Abstract

Konventionelt ultralyd bruger ufokuserede og fokuserede stråler til at indsamle billedinformation i væv . Men begrænsning i vævets hastigheden er opnået og nye teknikker skal udvikles for at overvinde disse. Negativ fokus har i enkelte tilfælde vist potentiale for at løse dette ved at give en bredere stråle dermed forbedre den parallelle fokusering kapacitet i ultralyd. Der er dog stadig en mangel på viden om den negative fokus i forhold til den ufokuseret og fokuseret stråle. Dette projekt har Fundet en algebraisk model, som samler de indflydelsesrige faktorer aperture størrelse, negativ focus afstand og afstand fra transduceren til at bestemme strålen bredde. Modellen var validere med gode resultater, og viser, hvordan stråle bredden er en projektion af aperturet. Denne model er baseret på en nyudviklet teknik til simulering af ultralyds stråler og valideres med målinger af stråle bredde fra to transducere. Modellen har potentialet til at kombinere de særskilte teorier for de tre stråler til én.

Conventionally ultrasound uses unfocused and focused beams to gather image information in tissue. However limitation in the acquisition speed has been reach and new techniques need to be developed to overcome these. Negative focus has in few cases shown potential to solve this by providing a wider beam thus enhancing the parallel focusing capability in ultrasound. There is however still a lack of knowledge for the negative focus compared to the unfocused and focused beam. This project has determine an algebraic model bringing together the influential factors aperture size, negative focal distance and range to determine the beam width. The model was validate with good results and shows how the beam width is a projection of the aperture. This model is based on a newly developed technique to simulated ultrasound beams and validated with measurements of the beam width from two transducers. The model has the potential to combine the separate theories of the three beams into one.

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A master thesis from Aalborg University

Algebraic model for negative focused ultrasound beam width