Numerická studie proveditelnosti mikrovlnného neinvazivního sledování vývoje hypoxicko-ischemické encefalopatie u novorozenců

Abstract

Tato diplomov ́a pr ́ace se zab ́yv ́a numerickou studi ́ı proveditelnosti mikrovlnn ́eho zobrazovac ́ıho syst ́emu pro monitorov ́an ́ı v ́yvoje hypoxicko-ischemick ́e encefalopatie u novorozenc ̊u. Studie proveditelnosti byla provedena vyuˇzit ́ım softwaru COMSOL Multiphysics pro numerick ́e simulace a softwaru MATLAB pro rekonstrukci obrazu s vyuˇzit ́ım principu diferenˇcn ́ıho zobrazov ́an ́ı zaloˇzen ́eho na Bornovˇe aproximaˇcn ́ı metodˇe. Z 1D analytick ́eho modelu koeficientu pˇrenosu EM vln skrze v ́ıcevrstevnat ́e prostˇred ́ı reprezentuj ́ıc ́ı novorozeneckou hlavu byly odvozeny 4 hodnoty relativn ́ı permitivity pˇrizp ̊usobovac ́ı kapaliny (15, 25, 35 a 45). Pro tyto permitivity byly testov ́any pˇrenosov ́e koeficienty a zobrazovac ́ı schopnosti 2D syst ́em ̊u s anatomicky pˇresnou geometri ́ı transverz ́aln ́ıho ˇrezu hlavy novorozence spoleˇcnˇe s anatomicky vˇern ́ymi ischemick ́ymi patologiemi nalezen ́ymi v literatuˇre. Na z ́akladˇe tˇechto anal ́yz byla urˇcena optim ́aln ́ı pracovn ́ı frekvence 2 a 2,5 GHz a relativn ́ı permitivita pˇri-zp ̊usobovac ́ı kapaliny 45. Pro potˇreby 3D zobrazovac ́ıch syst ́em ̊u byl impedanˇcnˇe pˇrizp ̊usoben H-slotov ́y ant ́enn ́ı element pro frekvenˇcn ́ı p ́asmo 2 aˇz 2,7 GHz. D ́ale byly vytvoˇreny 3D zobrazovac ́ı syst ́emy s anatomicky vˇern ́ym modelem hlavy a ischemick ́ymi patologiemi. Na z ́akladˇe v ́ysledk ̊u 3D rekonstrukc ́ı kulov ́e ischemie byl vybr ́an nejlepˇs ́ı zobrazovac ́ı syst ́em, pro kter ́y byly rekonstruov ́any zbyl ́e ischemick ́e patologie. V diskuzi t ́eto pr ́ace byly vyhodnoceny aplikaˇcn ́ı moˇznosti mikrovlnn ́eho zobrazov ́an ́ı v problematice monitorov ́an ́ı v ́yvoje hypoxicko-ischemick ́e encefalopa-tie. V ́ysledky t ́eto diplomov ́e pr ́ace naznaˇcuj ́ı, ˇze by takov ́yto mikrovlnn ́y zobrazovac ́ı syst ́em mohl pomoci s monitorov ́an ́ım a terapi ́ı hypoxicko-ischemick ́e encefalopatie, kter ́a tvoˇr ́ı v ́yznamnou pˇr ́ıˇcinu ́umrtnosti nebo tˇeˇzk ́eho neurologick ́eho poˇskozen ́ı u novorozenců

This master’s thesis deals with a numerical feasibility study of microwave imaging system for monitoring hypoxic-ischemic encephalopathy in newborns. The feasibility study was carried out using COMSOL Multiphysics software for numerical simulations and MATLAB for image reconstruction using differential imaging based on Born’s approximation. From 1D analytical model of transmission coefficient EM waves through multilayer domain representing newborn’s head, 4 relative permittivities of matching medium were determined (15, 25, 35, 45). For those permittivities, the transmission coefficients and imaging capabilities of 2D systems were tested on anatomically accurate transversal cut of neonatal head together and anatomically correct ischemic pathologies found in literature. Based on those analysis, the optimal working frequency of 2 and 2,5 GHz and relative permittivity of matching medium of 45 were determined. For the purpose of 3D imaging system, H-slot antenna was impedance matched for frequency range from 2 to 2,7 GHz. Next, 3D imaging systems with anatomically correct head model and ischemic pathologies were created. On the basis of 3D reconstructions of spherical ischemic lesion the best imaging system was chosen, for which the rest of the ischemic pathologies were reconstructed. The application options of microwave imaging for monitoring of development of hypoxicischemic encephalopathy were debated about in the discussion. The results of this work suggest that such microwave imaging system would help in the monitoring and treatment of hypoxic-ischemic encephalopathy which is the significant cause of mortality or severe neurologic disability in newborn children.