The Feasibility of Contrast-to-Noise Ratio on Measurements to Evaluate CT Image Quality in Terms of Low-Contrast Detailed Detectability

Abstract

<jats:p>Background: To evaluate contrast-to-noise ratio (CNR) measurements in assessing image quality, in the context of the detectability performance of low-contrast detail (LCD), in computed tomography (CT) images, since exposure to elevated ionising-type radiation is considered to present excessive carcinogenic risk, whilst also causing distress in study subjects. Methods: An LCD phantom module (CTP515) was utilised in the study. Three dissimilar contrast items were used to analyse the ramifications of the proportions of an object on the CNR. Three multidetector CT (MDCT) scanners were used, with 16-MDCT, 64-MDCT and 80-MDCT frameworks, respectively. The CT scans were recreated using three dissimilar remaking algorithms—soft, standard and lung. The effects exerted on the CNR by various remodelling algorithms, as well as the contrast of various objects along with the size of the objects, were explored. The Hounsfield units of each chosen object (one unit representing the outer portion of the object) and the background and the standard deviation of the noise parameter were quantified, and algorithms were developed using MATLAB. Results: The CNR information was greatly influenced by changing the image recreation calculations and was very much increased in the soft-tissue recreation images using 16-MDCT and 64-MDCT. The CNR information was also increased more in the optimum recreation images than in the reproduced images from the computational procedure used in the 80-MDCT. The results did not show any remarkable contrasts in the CNR values between the different object sizes. Overall, a higher kVp produced an improved CNR in all the CT scanners. In particular, there were prominent upgrades in the CNR information when the kVp was increased from 80 to 120. Higher mAs levels gave better CNR values overall, especially for greater section thicknesses. Based on the CNR estimations, the 64-MDCT provided the best correlation among the CT scanners. Conclusions: The objective LCD appraisal method, based on CNR measurements, was confirmed as being useful for checking the different impacts of kVp, mAs and section thickness on the nature of the picture. This procedure was similarly viable in assessing the impacts of the different reconstruction calculations and the different differentiation questions on the nature of the image.</jats:p>

Automated development of the contrast–detail curve based on statistical low‐contrast detectability in CT images

“…It was found that if noise level increases, then the target size also increases, as reported previously. 30,31 This is because the high levels of noise affect the shape of the sharp edge of the object, reducing the MDC especially for small objects.…”

Image quality characterization of an ultra‐high‐speed kilovoltage cone‐beam computed tomography imaging system on an O‐ring linear accelerator

“…Further details regarding the region of interest (ROI) selection and CNR computation are elaborated in the subsequent CT number accuracy section. Since the standard deviation of the CT number is inversely proportional to the square root of the tube current (mAs), 19 tube current‐normalized CNR was calculated by dividing the CNR and noise with the square root of the tube current ($$CNR/\sqrt {mAs} $$) to exclude the impact of the different tube currents of each protocol 18–20 …”

“…Since the standard deviation of the CT number is inversely proportional to the square root of the tube current (mAs), 19 tube current-normalized CNR was calculated by dividing the CNR and noise with the square root of the tube current (CNR∕ √ mAs) to exclude the impact of the different tube currents of each protocol. [18][19][20] In addition, to assess the nonlinear contrast resolution, we measured the minimum detectable diameter of contrast rods using the CTP730 low contrast module of the Catphan 604. This module contains nine rods with diameters of 1, 2, 3, 4, 5, 6, 7, 8, and 9 mm, in addition to 15 mm, for each contrast level: 1%, 0.5%, and 0.3%.…”

The Effects Of High Dose and Low Dose Protocols In Thorax’s CT Scan Image Quality

“…Perubahan faktor eksposi tidak memberikan efek yang besar terhadap feature-feature radiomic dari citra CT Scan [21] . [22] . [14] .…”