Abstract
PurposeTo evaluate the reliability of 3D image analysis and the effect of an iodine contrast agent on the computed tomography (CT) Hounsfield unit (HU) values of the proximal femur.Materials and methodsFifty female patients (mean age, 61.3 years; age range, 50–79 years) who underwent both pre- and post-enhancement abdominopelvic CT scans were included in this retrospective study. Whole 3D volumes of the left proximal femur from the head to the lesser trochanter were extracted using the regional growth technique with commercial 3D software. Total volume, mean HU, and HU histogram analysis (HUHA) values of the extracted femur were calculated. HUHA distribution was classified into HUHAfat for the assumed fatty marrow (percentage of negative HU values) and HUHAdense-bone (percentage of HU values ≥ 126 HU). Reliability was assessed by calculating intra- and interobserver correlation coefficients (ICCs) and by drawing Bland–Altman plots. The effect of contrast medium administration was evaluated by the paired t-test.ResultsAll intra- and interobserver ICCs of 3D volume measurements showed excellent reproducibility (all ICCs > 0.90). On Bland–Altman analysis of two observers’ 3D volume measurements, the differences in the mean total volume, HUHAfat, HUHAdense-bone, and mean HU were 2.4 cm3, 0.17%, 0.6%, and 1.9 HU, respectively. The mean difference in HU after contrast agent administration (-2.2 HU) was not significant (P = 0.27). The mean difference in HUHAfat and HUHAdense-bone after contrast agent administration were -1.1% and -2.2%, respectively, on the Bland–Altman plot. HUHAfat and HUHAdense-bone showed significant differences (P < 0.05). The 95% limits of agreement for HUHAfat, HUHAdense-bone, and mean HU were -3.6% to 1.3%, -6.5% to 2.1%, and -30.0 to 25.5 HU, respectively.ConclusionImage analysis based on 3D volume measurement of the proximal femur showed excellent reliability, with the contrast agent administration showing negligible influence on the mean HU.
Highlights
The major advantage of imaging analysis using computed tomography (CT) is its reliability [1,2,3]
Image analysis based on 3D volume measurement of the proximal femur showed excellent reliability, with the contrast agent administration showing negligible influence on the mean Hounsfield unit (HU)
Recent advances in three-dimensional (3D) image analysis software have made it possible to draw HU histograms of regions of interest (ROIs) [4], which can be subclassified by HU range to calculate the proportions of fat and cortical bone
Summary
The major advantage of imaging analysis using computed tomography (CT) is its reliability [1,2,3]. Recent advances in three-dimensional (3D) image analysis software have made it possible to draw HU histograms of regions of interest (ROIs) [4], which can be subclassified by HU range to calculate the proportions of fat and cortical bone. This analysis shows a strong positive correlation and high diagnostic performance for predicting osteoporosis of the femoral neck in comparison with analyses based on the mean HU value [5]. Reliability evaluation of this technique has not yet been reported
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