Chapters 13-17 Flashcards
(45 cards)
What is harmonics?
multiples of the transducer frequency
Where are harmonics created?
In the tissues
What creates harmonics?
non-linear behavior
Where does sound move slightly faster?
in regions of compression (higher pressure)
where does sound travel slightly slower?
in regions of rarefraction (lower pressure)
what is the major disadvantage of pulse invertion imaging?
the frame rate is half that of fundamental imaging
What does pulse inversion do?
degrades temporal resolution while improving spatial resolution
What is brightness related to?
the brilliance of an image
What does contrast determine?
the range of brilliancies that are displayed (Bistable images are high contrast)
Analog (real world)
a variable attains a continuum of values
what is a pixel?
the smallest element of a digital picture
what does pixel density improve?
spatial or detail resolution
what is spatial resolution related to?
the number of lines per frame (more lines, better spatial resolution)
what do more bits per pixel give you?
more shades of gray and more contrast resolution
what is a byte?
a group of 8 bits
preprocessing
TGC, log compression, write magnification, fill-in interpolation, persistance, spatial compounding
how can write magnification improve temporal resolution?
if imaging is shallower
fill in interpolation improves what?
spatial or detail resolution
how is artifact created?
by the interference effects of scattered sounds, both constructive and destructive
how are scan lines steered?
by the transducer in different directions or views
dynamic apeture
optimizes lateral resolution @ all depths
edge enhancement
increases the contrast @ a boundary; ideally suited to distinguish interfaces
where does coded excitation take place
in the pulser
rendering
creates an element of realism to a 3D or 4D image
