Abstract
A kilo-voltage cone-beam CT (CBCT) attached to a linear accelerator can verify a target position in each radiation therapy. If CBCT images can be used in dose calculation, we can verify an actual dose distribution on every treatment day. However, the CBCT images are degraded by several factors, and so we cannot use the CBCT images directly in place of conventional multi-slice CT (MSCT) images that are used in the initial dose planning. In this paper, we proposed a new method for using CBCT and MSCT images in the calculation of a dose distribution. Our proposed method segments the CBCT and MSCT images into regions of three major organs (lungs, bones and soft tissues) by use of histogram analysis. We also calculated a value such as the median of the MSCT numbers in each region of the MSCT images, and we set three representative values to the corresponding regions of the CBCT images. In the calculation of a dose distribution, we used these modified CBCT images. The validity of our method was confirmed with experiments in which we used images of a heterogeneous phantom and patients’ lungs in comparison with conventional methods. The results showed that the dose distribution determined by our method was similar to that of the initial dose plan, and our method was superior to the conventional methods in terms of pass rates of a distance-to-agreement analysis and γ analysis. The results of a dose-volume-histogram analysis also showed the accuracy of our proposed method.
References
Hong TS, Tomé WA, Chappell RJ, Chinnaiyan P, Mehta MP, Harari PM. The impact of daily setup variations on head-and-neck intensity modulated radiation therapy. Int J Radiat Oncol Biol Phys. 2005;61:779–88.
Barker JL Jr, Garden AS, Ang KK, O’Daniel JC, Wang H, Court LE, Morrison WH, Rosenthal DI, Chao KS, Tucker SL, Mohan R, Dong L. Quantification of volumetric and geometric changes occurring during fractionated radiotherapy for head-and-neck cancer using an integrated CT/linear accelerator system. Int J Radiat Oncol Biol Phys. 2004;59:960–70.
Xing L, Lin Z, Donaldson SS, Le QT, Tate D, Goffinet DR, Wolden S, Ma L, Boyer AL. Dosimetric effects of patient displacement and collimator and gantry angle misalignment on intensity modulated radiation therapy. Radiother Oncol. 2000;56:97–108.
Ding GX, Duggan DM, Coffey CW, Deeley M, Hallahan DE, Cmelak A, Malcolm A. A study on adaptive IMRT treatment planning using kV cone-beam CT. Radiother Oncol. 2007;85:116–25.
Jeasen HR, Hansen O, Hjelm-Hansen M, Brink C. Inter- and intra-fractional movement of the tumor in extra cranial stereotactic radiotherapy of NSCLC. Acta Oncol. 2008;47:1432–7.
Usui K, Kihara A, Ichimaru Y, Okumura Y, Murakami K, Kunieda E, Ogawa K. Feasibility of kV-CBCT images for the dose calculation in image-guided radiotherapy. In: Proceedings of the 6th Japan Korea joint meeting medical physics 2011, CD-ROM.
Richter A, Hu Q, Steglich D, Baier K, Wilbert J, Guckenberger M, Flentje M. Investigation of the usability of conebeam CT data sets for doe calculation. Radiat Oncol. 2008;3:42. doi:10.1186/1748-717X-3-42.
Hu W, Ye J, Wang J, Ma X, Zhang Z. Use of kilovoltage X-ray volume imaging in patient dose calculation for head-and-neck and partial brain radiation therapy. Radiat Oncol. 2010;5:29. doi:10.1186/1748-717X-5-29.
Guan H, Dong H. Dose calculation accuracy using cone-beam CT (CBCT) for pelvic adaptive radiotherapy. Phys Med Biol. 2009;54:6239–50.
Rong Y, Smilowitz J, Tewatia D, Tomé WA, Paliwal B. Dose calculation on KV cone beam CT images: an investigation of the Hu-density conversion stability and dose accuracy using the site-specific calibration. Med Dosim. 2010;35:195–207.
Bamey BM, Lee RJ, Handrahan D, Welsh KT, Cook JT, Sause WT. Image-guided radiotherapy (IGRT) for prostate cancer comparing KV imaging of fiduciary markers with cone beam computed tomography (CBCT). Int J Radiat Oncol Biol Phys. 2011;80:301–5.
Siewerdsen JH, Jaffray DA. Cone-beam computed tomography with a flat-panel imager: magnitude and effects of X-ray scatter. Med Phys. 2001;28:220–31.
Zhu L, Xie Y, Wang J, Xing L. Scatter correction for cone-beam CT in radiation therapy. Med Phys. 2009;36:2258–68.
Author information
Authors and Affiliations
Corresponding author
About this article
Cite this article
Usui, K., Ichimaru, Y., Okumura, Y. et al. Dose calculation with a cone beam CT image in image-guided radiation therapy. Radiol Phys Technol 6, 107–114 (2013). https://doi.org/10.1007/s12194-012-0176-z
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s12194-012-0176-z