Describing Sound and Pulsed Waves
Resolution and Image Formation
Transducers and 2D Imaging
Artifacts
Display and Image Processing
100
This happens when sound beams arrive at the same location at exactly the same time.
What is interference?
100
This type of resolution is improved by using higher frequency transducers.
What is axial resolution?
100
This material is bonded to the back of the active element and reduces the "ringing" of the PZT.
What is backing material?
100
This common artifact appears as multiple equally spaced lines located parallel to the sound beam's main axis.
What is reverberation?
100
This is the manipulation of image data after storage in the scan converter. It is controlled by the sonographer.
What is postprocessing?
200
This is the highest value a wave reaches from its baseline.
What is amplitude?
200
This type of resolution improves with a smaller beam width.
What is lateral resolution?
200
This transducer type electronically steers and focuses the beam using many small disc-like elements. If a PZT is damaged it will cause a horizontal band of drop-out on the image.
What is an annular phased array transducer?
200
This artifact is created when a sound pulse changes direction during transmission producing a second copy of the reflector side by side at the same depth of the true reflector.
What is refraction?
200
This type of magnification is applied during data acquisition before storage in the scan converter. It creates a new image with increased spatial resolution.
What is write magnification?
300
These two characteristics of a medium determine the speed of sound in that particular medium.
What are stiffness and density?
300
This relationship describes how crystal diameter and beam divergence are related. For example, a smaller diameter crystal produce beams that diverge more.
What is inversely related?
300
A process that reduces the strength of side and grating lobes by altering the electrical spike voltage in the transducer.
What is apodization?
300
This is an example of this type of artifact.
What is mirror image?
300
This method improves image quality by creating very long sound pulses with a wide range of frequencies in the pulser.
What is coded excitation?
400
This pulse waved parameter is the time from the start of a pulse to the start of the next pulse. It is the reciprocal of pulse repetition frequency.
What is pulse repetition period?
400
This type of resolution describes distinguishing structures that lie above or below the imaging slice.
What is elevational or slice thickness resolution?
400
This firing pattern steers the beam of a linear phased array transducer to the left or the right.
What is electronic slope?
400
This artifact occurs when sound waves propagate through a medium at a speed other than 1,540 m/s causing reflectors to appear at incorrect depths.
What is speed error?
400
This is used when gaps exist between scan lines. It is a prediction based on actual data that surrounds the gaps.
What is fill-in interpolation?
500
This type of wave requires a medium to travel; it is how ultrasound propagates.
What is a mechanical, longitudinal wave.
500
This is the location of the sound beam where the beam diameter equals the diameter of the transducer in the far field.
What is two near zone lengths?
500
A technique used by modern transducers that is designed to keep the sound beam narrow over a substantial depth range which optimizes lateral resolution.
What is dynamic aperture?
500
Reflections from above or below the assumed imaging plane can appear in an image due to this artifact.
What is slice thickness artifact?
500
This is an image processing technique that displays information from older images and superimposes the previous frames on the most current frame reducing noise on the image.
What is temporal compounding or persistence?