OP26.04: Reliability of three‐dimensional ultrasound measurements of the levator ani hiatus using virtual reality
Leonie Speksnijder, Melek Rousian, Eric A.P. Steegers, Anton H. J. Koning, Anneke B. Steensma · Ultrasound in Obstetrics and Gynecology · 2010
To establish the reliability of three-dimensional (3D) ultrasound measurements of the levator ani hiatus in a virtual reality system. In 2008, 100 symptomatic patients in a tertiary pelvic floor clinic were analyzed with a normal intact levator ani muscle on pelvic floor ultrasound imaging, using a Voluson 730 Expert system and a 4–8 MHz RAB probe. Offline two-dimensional (2D) measurements were performed using 4D view version 9.0. With 4D view a rendered volume with a slice thickness of 1.5 cm was obtained at the level of minimal hiatal dimension during contraction. The datasets were then transferred to the I-Space (Barco, Belgium); a virtual reality system that allows the observer to perceive depth and interact with volume-rendered (ultrasound) data. The volumes were rendered in 3D using the V-scope application and semi-automatically measured using a virtual pointer. All measurements were repeated three times and their mean values were used for comparison. For comparing both measurements the 2D measurements were enlarged by 1.5. The mean age was 54 years (range: 22–79). The mean hiatal area in 4D view (2D) and the I-Space (3D) was 14.43 cm (SD 3.38) and 21.75 cm (SD 4.79). The mean difference between the measurements made with 4D view and I-Space was 0.11 cm (SD 1.26) (P = 0.40) with a Pearson correlation of 0.97 (P < 0.001). The ICCs comparing 4D View with the I-Space measurements were 0.983 (P < 0.001). The intra- and interobserver ICCs for 4D view measurements were 0.972 (P < 0.001) and 0.905 (P < 0.001). The intra- and interobserver ICCs for the measurements with the I-Space were 0.991 (P < 0.001) and 0.981 (P < 0.001). The application of virtual reality offers possibilities for measuring non-planar structures. Levator hiatal area measurements in the I-Space were reliable and comparable with measurements in 4D view. New areas of pelvic measurements can now be explored using this technique.