Ultrasound Flashcards
Ultrasound definition
Very high frequency sound above the audible range , is a longitudinal wave that produces compressions and rare fractions of ‘particles’
What happens when strikes boundary
The beam is split int 4: Transmitted beam Refracted beam Scattered beam Reflected beam
What generates the image
The ultrasound machine generates an image based on amplitude and time taken for echo to return
Amplitude= brightness
Time taken= depth/location
The larger the difference in acoustic impedance, the greater the amount (amplitude) of reflections
The important settings are:
Frequency
Gain
Focus
Low Frequency =
E.g. 3.5MHz. Good depth of penetration but poor resolution
High Frequency =
E.g 10MHz Poor depth of penetration but good resolution
How to decide what frequency to use
Use the highest frequency that allows adequate penetration of structures.
What is gain
Is the amplitude applied to the returning echo. Is turned up for deeper tissues= time-gain compensation
Ultrasound and focus
Adjust focal zone to the region of interest
Transducer types
Sector transducer
Phased array transducer
Liner array transducer
Curved array transducer
Sector transducer ad and dis
\+ small contact area \+diverging beam -reduced near field resolution -diverging far field (reduced lateral resolution) - moving parts (warm up before use)
Sector transducer common uses
Echo cardiology , intrathoracic and intra-abdominal organs, regions with small contact areas e.g. brain, eye, joints
Sector transducer
Mechanical crystal movement
Phased array transducers
Sector scanner with electronic steering of crystal emission
Phased array transducer ad and dis
+ small contact area
+diverging beam
+good resolution
- reduced near field resolution
Phased array transducer common uses
Echocardiology, thoracic structures,Abdominal organs, regions with small contact area ( brain, eye and joints)
Linear array transducers
Multiple crystals arranged in a line and sequentially triggered
Liner array transducers ad and dis
\+ good near field resolution \+parallel beams \+no moving parts - large contact area -limited field of view
Linear array transducer common uses
Abdominal organs, muscles, joints and tendons
Curved array transducers
Multiple crystals arranged in an arc and sequentially triggered
Also know as curvilinear transducer
Curved array transducer ad and dis
\+good near field resolution \+no moving parts \+diverging beam -large contact area (but less than linear) - diverging far field
Curved array transducer common uses
Abdominal organs, pregnancy diagnosis
Which is the best all purpose probe
Microconvex - type of curved array transducer- has smaller footprint
When use ultrasound
Work-ups of the abdomen and heart
Excellent soft tissue detail
Real tim motion helps to assess organ function
Measurements can assess structure or function
Limitations of ultrasound
Quality and usefulness depends on operator
Obtaining accurate and good quality images requires considerate practise and skill
Which terms are used to describe ultrasound images
Anechoic
Hypoechoic
Medium echogenicity
Hyperechoic
Anechoic
Produce no echo
Black on image
Fluid (blood,, bile, urine)
Hypoechoic
Little echo produced
DARK GREY
E.g. tissues with high water content- cartilage, muscle, real medulla
Medium echogenicity
Produce medium echo
Most soft tissues- liver spleen prostate, testes
Medium to light grey
Hyperechoic
Much echo
E.g gas and bone and mineralised tissue and dense connective tissue
White appearance
What are the characteristic of a desired environment for ultrasound
- Plenty of time
- Handler with bridle
- Seadtion
- Quiet
- Dark
- Enclosed space with room for manoeuvre
- No other horses around
How to prepare limb for ultrasound
Clip hair
Clean limb
Apply ultrasound coupling gel
Why do you need to clip thehair on the limb you are going to ultrasound
Ultrasound waves can’t pass through the dry hair/air interface
What do you clean the limb with
Clean with dilute chlorhexidine to remove grease
Why do you need to clean the limb that you are going to ultrasound
Grease and dirt will affect the passage of the ultrasound waves into the tissues and may result in artefact production
Why do yo need to apply ultrasound coupling gel when you are ultrasounding
Allows ultrasound waves to pass from the transducer (probe) into the tissues and back again. You will not gain an image if there is an air gap
Which type of transducer is used when ultrasounding distal limb of horse
Linear array transducer
What frequency is used wen ultrasounding the distal limb of the horse
7.5 and 10 MHz is used
When ultrasounding the distal limb of the horse what plane is used
Need to image in a longitudinal and a transverse plane
What is the normal appearance of the SDFT on an ultrasound
Is homogenous and echogenic
Palmar is to thee top of the image
What is the normal appearance of the DDFT on an ultrasound
Is homogenous and echogenic but has increased echogenicity compared to SDFT
What is the normal appearance of the Acessory ligament of the ddft on an ultrasound
Is homogenous and echogenic
What is the normal appearance of the suspensory ligament on an ultrasound image
Contains muscle, connective tissue, fat and ligament fibres and so appears heterogenous and can contain hypoechoic areas
What should a lesion be described in terms of on an ultrasound
Location Size Shape Changes in echogenicity Changes in normal architecture Anomalies
How can a tendon lesion be graded for changes in echogenicity
Type 1- slightly less echogenic than normal
Type 2 - half echogenic and half and hoof
Type 3 - mostly anechoic
Type 4 - completely anechoic
How can a tendon be scored for changes in fibre alignment on an ultrasound
Fibre pattern/alignment scoring (FAS) undertaken on a longitudinal view
0: >75% fibres aligned parallel to target path
1: 50-75% fibres aligned parallel to target path
2: 25-50% fibres aligned parallel to target path
3: <25% fibres aligned parallel to target path
What tissues is ultrasound useful to look at
Soft tissue
Joints (dynamic)
