Data Acquisition (4) Flashcards
Inputs (2)
“Data Acquisition”
All the physical/technical parameters that go into creating scan data
Processing (2)
“Reconstruction”
Series of events used to transform inputs to useful image information
Outputs (3)
“Image Display”
Processed data that’s displayed as pixels within a matrix
Various manipulation possibilities
X-plane
Extends horizontally across scanner
(Right vs Left)
Y-axis
Extends vertically across scanner
(Ant vs Post)
Z-plane
Extends longitudinally thru scanner
(Sup vs Inf)
Which axis of any given voxel represents the specific slice
z-axis
SFOV
Scan Field of View
Entire area inside scanner that’s actually being scanned
DFOV (2)
Display Field of View
Just the area processed for viewing
Set by tech based on localizer image
Iso-center
Exact center of scanner representing mid-point of x- / y-axes
Ideal midpoint of patient anatomy to ensure equal exposure in all directions
Sequential Scanning
“Axial” scanning
Spiral Scanning
“Helical” CT
Helical Scan Benefits (2)
Decreased scan time: shorter breath holds, greater comfort
Better visualization of contrast before it dissipates into blood stream/is excreted
IV contrast will fill vasculatrue of chest within _______ and be nearly gone within ________
30sec
60sec
Volume scanning is only possible with detector arrays containing at least _______
250 rows (must be at least as large as organ being scanned)
Major benefit of volume scanning (2)
Rapid Scan
Minimal Motion
Rotation Time
Time required for single tube rotation (around patient)
Acquisition Thickness (3)
Thickness of each detector row
Can be “functionally” combined to increase acquisition rate (decrease scan time)
Limiting factor for reconstruction thickness
Partial Volume Averaging
Loss of tissue visibility when different tissue types are averaged together w/in a slice and displayed with same HU
If pitch is < 1 there is _______ in the helix and the scanner gets _______ views resulting in a very ________ (speed) scan with very ________ resolution
Overlap
Extra
Slow
High
If the pitch is > 1 there are _______ views, resulting in a _______ (speed) scan with _______ resolution
Missing
Faster
Lower
Table Movement (per rotation) Formula
Beam Width x Pitch
Pitch applies only to _________ scanning
Helical
Pitch is a ratio describing:
The distance the table moves : the beam width
Pitch Calculation:
Table Movement/Beam Width
When pitch is > 1 _________ begin to appear
Gaps in information
