Department of Obstetrics and Gynecology, Mannheim University Hospital, Mannheim, Germany.
J Ultrasound Med. 2011 Aug;30(8):1085-91. doi: 10.7863/jum.2011.30.8.1085.
Three-dimensional (3D) sonography is an established volumetric method in gynecology and obstetrics. The aim of this study was to investigate the variability of 3D sonographic measurements and their accuracy in comparison with magnetic resonance imaging (MRI) for assessing fetal lung volume using in vitro lung models.
Twenty-three in vitro lung models with randomly defined volumes ranging from 1 to 60 mL were made from gelatin with plastic sheaths, manually molded into the shape of fetal lungs. The models were measured using 3D sonography and MRI. The 3D sonographic volumes were calculated using the rotational technique with angles of 6° and 30°. Multiplanar T2-weighted sequences were used for the MRI measurements. The percentage error and absolute percentage error were calculated for each method, and intraobserver and interobserver variability in 3D sonographic measurements was assessed with intraclass correlation coefficients (ICCs). Agreement between calculated and real volumes using the limits of agreement method was also evaluated.
The ICCs for the rotation angles indicated very good intraobserver and interobserver variability (6°, 0.995 and 0.996; 30°, 0.997 and 0.985). No systematic errors were observed in the mean percentage errors for 3D sonographic measurements or MRI volumetry. The lowest median absolute percentage error (1.76) was obtained with MRI volumetry, significantly lower than the values for sonography (6°, 5.00; P < .001; 30°, 5.49; P < .001). There were no significant differences in absolute percentage errors between the rotation angles (P = .82) and no significant differences in limits of agreement between 3D sonography and MRI (6°, P = .76; 30°, P = .39).
Three-dimensional sonographic volumetry was almost as accurate as MRI in this in vitro model and can be regarded as a good alternative method. Further research is needed to confirm these findings in vivo and to assess the prognostic value in fetuses with lung hypoplasia (eg, congenital diaphragmatic hernias).
三维（3D）超声是妇产科中一种成熟的容积测量方法。本研究旨在通过使用体外肺模型，研究 3D 超声测量的可变性及其与磁共振成像（MRI）在评估胎儿肺容积方面的准确性。
本研究共纳入了 23 个随机定义体积范围在 1 至 60 毫升之间的体外肺模型，这些模型由明胶和塑料护套制成，人工塑造成胎儿肺的形状。使用 3D 超声和 MRI 对模型进行测量。3D 超声体积使用旋转技术计算，角度为 6°和 30°。多平面 T2 加权序列用于 MRI 测量。为每种方法计算百分比误差和绝对百分比误差，并使用组内相关系数（ICC）评估 3D 超声测量的观察者内和观察者间变异性。还使用界限法评估了计算体积与真实体积之间的一致性。
旋转角度的 ICC 表明观察者内和观察者间的变异性非常好（6°，0.995 和 0.996；30°，0.997 和 0.985）。3D 超声测量或 MRI 容积测量的平均百分比误差均未观察到系统误差。MRI 容积测量的中位数绝对百分比误差最低（1.76），明显低于超声测量的数值（6°，5.00；P <.001；30°，5.49；P <.001）。旋转角度之间的绝对百分比误差无显著差异（P =.82），3D 超声和 MRI 之间的界限也无显著差异（6°，P =.76；30°，P =.39）。
在本体外模型中，3D 超声容积测量几乎与 MRI 一样准确，可以作为一种良好的替代方法。需要进一步的研究来确认这些发现的体内准确性，并评估其在肺发育不良（例如先天性膈疝）胎儿中的预后价值。
