The Influence of CT Reconstruction Methods on the Accuracy of Monitoring Lung Nodule Diameters at Different Dose Levels
Plasman, Paul; Baxter, H.; Coleman, L.; Hogg, Peter; Hustveit, Hanne; Rizvi, A.; van der Sluis, L.G.; Telle, Christina; Zigterman, J.
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2016Metadata
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Original version
Plasman P, Baxter, Coleman, Hogg P, Hustveit H, Rizvi, van der Sluis L, Telle C, Zigterman: The Influence of CT Reconstruction Methods on the Accuracy of Monitoring Lung Nodule Diameters at Different Dose Levels. In: Hogg P, Blakeley, Buissink C. OPTIMAX 2015 : Multicultural team-based research in radiography, a holistic educational approach. , 2016. University of Salford p. 100-111Abstract
Purpose:
This study aims to investigate the effect of filtered back projection (FBP)
and sinogram-affirmed iterative reconstruction (SAFIRE) on the accuracy of lung
nodule diameter measurements at different dose levels.
Method:
48 CT images were acquired (at tube-current time product of 10, 20,
30 and 40 mAs) using an anthropomorphic phantom Lungman N1 ©, containing
simulated spherical lung nodules of +100 Hounsfield Units of 5, 8 and 12mm
diameter. Images were reconstructed with FBP and SAFIRE strengths 1, 3, and 5.
Twelve participants, with radiographic experience, performed nodule diameter
measurements for all images. Nodule edge sharpness was calculated for all images
by measuring the angle of profile edge slope.Contrast to Noise Ratio (CNR) values
were obtained from pixel values in regions of interest (ROIs) in the lung nodule and
background air. Measurement accuracy was assessed by calculating the absolute
error percentage (AEP) between participant’s measurements and actual nodule size.Results:
There is no significant difference in nodule diameter measurement
between mAs values and reconstruction algorithms (p-value 0,009 - 0,969). AEP
showed no significant difference (p-value 0,041-0,969) for any of the reconstruction
algorithms.
Discussion:
Previous research using SAFIRE suggests a decrease of mAs while
maintaining image quality. Furthermore, SAFIRE has the ability to increase CNR
and decrease image artefacts. However, the findings in this study suggest that
accuracy of lung nodule measurement does not improve with an increase of CNR
values nor the line profiles of edge sharpness.
Conclusion:
Our study suggests that image dose levels can be reduced
without compromising nodule diameter measurement accuracy, regardless of
reconstruction method.