Chapter 8: Axial Resolution
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| What is resolution? | The ability to image accurately
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| What is Axial Resolution? | The ability of a system to display two structures that are close together
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| With axial resolution, where do the structures lie in relation to the sound beam's main axis? | The structures lie parallel to the sound beam's main axis one in front of the other
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| What are the units for axial resolution? | mm, any unit of distance
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| Axial resolution is determined by what? | Spatial Pulse Length; medium and sound
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| What is the relationship between axial resolution and spatial pulse length? | Shorter pules: better axial resolution
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| What is the mnemonic for the synonyms of axial resolution and what does it stand for. | LARRD: longitudinal, axial, range, radial, depth
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| Can axial resolution be adjusted by the tech? Why or why not? | no; because SPL is set by the TD
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| What are the typical values of axial resolution? | 0.1-1.0mm
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| What type of numeric value improves image accuracy for axial resolution? | Low numeric value
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| For best axial resolution, the pulse duration (PD) and SPL should by what? | short
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| What are the equations for SPL? | SPL = wavelength x # of cycles or
SPL = propagation speed/frequency x
# of cyles
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| What is the equation for axial resolution? | axial resolution(mm)=SPL(mm)/2 or
axial resolution(mm)=wavelength(mm)x #of cycles in pulse / 2
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| What is the equation for axial resolution in soft tissue? | axial resolution(mm)=0.77x #cycles in pulse / frequency (MHz)
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| What two things create shorter pulses that improve axial resolution? | Less ringing (dampen the crystal), higher frequency
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| When a crystal is dampened, how many cycles are in a pulse? | 2-3 cycles
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| How does a higher frequency improve axial resolution? | higher frequencies = shorter wavelength (with set medium)= shorter pulse
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| According to Kremkau, what is axial resolution and how does it run? | It is the ability to produce 2 distinct structures and it runs "along scan line"
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| What is the useful frequency range for ultrasound? | 2-15 MHz range
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| What happens when the frequency is less than 2MHz or more than 15MHz? | less than 2MHz = not acceptable axial resolution
more than 15MHz = not enough penetration depth
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| What are the two types of detail resolution? | axial and lateral resolution
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