Optimisation of T2 and M0 measurements of bi-exponential systems.
Abstract: Cramer-Rao theory and computer simulations were used to show that the errors involved in calculating the magnetization and relaxation parameters of a two-component system decrease with: (1) increasing SNR, (2) increasing number of echoes used in the fitting procedure, and (3) increasing ratio of the relaxation times of the two components, T(22)/T(21). Images of bi-compartmental phantoms of known T(2) values were acquired using an optimized imaging sequence, and an optimized fitting algorithm was used to calculate the T(2) values of the two components by fitting the resulting images to a bi-exponential decay model. Accuracy better than 6% was achieved in the calculations of the T(2) values of the two components, and region fitting provided better accuracy than pixel-by-pixel fitting. The procedures were used to calculate the T(2) and M(0) values of equine carpal bones with known degree of radiographic bone sclerosis. Although the T(2) and M(0) values of both water and fat components all decreased with the degree of radiographic bone sclerosis, the transverse relaxation of the water component, T(2W), showed a greater decrease with advanced stages of bone sclerosis.
Publication Date: 2004-02-20 PubMed ID: 14972396DOI: 10.1016/j.mri.2003.05.005Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research article is an investigation into the optimization of T2 and M0 measurements of two-component systems. By utilizing Cramer-Rao theory and computer simulations, the researchers demonstrate that increased accuracy in magnetization and relaxation parameters can be achieved through improvements in signal-to-noise ratio, increased echo usage during fitting, and augmenting the ratio of the two component’s relaxation times.
Research Methodology
- The researchers used Cramer-Rao theory and computer simulations to understand the error rates involved in calculating magnetization and relaxation parameters in two-component systems.
- Findings show that the errors in these calculations decrease with an increase in Signal-to-Noise Ratio (SNR), an increase in the number of echoes used during the fitting procedure, and increasing the ratio of the two components’ relaxation times – loosely defined as T(22)/T(21).
Experimental Approach
- Bi-compartmental phantom images with known T(2) values were captured using a specially optimized imaging sequence for verification of the computations.
- An optimized fitting algorithm was deployed to calculate the T(2) values of these two components. They achieved this by fitting the resulting images into a bi-exponential decay model.
- The researchers achieved a higher than usual accuracy of 6% in calculating the T(2) values of these components. Subsequently, the researchers found that region fitting provided more accurate results compared to pixel-by-pixel fitting methods.
Application to Equine Carpal Bones
- The method described was then applied to investigating the T(2) and M(0) values of equine carpal bones with a known level of radiographic bone sclerosis.
- This method of research helped establish that both the water component and the fat component values of T(2) and M(0) decreased with a higher degree of bone sclerosis.
- The transverse relaxation of the water component, or T(2W), showed a significant decrease at advanced stages of bone sclerosis. In other words, as bone sclerosis became more severe, there was a substantial drop in T(2W).
Cite This Article
APA
Anastasiou A, Hall LD.
(2004).
Optimisation of T2 and M0 measurements of bi-exponential systems.
Magn Reson Imaging, 22(1), 67-80.
https://doi.org/10.1016/j.mri.2003.05.005 Publication
Researcher Affiliations
- Herchel Smith Laboratory for Medical Chemistry, University of Cambridge, School of Clinical Medicine, Robinson Way, Cambridge, England, CB2 2PZ, United Kingdom. T.Anastasiou@cantab.net
MeSH Terms
- Animals
- Bone Diseases / pathology
- Computer Simulation
- Horses
- Magnetic Resonance Imaging / methods
- Phantoms, Imaging
- Sclerosis
Citations
This article has been cited 22 times.- Regulski PA, Zielinski J, Borucki B, Nowinski K. A Weighted Stochastic Conjugate Direction Algorithm for Quantitative Magnetic Resonance Images-A Pattern in Ruptured Achilles Tendon T2-Mapping Assessment.. Healthcare (Basel) 2022 Apr 23;10(5).
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