Question

What is meant by the axial resolution of an ultrasound imaging system. What is it dependent on?  A 10 MHZ transducer is employed for a medical ultrasound scan.  The pulse duration is given as 0.3 micro sec.  

a)Sketch the shape of the pulse, indicating the number of oscillations.  

Answer 1

What is meant by the axial resolution of an ultrasound imaging system. What is it dependent on?

$\Rightarrow$ Axial resolution is determined by the length of ultrasound pulse. It is the minimum distance that can be differentiated between two reflectors located parallel to the direction of ultrasound beam.

Mathematically, we have

Axial resolution = (1/2) SPL

where, SPL = spatial pulse length

Axial resolution is high when the spatial pulse length is short. Higher the beam frequency, better the axial resolution.

Spatial pulse length is the product of the number of cycles in a pulse of ultrasound and the wavelength.

The wavelength of a pulse is determined by the operating frequency of a transducer. Transducers of high frequency have thin piezoelectric elements that generate pulses of short wavelength. The wavelength is equal to twice the thickness of an elements in a transducer.

(Pulse duration) = (Period) x (Number of cycles in pulse)

A 10 MHZ transducer is employed for a medical ultrasound scan. The pulse duration is given as 0.3 micro sec.  

(a) To sketch the shape of a pulse which can shown below as -