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Author:Lajunen, Atte
Title:Dynaaminen ja MRI-optinen fantomi lähi-infrapunakuvantamiseen
Dynamic and MRI-Optical Phantom for Near Infrared Spectroscopic Imaging
Publication type:Master's thesis
Publication year:2010
Pages:53      Language:   fin
Department/School:Informaatio- ja luonnontieteiden tiedekunta
Main subject:Lääketieteellinen tekniikka   (Tfy-99)
Supervisor:Ilmoniemi, Risto
Instructor:Nissilä, Ilkka ; Kotilahti, Kalle
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  107   | Archive
Keywords:near infrared spectroscopic imaging
phantoms
dynamic
magnetic resonance imaging
optical
lähi-infrapunakuvantaminen
fantomit
dynaaminen
magneettikuvantaminen
optinen
Abstract (eng): Near infrared spectroscopic imaging (NIRSI) is a non-invasive imaging modality, which is based on a relatively low attenuation of a near infrared light in tissue and different optical properties of different tissues.
Infrared light interacts with tissue mostly by absorption and scattering.
The aim of NIRSI is to determine the absorption and scattering parameters of tissue or their changes in time in different areas.
Functional near infrared spectroscopic imaging is based on the changes in blood volume and oxygenation, which are connected with brain activity through the so called hemodynamic coupling.

Phantoms are artificial objects that are used for, for example, quality and calibration measurements.
In this thesis, two phantoms were manufactured: a dynamic and an MRI-optical.
The dynamic phantom was made to study the effects of systemic slow oscillations, heart pulsation and aliasing on signals from the hemodynamic responses.
With the help of the MRI-optical phantom, the use of priori information to improve the quality of optical reconstruction was studied.

The dynamic phantom was found to be suitable for simulating the needed phenomena.
The changes induced by the movement of different perturbations representing the different phenomena were clearly detectable in the signal.
With the help of the MRI-optical phantom, it was concluded that the priori information clearly improved the contrast and the speed of the optical reconstruction.
Abstract (fin): Lähi-infrapunakuvantaminen (NIRSI) on ei-invasiivinen kuvantamismenetelmä, joka perustuu lähi-infrapunavalon suhteellisen heikkoon vaimenemiseen kudoksessa ja eri kudosten erilaisiin optisiin ominaisuuksiin.
Infrapunavalo vuorovaikuttaa kudoksen kanssa absorboitumalla ja siroamalla.
NIRSI:n tavoitteena onkin määrittää kudoksen absorptio- ja sirontaparametrit tai niiden muutokset ajan funktiona eri alueilla.
Toiminnallinen lähi-infrapunakuvantaminen perustuu veren määrän ja happipitoisuuden määrittämiseen, mitkä ovat yhteydessä eri aivoalueiden aktiivisuuteen niin sanotun hemodynaamisen kytkennän kautta.

Fantomit ovat keinotekoisia kappaleita, joita käytetään esimerkiksi laadunvarmistusja kalibraatiomittauksiin.
Tässä työssä toteutettiin kaksi fantomia: dynaaminen ja MRI-optinen.
Dynaaminen fantomi valmistettiin, jotta voidaan tutkia systeemisten hitaiden oskillaatioiden, sykkeen ja aliasoitumisen vaikutusta hemodynaamisista vasteista aiheutuviin signaaleihin.
MRI-optisen fantomin avulla tutkittiin priori-tiedon käyttämistä parantamaan optisen rekonstruktion laatua.

Dynaamisen fantomin havaittiin soveltuvan hyvin haluttujen ilmiöiden simuloimiseen.
Mittaussignaalissa näkyi selkeästi eri ilmiöitä kuvaavien perturbaatioiden aiheuttamat muutokset optisissa ominaisuuksissa.
MRI-optisen fantomin avulla havaittiin, että priori-tiedon käyttö parantaa selkeästi optisen rekonstruktion kontrastia ja nopeutta.
ED:2010-08-12
INSSI record number: 40085
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