Tactile and Ultrasound Image Fusion for Functional Assessment of the Female Pelvic Floor

Abstract

Introduction: The true etiology of pelvic organ prolapse and urinary incontinence and variations observed among individuals are not entirely understood. Tactile (stress) and ultrasound (anatomy, strain) image fusion may furnish new insights into the female pelvic floor conditions. This study aimed to explore imaging performance and clinical value of vaginal tactile and ultrasound image fusion for characterization of the female pelvic floor.

Methods: A novel probe with 96 tactile and 192 ultrasound transducers was designed. Women scheduled for a urogynecological visit were considered eligible for enrollment to observational study. Intravaginal tactile and ultrasound images were acquired for vaginal wall deformations at probe insertion, elevation, rotation, Valsalva maneuver, voluntary contractions, involuntary relaxation, and reflex pelvic muscle contractions. Biomechanical mapping has included tactile/ultrasound imaging and functional imaging.

Results: Twenty women were successfully studied with the probe. Tactile and ultrasound images for tissues deformation as well as functional images were recorded. Tactile (stress) and ultrasound (strain) images allowed creation of stress-strain maps for the tissues of interest in absolute scale. Functional images allowed identification of active pelvic structures and their biomechanical characterization (anatomical measurements, contractive mobility and strength). Fusion of the modalities has allowed recognition and characterization of levator ani muscles (pubococcygeal, puborectal, iliococcygeal), perineum, urethral and anorectal complexes critical in prolapse and/or incontinence development.

Conclusions: Vaginal tactile and ultrasound image fusion provides unique data for biomechanical characterization of the female pelvic floor. Bringing novel biomechanical characterization for critical soft tissues/structures may provide extended scientific knowledge and improve clinical practice.

Keywords: Biomechanical Mapping; Pelvic Function; Pelvic Support; Tactile; Tissue Elasticity; Ultrasound.

Figure 1.

Vaginal probe with 96 tactile and 192 ultrasound transducers.

Figure 2.

Tactile and Ultrasound imaging fusion for Test 1 (probe insertion) allows elasticity assessment for critical structures; 34 y.o. women with normal pelvic floor conditions.

Figure 3.

Normal (left, A1- A4) and POP Stage II (right, B1-B4) posterior conditions imaged by TIUSv at probe elevation against posterior compartment (Test 2 results). A1, B1 – tactile images (pressure patterns); A2, B2 – gradient images calculated from the tactile images A1 and B1; A3, B3 – ultrasound images; A4, B4 – tactile and ultrasound image fusion allows assessment of pelvic floor support; C – sagittal diagram of the pelvic floor at probe elevation versus posterior compartment.

Figure 4.

Orthogonal ultrasound images with pressure distribution patterns in Test 3 (probe rotation). A – transverse image; B – image along the vagina at specified angle for 53 y.o. patient with stage II anterior prolapse.

Figure 5.

Anterior sagittal images of a patient with anterior Stage III POP and overactive bladder at rest (A) and Valsalva maneuver in Test 4 (B).

Figure 6.

Posterior images of a patient without posterior prolapse, but with uterine Stage II POP at rest (A) and at voluntary pelvic muscle contraction in Test 5 (B).

Figure 7.

Left side images of a 27 y.o. patient without prolapse at rest (A) and at voluntary pelvic muscle contraction in Test 6 (B).

Figure 8.

Images for involuntary muscle relaxation (Test 7), 37 y.o. patient without prolapse. A – ultrasound image at maximum muscle strength, and B – dynamic tactile image (pressure distribution on the vaginal wall as function of time – vertical axis).

Figure 9.

Images for involuntary muscle contraction (cough, Test 8). A - ultrasound image clearly demonstrates that the strong pressure signal (yellow graph) is coming from the urethra, not from pubic symphysis, for 44 y.o. patient with normal pelvic support (no POP), but with SUI and hyperactive urethra; and B - dynamic tactile image (pressure distribution on the vaginal wall as function of time – vertical axis) allows measurement of urethral mobility.