US physics

Question 1

What is axial resolution? What determines axial resolution?

Answer 1

• Axial resolution - ability to recognize two different objects at slightly different depths along beam axis
• Influenced by the spatial pulse length (i.e., shorter SPL = increased axial resolution)
  
  • Axial resolution = SPL / 2
  • SPL = wavelength x # of cycles
    
    • SPL is improved at higher frequency (shorter wavelength)

Question 2

What is lateral resolution? What influences lateral resolution?

Answer 2

• Lateral resolution - ability to distinguish objects that are side-by-side
• Depends on the beam width (i.e., smaller beam = better res)
  
  • Beam width is determined by:
    
    • Transducer frequency (higher freq = smaller width)
    • Focusing beam
    • Gain (decrease gain = smaller width)