T4: Ultrasounds and Endoscopes Flashcards
What is an ultrasound? Brieflty describe how it works.
- It is a computer
- A US probe is connected to the comp, which transmits and receives US waves using a row of vibrating crystals
- These vibrations are then sequenced by the comp
- so when probe receices these US waves following transmission into tissue, a slice image is formed
How high is the frequency of US waves? (range)
2 - 10 MHz
How is the soundwave produced?
- w/ in the transducer by one or more crystals
- such crystals will vibrate when coltage is applied
- vibration generates sound waves of set frequency
What is a-mode US?
- Simplest form
- For every echo received, a waveform is generated
- Does not give picture of tissue
What is B-mode US?
How does it work?
- brightness mode
- every echo received transformed into a dot
- strong echo = bright dot (bone)
- weak echo = dark dot (fluid)
- For every echo a grey scale on the computer is formulated, so each echo has a different colour, giving an accurate reflection of tissue density
What is M-mode US?
- motion mode
- allows us to compare movement in tissue over time
- Commonly used to examine heart and to provide HR
- Vertical dots = 1cm, horizontal dots = 0.5sec
What is Doppler US?
- Detects echoes from moving RBCs
- used to study blood flow in heart
- If RBC moving towards probe = increased frequency echoes, and vice versa
What is hypoechoic? How does it show up?
- low echo producing tissue –echo is weak, dot is dark (fluids)
What is hyperechoic? How does it show up?
- high echo producing tissue –echo is strong, dot is bright (bone)
What is echogenic?
tissue produces no echo
Which tissues represent a barrier to US imaging and why?
- Interfaces b/w soft tissue and air/bone
- as sound waves are reflected from boundaries b/w tissues of differing sound wave transmission properties
- Where the difference is great, most of the sound wave is reflected, leaving little sound energy to penetrate deeper tissues
How are sound waves weakened as they pass through tissue?
- As passes through tissue it is reflected, scattered and absorbed
- As a result, the strength of the sound wave diminishes w/ increasing depth
- and the corresponding echoes will also be lessened in comparison to superficial echoes.
How are the reflected echoes converted to a visual image?
Image on screen relative to?
- Sound waves reflected => crystal vibration => electrical energy =>visual image.
- Image displayed on screen relative to:
- time delay b/w sending signal and receiving echo. This determines depth of echo
- direction from which echo was received
- intensity of echo will determine brightness of image
What is the range that US probes may come in?
And what is each used for?
- 3 MHz (examining deep objects)
- 5 MHz (most commonly used in equine work)
- 7.5 MHz (provides fine detail for tendons, joints, ligaments)
- 10 MHz (“)
List the parts of an US machine
- Probe
- VCR and printer outlets
- On/Off switch
- Brightness
- Contrast
- Gain
- Date/time
- Patient ID
- Labeller
- Modes
- Reverse
- Menu buttons
What is the function of the gain?
- Gain increases power to probe; > power > brightness
- Near / far gain echoes from afar are weaker then those that are close. Near gain set low to achieve close imaging, far gain set high ap to > strength of images from deeper tissue
What substance should you use to clean the US?
water soluble gel or metho
NOT PARAFFIN OR MINERAL OIL
Fluid is what kind of echo and how does it appear?
hypoechoic and appears black
Air is what kind of echo and how does it appear?
hyperechoic and produces a reverberation artefact, so air shows as horizontal lines echoing continually back and forward
Tissue is what kind of echo and how does it appear?
moderately hypoechoic, is echogenic and produces shades of grey
Fat is what kind of echo and how does it appear?
hypoechoic and appears black
How should you prepare the patient for US?
- restraint
- clip hair
- apply acoustic gel
- aim to have organ you wish to examine as close as possible to probe
Why do we clip the patients hair when preparing for US?
Unless good contact is made b/w transducer and patient’s skin, air will be trapped resulting in reflection of sound waves and poor image quality. To avoid this patient hair is usually clipped.
What is an echocardiogram?
- Imaging of the heart
- restricted to windows b/w lung lobes
- used to assess the heart in patients showing signs of heart disease or to determine the underlying cause of heart murmurs.
- allows us to measure heart size, ventricle wall thickness, function/state of valves and check for congenital defects
A bit about abdominal US?
- Gas w/in the GIT is the major impediment to producing clear images.
- It is not a definitive diagnosis, but rather a suitable tool to determine the presence of disease.
- In general, if an abnormality is identified w/in an organ on US, a biopsy of the lesion is required to establish a diagnosis.
What are some ways of collecting a biopsy?
- indirect US guided biopsy: US used to ID lesion and assess depth/angle of needle insertion (freehand)
- freehand puncture: tranducer in one hand, needle in other
- needle guidance systems: probe fitted w/ needle and directs it, may display pathway superimposed on screen
Is US reliable at determining the number of babies in a pregnant animal?
No
Is it normal in some bitches/queens that the ovaries may not be visualised (imaged)?
Yes
Can you image a non-pregnant uterus in bitches?
No
What are flexible endoscopes used for?
git-oscopy, colonoscopy and bronchoscopy
What are rigid endoscopes used for?
rhinoscopy, cystoscopy, laparoscopy, orthoscopy, vaginoscopy and thoracoscopy
What does a flexible endoscope consist of?
- glass fibre bundles contained w/in protective tubing
- light source
- water source
What is the light/water used for in endoscopy?
If glass fibres break can they be replaced?
Light passes from light source down glass fibres to illuminate tissue under observation.
Water is used to keep lens clean. I
f glass fibres break they cannot be replaced and cannot transmit light.
How should you clean an endoscope?
- clean immediately after use
- NEVER immerse it completely in water
- clean using alcohol gauze swabs, specialist scrubbing brush, disinfectant and cotton buds in a bowl or sink
- After cleaning lightly lubricate the air, water and suction valves periodically to prevent cracking
How should endoscopes be stored?
- hung to dry in a straightened position in a well ventilated and secure place.
- They should not be stored un the carry case.
What is laparoscope?
- Form of rigid endoscope that allows surgeon to view contents of abdominal cavity and perform key-hole surgeries
- Three key-hole incisions made:
- to insert laparoscopic viewer
- to insert insufflators
- to insert laparoscopic surgical instruments
What is the insufflator used for in laparoscopes?
to pump gas (CO2) into abdomen to distend and separate organs
What is an arthroscope?
A rigid endoscope that is used for examining and performing surgery within joints.
