Diagnostic ultrasound ( PDFDrive )

1016 PART IV Obstetric and Fetal Sonography
Indications for First-Trimester Ultrasound
Conirmation of the presence of an intrauterine pregnancy
Suspected ectopic pregnancy
Vaginal bleeding
Pelvic pain
Estimation of gestational age
Diagnosis or evaluation of multiple gestations
Conirmation of cardiac activity
Adjunct to chorionic villus sampling, embryo transfer, and
localization, and removal of an intrauterine device
Assessment for certain fetal anomalies, such as
anencephaly, in high-risk patients
Measurement of nuchal translucency when part of a
screening program for fetal aneuploidy
Suspected ectopic pregnancy
Suspected hydatidiform mole
Maternal pelvic masses and/or uterine abnormalities
Modiied from Collaborative Subcommittee. ACR–ACOG–AIUM–SRU
practice parameter for the performance of obstetrical ultrasound.
American College of Radiology; 2014. 5
using a transabdominal and/or transvaginal approach, depending
on the gestational age and the region of interest. he choice of
transducer frequency is a trade-of between beam penetration
and resolution. In general, a 3- to 5-MHz transducer frequency
provides suicient resolution with adequate depth penetration
in all but the extremely obese patient. During early pregnancy,
a 4- to 7-MHz abdominal transducer or a 5- to 10-MHz vaginal
transducer can provide superior resolution while still allowing
adequate penetration. Higher-frequency transducers are most
useful in achieving high-resolution scans of anatomy close to
the probe, and lower-frequency transducers are useful when
increased penetration of the sound beam is necessary and when
a wider ield of view is needed. Use of Doppler ultrasound and
3D imaging depends on the speciic indication. As in all imaging
studies, complete documentation of the images and a formal
written interpretation are essential for quality assurance, accreditation,
and medicolegal issues.
ULTRASOUND GUIDELINES
First Trimester
he current guidelines of the American College of Radiology
(ACR) and American Institute of Ultrasound in Medicine (AIUM)
for the performance of irst-trimester obstetric ultrasound
examination include documentation of the location of the
pregnancy (intrauterine vs. extrauterine), documentation of the
appearance of the maternal uterus and ovaries (Fig. 28.1), and
assessment of gestational age, either by measurement of mean
sac diameter (before visualization of embryonic pole; Fig. 28.2)
or by embryonic/fetal pole crown-rump length 5 (Fig. 28.3).
Another important structure to assess is the yolk sac. An image
of the heart rate is taken using M-mode ultrasound. It is important
to use M-mode rather than spectral Doppler ultrasound on the
embryo to limit power deposition. Late in the irst trimester,
Indications for Second- and Third-Trimester
Ultrasound
Estimation of gestational (menstrual) age
Evaluation of fetal growth
Evaluation of fetal anatomy and fetal well-being
Vaginal bleeding
Abdominal or pelvic pain
Cervical insuficiency
Determination of fetal presentation
Suspected multiple gestation
Adjunct to amniocentesis or other procedure
Evaluation of discrepancy between uterine size (as
measured by fundal height) and clinical dates
Pelvic mass
Suspected hydatidiform mole
Adjunct to cervical cerclage placement
Suspected ectopic pregnancy
Suspected fetal death
Suspected uterine abnormality
Suspected amniotic luid abnormalities
Suspected placental abruption
Adjunct to external cephalic version
Premature rupture of membranes and/or premature labor
Previous abnormal screening exams
Follow-up evaluation of placental location for suspected
placenta previa or accreta
Previous congenital anomaly
Screening for or follow-up of fetal anomalies
Modiied from Collaborative Subcommittee. ACR–ACOG–AIUM–SRU
practice parameter for the performance of obstetrical ultrasound.
American College of Radiology; 2014. 5
dating can be performed with measurement of the biparietal
diameter and head circumference rather than crown-rump length.
Videos 28.1 and 28.2 show normal irst-trimester indings of
an early embryo with cardiac activity (Video 28.1) and normal
indings of rhombencephalon (Video 28.2).
In the irst trimester it is important to not only establish the
location of the pregnancy (intrauterine versus extrauteruine)
but when intrauterine, to carefully determine if it is a potentially
viable pregnancy or if it is a nonviable pregnancy. 6-9 Due to the
General Survey Guidelines for First-Trimester
Ultrasound
Gestational sac
Location of pregnancy: intrauterine vs. extrauterine
Gestational age (as appropriate)
Mean sac diameter
Embryonic pole length or crown rump length
Yolk sac
Cardiac activity on M-mode ultrasound
Embryo/fetal number (amnionicity/chorionicity)
Maternal anatomy: uterus and adnexa
Modiied from Collaborative Subcommittee. ACR–ACOG–AIUM–SRU
practice parameter for the performance of obstetrical ultrasound.
American College of Radiology; 2014. 5