Oelze - ECE 571 Lecture 2 Biological Measurement 1 BIOE 571

Oelze - ECE 571 Lecture 2Oelze - ECE 571 Lecture 2

Biological Measurement 1Biological Measurement 1

BIOE 571BIOE 571


I. Topics Covered TodayI. Topics Covered Today

• Generation of ultrasoundGeneration of ultrasound• Types of sourcesTypes of sources

• Importance of bandwidth to ultrasonic Importance of bandwidth to ultrasonic imagingimaging

• Importance of field characteristics of Importance of field characteristics of sources to ultrasonic imagingsources to ultrasonic imaging

• Modeling of fieldsModeling of fields


Single-element TransducerSingle-element Transducer

Wire

Damping Material

Crystal

Acoustic Matching Layer

Insulating Layer


Importance of BandwidthImportance of Bandwidth

h(t)

v(t)

v(t)*h(t)


Range Resolution Range Resolution TT11

TT22 A-modeA-mode


Beam PatternsBeam Patterns


Imaging with a Flat PistonImaging with a Flat Piston














B-Mode ImagingB-Mode Imaging




























Array TransducersArray Transducers


Linear ArrayLinear Array

1.1. Can steer beam in azimuth plane only (along y)Can steer beam in azimuth plane only (along y)

2.2. Non-symmetric beam (tighter in y than x)Non-symmetric beam (tighter in y than x)

3.3. Can focus to different depthsCan focus to different depths

xx

yy


Annular ArrayAnnular Array

1.1. Can change focal lengthCan change focal length

2.2. Symmetric beamSymmetric beam

xx

yy


1.5D Array1.5D Array

1.1. Can steer beam in azimuth plane (y)Can steer beam in azimuth plane (y)

2.2. Non-symmetric beam (tighter in y than x)Non-symmetric beam (tighter in y than x)

3.3. The transverse plane (x) is used for elevational The transverse plane (x) is used for elevational focusingfocusing

xx

yy


2D Array2D Array

1.1. Can steer beam in both directions (x and y)Can steer beam in both directions (x and y)

2.2. Elevational focusingElevational focusing

3.3. Many channels needed to operateMany channels needed to operate

xx

yy


Array Imaging: Steering, Low F-NumberArray Imaging: Steering, Low F-Number












Array Imaging: Steering, High F-NumberArray Imaging: Steering, High F-Number

Same Trade-offs as with single elements except, Same Trade-offs as with single elements except, no need to translate source (electronic steering) no need to translate source (electronic steering) and no need to use multiple transducers with and no need to use multiple transducers with different f-numbers (electronic focusing)…different f-numbers (electronic focusing)…


Simple Linear Array: MainlobesSimple Linear Array: Mainlobes

kd = 8.16kd = 8.16

N = 10N = 10

Multiple main lobes Multiple main lobes can occur, which can occur, which causes image causes image degradation in a degradation in a ultrasonic imaging ultrasonic imaging system.system.


Simple Linear Array: MainlobesSimple Linear Array: Mainlobes

kd = 5.6549kd = 5.6549

N = 10N = 10

Only one mainlobe Only one mainlobe and no grating lobesand no grating lobes


Simple Linear Array: SteeringSimple Linear Array: Steering

kd = 5.6549kd = 5.6549

N = 10N = 10



kd = 5.6549kd = 5.6549

N = 10N = 10

With same settings With same settings and steering the and steering the beam to 45 degrees, beam to 45 degrees, we can see the we can see the mainlobe at -23 mainlobe at -23 degrees (but still 10 degrees (but still 10 lobes away).lobes away).



kd = 2.8724kd = 2.8724

N = 10N = 10

One mainlobe, but One mainlobe, but fundamental fundamental engineering trade-off engineering trade-off is that the mainlobe is that the mainlobe is wider.is wider.


Linear ArrayLinear Array

Element has width 2a and height 2bElement has width 2a and height 2b

xx

yy


Simple Linear Array: Element FactorSimple Linear Array: Element Factor

- H- Hee

-- H- H

HHTOTTOT

kd = 5.6549kd = 5.6549

N = 10N = 10

..


Simple Linear Array: Element FactorSimple Linear Array: Element Factor

- H- Hee

-- H- H

HHTOTTOT

kd = 8.482kd = 8.482

N = 10N = 10

..


Simple Linear Array: Element factorSimple Linear Array: Element factor

- H- Hee

-- H- H

HHTOTTOT

kd = 5.6549kd = 5.6549

N = 10N = 10

..



- H- Hee

-- H- H

HHTOTTOT

kd = 5.6549kd = 5.6549

N = 10N = 10

..



- H- Hee

-- H- H

HHTOTTOT

kd = 2.8274kd = 2.8274

N = 10N = 10

..


Simple Linear Array: ApodizationSimple Linear Array: Apodization

-- H - apodization- H - apodization

HH - no apodization- no apodization

kd = 2.8274kd = 2.8274

N = 10N = 10



kd = 5.1408kd = 5.1408

N = 10N = 10



00°° steering steering



kd = 5.1408kd = 5.1408

N = 10N = 10



4545°° steering steering

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Oelze - ECE 571 Lecture 2 Biological Measurement 1 BIOE 571