Fizikalne osnove oslikavanja magnetskom rezonancijom

master's thesis

• Title (english): Physical basis of magnetic resonance imaging
• Author: Vedran Župančić
• Mentor: Sanja Dolanski-Babić (mentor)
• Committee member: Ozren Gamulin (predsjednik povjerenstva)
• Committee member: Mislav Čavka (član povjerenstva)
• Committee member: Sanja Dolanski-Babić (član povjerenstva)
• Granter: University of Zagreb; School of Medicine; (Department of Physics and Biophysics); Zagreb
• Defense date and country: 2017-07-14, Croatia
• Scientific / art field, discipline and subdiscipline: BIOMEDICINE AND HEALTHCARE; Clinical Medical Sciences

Abstract

Oslikavanje magnetskom rezonancijom je radiološka tehnika oslikavanja. Za dobivanje slike koriste se uređaji sa snažnim magnetskim poljima od 0,2 do 7 T, izvorima elektromagnetskih valova i gradijenata magnetskog polja. Osnova za dobivanje signala je interakcija između magnetskih momenata vodikovih atoma i energije elektromagnetskih valova iz radiofrekventnog spektra (RF pulsa). Tijelo koje se oslikava stavlja se u vanjsko magnetsko polje koje u njemu izaziva pojavu longitudinalne magnetizacije. Nakon toga se primjenjuje RF puls koji zakreće os magnetizacije u ravninu koja je okomita na vanjsko magnetsko polje i ta se magnetizacija naziva transverzalna magnetizacija. Zbog toga signal koji nastaje u tijelu postaje mjerljiv. Nakon prestanka RF pulsa magnetizacija se vraća u stanje svoje prvotne orijentacije. Taj proces vraćanja u početno stanje se naziva relaksacija. Imamo dvije vrste relaksacije, T1 i T2, a one su osnovni parametri za dobivanje krajnje slike. Ovisno o duljini trajanja relaksacije imat ćemo različite signale i različiti slikovni prikaz tkiva u tijelu. Različitim trajanjem RF pulsa dobivat ćemo slike koje se više oslanjaju na T1 ili T2 parametre i na taj način ćemo moći bolje razlikovati oslikavana tkiva. Lokalizacija izvora signala iz tijela se postiže gradijentnim poljima. Magnetska rezonancija je neionizirajuća pretraga koja jako unaprjeđuje dijagnostičke mogućnosti. Jedina kontraindikacija za ovu vrstu pretrage su metalni umetci koji mogu uzrokovati veliku štetu na tkivu prilikom oslikavanja. Napredne mogućnosti u prikazu tkiva daju oslikavanju magnetskom rezonancijom nezamjenjivu ulogu u modernoj medicini.

Abstract (english)

Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology. For producing a picture MRI scanners use strong magnetic fields from 0.2 to 7 Tesla, electromagnetic waves and field gradients.The basic principle for getting a signal is the interaction between magnetic moments of hydrogen atoms and energy from electromagnetic pulse in the radio frequency spectrum (RF pulse). The body is placed into a strong magnetic field which induces longitudinal magnetization in the body. Then we apply a RF pulse which tilts magnetization into a plane that is perpendicular to our external magnetic field and that magnetization is now called trasnversal magnetisation. The signal that is arising from the body now becomes measurable. After the application of RF pulse, tilted magnetization starts to return to its steady state. Because the magnetization in motion induces electric currency, we are able to measure the signal. That process of magnetization returning to steady state is called relaxation. We have two types of relaxation, T1 and T2, and those are parameters that affect the outcome of the final image. Depending on how long the relaxations are, we will have different signal and also the different image from different tissues. Combining different energy or duration of the RF pulse we can alter the picture result so it will be more in the area of T1 or T2 relaxation. Those areas of relaxation are called T1-weighted or T2-weighted images and help us in better differentiation of the tissues. Localisation of the signal arising from the body is done through gradient magnetic fields. Magnetic resonance imaging is a non-ionising procedure which vastly improves our opportunities for better diagnostics. The only contraindications to this type of imaging are non-removable metal implants. The advanced functionality of MRI in body imaging gives it a irreplaceable role in modern medicine.

• Keywords: oslikavanje magnetskom rezonancijom; RF puls; T1 relaksacija; T2 relaksacija; gradijenti polja; metalni umetci; neionizirajuća pretraga
• Keywords (english): magnetic resonance imaging; RF pulse; T1 relaxation; T2 relaxation; gradient fields; metal implants; non-ionising procedure
• Language: croatian
• URN:NBN: urn:nbn:hr:105:409172
• Study programme: Title: Medicine; Study programme type: university; Study level: integrated undergraduate and graduate; Academic / professional title: doktor/doktorica medicine (doktor/doktorica medicine)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2017-11-28 13:13:51