Ultrasonagraphy Flashcards
What are ultrasounds?
Sound waves with frequencies higher than the human audible range,
The upper limit is considered to be approximately 20kHz
What are the functions of the ultrasound probe?
The ultrasound probe has 2 main functions
- Emit a sound wave
- Receive echoes from the original wave
What is the pulse echo principle?
This is the foundation principle of all Ultrasound applications and technology
Whenever the ultrasound wave passes through a tissue boundary it can be reflected or will pass through and continue propogating
Describe how tissue density affects the amount of sound wave reflected
Adjacent tissues with varying densities will reflect more of the sound wave, adjacent tissues with similar densities will reflect less..
Eg Air in lungs creates a poor image
What does an ultrasound image look like?
Gray scale is traditional for ultrasound
Dense bone reflects back at higher altitudes than less dense tissues ∴ denser areas shown in white
How is fluid shown in ultrasound images?
Fluid (e.g. urine, bile, cysts, amniotic fluid) doesn’t contain v. dense materials for ultrasound to reflect back off so produces a dark black image
What are the clinical applications of ultrasound?
Obstetrics Gynaecology Abdominal Urinary Trauma - POCUS Testicular Breast Head / neck Vascular Cardiology Musculoskeletal (MSK) Lungs
Outline the pros of using ultrasound
🗸 No radiation 🗸 No documented side effects in humans 🗸 Usually non invasive 🗸 Well tolerated 🗸 “real time” imaging 🗸 Results can often be available immediately – Bedside 🗸 Widely Accessible
What are the cons of ultrasound use?
⨯ Ultrasound image quality is highly dependant on patient habitus
⨯ No known side effects?
⨯ Training is more resource intensive for departments compared to other modalities
⨯ Effectiveness and accuracy are highly operator dependant
Why is there a variety of transducers available?
Important to have a selection as an increased choice of technical variables allows for optimisation of your image
Choice over sector width, scan depth (resolution), patient habitus, field of view..
What is the major advantage of Ultrasound over X-ray / CT in obstetric imaging?
All women in the UK are offered ultrasound Screening during pregnancy (12/20 weeks)
Scan Preparation?
If there is a problem, what happens?
How big is a fetus typically at 12 wk scan?
Fetus is approximately 45-84mm in length (11+2wks – 14wks)
What is the purpose of the 12 week scan?
First routine scan offered to most low risk pregnancies
Detects ‘Viability’, number of fetus’,
What can we identify at the 12 week scan?
Gross anatomy, detectable major abnormalities, morphology of ovaries and an accurate gestational age of the fetus
What are common abnormalities detected at 12 weeks?
- Body Stalk Defect 1:14-30,000
- Blighted Ovum / Missed
- Cystic Hygroma
10% survival rate - Molar Pregnancy 1:1000
What are the chances of miscarriage throughout a pregnancy?
1 / 4 pregnancies from the start will result in miscarriage
After 12 weeks of pregnancy the chances of miscarriage decrease
What causes downs syndrome (DS)?
Down’s syndrome is caused by a change in one of the genes in the egg before fertilisation (at the time of conception); Usually completely random, though more common in older mothers
What is the frequency of DS around the world?
Throughout the world, the frequency of DS is ~3 per 2000 births.
Outline incidence rates of DS
1: 1500 at 20 years
1: 800 at 30 years
1: 270 at 35 years
1: 100 at 40 years
1: 50 at 45 years and over
How is DS detected using ultrasound?
Fetal nuchal translucency (NT) screening uses ultrasound to measure size of nuchal pad at nape of fetal neck
It should be performed between 11 weeks and 13 weeks + 6 days
What physical changes can we identify using ultrasound in DS babies?
In DS, NT is much thicker around 3mm
Also have lack of nasal bone (soft marker for DS)
How can a maternal blood test help identify DS?
Maternal blood test can identify different DS markers e.g enzyme gene mutations
Can be tweaked to optimize chances of healthy baby
What is the purpose of the 20 week scan?
The purpose of the 20 week scan in England is to identify abnormalities which:
- may indicate the baby has a life-limiting condition
- may benefit from antenatal treatment
- may require early intervention following delivery
What are other aims of the 20 week scan?
Other standard aims;
- Placenta localisation
- Fetal Biometry
- Fibroid Monitoring
- Liquor Assessment
How can Ob/gyn estimate baby weight?
Measure bone lengths and estimate baby weights
What is spina bifida?
Spina Bifida is an incomplete closing of the spine and membranes around the spinal cord during early development
Spinal nerves can protrude and create cyst
How can spina bifida be treated?
In utero surgery can close spine before birth
More serious cases can lead to paralysis, incontinence and is linked to other chromosomal abnormalities
What are the physical markers of spina bifida?
Cerebellum posterior in brain (seen as figure 8 on scan) links the brain to spinal cord
Spina bifida:
Cerebellum pulled down as spinal cord is protruding out causing misshapen brain - lemon shape
The extra force pulling down the baby’s brain causes indents of forebrain
What are markers of achondroplaisa obsevred in ultrasound?
Frontal bossing - forehead protrudes
Thickened soft tissue surrounding the long bones
Bowing of long bones
What is achondroplasia?
Achondroplasia is a genetic disorder that results in dwarfism
How can we detect a low lying placenta using ultrasound?
In England at the 20 week scan we measure the distance from the lowest edge of the placenta to the internal OS of the cervix
What are the further tests required for complications of a low lying placenta?
If the placenta is within 2.5cm of the cervix then future scans are required
If the placenta does not raise higher closer to the due date then a C-Section may be required
What is talipes?
Club foot (Unilateral/Bilateral) If one parent had the condition as a baby their own baby would have a 1 in 30 chance of also having talipes
What causes club foot?
Mechanical
- foot trapped in position without much fluid - weakening tendons around ankle
Chromosomal
- DS, Patau’s & Edwards
What is Anhydramnios / Oligohydramnios?
Without amniotic fluid / less amniotic fluid surrounding fetus
What is Polyhydramnios?
Excess amniotic fluid surrounding fetus
- may be due to gestational diabetes
When is an Umblical artery doppler assessment carried out?
Can be used to highlight the effects of preeclampsia and intrauterine growth restriction (IUGR)
Used more frequently - suggested we can improve perinatal mortality and morbidity
What are the signs of an early pregnancy?
In cases of
lower abdominal/pelvic pain, bleeding, confirmed history of recurrent miscarriage and sometimes due to previous obstetric history issues
What are normal pregnancy EPU results?
The fetal pole is detected is an area of thickening along yolk sac periphery
Minimum of 1-2mm in length for detection (5-6 wks)
Cardiac Activity should be detected routinely from 4-5mm (6wks)
What is an ectopic preganncy?
When an egg implants outside of the uterine cavity it is known as an ectopic pregnancy
- transvaginal
- transabdominal
What causes an ectopic pregnancy
Can be caused by fallopian tubal damage (from surgery, PIDS, endometriosis) or attached to the pelvis, ovaries or ligaments
What is the consequence of an untreated ectopic?
Will continue to grow and propagate if untreated
Treatment depends on the individual, Medical or surgical
What causes multiple pregancnies?
Multiple pregnancy is usually caused by delays in the fertilized egg reaching the womb before implanting
How is ultrasound used to visualise multiple pregnancies?
Can visualise triplets and conjoined twins
Describe what we’d see in dichorionic twins?
Dichorionic
Lambda Sign – non identical
What is seen in ultrasound of monochorionic twins?
Monochorionic
T Sign - identical
When is 3D/4D imaging used?
3D / 4D doesn’t currently have much diagnostic value other than cleft lip
When is an obstetric ultrasound carried out?
Usually carried out for chromosomal abnormalities
e. g.
- CVS
- Amniocentesis
What is CVS?
CVS (chorionic Villus Sampling) ultrasound guided ; sampling blood vessels and tissues helping baby grow
What is amniocentesis?
Amniocentesis ; sampling amniotic fluid - can test genetics/chromosomes of babies
Has risks ~1-2% miscarriage risk
What are fibroids?
Fibroids consist of fibrous muscular tissue
Many grow until blood supply no longer supports further growth
Others get very large and become mechanical obstructions
How are firboids treated?
Require surgical interventions ( myomectomy / uterine embolisation / hysterectomy)
What are uterine polyps?
Uterine Polyps – growths from the inner wall of the womb which extend throughout the cavity and into the cervix and vagina.
What is the significance of uterine polyps?
Usually benign but on rare occasions some can turn cancerous. Surgery would be considered
- Rules out ovarian and endometrial cancer
What structures can be observed using an abdominal ultrasound?
Can identify abdominal organs: Liver Kidneys Aorta Pancreas Spleen Gallbladder / Biliary Tree
How can ultrasound be used to identify aortic aneurysms?
Abdominal aorta section defined as aneurysmal when 3cm in AP diameter
What is the treatment prognosis of an aortic aneurysm?
AAAs are monitored in specialised clinics and surgery is often considered once the aneurysm meets 5.5cm in AP diameter
What is the significance of stents?
Ultrasound shows stents put in ; now have 2 limbs supporting directing blood through centre of aorta
Can sometimes get an endoleak →
What may be the reason for an abnormal liver ultrasound?
Abnormal liver may be due to:
- Alcoholism
- Fibrosis and scarring tissue
- Shrinkage
- Excessive fluid
What factors contribute to liver failure?
Can be caused due to lifestyle, genetic predispositions or medications
What causes gallstones?
Usually caused by an imbalance in the chemical make up within the bile in the gallbladder (high cholesterol / bilirubin)
Describe how gallstones appear on ultrasound
Gallbladder may fill with bile -black space on scan
Soft tissue masses (polyps) less dense and darker
kidney/gallbladder stones produce ‘shadows’ in scan - high density bright white
What conditions of the urnary tract are visualised on ultrasound?
> Enlarged Prostate
Polycystic Kidney Disease
Renal Calculi
ectopic kidneys
What may be the reason for testicular lumps on ultrasound?
Varicocele
Simple Cyst - epididymal head
Hydrocele
Testicular cancer
Why are younger patients more liekly to have a breast ultrasound than a mammogram?
Age >35, breast tissue = denser → difficulty diagnosing nature of breast lumps on mammograms differentiating solid / fluid filled areas is relatively poor
Why is ultrasound a better technique for diagnosing breast cancer?
Differentiates at improved rate (~30% increased)
Enables core biopsies of breast lumps = allows histological investigation to allow for classification of the lump.
How is ultrasound used for DVT?
Exclude / confirm presence of DVT in cases of pain and swelling in lower limbs
Screening tool for DVT in postoperative patients and those with known pulmonary embolism (find source of clot)
How is colour flow doppler used in DVT?
Using colour flow doppler we can demonstrate that the femoral vein is completely occluded by the lack of colour in this region
Outline ultrasound applications in musculoskeletal cases
-Muscle/tendon tears
-Inflammation
-Nerve Entrapments
-Soft tissue lumps
-Cysts
-Hernias
-Paediatric CHD
-Infant Torticollis (neck twisting)
-Early RA
-Joint effusions
-Injection Guidance (contrast &
Therapeutic)
What is POCUS?
Point of Care Ultrasound – Focused Assessment with Sonography of Trauma
FAST is an ultrasound scan protocol undertaken at the time of presentation of a trauma patient.
What is the benefit of using POCUS in trauma?
Ultrasound can detect as little as 20ml of free fluid, compared to the 200ml required with plain X-Ray
