CT number accuracies for different number of detector array and age of detector: A multi-center study

Background: The accuracy of the CT number and its linearity are important parameters in computed tomography (CT) image quality. Both parameters may depend on the number of detector arrays and the age of detector. No previous study has investigated this issue.

Purpose: The purpose of this study was to investigate the CT number accuracy of various materials in ACR 464 CT phantom images and its linearity from 55 different scanners as a function of the number of detector arrays and age of detector.

Method: This study used an accredited ACR 464 CT phantom. The phantom was scanned by 55 CT different scanners from various vendors. The CT numbers of different materials and their linearity were automatically measured using IndoQCT software from images of the phantoms. The coefficient of determination (R²) was obtained from a graph of CT number versus material density. Information on the number of detector arrays (from 2- to 128-row array) and age of detector (from 1 to 12 years, determined from the commissioning date) were found from the Medical Physicist officer at each CT center.

Result: It was found that 6 out of the 55 scanners had a CT number linearity lower than 0.990. The CT scanners with R₂ values below this standard had a number of detector of 16- and 32-row array, and have detector ages of 3, 5, 8, 10, 11, and 18 years.

Conclusion: The accuracy of CT number and its linearity were independent of the number of detector arrays and the age of the detector. The finding suggests that quality control of the accuracy of CT number and its linearity should to be carried out periodically so that if any issues can be addressed as soon as possible.