Reduction of Noise and Artefacts in MRIScan of Metal Implant Reconstructed by Frequency Mapping
(2022) BMEM01 20221Department of Biomedical Engineering
- Abstract (Swedish)
- Metal objects can cause significant artefacts in magnetic resonance imaging (MRI) scans, cause loss of signal and what is known as geometric warping. There are ways to address these problems using different MRI sequences. This project looks at a newer method of artefact correction proposed by Månsson and Morin.
The aim is to improve upon the main two faults of the method. The method makes use of a frequency map taken alongside the image dataset which describes the warping of the magnetic field caused by the metal object. This frequency map is then used to estimate how far data should be shifted back to correct for the geometric warping. The data is then shifted back using Fourier Shift. The main limitations of the method are a noticeable... (More) - Metal objects can cause significant artefacts in magnetic resonance imaging (MRI) scans, cause loss of signal and what is known as geometric warping. There are ways to address these problems using different MRI sequences. This project looks at a newer method of artefact correction proposed by Månsson and Morin.
The aim is to improve upon the main two faults of the method. The method makes use of a frequency map taken alongside the image dataset which describes the warping of the magnetic field caused by the metal object. This frequency map is then used to estimate how far data should be shifted back to correct for the geometric warping. The data is then shifted back using Fourier Shift. The main limitations of the method are a noticeable increase in noise present in the image post correction as well as the unexpected appearance of zebra-stripe artefacts.
The improvements are made from two parts: filtering and interpolation. These methods were tested on both synthetic datasets generated using MATLAB, as well as a previously created phantom.
By filtering the frequency map using a three-dimensional median filter prior to applying the correction method, the noise could be reduced by about a factor 2 in the final image. Additionally, interpolating both datasets prior to applying the method caused a significant reduction to the zebra-stripe artefacts. (Less) - Popular Abstract (Swedish)
- Brusreduktion i ny Metod att Korrigera MR-bilder
MR-bildtagning är en viktig undersökningsmetod då den kan säkert och effektivt upptäcka problem inuti en patient som annars är svåra att finna. Tyvärr är MR en väldigt tidskrävande process, speciellt när patienter har implanterade metallobjekt. Detta examensarbete förbättrar en ny och lovande metod att snabbare ta och korrigera MR bilder tagna i närheten av metall.
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9075377
- author
- Wahlqvist, Pontus LU
- supervisor
- organization
- course
- BMEM01 20221
- year
- 2022
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- additional info
- 2022-03
- id
- 9075377
- date added to LUP
- 2022-02-15 14:50:34
- date last changed
- 2022-02-15 14:50:34
@misc{9075377, abstract = {{Metal objects can cause significant artefacts in magnetic resonance imaging (MRI) scans, cause loss of signal and what is known as geometric warping. There are ways to address these problems using different MRI sequences. This project looks at a newer method of artefact correction proposed by Månsson and Morin. The aim is to improve upon the main two faults of the method. The method makes use of a frequency map taken alongside the image dataset which describes the warping of the magnetic field caused by the metal object. This frequency map is then used to estimate how far data should be shifted back to correct for the geometric warping. The data is then shifted back using Fourier Shift. The main limitations of the method are a noticeable increase in noise present in the image post correction as well as the unexpected appearance of zebra-stripe artefacts. The improvements are made from two parts: filtering and interpolation. These methods were tested on both synthetic datasets generated using MATLAB, as well as a previously created phantom. By filtering the frequency map using a three-dimensional median filter prior to applying the correction method, the noise could be reduced by about a factor 2 in the final image. Additionally, interpolating both datasets prior to applying the method caused a significant reduction to the zebra-stripe artefacts.}}, author = {{Wahlqvist, Pontus}}, language = {{eng}}, note = {{Student Paper}}, title = {{Reduction of Noise and Artefacts in MRIScan of Metal Implant Reconstructed by Frequency Mapping}}, year = {{2022}}, }