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"