S1_L2_MSKI - 1-4 Flashcards
who discovered CT
Godfrey Hounsfield
godfrey hounsfield’s CT was based on _
Work was based on Alan Cornack’s mathematical formulas for reconstruction of images for digital signals
t or f First scanners were dedicated to scanning the head
t
Primary purpose of CT was for _
imaging of the brain
what year when godfrey divocered CT
1972
Whole body scan was possible. in what year
1976
Hounsfield was awarded Nobel Prize in Medicine in _
1979
Hounsfield was awarded_in 1979
Nobel Prize in Medicine
t or f CT scan has different imaging principles as conventional radiography
f, Same imaging principles as conventional radiography
X-rays are _ by body tissues
attenuated
Radiodensities of the body tissues are represented in the image as shades of _
gray
_ of the body tissues are represented in the image as shades of gray
Radiodensities
CT creates images based on _(axial) slices, created by up to
_ projections
from different angles, unlike X-rays
cross-sectional, 1000 projections
3 ELEMENTS OF CT SCAN
GANTRY
OPERATOR’S CONSOLE
COMPUTERS
Into which the patient slides during the examination
GANTRY
gantry parts:
X-ray tube and the high-voltage generator
● Collimator Assembly
Detector Array
Data Acquisition
employs a high-intensity x-ray tube in order to provide uniform penetration of
the tissues and reduce attenuation
X-ray tube and the high-voltage generato
Aperture through which xrays pass
● Collimator Assembly
Controls radiation center
Collimator Assembly
Creates a narrow fan-shaped beam of
x-rays
Collimator Assembly
collimator assembly creates __ beam of xrays
narrow fan shaped
Measures the remnant radiation
● Detector Array
what determines the slice thickness
Collimator Assembly
Opposite X-Ray tube
● Detector Array
Up to how many detectors are arranged in an
array, encircling the patient
1000
Amplifies signal from the detectors in the
form of varying electrical current = analog
signal
● Data Acquisition
varying electrical current is called
analog signal
Will later on be converted into digital for
an image to be seen in the computer
● Data Acquisition
Converts analog to digital form
computer (data acquisition)
CT tech controls scanning process, selects slice thickness,
reconstruction algorithms (post-processing), and other specs
OPERATOR’S CONSOLE
Transforms radiant energy to something we are able to see
COMPUTERS
computers transform __ to somewthing we are able to see
radiant energy
MAKING THE CT IMAGE (2)
SCREENING PROCESS
DATA CONVERSION
Where transduction occurs
SCREENING PROCESS
2 Dimensional digital radiograph
SCOUT IMAGE
X-ray tube moves circumferentially around patient to get a “slice”
CT SCANNING
Will revolve _ degrees in the gantry
360
● Table moved for a new “slice” in what cuts for ct scanning
axial
movement of the tabletop is referred to in
terms of _
pitch
○ CT scan will revolve, stop, move, and go.
● Stop-and-go action
t or f For modern scanners they move continuously during the exam process
t
Modern scanners move continuously during the examination process -> what slices
helical
While the x-ray beam is moving around, _continuously goes on
scanning process
DATA CONVERSION (3)
matrix
image
post processing
Radiodensities are converting by the computer into a _
matrix
Each cell of the matrix is a _ (picture element).
pixel
Each pixel is assigned a shade of _,
which represents the _ of that cell of the matrix,
expressed in terms of _ units.
gray, radiodensity, hounsfiel
Matrix becomes an _ using a mathematical process called
image, “back projection”
the image of ct scan will perform what cuts
sagittal or coronal cuts
Image can be manipulated in the computer’s software
POST PROCESSSING
Improving contrast in __
post porcessing
Modifying the window can be done in _
post processing
DIFFERENT FORMS OF CT
THREE-DIMENSIONAL CT
CT MYELOGRAM
CONE BEAM CT
Multiplanar reconstruction
THREE-DIMENSIONAL CT
Imaged part can be rotated “in space” on the
computer screen
THREE-DIMENSIONAL CT
Invasive in nature -> inject a contrast
ct myelogram
Media into the subarachnoid space
ct myelogram
_ is better able to distinguish between osteophytes, ligament infolding,
and annular material than is MRI.
CT myelography
ct myelography is better able to distinguish between _, _,
and _ than is MRI.
osteophytes, ligament infolding, annular material
Best viewed in digital format than on printed
forma
THREE-DIMENSIONAL CT
t or f You can print out 3d images, but can’t be manipulated
t
in ct myelgram, where will you inject the media
subarachnoid space
Acquires all the data in a single sweep of the scanner
CONE BEAM CT
is not constructed from a large number of slices but rather
based on one volume of data.
CBCT scanner
cone beam ct is used mostly in _
drentistry
Uses a large, cone-shaped x-ray beam matched with a flat-panel detector
cone beam ct
cone beam ct is for imaging of the _
breast
○ For breast cancer detection
○ To check for malignant cells
cone beam ct
Tissues will have differing _
represented by different shades of _
radiodensities, gray
Dense structure in CT = what color
white or light shade of gray
Less dense in CT, what color
dark
tracheas and epiglottis will appear what color in CT
black
t or f Cortical bone is more dense than cancellous bone
t
cancellous bone sanwiched between cortical is called
flat bone
For axial cuts/images, images are viewed in a __
caudo-cephalad manner
For sagittal cuts, images are viewed from _
left to right
t or f Viewing adjacent slices may help orient you with the anatomy
t
in viewing ct images, concentrate only on 1 area t or f
f
CT scan slices are identified in terms of _ that correspond to _
slice
numbers, scout images
_ appears as a small locator image inserted into the image for each
slice (left uppermost corner)
Scout image
Selecting the range of radiodensities displayed in an image
WINDOWING
t or f CT is inable to choose the range of radiodensities displayed
f, CT has the ability to choose the range of radiodensities displayed
a CT image made for the purpose of viewing musculature,
soft tissues, or viscera
Soft tissue window
CT image for viewing of the bone
Bone window
Slice thickness for _
CT can vary from 0.5 to 2 mm (for small joints) to 2 to 3 mm (for the pelvis)
musculoskeltal CT
Slice thickness for musculoskeletal CT can vary from _(for small joints) to _
(for the pelvis)
0.5 to 2 mm, 2 to 3 mm
0.5 to 2 mm is for _
small joints
2 to 3 mm is for
pelvis
Thinner slices are typically used in areas of_
rapidly changing anatomy
Smaller bones or joints can be missed in
_ slices
thicker
CLINICAL USES OF CT SCAN
● Subtle fractures and/or complex fractures
Degenerative changes (spinal arthritic changes), spinal stenosis especially with CT myelography
Serious trauma since multiple injuries to both osseous and soft tissue structures can be determined
IV disc conditions when combined with
diskograms
Best for evaluation of loose bodies in a joint
Less time-consuming than MRI or UTZ
Accurate measurement of osseous alignment
Less expensive than MRI
Less problematic for claustrophobic patients
Comminuted fx: better seen with _
CT Scan
_ are like myelograms, you
inject the contrast to the disc.
Diskograms
ct scan is best for evaluation of __
loose bodies in a joint
UTZ is also fast, but it is _
operator-dependent.
MRI only takes _
45 mins - 1 hr long
At present, CT is the modality of choice for
detailed imaging of _ _
cortical and trabecular
bone.
Limited capability for determining the histological makeup of tissues for _
ct scan
Different tissues may have the similar
_ = difficult to differentiate
tissues
radiodensity
High radiation exposure (1000 projections) for MRI t or f
f, ct
