Introduction to Advanced Imaging Flashcards
what are CT amd MRI images
tomographic imaging
produce slice of patient
avoids superimposition
what are the planes of imaging in CT and MRI
sagittal
dorsal
transverse
what is CT
computed tomography
ionizing radiation
shows slices
how does CT take an image
x-ray beam passes through patient and strikes detectors
x-ray tube and detectors rotate around patient
cross-sectional image generated
high-energy x-ray beam
what is back projection
measurement of total beam attenuation along path
measurement at multiple angles
gives final image
how is CT image displayed
tissue attenuation measured in Hounsfield Units (HU)
can adjust window centre and width to highlight different tissues
what are the uses of CT
lung and bony structures (resp and orthopaedic disease
3D reconstruction
higher resolution than convential radiography
what is MRI useful for
excellent for soft tissue (CNS)
how does MRI work
body placed in strong magnetic field with receiver coil
protons align with magnetic field
electromagnetic pulse moves protons from alignment with main field
as protons relax back to main field, change in signal is detected by receiver coil
image is generated
what are the two sequences of MRI
T1 and T2
different tissues have different relaxation properties –> image sequence can highlight different relaxation property, appearance depends on imaging sequence used
what are hypointense (dark) tissues on T1 weighted sequences
fluid
cortical bone
gas
what are isointense (grey) tissues on T1 weighted sequences
CNS
muscle
organs
what are hyperintense (white) tissues on T1 weighted sequences
fat
what are hypointense tissues on T2 weighted sequences
cortical bone
gas
what are isointense tissues on T2 weighted sequences
muscle
organs
CNS
white vs. grey matter
