Chapter 10: Sound Beam
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| show | a single disc-shaped, unfocused PZT operating in CW mode
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| As sound travels, what changes that affects the shape of a sound beam? | show 🗑
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| At the starting point, the beam width equals what? | show 🗑
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| What happens to the sound beam's width after leaving the starting point? | show 🗑
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| show | Focus
Near Zone
Focal Length (focal depth, near zone length)
Far Zone
Focal zone
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| show | location where beam diameter is the narrowest
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| show | 1/2
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| What are the synonyms of Focus? | show 🗑
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| What is Focal Length? | show 🗑
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| What determines the focal length? | show 🗑
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| What are some synonyms of focal length? | show 🗑
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| show | region from the TD to the focus
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| show | the sound beam gradually narrows
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| show | the active element
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| At the end of the near zone, the beam narrows to what? | show 🗑
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| show | the Focus
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| show | near field, Fresnel zone
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| show | the region starting at the focus and extending deeper
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| show | the sound beam diverges
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| With a disc-shaped crystal, how wide is the sound beam at the beginning of the far zone? | show 🗑
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| show | the sound beam is again the same size as the active element
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| show | the sound beam is wider than the active element
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| What are some synonyms of the Far Zone? | show 🗑
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| show | the region around the focus where the beam is relatively narrow
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| show | creates images that are more accurate than those at other depths
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| Where is the focal zone located? | show 🗑
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| What is the name of the area where image detail is improved? | show 🗑
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| What characteristics of fixed focus TD combine to determine focal depth? | show 🗑
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| show | directly related
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| show | the focus is deeper
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| show | the focus is deeper
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| show | the focus is deeper
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| How are frequency and focal depth related? | show 🗑
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| Why do manufacturers make high frequency TD with very small diameter PZT? | show 🗑
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| show | at the end of the near zone
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| At depths greater than the focus, the sound beam does what? | show 🗑
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| show | Transducer diameter
Frequency of sound
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| A smaller crystal diameter produce beams that do what in the deep far zone? | show 🗑
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| Crystal diameter and beam divergence is related how? | show 🗑
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| show | large diameter crystals
due to less divergence
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| show | diverges less in the far field
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| Frequency and beam divergence are related how? | show 🗑
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| show | higher frequencies
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| Sound waves produced by very small sources and diverge into a"V" shape are called what? | show 🗑
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| Spherical waves are created how? | show 🗑
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| Spherical waves are also known as what? | show 🗑
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| What are Huygen's sources? | show 🗑
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| What explains the inconsistency between the large PZT crystal producing an hourglass-shaped beam and the small sound source creating a V-shaped beam? | show 🗑
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| Large active element is composed of what? | show 🗑
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| Each tiny particle of a large active element is a what and creates a what with a V-shape? | show 🗑
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| The hourglass shape of a sound wave is a result of what? | show 🗑
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| show | lateral resolution
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| What units are used for lateral resolution? | show 🗑
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| show | small numbers
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| Lateral resolution is determined by what? | show 🗑
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| show | narrow beam
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| show | depth
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| show | synonyms of lateral resolution
Lateral
Angular
Transverse
Azimuthal
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| show | within the focal zone
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| Where is lateral resolution best? | show 🗑
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| What is the equation for lateral resolution? | show 🗑
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| show | axial resolution is better than lateral resolution- U/S pulses are shorter than wide
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| show | axial resolution
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| show | because pulses wider than short
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| What happens when 2 reflectors are closer side by side than the beam width> | show 🗑
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| What improves both axial and lateral resolution? | show 🗑
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| Why does a high frequency TD improve axial resolution? | show 🗑
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| Why does a high frequency TD improve lateral resolution? | show 🗑
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| What improves lateral resolution by concentrating sound energy into a narrow beam? | show 🗑
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| show | External focusing - with a lens
Internal focusing - with a curved active element
Phased array focusing - done by electronics of U/S system
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| Which types of focusing can be used with a single element TD? | show 🗑
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| show | Phased array focusing
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| show | fixed, conventional or mechanical
adjustable
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| show | external and internal focusing
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| Fixed focusing techniques mean what? | show 🗑
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| show | lens placed in front of the PZT material
fixed focus with acoustic lens
Arc of lens becomes prominent-degree of focusing increases-beam narrow in focal zone
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| show | Uses curved PZT element to concentrate sound energy
forms narrower sound beam
As curvature becomes more pronounced-degree of focusing increases
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| What is the most common form of fixed focusing? | show 🗑
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| show | Phased array transducers uses electronics of the U/S system to focus the sound beam
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| Can sonographers alter the focusing characteristics of electronic focusing - phased array? | show 🗑
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| What are the first 2 of the four distinct alterations of the sound beam when its focused? | show 🗑
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| show | Beam diameter in the far zone increases (more divergence) which improves lateral resolution in near and focal zone and degrades it beyond the focal zone;
Focal zone is smaller (region on each side of the focus)
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Created by:
quietone055
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