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Vet Nurse Small Animal Diploma CQ > Diagnostic imaging (SA08) > Flashcards

Diagnostic imaging (SA08) Flashcards

1
Q

What are the dangers associated with radiography?

A
  • X rays are invisible
  • They are painless
  • Effects are ‘latent’ (not seen immediately, may only be seen years later
  • Effects are cumulative; repeated low exposures are as hazardous as a single large exposure
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1
Q

What are the principles of radiation protection?

A
  • X rays must only be taken if definite clinical justification
  • Exposure of personnel kept to minimum
  • Time - reduce need for repeat exposures
  • Distance - Stand 2 meters away
  • Shielding - Wear PPE, stand behind lead screen
  • No dose limit should be exceeded
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2
Q

What is the electromagnetic spectrum?

A
  • Radiations with similar properties
  • Low to high energy
  • Radio waves, Microwaves, Infared radiation, Visible light, Ultraviolet, X-rays, Gamma-rays
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3
Q

What do all the waves of the electromagnetic spectrum have in common?

A
  • Travel in waves
  • Travel at same velocity
  • Need no medium to travel, can pass through vacuum
  • Travel in straight lines
  • Interact with matter through absorption or scatter
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4
Q

What is the difference between radiowaves and x-rays?

A

RADIOWAVES
- Low energy radiation
- Low frequency
- Long wavelengths
X-RAYS
- High energy radiation
- High frequency
- Short wavelengths

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5
Q

How are x-rays different to other waves in the electromagnetic spectrum?

A
  • Penetrate matter visible light can’t as high energy
  • Interact with photographic film, produce latent image
  • Interact with phosphor in intensifying screen to produce visible light (fluorescence)
  • Interact with living tissues, produce bio changes
  • Energy can be captured and converted to produce electronic images
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6
Q

What are the 3 types of x-ray machines?

A
  • Portable
  • Mobile
  • Fixed
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7
Q

What are portable x-ray machines?

A
  • Wall mounted or on portable stand
  • Not very powerful
  • Old machines only produce 20mA
  • Newer machines can produce around 60mA
  • kV and mA are usually linked, a given kV delivers a set mA
  • Dental and equine
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8
Q

What are mobile x-ray machines?

A
  • Large transformer box and trolly
  • More powerful than portable machines
  • Produce up to 300mA
  • mA and kV can be set independently
  • Machines in practice (often x-hospital)
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9
Q

What are fixed x-ray machines?

A
  • Built in the room on overhead gantry/rails
  • Needs special electricity supply
  • Very powerful but more costly
  • Often linked to floating tables
  • Used in NHS
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10
Q

What is the x-ray beam made up of?

A
  • Photons (packets of energy)
  • Created when electrons are slowed down/stopped
  • Electrons are present in atoms of all elements
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11
Q

What does the structure of an atom consist of?

A
  • Protons (positively charged)
  • Neutrons (no electrical charge)
  • Electrons (negatively charged)
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12
Q

What does it mean for an atom to be electrically neutral?

A
  • Equal number of protons and electrons
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13
Q

Where in an atom are the different elements?

A
  • Protons + neutrons (centre of nucleus)
  • Electrons orbit nucleus in shells
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14
Q

How are the charges of atoms changed?

A
  • Changes to amount of electrons
  • More protons than electrons, positively charged, Cation
  • More electrons than protons, negatively charged, Anion
  • Atomic numbers are number of protons in nucleus
  • Important with how x-rays interact with different types of tissue and are seen on x-rays
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15
Q

What is needed for the on/off switch of a radiography machine?

A
  • Must have warning light when machine on
  • Now a ‘controlled area’, only radiography personnel allowed
  • Often directly linked to lights outside room
  • Should be isolator to turn off machine outside room in emergencies
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16
Q

What is a line voltage compensator?

A
  • Ensures incoming voltage in consistent
  • Produced by an autotransformer
  • Built in part of modern machines
  • Older machines may have indicator light
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17
Q

What are kilivolts (kV)?

A
  • High power electrical charge
  • Applied to target during exposure
  • Draws electrons across
  • Produced by a set up transformer
  • ‘Penetrating power’
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18
Q

What are Milliamps (mA)?

A
  • Low power electrical charge
  • Heats filament
  • Releases electrons during ‘prepping’ stage
  • Produced by a step down transformer
  • Number of electrons (quality)
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19
Q

What are seconds (S)?

A
  • Timer for exposure time
  • Some machines as low as 0.01 seconds
  • Most exposures made at 0.05-0.5 seconds
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20
Q

What are the differences in old and new machines with inputting settings?

A
  • Some modern machines automatically input settings from species, area and depth of patient
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21
Q

What are the 3 exposure factors?

A

kV
- Controls energy of photons
- Quality/penetrating power of primary beam
- Affects contrast and density of image
mA
- Controls number of photons
- Quantity/intensity of primary beam
- Affects density of image
s
- Controls number of photons
- Quantity/intensity of primary beam

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22
Q

What is mAs?

A
  • mA x s
  • Control number of photons per exposure
  • mA = number of electrons emitted
  • s = how long emission lasts for
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23
Q

What will happens if mAs or kV is too high?

A
  • Black, over exposed image
  • Few shades of grey
  • Everything dark grey
  • Flat, lacking contrast
24
Q

What happens if mAs or kV is too low?

A
  • White, underexposed image
  • x-rays not strong enough or not enough to penetrate tissues
  • Tissue pale on black background
  • Soot and whitewash film
25
Q

What does MRI stand for?

A

Magnetic Resonance Imaging

26
Q

What is an MRI machine?

A
  • Typically long thin tubed shaped
  • Powerful magnet running front to back
  • Body part must be in exact centre of magnetic field (isocentre)
  • Can take 2-D or 3-D map of body tissues
  • Magnet 30,000 x stronger than earth magnetic field
  • Can draw all metal objects within several yards
27
Q

How is an MRI image created?

A
  • Magnet causes nuclei of hydrogen atoms to line up in parallel formation
  • Body hydrogen atoms normally point in different directions
  • Radiofrequency wave produced by RF coil
  • H atoms move orthogonally (Resonance)
  • When turned off, move back to align with magnet
  • Another RF wave is produced
  • Signals produced are detected by RF coil and converted to form and image
  • Speed of H atom movement creates image
28
Q

What is ultrasound?

A
  • Sound energy at higher frequency than can be heard
  • Frequency determines how far waves travel through body
  • Higher frequency gives better pictures but can’t travel far
  • Different frequency transducer heads are available
29
Q

What does ultrasound equipment consist of?

A
  • Transducers
  • TV monitor
  • Control panel
30
Q

How can ultrasound images be stored?

A
  • On patient records
  • Printed
  • Uploaded to PACS
31
Q

What are the types of ultrasound transducers?

A

SECTOR ARRAY
- More suitable for SA as small contact area
LINEAR ARRAY
- More suitable for large animal

32
Q

How are ultrasound images produced?

A
  • Crystals in transducer alter shape when current is applied; piezoelectric effect
  • When applied to skin, waves pass through and ‘reflect’ off tissues, back to transducer
  • Returning sound waves cause vibration of crystals and converted back to electric impulses to create images
33
Q

What are ultrasound transducers?

A

Probes

34
Q

What is echogenicity?

A
  • Ability of tissue to reflect ultrasound wave
35
Q

What is anechoic?

A
  • Without echoes
  • No sound waves return
  • Appear black
  • Fluid
36
Q

What is the piezoelectric effect?

A
  • Crystals in ultrasound transducer change shape when electrical current is applied
37
Q

What is hypoechoic?

A
  • Not many echoes
  • Not many sound waves returned
  • Appear dark grey
  • Dense tissue
38
Q

What is hyperechoic?

A
  • Lots of echoes
  • Many waves returned
  • Appear bright white
  • Bones/gas
39
Q

What is acoustic resistance?

A
  • When sound waves bounce back off of tissues
40
Q

What does homogenous mean?

A
  • Of uniform composition
  • Smooth appearance
41
Q

What does heterogenous mean?

A
  • Not of uniform composition
  • Mottled appearance
42
Q

How does different tissue appear on a ultrasound?

A
  • Fluid is black - Anechoic
  • Tissues shades of grey
  • Bone/gas white - Hyperechoic
43
Q

What is the brightness or B mode in ultrasounds?

A
  • Most commonly used mode
  • Image of slice though organ/tissue
44
Q

What is the time-motion or M mode in ultrasound?

A
  • Vertical section through tissue
  • Constantly updated
  • Appears as rolling horizontal image
  • Heart scans
45
Q

What is the doppler mode in ultrasound?

A
  • Used to detect movement
  • Often used to detect blood flow
  • Colour doppler assigns colour according to speed and direction of flow
46
Q

What is contrast ultrasonography?

A
  • Small quantities of microbubbles of sulphur hexafluoride gas
  • Injected into blood stream in phospholipid capsules
  • Microbubbles reflect waves
  • Increased echogenicity in proportion to vascularity
  • Looks at direction of blood
47
Q

What other uses does ultrasonography have?

A
  • Allows for accurate sampling
  • FNA, biopsies
    -Tru-cut biopsy (larger sample)
  • Tru-cut requires heavy sedation or GA
  • Cystocentesis easier, especially if bladder small
48
Q

Why may starvation be needed for an ultrasound?

A
  • Full stomach causes increased echogenicity
  • Avoid regurge in sedated animal
  • Most animals won’t require sedation but stress and pain must be managed
49
Q

What is the purpose of contrast studies?

A
  • Visualise structures not normally seen on plain films
  • Due to surrounding tissue similar radio-opacity
  • Provides information re size, shape, position and structure
  • Information re function of organ
50
Q

What structures can be visualised using contrast media?

A
  • Oesophagus
  • Stomach
  • Stomach & SI
  • Large intestines
  • Bladder
  • Kidneys & Ureters
  • Vagina & Urethra
  • Spinal cord
  • Blood vessels & heart chambers
  • Internal structures of joints
51
Q

What must contrast agent have the ability to do?

A
  • Absorb a different amount of x-rays than the surrounding tissue
52
Q

What are positive contrast agents?

A
  • High atomic numbers
  • Barium AN = 56
  • Iodine AN = 53
  • More radio-opaque than tissue
53
Q

What are negative contrast agents?

A
  • Low atomic numbers
  • Air AN = 8
  • More radiolucent than tissues
  • Carbon dioxide sometimes used
54
Q

An ideal contrast agent should:

A
  • Show area of interest well
  • Non-irritant
  • Non-toxic
  • Persist in area of interest
  • Be totally eliminated from the body
55
Q

What is Barium?

A
  • For GI studies
  • Suspension, paste, powder
  • BIPS = Barium impregnated polyethylene spheres
56
Q

Powder and suspension Barium?

A
  • For stomach, small and large intestine
  • Care when administering orally
  • Aspiration causes granulomas
  • Fatal aspiration pneumonia
  • Contraindicated if perforation of oesophagus or bowels
  • Leakage into thoracic or abdominal cavity causes granulomas
  • Will persist indefinitely in those cavities.
57
Q
A

Vet Nurse Small Animal Diploma CQ (14 decks)

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