Diagnostic Imaging Flashcards
what does CT stand for?
computed tomography
how does a CT scanner work?
- uses an x-ray tube mounted opposite a detector which emits x-rays in a fan shape that pass through the patient to reach the detector
- x-ray tube moves around the patient
what are the pros of a CT scan?
- detailed image quality
- automatically digitised
- tissue contrast greater and defined
- fluid and solid tissue can be distinguished
- internal structure of soft tissue is more detailed
what is the hounsfied unit for water, bone and air?
Water - 0
bone - 3000
air - -1000
what is the relation between a high housfied number and attenuation?
high number, white, increased attenuation
what is the relation between a low housfied number and attenuation?
low number, black, decreased attenuation
what is attenuation?
the reduction of the intensity of an x-ray beam as it transverses matter
what is a consideration to a CT scan?
- patients will need to be anaesthetised or heavily sedated
what can you use a CT scan for?
- images of the skull, lungs, brain, spine
- thoracic and abdominal masses
- can detect metastases
- useful for demonstrating size and position of tumours
What is fluroscopy?
an imaging technique that uses x-rays to obtain real time moving images of the interior of an object
what colours do soft tissue and bone appear during a fluroscopy?
- soft tissue - white
- bone - black
what is a con of fluroscopy?
higher radiation due to continuous exposure
how does an MRI scan work?
- magnets change alignment of the protons of hydrogen atoms in the body
- radio waves disorientate the protons so they move around
- protons give off signals when they return to original position
what does MRI stand for?
Magnetic Resonance Imaging
what is an MRI scanner used for?
- used to map location of protons in the body tissues
- soft tissue images
- moving areas such as heart and lungs
what are some cons of an MRI scan?
- patient must be anaesthetised
- can be up to an hour
- danger with metal objects
what is the unit of measurement used in MRI’s called?
TESLA
what is a pro of an MRI scan?
does not use ionising radiation
what is nuclear scintigraphy?
- involves the use of a radioactive isotope which are injected into the patient
- when these decay they release gamma radiation
- this can be scanned and forms a 2D image
- have to be isolated for at least 24hrs
what can nuclear scintigraphy be used for?
- equine orthopaedics
- thyroid cats
what law governs nuclear scintigraphy?
The Radioactive Substance Act 1993
what is ultrasonography?
uses sound waves to provide an image
what can ultrasonography be used for?
to complement radiography
what is a pro of ultrasonography?
can be performed conscious
what is a con of ultrasonography?
requires clipping of hair
what does white image do in terms of ultrasonography?
- reflects all sound waves
- bone or gas
what does black image do in terms of ultrasonography?
- lets sound pass through
- fluid
what does grey image do in terms of ultrasonography?
- reflects some, lets some through
- soft tissue and fat
why do we use ultrasound?
- highlight differences between fluid and soft tissue
- shows internal architecture of soft tissue
- real time moving picture
what are some advantages of ultrasound?
- painless
- non invasive
- short notice
- conscious
what are some disadvantages of ultrasound?
- doesn’t penetrate bone or air
- difficult to master
what are the two types of tranducer?
- linear array transducer
- sector scanner transducer
