Imaging Technologies Flashcards
What is a Digital Image?
- Digital images are acquired by an imaging device
- Overlay a grid, assign a number (usually an integer)
to each grid position
what are pixels
Pixels (picture elements) are the grid elements
what is image resolution
Image resolution / matrix size / pixel count is often used to refer to the number of pixels along each axis
what is Intensity/grey-scale
the number for a
pixel
what is Intensity/grey-scale resolution
the range of possible intensity values
what is spatial resolution
a measure of the smallest discernible detail in an image
In 3-D images, the pixels are known as what
voxels (volume elements)
Pixel/voxel size normally specified in
mm
what is the most common image file format for medical imaging
DICOM (Digital Imaging and Communications in
Medicine)
^ its a non compressed file format
what file format should not be used to store medical images?
Normally lossy compression file formats should
not be used to store medical images
what are 2 types of visualisation techniques in medical imaging
How can you differentiate between an MRI scan and a CT scan ?
if you are able to see bone in the image it is a CT scan
if the bone is missing it is an MRI
How do ultrasound machines work ?
an ultrasound wave is sent through the patient
the wave is reflected
the time taken between emitting a pulse and recieving a repsonse tells us how far away the boundry is
How does MRI imaging work ?
the patient enters the tube and they are irradiated with radio waves
the body then re emits those waves
the re emitted signals are localised using the magentic field and an image is produced
How is radioactive nuclear imaging used to detect cancer ?
cancer has inc blood flow
this means areas in the body where there is cancer, there will be increased uptake of the radioactive isotope
these areas will glow up on the image showing the presence of cancer
What are the 3 components of an MR scanner ?
magnet
gradient coils (electromagnets)
RF coils (radiofrequency)
What are the 5 radiographic densities that are available on X rays ?
air
fat
soft tissue
bone
metal
What 2 contrast agents is used for CT ?
iodine
barium
What contrast agents are used in MRI ?
Gadolinium
What is a disadvantage of X- rays ?
it is not very good at being able to distingush between different types of soft tissues
What is CT imaging ?
uses x-rays to create a 3d rendering
the x ray rotates around the patient to get a 180 degree view
What is the most common Beta+ (positron) emmiter given for medical imaging ?
F-18
It is given as FDG (fluorodeoxyglucose)
half life of 110 min
What pure gamma emitter is used for medical imaging ?
Tc-99m
half life of 110min
Which 2 types of ionising radiation are the most useful for medical imaging and why ?
positrons
gamma rays
they are able to penetrate the body but also leave the body so they can be detected to create an image
