,
Shogo Tanabe ,
Mei Tokai ,
Shinichi Ueda ,
Kimiya Noto ,
Naoki Isomura  and
Hironori Kojima
Akihiro Takemura*
Affiliation:
Institution of Medical, Pharmaceutical and Health Sciences, Faculty of Health Sciences, Kanazawa University, Kanazawa, Japan
Shogo Tanabe
Affiliation:
Department of Radiodiagnosis, Osaka Medical Center for Cancer and Cardiovascular Diseases, Higashinari, Osaka, Japan
Mei Tokai
Affiliation:
Division of Health Sciences, Graduate School of Medical Science, Kanazawa University, Kanazawa, Japan
Shinichi Ueda
Affiliation:
Department of Radiological Technology, Kanazawa University Hospital, Kanazawa, Japan
Kimiya Noto
Affiliation:
Department of Radiological Technology, Kanazawa University Hospital, Kanazawa, Japan
Naoki Isomura
Affiliation:
Department of Radiological Technology, Kanazawa University Hospital, Kanazawa, Japan
Hironori Kojima
Affiliation:
Department of Radiological Technology, Kanazawa University Hospital, Kanazawa, Japan
*
Correspondence to: Akihiro Takemura, Institution of Medical, Pharmaceutical and Health Sciences, Faculty of Health Sciences, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa 902-0942, Japan. Tel: +8 176 265 2538. Fax: +8 176 234 4366. E-mail: at@mhs.mp.kanazawa-u.ac.jp
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Abstract

Aim

To use cone-beam computed tomography (CBCT) images for treatment planning, the Hounsfield unit (HU)-electron density (ED) calibration table for CBCT should be stable. The purpose of this study was to verify the stability of the HU values for the CBCT system over 1 year and to evaluate the effects of variation in HU-ED calibration curves on dose calculation.

Materials and Methods

A tissue characterisation phantom was scanned with the field of view (FOV) of size S (FOV-S) and FOV of size M (FOV-M) using the CBCT system once a month for 1 year. A single field treatment plan was constructed on digital phantom images to validate the dose distribution using mean HU-ED calibration curves and possible variations.

Results

HU values for each material rod over the observation period varied with trend. The HU value of the cortical bone rod decreased by about 100 HU for the FOV-S and by about 300 HU for the FOV-M. Possible variation in the HU-ED calibration curves produced a ≤17·9% dose difference in the dose maximum in the treatment plan.

Conclusions

The CBCT system should be calibrated periodically for consistent dose calculation.

Keywords

adaptive radiotherapyCBCTdose calculationHU-ED calibration tablelong-term stability
Type
Original Articles
Information
Journal of Radiotherapy in Practice , Volume 14 , Issue 4 , December 2015 , pp. 410 - 417
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Copyright
© Cambridge University Press 2015 

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