カラードプラ心エコーに基づく血流の定量的評価

Tohoku University西條芳文課

Evaluation of intraventricular flow by multimodality imaging: a review and meta-analysis

Background The aim of this systematic review was to evaluate current inter-modality agreement of noninvasive clinical intraventricular flow (IVF) assessment with 3 emerging imaging modalities: echocardiographic particle image velocimetry (EPIV), vector flow mapping (VFM), and 4-dimensional flow cardiovascular magnetic resonance imaging (4D flow CMR). Methods We performed a systematic literature review in the databases EMBASE, Medline OVID and Cochrane Central for identification of studies evaluating left ventricular (LV) flow patterns using one of these flow visualization modalities. Of the 2224 initially retrieved records, 10 EPIV, 23 VFM, and 25 4D flow CMR studies were included in the final analysis. Results Vortex parameters were more extensively studied with EPIV, while LV energetics and LV transport mechanics were mainly studied with 4D flow CMR, and LV energy loss and vortex circulation were implemented by VFM studies. Pooled normative values are provided for these parameters. The meta- analysis for the values of two vortex morphology parameters, vortex length and vortex depth, failed to reveal a significant change between heart failure patients and healthy controls. Conclusion Agreement between the different modalities studying intraventricular flow is low and different methods of measurement and reporting were used among studies. A multimodality framework with a standardized set of flow parameters is necessary for implementation of noninvasive flow visualization in daily clinical practice. The full potential of noninvasive flow visualization in addition to diagnostics could also include guiding medical or interventional treatment.Cardiovascular Aspects of Radiolog

先天性心疾患における体循環系心室の血流動態と機能の解明

Tohoku University西條芳

Ultrasonic colour Doppler imaging

Ultrasonic colour Doppler is an imaging technique that combines anatomical information derived using ultrasonic pulse-echo techniques with velocity information derived using ultrasonic Doppler techniques to generate colour-coded maps of tissue velocity superimposed on grey-scale images of tissue anatomy. The most common use of the technique is to image the movement of blood through the heart, arteries and veins, but it may also be used to image the motion of solid tissues such as the heart walls. Colour Doppler imaging is now provided on almost all commercial ultrasound machines, and has been found to be of great value in assessing blood flow in many clinical conditions. Although the method for obtaining the velocity information is in many ways similar to the method for obtaining the anatomical information, it is technically more demanding for a number of reasons. It also has a number of weaknesses, perhaps the greatest being that in conventional systems, the velocities measured and thus displayed are the components of the flow velocity directly towards or away from the transducer, while ideally the method would give information about the magnitude and direction of the three-dimensional flow vectors. This review briefly introduces the principles behind colour Doppler imaging and describes some clinical applications. It then describes the basic components of conventional colour Doppler systems and the methods used to derive velocity information from the ultrasound signal. Next, a number of new techniques that seek to overcome the vector problem mentioned above are described. Finally, some examples of vector velocity images are presented

4D ultrafast ultrasound flow imaging: in vivo quantification of arterial volumetric flow rate in a single heartbeat

ABSTRACT: We present herein 4D ultrafast ultrasound flow imaging, a novel ultrasound-based volumetric imaging technique for the quantitative mapping of blood flow. Complete volumetric blood flow distribution imaging was achieved through 2D tilted plane-wave insonification, 2D multi-angle cross-beam beamforming, and 3D vector Doppler velocity components estimation by least-squares fitting. 4D ultrafast ultrasound flow imaging was performed in large volumetric fields of view at very high volume rate (>4000 volumes s(-1)) using a 1024-channel 4D ultrafast ultrasound scanner and a 2D matrix-array transducer. The precision of the technique was evaluated in vitro by using 3D velocity vector maps to estimate volumetric flow rates in a vessel phantom. Volumetric Flow rate errors of less than 5% were found when volumetric flow rates and peak velocities were respectively less than 360 ml min(-1) and 100 cm s(-1). The average volumetric flow rate error increased to 18.3% when volumetric flow rates and peak velocities were up to 490 ml min(-1) and 1.3 m s(-1), respectively. The in vivo feasibility of the technique was shown in the carotid arteries of two healthy volunteers. The 3D blood flow velocity distribution was assessed during one cardiac cycle in a full volume and it was used to quantify volumetric flow rates (375 +/- 57 ml min(-1) and 275 +/- 43 ml min(-1)). Finally, the formation of 3D vortices at the carotid artery bifurcation was imaged at high volume rates

Caractérisation de vortex intraventriculaires par échographie Doppler ultrarapide

Les maladies cardiaques sont une cause majeure de mortalité dans le monde (la première cause en Amérique du nord [192]), et la prise en charge de ses maladies entraîne des coûts élevés pour la société. La prévalence de l’insuffisance cardiaque augmente fortement avec l’âge, et, avec une population vieillissante, elle va demeurer une préoccupation croissante dans le futur, non seulement pour les pays industrialisés mais aussi pour ceux en développement. Ainsi il est important d’avoir une bonne compréhension de son mécanisme pour obtenir des diagnostics précoces et un meilleur prognostic pour les patients. Parmi les différentes formes d’insuffisance cardiaque, on trouve la dysfonction diastolique qui se traduit par une déficience du remplissage du ventricule. Pour une meilleure compréhension de ce mécanisme, de nombreuses études se sont intéressées au mouvement du sang dans le ventricule. On sait notamment qu’au début de la diastole le flux entrant prend la forme d’un anneau vortical (ou vortex ring). La formation d’un vortex ring par le flux sanguin après le passage d’une valve a été décrite pour la première fois en 1513 par Léonard de Vinci (Fig. 0.1). En effet après avoir moulé l’aorte dans du verre et ajouter des graines pour observer le flux se déplaçant dans son fantôme, il a décrit l’apparition du vortex au passage de la valve aortique. Ces travaux ont pu être confirmés 500 ans plus tard avec l’apparition de l’IRM [66]. Dans le ventricule, le même phénomène se produit après la valve mitrale, c’est ce qu’on appelle le vortex diastolique. Or, le mouvement d’un fluide (ici le sang) est directement relié a son environnement : la forme du ventricule, la forme de la valve, la rigidité des parois... L’intérêt est donc grandissant pour étudier de manière plus approfondie ce vortex diastolique qui pourrait apporter de précieuses informations sur la fonction diastolique. Les modalités d’imagerie permettant de le visualiser sont l’IRM et l’échographie. Cette thèse présente l’ensemble des travaux effectués pour permettre une meilleure caractérisation du vortex diastolique dans le ventricule gauche par imagerie ultrasonore Doppler. Pour suivre la dynamique de ce vortex dans le temps, il est important d’obtenir une bonne résolution temporelle. En effet, la diastole ventriculaire dure en moyenne 0.5 s pour un coeur humain au repos, une cadence élevée est donc essentielle pour suivre les différentes étapes de la diastole. La qualité des signaux Doppler est également primordiale pour obtenir une bonne estimation des vitesses du flux sanguin dans le ventricule. Pour étudier ce vortex, nous nous sommes intéressés à la mesure de sa vorticité en son centre v et à l’évolution de cette dernière dans le temps. Le travail se divise ainsi en trois parties, pour chaque un article a été rédigé : 1. Développement d’une séquence Doppler ultrarapide : La séquence se base sur l’utilisation d’ondes divergentes qui permettent d’atteindre une cadence d’image élevée. Associée à la vortographie, une méthode pour localiser le centre du vortex diastolique et en déduire sa vorticité, nous avons pu suivre la dynamique de la vorticité dans le temps. Cette séquence a permis d’établir une preuve de concept grâce à des acquisitions in vitro et in vivo sur des sujets humains volontaires. 2. Développement d’une séquence triplex : En se basant sur la séquence ultrarapide Doppler, on cherche ici à ajouter des informations supplémentaires, notamment sur le mouvement des parois. La séquence triplex permet non seulement de récupérer le mouvement sanguin avec une haute cadence d’images mais aussi le Doppler tissulaire. Au final, nous avons pu déduire les Doppler couleur, tissulaire, et spectral, en plus d’un Bmode de qualité grâce à la compensation de mouvement. On peut alors observer l’interdépendance entre la dynamique du vortex et celle des parois, en récupérant tous les indices nécessaires sur le même cycle cardiaque avec une acquisition unique. 3. Développement d’un filtre automatique : La quantification de la vorticité dépend directement des vitesses estimées par le Doppler. Or, en raison de leur faible amplitude, les signaux sanguins doivent être filtrés. En effet lors de l’acquisition les signaux sont en fait une addition des signaux sanguins et tissulaires. Le filtrage est une étape essentielle pour une estimation précise et non biaisée de la vitesse. La dernière partie de ce doctorat s’est donc concentrée sur la mise au point d’un filtre performant qui se base sur les dimensions spatiales et temporelles des acquisitions. On effectue ainsi un filtrage du tissu mais aussi du bruit. Une attention particulière a été portée à l’automatisation de ce filtre avec l’utilisation de critères d’information qui se basent sur la théorie de l’information.Heart disease is one of the leading causes of death in the world (first cause in North America [192]), and causes high health care costs for society. The prevalence of heart failure increases dramatically with age and, due to the ageing of the population, will remain a major concern in the future, not only for developed countries, but also for developing countries. It is therefore crucial to have a good understanding of its mechanism to obtain an early diagnosis and a better prognosis for patients. Diastolic dysfunction is one of the variations of heart failure and leads to insufficient filling of the ventricle. To better understand the dysfunction, several studies have examined the blood motion in the ventricle. It is known that at the beginning of diastole, the filling flow creates a vortex pattern known as a vortex ring. This development of the ring by blood flow after passage through a valve was first described in 1513 by Leonardo Da Vinci (Fig. 0.1). After molding a glass phantom in an aorta and adding seeds to visually observe the flow through the phantom, he could describe the vortex ring development of the blood coming out of the aortic valve. His work was confirmed 500 years later with the emergence of MRI [66]. The same pattern can be observed in the left ventricle when the flow emerges from the mitral valve, referred to as the diastolic vortex. The flow motion (in our case the blood) is directly related to its environment : shape of the ventricle, shape of the valve, stiffness of the walls... There is therefore a growing interest in further studies on this diastolic vortex that could lead to valuable information on diastolic function. The imaging modalities which can be used to visualize the vortex are MRI and ultrasound. This thesis presents the work carried out to allow a better characterization of the diastolic vortex in the left ventricle by Doppler ultrasound imaging. For temporal monitoring of vortex dynamics, a high temporal resolution is required, since the ventricular diastole is about 0.5 s on average for a resting human heart. The quality of Doppler signals is also of utmost importance to get an accurate estimate of the blood flow velocity in the ventricle. To study this vortex, we focused on evaluating the core vorticity evaluation and especially on its evolution in time. The work is divided in three parts, and for each of them an article has been written : 1. Ultrafast Doppler sequence : The sequence is based on diverging waves, which resulted in a high frame rate. In combination with vortography, a method to locate the vortex core and derive its vorticity, the vortex dynamics could be tracked over time. This ix sequence could establish a proof of concept based on in vitro and in vivo acquisitions on healthy human volunteers. 2. Triplex sequence : Based on the ultrafast sequence, we were interested in adding information on the wall motion. The triplex sequence is able to recover not only the blood motion with a high framerate but also tissue Doppler. In the end, we could derive color, tissue, and spectral Doppler, along with a high quality Bmode by using motion compensation. The interdependence between vortex and walls dynamics could be highlighted by acquiring all the required parameters over a single cardiac cycle. 3. Automatic clutter filter : Vorticity quantification depends directly on the estimation of Doppler velocity. However, due to their low amplitude, blood signals must be filtered. Indeed, acquired signals are actually an addition of tissue and blood signals. Filtering is a critical step for an unbiased and accurate velocity estimation. The last part of this doctoral thesis has focused on the design of an efficient filter that takes advantage of the temporal and spatial dimensions of the acquisitions. Thus the tissue alongside the noise is removed. Particular care was taken to automatize the filter by applying information criteria based on information theory

超音波Vector flow imagingによる実験回路を用いたVA-ECMO mixing zoneの観察

Tohoku University西條芳文課

From Molecules to the Masses : Visual Exploration, Analysis, and Communication of Human Physiology

Det overordnede målet med denne avhandlingen er tverrfaglig anvendelse av medisinske illustrasjons- og visualiseringsteknikker for å utforske, analysere og formidle aspekter ved fysiologi til publikum med ulik faglig nivå og bakgrunn. Fysiologi beskriver de biologiske prosessene som skjer i levende vesener over tid. Vitenskapen om fysiologi er kompleks, men samtidig kritisk for vår forståelse av hvordan levende organismer fungerer. Fysiologi dekker en stor bredde romlig-temporale skalaer og fordrer behovet for å kombinere og bygge bro mellom basalfagene (biologi, fysikk og kjemi) og medisin. De senere årene har det vært en eksplosjon av nye, avanserte eksperimentelle metoder for å detektere og karakterisere fysiologiske data. Volumet og kompleksiteten til fysiologiske data krever effektive strategier for visualisering for å komplementere dagens standard analyser. Hvilke tilnærminger som benyttes i visualiseringen må nøye balanseres og tilpasses formålet med bruken av dataene, enten dette er for å utforske dataene, analysere disse eller kommunisere og presentere dem. Arbeidet i denne avhandlingen bidrar med ny kunnskap innen teori, empiri, anvendelse og reproduserbarhet av visualiseringsmetoder innen fysiologi. Først i avhandlingen er en rapport som oppsummerer og utforsker dagens kunnskap om muligheter og utfordringer for visualisering innen fysiologi. Motivasjonen for arbeidet er behovet forskere innen visualiseringsfeltet, og forskere i ulike anvendelsesområder, har for en sammensatt oversikt over flerskala visualiseringsoppgaver og teknikker. Ved å bruke søk over et stort spekter av metodiske tilnærminger, er dette den første rapporten i sitt slag som kartlegger visualiseringsmulighetene innen fysiologi. I rapporten er faglitteraturen oppsummert slik at det skal være enkelt å gjøre oppslag innen ulike tema i rom-og-tid-skalaen, samtidig som litteraturen er delt inn i de tre høynivå visualiseringsoppgavene data utforsking, analyse og kommunikasjon. Dette danner et enkelt grunnlag for å navigere i litteraturen i feltet og slik danner rapporten et godt grunnlag for diskusjon og forskningsmuligheter innen feltet visualisering og fysiologi. Basert på arbeidet med rapporten var det særlig to områder som det er ønskelig for oss å fortsette å utforske: (1) utforskende analyse av mangefasetterte fysiologidata for ekspertbrukere, og (2) kommunikasjon av data til både eksperter og ikke-eksperter. Arbeidet vårt av mangefasetterte fysiologidata er oppsummert i to studier i avhandlingen. Hver studie omhandler prosesser som foregår på forskjellige romlig-temporale skalaer og inneholder konkrete eksempler på anvendelse av metodene vurdert av eksperter i feltet. I den første av de to studiene undersøkes konsentrasjonen av molekylære substanser (metabolitter) ut fra data innsamlet med magnetisk resonansspektroskopi (MRS), en avansert biokjemisk teknikk som brukes til å identifisere metabolske forbindelser i levende vev. Selv om MRS kan ha svært høy sensitivitet og spesifisitet i medisinske anvendelser, er analyseresultatene fra denne modaliteten abstrakte og vanskelige å forstå også for medisinskfaglige eksperter i feltet. Vår designstudie som undersøkte oppgavene og kravene til ekspertutforskende analyse av disse dataene førte til utviklingen av SpectraMosaic. Dette er en ny applikasjon som gjør det mulig for domeneeksperter å analysere konsentrasjonen av metabolitter normalisert for en hel kohort, eller etter prøveregion, individ, opptaksdato, eller status på hjernens aktivitetsnivå ved undersøkelsestidspunktet. I den andre studien foreslås en metode for å utføre utforskende analyser av flerdimensjonale fysiologiske data i motsatt ende av den romlig-temporale skalaen, nemlig på populasjonsnivå. En effektiv arbeidsflyt for utforskende dataanalyse må kritisk identifisere interessante mønstre og relasjoner, noe som blir stadig vanskeligere når dimensjonaliteten til dataene øker. Selv om dette delvis kan løses med eksisterende reduksjonsteknikker er det alltid en fare for at subtile mønstre kan gå tapt i reduksjonsprosessen. Isteden presenterer vi i studien DimLift, en iterativ dimensjonsreduksjonsteknikk som muliggjør brukeridentifikasjon av interessante mønstre og relasjoner som kan ligge subtilt i et datasett gjennom dimensjonale bunter. Nøkkelen til denne metoden er brukerens evne til å styre dimensjonalitetsreduksjonen slik at den følger brukerens egne undersøkelseslinjer. For videre å undersøke kommunikasjon til eksperter og ikke-eksperter, studeres i neste arbeid utformingen av visualiseringer for kommunikasjon til publikum med ulike nivåer av ekspertnivå. Det er naturlig å forvente at eksperter innen et emne kan ha ulike preferanser og kriterier for å vurdere en visuell kommunikasjon i forhold til et ikke-ekspertpublikum. Dette påvirker hvor effektivt et bilde kan benyttes til å formidle en gitt scenario. Med utgangspunkt i ulike teknikker innen biomedisinsk illustrasjon og visualisering, gjennomførte vi derfor en utforskende studie av kriteriene som publikum bruker når de evaluerer en biomedisinsk prosessvisualisering målrettet for kommunikasjon. Fra denne studien identifiserte vi muligheter for ytterligere konvergens av biomedisinsk illustrasjon og visualiseringsteknikker for mer målrettet visuell kommunikasjonsdesign. Særlig beskrives i større dybde utviklingen av semantisk konsistente retningslinjer for farging av molekylære scener. Hensikten med slike retningslinjer er å heve den vitenskapelige kompetansen til ikke-ekspertpublikum innen molekyler visualisering, som vil være spesielt relevant for kommunikasjon til befolkningen i forbindelse med folkehelseopplysning. All kode og empiriske funn utviklet i arbeidet med denne avhandlingen er åpen kildekode og tilgjengelig for gjenbruk av det vitenskapelige miljøet og offentligheten. Metodene og funnene presentert i denne avhandlingen danner et grunnlag for tverrfaglig biomedisinsk illustrasjon og visualiseringsforskning, og åpner flere muligheter for fortsatt arbeid med visualisering av fysiologiske prosesser.The overarching theme of this thesis is the cross-disciplinary application of medical illustration and visualization techniques to address challenges in exploring, analyzing, and communicating aspects of physiology to audiences with differing expertise. Describing the myriad biological processes occurring in living beings over time, the science of physiology is complex and critical to our understanding of how life works. It spans many spatio-temporal scales to combine and bridge the basic sciences (biology, physics, and chemistry) to medicine. Recent years have seen an explosion of new and finer-grained experimental and acquisition methods to characterize these data. The volume and complexity of these data necessitate effective visualizations to complement standard analysis practice. Visualization approaches must carefully consider and be adaptable to the user's main task, be it exploratory, analytical, or communication-oriented. This thesis contributes to the areas of theory, empirical findings, methods, applications, and research replicability in visualizing physiology. Our contributions open with a state-of-the-art report exploring the challenges and opportunities in visualization for physiology. This report is motivated by the need for visualization researchers, as well as researchers in various application domains, to have a centralized, multiscale overview of visualization tasks and techniques. Using a mixed-methods search approach, this is the first report of its kind to broadly survey the space of visualization for physiology. Our approach to organizing the literature in this report enables the lookup of topics of interest according to spatio-temporal scale. It further subdivides works according to any combination of three high-level visualization tasks: exploration, analysis, and communication. This provides an easily-navigable foundation for discussion and future research opportunities for audience- and task-appropriate visualization for physiology. From this report, we identify two key areas for continued research that begin narrowly and subsequently broaden in scope: (1) exploratory analysis of multifaceted physiology data for expert users, and (2) communication for experts and non-experts alike. Our investigation of multifaceted physiology data takes place over two studies. Each targets processes occurring at different spatio-temporal scales and includes a case study with experts to assess the applicability of our proposed method. At the molecular scale, we examine data from magnetic resonance spectroscopy (MRS), an advanced biochemical technique used to identify small molecules (metabolites) in living tissue that are indicative of metabolic pathway activity. Although highly sensitive and specific, the output of this modality is abstract and difficult to interpret. Our design study investigating the tasks and requirements for expert exploratory analysis of these data led to SpectraMosaic, a novel application enabling domain researchers to analyze any permutation of metabolites in ratio form for an entire cohort, or by sample region, individual, acquisition date, or brain activity status at the time of acquisition. A second approach considers the exploratory analysis of multidimensional physiological data at the opposite end of the spatio-temporal scale: population. An effective exploratory data analysis workflow critically must identify interesting patterns and relationships, which becomes increasingly difficult as data dimensionality increases. Although this can be partially addressed with existing dimensionality reduction techniques, the nature of these techniques means that subtle patterns may be lost in the process. In this approach, we describe DimLift, an iterative dimensionality reduction technique enabling user identification of interesting patterns and relationships that may lie subtly within a dataset through dimensional bundles. Key to this method is the user's ability to steer the dimensionality reduction technique to follow their own lines of inquiry. Our third question considers the crafting of visualizations for communication to audiences with different levels of expertise. It is natural to expect that experts in a topic may have different preferences and criteria to evaluate a visual communication relative to a non-expert audience. This impacts the success of an image in communicating a given scenario. Drawing from diverse techniques in biomedical illustration and visualization, we conducted an exploratory study of the criteria that audiences use when evaluating a biomedical process visualization targeted for communication. From this study, we identify opportunities for further convergence of biomedical illustration and visualization techniques for more targeted visual communication design. One opportunity that we discuss in greater depth is the development of semantically-consistent guidelines for the coloring of molecular scenes. The intent of such guidelines is to elevate the scientific literacy of non-expert audiences in the context of molecular visualization, which is particularly relevant to public health communication. All application code and empirical findings are open-sourced and available for reuse by the scientific community and public. The methods and findings presented in this thesis contribute to a foundation of cross-disciplinary biomedical illustration and visualization research, opening several opportunities for continued work in visualization for physiology.Doktorgradsavhandlin