Term
| When we discuss different types of transducers what do we pay attention to? |
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Definition
- How the beam is steered
- How the beam is focused
- The number of crystals
- The shape of the image produced |
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Term
| What are the different types of steering? |
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Definition
- Mechanical
- Manual
- Electronic |
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Term
| What are the different types of focusing? |
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Definition
- Fixed
> Internal
> External
- Adjustable
> Aperture
> Electronic transmit
> Dynamic (receive) |
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Term
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Definition
- One Crystal
- Fixed Focusing
- Mechanical or Manual Steering
- Image shape is a sector or a circle. |
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Term
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Definition
- A small crystal is rotated by a motor inside a water filled catheter.
- Catheter is pulled though the vessel obtaining a 2D image.
- Later the image can be run through computer reconstruction and turned into a 3D image. |
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Term
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Definition
- 120-250 elements arranged in a LINE.
- Produces a RECTANGULAR image. |
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Term
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Definition
- 120-250 elements arranged in a CURVE.
- A SECTOR image is produced with a ROUNDED top. |
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Term
| What types of technology can linear and curvilinear transducers utilize? |
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Definition
- Sequential technology
- Segmental technology
- Phased technology |
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Term
| Explain sequential technology |
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Definition
- Fixed focusing
- No steering: crystals are shot in order one at a time to obtain multiple scan lines:
> 1st crystal is shot, echo from the deepest structure is received, 1st line of sight is generated.
> 2nd crystal is shot, echo from the deepest structure is received, 2nd line of sight is generated.
> 3rd crystal is shot, echo from the deepest structure is received, 3rd line of sight is generated.
> Etc. |
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Term
| Summary of sequential technology |
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Definition
- The Number of lines of sight = the number of crystals
- The delay between adjacent crystals = 13 microsec/cm x d.
- Each individual crystal is NARROW.
> Shallow focus since Dnf = Wcr^2F/4v
> Good LATA at the focal point since LATA f.pt. = 1/2 Wcr
- Produces a wide linear image in the near field
(good for scanning superficial structures) |
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Term
| Explain Segmental Technology |
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Definition
- Aperture focusing
- No steering: A group of crystals are fired in order one at a time to obtain multiple scan lines.:
> 1st through 4th crystals are fired, echoes are returned from the deepest structure, 1st line of sight is generated.
> 5th through 8th crystals are fired, echoes from deepest structure is returned, 2nd line of sight is generated. |
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Term
| What is Aperture focusing? |
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Definition
| By varying the number of crystals simultaneously fired in a group, you can vary the depth of the near field. |
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Term
| What are the advantages and disadvantages of segmental array? |
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Definition
- Advantage: Adjustable focusing (Aperture)
- Disadvantage: Fewer lines |
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Term
| Explain Segmental Step-Down Technology |
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Definition
- 1st through 4th crystals are fired, echoes from deepest structure are received, 1st line of sight is generated.
- 2nd through 5th crystals are fired, echoes from the deepest structure are received, 2nd line of sight is generated.
- 3rd through 6th crystals are fired.... |
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Term
| What are the advantages of segmental step down array? |
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Definition
- Advantage:
> Flexible focus (aperture)
> multiple lines |
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Term
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Definition
- The LATA can be improved by varying the amount of crystals listening.
- The effect of this is to give the transducer the most sensitivity to listen to returning echoes at a specific depth along the central axis of the beam. |
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Term
| Explain Phased Technology |
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Definition
- Phased technology allows us to:
> electronically steer
> electronically focus
- Focusing at different depths is possible
- Multi-focusing is possible |
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Term
| What is Huygen's Principle? |
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Definition
| - Every point of the wave front acts as a source of new tiny wavelets. The new wave source is then the surface tangent to the wavelets. |
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Term
| Explain Electronic Steering |
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Definition
| - Crystals are fired ONE at a time with a VERYYYYY small time delay. One line of sight is generated with a pulse from all the crystals. |
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Term
| Explain Electronic Focusing. |
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Definition
- Crystals are fired in a curved pattern with a very SMALL time delay.
- ONE line of sight is generated with a pulse from all the crystals. |
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Term
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Definition
- A vector array is a linear probe that combines linear segmental technology with linear phased technology.
- Image shape produced is a sector shape with a flat top. |
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Term
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Definition
- Elements are concentric rings.
- Image has a sector shape.
- Smaller diameter rings provide shallow focusing, bigger diameter rings provide deep focusing.
- Phased technology allows focusing (good LATA) at all depths.
- Steered mechanically. |
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Term
| Multi-dimensional transducers: 1.5 D Array |
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Definition
| - Multiple rows of crystals produces 2D image with a very SMALL SLICE THICKNESS. |
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Term
| Multi-dimensional transducers: 2D Array |
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Definition
- Multiple rows of crystals makes a 3D image
> Each row makes a 2D slice
> Computer assembles a 3D image out of it. |
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Term
Transducer type: Single Element
Image shape:
Steering:
Focusing: |
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Definition
Transducer type:
Image shape: Sector or Circle
Steering: Mechanical or manual
Focusing: Fixed |
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Term
Transducer type: Linear Sequential
Image shape:
Steering:
Focusing: |
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Definition
Transducer type:
Image shape: Rectangle
Steering: None
Focusing: Fixed |
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Term
Transducer type: Linear Segmental
Image shape:
Steering:
Focusing: |
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Definition
Transducer type:
Image shape: Rectangle
Steering: None
Focusing: Aperture or Dyanmic |
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Term
Transducer type: Curvilinear Sequential
Image shape:
Steering:
Focusing: |
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Definition
Transducer type:
Image shape: Sector with rounded top
Steering: None
Focusing: Fixed |
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Term
Transducer type: Curvilinear Segmental
Image shape:
Steering:
Focusing: |
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Definition
Transducer type:
Image shape: sector image with rounded top
Steering: none
Focusing: Aperture or Dynamic |
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Term
Transducer type: Linear Phased or Sector
Image shape:
Steering:
Focusing:
Image type with a single defect: |
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Definition
Transducer type: Linear Phased or Sector
Image shape: Sector
Steering: electronic
Focusing: electronic
Image type with a single defect: Reduced steer and focusing |
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Term
Transducer type: Vector
Image shape:
Steering:
Focusing: |
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Definition
Transducer type:
Image shape: Sector image with flat top
Steering: Electronic (along sides)
Focusing: Electronic |
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Term
Transducer type: Annular
Image shape:
Steering:
Focusing: |
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Definition
Transducer type:
Image shape: Sector
Steering: Mechanical
Focusing: Electronic |
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