1. Diagnostic Ultrasound for Postgraduates in Obstetrics and Gynaecology
Max Brinsmead MB BS PhD
May 2015

2. Potential uses for ultrasound in the 1st trimester of pregnancy:
Locate the pregnancy – exclude ectopic
Assessment of viability
Diagnosis of molar pregnancy
Determining gestational age
Diagnosis of multiple pregnancy
Assessment of other pelvic masses
Screening for fetal abnormalities
Assisting CVS and amniocentesis

3. Other uses for ultrasound in obstetrics:
Screening for placenta previa
Assessment of APH
Cervical length monitoring
Assessment of fetal growth
Evaluation of polyhydramnios and hydrops
Diagnosis and management of malpresentation
Assessment of fetal welfare
Assessment of the postpartum uterus
Directing intrauterine interventions

4. Potential uses for ultrasound in gynaecology:
Assessment of adnexal pelvic masses
IUCD and Implanon location
Treatment of ovarian cysts (aspiration) and ectopic pregnancy (methotrexate)
Investigation of postmenopausal bleeding
Evaluation of pelvic pain
Investigation of menorrhagia
Diagnosis of polycystic ovaries
Tubal patency studies in infertility
Evaluation of primary amenorrhoea
Screening for ovarian cancer
Monitoring of follicle number and growth for IVF
Egg recovery for IVF and ICSI

5. But before you can do all this…
You must know how to drive an ultrasound machine

6. What is Medical Ultrasound?
Sound waves whose frequency is beyond the human ear
That is >20 kHz

7. Advantages of Ultrasound:
Can be directed in a beam
Obeys the laws of reflection and refraction
Reflected by objects of quite small size
Can be converted to analogue or digital signals for image production

8. An ultrasound image is produced by:
Producing a beam of sound waves
Transmitting this through the object of interest
Receiving echoes
Converting the echoes into electric signals
Interpreting and displaying those signals
Can be snapshot or in real time

9. The ultrasound beam AND the receipt of echoes is achieved by piezoelectric crystals:
Mounted in an array on a probe
The probe can be fixed or oscillating
The wave of sound can be focused to a point of interest
The image is displayed on an oscilloscope (or TV screen)

10. The image is formed by: The direction of the echo
The strength of the echo
The time taken for the echo to return
These 3 characteristics determine which pixels on the screen will light up
And with what intensity

11. So the ultrasound image will be:
White = Area of high acoustic impedance e.g. bone
Black = Areas of low acoustic impedance e.g fluid
All shades of grey in between
Shadowed by area of non penetration or areas behind those of high acoustic impedance e.g. behind bone

12. Disadvantages of Ultrasound:
Travels poorly through gas
The amount reflected depends on the degree of acoustic mismatch
The piezoelectric crystals are quite delicate

13. Diagnostic ultrasound:
Typically involves frequencies of 2 – 15 mHz
Lower frequencies will give greater penetration
And thereby you can see further
Higher frequencies allow you to see more detail
But the penetration is less
And very high frequencies have the potential for adverse biological effects

14. Types of Probes: A linear array of crystals A sector scanning probe
Produces parallel sound waves
And a rectangular image
Good for surface structures
A sector scanning probe
Produces a fan-like image
Can fit ito narrow spaces
Has poor near-field resolution
A curved array of crystals
Will fit curved surfaces of the body
The density of scan decreases proportionally to the distance from the transducer

15. Probe Types

16. Machine Controls

17. Max’s Maxim Number 17
Using an ultrasound machine without using a few of its knobs is like driving a car only in the first gear
It’s a safe to go…
But you don’t get very far

18. Some tips: Don’t be intimidated by all the knobs
Just like driving a car, You only need to know a few basic controls
Practice and play!
The first challenge is to find the switch to turn it on
There may be more than one
Next find the machine pre set for the exam you are about to do
And do all this before you get to the patient

19. Some more tips: Ultrasound is no substitute for a good history
ALWAYS do an abdominal scan before using the vaginal probe
Know how to switch probes
Is it safe to “hot wire”?
The trick is to build up a 3-dimensional picture in your mind using real-time imaging
You will always be better than sonographers because you know the anatomy and pathology
Or you will get to see it!
So beware of premature conclusions

20. Machine Controls: Freeze Zoom Depth Gain
Controls brightness or “contrast”
Also in a array of sliding levers
Use maximum gain and minimum power
Depth
Reach to the area of interest then…
Zoom
To enlarge your view then…
Freeze
For measurements (or stored image)

21. Machine Controls

22. Machine Controls 2: Tracker Ball Calipers Ellipse
This is the “mouse” for your computer, usually with right and left click buttons to execute functions
Used to superimpose things on the screen
May have several functions
Calipers
To measure distance between 2 points
Ellipse
To measure area

23. Machine Controls

24. Some more tips:
Use a low light but make sure you can see all the controls
Adjust contrast on your screen before you start
Make yourself and the patient comfortable
Use a good quality transducer gel - SPARINGLY
Remember the prime purpose of the exam
Make sure that always follow a routine and do it all
Scroll-back and cine re-loop can be very useful
Look for acoustic enhancement on the other side of fluid
Look for shadowing on the other side of bone

25. Some traps:
Doing patients in succession when data from one is carried forward onto the next
When you find a fetal heart make sure that it inside a uterus
Pseudo sac within the uterus with an ectopic
Measuring the yolk sac as a part of the CRL
Image duplication resulting in the false diagnosis of twin sacs
A small amount of free fluid in the pelvis can be normal
Know the many variations of a corpus luteum
Using a too-narrow field of view

26. Proven uses for ultrasound in pregnancy:
Dating the gestation
Many women cannot provide a reliable LMP
Should be +/- 7 days based on CRL in the 1st trimester
Can be +/- 10 days based on HC, AC and FL in 2nd trimester
Becomes increasingly unreliable after 22w
Identification of multiple pregnancy
Twins have a perinatal mortality that is 2-4x singletons
Monitoring for discordant growth with Doppler reduces risk
Important to diagnose zygosity
Identification of breech in the third trimester
ECV reduces the rate of Caesarean section
Few RCTs of routine ultrasound have shown any effect on overall perinatal mortality and morbidity

27. Unproven uses for ultrasound in pregnancy:
Screening for Aneuploidy
Cost effectiveness of universal screening debated
Ethical issues and patient choice involved
Screening for structural malformations
Sensitivity is 13 – 50% depending on expertise & equipment
And only half of these before 20 w gestation
False positives occur
Screening for IUGR in the 3rd trimester
Sensitivity is 80-90%
But the positive predictive value of neonatal morbidity is only 25-50%
The rest have constitutional smallness

28. Harmful Effects of ultrasound in pregnancy:
It is not ionising radiation
However, thermal effects and cavitation can occur in tissues exposed to high power ultrasound
One RCT of repeated routine ultrasound with Dopplers in the 3rd trimester found a small but significant decrease in birth weight in the exposed cohort
A meta analysis showed males exposed to ultrasound in uterus are more likely to be left-handed

29. Caring for your ultrasound machine:
Treat your probes as if they were made of glass
Wash, clean and dry probes
Sterilisation options
Don’t use oil or alcohol
Transport probes safely stowed
If you changed the machine defaults set them back to the original

30. Ultrasound in the first trimester of pregnancy:
Start with the abdominal probe
Counsel the patient about your expected findings and expertise
First find the cervix and/or uterine body
It’s not as far in as you think
Look for embryo at the edges of a sac <7w
FH should be demonstrable when sac size is >2 cm
Measure CRL up to 12w, thereafter BPD, HC, AC and FL
Remember ectopic and multiple pregnancy
If you are not sure say so…
Exclude ectopic and recheck in 7 – 14 days
Check the POD and ovaries before you finish

31. Pain & Bleeding in Pregnancy
Assume ectopic & proceed accordingly
>1000 iu/L
Diagnostic laparoscopy if clinically suspicious
iu/L
Observe
Repeat HCG in hrs
Rescan when >1000 iu/L
or follow to <10 iu/L if EP possible
<500 iu/L
Quantified beta HCG
Inconclusive Vaginal Scan = Empty uterus
Pain & Bleeding in Pregnancy
Emergency Management

32. Ultrasound in the third trimester of pregnancy:
Start with abdominal palpation
Tell patient purpose of examination
Quick scan for presentation and lie
Measure BPD, HC, AC and FL
Remember that this does not predict dates
Liquor volume
Find placenta and examine lower edge in relationship to the presenting part
Suspected placenta previa best evaluated by PV or TV scan
Ovaries virtually never seen

33. Ultrasound for the non pregnant woman:
Start with abdominal probe
Preferably with a full bladder
I measure uterine dimensions in two planes
Then send patient to empty bladder…
And switch to vaginal probe
First find the cervix
Acutely anteverted/flexed uterus is tricky
Find and measure endometrium
Then evaluate myometrium
Ovaries can be anywhere
And cannot be found 25 – 30% of the time
I measure ovaries in two dimensions

34. Any Questions or Comments?
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