ARDMS SPI Principles of Image Resolution 2

Question 1

Which factor primarily determines the lateral resolution of an ultrasound beam?

Accepted Answer

Beam width at the focal zone

Answer

Lateral resolution equals the beam width at any given depth, so it is best at the focal zone where the beam is narrowest.

Question 2

A transducer operating at 10 MHz will have _____ axial resolution compared to one operating at 5 MHz.

Accepted Answer

Better

Answer

Higher frequency produces shorter wavelengths and shorter pulses, improving axial resolution.

Question 3

Elevational (slice-thickness) resolution is primarily controlled by:

Accepted Answer

Fixed focus in the elevation plane

Answer

Most arrays cannot steer or focus electronically in the elevation plane, so slice thickness is fixed by the lens curvature.

Question 4

Increasing the number of focal zones in a linear array will:

Accepted Answer

Improve lateral resolution throughout the image at the cost of frame rate

Answer

Multiple transmit focal zones improve lateral resolution over more depths but require multiple firings, reducing frame rate.

Question 5

The spatial pulse length (SPL) is calculated as:

Accepted Answer

Number of cycles × wavelength

Answer

SPL = number of cycles × wavelength; shorter SPL yields better axial resolution.

ARDMS SPI - ARDMS Sonography Principles and Instrumentation Practice Test