T4: Ultrasounds and Endoscopes

Question 1

What is an ultrasound? Brieflty describe how it works.

Answer 1

• 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

Question 2

How high is the frequency of US waves? (range)

Answer 2

2 - 10 MHz

Question 3

How is the soundwave produced?

Answer 3

• w/ in the transducer by one or more crystals
• such crystals will vibrate when coltage is applied
• vibration generates sound waves of set frequency

Question 4

What is a-mode US?

Answer 4

• Simplest form
• For every echo received, a waveform is generated
• Does not give picture of tissue

Question 5

What is B-mode US?

How does it work?

Answer 5

• 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

Question 6

What is M-mode US?

Answer 6

• 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

Question 7

What is Doppler US?

Answer 7

• Detects echoes from moving RBCs
• used to study blood flow in heart
• If RBC moving towards probe = increased frequency echoes, and vice versa

Question 8

What is hypoechoic? How does it show up?

Answer 8

• low echo producing tissue –echo is weak, dot is dark (fluids)

Question 9

What is hyperechoic? How does it show up?

Answer 9

• high echo producing tissue –echo is strong, dot is bright (bone)

Question 10

What is echogenic?

Answer 10

tissue produces no echo

Question 11

Which tissues represent a barrier to US imaging and why?

Answer 11

• 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

Question 12

How are sound waves weakened as they pass through tissue?

Answer 12

• 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.

Question 13

How are the reflected echoes converted to a visual image?

Image on screen relative to?

Answer 13

• 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

Question 14

What is the range that US probes may come in?

And what is each used for?

Answer 14

• 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 (“)

Question 15

List the parts of an US machine

Answer 15

• Probe
• VCR and printer outlets
• On/Off switch
• Brightness
• Contrast
• Gain
• Date/time
• Patient ID
• Labeller
• Modes
• Reverse
• Print
• Menu buttons

Question 16

What is the function of the gain?

Answer 16

• 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

Question 17

What substance should you use to clean the US?

Answer 17

water soluble gel or metho

NOT PARAFFIN OR MINERAL OIL

Question 18

Fluid is what kind of echo and how does it appear?

Answer 18

hypoechoic and appears black

Question 19

Air is what kind of echo and how does it appear?

Answer 19

hyperechoic and produces a reverberation artefact, so air shows as horizontal lines echoing continually back and forward

Question 20

Tissue is what kind of echo and how does it appear?

Answer 20

moderately hypoechoic, is echogenic and produces shades of grey

Question 21

Fat is what kind of echo and how does it appear?

Answer 21

hypoechoic and appears black

Question 22

How should you prepare the patient for US?

Answer 22

• restraint
• clip hair
• apply acoustic gel
• aim to have organ you wish to examine as close as possible to probe

Question 23

Why do we clip the patients hair when preparing for US?

Answer 23

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.

Question 24

What is an echocardiogram?

Answer 24

• 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

Question 25

A bit about abdominal US?

Answer 25

• 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.

Question 26

What are some ways of collecting a biopsy?

Answer 26

• 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

Question 27

Is US reliable at determining the number of babies in a pregnant animal?

Answer 27

No

Question 28

Is it normal in some bitches/queens that the ovaries may not be visualised (imaged)?

Answer 28

Yes

Question 29

Can you image a non-pregnant uterus in bitches?

Answer 29

No

Question 30

What are flexible endoscopes used for?

Answer 30

git-oscopy, colonoscopy and bronchoscopy

Question 31

What are rigid endoscopes used for?

Answer 31

rhinoscopy, cystoscopy, laparoscopy, orthoscopy, vaginoscopy and thoracoscopy

Question 32

What does a flexible endoscope consist of?

Answer 32

• glass fibre bundles contained w/in protective tubing
• light source
• water source

Question 33

What is the light/water used for in endoscopy?

If glass fibres break can they be replaced?

Answer 33

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.

Question 34

How should you clean an endoscope?

Answer 34

• 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

Question 35

How should endoscopes be stored?

Answer 35

• hung to dry in a straightened position in a well ventilated and secure place.
• They should not be stored un the carry case.

Question 36

What is laparoscope?

Answer 36

• 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

Question 37

What is the insufflator used for in laparoscopes?

Answer 37

to pump gas (CO2) into abdomen to distend and separate organs

Question 38

What is an arthroscope?

Answer 38

A rigid endoscope that is used for examining and performing surgery within joints.