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Two dimens. imaging
Chapter 12 Edelman
| Question | Answer |
|---|---|
| What type of image does a mechanical scanner produce? | Sector shaped images |
| How many active elements are in a mechanical scanner? | One |
| What type of image does a linear phased array scanner produce? | Sector shaped images |
| How many active elements are in a phased array scanner? | Many |
| What type of image does a linear sequential scanner produce? | Rectangular, and never wider than the transducer |
| Which has a smaller acoustic footprint, linear phased arrays or linear sequential arrays? | Linear phased arrays |
| With linear sequential arrays, how many crystals are fired at a time to create a sound beam? | A small group of crystals |
| A curved active element is what type of focus? | Internal |
| Placing a lens in front of the active element is what type of focus? | External |
| Can linear sequential array transducers steer sound beams electronically? | Yes, forming a parallelogram shaped image |
| True or false: the sound beams transmitted from a convex or curved array are parrallel to each other like a sequential array? | False, they are arranged in an arc |
| What type of image does a convex, curved or curvilinear scanner produce? | Blunted sector shaped images |
| True or false: vector array transducers are a combination of linear sequential and linear phased array technologies | True |
| What type of image does a vector array produce? | Trapezoidal |
| Which type of transducer when the active element is damaged has no loss of image or drop-out, but has eratic steering and focusing? | Phased array |
| Which two types of transducers have mechanical steering? | Mechanical and annular phased |
| What are the three types of resolution in imaging? | Axial, lateral and slice thickness or elevational resolution |
| True or false: Disc shaped crystals found in mechanical and annular phased arrays produce the best elevational resolution. | True |
| True or false: 4-D imaging refers to real time 3-D imaging. | True. It's a 3-D image with motion. |
| Three dimensional data acquired during an US using a 2-D probe creates an image. What word describes this action? | Rendering |
| True or false: Side lobes and grating lobes create artifacts, degrade lateral resolution, and reduce image quality. | True |
| Reducing the strength of side and grating lobes can be achieved through a process called what? | Apodization |
| True or false: grating lobes can be eliminated if the strength of the electrical spikes differs from element to element in the probe. | True, this is called apodization. |
| When the US system changes the number of active elements used along the face of the probe, this is called what? | Variable aperture or dynamic aperture |
| Modern tranducers are called what? | Arrays |
| Mechanical transducers have what type of a focal depth? | Fixed focus or conventional or mechanical focus |
| In a phased array transducer, the sound beams are steered rather than the crystal being mechanically moved. This electronic steering is called what? | Phasing |
| True or false, phased array always means "adjustable" or "mulit-focus." | True |
| The line of electrical signals that excite the pzt's are called the what? | Spike line |
| True or false, the sector shape image of an US is created due to the slight variations in the slope of the electrical pattern of the spike line. | True |
| The electronics within the ultrasound system that create specific patterns is called what? | The beam former |
| True of false, when a spike pattern is a straight line, an unfocused sound beam is created. | True |
| The curved pattern of a spike line creates a _________ sound beam. | Focused |
| If there is no predominant slope to a spike line the sound beam will be directed in which way? | Straight down |
| A severe curvature of a spike line creates a shallow or deep focus? | Shallow |
| An electrical spike pattern that is convex or D-shaped creates what kind of a beam shape? | Defocused, but this is only of academic interest and has no application in diagnostic imaging. |
| A smaller diameter PZT creates a _________ focus beam, whereas larger diameter crystals create __________ focus beams. | Shallow; deeper |
| Acoustic footprint refers to what? | The area of the transducer that comes in contact with the skin |
| Annular means what? | Ring-shaped |
| In both linear array and convex sequential array transducers, the active elements have a width of about_____ __________. | One wavelength |
| True or false: In subdicing, a crystal is divided into a group of smaller crystals called sub-elements. These sub-elements are electrically joined, and act as if they are a single crystal, which reduces grating lobes. | True |
| In apodization, ________ electrical signals are used to excite the inner crystals, and progressively ________ electrical spikes excite the outer crystals. | Stronger; weaker |
Created by:
gillybruursema
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