Measuring the levator hiatus with axial MRI sequences: Adjusting the angle of acquisition

By rotating the acquisition plane to be parallel to the puborectalis muscle (sometimes called the plane of minimal hiatal dimensions), some of the measurements of the distal and medial pelvic floor muscles (and the hiatus defined by them) are altered. This issue is important because both MRI and 3D ultrasound are increasingly being used to evaluate the pelvic floor hiatus, and its relationship to childbirth injury and pelvic floor disorders. To make meaningful comparisons, it is important that both modalities are measuring the same thing.