MR Virtual Endoscopy of the Fetal Limb Anomalies Using Three-Dimensional Fast Imaging Employing Steady-State Acquisition Sequence

<b><i>Objective:</i></b> To retrospectively investigate the feasibility of magnetic resonance virtual endoscopy (MRVE) to visualize the normal limbs and limb deformities <b><i>Methods:</i></b> MR sequences included two-dimensional (2D) single fast spin-echo sequence and 2D and 3D steady-state procession fast imaging sequences. MRVE reconstruction was retrospectively performed by 2 radiologists in 32 fetuses in 30 pregnant women. The correlation between the radiologists for the virtual endoscopy threshold of MRVE was determined. Image quality and limb segment visibility were independently rated. Area under the receiver operating characteristics curve (AUC) of 2D MRI and MRVE was calculated. <b><i>Results:</i></b> The mean virtual endoscopy threshold required for the visualization of the limb was 991.93 ± 12.13 and 991.83 ± 12.26 for 2 radiologists, respectively. The correlation between the radiologists for virtual endoscopy threshold was excellent (<i>r</i> = 0.933). The weighted kappa statistic was 0.96 for the evaluation of image quality of limb segments, indicating excellent interobserver agreement. Compared to that of 2D MRI alone, a higher AUC of 2D MRI with MRVE was achieved in detection of both upper and lower limb deformities (0.91 vs. 0.69 and 0.83 vs. 0.71, respectively). <b><i>Conclusion:</i></b> MRVE may display normal and abnormal fetal limb orientation and structures from multiple perspectives and provide incremental information for obstetrics.