Single- ELEMENT ULTRA SOUND TRANSDUCER FOR COMBINED VESSEL LOCALISATION AND ABLATION

7/27/2019 Single- ELEMENT ULTRA SOUND TRANSDUCER FOR COMBINED VESSEL LOCALISATION AND ABLATION

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S7 EA


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introduction

Blood vessel localization and ablation

Highly potent therapeutic method for tumors

Employed to stop blood flow

Used in small arteries and target veins

Require two systems

1)imaging system -localizing blood vessels

2)therapeutic system-ablation treatment Synchronization between imaging and ablation

devices

Use single transducer


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hifu transducer

Focus range-55mm

Operating range-1.6 to 2.4MHz

Focus is in oval shape

Medium for acoustic wave conduction

Two modes of operation

1)Therapeutic mode

2)Imaging mode

Two tests

1)In vitro

2)In vivo


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Experimental setup


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Timing diagram


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In vitro test Test targeting ability

Performed on acryl amide phantoms

Acrylic tank

Albumin mixed into acryl amidephantoms

Water bath-acryl amide phantom

Degassed water preparation


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In vivo test

Test targeting and occluding ability

Performed by capping-

the HIFU transducer

Transducer mounted

on a stepper motor

Experimental setup for >

In vivo tests


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Imaging mode

Acoustic wave generation

Focus pressure estimation

Backscattered signal mixing with noise

Diplexer ,Digital oscilloscope ,A/D card

Customized lab view procedure

Doppler signal calculation


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Therapeutic mode Generate strong acoustic waves

Intensity averaged over space andtime

Acoustic power estimation

Operation mode switched back toimaging mode


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how useful the Doppler signal??

Determine target vessel

location in real time

HIFU transducer scanned the

vessel

Track centre of femoral artery


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Ultrasonic signal processing

Obtains Doppler frequency shift

Data for Doppler signals

Demodulated complex echo signal-nth firing

Doppler spectrum calculation

Doppler spectrum mean velocity


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Results for flow detection

a)Raw RF signals after firing 300 times with PRF 5KHzb)Doppler shifts-tube(diameter-2.9mm,flow rate-150ml/min)c)Comparison detected Doppler frequency &values from actual f low volume

for two pumping rates 150&75mL/min


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Doppler shifts peak amplitude & sum

Peak amplitude Doppler shift

Sum of Doppler shift

Change HIFU transducer focus

Velocity change

a)peak amplitude of Doppler shiftb)sum of Doppler shift


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Ablation in rabbit and rat

a &e:-pre-ablation setup and evaluationb &f:-Doppler signal before ablation(2-D ultrasound)c &g:-Doppler shifts with the HIFU transducer in the imaging mode

d &h:-Doppler signals were absent after ablation (2-D ultrasound)


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advantages

Single transducer for localization and ablation

Less complicated and cheaper

Smaller therapeutic window-easier to operate

Easier to tilt and focus on tissues behind ribs


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disadvantages

Cant provide 2-D ultrasound image

Setting range gate-Doppler signal calculation

Trade-off between good imaging quality and highablation efficiency


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conclusion

New system utilizes single HIFU transducer

In vivo and In vitro tests performed

Switching between imaging and therapeutic mode

Transducer movement-scanning target area

New system include function-stop blood flow


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reference

www.ieeexplore.com (IEEE transactions onUltrasonic ,Ferroelectrics and frequency

control)

www.seminarpaper.com


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Documents

Single- ELEMENT ULTRA SOUND TRANSDUCER FOR COMBINED VESSEL LOCALISATION AND ABLATION