Optimising Laser Ultrasound Imaging

Optimising Laser Ultrasound Imaging

Ultrasound imaging in MedicineUse of high-frequency sound wavesCaptures real timeNo ionization radiation exposureTypes of ultrasound Abdominal ultrasound, Bone sonometry, Breast ultrasoundWorking of Ultrasound

Stages of Ultrasound imagingProduction of the sound waveHigh frequency v/s Low frequencyConventional method Piezoelectric transducer

Receiving of the echoes

Forming the echoes

Need for all-optical transducersPiezoelectric transducers require electrical connections and circuitry

Makes miniaturisation tough

Miniaturisation needed for probes to be inserted into vagina, rectum, esophagus

All-optical probes might have higher sensitivity and spatial resolutionOptical detection of Ultrasound Positives Non Contact , High Detection Bandwidth, ability to provide exact measurement of the ultrasonic signal.Negatives Optical detection sensitivity is atleast an order of magnitude of poorer than contact transducers.

Basics To optically monitor ultrasound, a light beam should be made to interact with the object undergoing such motion.There are two broad classes in which affect of ultrasound can affect the light beam.1. Intensity Modulation2.Phase or Frequency Modulation Softwares to be usedMATLAB with k-wave toolbox for optimisation of laser

MATLAB High intensity focussed ultrasound simulator

ImageJ Shock software for image reconstructionProject Abstract Ultrasound imaging is widely used in medicine for diagnostics and therapy. Conventional ultrasound imaging probestypically use piezoelectric elements to transmit and record signals, and each element requires electrical connectionsand circuitry that can make miniaturisation challenging and expensive. By employing all-optical ultrasound transmittersand receivers fabricated on top of optical fibres, ultrasound imaging probes can be created without any electroniccomponents and on a very small scale. These all-optical ultrasound probes could potentially have higher sensitivityand spatial resolution than their electronic counterparts. This project is focused on one aspect of optical imaging probes:the generation of ultrasound at the distal end of an optical fibre by means of the photoacoustic effect. Modulated light absorbedin a coating deposited on the end of the fibre causes a small temperature rise which results in an increase in pressure. Thislocalised pressure increase subsequently propagates into tissue as an acoustic wave. The aim of this project is to optimisethe modulation of the light to obtain ultrasound pulses that provide optimal spatial resolution upon reconstruction. The resultsobtained in this project will aid in optimising the image quality of new types of ultrasound imaging probes. The project will beprimarily computational in nature, but will have an experimental component.

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