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Methods for Hemodynamic Parameters Measurement Using the Laser Speckle Effect in Macro and Microcirculation

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Methods for Hemodynamic Parameters Measurement Using the Laser Speckle Effect in Macro and Microcirculation 100 200 300 400 500 600 Pedro Guilherme da Cunha Leitao˜ Dias Vaz METHODS FOR HEMODYNAMIC PARAMETERS 100 MEASUREMENT200 300 USING400 THE LASER500 SPECKLE EFFECT600 IN 700 800 MACRO AND MICROCIRCULATION PhD thesis in Biomedical Engineering, in co-supervision (co-tutelle) regime between the University of Coimbra (UC) - Portugal and the University of Angers (UA) - France, under the supervision of Dr. Joao˜ Manuel Rendeiro Cardoso (UC) and Professor Anne Humeau-Heurtier (UA), submitted to the Faculty of Sciences and Technology of the University of Coimbra. September 2016 University of Coimbra and University of Angers PhD Thesis Programa Doutoral em Engenharia Biomedica´ (UC) And Doctorat en Traitement du Signal et de l'Image (UA) Methods for hemodynamic parameters measurement using the laser speckle effect in macro and microcirculation. Author: Pedro Guilherme da Cunha Leit~aoDias Vaz Supervisors: Dr. Jo~aoRendeiro Cardoso (University of Coimbra) Prof. Anne Humeau-Heurtier (University of Angers) 2016 Esta c´opiada tese ´efornecida na condi¸c~aode que quem a consulta reconhece que os direitos de autor s~aoperten¸ca do autor da tese, da Universidade de Coimbra e da Universidade de Angers e que nenhuma cita¸c~aoou informa¸c~aoobtida a partir dela pode ser publicada sem a refer^enciaapropriada. Cette copie de la th`esea ´et´efourni `ala condition que toute personne qui consulte de reconna^ıtre que son droit d'auteur appartient avec son auteur, avec l'Universit´ede Coimbra et avec l'Universit´ed'Angers et qu'aucune mention de la th`esepeut ^etrepubli´e sans r´ef´erenceappropri´ee. This copy of the thesis has been supplied on condition that anyone who consults it is understood to recognize that its copyright rests with its author, with the University of Coimbra and with the University of Angers and that no quotation from the thesis and no information derived from it may be published without proper reference. The research reported in this thesis was performed with financial support of the fol- lowing institutions/programs: PhD scholarship number SFRH/BD/89585/2012 granted by the Funda¸c~aopara a Ci^enciae Tecnologia. PESSOA/Hubert Curien travelling program granted by the Funda¸c~aopara a Ci^encia e Tecnologia and by the CAMPUS FRANCE. A¸c~oesintegradas Luso Francesas/PAUILF granted by Conselho de Reitores das Uni- versidades Portuguesas (CRUP) and Conf´erencedes Pr´esidents d'Universit´e(CPU). i Resumo O laser speckle corresponde a um efeito de interferometria que foi muitas vezes consider- ado como uma grande limita¸c~aodo uso de fontes de luz coerente. No entanto, para um conjunto espec´ıficode aplica¸c~oes, este efeito pode ser usado como fonte de informa¸c~ao. Entre estas aplica¸c~oespodemos encontrar v´arias no ^ambito da biomedicina. Esta t´ecnica tem vindo a ser utilizada durante d´ecadaspara avaliar a perfus~aosangu´ıneamas, ape- nas agora, come¸caa despertar interesse como meio de avaliar tamb´em a macrocircula¸c~ao. Este trabalho pretende demonstrar que o efeito de laser speckle pode ser usado, tamb´em, para extrair informa¸c~aoimportante relativa `acondi¸c~aocardiovascular, nomeadamente da macrocircula¸c~ao,com boa fiabilidade e usando m´etodos semelhantes aos j´aaplicados na avalia¸c~aoda microcircula¸c~ao. O facto de serem usados os mesmo m´etodos poder´alevar a uma r´apidainclus~aodeste tipo de an´alisenos dispositivos j´aexistentes. No campo do uso de laser speckle para avalia¸c~aoda microcircula¸c~ao,uma das quest~oesmais impor- tantes est´arelacionada com o efeito dos dispersores est´aticos. A quantidade de dispersores est´aticosinfluencia fortemente o sinal de laser speckle, levando a interpreta¸c~oesincorretas dos dados. Este ´eum dos fatores que impede a exist^enciade dispositivos laser speckle com capacidade de quantificar o fluxo sangu´ıneo. Devido a isto, o estudo do efeito de difer- entes concentra¸c~oesde dispersores est´aticosnos sinais de contraste e correla¸c~aospeckle ´e tamb´emum dos objetivos deste trabalho. Esta tese apresenta os estudos realizados com o objetivo de testar a possibilidade de usar o efeito de laser speckle para avalia¸c~aode par^ametroshemodin^amicosda microcir- cula¸c~aoe o trabalho experimental realizado no ^ambito do efeito dos dispersores est´aticos. Antes do trabalho experimental, esta tese come¸ca por descrever os princ´ıpiosb´asicosda teoria de laser speckle. Nesta sec¸c~ao´erealizada uma an´alisecr´ıticada literatura dispon´ıvel e s~aoidentificados os desafios futuros desta t´ecnica.Algumas ideias inovadoras s~aotamb´em propostas como m´etodos para lidar com alguns dos problemas atuais da t´ecnicade laser speckle. Os trabalhos desenvolvidos na ´areada macrocircula¸c~aodemonstraram que o efeito de laser speckle pode ser usado para extrair a forma de onda de pulso. Um estudo com fontes de luz de diferentes comprimentos de onda foi efetuado para determinar qual destes comprimentos de onda apresenta melhores resultados. Os comprimentos de onda mais curtos (luz verde) conseguiram atingir os melhores resultados na identifica¸c~aodo ritmo card´ıaco. Num segundo teste, usando os mesmo m´etodos j´ausados para a avalia¸c~aoda microcircula¸c~ao,o efeito de laser speckle foi capaz de reconstruir a onda de pulso e iden- tificar pontos caracter´ısticoscomo o pico sist´olicoe o n´odicr´otico.Para alem disto, este mesmo sistema foi usado num teste piloto para segmentar alvos bidimensionais com movi- mentos longitudinais. Um algoritmo baseado no c´alculoda entropia foi usado com sucesso para distinguir dois alvos id^enticos, onde apenas um apresentava movimento. Para al´em disto, este m´etodo permitiu segmentar o alvo em movimento sem nenhuma informa¸c~ao antecipada sobre a movimenta¸c~aodos alvos ou a disposi¸c~aoda cena. Relativamente ao campo da microcircula¸c~ao,um teste experimental foi desenvolvido iii iv para estudar o efeito dos dispersores est´aticosno sinal de laser speckle. Este teste consistiu na avalia¸c~aode um fantoma constitu´ıdopor um micro-canal e diferentes camadas de dis- persores. Este fantoma foi usado para simular a perfus~aosangu´ıneaem vasos de pequeno calibre. Os dados recolhidos foram processados em termos de contraste e correla¸c~ao.Os resultados indicaram que a correla¸c~aoentre duas imagens consecutivas ´ecapaz de identi- ficar a quantidade relativa de dispersores est´aticos/din^amicose deve ser usada como meio para atingir uma t´ecnicacompletamente quantitativa. A correla¸c~aode speckle demon- strou tamb´emser independente da velocidade dos dispersores din^amicos.Em rela¸c~aoao contraste de speckle, o algoritmo temporal apresentou uma boa independ^enciaem termos de concentra¸c~aode dispersores est´aticos. O algoritmo espa¸co-temporal demonstrou ser aquele que apresenta uma melhor coer^enciacom a teoria do efeito laser speckle. Concluindo, o efeito de laser speckle ´euma ferramenta altamente vers´atile provou ser capaz de extrair par^ametroshemodin^amicosrelacionados com a macrocircula¸c~ao. Este trabalho tamb´emdemonstrou que a correla¸c~aode laser speckle permite estimar o r´acio entre a quantidade de dispersores est´aticos/din^amicoscom boa fiabilidade. Palavras-chave: Laser speckle, forma de onda de pulso, dispersores est´aticos, macrocircula¸c~ao,microcircula¸c~ao. Resum´e Le speckle laser est un effet d'interf´erencelongtemps consid´er´ecomme n´efastelors de l'utilisation de sources de lumi`erecoh´erente. Cependant, pour certaines applications, cet effet peut ^etreb´en´efiqueet utilis´ecomme source d'information. C'est le cas du domaine biom´edical. Ainsi, le speckle laser est utilis´edepuis des d´ecenniespour la surveillance du flux sanguin microvasculaire. Il commence `a^etreconsid´er´eaussi pour l'extraction de param`etresde la macrocirculation sanguine. Ce travail vise donc tout d'abord `ad´emontrer que le speckle laser permet d'´evaluer les param`etres h´emodynamiques de la macrocircula- tion avec fiabilit´eet `apartir d'une technique identique `acelle employ´eedans l'´etudede la microcirculation. Ceci conduira `aune int´egrationrapide du dispositif dans les instruments existants. Par ailleurs, l'un des probl`emesles plus importants du speckle laser, emp^echant l'obtention d'une analyse totalement quantitative, est l’effet des diffuseurs statiques. Ce type de diffuseurs influence fortement le contraste de speckle, conduisant `aune mauvaise interpr´etationdes donn´ees. Le second objectif de ce travail est donc d'´etudierl’effet des diffuseurs statiques sur la corr´elationet le contraste du speckle laser. Afin d'atteindre ces objectifs, nous commen¸consce travail par une introduction `ala th´eoriede base du speckle laser. Une analyse critique de la litt´eraturesur ce ph´enom`ene est propos´ee.Nous sugg´erons´egalement des d´efis`alever pour les futures applications du speckle laser. Par la suite, nos travaux r´ealis´esdans le domaine de macrocirculation sont expos´es.Nous montrons que le speckle laser peut ^etreutilis´epour extraire l'onde de pouls. En outre, une ´etudemulti-longueur d'onde a ´et´emen´ee afin de d´eterminerquelle longueur d'onde serait la plus appropri´eepour l'analyse de la macrocirculation. Les longueurs d'onde plus courtes ont permis d'aboutir `ade meilleurs r´esultatsdans l'identification de la fr´equencecardiaque. Par ailleurs, nous observons que l'utilisation des m^emes m´ethodes de traitement du signal que celles employ´eesdans les dispositifs actuels (´etudede la microcir- culation) permet de reconstituer l'onde de pouls et d'identifier ses points caract´eristiques comme le pic systolique et l'encoche dicrote. Par ailleurs, le m^emedispositif exp´erimental a ´et´eutilis´epour effectuer une segmentation en deux dimensions de cibles avec mouvements longitudinaux. Un algorithme bas´esur l'entropie a ´et´eappliqu´eaux donn´eesdu speckle laser afin de discerner deux cibles identiques, dont une seule est en mouvement.
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