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- •Foreword
- •Preface
- •Acknowledgments
- •Contents
- •Contributors
- •Introduction
- •Tissue Characteristics
- •Ovarian Scanning
- •Embryo/Fetus Susceptibility
- •References
- •Instrument Outputs
- •The Output Indices
- •Introduction
- •Limitations
- •History
- •Conclusions
- •References
- •Introduction
- •Endometrial Blood Flow
- •Ovarian Stromal Blood Flow by 2D Doppler
- •Ovarian Stromal Blood Flow by 3D Doppler
- •Conclusion
- •References
- •Transabdominal Ultrasound
- •Transvaginal Ultrasound
- •Postmenopausal Ovaries
- •Premenarchal Ovaries
- •Reproductive Age Ovaries
- •Antral Follicle Count (AFC)
- •References
- •Ovarian Cysts
- •Conclusion
- •References
- •6: PCOS
- •The Polycystic Ovarian Morphology (PCOM)
- •Ovarian Volume
- •Ovarian Stromal Blood Flow
- •Future Points
- •References
- •7: The Normal Uterus
- •Uterus
- •Myometrium
- •Endometrium
- •Cervix
- •References
- •8: Congenital Uterine Anomalies
- •Introduction
- •Müllerian Agenesis
- •Unicornuate Uterus
- •Uterus Didelphys
- •Bicornuate Uterus
- •Septate Uterus
- •Arcuate Uterus
- •Hysterosalpingography
- •Two-Dimensional Ultrasonography
- •Pelvic Magnetic Resonance Imaging
- •Three-Dimensional Ultrasonography
- •Urinary Tract Imaging
- •Conclusion
- •References
- •9: Uterine Fibroids
- •Background
- •Ultrasound
- •Saline Infusion Sonohysterography
- •Magnetic Resonance Imaging
- •Observation
- •Medical Therapies
- •Myomectomy
- •Hysteroscopic Myomectomy
- •Abdominal Myomectomy
- •Laparoscopic Myomectomy
- •Uterine Artery Embolization
- •MRgFUS
- •Conclusion
- •References
- •10: Uterine Polyps
- •Endometrial Polyps
- •Interrupted Mucosa Sign
- •Sonoelastography (SE)
- •Sonohysterography
- •Cervical Polyps
- •References
- •11: Intrauterine Adhesions
- •Introduction
- •Incidence
- •Manifestation
- •Causes
- •Risk Factors
- •Diagnosis
- •Hysteroscopic Surgery
- •Treatment Outcome
- •Radiographic Methods
- •Mechanical Barriers
- •Fluid Barriers
- •Tissue Barriers
- •Prevention Strategies
- •Recent Advances
- •Conclusion
- •Introduction
- •SHG Procedure [1, 2, 6, 13]
- •2D Versus 3D SHG
- •References
- •Gel Instillation SHG
- •SHG Versus Hysteroscopy
- •Conclusion
- •References
- •Introduction
- •Scrotal Ultrasonography
- •Paratesticular Structures
- •Epididymis
- •Varicocele
- •Vas Deferens
- •Testicular Ultrasound
- •Cryptorchidism
- •Cysts, Hydrocele, Infectious Processes
- •Testicular Masses
- •Microlithiasis
- •Testicular Torsion/Trauma
- •Transrectal Ultrasonography
- •Prostate
- •Cysts
- •Ejaculatory Duct Obstruction
- •Seminal Vesicles
- •Assisted Reproductive Techniques
- •Conclusion
- •References
- •Hysterosalpingography (HSG)
- •The Technique
- •Three-Dimensional Coded Contrast Imaging (3D CCI) During HyCoSy
- •Conclusion
- •References
- •Premature Luteinization
- •Multiple Pregnancies
- •Polycystic Ovarian Syndrome (PCOS)
- •Ultrasound Diagnosis [17]
- •Ovaries
- •Follicles
- •Clomiphene Citrate
- •Gonadotropins
- •Conclusion
- •References
- •Introduction
- •Normal Folliculogenesis
- •Monitoring Follicular Maturation
- •Standard Ultrasound Monitoring Program
- •Self-Monitoring
- •Conclusion
- •References
- •17: SonoAVC (Sonographic-Based Automated Volume Count)
- •Introduction
- •How Does One Apply SonoAVC?
- •Follicular Monitoring
- •Case 1
- •Case 2
- •Case 3
- •Antral Follicle Count
- •References
- •18: Ultrasound-Guided Surgical Procedures
- •Introduction
- •Uterine Septum
- •Submucosal Fibroids
- •Synechiae
- •Intrauterine Foreign Bodies
- •Hematometra
- •Summary
- •Ovarian Cyst Aspiration
- •Hydrosalpinx Aspiration
- •Oocyte Retrieval
- •Endometrial Thickness
- •Embryo Transfer
- •Conclusion
- •References
- •References
- •Introduction
- •Clinical Touch ET Versus Transabdominal US-Guided ET
- •Conclusion
- •References
- •General Concepts
- •Patient’s Acceptance
- •Contraindications
- •Radiation
- •Image Post-Processing
- •Conclusion
- •References
- •Introduction
- •A Quick Look Back at Endometrial Assessment Approaches
- •Receptive
- •Non-receptive
- •Improving Endometrial Receptivity Assessment
- •References
- •List of Relevant Websites
- •23: Early Pregnancy Ultrasound
- •Introduction
- •Pregnancy Location
- •Gestational Sac (GS)
- •Yolk Sac (YS)
- •Embryonal Heart Rate (EHR)
- •Pregnancy Dating
- •Pregnancy Viability
- •Conclusion
- •References
- •24: Ectopic Pregnancy
- •Cervical Pregnancy
- •Ovarian Pregnancy
- •Abdominal Pregnancy
- •Cesarean Scar Ectopic Pregnancy
- •Interstitial Ectopic Pregnancy
- •Ectopic After Hysterectomy
- •Summary
- •References
- •Index

Contents
Part I Safety in Ultrasound
1 Ultrasound in Reproductive Medicine: Is It Safe? . . . . . . . . . . . 3
Jacques S. Abramowicz
Part II Ultrasound Techniques
2 Basics of Three-Dimensional Ultrasound
and Applications in Reproductive Medicine . . . . . . . . . . . . . . . . . 21
Maximilian Murtinger and Maximilian Schuff
3 Two-Dimensional and Three- Dimensional Doppler
in Reproductive Medicine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Ernest Hung Yu Ng
Part III Ultrasound of the Ovary
4 The Normal Ovary: Changes in the Menstrual Cycle . . . . . . . . . 59
Renato Bauman and Ursula Res Muravec
5 Ultrasound and Ovarian Reserve . . . . . . . . . . . . . . . . . . . . . . . . . 75
Laurel A. Stadtmauer, Mai Tran, Alessandra Kovac,
and Ilan Tur-Kaspa
6 PCOS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Ana M. Monzo, Nikolaos Prapas, and Artemis Karkanaki
Part IV Ultrasound of the Uterus
7 The Normal Uterus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
Khaled Sakhel, Alfred Z. Abuhamad,
and Callum Andrew Potts
8 Congenital Uterine Anomalies . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
Beth W. Rackow
9 Uterine Fibroids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
Bradley S. Hurst
xiii

xiv
10 Uterine Polyps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
Silvina M. Bocca, Bijan Morshedi, and Alena D. Naumova
11 Intrauterine Adhesions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
Gautam Nand Allahbadia, Akanksha Allahbadia Gupta,
and A. H. Maham
12 Sonohysterography (SHG) in Reproductive Medicine . . . . . . . . 199
Ilan Tur-Kaspa, Alberto Revelli, Laurel A. Stadtmauer,
and David P. Cohen
Part V Ultrasound and Male Infertility
13 Ultrasound in Male Infertility . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
Isaac Samuel Lam, Landon W. Trost, David D. Casalino,
and Robert E. Brannigan
Part VI Ultrasound and ART Techniques
14 Evaluation of Tubal Patency (HyCoSy, Doppler) . . . . . . . . . . . . . 239
Kamal Ojha, Tuhina Goel, and Dimuthu Vinayagam
15 Ultrasound in Follicle Monitoring
for Ovulation Induction/IUI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249
Josef Blankstein, Peter Aziz, Shumal Malepati,
and Jawaria Amir
Contents
16 2D Ultrasound in Follicle Monitoring for ART . . . . . . . . . . . . . . 273
Gianluca Gennarelli, Tomer Tur-Kaspa, Alberto Revelli,
Mette Toftager, and David P. Cohen
17 SonoAVC (Sonographic-Based Automated Volume Count) . . . . . 285
Adela Rodrıguez-Fuentes, Jairo Hernández,
Jean Paul Rouleau, and Angela Palumbo
18 Ultrasound-Guided Surgical Procedures . . . . . . . . . . . . . . . . . . . 305
Audrey M. Marsidi, Donna R. Session,
and Jennifer Fay Kawwass
19 Ultrasound and Ovarian Hyperstimulation Syndrome . . . . . . . . 321
Laura P. Smith
20 Ultrasound Guidance in Embryo Transfer . . . . . . . . . . . . . . . . . . 335
Alberto Revelli, Tomer Tur-Kaspa, and Edmond Conno
21 Virtual Hysterosalpingography: A Noninvasive
Diagnostic Technique for the Evaluation
of the Female Reproductive Tract . . . . . . . . . . . . . . . . . . . . . . . . . 345
Patricia Carrascosa, Carlos Capuñay, Juan Mariano Baronio,
and Carlos E. Sueldo

Contents
xv
22 Modern Evaluation of Endometrial Receptivity . . . . . . . . . . . . . 357
Jose Miravet-Valenciano, Maria Ruiz-Alonso,
and Carlos Simón
Part VII Ultrasound and Pregnancy
23 Early Pregnancy Ultrasound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369
Laura Detti
24 Ectopic Pregnancy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381
Donald L. Fylstra
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395

Contributors
Jacques S. Abramowicz, MD, FACOG, FAIUM Ultrasound Services,
Fetal and Neonatal Care Center, University of Chicago, Department of
Obstetrics and Gynecology, Chicago, IL, USA
Alfred Z. Abuhamad, MD Department of Obstetrics and Gynecology,
Eastern Virginia Medical School, Norfolk, VA, USA
Gautam Nand Allahbadia, MD Reproductive Endocrinology & IVF,
Millennium Medical Center IVF, Jumeirah, Dubai, UAE
Reproductive Endocrinology & IVF, Bourn Hall IVF, Jumeirah, Dubai, UAE
Reproductive Endocrinology & IVF, Orchid Fertility & Andrology Services,
DHCC, Dubai, UAE
Reproductive Endocrinology & IVF, Dr. Amal Elias Fertility Center,
Dubai, UAE
Reproductive Endocrinology & IVF, Canadian Specialist Hospital, Abu Hail,
Dubai, UAE
Reproductive Endocrinology & IVF, Indo Nippon IVF, Mumbai, India
Rotunda – The Center For Human Reproduction, Mumbai, India
Medical Education & Research, ISRME, Mumbai, India
Medical Education & Research, Indira IVF, Udaipur, India
JawariaAmir, MD Rosalind Franklin University of Medicine and Science,
The Chicago Medical School, Chicago, IL, USA
Peter Aziz, MD Mount Sinai Hospital, Department of Obstetrics and
Gynecology, Chicago, IL, USA
Juan Mariano Baronio, MD Department of Fertility, CEGYR, Buenos
Aires, Argentina
Renato Bauman, MD, PhD Rotunda IVF, The National Fertility Centre,
The Rotunda Hospital, Dublin, Ireland
Josef Blankstein, MD Rosalind Franklin University of Medicine and
Science, Chicago, IL, USA
Mount Sinai Hospital, Department of Obstetrics and Gynecology, Chicago,
IL, USA
xvii

xviii
SilvinaM.Bocca, MD, PhD, HCLD The Jones Institute for Reproductive
Medicine, Eastern Virginia Medical School, Department of Obsterics and
Gynecology, Norfolk, VA, USA
RobertE.Brannigan, MD Northwestern Memorial Hospital, Department
of Urology, Chicago, IL, USA
CarlosCapuñay, MD Department of Computed Tomography and Magnetic
Resonance, Diagnóstico Maipú, Buenos Aires, Argentina
PatriciaCarrascosa, MD, PhD, FSSCT Department of Computed Tomography
and Magnetic Resonance, Diagnóstico Maipú, Buenos Aires, Argentina
David D. Casalino, MD Northwestern University School of Medicine,
Department of Radiology, Chicago, IL, USA
DavidP.Cohen, MD, FACOG Institute for Human Reproduction, Chicago,
IL, USA
Edmond Conno, MD Feinberg School of Medicine, Northwestern
University, Chicago, IL, USA
Laura Detti, MD University of Tennessee Health Science Center,
Department of Obstetrics and Gynecology, Memphis, TN, USA
DonaldL.Fylstra, MD Department of Obstetrics and Gynecology, Medical
University of South Carolina, Charleston, SC, USA
Contributors
GianlucaGennarelli, MD, PhD Sant’Anna Hospital, University of Turin,
Department of Obstetrics and Gynecology, Turin, Italy
TuhinaGoel, MD, DNB All India Institute of Medical Sciences, New Delhi,
India
Department of Obstetrics and Gynaecology, Saharanpur, Uttar Pradesh, India
AkankshaAllahbadiaGupta, MS Indira IVF, New Delhi, India
JairoHernández, PhD Centro de Asistencia a la Reproducción Humana de
Canarias, San Cristobal de La Laguna, Spain
BradleyS.Hurst, MD Carolinas Medical Center, Department of Obstetrics
and Gynecology, Reproductive Endocrinology and Infertility, Charlotte, NC,
USA
ArtemisKarkanaki, MD, MSc, PhD Third Department of Obstetrics and
Gynecology, Hippokratio General Hospital of Thessaloniki, Thessaloniki,
Greece
Aristotle University of Thessaloniki, Thessaloniki, Greece
Jennifer Fay Kawwass, MD Emory Reproductive Center, Atlanta, GA,
USA
Emory University, Department of Reproductive Endocrinology and Infertility,
Atlanta, GA, USA

Contributors
xix
Alessandra Kovac, MPH Center for Biostatistics in AIDS Research at
Harvard T.H. Chan School of Public Health, Boston, MA, USA
Isaac Samuel Lam, BA Northwestern University Feinberg School of
Medicine, Department of Urology, Chicago, IL, USA
A.H.Maham, MBBS Millennium Medical Center IVF, Dubai, UAE
ShumalMalepati, MD Trios Medical Group– Obstetrics & Gynecology,
Kennewick, WA, USA
AudreyM.Marsidi, MD Emory University Hospital Midtown, Department
of Gynecology and Obstetrics, Atlanta, GA, USA
JoseMiravet-Valenciano, MSc Igenomix, Valencia, Spain
Ana M. Monzo, MD, PhD La Fe University Hospital, University of
Valencia, Human Reproduction Unit, Department of Obstetrics and
Gynecology, Reproductive Medicine Research Group, Instituto de
Investigación Sanitario La Fe, Valencia, Spain
Bijan Morshedi, BSc University of Virginia School of Medicine,
Charlottesville, VA, USA
UrsulaResMuravec, MD, Msc Medical Center Dravlje, Department for
Infertility, Ljubljana, Slovenia
Maximilian Murtinger, MD NEXTCLINIC IVF Zentren Prof. Zech,
Bregenz, Austria
Alena D. Naumova, MD Monmouth Medical Center, Department of
Obstetrics and Gynecology, Long Branch, NJ, USA
Ernest Hung Yu Ng, MBBS, MD Department of Obstetrics and
Gynaecology, The University of Hong Kong, Hong Kong, SAR, China
Kamal Ojha, MD, FRCOG St. George’s University Hospital, NHS
Foundation Trust, Department of Obstetrics and Gynaecology, London, UK
Angela Palumbo, MD, PhD Centro de Asistencia a la Reproducción
Humana de Canarias, San Cristobal de La Laguna, Spain
CallumAndrewPotts, BSc, MBBS Inova Fairfax Hospital, Women’s and
Children’s Hospital, Falls Church, VA, USA
Nikolaos Prapas, MD, MSc, PhD Third Department of Obstetrics and
Gynecology, Hippokratio General Hospital of Thessaloniki, Thessaloniki,
Greece
Aristotle University of Thessaloniki, Thessaloniki, Greece
BethW.Rackow, MD Columbia University Medical Center, Department of
Obstetrics and Gynecology, New York, NY, USA
Alberto Revelli, MD PhD Sant’Anna Hospital, University of Turin,
Department of Obstetrics and Gynecology, Turin, Italy

xx
Adela Rodriguez-Fuentes, MD Universidad de La Laguna, Centro de
Asistencia a la Reproducción Humana de Canarias, San Cristobal de La
Laguna, Spain
JeanPaulRouleau, MD Centro de Asistencia a la Reproducción Humana
de Canarias, San Cristobal de La Laguna, Spain
MariaRuiz-Alonso, MSc Igenomix, Valencia, Spain
KhaledSakhel, MD Inova Fairfax Hospital, Department of Obstetrics and
Gynecology, Falls Church, VA, USA
MaximilianSchuff, PhD NEXTCLINIC IVF Zentren Prof. Zech, Bregenz,
Austria
DonnaR.Session, MD Vanderbilt University Medical Center, Department
of Obstetrics and Gynecology, Franklin, TN, USA
CarlosSimón, MD, PhD Valencia University, Valencia, Spain
Igenomix Academy and Igenomix, Valencia, Spain
Department of Obstetrics and Gynecology, Stanford University, Stanford,
CA, USA
Department of Obstetrics and Gynecology, Baylor College of Medicine,
Houston, TX, USA
Contributors
LauraP.Smith, MD Reproductive Medicine and Surgery Center of Virginia,
PLC, Charlottesville, VA, USA
Laurel A. Stadtmauer, MD, PhD The Jones Institute for Reproductive
Medicine, Eastern Virginia Medical School, Norfolk, VA, USA
Carlos E. Sueldo, MD University of California San Francisco-Fresno,
Department of Obstetrics and Gynecology, Fresno, CA, USA
Mette Toftager, MD, PhD Fertility Clinic, Rigshospitalet, Copenhagen
University Hospital, Copenhagen, Denmark
Mai Tran, MD, MPH Fresno Department of Obstetrics and Gynecology,
University of California, San Francisco, Fresno, CA, USA
Landon W.Trost, MD Mayo Clinic, Department of Urology, Rochester,
MN, USA
IlanTur-Kaspa,
MD, FACOG Institute for Human Reproduction, Chicago,
IL, USA
TomerTur-Kaspa Wesleyan University, Middletown, CT, USA
Dimuthu Vinayagam, BSc, MD, MRCOG St. George’s University
Hospital, University of London, Cardiovascular Sciences Research Centre,
London, UK

Part I
Safety in Ultrasound

Ultrasound inReproductive
Medicine: Is It Safe?
JacquesS.Abramowicz
1
Introduction
The rst published description of the clinical use
of ultrasound in obstetrics and gynecology
(OB-GYN) dates from 1958 [1] and describes the
value of this new technology for the diagnosis of
abdominal masses, specically ovarian cysts.
Since then its use has increased exponentially
and is ubiquitous in the daily practice of
OB-GYN. Another OB-GYN specialty that has
equally burgeoned is reproductive endocrinology
and infertility (REI). These two disciplines are
strongly interconnected, in part because of the
major progress made in image quality and the
introduction of new modalities, such as color and
spectral Doppler or three-dimensional (3D) ultrasound, which has greatly facilitated diagnosis,
interventions, and certain forms of therapy in fertility treatments and assisted reproductive technology. Because ultrasound is a waveform, with
alternating positive and negative pressure, it has
effects in tissues it traverses. These may be thermal and nonthermal (or mechanical). The question that bears asking is: can these effects be
detrimental to the developing follicle, ovum, or
early fetus? A publication describing premature
J. S. Abramowicz (*)
Ultrasound Services, Fetal and Neonatal Care Center,
University of Chicago, Department of Obstetrics and
Gynecology, Chicago, IL, USA
e-mail: jabramowicz@bsd.uchicago.edu
ovulation in women whose ovaries were exposed
to ultrasound is often quoted but dates from 1982
[2]. This chapter will briey describe the physics
of ultrasound and its interaction with live tissue,
dene bioeffects and on-screen indicators of
potential risk, focus on ovarian scanning in ART,
and discuss fetus susceptibility and safety measures. Bioeffects and safety of ultrasound in pregnancy, in general, and in later gestation, in
particular, will not be addressed. The interested
reader may consult various book chapters and
reviews on this topic [3–11].
A Short Review ofUltrasound
Physics
Ultrasound is a waveform, characterized by various parameters:
• Frequency is the number of cycles per second,
measured in hertz (Hz). Human ears can discern sounds at approximately 20Hz to 20,000
HZ. Diagnostic ultrasound is, generally,
2–15million Hz (2–15megahertz, MHz).
• Wavelength is the distance between two cor-
responding points on a particular wave. It is
inversely proportional to the frequency
(0.2–1.5mm).
• Resolution (i.e., the shortest distance between
two points which allows these two points to be
displayed separately) depends on the wave-
© Springer Nature Switzerland AG 2019
L. A. Stadtmauer, I. Tur-Kaspa (eds.), Ultrasound Imaging in Reproductive Medicine,
https://doi.org/10.1007/978-3-030-16699-1_1
3

4
J. S. Abramowicz
length: the axial resolution ranges between 2
and 4 wavelengths. Therefore, the smaller the
wavelength (which corresponds to the higher
the frequency), the better the resolution (the
distance between the two points is smaller)
but the lower the penetration. This explains
why endovaginal probes have better resolution (higher frequency) but lower penetration,
hence the need to be closer to the organs being
examined.
• Diagnostic ultrasound is not continuous but
pulsed. There are pulses separated by silent
intervals. The number of pulses occurring in
1 second is the pulse repetition frequency
(PRF). The fraction of time that the pulsed
ultrasound is on (duty factor) is very important from a potential bioeffect aspect. When
the PRF increases, so does the duty factor.
Since the ultrasound wave is sinusoidal, there
are alternating periods of positive and negative pressure which allow the wave to propagate through tissues by means of particle
motions. The speed of propagation is related
both to the beam and several of the tissue
properties. The average speed of sound propagation in biological tissues is estimated at
1540m/sec.
• When pressure is exerted on the resisting
insonated tissue, work is produced. The ability
of the wave to do this is its energy (in joules),
and the rate at which the energy is transformed
from one form to another is the power (in
watts, W, or milliwatts, mW).
• When the power is expressed as a function of
area unit (in cm
2
), this is intensity (generally
in mW/cm2). Bioeffects are conventionally
related to the acoustic intensity. As stated
above, pulses of energy are intermingled with
periods where no energy is emitted. When
describing an ultrasound wave, several parameters can be described in relation to time or
space. By combining peak and average values
in time and space, six intensities can be
dened. The spatial peak-temporal average
intensity (ISPTA) is the most practical and
most commonly referred to and corresponds
to the energy averaged over a period of time.
The maximal permitted values based on vari-
Table 1.1 Values of I
denition
Ophthalmic 17 17 17
Fetal imaging 46 94 (104%) 720 (667%)
Cardiac 430 430 720 (67%)
Peripheral vessel 720 720 720
by modality and year of
SPTA
1976 1986 1992
ous clinical applications being considered
were rst determined in 1976 by the US Food
and Drug Administration (FDA) [12] but were
modied in 1986 [13]. The most recent denition dates from 1992 [14]. These values (in
2
mW/cm
) are shown in Table1.1 for the various applications (left column) as a function of
the year they were implemented (modied
from references [10–13]). The numbers in
parentheses indicate the percentage increase,
compared to the previously allowed intensity.
It is interesting to observe from the table that,
for fetal imaging, the ISPTA was allowed to
increase by a factor of almost 16 from 1976 to the
most recent values in 1992, yet, as will be
described below, all known epidemiological
information available regarding fetal effects predates 1992. A further remarkable fact is that intensity for ophthalmic examination has not changed
from the original 17 mW/cm2, a value approximately 42.5 times lower than the present allowed
maximal value for fetal scanning. Furthermore,
pelvic imaging (abdominal or transvaginal) is not
specied in the above table, but one can assume
that the ISPTA is the same as adult abdominal
imaging, i.e., 720mW/cm
2
, also quite higher than
that allowed for scanning of the eye.
Tissue Characteristics
When the ultrasound wave travels through a
medium, its intensity diminishes with distance
[15]. Biologic tissues are nonhomogeneous, and
weakening (attenuation) of the signal results
from absorption and scattering, as well as reec-
tion. Absorption is the sound energy being converted to other forms of energy, and scattering is
the sound being reected in directions other than
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