Lec 13 - CT/MRI Imaging Flashcards
cone beam ct does not have nearly as much exposure as blank
medical ct
ct advantage is that it is a blank of information and NOT a standard blank
slice, shadow image
ct scans are often called CAT scans because it stands for blank
computed axial tomography
the geometry for Hounsfield’s original ct scanner used a blank beam
pencil
hounsfield found that a 2 or 3 dimensional object could be reproduced from a blank set of projections
infinite
blank from tomographic imaging are converted to 2D pixels so that data can be reconstructed into digital images
3D voxels
ct number shade of gray that is +1000
dense bone
ct number shade of gray that is 0
water
ct number shade of gray that is -1000
air
newer ct units have a ct number up to blank
+3000
spatial resolution is related to blank
pixel size
contrast resolution is related to blank
bit depth
high threshold will make everything look blank
black
3rd generation of ct design had x ray tube and detector moving on blank
different tracks
4th generation of ct design has blank moving but there was a stationary continuous ring of blank
x ray tube, detectors
to reduce effects of compton scattering in medical ct… each detector has blank… this is also important for control of blank
its own collimator, voxel length
artifacts in cone beam ct are from streaks from blank
high density materials like implants
3 types of tomography
mri, ct, pet
most common mri target
hydrogen nuclei
mri is best for blank
soft tissues
mri radio frequency pulse leads to blank
disalignment
mri recovery rates differ depending on the
tissue type
the protons are not perfectly aligned with the magnetic field and instead are blank (wobbling) which results in a blank frequency
precessing, resonant
weighted image that looks at fat and makes it bright
t1
weighted image that looks at water and makes it bright
t2
t1 has fat with the blank t1 relaxation time
shortest
t2 has water with the blank t2 relaxation time
longest
PET scans… when labeled molecules are metabolized, blank are released which produce blank
positrons, gamma rays
imaging of the salivary or ductal system that usually uses iodine
sialography
stone in salivary gland
sialolith
imaging that uses sound waves and is harmless
ultrasound
sound is not part of the blank spectrum
electromagnetic
ultrasound imaging uses blank MHz
2-15
sound travels blank in solids than in liquids or gas
faster
