Ultrasonagraphy Flashcards
(43 cards)
Define Ultrasound (US)
Sound waves with frequencies higher than the human audible range,
Describe limits of frequencies
The upper limit is considered to be approximately 20kHz
< 20Hz = infasound
20Hz < audible < 20kHz
20kHz < ultrasound < 200mHz
Functions of US probe
First emit a sound wave
Then to receive the echoes from the original wave.
= This is the foundation principle of all Ultrasound applications and technology.
Describe pulse escho principle
Whenever the ultrasound wave passes through a tissue boundary it can be reflected or will pass through and continue propogating
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
Describe relation of amplitude to reflections
High amplitude – strong reflections
Low amplitude – Poor reflections / no reflections
List clinical applications of US
Abdominal
Gynaecology
Urinary
Trauma - POCUS
Obstetrics
Testicular
Lungs
Musculo-skeletal
(MSK)
Breast
Head/Neck
Cardiology
Vascular
Advantages of US
Widely Accessible
Results can often be
Available immediately –
Bedside
No radiation
“real time” imaging
No documented side effects
In humans
Well tolerated
Usually non invasive
Disdvantages of US
Training is more resource intensive
For departments compared to other modalities
Ultrasound image quality is highly
Dependant on patient habitus
Effectiveness and accuracy
Are highly operator dependant
No known side effects?
Why have a selection of transducers
Increased choice of technical variables allows for optimisation of your image
Choice over sector width, scan depth (resolution), patient habitus, field of view..
Describe characteristics of 12wk obstetric US scan
-Fetus is approximately 45-84mm in Length (11+2wks – 14wks) -First routine scan offered to most low Risk pregnancies -Detects ‘Viability’, number of fetus’, Gross anatomy, detectable major Abnormalities, morphology of ovaries And an accurate gestational age of The fetus.
Down’s syndrome define
Down’s syndrome is caused by a change in one of the genes in the egg before it is fertilised by the sperm (at the time of conception)
This is usually a completely random happening, though it is more common in older mothers
Throughout the world, the frequency of DS is about 3 per 2000 births.
Fetal nuchal translucency (NT) function
- when should it be performed
Fetal nuchal translucency (NT) screening uses
ultrasound to measure the size of the nuchal pad at
the nape of the fetal neck. It should be performed
between 11 weeks and 13 weeks + 6 days
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
Other standard aims of 20 wk scan in England
Other standard aims;
Placenta localisation
Fetal Biometry
Fibroid Monitoring
Liquor Assessment
Spina bifida = define
Spina bifida is when a baby’s spine and spinal cord don’t develop properly in the womb = a gap in the spine
a type of neural tube defect
Cause not kbut a lack of folic acid before and in the early stages of pregnancy is a significant risk factor.
Spina bifida = risk factor
Lack of folic acid before and in the early stages of pregnancy is a significant risk factor.
Achondroplasia define
Achondroplasia is a genetic disorder that results in dwarfism.
Thickened soft tissue surrounding the long
bones
What do we measure in 20 wk scan
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.
Describe the effect of low lying placenta
f 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.
Talipes - define
= club foot. It is a deformity of the foot and ankle = congenital
Talipes - chance of getting it
If one parent had the Condition as a baby their Own baby would have a 1 in 30 chance of also Having talipes
Umbilical Artery Doppler Assessment – function
Umbilical Artery Doppler Assessment –
Can be used to highlight the affects of pre-eclampsia and intrauterine growth restriction (IUGR)
Is used more frequently now as is being suggested we can improve perinatal mortality and morbidity.
Characterisics of EPU - US
-The fetal pole is detected as an Area of thickening along the periphery Of a yolk sac -Minimum of 1-2mm in length for Detection (5-6 wks) -Cardiac Activity should be detected Routinely from 4-5mm (6wks)
Reasons for PW to be referred to GP
-Pregnant women can be referred by their GPs in cases of lower abdominal/pelvic pain,
Bleeding, confirmed history of recurrent miscarriage and sometimes due to previous
Obstetric history issues.
