Assessment of the effects of CT dose in averaged x-ray CT images of a dose-sensitive polymer gel

8th International Conference on 3D Radiation Dosimetry

Kairn, T.^1,2 ; Kakakhel, M.B.^3 ; Johnston, H.^4 ; Jirasek, A.^4 ; Trapp, J.V.^2

Genesis Cancer Care Queensland, Brisbane, Australia^1

Science and Engineering Faculty, Queensland University of Technology, Brisbane, Australia^2

DPAM, Pakistan Institute of Engineering and Applied Sciences, PO Nilore, Islamabad

45650, Pakistan^3

Department of Physics and Astronomy, University of Victoria, Victoria

BC, Canada^4

关键词: Contrast-to-noise;    Dose measurement;    Hounsfield units;    Linear extrapolation;    Sensitive polymers;    Signal to noise;    X ray CT images;    X-ray computed tomography;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/573/1/012075/pdf
DOI  :  10.1088/1742-6596/573/1/012075

来源: IOP

【 摘 要 】

The signal-to-noise ratio achievable in x-ray computed tomography (CT) images of polymer gels can be increased by averaging over multiple scans of each sample. However, repeated scanning delivers a small additional dose to the gel which may compromise the accuracy of the dose measurement. In this study, a NIPAM-based polymer gel was irradiated and then CT scanned 25 times, with the resulting data used to derive an averaged image and a "zero-scan" image of the gel. Comparison between these two results and the first scan of the gel showed that the averaged and zero-scan images provided better contrast, higher contrast-to- noise and higher signal-to-noise than the initial scan. The pixel values (Hounsfield units, HU) in the averaged image were not noticeably elevated, compared to the zero-scan result and the gradients used in the linear extrapolation of the zero-scan images were small and symmetrically distributed around zero. These results indicate that the averaged image was not artificially lightened by the small, additional dose delivered during CT scanning. This work demonstrates the broader usefulness of the zero-scan method as a means to verify the dosimetric accuracy of gel images derived from averaged x-ray CT data.