diplomsko delo
Povzetek
Uvod: Slikanje z magnetno resonanco (MR) je slikovna metoda, ki je zaradi kompleksnosti precej dovzetna za nastanek popačenj. Na sliki se izražajo v obliki vzorcev ali objektov, ki lahko prekrijejo, prislikajo ali preslikajo patologijo oz. pomembne diagostične informacije. Popačenja nastajajo zaradi več razlogov, večino pa je mogoče hitro prepoznati in odstraniti, ali pa vsaj zmanjšati njihov učinek. Namen: Opisati in sistematično razvrstiti najpogostejša MR popačenja ter v pregledni obliki predstaviti tehnike njihovega odpravljanja oz. zmanjševanja, s primerjavo različnih tehnik ugotoviti, katere so za posamezna popačenja najučinkovitejše. Metode dela: S pregledom literature in deskriptivno metodo opisati najpogostejša MR popačenja. Retrogradni pregled MR slik s popačenji s PACS sistemom v UKC Ljubljana. Pregled literature z DiKUL, Pubmed, Pubmed CENTRAL in ScienceDirect podatkovnimi bazami. Rezultati: Popačenja zaradi gibanja se največkrat zmanjšuje s fiksacijo pacienta, uporabo dodatnih saturacijskih polj in tehnik za izravnavo pretoka. Popačenje preslikave rešujemo s povečanjem pregledovalnega polja in uporabo tehnik zmanjševanja preslikave, ko so na primer No Phase Wrap, Phase Oversampling. Popačenjem zaradi magnetne dovzetnosti se izogibamo z uporabo krajših časov odmeva, uporabo hitrejših pulznih zaporedij in tanjših rezin. Kovinska popačenja preprečimo z ustrezno pripravo pacienta na preiskavo, pri kovinskih implantatih pa uporabimo protokol Metal Artifact Reduction Sequence – MARS. Če poskrbimo, da se rezine ne križajo v spinalnem kanalu, ali pa vzbujamo lihe in sode rezine izmenično, se izognemo tudi popačenjem zaradi križanja rezin. Kemijski premik zmanjšamo z uporabo širše pasovne širine, povečanju slikovnega polja in zasičenjem signala iz protonov maščobe. Popačenju zadrge se izognemo tako, da tesno zapremo vrata diagnostične sobe. Gibbsovem popačenju se izogibamo z uporabo filtrov za glajenje v k prostoru. Razprava in zaključek: Znane so številne tehnike zmanjševanje MR popačenj, ki so pri tem bolj ali manj uspešne. Pri delu z MR je ključna naloga radioloških inženirjev prepoznavanje popačenj, vzrokov njihovega nastanka in načinov njihovega odpravljanja oz. zmanjševanja. Upoštevajoč vzroke nastanka popačenj, se tako lažje odločimo za uporabo najprimernejše tehnike zmanjševanja v dani situaciji.
Ključne besede
diplomska dela;radiološka tehnologija;magnetna resonanca;popačenje;zmanjševanje;preslikave;susceptibilnost;kovine;kemijski premik;pulzna zaporedja;
Podatki
Jezik: |
Slovenski jezik |
Leto izida: |
2019 |
Tipologija: |
2.11 - Diplomsko delo |
Organizacija: |
UL ZF - Zdravstvena fakulteta |
Založnik: |
[Ž. Bajc |
UDK: |
616-07 |
COBISS: |
5685867
|
Št. ogledov: |
759 |
Št. prenosov: |
308 |
Ocena: |
0 (0 glasov) |
Metapodatki: |
|
Ostali podatki
Sekundarni jezik: |
Angleški jezik |
Sekundarni naslov: |
Overview of the most common magnetic resonance artifacts and methods of correction |
Sekundarni povzetek: |
Introduction: Due to its complexity, the magnetic resonance imagining (MR) is susceptible to artifacts. They can appear in MR images as different shapes or objects. Some of them can seriously affect diagnostic image quality, while others may simulate or be confused with different pathology. Artifacts are caused by various factors, and most of them can be identified and eliminated quickly and effectively. If elimination is not possible, some methods allow radiographers to reduce negative influence on MR images. Purpose: To describe and systematically classify the most common MR artifacts, to present an overview of mitigation and correction methods, and to determine which method is the most appropriate for remedying each type of artifact. Methods: The thesis presents an overview of the most common MR artifacts based on literature review and descriptive research. We analyzed MR scans, corrupted with already identified artifacts, using a picture archiving and communication system (PACS), used by Ljubljana Medical Center. We reviewed literature, found in DiKUL, Pubmed, Pubmed CENTRAL and ScienceDirect databases. Results: Motion artifacts are usually reduced by fixation with straps, by using series of additional saturation pulses, and by flow compensation technique. Aliasing artifacts can be eliminated by increasing the field of view. Alternatively, they can also be prevented by anti-aliasing techniques, such as no-phase wrap and phase oversampling. Approaches to minimizing susceptibility artifacts include shortening the echo time, the use of faster pulse sequences and the use of thinner slices. Metal artifacts can be avoided by proper patient preparation before the MR procedure. When metallic implants are present in the MR examination, their impact should be minimalized by a metal artifact reduction sequence (MARS). To reduce the slice-overlap artifact, radiographers should ensure that the slices do not overlap in the spinal canal. Alternatively, they could acquire the odd slices first and then the even slices. Chemical shift artifacts can be alleviated by increasing the receiver bandwidth or the field of view, and by fat saturation. Zipper artifact can be avoided by ensuring that the scanner room door is shut during imaging. Gibbs-ringing artifacts are reduced by high pass filter that removes the low spatial frequencies from k-space. Discussion and conclusion: MR artifacts can be alleviated or eliminated by numerous methods of varying success. To optimize clinical image quality, it is crucial that radiographers understand the causes of artifacts, their characteristics, and mitigation and correction methods, so that they opt for the most appropriate method for alleviating each type of artifact. |
Sekundarne ključne besede: |
diploma theses;radiologic technology;magnetic resonance;artifact;reducing;aliasing;susceptibility;metals;chemical shift;pulse sequences; |
Vrsta dela (COBISS): |
Diplomsko delo/naloga |
Študijski program: |
0 |
Komentar na gradivo: |
Univ. v Ljubljani, Zdravstvena fak., Oddelek za radiološko tehnologijo |
Strani: |
31 str. |
ID: |
11224121 |