Reliability and validity of MR image lung volume measurement in fetuses with congenital diaphragmatic hernia and in vitro lung models.

PURPOSE: To prospectively assess the reliability of magnetic resonance (MR) image volume measurement in fetuses with congenital diaphragmatic hernia (CDH) and the reliability and validity of measurements in in vitro lung models.

MATERIALS AND METHODS: This study was approved by the ethics committee, and informed consent was obtained. MR fetal lung volume (FLV) was measured in 40 consecutive fetuses with CDH by using half-Fourier acquired single-shot turbo spin-echo MR imaging and true fast imaging with steady-state precession at 24-36 weeks gestation (mean gestational age, 30.6 weeks +/- 3.5 [standard deviation]). Lung volumes were independently assessed in three orthogonal section planes by two experienced observers. Additionally, 28 in vitro lung models of defined volumes of 1-60 mL were evaluated the same way. To assess measurement validity and reliability, the intraclass correlation coefficient (ICC) and the Bland-Altman plot were used.

RESULTS: The interobserver reliability was high for both the lung models and FLV measurements (ICC, 0.999 and 0.928, respectively). Measurement validity was also good, with a mean difference between the calculated volume and the true volume of 0.4 mL (95% confidence interval: 0.30, 0.48). Measurement reliability and validity did not depend, to any considerable degree, on imaging plane or sequence (ICC range, 0.878-0.999) or on total volume.

CONCLUSION: The reliability and validity of MR volume measurements are high. The method is independent of the sequence and the imaging plane and can be performed with a very good interobserver agreement, even in small volumes.