Special Imaging Flashcards
What does CT stand for?
Computerized Tomography
What is CT (computerized tomography) also known as?
Computerized axial tomography (CAT)
What does a CT scan do?
Diagnostic imaging procedure that uses x-rays to present a cross-sectional image “slices” of the body
What are the cross sections reconstructed from?
Measurements of Attenuation coefficients (this calculates the ability of x-rays to pass through tissues)
What calculates the ability of x-rays to pass through tissues or being weakened or _____ by the tissues?
Attenuation coefficients
- Attenuated
CT is based on what fundamental principle?
The density of tissue that is passed by the x-ray beam is able to be measured from a calculation of the attentuation coefficients!
T/F: The emitter of x-rays rotates around the patient and the detector, placed in diametrically same sides.
FALSE
- The emitter of x-rays rotates around the patient and the detector, placed in diametrically OPPOSITE sides
T/F: Unlike x-ray radiography, detectors of the CT scanner do not produce an image
TRUE
CT scanners will measure the transmission of a thin beam, how thin is it?
1-10mm slices
The image of the certain section being imaged is taken from different angles, which allows the information to be viewed at a certain depth…. what depth is this? (i.e. 1-d, 2-d, 3-d)
3-dimension
T/F: CT scanning allows you to view body sections in all available planes and three dimensional imaging.
TRUE
What is each square in the image matrix called?
Pixel
What is the tiny elongated block of tissue known as?
Voxel
T/F: The size of the pixel was not determined by the computer program, but determined by the dimensions of the x-ray beam.
FALSE
- The size of pixel was determined by the computer program and NOT by the dimensions of x-ray beam
T/F: CT slice thickness is determined by computer programming and not the x-rays themselves.
TRUE
What are the units used in CT scans?
- Hounsfield units (HU)
- These are determined by the intensity of x-ray attenuation coefficient in tissues of different densities that can be a reliable measure of different compositions of body tissues
In HU, what are the measurements of Air, Fat, Water, Compact bone…
Air = -1000HU
Fat = -60 to -120 HU
Water = 0 HU
Compact Bone = + 1000 HU
Who pioneered the CT scan?
Sir Godfrey Hounsfield - Nobel Prize in 1979
Clinical application and indication for CT scanning?
- Head/Neck Pathology + paranasal sinuses
- CTA-CT angiography
- Chest and abdomen
- Imaging of acute trauma: fractures/dislocations
- CT is also used if MRI or other imaging is contraindicated
- Note: CT axial slices are modality of choice for investigating head trauma and cerebrovascular events (stroke)
Neck Ct+C is used in the diagnosis or what?
Lymphoma and Head/Neck Neoplasms
T/F: For cervical and other skeletal trauma CT imaging w/o contrast is the modality of choice especially if plain radiographs are unrewarding or require further special imaging.
TRUE
- ex. sagittal reconstruction of a cervical spine CT showing flexion teardrop fracture at C5
Correct ID of various radiographic densities referring to HU scale will help with accurate diagnosis and clinical management. If looking at a axial cut of a liver, what could one find?
Lipoma within the liver
What does MRI stand for?
Magnetic Resonance Imaging
T/F: Like CT an MRI helps look at the body within different planes.
TRUE
