Chapter 6-9 quiz Flashcards
What is the region from the transducer to the smallest cross-sectional area of a sound beam called?
Near zone
The area that starts at the beam’s smallest diameter and extends deeper is:
The Fraunhofer zone
What is the point or location where a beam reaches it smallest dimension?
Focus
All of the following are true of the focus except:
It is at the start of the fresnel zone
Two ultrasound systems are identical except for the PRP of the emitted pulse. Which system will have the deeper focus?
Their foci will be at the same depth
For a disc shaped PZT crystal producing continuous sound, which design will create a beam with the shallowest focus?
Small diameter, low frequency
For a disc shaped PZT crystal producing continuous sound, which design will create a beam with the deepest focus?
Large diameter, high frequency
As sound travels deeply into the far zone, the beam diverges, or spreads out. Which of the following will result in a minimum beam divergence deep in the far zone?
High frequency, large diameter
As sound travels deeply into the far zone, the beam diverges, or spreads out. Which of the following will result in the greatest beam divergence deep in the far zone?
Low frequency, small diameter
All of the following terms describes the shape of a sound wave created by a tiny fragment of PZT except:
Hourglass shape
Huygens’ principle is based on ____
Interference
Which of the following explains the difference in sound beam shape created by a disc-shaped crystal from that of a small chip of PZT?
Huygen’s principle
Two ultrasound systems are identical except for the diameter of the transducer’s piezoelectric crystal. Which system has the deepest focus?
The one with the larger diameter crystal
In which region of a sound beam is focusing most effective?
The end of the near zone
The focus of an ultrasound beam is the location where the _______.
Optimum transverse resolution is
T or F? In comparison to other locations along the length of an ultrasound beam, focusing is generally ineffective in the far zone.
True
In an imaging transducer, what is the purpose of attaching the backing material to the PZT?
Improve image quality
Which component of an ultrasound system is made of lead zirconate titanate?
Transducer’s active element
T or F. The purpose of the backing material of an ultrasound transducer is to shorten the pulses, thereby creating images with better image quality.
True
Which component of an ultrasound transducer is made from a slab of epoxy embedded with tungsten?
The damping material
How thick is the active element of a 3MHz pulsed wave transducer?
Half the wavelength of the sound wave in the PZT
The PZT crystal of a transducer typically has a impedance higher that the impedance of the skin?
True
Which of the following lists orders the impedance from highest to lowest?
PZT, matching layer, gel, and skin
What is the thickness of the matching layer of a 2 MHz pulsed wave transducer?
One-quarter the wavelength of sound in matching layer
