Influence of acquisition settings and radiation exposure on CT lung densitometry—An anthropomorphic ex vivo phantom study

Abstract

Objectives To systematically evaluate the influence of acquisition settings in conjunction with raw-data based iterative image reconstruction (IR) on lung densitometry based on multi-row detector computed tomography (CT) in an anthropomorphic chest phantom. Materials and methods Ten porcine heart-lung explants were mounted in an ex vivo chest phantom shell, six with highly and four with low attenuating chest wall. CT (Somatom Definition Flash, Siemens Healthineers) was performed at 120kV p and 80kV p , each combined with current-time products of 120, 60, 30, and 12mAs, and was reconstructed with filtered back projection (FBP) and IR (Safire, Siemens Healthineers). Mean lung density (LD), air density (AD) and noise were measured by semi-automated region-of interest (ROI) analysis, with 120kV p /120 mAs serving as the standard of reference. Results Using IR, noise in lung parenchyma was reduced by~31% at high attenuating chest wall and by~22% at low attenuating chest wall compared to FBP, respectively (p<0.05). IR induced changes in the order of ±1 HU to mean absolute LD and AD compared to corresponding FBP reconstructions which were statistically significant (p<0.05). Conclusions Densitometry is influenced by acquisition parameters and reconstruction algorithms to a degree that may be clinically negligible. However, in longitudinal studies and clinical research identical protocols and potentially other measures for calibration may be required.

A Computer-based Analysis for Identification and Quantification of Small Airway Disease in Lung Computed Tomography Images

“…19 A recent study has shown that acquisition protocols and reconstruction algorithms have clinically negligible effects on lung density. 21 However, identical protocols may be required in studies employing serial imaging. Generally, different scanners deliver different photon counts to individuals in a given milliampere second (mAs) due to factors, such as differences in beam filtration, alterations in tube potential, and rotation time.…”

“…Newly developed dose optimization protocols and iterative reconstruction techniques have allowed investigators to acquire CT scans at a fraction of standard clinical dose while presenting a quantitative analysis of AT. 20,21 In inspiratory CT scans, the tube current-time product may be decreased to 20 mAs, whereas in expiratory CT scans, it may be maintained low ( ≤ 50 mAs). 19 A recent study has shown that acquisition protocols and reconstruction algorithms have clinically negligible effects on lung density.…”

“…Minimization of radiation exposure, particularly as part of research protocols that use serial imaging, has always been of great significance. Newly developed dose optimization protocols and iterative reconstruction techniques have allowed investigators to acquire CT scans at a fraction of standard clinical dose while presenting a quantitative analysis of AT 20,21. In inspiratory CT scans, the tube current-time product may be decreased to 20 mAs, whereas in expiratory CT scans, it may be maintained low (≤50 mAs) 19.…”

“…In inspiratory CT scans, the tube current-time product may be decreased to 20 mAs, whereas in expiratory CT scans, it may be maintained low (≤50 mAs) 19. A recent study has shown that acquisition protocols and reconstruction algorithms have clinically negligible effects on lung density 21. However, identical protocols may be required in studies employing serial imaging.…”

“…Generally, different scanners deliver different photon counts to individuals in a given milliampere second (mAs) due to factors, such as differences in beam filtration, alterations in tube potential, and rotation time. Therefore, a fixed milliamperage yields different exposures, leading to noise differences and inconsistent Hounsfield unit (HU) measurements across scanners 18,20,21. Several teams are working on standard CT protocols to minimize inter-scanner variability.…”