In this video, we will review dynamic 3D transperineal ultrasound of the pelvic floor. This imaging technique may be valuable in the assessment of the structure of the levator ani muscle, the assessment of multi-compartment pelvic organ prolapse, and the evaluation of anatomic changes that can occur during valsalva and pelvic muscle contraction. Some of the anatomy of interest includes the urethra and bladder neck, shown here in the sagittal plane, the anal canal, shown here in the axial, sagittal, and coronal planes, and the levator ani muscles, shown here in the axial plane. Although transperineal ultrasound has a variety of indications, this video will focus on the assessment of levator ani muscle anatomy. The ultrasound probe used for these studies is a 4-8 MHz curved array transducer. This transducer generates a fan-shaped array of data in the plane of the transducer, creating a pyramid of 3D data that can be manipulated after acquisition. To start the study, the sonographer selects the 4D probe and picks a gynecology setting. Here we'll use a pelvic floor custom setting that we've created. Our pelvic floor presets include CRI and SRI set to 3, sector angle at maximum, which is at least 90 degrees, harmonics on to acquire sufficient resolution, and high frequency. We recommend setting two focal zones at 2 and 4 cm, reflecting the relatively short distance from the transducer to the anatomy of interest. After starting the 4D study, ensure that image acquisition is set for a depth of approximately 5 cm. We're going to obtain a 4D CINE loop with a split-screen configuration. The sagittal image is on this side. A rendered image is on this side. The rendered image is created by the ultrasound software. Rendering is a process by which all the data from a series of 2D images, or slices, are compressed into a single image. This technique can be useful to clarify the border of something curved, such as the levator muscle. The render box, shown here, specifies the section of the volume to be used for creating the rendered image. Here the sonographer selects a render box approximately 2 cm thick and wide enough to include the entire levator hiatus. The next step is to prepare the transducer. The surface is covered with gel and inserted into a probe cover. Here a glove is used as a cover. Tighten the transducer cover and secure with tape or a rubber band to keep the cover tight. Smooth out any air bubbles underneath the transducer cover, because a bubble in the layer of gel will create significant artifact. The patient should empty her bladder and should be in the lithotomy position for this study. A generous layer of warm gel is applied to the transducer cover. The ultrasound transducer should be positioned in the sagittal orientation on the perineal body. For more obese women, the sonographer will apply more pressure. The transducer orientation should result in this view, with the pubis on the left side of the image, the anal canal on the right side, and the border of the levator muscle posterior to the anal canal. This view ensures that the acquired volume will capture the relevant levator anatomy. The ultrasound settings allow for acquisition with a multi-planar view, including the sagittal plane, the coronal plane, and the axial plane. For levator assessment, it is important that the anatomy captured includes the plane of minimal hiatal dimensions, which is represented by the shortest AP distance from the pubis to the levator. The transverse levator diameter is also shown. The first series of volumes will use a Valsalva maneuver to measure the dimensions of the levator hiatus and to demonstrate organ descent. This Valsalva series is best obtained with the split-screen view. The render box has been placed at the plane of minimal hiatal dimension. Here the CINE loop shows the widening of the levator hiatus during Valsalva, as well as organ descent, shown here most clearly for descent of the bladder base. Encourage the patient to sustain a strong Valsalva for at least 5 seconds to capture the full effect of the Valsalva on the tissues. In severe prolapse, the ultrasound transducer should not be held so firmly against the perineum that the full extent of prolapse is inadvertently masked. This next series is a pelvic muscle contraction, or Kegel. The levator muscle is seen most clearly with maximal contraction. This series can be used to assess for levator injury and for biofeedback during pelvic muscle retraining. Similar to the Valsalva series, this series is best obtained with the split-screen view. Again, make sure the sagittal image captures the relevant landmarks and that the render box has been placed at the plane of minimal hiatal dimension. As the levator muscle is contracted, the levator should move toward the pubis, narrowing the hiatus. In the final segments of the video, we will focus on manipulation of acquired volumes. First, we'll measure the levator hiatus during Valsalva. Select a volume CINI that represents an adequate Valsalva effort. Select the point during the volume that represents the maximum Valsalva. Adjust the image so the plane of minimal hiatal dimensions is captured by the render box. Switch to the measurement tools, outline the hiatus with the area tool, and the hiatus area and circumference will be displayed on the screen. Post-acquisition processing can also be used to obtain a tomographic image, as shown here. Levator injuries are best seen on the tomographic view during maximal muscle contraction. Here, a normal tomographic view of the levator muscle is contrasted with an image showing a left-sided avulsion. The marked asymmetry is evident. To create the tomographic view, first, select a volume representing a levator contraction. Select the point in the volume that represents the maximal contraction. Adjust the image so the plane of minimal hiatal dimensions is captured by the render box. Switch to the tomographic view, and adjust the slice distance so the tomographic slices are at 2.5 mm intervals. In summary, as illustrated in this video, the 4D transperineal ultrasound can be easily performed with ultrasound equipment that is likely available in the OB-GYN department. The study is interactive and non-invasive. While this video has focused on the assessment of levator anatomy, this technique can also be used to investigate prolapse symptoms not accounted for by examination findings, to evaluate vaginal cysts including suspected urethral diverticulum, and for the postoperative assessment of sling position and tension in women with either persistent stress incontinence or urinary retention after a midurethral sling procedure. For more information, visit www.osho.com

dynamic 3D transperineal ultrasound

pelvic floor

levator ani muscle

pelvic organ prolapse

valsalva and pelvic muscle contraction