4. Ultrasound

What is a Level I ultrasound scan and when is it performed?

A standard 2nd trimester scan at 12-14 weeks involving a simple foetal anatomical survey and determination of gestational age

What are the risks of a Level I scan?

No major risks unless a transvaginal probe needs to be used

What is a Level II ultrasound scan and when is it performed?

A specialised 2nd trimester scan at 18-22 weeks

What are the purposes of a Level II scan?

Assess foetal anatomy, screen for abnormalities, evaluate placental location, assess maternal pelvic anatomy, and further estimate gestational age

Is a Level II scan used to determine sex?

No

What is the Doppler effect in ultrasound?

A change in wavelength due to motion of the source

What does a duplex scan do?

Images the movement of tissues and body fluids and their relative velocity to the probe, determining speed and direction of flow by calculating frequency shift

What can spectral duplex scanning assess?

Direction, pulsatility, and acceleration of flow — and produces audible sounds

What is Doppler echocardiography used for?

To examine the heart — assessing speed and direction of blood flow, cardiac valve function, abnormal communication, cardiac output, and left ventricle function

What is the main limitation of Doppler echocardiography?

The ultrasound beam should be as parallel to blood flow as possible

What is an advantage of Doppler echocardiography for children?

There is no age or size requirement

What does foetal Doppler ultrasound assess?

Blood circulation in the foetus, uterus, and placenta — including heart rate and heartbeat

When is the risk of morphological abnormalities highest in foetal Doppler?

In the last 3 months of pregnancy

What morphological abnormalities can foetal Doppler detect in the last trimester?

Abnormalities in blood vessels, heart, and brain

What are the indications for a 32-week Doppler scan?

Multiple pregnancies, foetus affected by Rhesus antibodies or Parvovirus, history of low birth weight or late miscarriage, slow foetal growth, gestational diabetes, low or high BMI, smoker

What are the advantages of ultrasound?

No radiation, widely available, relatively cheap, easy to use, excellent safety profile, no contraindication in pregnancy/lactation, minimal patient preparation, real-time and dynamic imaging, no contrast agents needed

What patient preparation may be needed for transabdominal ultrasound?

A full bladder to enhance resolution

What are the disadvantages of ultrasound?

Risk of tissue heating and gas formation with prolonged/untrained use, transvaginal risk if cervix is breached, very focused imaging area, needs specialist interpretation, penetration limited by fat/muscle, probe must be placed at 90 degrees

What long-term effects does ultrasound have on tissue?

Long-term effects are unknown; it can slightly heat tissue and create small pockets of gas

What are the uses of ultrasound?

Abdominal ultrasound, bone sonometry, breast ultrasound, Doppler foetal heart rate monitors, Doppler ultrasound, echocardiogram, foetal ultrasound, ultrasound-guided biopsies, ophthalmic ultrasound, ultrasound-guided needle placement

What are the 4 key review topics for ultrasound probes and physics?

4 types of probes, piezoelectric effect, frequency, and interaction with tissue (attenuation, reflection, refraction)

What are the imaging modes in ultrasound?

Brightness mode (B-mode), Motion mode (M-mode), and Doppler

What does hyperechoic mean?

Tissue that reflects more ultrasound waves, appearing brighter on the image

What does hypoechoic mean?

Tissue that reflects fewer ultrasound waves, appearing darker on the image

What is echogenicity?

The ability of tissue to reflect ultrasound waves

What is foetal sonography?

The most widely used imaging modality to view foetal development and monitor health of the foetus and mother

What maternal conditions have increased incidents of stillbirth and foetal abnormalities?

Morbid obesity, hypertension, and gestational diabetes

What are the two approaches for foetal sonography and their bladder requirements?

Transvaginal (empty bladder) and transabdominal (full bladder to enhance resolution)