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Fetal Evaluation (UPenn) > Basic Ultrasound > Flashcards

Basic Ultrasound Flashcards

1
Q

Levels of ultrasound procedures

A
  • Standard/Basic
  • Limited
  • Specialized (when fetal anomaly suspected)
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2
Q

AWHONN Scope of Practice

1st trimester ultrasound

A
  • +/- gestational sac
  • Fetal #
  • +/- cardiac activity
  • Estimated GA via CRL
  • +/- IUP
  • Identify 1st tri complications:
    • Anembryonic pregnancy
    • Ectopic pregnancy
    • Threatened, incomplete, complete, or misses AB
    • Molar pregnancy
    • Multiple gestation
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3
Q

AWHONN Scope of Practice

2nd+3rd trimester ultrasounds

A
  • fetal #
  • +/- cardiac activity
  • Fetal presentation
  • Placental location
  • Amniotic fluid volume
  • BPP and modified BPP
  • Biometric measurements: EFA and EFW
  • Cervical length measurements
  • Adjunct to US guided procedures
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4
Q

Common ultrasound indications

A
  • Evaluation of fetal growth
  • Suspected fetal abnormality
  • Adjunct to special procedures (le amnio)
  • Uterine evaluation
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5
Q

Which 2 probes do we use the most in OB/GYN

A
  • 3.5 MHz convex probe (abdomen, OB/GYN)
  • 6.5 MHz transvaginal probe
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6
Q

Where do you orient the transducer notch?

A
  • Notch oriented towards person’s head
  • Left side of ultrasound screen = head
  • Right side = feet
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7
Q

What are the different ultrasound modes?

A
  • B-mode: “Brightness mode”
    • 2D ultrasound in grey scale using real time.
    • Used 99% of time
  • M-mode: “Motion mode”
    • Cursor line on fetal heart and shows motion of fetal heart, estimates FHR
  • Doppler
    • Color - shows direction of flow
      • Towards transducer = red
      • Away from transducer = blue
    • Power - amplitude
    • Spectral - velocity
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8
Q

Define: echogenic

A

The ability of a structure to produce echos

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9
Q

Define: anechoic

A
  • No echos
  • Appears black on ultrasound
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10
Q

Define: hypoechoic

A
  • Less reflective and low amount of echoes when compared with neighboring structures
  • Appears as varying shades of darker gray
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11
Q

Define: hyperechoic

A
  • Highly reflective & echo rich when compared with neighboring structures
  • Appears as varying shades of gray
  • Echogenic is often used interchangeably
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12
Q

Define: isoechoic

A
  • Having similar echogenicity to a neighboring structure
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13
Q

Define: homogenous (texture)

A
  • Organ parenchyma is uniform in echogenicity
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14
Q

Define: inhomogenous/heterogenous (texture)

A
  • Organ parenchyma is not uniform in echogenicity
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15
Q

Define: reverberation

A
  • Artifacts that appear as multiple equally spaced lines along a ray line.
  • Caused by the sound bouncing back and forth between tissue boundaries and then returning to the receiver
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16
Q

Define: acoustic enhancement

A
  • Artifact with hyperechoic pattern to a poorly or non-attenuating structure or mass
  • Often seen with fluid index
17
Q

Define: shadowing

A
  • Artifact appears as a hypoechoic pattern to highly attenuating structures (e.g., calcifications such as bone)
18
Q

What is the ALARA principle?

A
  • As Low As Reasonably Achievable
  • Only perform when there is a valid medical indication, and use the lowest possible ultrasonic exposure setting to gain the necessary diagnostic info
19
Q

Define: thermal index (TI)

A
  • Measure of how much the ultrasound beam is theoretically heating the tissue. Its different for the types of tissue
  • TIs (soft tissue): GYN and OB < 10 weeks
  • TIb (bone): OB ultrasound > 10 weeks
  • TI = <0.7 is the threshold for extended scanning
20
Q

1st trimester gestational sac facts

  • Visibility by tranvaginal and abdominal approaches
  • Gestational sac characteristics (appearance, sizing, cardiac activity)
  • What confirms IUP
A
  • Visible as early as 4 - 4.5 transvaginal and 5 - 5.5 weeks abbdominal
  • Thick, bright, double ring
  • Sac > 2mm, fetal embryonic pole visible by transvaginal
  • Embryon > 5 mm, cardiac + likely
  • CRL > 7 mm, cardiac + definitely
  • Yolk sac confirms IUP
    *
21
Q

Pregnancy Failure

A
  • Gestational sac measuring >25 mm without an embryo within is diagnostic of a failed pregnancy
22
Q

What biometry measures are used after 14 weeks?

A
  • Biparietal diameter (BPD)
  • Abdominal circumference (AC)
  • Head circumference (HC)
23
Q

Biparietal Diameter and Head Circumference Landmarks/Measurement

A

Landmarks

  • Falx Cerebri Anteriorly and Posteriorly
  • Thalami
  • Cavum septum pellucidum

Measurement

  • BPD
    • Width of skull transversly through thalami
    • Outer edge of parietal skull to inner edge
  • HC
    • Outer circumference edge of fetal skull (use ellipsis instead of calipers)
24
Q

Abdominal Circumference

Landmarks/Measurement

A

Landmarks

  • Junction of umbilical vein and left portal deep vein within liver
  • Stomach
  • Three ossification centers of spine

Measure

  • OUTER transverse circumference
25
Q

Femur Length

Landmarks/Measurement

A

Landmarks

  • Longitudinal view

Measure

  • Diaphysis to diaphysis
  • Omit “HOOK”or femoral epiphysis
  • 90° angle
26
Q

Placenta Position

Low-Lying vs Previa

A
  • Complete
    • Over/up to IO
  • Low Lying
    • ≤ 2.0 cm IO
  • Rescan at 32 wks; +36 wks
27
Q

Placental grades

A
28
Q

Indications for fetal surveillance

A

Any maternal or fetal condition that would affect utero-placental functioning

Maternal

  • Hypertension
  • Diabetes
  • Preterm Labor
  • Sickle Cell Disease, Thalassemias
  • Elevated Maternal Serum Alpha Feto protein

Fetal

  • IUGR
  • Abnormal fetal ultrasound
  • Multiple gestations
  • Decreased fetal activity
  • Isoimmunizations
  • Previous stillborn
  • Post-dates
29
Q

Types of fetal surveillance

A
  • Fetal movement counts
  • Non-stress tests
  • Biophysical profile scoring
  • Contraction stress tests
30
Q

Non-stress test

A
  • Monitors fetal heart rate and uterine activity
  • Note for the presence or absence of 2 accelerations in 20 minutes (or up to 40 minutes or longer)
    • Reactive (Reassuring): 2 or more accelerations
      • 15 beats by 15 seconds (over 32 weeks gestation)
      • 10 beats by 10 beats (under 31 and 6/7 weeks gestation)
      • Detects 99% well-oxygenated and non-acidemic fetuses
    • Non Reactive (Non-reassuring): 0 – 1 acceleration only
      • Repeat testing within 24 hours
      • BPP or CST
      • 50% of fetuses with non-reassuring FHR are OK
  • Vibroacoustic stimulation: 1 – 2 seconds using specially designed artificial larynx placed on maternal abdomen
    • May repeat 3x at max 2 seconds to elicit fetal heart rate accelerations
31
Q

Biophysical Profile

A
  • Assess fetal intrauterine adaptation
  • Ultrasound evaluation for 30 minutes
  • 5 Assessment Parameters (2 points each, all or none)
    • NST (reactive)
    • Fluid (2 cm pocket)
    • Breathing (30 seconds)
    • Tone (1 episode)
    • Movement (3 gross body movements)
  • Reassuring = 8 or 10 → no further testing
  • Nonreassuring = < 6 → further testing or delivery
    • Equivocal → retest in 12 - 24 hours
      • 6
    • Abnormal - consider delivery
      • 4 - high probability of asphixia
      • 2 - asphixia almost certain
      • 0 asphixia certain
32
Q

Modified BPP

A

Modified BPP = NST and AFI

  • NST - short term indicator of fetal hypoxic status
  • AFI - indication of long-term placental function
33
Q

Amniotic fluid volume measurements

(3 techniques)

A
  1. Subjective - sonographer compares the overall amount of fluid [free of cord and body parts] to the area that the baby and placenta are occupying
  2. Single deepest vertical pocket - measure the single deepest vertical fluid pocket of fluid [free of cord and body parts]
  3. Amniotic fluid index (AFI):
  • Must hold transducer perpendicular to the floor
  • Divide uterus into 4 quadrants with 2 perpendicular lines
  • Measure largest vertical fluid pocket [free of cord and body parts] in centimeters
  • AFI is the sum = total of the four quadrants
34
Q

Amniotic fluid volume levels

(normal vs abnormal)

A

Oligohydramnios

  • AFI < 5 cm
  • < 2 cm single deepest vertical pocket of fluid

Normal

  • AFI > 5 – 23 cm
  • A normal single-pocket measurement is between 2 – 7 cm

Polyhydramnios

  • AFI > 24 cm
  • > 8 cm single deepest vertical pocket of fluid
35
Q

Contraction Stress Test (CST)

A
  • aka Oxytocin challenge test
  • Contraindications
    • PTL
    • High risk for preterm delivery
    • PPROM
    • Placenta previa
    • Classical uterine scar
  • Observe baseline FHR and uterine activity for 10-20 min
  • If < 3 contractions lasting at least 40 sec in 10 min → nipple stim or oxytocin to produce 3 contractions in 10 min
  • Negative test = no late or significant variable decels
  • Positive = late decels in at least 50% of contractions (consider further testing or delivery)
36
Q

False negative vs False positive tests

A

False Negative Test - normal result with resultant fetal death within 1 week of testing

  • Very low rates
  • NST= 1.9/1000 women
    CST= 0.3/1000 women
    BPP & modified BPP = 0.8/1000 women

False Positive Test - abnormal test result that prompts delivery for an uncomprised fetus

Fetal Evaluation (UPenn) (5 decks)

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