Computer simulations of thermal tissue remodeling during transvaginal and transurethral laser treatment of female stress urinary incontinence

Dual-sectored transurethral ultrasound for thermal treatment of stress urinary incontinence: in silico studies in 3D anatomical models

The purpose of this study is to investigate the feasibility and performance of a stationary, non-focused dual-sectored tubular transurethral ultrasound applicator for thermal exposure of tissue regions adjacent to the urethra for treatment of stress urinary incontinence (SUI) through acoustic and biothermal simulations on 3D anatomical models. Parametric studies in a generalized tissue model over dual-sectored ultrasound applicator configurations (acoustic surface intensities, lateral active acoustic output sector angles, and durations) were performed. Selected configurations and delivery strategies were applied on 3D pelvic anatomical models. Temperature and thermal dose distributions on the target region and surrounding tissues were calculated. Endovaginal cooling was explored as a strategy to mitigate vaginal heating. The 75-90° dual-sectored transurethral tubular transducer (3.5 mm outer diameter (OD), 14 mm length, 6.5 MHz, 8.8-10.2 W/cm²) and 2-3-min sonication duration were selected from the parametric study for acoustic and biothermal simulations on anatomical models. The transurethral applicator with two opposing 75-90° active lateral tubular sectors can create two heated volumes for a total of up to 1.8 cm³ over 60 EM_43 °C, with at least 10 mm radial penetration depth, 1.2 mm urethral sparing, and no lethal damage to the vagina and adjacent bone (< 60 EM_43 °C). Endovaginal cooling can be applied to further reduce the vaginal wall exposure (< 15 EM_43 °C). Simulations on 3D anatomical models indicate that dual-sectored transurethral ultrasound applicators can selectively heat pelvic floor tissue lateral to the mid-urethra in short treatment durations, without damaging adjacent vaginal and bone tissues, as a potential alternative treatment option for stress urinary incontinence. Graphical abstract Schema for in silico investigation of transurethral ultrasound thermal therapy applicator for minimally invasive treatment of SUI.

A computational analysis of the effect of supporting organs on predicted vesical pressure in stress urinary incontinence

Stress urinary incontinence (SUI) or urine leakage from urethra occurs due to an increase in abdominal pressure resulting from stress like a cough or jumping height. SUI is more frequent among post-menopausal women. In the absence of bladder contraction, vesical pressure exceeds urethral pressure leading to urine leakage. The main aim of this study is to utilize fluid-structure interaction techniques to model bladder and urethra computationally under an external pressure like sneezing. Both models have been developed with linear elastic properties for the bladder wall while the patient model has also been simulated utilizing the Mooney-Rivlin solid model. The results show a good agreement between the clinical data and the predicted values of the computational models, specifically the pressure at the center of the bladder. There is 1.3% difference between the predicted vesical pressure and the vesical pressure obtained from urodynamic tests. It can be concluded that the accuracy of the predicted pressure in the center of the bladder is significantly higher for the simulation assuming nonlinear material property (hyperelastic) for the bladder in comparison to the accuracy of the linear elastic model. The model is beneficial for exploring treatment solutions for SUI disorder. Graphical abstract ^{3D processing of bladder deformation during abdominal pressure of a the physiological model and b the pathological model (starting from left to right and up to down, consecutively)}.

Efficacy of Fractional CO2 Laser, Promestriene, and Vaginal Lubricant in the Treatment of Urinary Symptoms in Postmenopausal Women: A Randomized Clinical Trial

BACKGROUND AND OBJECTIVES

Evaluating the efficacy of the fractional CO₂ laser, promestriene, and vaginal lubricant to treat urinary symptoms in women with genitourinary syndrome of menopause.

STUDY DESIGN/MATERIALS AND METHODS

We conducted a randomized clinical trial with 72 postmenopausal women aged 50 years or older. The participants were randomized to one intervention each in three treatment groups fractional CO₂ laser, promestriene, and vaginal lubricant. Urinary symptoms were assessed prior to treatment and 2 weeks after treatment completion using validated questionnaires, the International Consultation on Incontinence Questionnaire (ICIQ-UI SF), and the International Consultation on Incontinence Questionnaire Overactive Bladder (ICIQ-OAB).

RESULTS

There was a significant reduction in the total ICIQ-UI SF score in the intragroup comparison (baseline vs. week 14) of the CO₂ laser group (P = 0.004). This group also showed a statistically significant reduction in nocturia (1.33 ± 0.87 vs. 1.00 ± 0.76, respectively; P = 0.031). In the intergroup comparison after treatment, nocturia in the lubricant group had worsened compared with that of the other two groups (P = 0.002). Regarding the total ICIQ-OAB score, the results of the CO₂ laser group were superior to those of the lubricant group in the intergroup comparison (7.76 ± 3.36, P = 0.020; analysis of variance P = 0.038).

CONCLUSION

The results were significantly different between the intravaginal fractional CO₂ laser and topical estrogen groups for treating urinary symptoms related to the genitourinary syndrome of menopause. Further controlled and randomized studies are needed. Lasers Surg. Med. © 2020 Wiley Periodicals, Inc.

The Rationale for Photobiomodulation Therapy of Vaginal Tissue for Treatment of Genitourinary Syndrome of Menopause: An Analysis of Its Mechanism of Action, and Current Clinical Outcomes

Objective: Light, particularly in the visible to far-infrared spectrum, has been applied to the female genital tract with lasers and other devices for nearly 50 years. These have included procedures on both normal and neoplastic tissues, management of condylomata, endometriosis, and menometrorrhagia, and, more recently, a number of fractional laser devices have been applied for the management of genitourinary syndrome of menopause (GSM) and stress urinary incontinence (SUI), and to achieve so-called vaginal rejuvenation. Photobiomodulation therapy (PBMT) has been proposed as an alternative for use in managing GSM and SUI.

Methods: This article reviews the biological basis, symptoms, and management of GSM, and investigates the current status and rationale for the use of PBMT.

Results and conclusions: Based on the preliminary evidence available, PBMT is safe and appears to be efficacious in treating GSM.

Transurethral high-intensity ultrasound for treatment of stress urinary incontinence (SUI): simulation studies with patient-specific models

BACKGROUND

Stress urinary incontinence (SUI) is prevalent in adult women, attributed to weakened endopelvic supporting tissues, and typically treated using drugs and invasive surgical procedures. The objective of this in silico study is to explore transurethral high-intensity ultrasound for delivery of precise thermal therapy to the endopelvic tissues adjacent to the mid-urethra, to induce thermal remodeling as a potential minimally invasive treatment alternative.

METHODS

3D acoustic (Rayleigh-Sommerfeld) and biothermal (Pennes bioheat) models of the ultrasound applicator and surrounding tissues were devised. Parametric studies over transducer configuration [frequency, radius-of-curvature (ROC)] and treatment settings (power, duration) were performed, and select cases on patient-specific models were used for further evaluation. Transient temperature and thermal dose distributions were calculated, and temperature and dose metrics reported.

RESULTS

Configurations using a 5-MHz curvilinear transducer (3.5 × 10 mm, 28 mm ROC) with single 90 s sonication can create heated zones with 11 mm penetration (>50 °C) while sparing the inner 1.8 mm (<45 °C) radial depth of the urethral mucosa. Sequential and discrete applicator rotations can sweep out bilateral coagulation volumes (1.4 W power, 15° rotations, 600 s total time), produce large volumetric (1124 mm³ above 60 EM43 °C) and wide angular (∼50.5° per lateral sweep) coverage, with up to 15.6 mm thermal penetration and at least 1.6 mm radial urethral protection (<5 EM43 °C).

CONCLUSION

Transurethral applicators with curvilinear ultrasound transducers can deliver spatially selective temperature elevations to lateral mid-urethral targets as a possible means to tighten the endopelvic fascia and adjacent tissues.

1.7 micron optical coherence tomography for vaginal tissue characterization in vivo

OBJECTIVES

Optical coherence tomography (OCT) can noninvasively visualize in vivo tissue microstructure with high spatial resolution that approaches the histologic level. Currently, OCT studies in gynecology are few and limited to a conventional 1.3 μm center wavelength swept light source which provides high spatial resolution but limited penetration depth. Here, we present a novel endoscopic OCT system with improved penetration depth and high resolution.

METHODS

A novel endoscopic OCT system was developed based on a 1.7 µm swept source laser, which is capable of deeper tissue penetration due to its longer wavelength. To evaluate the performance of system, we imaged the human vaginas in vivo with both conventional 1.3 and 1.7 μm endoscopic OCT systems.

RESULTS

With the 1.7 μm endoscopic OCT system, imaging depth was improved by more than 25%, allowing better visualization of the lamina propria and clear contrast of the epithelial layer from the surrounding tissues.

CONCLUSION

The significantly improved performance of the novel 1.7 μm OCT imaging system demonstrates its potential use as a minimally-invasive monitoring tool of vaginal health in gynecologic practice. Lasers Surg. Med. 51:120-126, 2019. © 2018 Wiley Periodicals, Inc.

LASER PROBE WITH INTEGRATED CONTACT COOLING FOR SUBSURFACE TISSUE THERMAL REMODELING

Over 6.5 million women in the United States suffer from female stress urinary incontinence (SUI). Only ~200,000 women choose surgery. There may be a role for a non-surgical, minimally invasive procedure that provides thermal shrinkage/remodeling of submucosal collagen in the endopelvic fascia. This study describes design, characterization, and preliminary testing of a novel probe with integrated contact cooling for potential use in transvaginal laser treatment of SUI. Laser energy at a deeply penetrating, near-infrared wavelength of 1075 nm was delivered through a 600-μm-core fiber optic patchcord into a 90° side-firing probe head (19 × 22 mm) with integrated flow cell and sapphire window cooled to -2°C by circulating an alcohol-based solution. An inflatable balloon attached to the probe insured contact with vaginal wall. A force sensor and thermocouples monitored pressure and temperature. Thermal lesions were created in vaginal tissue of three cadavers (power = 4.6-6.4 W; spot diameter = 5.2 mm; time = 30 s). Thermal lesion areas measured 3.1-4.6 mm², while preserving the vaginal wall to a depth of 0.8-1.1 mm. Consistent tissue contact and cooling was maintained using the force sensors. Preliminary cadaver studies demonstrated subsurface treatment of endopelvic fascia with partial preservation of the vaginal wall. Future studies will optimize parameters for thermal remodeling with further tissue surface preservation.

Optical Clearing of Vaginal Tissues in Cadavers

A nonsurgical laser procedure is being developed for treatment of female stress urinary incontinence (SUI). Previous studies in porcine vaginal tissues, ex vivo, as well as computer simulations, showed the feasibility of using near-infrared laser energy delivered through a transvaginal contact cooling probe to thermally remodel endopelvic fascia, while preserving the vaginal wall from thermal damage. This study explores optical properties of vaginal tissue in cadavers as an intermediate step towards future pre-clinical and clinical studies. Optical clearing of tissue using glycerol resulted in a 15-17% increase in optical transmission after 11 min at room temperature (and a calculated 32.5% increase at body temperature). Subsurface thermal lesions were created using power of 4.6 - 6.4 W, 5.2-mm spot, and 30 s irradiation time, resulting in partial preservation of vaginal wall to 0.8 - 1.1 mm depth.

Advances in Monte Carlo Simulation for Light Propagation in Tissue

Monte Carlo (MC) simulation for light propagation in tissue is the gold standard for studying the light propagation in biological tissue and has been used for years. Interaction of photons with a medium is simulated based on its optical properties. New simulation geometries, tissue-light interaction methods, and recording techniques recently have been designed. Applications, such as whole mouse body simulations for fluorescence imaging, eye modeling for blood vessel imaging, skin modeling for terahertz imaging, and human head modeling for sinus imaging, have emerged. Here, we review the technical advances and recent applications of MC simulation.

Optical clearing of vaginal tissues, ex vivo, for minimally invasive laser treatment of female stress urinary incontinence

Near-infrared laser energy in conjunction with applied tissue cooling is being investigated for thermal remodeling of the endopelvic fascia during minimally invasive treatment of female stress urinary incontinence. Previous computer simulations of light transport, heat transfer, and tissue thermal damage have shown that a transvaginal approach is more feasible than a transurethral approach. However, results were suboptimal, and some undesirable thermal insult to the vaginal wall was still predicted. This study uses experiments and computer simulations to explore whether application of an optical clearing agent (OCA) can further improve optical penetration depth and completely preserve the vaginal wall during subsurface treatment of the endopelvic fascia. Several different mixtures of OCA’s were tested, and 100% glycerol was found to be the optimal agent. Optical transmission studies, optical coherence tomography, reflection spectroscopy, and computer simulations [including Monte Carlo (MC) light transport, heat transfer, and Arrhenius integral model of thermal damage] using glycerol were performed. The OCA produced a 61% increase in optical transmission through porcine vaginal wall at 37°C after 30 min. The MC model showed improved energy deposition in endopelvic fascia using glycerol. Without OCA, 62%, 37%, and 1% of energy was deposited in vaginal wall, endopelvic fascia, and urethral wall, respectively, compared with 50%, 49%, and 1% using OCA. Use of OCA also resulted in 0.5-mm increase in treatment depth, allowing potential thermal tissue remodeling at a depth of 3 mm with complete preservation of the vaginal wall.