Abstract Purpose:
This study aimed to develop a new method for automated contrast-to-noise ratio (CNR) measurement using the low-contrast object in the ACR CT phantom.
Methods:
The ACR CT 464 phantom was scanned by 25 CT scanners installed at 25 different hospitals. AROI was placed in a specific radial location and was then rotated around 3600 increments of 20. At each position, the average CT number within the ROI was calculated. After one complete rotation, a profile of the average CT number around the 3600 degree was obtained. The center coordinate of the low-contrast object was determined from the maximum value of the profile. The CNR was calculated based on the average CT number and noise within the ROI in the low-contrast object and the ROI in the background, i.e., at the center of the phantom. The results were compared to a previous method based on a segmentation approach.
Results:
From 325 image samples of the 25 CT scanners, the proposed method successfully (100%) located the ROI within the low-contrast objects of all images used. The success rate of the segmentation method was only 56%.
Conclusion:
A new method for measuring CNR in the ACR CT phantom has been proposed and implemented. It is more powerful than a previous method based on segmentation.
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