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"Squashing peanuts and smashing pumpkins": how noise distorts diffusion-weighted MR data
Derek K Jones1, Peter J Basser
1Section on Tissue Biophysics and Biomimetics, Laboratory of Integrative Medicine and Biophysics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-5772, USA. jonesde@mail.nih.gov
Magnetic Resonance in Medicine
|October 28, 2004
Summary
New MRI techniques reveal artifacts caused by background noise in diffusion-weighted imaging (DWI). These noise-induced artifacts, particularly at high b-values, can distort diffusion measurements but are minimal in standard diffusion tensor MRI (DT-MRI).
Area of Science:
- Magnetic Resonance Imaging (MRI)
- Biomedical Engineering
- Neuroimaging
Background:
- Advanced diffusion-weighted imaging (DWI) methods aim to capture non-Gaussian diffusion properties beyond conventional diffusion tensor MRI (DT-MRI).
- Increasing diffusion weighting or spatial resolution in DWI can decrease signal-to-noise ratio, making signals susceptible to background noise.
- Understanding noise effects is crucial for accurate interpretation of complex diffusion metrics.
Purpose of the Study:
- To identify and characterize novel artifacts in diffusion-weighted imaging (DWI) arising from background noise.
- To explain how background noise influences the apparent diffusion coefficient (ADC) profile and diffusion anisotropy measurements.
- To assess the impact of these artifacts on specific clinical applications like acute ischemia and compare them with standard DT-MRI.
Main Methods:
- Analysis of diffusion-weighted imaging (DWI) data, focusing on the apparent diffusion coefficient (ADC) profile at various b-values.
- Investigated the effects of background noise on orientation-dependent ADC behavior and diffusion anisotropy indices.
- Evaluated noise-induced artifacts in simulated and real-world data, including comparisons between high b-value DWI and standard DT-MRI (b ≈ 1000 s mm(-2)).
Main Results:
- Identified several new artifacts, including orientation-dependent ADC deviations and underestimation of diffusion anisotropy, linked to background noise.
- Observed noise-induced increases in gray/white matter contrast at higher b-values and apparent diffusion anisotropy elevation in acute ischemia.
- Demonstrated that these artifacts are negligible at the b-values commonly used in brain DT-MRI (b ≈ 1000 s mm(-2)).
Conclusions:
- Background noise introduces significant artifacts in high b-value DWI, affecting the accuracy of diffusion measurements and anisotropy indices.
- Standard DT-MRI (b ≈ 1000 s mm(-2)) is largely unaffected by these specific noise-related artifacts.
- A strategy was demonstrated to mitigate noise artifacts in high b-value DWI data, improving data reliability.