Evaluation of the Agreement Between 3-Dimensional Ultrasonography and Magnetic Resonance Imaging for Fetal Lung Volume Measurement

OBJECTIVE The purpose of this study was to assess the agreement between 3-dimensional ultrasonography (3DUS) and magnetic resonance imaging (MRI) for lung volumetry in fetuses with and without abnormalities associated with lung hypoplasia. METHODS Fifty-nine singleton pregnancies were evaluated. Cases were separated into groups 1 and 2, according to the presence or absence of malformations associated with lung hypoplasia, respectively. Fetal lung volume was calculated by the Virtual Organ Computer-Aided Analysis (VOCAL) program of the 3DUS and the MRI. In both groups, measurements performed with all VOCAL angles were compared among themselves and with those obtained by MRI. Bland-Altman tests and analysis of variance were used for this purpose. RESULTS In groups 1 and 2, the mean lung volume obtained with each rotation angle of the VOCAL technique was significantly smaller than the mean volume calculated by MRI (P < .001), and the mean volume obtained with the 30 degrees rotation step was significantly smaller than those obtained with the other rotation steps of the VOCAL technique. Bland-Altman tests confirmed this underestimation and showed a broad 95% confidence interval when the VOCAL angles were compared with those of MRI and when the 30 degrees rotation step was compared with the other VOCAL steps. CONCLUSIONS There was a substantial discrepancy between 3DUS and MRI and between the 30 degrees rotation step of the VOCAL technique and the other rotation angles, for lung volume measurement in fetuses with and without abnormalities associated with lung hypoplasia.