Module 2 Physics Flashcards
What happens with a longer impulse response
longer resonation –> longer impulse response –> more cycles in a pulse –> longer SPL = decrease axial res
What is the size of the matching layer
About half the wavelegnth leaving the tx
What is the purpose of the matching layer
to reduce the amount of reflection from crystals to the medium. Improve sound transmission
Why is purewave better than PZT?
- gives a near perfect polarization
-PZT is only about 70%
this improves efficiency, sensitivity, penetration, and image quality
wider BW with improved sensitivity
Bandwidth calculation
max frequency - min frequenct
Fractional BW calculation
BW/operating freq (centre freq)
What is Huygen’s Principle?
- That each crystal produces its own wavelet whcih come together to form a single wavefront (a sound beam per SL)
What is the NZL formula?
NZL = D^2 x freq divided by 6
What causes an increase in NZL
increases with aperature (number of crystals) and frequency
Increases when focal point is farther away
Where is the best resolution on an ultrasound scree?
Just shallow/just before the focal point - this is why we put the focus just below the area of interest
What type of resolution is improved at the focal zone?
lateral and contrast resolution is improved
What type of resolution is related to the width plane of the beam? How do you change this?
This is aka lateral plane/azimuthal/transverse. This is related to lateral resolution which changes with the focal point (we change this)
What type of resolution is related to the thickness plane? How do we change this?
elevational plane so elevational resolution. This is fixed we cant change this but it is related to artifacts (PVA)
What type of resolution is related to the length plane? How do we change this?
AKA the axial plane and effects axial resolution - related to SPL - can be changed by frequency
Band width ____ at the focal zone
decreases
