Advanced Imaging Techniques Flashcards
what are the 3 main advanced imaging techniques?
computed tomography (CT) scintigraphy magnetic resonance imaging (MRI)
where are most advanced imaging modalities found?
at refurral centers
where are most advanced imaging modalities found?
at refurral centers
what is seen when using CT/MRI?
slices through the animal rather than 2D projections
what can be assessed by scintigraphy?
functional remodelling activity of bone
how is CT similar to MRI and US?
uses cross-sectional imaging
how is CT similar to radiography?
makes use of ionising radiation and many of the same principles
what is used to generate the image in CT?
x rays
what constraints is CT imaging under?
same as x ray
what happens to the room while CT is running?
locked and red light outside shows no entry
how does CT gain a 360 degree image?
uses rotating x ray machine and rotating detector which pass around the patient
where is the patient positioned during CT?
on a sliding table and is advanced through the gantry as the machine rotates
what is used to construct the data gained from CT into a slice or 3D image?
complicated computer programs which analyse information from all detectors
how are different tissues represented on CT?
as with radiography (bone - white, air - black)
what is CT windowing?
choice of how to display information / tissues depending on what you would like to view
what is each tissue assigned during CT?
Hounsfield unit?
what do Hounsfield units depend on?
attenuation of beam - how much of the X-ray beam reaches the detector as it passes through each tissue
what is CT window level and width chosen to optimise?
certain tissues so that they show up more than others
what structure is assigned Hounsfield number 0?
water
how can Hounsfield units be used to optimise an image?
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
what is a key benefit of CT windowing?
animal can be scanned once but image is reconstructed differently to show different desired tissues
what are the main uses of CT?
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
how long is CT scan time?
several seconds - longer than x ray
what restraint is needed for CT?
sedation or GA
what area of CT is particularly useful for orthopedic surgery?
can be used to create 3D models for surgical planning and custom made surgical implants
what are the disadvantages of CT?
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
what is CT useful for in the lung?
pathology
detection of metastatic disease
why is CT so good for detection of metastatic disease in the lungs?
detects nodules that are invisible on x-rays
what issue found with radiographs is avoided by CT?
superimposition of structures