Biomechanical Mapping of the Female Pelvic Floor

By Vladimir Egorov

Biomechanical Mapping of the Female Pelvic Floor explores new technological advances in women’s healthcare intended to improve pelvic floor characterization, diagnosis and prediction of treatment outcomes. The book describes biomechanical approaches and clinical examples to demonstrate how one can evaluate the changes in the pelvic floor to gain a better understanding of an individual patient’s pelvic floor dysfunctions, such as prolapse, incontinence, chronic pelvic pain, and even conditions leading to spontaneous preterm delivery and predicting maternal birth trauma.

This book is a valuable resource for researchers focused on gynecology, urogynecology or obstetrics, clinicians, graduate students and biomedical scientists and bioengineers who need to better understand the technological advances in biomechanical characterization and how they can be used not only for diagnosis but also for monitoring several OBGYN-related conditions.

• Discusses the most recent advances in the field of biomechanical characterization of soft tissues, pelvic support and function, including different applications of tactile imaging, ultrasound and magnetic resonance elastography
• Explores new diagnostic devices and techniques, mathematical models and simulations to address preoperative assessment and prediction of pelvic surgery outcomes and delivery
• Presents reviews of the results of multiple clinical studies with the biomechanical mapping of human tissues and organs to provide comprehensive information on the subject and determine future directions in the field

• Language: English
• Publisher: Academic Press
• Release date: Mar 28, 2023
• ISBN: 9780323859837

Vladimir Egorov

Vladimir Egorov, PhD, is the CEO of Advanced Tactile Imaging, a medical device developer and manufacturer whose primary area of focus is women’s healthcare including pelvic organ prolapse, stress urinary incontinence, vaginal tissue atrophy, overactive bladder, spontaneous preterm delivery, and maternal birth trauma. Dr. Egorov participated in 13 R&D projects—funded by National Institutes of Health (NIH) and Department of Defense (DoD)—related to medical devices from a feasibility study to production in FDA-audited environment and commercialization. He led the six of them as a Principal Investigator. His team developed a series of innovative devices for biomechanical charaterization of the female pelvic floor. Dr. Egorov received his MS in Biophysics from the Moscow Institute of Physics and Technology, USSR, and was granted a PhD in Biology, working at the Institute of Basic Biological Problems, Pushchino. He has over 30 years of experience in hardware, software, algorithm development and statistical data analysis, regulatory compliance and approvals (FDA, CE, TGA), and clinical studies (feasibility, development, validation). Dr. Egorov has 81 peer-reviewed research publications (78 journals and 3 book chapters) related to different aspects of academic research, instrumentation, and clinical applications. He coauthored 29 issued patents, most of them disclosing the specific details of tactile imaging technology in medical applications.

Book preview

Chapter 1: Introduction

The interactions between the anatomical structures of the female pelvic floor and their interrelated functions are among the most complex in the human body. Therefore, true understanding of how to best restore pelvic function lost due to anatomical and physiological changes can be extremely problematic. The female pelvic floor comprises a bladder with urethra for storage and evacuation of urine, a uterus with cervix, a vagina for reproductive and sexual function, and a rectum with the anus for storage and elimination of stool, along with a complicated and interdependent muscular web with its required neuronal innervation and variable connective tissues. Together, they are protected by and are structurally dependent on the surrounding pelvic bones. The multitasking and codependence of these structures create the inherent nature whereby, usually, pelvic floor disease conditions are often interrelated. The true etiology of pelvic organ prolapse and urinary incontinence and the variations observed among individuals are not entirely understood. These disorders are thought to share a common pathogenesis, weakening (elasticity changes) of the connective support tissues, and pelvic floor muscle dysfunction. Because of the various types of trauma and injury that can be sustained to the soft tissues of the pelvic floor during a vaginal delivery, along the typical degree of mechanical stress and strain to the pelvic floor with extended life expectancy, most women, if not all, have clinically relevant pelvic floor problems at some point in their lifetime.

Female pelvic floor multitasking is realized at a macrolevel because of biomechanical actions (micturition, defecation, intercourse, pregnancy, childbirth). Active muscle structures play a role as the basic drivers required to release or apply pressure for specific task completion. Passive connective tissue attachments keep the pelvic organs in the proper three-dimensional spatial orientation, so that the muscles of the pelvic floor can act on them. The complex biomechanical actions, such as urination or voluntary control of defecation, cannot be completed normally if muscular or connective tissues have altered mechanical properties (passive and/or active). As the pelvic floor muscle resting tone decreases and connective tissue (ligament) laxity ensues, a significant anatomic distortion can develop, which could decrease contractive capabilities and lead to a physiological malfunction. Even more damaging may be the avulsion of the pelvic floor muscle and/or connective tissue disruption. All these pelvic dysfunctions and anatomical changes of pelvis soft tissues and structures occur because of biomechanical changes. It requires a repair, which can be effective in the mid and long term only if ‘a repairer’ has an accurate knowledge of the problem(s) (diagnosis) and can objectively predict the consequences of the applied treatment(s) whether it will be conservative or surgical treatment.

A significant gap exists in biomechanical and functional research on the female pelvic floor. In 2018, The American Urogynecologic Society (AUGS) conducted a survey among the leaders in the field, including clinicians, clinical and basic science researchers, and representatives from government agencies, industry, patient advocacy groups, and the public. The objective was to identify and prioritize critical areas of need for future research. According to the survey, mechanistic research on pelvic supportive structures (first place), clinical research to optimize outcomes after pelvic prolapse surgery (fourth place), and evidence-based quality measures for prolapse outcomes (fifth place) are among the main needs. Further, this AUGS panel stated that For pelvic organ prolapse, there is a need to describe the interdependence of load-bearing structures such as levator ani muscles, connective tissue, and nerves because these structures relate to the bony anatomy and to the proposed components of pelvic support. Furthermore, there is a need to understand how expulsive forces are applied and distributed. These questions are highly relevant due to the 5 year past failure rate for pelvic organ prolapse surgery as high as 70% as demonstrated in a representative study.

Substantial improvement in women's healthcare is possible with better precision in imaging, advanced computational methods, improved tissue modeling, and the development of noninvasive biomechanical measurement methods. Personalized medicine would be achievable with the development of patient-specific treatment and rehabilitation protocols based on predictive models created from each patient's specific anatomy, biomechanical mapping, physiology, and pathophysiology. Sophisticated models, built with accurate biomechanical inputs, could be used to predict a spontaneous preterm delivery, maternal birth trauma, prolapse, and urinary incontinence development. Advanced computational analysis methods offer the promise of multiscale modeling methodologies to simulate organs and tissues. These methods along with the new tactile (stress, function) and ultrasound (anatomy, strain, function) imaging devices would enable the validation of available theories, such as the hammock and integral theory, and further development of biomechanical and functional theory of the pelvic floor. Treatments based on these theories could be tested quantitatively in scaled clinical trials to evolve into patient-specific approaches. Biomechanical integrity assessment of the pelvic floor and then tailoring treatment of its biomechanical dysfunction is the logical route to improve clinical success. This opens up new possibilities for the quantitative biomechanical valuation and monitoring of pelvic floor conditions.

The intent of this book is to summarize the recent progress in biomechanical characterization of the female pelvic floor and highlight the future directions that may have significant clinical impacts. The description of biomechanical approaches and clinical examples demonstrate how one can evaluate the changes in the mechanical conditions of the of the pelvic floor to gain a better understanding of an individual patient's pelvic floor dysfunction and thereby ultimately improve guidance toward an optimal selection from the various surgical and nonsurgical therapeutic choices available. The emphasis in this book is on transvaginal biomechanical mapping as an imaging and diagnostic tool to characterize the wide spectrum of pelvic diseased conditions. Specifically, this technology is applicable for detection and characterization of prolapse, incontinence, chronic pelvic pain, pathologies that include endometriosis, adenomyosis and uterine fibroids, cervical and ovarian cancer, and even conditions leading to spontaneous preterm delivery and predicting maternal birth trauma.

This text is designed to convince gynecologists about the application of available technical tools for quantitative pelvic floor characterization in annual examinations for early detection of the diseased conditions. To persuade the urogynecologists to extend their professional horizon to biomechanical aspects of the female pelvic floor, they are trying to reconstruct or improve every surgical procedure. This text is also designed to inform the obstetricians on technological progress related to the birth canal characterization, coming possibilities in the detection of cervical conditions leading to spontaneous preterm delivery, and establishing a relationship between the antepartum biomechanical conditions of the pelvis with applied intrapartum procedures and maternal injuries. This text is also meant to provide a go-to reference for those interested in studying pelvic floor biomechanics, imaging/measurement methods, and modeling (predictive and finite element). Another goal of this text is to be used in a course on biomechanics with pelvic floor examples of the concepts presented. Therefore, medical school students could master the fundamental aspects of their future practical skills. Finally, this text is designed to allow future investigators to continue the development, clinical validation, and practical implementation of the devices and methods that improve women's health.

With this in mind, Chapter 2 establishes definitions of key matters and concepts used further in the text; Chapter 3 provides retrospective history and medical applications for the biomechanical mapping of soft tissues including elastography; Chapter 4 outlines the current state of art in biomechanical mapping with ultrasound and magnetic resonance imaging and its applicability to the female pelvic floor; Chapter 5 reviews the pelvis characterization with force and pressure measurements; Chapter 6 discusses in details application of vaginal tactile imager for characterization of tissue elasticity, pelvic support, and function including data interpretation with clinical examples; Chapter 7 introduces a new paradigm—Biomechanical Integrity score—for the female pelvic floor including its clinical validation; Chapter 8 demonstrates the possibility of the biomechanical mapping in prediction of an outcome of prolapse surgery; Chapter 9 describes changes in pelvic floor integrity after hysterectomy; Chapter 10 highlights vaginal conditions after laser treatment; Chapter 11 reports a unique fusion of tactile and ultrasound imaging in one probe and its clinical perspectives; Chapter 12 relates to the use of biomechanical mapping to characterization of cervical deficiency and prediction of spontaneous preterm delivery; Chapter 13 demonstrates a possibility of antepartum tactile imaging in characterization of critical pelvic structures before the delivery and its perspective in risk assessment of maternal injuries; and finally Chapter 14 brings conclusions and future directions for the biomechanical mapping developments and clinical applications. Further impartments in the women's healthcare would only be possible with the development of precise imaging techniques, and novel methods of biomechanical characterization of the female pelvic floor.

In a future scenario, a patient with pelvic organ prolapse would undergo biomechanical imaging diagnostic tests, the results of which would be fed into a patient-specific biomechanical model that could rapidly simulate multiple treatment options, including conservative and surgical repairs, to select a justified optimal treatment for that patient. Medical imaging and biomechanical testing might be offered to a pregnant woman, and computational analysis may be applied to determine optimal labor and delivery scenarios to minimize the risk of childbirth related pelvic floor injuries.

The biomechanical mapping developments and clinical research described in this book would not be possible without the support and participation of scientific, engineering, programming, analytical, and clinical professionals. The first in this row is Armen Sarvazyan, Ph.D., DSc, recipient of EEE UFFC Rayleigh Award and ASA Helmholtz-Rayleigh Medal, a foreign member of Russian Academy of Science, the inventor of mechanical imaging and shear wave ultrasound imaging. He inspired elasticity imaging research more than 25 years ago in the United States. The engineering team working on mechanical, tactile, and ultrasound imaging developments included Brendan Corbin, Sergey Tsyuryupa, Ph.D.; Milind Patel, Aleskandr Pasechnik, Tomasz Wojtera, Alexandr Povar, and Brendan Francy. Firmware, software, and electronics developments were possible due to Sergiy Kanilo, Ph.D.; Viktors Kurtenoks, Petr Tokar, Ph.D.; and Alex Merzhevskiy. Drs. Stanislav Emelianov, Marianna Alperin, and Salavat Aglyamov were consultants on critical development aspects and finite element modeling. The clinical research with the tactile imaging devices was conducted under the guidance of Heather van Raalte, MD; Vincent Lucente, MD, MBA; Peter Takacs, MD, Ph.D., MBA; Seyed A. Shobeiri, MD; Lennox Hoyte, MD; Todd Rosen, MD; Meena Khandelwal, MD; Jorge Tolosa, MD; Vladimir Kalis, MD, Ph.D.; and Zdenek Ruzavy, MD, PhD. Scientific and significant administrative contributions were made by Noune Sarvazyan, Ph.D., MBA, overseeing clinical research, IRB approves government agencies' communication. Clinical studies would have been impossible without the coordination and assistance provided by Robin Haff, Eileen Taff, Alison Shaltis, Rachel Grabe, Renee Brenned, Shama Khan, and Nina Egorova. Finally, we acknowledge the support of the National Institute on Aging and Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health under Awards Numbers R44AG034714, R44HD090793, R43HD095223, R44HD097805, and SB1AG034714, and by the Department of Defense (DoD) through the Broad Agency Announcement (BAA), for Extramural Medical Research, under Award No. W81XWH1920018. The content of the clinical results is solely the responsibility of the author and does not necessarily represent the official views of the National Institutes of Health. The opinions, interpretations, conclusions, and recommendations are those of the author and are not necessarily endorsed by the Department of Defense. Enjoy your reading.

Vladimir Egorov, Ph.D.

Princeton, NJ, USA.

Chapter 2: Definitions and interpretation of biomechanical mapping

Abstract

This chapter provides definitions of terms used in this book. Among them, the new concepts of tactile imaging, functional tactile imaging, tactile ultrasound image fusion, biomechanical mapping, and biomechanical integrity are presented. It delivers comments and interpretations whenever it is reasonable for further understanding. A full list of used abbreviations is also included. Shortly, the new devices, developed within the scope of the biomechanical mapping project, are described.

Keywords

Biomechanical integrity; Biomechanical mapping; Functional tactile imaging; Mechanical imaging; Soft tissue elasticity; Tactile imaging; Tactile ultrasound image fusion

Introduction

The characterization of any complex life system must include the selection of key components that play a significant role in physiological processes. In this consideration, we will pay attention to the new technological approaches to characterize tissues, structure, and related active biomechanical aspects of the pelvic muscles, as described in the published literature relevant to functional anatomy of the female pelvic floor [1–5].

Definitions

From classical mechanics, we know that to characterize an object as a mechanical system and its mechanical properties, a great number of parameters are needed. These include the shear and Young's moduli, bulk compressional modulus, nonlinearity, Poisson's ratio, viscosity, poroelastic parameters, hysteresis, anisotropy, and heterogeneity indices [6–8]. At first glance, this requirement does not look realistic to meet. However, over the centuries, soft tissue palpation has become the most prevalent and successful medical diagnostic technique [9]. Two critical factors explain this: (1) detection of a mechanical heterogeneity by manual palpation is based exclusively on sensing the variations in the Young's modulus (E) of tissue (or shear elasticity modulus, which is approximately equal to E/3 for soft tissues), and (2) the elasticity modulus varies by hundreds of percentages during the development of pathological or diseased conditions in the soft tissues [10–12]. The key terms related to soft tissue elasticity require additional explanation to understand the technological approaches described in this book.

Basic concepts

Pressure

Pressure is the force applied per unit area to an object or a portion of the object. Here, pressure refers to the cause of soft tissue deformation as a force (pressure) is applied to the tissue surface. The units of pressure include force (Newton) per unit area (square meter) [N/m²] (called Pascals or Pa). Other units of pressure, such as cmH2O and mmHg (millimeter of mercury), are also used; e.g., 1mmHg=0.0075Pa. Pressure is a scalar described by magnitude alone. Force is a vector; it has a magnitude and a direction.

Stress

Stress is the force that neighboring particles of a continuous material exert on each other. Stress refers to the cause of the tissue deformation. The unit of stress here is force (Newton) per unit area (square meter) [N/m²] or [Pa]. Stress is a vector described by both magnitude and a direction.

Strain

Strain is the measure of the deformation of the material under applied load (pressure or stress). Strain may characterize deformation of a soft tissue surface or displacement of internal particles. Strain is expressed as the ratio of total deformation to the initial dimension of the object. Strain is dimensionless [m/m].

Elasticity

In mechanics, elasticity is the ability of a material to resist applied stress and to return to its original shape when the stress is removed. The elastic moduli characterize the ability to resist the applied stress as an intrinsic property of a specific material [6–8]. If the deformed tissue has returned by 98% to its initial size, is it elastic? Yes, it is elastic; it just may require additional characterization. A perfect (100%) elastic material is an illusory approximation of the real world. In the case of one-dimensional (1D) deformation of a uniform object, the stress to strain ratio is the Young's modulus [stress/strain=N/m²/m/m=Pa] (Hooke's law). Many materials, including human soft tissues, noticeably deviate from Hooke's law well before their elastic limits (tissue break) are reached. However, the stress to strain ratio directly characterizes the soft tissue elasticity.

Stiffness

Stiffness is the ability of an elastic object to resist an applied force. Stiffness is not a function of the material alone, but is also influenced by the object shape. It might be measured as the ratio of the applied force (Newton) per object linear compression or elongation (meter) [N/m]. However, this term cannot be considered a scientifically justified descriptor. It is often used in everyday life.

Elastography

Elastography or Elasticity Imaging is a medical imaging modality that maps the mechanical properties of soft tissues and/or functions of organs or structures in a body. It may cover the functions which are related or depend to the mechanical properties of soft tissues.

Mechanical imaging

Mechanical imaging is a modality of medical diagnostics based on the reconstruction of tissue structure and viscoelastic properties using mechanical sensors. The essence of mechanical imaging is the solution to an inverse problem using the data of stress patterns on the surface of the tissue compressed by a pressure sensor array. A key feature of mechanical imaging is ‘knowledge-based imaging.’ To produce a 3D image, the computer uses both the measured parameters of an individual examined object and a general database on the anatomy and pathology of the object [13,14].

Tactile imaging

Tactile imaging is a medical imaging modality that translates the sense of touch into a digital image. The tactile image is a function of P(x,y,z), where P is the pressure on the soft tissue surface under the applied deformation, and x, y, and z are coordinates where pressure P was measured. The tactile image is a pressure map, on which the direction of tissue deformation is specified [15].

Functional tactile imaging

Functional tactile imaging is a variation of tactile imaging that translates the muscle activity into a dynamic pressure pattern P(x,y,t) for an area of interest, where t is time and x and y are coordinates where pressure P was measured [15].

Biomechanical integrity score

Biomechanical integrity score (BI-score) of the female pelvic floor is an integral parameter composed of five components: (1) tissue elasticity, (2) pelvic support, (3) pelvic muscle contraction, (4) involuntary muscle relaxation, and (5) pelvic muscle mobility [16]. Each component is further composed of a set of relevant biomechanical parameters. The tactile imaging probe allows the acquisition of all information needed for the BI-score calculation.

Tactile ultrasound measurements

Tactile and ultrasound measurements include dynamic stress data on the tissue surface and acoustic waveforms came from the tissue under the study.

Tactile ultrasound image fusion

Tactile and ultrasound image fusion has multiple aspects [17]. Specifically, it may be:

• Superposition of tactile image with ultrasound image to identify anatomical structures making contribution into the tactile image for tissue elasticity assessment.

• Superposition of tactile image with ultrasound image to identify anatomical structures (pelvic muscles) making contribution into the pelvic floor support.

• Superposition of 3D ultrasound image with 2D/3D pressure pattern for the entire vagina to identify affected locations and structures in the pelvic floor.

• Superposition of dynamic ultrasound image with dynamic pressure pattern to identify affected locations and structures in the pelvic floor.

Biomechanical mapping

Biomechanical mapping of the female pelvic floor inlcudes one of the listed technological approaches or their combination (Fig. 2.1):

• Tactile imaging

• Functional tactile imaging

• Tactile ultrasound measurements

• Tactile ultrasound image fusion

• Ultrasound Elastography

• Magnetic Resonance Elastography

BI-score calculation requires at least two components—tactile imaging and functional tactile imaging.

Biomechanical mapping devices

Vaginal Tactile Imager

Vaginal Tactile Imager (VTI) device allows tactile imaging and functional tactile imaging of the female pelvic floor. It automatically calculates the BI-score, its five components, and 50+ biomechanical parameters (see Chapter 6).

Vaginal Tactile Ultrasound Imager

This device allows tactile imaging, functional tactile imaging, and ultrasound imaging of the female pelvic floor. It automatically calculates the BI-score, its five components, and 60+ biomechanical parameters (see Chapter 11).

Cervix Monitor

This device allows tactile ultrasound measurements of cervical elasticity and length (see Chapter 12).

Figure 2.1  Biomechanical mapping of the female pelvic floor and its components.

Antepartum Tactile Imager

This device allows tactile imaging and elasticity characterization of the perineum, levator ani, and measurement of a critical distance between the perineum and pubic bone (see Chapter 13).

Laparoscopic Tissue Monitor

This device allows tactile ultrasound measurements of soft tissue during laparoscopic surgery (see Chapter 14).

Vaginal Tactile Electromyographic Imager

This device allows tactile imaging, functional tactile imaging, and electromyographic imaging of the female pelvic floor (see Chapter 14).

Comments and interpretations

Pressure response patterns are measured with a pressure sensor array by applying a probe to the surface of a soft tissue object, to allow the acquisition of the stress data. If we know the exact displacement coordinates (the strain) of every pressure sensor during the tissue deformation, we can map the pressure response data in this coordinate continuum to obtain stress–strain map or tactile image. It seemed that a tactile image can be acquired not only for tissue compression by a probe with pressure/tactile sensors, but also for probe sliding over lubricated soft tissue or a combination of compression and sliding. Such an approach allows compositing a 3D tactile image that looks similar to the original structure and allows its elasticity assessment. The tactile compound image integration is also possible if the object exceeds the probe size [18,19]. A tactile imaging probe has a pressure sensor array mounted on its face that acts similarly to human fingers during a clinical examination, deforming the soft tissue and detecting the resulting changes in the pressure pattern on the surface. The probe is moved over the surface of the tissue to be studied, and the pressure response is evaluated at multiple locations along the tissue. The results are used to generate 2D or 3D images showing the pressure distribution over the area of the tissue under the study.

Generally, an inverse problem solution for a 3D tactile image P(x,y,z) would allow reconstruction of the tissue elasticity distribution as a function of the coordinates x, y, and z. Unfortunately, the inverse problem solution is hardly possible for most real objects because it is a nonlinear and ill-posed problem. However, the tactile imaging reveals tissue or organ anatomy and elasticity distribution because it keeps the stress–strain relationship for deformed tissue [18,19]. It appears that the 3D tactile image can be transformed into an elasticity image with the use of a linear transformation for a region of interest. That means, in general, the spatial gradients ∂P(x,y,z)/∂x, ∂P(x,y,z)/∂y, and ∂P(x,y,z)/∂z can be used in practical applications for a quantitative assessment of soft tissue elasticity despite structural and anatomical variations [15]. Another approach for elasticity assessment from tactile images is the use of a set of direct solutions of a finite element model for a specific anatomy [20].

Tactile imaging, applied to the female pelvic floor, allows the characterization of soft tissue elasticity and pelvic floor support. Muscle activity to be studied may include a voluntary contraction (e.g., pelvic floor squeeze), involuntary reflex contraction (e.g., due to a cough), involuntary relaxation, or a Valsalva (veering down) maneuver [21]. The functional tactile imaging is similar to the high-definition manometry used for muscle contraction studies along the gastrointestinal tract. With this approach, muscle strength (MS) is calculated as the difference between maximum pressure amplitude P 2 (x), as measured by the VTI probe at muscle contraction (voluntary or involuntary) and pressure amplitude P 1 (x) in the same location x at muscle rest. That means MS = P 2 (x)–P 1 (x).

Functional tactile imaging, applied to the female pelvic floor, allows the characterization of muscle contractive activities and innervation.

BI-score of the female pelvic floor characterizes the pelvic as the system with complex internal interrelations. It is essential that the BI-score, as well as its five components, are presented in the units of standard deviation relatively the normal conditions of the pelvic floor. This way, any deviation from age-adjusted normal BI-score line can be interpreted as beginning or developed deterioration of appropriate aspect(s) within the pelvis [16].

Summary

The descriptions in this chapter of known and new concepts and interpretations must help in reading this book.

Abbreviations

2D    Two-dimensional

3D    Three-dimensional

AMA    American Medical Association

ANOVA    Analysis of Variance

aOR    Adjusted odds ratio

ARA    Anorectal angle

ARFI    Acoustic radiation force impulse

ATFP    Arcus tendineus fascia pelvis ligament

ATM    Antepartum tactile monitor

AUC    Area under the ROC curve

AVW    Anterior vaginal wall

BI-score    Biomechanical integrity score

BMD    Bone mineral density

BMI    Body mass index

BTI    Breast tactile imager

C    Cervix

CDC    Centers for Disease Control and Prevention

CI    Confidence interval

CL    Cardinal ligament

CM    Cervix Monitor

CS    Cesarean section

DC    Direct current

DPA    Digital pelvic floor assessment

DRE    Digital rectal examination

DTG    Draw tower grating

DTI    Diffusion tensor imaging

DWI    Diffusion-weighted imaging

E    Young's modulus

EC    Endometrial carcinoma

EI    Elasticity imaging

EVUS    Endovaginal ultrasonography

FBG    Fiber-Bragg grating

FDA    Food and drug administration

FIGO    Federation international of gynecology and obstetrics

FSFI    Female sexual function index

ICC    Intraclass correlation coefficient

ICM    Ilicoccygeal muscle

IMC    Involuntary muscle contraction components

IOL    Induction of labor

IRB    Institutional review board

IVPS    Intravaginal pressure sensor

IVT    Intravaginal pressure transducer

kPa    Pa×1000

LAM    Levator ani muscle

LP    Levator plate

LTM    Laparoscopic Tissue Monitor

m    Meter (unit of distance)

MCID    Minimal clinically important difference

MFMU    Maternal-fetal medicine units network

mm    Millimeter

mmHg    Millimeter of mercury (unit of pressure)

MOS    Modified oxford scale

MRE    Magnetic resonance elastography

MRFD    Maximal rate of force development

MRI    Magnetic resonance imaging

MRR    Muscle relaxation rate

MS    Muscle strength

MTrPs    Myofascial trigger points

MVS    Voluntary pelvic floor muscle contraction

N    Newton (unit of force)

NICHD    Eunice Kennedy Shriver National Institute of Child Health and Human Development

OAB    Overactive bladder

OASI    Obstetric anal sphincter injury

P    Pressure

Pa    Pascal (unit of pressure)

PAM    Puboanal muscle

PB    Pubic bone

PCB    Printed circuit board

PCC    Pubococcygeal muscle

PFDI    Pelvic floor distress inventory

PFM    Pelvic floor muscles

PMI    Prostate mechanical imager

POP    Pelvic organ prolapse

POP-Q    Pelvic organ prolapse quantification

PPM    Puboperineal muscle

PRM    Puborectal muscle

PS    Symphysis pubis

pSWE    Point shear wave elastography

PUL    Pubourethral ligament

PVM    Pubovaginal muscle

RF    Radiofrequency

ROC    Receiver operating characteristic

RTR    Resting tissue resistance

s    Second

SE    Strain elastography

SEM    Standard error of measurement

SPTD    Spontaneous preterm delivery

SSI    Supersonic shear imaging

SUI    Stress urinary incontinence

SWE    Shear wave elastography

SWEI    Shear wave elasticity imaging

TE    Tissue elastometer

TI    Tactile imaging

TIEMG    Vaginal Tactile Electromyographic Imager

TIUSv    Vaginal Tactile Ultrasound Imager

TME    Tissue micro elastometer

TRUS    Transrectal ultrasound

U    Urethra

UE    Ultrasound elastography

UI    Urinary incontinence

USL    Uterosacral ligament

VAS    Visual analog scale

VHI    Vaginal health index

VSQ    Vulvovaginal symptom questionnaire

VTI    Vaginal Tactile Imager

WHO    World Health Organization

∂P(y)/∂y    Derivative (Spatial Gradient)

References

1. Shobeiri S. Pelvic floor anatomy. In: Practical pelvic floor ultrasonography: a multicompartmental approach to 2D/3D/4D ultrasonography of the pelvic floor. 2nd ed. New York: Springer International