I Jin Joo MD, Abstract Co-Author: Nothing to Disclose

Se Hyung Kim, Presenter: Nothing to Disclose

Jae Young Lee MD, Abstract Co-Author: Nothing to Disclose

Jeong-Min Lee MD, Abstract Co-Author: Advisory Board, Bayer AG

Joon Koo Han MD, Abstract Co-Author: Nothing to Disclose

Byung I. Choi MD, PhD, Abstract Co-Author: Research collaboration, Taewoong-Medical Co, Ltd

To compare the accuracy between semi-automated and manual measurements for the volume and longest diameter of simulated hepatic lesions in phantom models, and to evaluate the effect of slice thickness (ST) and reconstruction increment (RI) on their accuracy.

Six liver phantoms with 45 hypo- and 45 hyper-attenuating lesions of different sizes (diameter 13.3-50.7mm, volume 0.4-54.0ml) and shapes (spherical, elliptical) were scanned with a 64-row MDCT scanner using 0.6mm collimation, 120kVp, 200mAs, 0.5 second rotation time, and a pitch of 1.1. To evaluate the effect of z-axis resolution on the accuracy of measurement, images were reconstructed with ST/RI settings of 0.75mm/0.7mm, 1.0mm/0.7mm, 1.5mm/1.0mm, 3.0mm/2.0mm, 3.0mm/3.0mm, and 5.0mm/5.0mm. Two radiologists then measured the longest diameter and volume of each lesion both manually and semi-automatically and compared them with reference values by calculating the absolute percentage error (APE). Comparison of APE between the two methods for both diameter and volume and between ST/RI settings were performed using paired t-tests. Degree of correlation between each measurement and reference values were also assessed.

The semi-automated method showed significantly higher accuracy in measuring volume for most ST/RI settings (0.75mm/0.7mm, 1.0mm/0.7mm, and 1.5mm/1.0mm in hypo- and all STs/RIs in hyper-attenuating lesions) and similar accuracy (p>0.05 at all STs/RIs regardless of lesion attenuation) in measuring diameter. Additionally, the semi-automated method demonstrated higher correlation with reference values than manual measurements for both diameter and volume. Regardless of measurement method and lesion attenuation, APE value was smallest in the thinnest setting and gradually increased, reaching its largest value at the thickest setting for both diameter and volume. Acceptable maximum ST/RI setting was 3mm/2mm.

Regardless of lesion attenuation, the semi-automated method shows higher accuracy and correlation than the manual method in measuring diameter and volume, and accuracy of both methods is highly dependent on z-axis resolution.

In the era of treatment monitoring, the semi-automated method can replace manual measurements of both diameter and volume. However, z-axis settings over 3mm/2mm should be avoided for accurate results.

Joo, I, Kim, S, Lee, J, Lee, J, Han, J, Choi, B, Comparison of Semi-automated and Manual Measurements for Simulated Hypo and Hyper-attenuating Hepatic Tumors on MDCT: Effect of Slice Thickness and Reconstruction Increment on Accuracy.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9007963.html