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Clinical Nursing Jan exam > Diagnostic Imaging > Flashcards

Diagnostic Imaging Flashcards

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1
Q

State properties of x-rays

A

Part of electromagnetic spectrum (travels at same speed in straight line but varied wavelengths/frequencies)
High energy wave due to short wavelength and high frequency

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2
Q

How is velocity of an x-ray calculated?

A

Wavelength x frequency

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3
Q

Define wavelength

A

Distance between two consecutive peaks

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4
Q

Define frequency

A

Number of times peak passes a fixed point per second

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5
Q

How are wavelength, energy of the wave and frequency related?

A

Frequency is proportional to energy of the wave and inversely proportional to wavelength

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6
Q

What are gamma rays used for?

A

Scintigraphy

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7
Q

What are the different types of x-ray machines available and their features?

A

Portable- small and compact, easy to move, linked exposure, low output as use mains voltage
Mobile- uncommon, larger, higher output than portable
Fixed- permanently installed, tube on gantry, higher output due to specialised electrical supply

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8
Q

What are features on x-ray control pannels?

A 
On off button
Mains voltage compressor (usually automatic unless old machine, adjusts incoming voltage, varies 215-240V to keep kV constant)
kV control
mA control
Timer
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9
Q

What is the main legislation for use of x-rays and what is its main priciples?

A

Ionising radiations regulations 2017

Only radiograph for clinical reasons, exposure to personnel to minimum, dont exceed dose limits

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10
Q

Why is radiation dangerous and what effects can it have on the body?

A

Invisible, can’t feel, can penetrate, cumulative effects

Carcinogenic, somatic (changes to tissues shortly after exposure particularly rapidly dividing cells), genetic mutations

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11
Q

What are sources of radiation hazard?

A

Tube head
Primary beam
Scatter

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12
Q

What are ways of reducing effect of scatter?

A

Collimation
Keep area of interest close to plate
Lead protection worn
Grid used

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13
Q

What safety measures need to be in place for all practices using x-rays?

A

General- HSE notified of using x-rays, practice has RPS and RPA (radiation protection supervisor and advisor)
Local rules- no manual restraint, protection used in controlled areas, guidelines if pregnant, warning signs for exposure
System of work- legal requirement displayed, details RPA/RPS, description and access to restricted areas, how to respond to incidences, working practices

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14
Q

What is meant by a controlled area and what are features of it?

A

Where x-rays are taken and dose exceeds 7.5mSv/h
Specific room with lead lined or thick walls to prevent penetration
Large enough for 2 people to be 2m from primary beam
Warning signs and indicators of exposure
Restricted to classified personnel

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15
Q

How are staff protected from x-rays?

A

Minimal exposure- rotate staff, minimal time taking x-rays
Distance- at least 2m from primary beam, leave room where possible, never manually restrain
Barriers- PPE, lead glass, lead-plywood doors
Dosimetry- follow dose limits, wear dosimeter

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16
Q

What are types of dosimeters available in practice?

A

Film badges- film blackens in proportion to exposure

Thermoiluminescent detectors- crystal absorbs radiation, heating causes light emission proportional to radiation dose

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17
Q

What are the protocols in place for dosimeter monitoring?

A

Worn for 4, 8 or 13 weeks then returned to NRPB for reading, reports kept for 2 years
Need individual badges worn at waist level, cant wear outside practice

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18
Q

State the two methods of x ray formation

A

General emission- major

Characteristic emission- minor

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19
Q

Describe how general emission x-ray formation works

A

Electrons rapidly decelerate when hit tungsten target as the pass through tungsten atoms and interact with electrons in atoms, energy lost from deceleration released as x-rays

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20
Q

Describe how characteristic x-ray formation works

A

Incoming electrons knock out electrons from tungsten orbits and electron drops from outer to inner shell releasing energy as x-rays

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21
Q

Describe the x-ray tube

A

Cathode and tungsten anode in vacuum, immersed in oil to help heat conduction and insulation, surrounded by lead except window for x-ray beam

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22
Q

Describe how x-ray tube generates x-rays

A

Small current passed through cathode filament heating it up producing cloud of free electrons known as thermionic emission
Focusing cup keeps cloud of electrons together preventing cathode repelling
Potential difference applied across tube causes electrons to hit tungsten target and x-rays are produced

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23
Q

Why is heat a problem in x-ray generation?

A

Interaction between electrons and tungsten is 99% heat and 1% x-ray generation
Electrons get focused on focal spot so heat dissipation is issue

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24
Q

What are the two types of anodes used to aid heat dissipation of x-ray generation?

A

Stationary- tungsten in block of copper so conducts heat from target, portable machines
Rotating- anode on disk with angled edge, tungsten track around edge to heat gets evenly distributed and is lost by radiation and convection from disk, on larger machines

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25
Q

What is meant by kV control?

A

Controls potential difference across tube between anode and cathode

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26
Q

What does mA control do?

A

Varies small current heating the cathode

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27
Q

How does the timer on x-ray control panel work?

A

Closing activates kV/high tension and mA/filament circuits

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28
Q

Describe how kV control works

A

Step up transformer supplies high voltage across tube with higher kV the higher potential difference across the tube, faster electrons will travel so have more kinetic energy and produce higher energy x-rays

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29
Q

Why is higher kV needed, what is typical kV ranges and how does increasing by 10kV effect exposure?

A

To produce higher quality images and to penetrate thicker tissues
40-120kV
10kV increase doubles exposure

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30
Q

How does mA control effect the amount of x-rays produced

A

Allows electrons to be emitted from the cathode, higher the mA the hotter the cathode gets and more electrons are accelerated across the tube, producing more x-rays

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31
Q

What are the typical ranges for mA?

A

Portable- 20-60mA

Fixed- 1000mA

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32
Q

How is time of exposure linked with x-rays production?

A

Increasing time increases number of x-rays produced

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33
Q

What is known as mAs?

A

mA and time

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34
Q

What effect does doubling mAs have on exposure?

A

Doubles exposure

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35
Q

How is mAs affected for thicker tissues?

A

Needs to be higher

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36
Q

What parameters are considered for exposure charts?

A 
kV
mA
s
Distance from x-ray tube, animal and plate
Use of grid
Body part
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37
Q

Describe how an exposure chart is created

A

Note exposure factors used on good images to build up a bank of them for different situations
Take exposure and increase kV when tissues are thicker
Repeat bad images until you get a good image to record

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38
Q

What must be the same to use exposure charts?

A

Machine
Film focal distance
Digital detector
Use of grid

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39
Q

What is seen for over and under exposure?

A

Overexposed- areas of blackness

Underexposed- grainy and lacking contrast

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40
Q

What is the relationship between intensity of x-ray and distance from x-ray tube?

A

Intensity is inversely proportional to square of distance from x-ray tube
Doubling distance from tube quarters intensity of radiation

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41
Q

Define film focal distance/FFD

A

Distance from x-ray tube to image receptor

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42
Q

What need changing if FFD is changed and how is it calculated?

A

mAs

New mAs = old mAs x (new distance squared/old distance squared)

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43
Q

Define object film distance

A

Distance between object radiographed and x ray detector

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44
Q

What is the effect of increasing object film distance on the image produced?

A

Gets magnified

Reduces sharpness due to penumbra

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45
Q

How is distortion of images prevented?

A

Keep area parallel to cassette and perpendicular to x-ray beam

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46
Q

What is the focal spot in x-ray machines?

A

Area of anode hit by electrons

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47
Q

What are advantages and disadvantages of keeping focal spot small as possible?

A

Advantages- image produced best if there’s a point source of x-rays, limits penumbra
Disadvantages- causes issues for heat dissipation

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48
Q

When is fine focus used in x-ray machines?

A

Smaller and thinner areas of anatomy

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49
Q

Define penumbra

A

Margin of blurring around edge of a structure due to beam diverging

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50
Q

What is the difference between actual and effective focal spots?

A

Target on anode is angled so electrons hit actual focal spot then beam is produced from smaller effective focal spot

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51
Q

Why is filtration of x-rays needed?

A

X-ray beam contains spectrum of energies

Low energy x-rays have insufficient energy to penetrate to produce an image so thin sheet of aluminium filters them out

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52
Q

What is meant by collimation?

A

Using light beam diaphragm to reduce aperture therefore primary beam size produced on the patient

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53
Q

What are the benefits of collimation?

A

Reduce unnecessary exposure to the patient
Reduce scatter produced
Improves image quality
Reduce exposure into controlled area

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54
Q

State the ways x-rays can interact with matter

A

X-ray photons pass through unchanged
X-ray photons are absorbed
X-ray photons are scattered

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55
Q

How can x-ray photons pass through matter unchanged and what effect does this have on the image produced?

A

Travel in straight line without losing energy

Forms useful x-ray image

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56
Q

Define radiolucent

A

Permeable to x-rays

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57
Q

Define radiopaque

A

Blocks x-rays

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58
Q

Describe how x-rays can be absorbed as they pass through matter

A

Depending on if material is radiolucent or radiopaque depends on proportion absorbed, depends on atomic number of tissues atoms

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59
Q

How does absorption of x-rays differ between tissues? (general, bone, gas, soft tissue)

A

General- higher atomic number, higher density and thicker tissue increase absorption due to more interactions
Bone- high atomic number, good absorption
Gas- low density, poor absorber
Soft tissue- intermediate atomic number and density, varied absorption

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60
Q

What colours are seen on x-rays when passing radiolucent and radiopaque tissues?

A

Radiolucent- black
Radiopaque- white
Between- grey

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61
Q

Describe what causes x-ray photons to scatter when interacting with matter and the impact this has

A

Deflected in random directions, some losing energy

Reduces image quality and not useful as dont reflect anatomy, increase exposure risk

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62
Q

When and why are grids used?

A

At high exposures to reduce the large amounts of scatter than will be produced, improving image quality

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63
Q

What is an x-ray grid?

A

Flat plates with series of thin lead strips to absorb scatter alternating thin radiolucent strips to allow primary beam through cassette

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64
Q

Why does use of a grid increase exposure factors needed?

A

Some of primary beam gets absorbed by the lead and some scatter passes through spacing material

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65
Q

What is a grid ratio?

A

Height of strips/width of spacing

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66
Q

What are typical grid ratios and what affect does a higher ratio have?

A

6:1-12:1

More efficient at removing scatter but removes more primary beam so need higher exposure

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67
Q

What effect does increasing lines per cm on a grid have?

A

Removes more scatter but absorbs more primary beam so need higher exposure

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68
Q

Define grid factor

A

Number mAs is multiplied by when using grid

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69
Q

What is a parallel grid and what are its advantages and disadvantages?

A

Parallel equal height lead strips
Advantages- cheap, easy to use, can use either way up, at any FFD or centring point
Disadvantages- beam divergence means increased primary beam absorption at edges

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70
Q

What is a focused grid and what are its advantages and disadvantages?

A

Lead strips slope progressively towards grid periphery
Advantages- no image cut off as mimic divergence
Disadvantages- needs correct orientation and centring, correct FFD needed to match divergence, expensive and complex

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71
Q

What is a pseudo-focused grid and what are its advantages and disadvantages?

A

Parallel lead strips with height reducing to periphery
Advantages- reduction of grid ratio to periphery compensates cut off in parallel grids
Disadvantages- needs correct orientation, more expensive

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72
Q

What is a cross-hatched grid and what are its advantages and disadvantages?

A

Lead strips at right angles to each other
Advantages- efficient at removing scatter
Disadvantages- need high exposures, accurate centring, expensive

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73
Q

What is a moving grid and what are its advantages and disadvantages?

A

Parallel grid permanently under radiolucent x-ray table, oscillates during exposure
Advantages- fine lines as in stationary grids blurred so not seen
Disadvantages- expensive, always used

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74
Q

What is meant by digital imaging in radiography?

A

X-ray machine and table are unchanged and images are produced on various image receptors

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75
Q

What are the advantages of digital imaging?

A

Low running costs
Higher quality images
Adjustments can be made reducing time and exposure
Easy to store, communicate and retrieve images

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76
Q

What are the disadvantages of digital imaging?

A

Viewing limited to availability of computer
May have artefacts
Need backing up

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77
Q

Describe how computed radiography works

A

Uses storage phosphor cassette
Energy from interactions with x-ray beam is stored in phosphor, later released as light when excited by laser beam in plate reader
Light is captured and quantified by photomultiplier tubes which converts to electrical signal as image on screen

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78
Q

How is phosphor plate for CR erased for re use?

A

Bright light removes residual energy, takes 1-2 minutes

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79
Q

Describe how direct radiography works

A

Patient information is entered into system
Flat panel detector produces instant image on connected monitor
Processing algorithms and formula reconstructs image depending on anatomical region being viewed
Can manipulate filters, contrast, size, orientation, measurements

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80
Q

How are digital images stored?

A

Computer files in ditcom format
Regularly backed up, can print at extra cost
Long term storage on PACS for identification, manipulation, back up and retrieval of images

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81
Q

What is meant by PACS and ditcom?

A

PACS- picture archiving and communication system

Ditcom- digital imaging and communications in medicine

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82
Q

What is meant by a satisfactory radiograph?

A

A radiograph that can be diagnostic

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83
Q

List factors assessed when looking at image quality

A 
Opacity
Contrast
Sharpness
Technique faults
Artefacts
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84
Q

How does opacity affect image quality and what effects opacity?

A

How black or white overall

Depends on tissue type, thickness, exposure factors, processing of image

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85
Q

How does contrast affect image quality and what effects it?

A

Difference in tone between areas either long or short scale contrast
Depends on part being x-rayed, atomic number, density, algorithm applied, scatter

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86
Q

How does sharpness effect image quality and when affects it?

A

How clearly defined the image is

Depends on movement, scatter, object film distance

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87
Q

State some technique faults that effect image quality of radiographs

A 
Poor positioning
Not enough projections taken
Not using L/R markers
No date or patient information
Movement blur
Incorrect grid use
Poor centring and collimation
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88
Q

List some artefacts that can affect quality of radiograph image

A

Double exposure- only on CR
Digital exposure error
Uberschwinger artefact- radiolucent zone around areas with high density difference caused by excess edge enhancement by computer
Ghost artefact- residual image from previous radiograph
Moire artefact- bands across image on CR due to interference between frequency of laser reader and lines/cm on grid
Dirt on light guide

89
Q

What is contrast media?

A

Agents more or less opaque than surrounding tissue

90
Q

What is the purpose of contrast studies?

A

Introduce contrast between otherwise same contrast structures
See normally poorly visible structures
Gain information on soft tissues and internal anatomy of structures

91
Q

What is the difference between the two types of contrast media?

A

Positive- high atomic number, white on radiograph

Negative- low density, black on radiograph

92
Q

What are examples of each type of contrast media?

A

Positive- barium, iodine

Negative- air, carbon dioxide

93
Q

State the use, formulation and properties of barium for contrast studies

A

GI tract to provide good mucosal detail
Powder or suspension, reasonably palatable
Inert, non-toxic, no osmotic effect so wont draw in water

94
Q

What are the properties of ionic iodine for contrast studies?

A 
Irritant extravascularly
Toxic in large doses
Viscous, reduced before use with warming
Water soluble preparation
Contraindicated with CV or renal insufficiency and for myelography in subarachnoid space
95
Q

What are the properties of non-ionic iodine for contrast studies?

A

Viscous
Water soluble preparation
Cause potential side effects- anaphylaxis, nephrotoxicity, pyrexia
More expensive

96
Q

How is iodine given to patients for contrast studies and how is it removed from the body?

A

IV

Renal excretion

97
Q

What are the positives and negatives of negative contrast media?

A

Positives- cheap, easy to use, minimal risk or side effects, combine with positive for double contrast study
Negatives- small risk of air embolism, poor mucosal detail, less contrast than positive due to air already in body

98
Q

What are indications for performing contrast studies?

A

The study will demonstrate a lesion
Time
Cost

99
Q

How do you prepare for contrast studies?

A

Take plain radiographs to ensure its needed and to check correct positioning and exposure
Ensure patient is properly restrained

100
Q

What situations mean a contrast study isn’t needed?

A

Plain radiography is enough
Endoscopy for GI better
Ultrasound for urinary tract in many cases
CT and MRI used instead of myelography

101
Q

What are indications for doing barium swallow study and what are risks?

A

Indications- dysphagia, regurgitation, suspected oesophageal rupture
Risks- aspiration, especially if struggling to swallow, weak, respiratory distress

102
Q

What is shown by a barium swallow test and how is it carried out?

A

Shows pharynx and oesophagus when swallowing, most of barium should be in stomach after swallowing
Use liquid barium or food with barium in, iodinated contrast if suspect rupture

103
Q

What is the purpose of barium follow through and how is it carried out?

A

Evaluate stomach and small intestine

Liquid barium give by mouth or stomach tube, radiographs taken immediately and at intervals until reaches colon

104
Q

What are disadvantages to barium follow through study?

A

Time consuming

Can be hard to interpret radiographs so endoscopy or ultrasound preferred

105
Q

What is the purpose and how is barium enema carried out?

A

Evaluate large intestine

Liquid barium infused into rectum post enema, can follow with air for double contrast

106
Q

What are advantages and disadvantages of barium enema contrast study?

A

Advantages- minimal complications
Disadvantages- messy, hard to interpret, faeces remaining look like lesions, could have leakage or rupture if over inflate, tend to use ultrasound instead

107
Q

What contrast media is used for the urinary tract and why?

A

Water soluble iodinated contrast medium as barium is irritant to bladder and cant be used IV

108
Q

What is the purpose of excretory urography study and how is it carried out?

A

Assess kidney, ureters and vesicoureteral junction
Bolus of contrast given to peripheral vein, follow through with radiographs taken immediately and then every 5 minutes for 15 minutes

109
Q

What do the radiographs taken at each time interval for excretory urography show?

A

Immediately- nephrogram (deliniates kidneys)
5 minutes- pyelogram (renal pelvis visible)
10 minutes- ureterogram (ureters visible)
15 minutes- ureterovesicular junction (where ureters meet bladder)

110
Q

What does cystography show and how is contrast introduced?

A

Delineates bladder

Introduced via urinary catheter

111
Q

What are the 3 types of cyctography?

A

Pneumocystogram- air only, shows bladder location, any large masses or thickenings
Positive contrast cystogram- iodinated contrast used
Double contrast cystogram- uses air and iodine to deliniate wall and contents

112
Q

What is the purpose of urethrography and how is it carried out and are there any risks?

A

Delineate urethra and vagina
Water soluble iodinated contrast introduced via foley catheter to distal urethra, radiographs taken at end of injection when vagina and urethra are distended by contrast. Can be combined with cystography
Small risk of urethral damage

113
Q

What is the purpose of myelography?

A

Delineate subarachnoid space, localise lesions on spinal cord or surrounding structures

114
Q

Why do you need to use non-ionic water soluble contrast medium for myelography?

A

Ionic can cause seizures and arachnoiditis

115
Q

Why is CT and MRI preferred over myelography and when is CT myelography used?

A

Non invasive

increases soft tissue detail

116
Q

What are the risks of myelography and how can they be reduced?

A

Seizure if enters the brain, minimal neurotoxicity otherwise

Keep head elevated on recovery to stop entering the brain, IV catheter placed with IV diazepam available

117
Q

What are other contrast studies that can be performed?

A

Angiography- blood vessels
Arthrography- joints
Fistulography- sinus tracts

118
Q

What is ultrasound and why can’t it travel through a vacuum?

A

High frequency sound waves

Relies on compression and relaxation of physical material

119
Q

How does the velocity of ultrasounds differ for air, soft tissue and bone?

A

Air- 330m/s
Soft tissue- 1540m/s
Bone- 3200m/s

120
Q

What are advantages of ultrasound?

A 
Widely available
Safe, no ionising radiation
Quick
Non-invasive
Rarely need GA
Good soft tissue detail, including internal structures
Can distinguish between soft tissue and fluid
Guide biopsies
Functional information of heart
121
Q

What are some disadvantages of ultrasound?

A

Relatively expensive
Easily damaged
Need to clip patient
Experience needed to interpret images, real time so cant look back
Gas, fat and bone limits vision
Biopsies usually needed for definitive diagnosis

122
Q

How is ultrasound produced?

A

Piezoelectric effect- electric voltage applied to disk in transducer and disk expands and contracts with movement proportional to voltage, movement produces a sound wave

123
Q

What is meant by pulsed production of ultrasound?

A

Transducer produces ultrasound by piezoelectric effect then sends out pulse of sound (3 wavelengths of 1.5mm at 1microsecond)
Transducer waits for sound to echo from tissue which distorts the disk and generates voltage proportional to pressure
Machine processes and displays as an image

124
Q

What is the equation for acoustic impedance?

A

Density of tissue x speed of sound in tissue

125
Q

How do ultrasound waves interact with the patinet?

A

Travels through tissues with varied acoustic impedance and when crosses boundary between tissues of different acoustic impedance some gets reflected back, with proportion reflected back dependent on difference of acoustic impedance between the tissues

126
Q

How does reflection of ultrasound differ at different boundaries?

A

Weak reflection- soft tissue boundaries

Large reflection- soft tissue bone interface

127
Q

What is meant by long and short scale contrast?

A

Long scale- many shades of grey

Short scale- black and white

128
Q

What is the difference between specular and non-specular reflection of ultrasound?

A

Specular- beam hits large smooth surface
Non-specular- beam hits small structures so weak echoes get re-radiated in all directions so give texture/speckled appearance to organs

129
Q

State the 3 display modes for ultrasound

A

A mode- amplitude
B mode- brightness
M mode- motion

130
Q

What is A mode ultrasonography used for?

A

Opthamology

131
Q

How does B mode ultrasonography work?

A

Pencil beam of ultrasound scans back and forth to build up an image, brightness on image depends on amplitude of returning signals and position on image depends on time for signal to return
Image is a slice through patient so need to scan in multiple planes

132
Q

What is M mode ultrasonography used for and how does it work?

A

Mainly cardiology
Shows movement of points along a line with image displayed as position vs time
Continually produces a trace

133
Q

Describe how an ultrasound exam is carried out

A

Select area of interest, ideally avoiding bone and gas if possible
Clip and clean skin, surgical spirit removes grease (can damage transducer), need good contact with skin
Apply lots of acoustic gel
Place transducer on skin
Keep patient still with restraint, sedation or GA

134
Q

Why should you starve overnight for abdominal ultrasounds?

A

Improves ability to examine organs

Allow safe sedation/GA if needed

135
Q

How should you clip for ultrasound for abdomen, heart, left kidney and right kidney?

A

Abdomen- xiphisternum to pubis, follow line of costal arch to lumbar muscles including last 2-3 intercostal spaces
Heart- right side, 4th to 6th intercostal space, costochondral junction to sternum
Left kidney- lateral approach, behind last rib and below lumbar muscles
Right kidney- last 2-3 intercostal spaces and below lumbar muscles

136
Q

What are phased and linear ultrasound transducers?

A

Phased- beam steered electronically

Linear- lots of elements triggered in turn

137
Q

Why should practice have a range of frequencies and types of ultrasound transducers?

A

Not one suitable for everything

Consider type, footprint and frequency

138
Q

What is a phased array transducer and what are the benefits of it?

A

Beam steered electronically

Easy to manipulate, small contact area but wide field at depth

139
Q

What is a linear array transducer and what are the benefits of it?

A

Multiple elements triggered in groups

Large contact area, large field of view near skin so good for superficial structures

140
Q

What is a microconvex/convex transducer and what are the benefits of it?

A

Elements arranged in curve triggered like linear

Easy to manipulate, small contact area with wide field at depth

141
Q

What frequency are high frequency transducers and what is their resolution and image at depth like?

A

Frequency- 7.5-18MHz
Resolution- good
Can’t image at depth

142
Q

What frequency are low frequency transducers and what is their resolution and image at depth like?

A

Frequency- 2.5-5MHz
Resolution- poorer
Can image at depth

143
Q

What are high frequency ultrasounds useful for and what can they not view properly?

A

Good image resolution, good for superficial structures or for small animals
Can’t penetrate deep

144
Q

What are low frequency ultrasounds useful for?

A

Deep structures and large animals

145
Q

Why does frequency of transducers need to vary?

A

Velocity is constant in soft tissues and as frequency increases wavelength decreases

146
Q

How do you get better resolution in ultrasounds and why?

A

Short wavelength and pulse length because when longer reflections overlap on return so objects close are seen as one

147
Q

How should you care for ultrasound machines?

A

Regular cleaning to remove gel and hair build up
Safely store leads and transducers
Service regularly

148
Q

Define echogenic

A

Produces ultrasound echo

149
Q

Define anechoic

A

No ultrasound echo produces

150
Q

What is the appearance of fluid, fat and soft tissues on ultrasounds?

A

Fluid- black (anechoic)
Fat- white (echogenic)
Soft tissues- variable, compare to other tissue

151
Q

What can be seen at borders of soft tissue with gas and bone in ultrasound?

A

Gas- totally reflects sound so cant see past the gas

Bone- reflects or absorbs sound so cant see past but can see bone surface

152
Q

What is meant by advanced imaging techniques?

A

Imaging techniques used mainly by referral centres that usually produce cross sectional images

153
Q

What is shown by MRI and CT and scintigraphy images?

A

MRI and CT- slices through

Scintigraphy- functional remodelling of bone

154
Q

What do CT and MRI stand for?

A

CT- computed tomography

MRI- magnetic resonance imaging

155
Q

What are safety measures for CT?

A

Same restrictions as radiography

Whenever on can emit radiation due to calibration etc so room stays locked

156
Q

How does CT work?

A

Cross sectional imaging produced by ionising radiation
Rotating x-ray and detector take 360 degree x-ray and patient is advanced through as machine rotates
Computer reconstructs data into 3D image with tissue represented on image the same as x-ray

157
Q

What is meant by windowing in CT?

A

Choice of how to display information

158
Q

How does windowing of CT work?

A

Tissues get assigned Hounsfield unit depending on attenuation of beam, window level and width, choses to optimise certain tissues details

159
Q

What are uses of CT?

A

Good for bony structures

Multiple anatomical reconstructions from one scan

160
Q

List advantages of CT

A

High bony detail and more soft tissue detail than x-ray
Can use contrast
Shorter scan time than MRI
Can create 3D reconstructions and models for surgical planning
Good for lung pathology and detecting metastatic disease
Avoids superimposition of joints
Cheaper than MRI

161
Q

List disadvantages of CT

A 
Limited availability
Expensive
Need to sedate
Higher radiation doses than x-ray
Limited to horses head or extremeties
162
Q

How does scintigraphy work?

A

Radioisotope (technetium 99m) is bound to substance to determine where in body to localise then injected into the body
Binding is increased in areas with increased metabolism (tumours etc)
Radiation emitted is measured by gamma camera

163
Q

What are used of scintigraphy?

A

Detect equine skeletal injury or lesions undetectable by radiography

164
Q

What are advantages of scintigraphy?

A

Available in most large equine practices

Element of functional assessment as uptake depends on metabolism and anatomy

165
Q

What are disadvantages of scintigraphy?

A

Ionising radiation risk to patient and staff
Patient radioactive for 48 hours, minimise contact, correctly dispose bedding, faeces etc
Poor detail produced so hard to interpret image
Additional legislation due to excretion of radioactive isotopes

166
Q

How does MRI work?

A

Cross sectional image produced using magnetic fields
Nucleus with odd number of protons and/or neutrons spins creating mini magnetic field which combine to form strong field
Protons get targeted
Patient in magnetic field causes magnetic moments of spinning nuclei to line up with magnetic field
When patient bombarded with radio waves nuclei temporarily disorientate and emit radio signals until they realign when radio waves stop
Timing depends on tissue environment and emitted signals from patient are detected giving information about tissue composition, appearance depends on timing of pulses and echoes which the computer reconstructs into an image

167
Q

What are uses of MRI?

A

Neurology
Soft tissue lesions
Bone marrow oedema

168
Q

What are advantages of MRI?

A

Good contrast resolution
Excellent soft tissue detail
No ionising radiation so not long term damaging

169
Q

What are disadvantages of MRI?

A 
Not widely available 
Expensive
Need to be completely still under GA
Cant have metallic objects around
In horses can only use on distal limbs under standing sedation
170
Q

Define positioning

A

Use of pads, wedges, sand bags, ties to ensure that the animal is straight and restrained

171
Q

What should be checked before positioning animals for diagnostic imaging?

A

Correct animal
Projections needed
Exposure factors and use of grid
Correct positioning, collimation and centring

172
Q

Why is it important to restrain animals for diagnostic imaging?

A

Produce good quality images

Avoid manual restraint

173
Q

State some positioning aids

A

Radiolucent troughs- VD or DV
Foam pads and wedges
Floppy sandbags
Tapes, ropes and ties

174
Q

Define centring

A

Using light beam diaphragm to position primary beam over correct area

175
Q

Briefly describe how to position patients for radiography

A

Put in comfortable position
Place markers and make sure are visible
Centre and collimate area of interest

176
Q

What are features of a good quality radiograph?

A

Present identification and markers
Correct area and projection with suitable exposure factors, contrast, density and sharpness
No artefacts
Repeats done when needed

177
Q

What information can you gain from the projection the radiography is taken?

A

Path of beam from x-ray tube to image receptor
Animal positioning
If lateral named after side animal is lying on

178
Q

When can certain projections not be taken?

A

DV or VD shouldnt be taken after lateral as lung will have collapsed
Dont take VD if dyspnoeic take DV instead

179
Q

Describe how to position for lateral thorax

A

Right lateral recumbency
Wedge under sternum to keep spine and sternum at same height
Forelegs pulled cranially
Centred at caudal border of scapula
Collimate 1/2 to 2/3 thorax including sternum and shoulder

180
Q

Describe how to position for DV/VD thorax

A

Dorsal or sternal recumbency
Support legs so not over thorax
Animal straight head to toe, may need trough
Centre on midline at highest point of scapula (DV) or middle of sternum on midline (VD)
Collimate to include all of lungs and chest wall edges

181
Q

Describe how to position for lateral abdomen

A

Right lateral recumbency
Wedge under sternum
Cranially positioned forelimbs
Hind limbs held parallel with pad to prevent rotation and pulled caudal to prevent superimposition
Sandbag over neck
Centre at level of last rib halfway down abdominal wall
Collimate to include cranial margin of diaphragm and pubic rim

182
Q

Describe how to position for VD abdomen

A

Dorsal recumbency
Legs held by sandbags
Trough to prevent rotation and needs to be straight head to toe
Centre at umbilicus along midline
Collimate to include entire diaphragm and pubis

183
Q

Describe how to position for PD hock and DP carpus

A

Animal in sternal with limb rotated and extended until straight
Centre over joint
Collimate to include soft tissues and 1/3 adjacent long bones

184
Q

Describe how to position for mediolateral hock and carpus

A

Side to radiograph place on cassette, other leg pulled back and sandbagged
Centre over joint
Collimate to include proximal phalanges and distal tibia/radius

185
Q

Describe how to position for mediolateral elbow and stifle

A

Joint in contact with cassette and other leg held back
Joint flexed or extended depending on whats being looked for
Centre over joint
Collimate to include distal/proximal long bones

186
Q

What is shown on flexed and extended elbow radiographs

A

Flexed- anconeal process and humeral epicondyles

Extended- cranial aspect of radial head and humeroradial joint space

187
Q

Describe how to position for cranio-caudal elbow

A

Sternal with leg extended, head towards limb being examined
Centre over joint
Collimate to include 1/3 humerus and antebrachium
Can use horizontal beam, animal in lateral recumbency with examined limb most upper

188
Q

Describe how to position for craniocaudal or caudocranial stifle

A 
Sternal so limb is straight
Craniocaudal- limb extended forward
Caudocranial- limb pulled back
Centre below patella
Collimate to include proximal and distal long bones
189
Q

Describe how to position for VD pelvis

A

Dorsal recumbency with legs extended and rotated so stifles are straight
Legs and tail tied
Hocks supported ad weighed down
Centre over pubis at level of greater trochanter

190
Q

Describe how to position for mediolateral shoulder

A

Limb examined nearest film and drawn forwards to extend shoulder
Head and neck extended
Upper limb retracted
Centre at level of and caudal to greater tuberosity

191
Q

Describe how to position for spinal radiographs

A

Need anaesthetising for good image quality as sedation keeps some muscle tone and rotation
Pads under head, neck and waist to keep spine straight
Take multiple images so beam passes directly through the joint rather than diverging at the edges

192
Q

Describe how to position for lateral cervical spine

A

Lateral recumbency
Support spine to remove natural curvature
Pulled back forelimbs so shoulder doesn’t superimpose
Centre at C3
Collimate to include base of skull

193
Q

Describe how to position for VD cervical spine

A 
Dorsal recumbency
Forelimbs pulled down over chest 
Neck straight
Centre over C3 on midline
Extubate to prevent superimposition
194
Q

Describe how to position for thoracic and lumbar spine

A 
Lateral recumbency
Support curves of spine
Pad between legs to prevent rotation 
Extend limbs
Centre over region of interest
Make sure films overlap if taking multiple
195
Q

Describe how to position for lumbosacral junction

A

Lateral recumbency
Pads between hind limbs
Spine supported
Centre between iliac wing and greater trochanter

196
Q

Describe how to position for ventrodorsal skull

A

Dorsal recumbency
Support with sandbags
Hard palette to table
Centre to level of interest along midline

197
Q

Describe how to position for lateral/oblique skull

A

Lateral recumbency
Support nose to keep head in lateral or at desired angle
Centre over area of interest

198
Q

Describe how to position for rostrocaudal tympanic bulla

A

Dorsal recumbency
Neck flexed until nose upright
Mouth held open in V with ties and gag
Centre where tongue goes down back of throat

199
Q

Describe how to position for DV intra-oral nose

A

Sternal recumbency
Hard palette to table top
Centre between eyes on midline
Collimate to include nose and soft tissue around mouth
Can have imaging plate in mouth to prevent mandible superimposing

200
Q

Describe how to position for VD mandible

A

Dorsal recumbency

Plate in mouth to prevent superimposition of skull

201
Q

Describe how to position for lateral pharynx

A

Lateral recumbency
Forelimbs pulled back towards chest
Pads under nose and neck to prevent rotation
Centre caudal to angle of mandible
Collimate to include nasopharynx, oropharynx and larynx

202
Q

What are the dangers involved in equine radiography?

A

Radiation

Conscious horse

203
Q

How is physical safety maintained in equine radiography?

A

Sedate horse unless very sensible, compliant but not too sleepy
Procedure done quickly and quietly with no sudden movement or noise
Always prepared to move if horse kicks

204
Q

Why is their more radiation danger associated with equine radiography?

A

Need lots of people in room to restrain

High exposure as thick tissue so lots of scatter

205
Q

What safety measures are in place for radiation for equine radiography?

A

Minimal personnel- one at head, one plate holder, one radiographer
Use PPE and dosimeters
Barrier behind horizontal beam
Cassette holder when possible

206
Q

How should you prepare horses for radiography?

A

Brush off mud (radiopaque)
Remove shoe
Pick out feet
Pack frog with same opacity as soft tissue

207
Q

What are the 4 standard views for equine radiography?

A

Dorsopalmer/plantar
Mediolateral/lateromedial
DLPMO/dorsal lateral palmer/plantermedial
DMPLO/dorsal medial palmer/plantar lateral

208
Q

What views are radiographed for horses foot?

A

Lateromedial
Dorsopalmer/plantar
60 degree dorsoproximal/palmarodistal oblique
45 degree palmaroproximo/palmardistal oblique

209
Q

What views are radiographed for horses fetlock?

A

4 standard views

210
Q

What views are radiographed for horses carpus?

A

4 standard views
Flexed to separate radial and intermediate carpal bones and see more joint surface
Can skyline dorsoproximal-dorsodistal obliques to shoe dorsal surface of each bone

211
Q

What views are radiographed for horses tarsus?

A

4 standard views

Can flex to see calcaneus and sustentaculum tali

212
Q

What views are radiographed for horses stifle?

A

Lateromedial

Caudocranial

213
Q

What views are radiographed for horses elbow/shoulder?

A

Mediolateral
Craniocaudal
Leg normally pulled forwards

214
Q

How are horses upper limbs and pelvis x-rayed and what are the limitations?

A

Lying with legs extended

Hard to view and produces lots of scatter as thick tissue

215
Q

What views are radiographed for horses thorax?

A 
4 images taken as too large for one image
Dorsocranial
Dorsocaudal
Ventrocranial
Ventrocaudal
216
Q

What views are radiographed for horses head?

A

Lateral
Dorsoventral
Obliques

217
Q

What are issues regarding equine ultrasounds?

A

Lots of hair
Thick skin
Dirty
Large so need low frequency which produces low image quality

218
Q

How are horses prepared for ultrasound?

A

Clipped
Lots of scrub
Spirit to degrease
Gel applied

219
Q

What are equine ultrasounds used for?

A

Musculoskeletal system

Abdomen

Clinical Nursing Jan exam (7 decks)

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