Upload
maxim-oldham
View
219
Download
0
Tags:
Embed Size (px)
Citation preview
US PRACTICAL
*NEAR ZONE is the nearest area to the transducer & it always has the same diameter
of the transducer, BUT if the transducer :
Linear the near zone length is long (Deeper) .
Concave the near zone length is short .
*FAR ZONE is the farthest area from the transducer .
Focal zone: is amethod of focusing the U/S beam by Concentrating the acoustic energy
over a small area at Specific distance from the transducer . WE CAN MAKE THE
FOUCSE BY TWO WAYS :
1 )Concave crystal .2 )Acoustic lens .
RESOLUTION:We have four different types of resolution: spatial,
contrast, temporal, and energy resolution .
*Spatial resolution : It is the ability to image small or high contrast objects .E.g., the best spatial resolution found in Mammogram .
*Contrast resolution : It is the ability to distinguish one similar tissue from
another .E.g., the best contrast resolution found in MRI .
*Temporal resolution:It is the ability to measure & count motion. E.g., the best temporal resolution found in US "Doppler".* Energy resolution:It is the ability to measure & count energy.E.g., the best energy resolution found in NM. N.B.We consider all the resolution types in US EXCEPT Energy resolution.
WE HAVE TWO TYPES OF
:SPATIAL RESOLUTION(1) Axial
(2) lateral
AXIAL SPATIAL RESOLUTION :
it could also call range, depth or longitudinal .
It is the ability to distinguish between two objects close to each other & located along the main axis
. Factors affecting axial spatial resolution are :
1 )Spatial pulse length "if SPL increase, ASR will decrease"
2 )Frequency "if freq. increase, ASR & penetration decrease"
3 )pulse duration“ if PP increase, ASR will decrease
4 )Damping material has an affect also, "how quickly a pulse of US can be initiated &
extinguished.5 )Distance between 2 reflectors “ more D,
more ASR
*LATERAL SPATIAL RESOLUTION:It could also call transverse or asemouthal.It is the ability to distinguish between two objects close to each other & located perpendicular on the main axis.
Factors affecting lateral spatial resolution are:1) Size (crystal diameter) "smaller diameter, more LSR"2) Beam width 3) Frequency " more freq, more LSR" 4) Distance between 2 reflectors" more
D, more ASR"