Analysis of the Attenuation Coefficient of Composite Silicone Rubber and Gliceryn for Soft Tissue Phantom Applications

Abstract

Introduction: Phantom is an object that can be used to investigate the accuracy of radiation dose delivered to patients. Phantom is usually produced from the combination of the silicone rubber as a matrix and glycerin as a filler to form a composite for the replacement of the human soft tissue. The composite is imaged using computed tomography (CT) simulator for the determination of the attenuation coefficient. Material and Methods: The Phantom in the current study has been synthesized from silicone rubber with and without the addition 10% and 20% of glycerin. The type of silicone rubber in this study was Room Temperature Vulcanized (RTV) 52 with blue catalyst by a ratio of 100:5 (wt%). Samples were scanned using CT simulator to obtain the images and then exported to the Eclipse treatment planning system for analysis. The region of interest (ROI) was at the center of an area of 50×50 pixels to determine the CT number. Results: The ROI results for the sample without and with the addition of glycerin 10% and 20% resulted in the CT values of 287.4, 280.5, and 225.2 HU, respectively, which were within the ROI range of the human soft tissue. The attenuation coefficients of the 3 samples were 0.239, 0.238±0.001, and 0.233±0.001 cm-1 for no glycerin, glycerin 10%, and glycerin 20%, respectively. The values of the half-value layer were 2.902±0.001, 2.911±0.001, and 2.980± 0.001 cm for phantom with no glycerin, glycerin 10%, and glycerin 20%, respectively. Conclusion: Phantoms in the current study were indicative of high potentials as an object of research for radiotherapy and educational purposes. Moreover, the composite with glycerin 20% could be the best surrogate of tissue in order to study human liver.