Long-term stability of the Hounsfield unit to electron density calibration curve in cone-beam computed tomography images for adaptive radiotherapy treatment planning. Issue 4 (15th July 2015)

• Record Type: Journal Article
• Authors: Takemura, Akihiro; Tanabe, Shogo; Tokai, Mei; Ueda, Shinichi; Noto, Kimiya; Isomura, Naoki; Kojima, Hironori
• Is Part Of: Journal of radiotherapy in practice. Volume 14:Issue 4(2014)
• Page Start: 410
• Page End: 417
• Publication Date: 2015-07-15
• Subjects: adaptive radiotherapy, -- CBCT, -- dose calculation, -- HU-ED calibration table, -- long-term stability; Radiotherapy -- Periodicals; 615.842005
• DOI: 10.1017/S1460396915000321
• Languages: English
• ISSNs: 1460-3969

Abstract

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.