AUTOMATIC MEASUREMENT OF CT NUMBER LINEARITY IN THREE TYPES OF CATPHAN PHANTOMS

Abstract

This study aims to develop an algorithm for automatically measuring CT number linearity in three different types of Catphan phantom. We used a sensitometry module image from three Catphan phantoms (types 500, 504, and 604). Each phantom and its air material were segmented. Based on the centroid of the air material, the coordinates for every object within the sensitometry modules were determined. The average CT numbers for every object were calculated and graphs of CT number linearity were automatically generated. Accurate segmentation of each object in the sensitometry modules produced accurate graphs of CT number linearity for each phantom. The linear regression of the Catphan 604 failed to pass the tolerance level, while the other two phantoms passed with R2 > 0.99. The automatic CT number linearity measurements were easy, fast, and more objective than manual measurements.