Fabrication and Evaluation of Thyroid Shield from Silicone Rubber-Cooper and its Comparison to Tube Current Modulation in CT Examination

Abstract

This study aimed to fabricate thyroid shields made from Silicone Rubber (SR)-Cooper (Cu) material, analyze the effectiveness of SR-Cu shields in reducing radiation dose, and compare them with tube current modulation (TCM) in computed tomography (CT) examination. Thyroid shields were made from SR-Cu with Cu percentages of 0, 5, 10, 15, and 20%. The thyroid shields were positioned over the neck of the anthropomorphic phantom. Scanning was performed using a GE 128-slice CT scanner with fixed tube current of 150 mA and tube current modulation (TCM). The elatiscity of thyroid shields was tested using an universal testing machine (UTM). The ability of thyroid shields for dose reduction was measured using a 10X6-3CT Radcal detector, and quality of the resulted images was characterized with metric of signal-to-noise ratio (SNR) at the anterior, posterior, and lateral areas of the neck area of anthropomorphic phantom. It is found that the elasticity of the thyroid shields increased from 0.09 to 0.12 N/mm2 for Cu percentages from 0 to 20%. The measured dose decreased as the percentage of Cu increased. 20% of SR-Cu was able to reduce the dose by 32.4% for the fix tube current. In comparison, the TCM technique reduced the dose by 44.5%. Therefore, dose reduction using the developed shields is lower than using TCM approach. It is also found that implementation of the thyroid shields did not reduce image quality significantly. It is found that there were no apparent artifacts in the images. The highest SNR was found in the image with 20% SR-Cu, which was 3.84. In comparison, the SNR using the TCM approach was 3.59. In conclusion SR-Cu shields were successfully developed and they reduced dose with relatively consistent of image quality.