Introduction toadvanced Ultrasound Imaging techniquesIntroduction toIntroduction toadvanced Ultrasound Imaging techniquesadvanced Ultrasound Imaging techniques

Christian Kollmann Ph.D

Center for Biomedical Engineering & Physics

Medical University of Vienna

Technical Ultrasound-Lab at the General Hospital

(AKH Vienna)Level 4L, Waehringer Guertel 18 – 20A - 1090 Vienna

Tel : (+43 1) 40400 - 1712Fax: (+43 1) 40400 - 3988

E-mail : christian.kollmann@meduniwien.ac.atInternet : www.bmtp.akh-wien.ac.at/people/kollch1/

update 2005

© Chr. Kollmann

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1. IntroductionWhen clinical imaging began … & its actual clinical diversity

2. Modern Equipment technologies & its clinical applications2.1 advanced signal processing developments

- Multi-Hertz & Fusion Imaging- SonoCT, Panoramic View, B-Flow- Coded pulse excitation- Multimodal Imaging- Harmonic Imaging (with / without contrast agents)- Elastography- 3D- / 4D-mode

2.2 advanced Hardware developments- Matrix transducer design- portable & wire-less US equipment (ASICS technology)

Table of contents

Clinical A-Mode (historical medical measurements, early 50s)

The austrian physician Dussik was the first (1942), who has used ultrasound formedical-diagnostic purposes

Transmission mode (Hyperphonometry)on the head

(shown a later measurement session)

© Chr Kollmann

left righthead side

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Development of clinical imaging applications

year # of applications

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2005

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advancedsignal processingdevelopments

advancedadvancedsignal processingsignal processingdevelopmentsdevelopments

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Requirements :• piezoelectric materials with large bandwidth• complex transducer (128 elements)• selectable frequencies, e.g. 2-3 (“Multi-Hertz”)

selectable spectra of probe

Fusion Imaging :• combination of generated high- &

low-frequency 2D-images

Advantages :• fine structured images• higher contrast resolution• larger penetration depth with

same probe

Modern Equipment technology : Multi-Hertz & Fusion Imaging

bandwidth of probe

- propagation of scanlines in different angles- acquiring of images from slight different views

combining all acquired images to one image in real-time

SonoCT, ATLSieClear, Siemens

Signal processing technique (SonoCT)UltraSoundUltraSound--LabLab

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Clinical applications of US imaging techniques (SonoCT)

Abdomen

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conventional new techniqueSonoCT, ATLSieClear, Siemens

conventional new techniquepositioning of a biopsy needle

Clinical applications of US imaging techniques (SonoCT)UltraSoundUltraSound--LabLab

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ATL / Philips

Abdominal & Organs

• emergency diagnosis• tumors, lesions• tissue differentiation• shape- & dimension evaluation

Clinical applications of US imaging techniques (bowel)UltraSoundUltraSound--LabLab

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7 cm long breast abcessssurvey of extremities

• large field scanning• pixel-by-pixel pattern recognition technique

B - Mode(Siemens)

Clinical applications of US imaging techniques (SieScape)

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complete fetustotal liver scanning

B - Mode(General Electric)

Clinical applications of US imaging techniques

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Visualization of blood flow within B-mode without Doppler shift-evaluation

B-mode / B-Flow (General Electric, SieFlow, Siemens)

• simultaneous imaging of tissue & blood flow• high resolution images at high frame rates

• emission of a coded broadband pulse (coded excitation)• signal tissue typically 20 – 30 db > signal reflected by blood

• echos are cross-correlated• echos available, that are equal to coded ones• amplitude of echos is enhanced• echo has its original short pulse characteristics

technical implementation :• 2 resp. 4 pulse sequences / image line (10 - 12 for CFM)• echos of tissue (stationary) -> B-mode black-coded• echos of blood or dyn. tissue -> B-mode grey-coded

1 1 1 0 1 0 1 1

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Features :

• direction & velocity cannot be originally quantified• signal amplitude depends on n, D-blood• small angle dependency• representation of scatters depend on scanner´s line generation• artefacts by moving tissue• higher spatial- & time resolution than CFM• higher frame rate (19 Hz instead of 8 Hz CFM)• no flow information behind calcifications

B-mode / B-Flow (General Electric) II

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Artery carotis

Clinical applications of B-Flow

conventional color Doppler B-Flow

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Internal carotis artery stenosisCommon carotid

(B-flow color-coded)

Clinical applications of B-Flow II

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dialysis graftpseudoaneurysm

Common carotis(ulceration)

Clinical applications of B-Flow III

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UltraSoundUltraSound--LabLabModern Equipment technology : Coded pulse excitation

• Codes are a unique signature on the sound beamformed by repeating a specific pattern of 1’s and 0’s

• Codes may be used to- Improve sensitivity (e.g. Coded Excitation)- Suppress unwanted signal components

• Applications in - B-flow - coded Harmonics - coded Harmonic Angio

1 1 1 0 1 0 1 1

conventional pulse coded pulse train

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UltraSoundUltraSound--LabLabModern Equipment technology : Coded pulse excitation II

• 7 MHz resolution at penetrations up to 20 cm (shown : phantom study)

18 cm18 cm

?conventional coded excitation

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UltraSoundUltraSound--LabLabModern Equipment technology : Coded pulse excitation III

duodenum

combiningdifferent imagingmodalitiesto one image(fusion/matching)

homogenous 4 x 4Transformationmatrix T

original2-D images

matched2-D image

co-registrationprocess

Clinical applications of Multimodal Imaging (Matching)

CT, MRI

UltraSound-Lab BMTP, Vienna

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Clinical applications of Multimodal Imaging (Matching) II

UltraSound-Lab BMTP, Vienna

- additional membrane is visible (arrow)

Subarachnoidal cyst (TCCS & MRT)

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- additional flow information is available

- circulus arteriosus Willisii within thebenign tumor visible

- information about location for pre-operational plannings

- therapy control easily & with an inex-pensive modality possible

Meningeom (TCCS & CCT)

Clinical applications of Multimodal Imaging (Matching) IIIUltraSoundUltraSound--LabLab

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UltraSoundUltraSound--LabLabModern Equipment technology : Harmonic imaging (static)

• using non-linear parts of the echo (i.e. higher frequencies)for imaging process

• US propagation through tissue results in non-linear effects :

harmonics

conventional

Applications known e.g. as : Tissue Harmonic Imaging(THI, Siemens)

freceive = femit

freceive = femit + 2 femit + 3 femit

emission receive receive

narrow band

Clinical applications of Harmonic Imaging

normal Tissue Harmonic Imaging(Siemens)

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Clinical applications of Harmonic Imaging

normal Tissue Harmonic Imaging

thrombus and ovarian cyst

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Clinical applications of Harmonic Imaging II

Tissue Harmonic Imaging (right, Toshiba)4-chamber view

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Tissue Doppler (Harmonic) Imaging TDI combined with M-modeheart systolic / diastolic(left /right) (Toshiba)

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Clinical applications of Harmonic Imaging III

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UltraSoundUltraSound--LabLabModern Equipment technology : Harmonic imaging (dynamic)

• in combination with US contrast agents (UCA) also non-linear partsof the echo (i.e. higher frequencies) can be used for imaging

n : harmonic number (½, 1,2,..)v : velocity scattererc : sound speedα : Doppler angle

Applications knowne.g. as :Second Harmonic,Intermittent HarmonicImaging

cvfnf emit

ndαcos2

=

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from : Kollmann, Putzer, Radiologe 6 (2005)

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UltraSoundUltraSound--LabLabModern Equipment technology : Harmonic imaging (dynamic) III

from : Kollmann, Putzer, Radiologe 6 (2005)

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UltraSoundUltraSound--LabLabModern Equipment technology : Harmonic imaging (dynamic) IV

• wide bandwidth probe

• sophisticated filter algorithm

selectable tissue or CA display

conventional

freceive = femit

Clinical applications of Harmonic Imaging

Normal perfusion of the myocardiumusing Levovist as contrast Agent (destroying CA phase)

(Toshiba)

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(Intermittent / Flash echo)

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Clinical images in combination with ultrasound contrast agents :

allows imaging of smalll amounts of UCAwith high spatial resolution

Clinical applications of Harmonic Imaging II

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UltraSoundUltraSound--LabLabModern Equipment technology : Pulse inversion Harmonics

• suppressing unwanted fundamental tissue signals

fundamental signal fundamental signal

harmonicsignal

harmonicsignal

180° phase-shiftedfundamental signal

180° phase-shiftedfundamental signal

conventional

pulse inversion

ATL

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Result :

fundamental & 180° phase-shifted signalextinguish each other

only harmonic signalremains

fundamental signal

harmonic signal

180° phase-shiftedfundamental signal

Modern Equipment technology : Pulse inversion Harmonics II

harmonic signal remains

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Elastography : visualization of the elastic properties of tissuesince 1991

(Elasticity- / Young-Modul)

ρ = density

c = sound speed

Z = impedance

US-Imaging : visualization of different acoustical impedancesconventional (compression, density)

(Compressibility-Modul)

Modern Equipment technology : Elastography

εσ

=E

cZ== ρ2c K

instead of : σ = tension

ε = expansion

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Acquisitionof images

(step-wise decompressionof tissue)

calculation of2D-moving matrix“ optical flow-principle”

correction ofbasis data

“ local companding “

calculation of expansion

tissue : high elasticity -> strong expansion (red coded)intrusion : low elasticity -> low expansion (blue/green coded)

Modern Equipment technology : Elastography II

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phantom study for detecting structures invisible with conventional imaging

Clinical applications of Elastography

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breast lesion

Clinical applications of Elastography

kidney tissue

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- internal stepper motor changes the scanplane inside the transducer (KretzTechnik, A)

- the scanned volume has a pyramidalform that can be visualized in arbitraryangles

- a special “niche” mode can be displayedthat allows the observer to cut arbitrary planes within this volume and that are perpendicular to each other (90°)

3D / 4D-Mode

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- a positioning device is attachedon a normal 2D-US probe/ trans-ducer

- the probe is moved “freehand” along the observed patient´s region

- the 2D-US images and the trak-king information is used tocalculate a volume image

3D / 4D-Mode “ free-hand procedure “

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these technique is used for :

- displaying & measuring volumes, angles& distances

- displaying organ or skin surfaces(render mode)

Clinical applications of 3D

-3D-representation of kidney perfusion(Power Mode)

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- fetal skeleton

- flow of umbilical cord

fetal gender -

- fetal fingers

Comparison -3D-US / newborn (lip cleft)

frighting fetus -

maldeformation & disorders

Clinical applications of 3D II

Clinical imaging applications (4D-Mode)

- real-time (16 fps) display of 3D-rendered fetal shape

(Kretz Technik)

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3-Scape, Siemens

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advancedHardware developmentsadvancedadvancedHardware Hardware developmentsdevelopments

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Technical development of the 2D-Array :

• 1 D-array : discrete aperture + statical focus• 1,25 D-array : discrete aperture variation + statical focus• 1,5 D-array : dyn. aperture variation + dyn. (but symmetr.) focus• 1,75 D-array : dyn. aperture variation + dyn. asymmetr. focus• 2 D-array : dyn. aperture variation + dyn. focus

ASIC-Technology (length of element : 200 - 300 µm quadrat.; line widths 25 µm /

vias : 50 µm)

Hardware developments : Matrix transducer design

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Advantage & possibilities :

• reduction of partial volume orslice-thickness effects

• higher frame rate• dynamic focussing and receiving• better image quality

• Real-Time 3D-representation (18-40 frames/sec)(“ 4D- Ultrasound “)

Hardware developments : Matrix transducer design II

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Problems (some still unresolved) :

• high element density• large number of cables (> 10000)• Piezomaterial (lead zirconate / PZN-PT; multi-layer or. single crystal)• frequencies > 15 MHz (i. use between 1 - 7 MHz)• insertion loss : 60 - 70 dB above conventional array

future :fully digital probe

Hardware developments : Matrix transducer design III

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Features :

• notebook-dimension• 5 - 6.4 inch TFT non-interlaced (640 x 480)• high resolution 2D (full digital beamforming)• Cine & Zoom; Caliper tools• 2D / Color (Power) Doppler• div. 2 - 7 MHz Array- probes• DR : <= 140 dB; FR : 100 frames/sec

Hardware development : Portable & wire-less US equipment

Technology :

• 4 ASICs on a board(Application-Specific Integrated Circuit1 cm2, “systems-on-a-chip”)

• dimension of transistor < 1 µm• high performance & fully digital• battery-powered• rel. low-manufacturing costs

• image storing > 50 frames

• Price : ca. 2500.- US$

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Micros Q.V.(Carolina Medical, USA)

Examples :

Terason 2000(TeraTech Corp., USA)

Hardware development : Portable & wire-less US equipment II

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Sonosite 180(Sonosite/ATL, USA)

Mysono 201(Medison, Korea)

Examples :

Hardware development : Portable & wire-less US equipment III

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Vivid i(General Electric, USA)

Examples :

Hardware development : Portable & wire-less US equipment IV

Logiq Book XP(General Electric, USA)

depends on clinical application :

Clinical used transducer types for imaging

vaginal probe rectal probe 3D-abdominal

Transesophagealprobe

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commercialpool of US

devices

Clinical available US equipmentUltraSoundUltraSound--LabLab

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... and what can this be ?UltraSoundUltraSound--LabLab

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ThankThank youyou forfor youryour attentionattention !!!!