Advanced Imaging Techniques

Question 1

what are the 3 main advanced imaging techniques?

Answer 1

computed tomography (CT)
scintigraphy
magnetic resonance imaging (MRI)

Question 2

where are most advanced imaging modalities found?

Answer 2

at refurral centers

Question 3

where are most advanced imaging modalities found?

Answer 3

at refurral centers

Question 4

what is seen when using CT/MRI?

Answer 4

slices through the animal rather than 2D projections

Question 5

what can be assessed by scintigraphy?

Answer 5

functional remodelling activity of bone

Question 6

how is CT similar to MRI and US?

Answer 6

uses cross-sectional imaging

Question 7

how is CT similar to radiography?

Answer 7

makes use of ionising radiation and many of the same principles

Question 8

what is used to generate the image in CT?

Answer 8

x rays

Question 9

what constraints is CT imaging under?

Answer 9

same as x ray

Question 10

what happens to the room while CT is running?

Answer 10

locked and red light outside shows no entry

Question 11

how does CT gain a 360 degree image?

Answer 11

uses rotating x ray machine and rotating detector which pass around the patient

Question 12

where is the patient positioned during CT?

Answer 12

on a sliding table and is advanced through the gantry as the machine rotates

Question 13

what is used to construct the data gained from CT into a slice or 3D image?

Answer 13

complicated computer programs which analyse information from all detectors

Question 14

how are different tissues represented on CT?

Answer 14

as with radiography (bone - white, air - black)

Question 15

what is CT windowing?

Answer 15

choice of how to display information / tissues depending on what you would like to view

Question 16

what is each tissue assigned during CT?

Answer 16

Hounsfield unit?

Question 17

what do Hounsfield units depend on?

Answer 17

attenuation of beam - how much of the X-ray beam reaches the detector as it passes through each tissue

Question 18

what is CT window level and width chosen to optimise?

Answer 18

certain tissues so that they show up more than others

Question 19

what structure is assigned Hounsfield number 0?

Answer 19

water

Question 20

how can Hounsfield units be used to optimise an image?

Answer 20

assigned to all tissues - area of interest (e.g. bone/brain) has range of HU and visible shades of grey are placed assigned to these values so differences in tissue density will be shown

Question 21

what is a key benefit of CT windowing?

Answer 21

animal can be scanned once but image is reconstructed differently to show different desired tissues

Question 22

what are the main uses of CT?

Answer 22

good bone detail
used in soft tissue particularly with contrast
scanning time is shorter than MRI so can be used for studies of thorax as respiration is not an issue

Question 23

how long is CT scan time?

Answer 23

several seconds - longer than x ray

Question 24

what restraint is needed for CT?

Answer 24

sedation or GA

Question 25

what area of CT is particularly useful for orthopedic surgery?

Answer 25

can be used to create 3D models for surgical planning and custom made surgical implants

Question 26

what are the disadvantages of CT?

Answer 26

limited availability in general practice expensive (although cheaper than MRI) scan time is several seconds - slower than x ray uses ionising radiation in higher patient doses than radiography due to length of scan rime

Question 27

what is CT useful for in the lung?

Answer 27

pathology | detection of metastatic disease

Question 28

why is CT so good for detection of metastatic disease in the lungs?

Answer 28

detects nodules that are invisible on x-rays

Question 29

what issue found with radiographs is avoided by CT?

Answer 29

superimposition of structures

Question 30

what aspect of CT facilitates surgical planning?

Answer 30

3D reconstruction and rotation to view all aspects

Question 31

what CT imaging can be performed in horses?

Answer 31

extremities and head

Question 32

what is used as the source of IR during scintigraphy?

Answer 32

radioisotope

Question 33

what is the most common radioisotope used for scintigraphy?

Answer 33

technetium 99

Question 34

what determines where in the body the radioisotope will localise?

Answer 34

the substance it is bound to which will bind to a certain tissue in the body

Question 35

where si increased binding of the radioisotope found?

Answer 35

within the target tissue where there is increased metabolism

Question 36

what is the most common substance used to bind radioisotope to bone?

Answer 36

HDP

Question 37

how does the bound isotope reach its site of binding?

Answer 37

IV injection into patient

Question 38

how long must be allowed for the isotope to reach the tissue of interest?

Answer 38

~3 hours

Question 39

how is scintigraphy scan performed?

Answer 39

gamma camera used to measure pattern of radiation emitted from the patient

Question 40

what restraint is used for scintigraphy?

Answer 40

sedation in cats as short scan time | standing sedation in horses - must be able to stand

Question 41

what are the uses of scintigraphy?

Answer 41

detection of skeletal injury in horses | detection of thyroid nodules (especially ectopic nodules) in cats

Question 42

where is scintigraphy useful in detection of skeletal injury in horses?

Answer 42

areas that are difficult to radiograph lesions not detectable radiographically cases where it is difficult to localise lameness source

Question 43

what areas of a horse may be difficult to radiograph?

Answer 43

pelvis/spine - due to thickness so more scatter produced and lower qualty image

Question 44

what is an example of a lesion that may be undetectable radiographically but would show on scintigraphy?

Answer 44

stress fractures

Question 45

what are the advantages of scintigraphy?

Answer 45

``` increasing availability (particularly in equine practice) functional assessment as uptake of bound isotope depends on metabolism / activity ```

Question 46

what are the disadvantages of scintigraphy?

Answer 46

uses IR radiation so same risks to operator and patient as x rays patient remains radioactive for sometime afterwards poor anatomical detail so can be difficult to interpret images additional legislation applies (EA) for licence to use and disposal

Question 47

how long will the patient remain radioactive after tachnetium is used?

Answer 47

48 hours

Question 48

what images are produced during MRI?

Answer 48

cross sectional images in different planes

Question 49

what causes a nucleus to spin?

Answer 49

if there is an odd number of protons and/or an odd number of neutrons

Question 50

what is created by the spinning electrical charge of an unbalanced atom?

Answer 50

a mini magnetic field

Question 51

how many protons are found within 1ml of water?

Answer 51

6x10^22

Question 52

what happens to the random proton rotation within a patient when they are placed in a strong magnetic field?

Answer 52

the magnetic moments of the spinning nuclei line up with the magnetic field they have been placed in

Question 53

what is the strength of the magnetic field in a typical high field machine?

Answer 53

1.5 tesla

Question 54

how is an image aquired during MRI?

Answer 54

patient placed in a strong magnetic field so that atoms all spin the same way patient is then bombarded with radiowaves which cause the nuclei to become disorientated and emit a radio signal themselves when the waves stop the nuclei realign themselves detection and analysis of the radio signals emitted by the patient gives information about the chemical composition of the tissues

Question 55

what does appearance of tissues on MRI depend on?

Answer 55

timing of pulses (inputs of radiowaves) and echoes (signals from tissue)

Question 56

what does the timing of radiowaves depend on?

Answer 56

tissue environment

Question 57

what does the computer reconstruction of information received from MRI machine result in?

Answer 57

cross sectional images through the patient

Question 58

what are the advantages of MRI?

Answer 58

good contrast resolution - excellent anatomical detail doesn't use ionising radiation - non damaging long term accurate assessment of extent of the spread of a lesion

Question 59

what lesions can be assessed with MRI?

Answer 59

retrotubular nasal pelvic masses

Question 60

what are the main uses of MRI?

Answer 60

neurology - spine and brain soft tissue lesions bone marrow oedema (not great with bone itself)

Question 61

what are the disadvantages of MRI?

Answer 61

not widely available in practice expensive (installation and maintenance) animals must be under GA safety hazard caused by magnet - no metallic objects around

Question 62

why must all animals be under GA when having an MRI scan?

Answer 62

MRI sequence takes time and must remain perfectly still throughout

Question 63

why must metal objects not be taken into MRI?

Answer 63

large permanent magnet

Question 64

what equipment used in MRI must be MRI compatible?

Answer 64

tables oxygen cylinders anaesthetic machine monitoring equipment

Question 65

should animals with pacemakers have an MRI?

Answer 65

no

Question 66

what must you take care with when the patient is having an MRI?

Answer 66

any implants - particularly new - as they may shift due to magnet

Question 67

what artefact may be produced during MRI?

Answer 67

distortion of magnetic field around microchip site leading to altered image

Question 68

how does MRI used during equine standing MRI differ from normal MRI?

Answer 68

similar technology lower field smaller magnet

Question 69

what part of the equine limb can be imaged using standing MRI?

Answer 69

distal only

Question 70

what is equine standing MRI useful for?

Answer 70

examining soft tissues within the hoof capsule

Question 71

what must be placed prior to equine standing MRI?

Answer 71

IV catheter

Question 72

what sedation level is equine standing MRI performed under?

Answer 72

standing

Question 73

who is usually in charge of acquiring images and sedation during equine standing MRI?

Answer 73

nurse