Alternate imaging modalities Flashcards
An imaging technique commonly used to obtain real-time moving radiographic images of the internal structures.
fluoroscopy
What kind of grey scale does fluoroscopy use?
inverted grey scale
High attenuation=Black
low attenuation=white
An imaging technique which has cross sectional imaging using a slice, has no superimposition and can create 3D images
CT
How does CT create and image?
X-ray tube spins around patient and the detectors determine amount of radiation absorbed by the patient, new spiral slicing allows for continuation of movement of the tube some, scanners even have multiple rows of detectors
A picture element and have only 2 dimensions.
pixel
A volume picture element and has three dimensions.
Voxel
In CT what constitutes to better resolution but a higher amount of radiation?
thickness of voxel slice (want thin slices)
All dimensions are equal and allows for multi-planar reconstructions and volume rendering without loss of resolution.
isotopic voxel
The range of HU represented on a specific image.
window
The central value of HU displayed.
level
hyper attenuating (CT)
white, highest HU (Bone, metal)
hypo attenuating (CT)
black, lowest HU values (Air)
What are some advantages of CT?
-more detailed view without superimposition
-faster and less expensive then MRI
what are some disadvantages of CT?
radiation exposure
more expensive than radiographs
poor soft tissue contrast
Which imaging techniques uses magnets?
MRI
What is the process of image formation for MRI?
Atoms with an odd number of protons possess a magnetic moment, hydrogen atoms have only 1 proton and act like tiny magnets, our protons will align with the magnetic field of the electromagnet some line up in the direction of the magnetic field while others will line up in the opposite direction some H atoms in opposite directions will cancel eachother out, a radiofrequency coil then applies energy which causes the non canceled out H atoms to flip direction, after a short period the pulse is stopped and the energy released from the H atoms are received by a coil
Weighting is then used to optimize the differences in relaxation rates of different tissues in order to provide contrast in the image
The use of certain parameters to optimize the differences in relaxation rates of different tissues in order to provide contrast in the image.
Weighting
hypointense (MRI)
less bright then the tissue you compare to
hyperintesne
brighter than the tissue you compare to
isointense
same brightness as the tissue you compare to
T1 weighted
fluid is hypointense (Black)
fat is hyperintense (white)
T2 weighted
fluid is hyperintense (white)
solid tissue is hypointese (black)
What is an advantage of using MRI?
better soft tissue contrast and noninvasive
Which imaging technique uses sound wave frequency higher than humans can hear?
US
