A New Sonographic Phantom for Quality Control and Training Purposes

Abstract

Background: Evaluation of the accuracy and performance of sonography units needs tissue-mimicking phantoms. These phantoms play an important role by simulating soft tissues, obviating the need to experiment on humans or animals. Objectives: To present a simple sonographic phantom for quality control and training purposes. Materials and Methods:The presented phantom consists of a two-part Plexiglas box. The larger part is filled with a mixture of ethanol (9.5 ± 0.25%) in distilled water and a solution of sodium nitrite (0.1 M) to prevent rusting. The second part is filled with a combination of 3.85% by wt. % agar, and 50 g/L of powdered graphite as the background material. In this study, chrome-plated electric guitar strings, 0.52 mm in diameter, were used. Several objects were considered as tissue-equivalent material, and their images were obtained at different times. Criteria for the selection of suitable objects comprised similarity between the obtained image and the corresponding tissues in the human body, minimal shrinkage, and change in brightness level at different times. In addition to quantitative analysis obtained from image processing, a blind qualitative study was done by a radiologist. Results:Both results of quantitative analysis using MATLAB software and independent qualitative analysis showed that the commercial rubber and agar were appropriate as solid and cystic objects, respectively. Moreover, quantitative analysis done with MATLAB on images obtained from the phantom showed that the commercial rubber and agar had a 5% and 2% change in image pixel intensity (brightness) after 2 months, respectively. Conclusions: The presented phantom not only has lower cost and complexity, which make it suitable for educational centers, but also is capable of providing good images of cystic and solid objects for quality control and training purposes. Furthermore, it confers reliable stability for at least 2 months, as was assessed in the present study.