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Tracer arrival timing-insensitive technique for estimating flow in MR perfusion-weighted imaging using singular value
Ona Wu1, Leif Østergaard, Robert M Weisskoff
1Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital/Massachusetts Institute of Technology/Harvard Medical School, Boston, Massachusetts 02129, USA. ona@nmr.mgh.harvard.edu
Magnetic Resonance in Medicine
|June 20, 2003
Summary
This study introduces novel methods for Magnetic Resonance Perfusion-Weighted Imaging (PWI) to improve accuracy. The new techniques, oscillating Singular Value Decomposition (oSVD) and circulant Singular Value Decomposition (cSVD), offer time-shift insensitive estimates of cerebral blood flow (CBF).
Area of Science:
- Neuroimaging
- Medical Physics
- Radiology
Background:
- Bolus-tracking MR Perfusion-Weighted Imaging (PWI) estimates of relative cerebral blood flow (CBF) and mean transit time (MTT) are sensitive to timing delays and dispersion.
- Standard Singular Value Decomposition (SVD) methods using a single arterial input function (AIF) can lead to inaccurate results due to these timing variations.
Purpose of the Study:
- To develop and evaluate time-shift insensitive deconvolution techniques for PWI.
- To compare the performance of oscillating SVD (oSVD) and circulant SVD (cSVD) against standard SVD (sSVD) in numerical simulations and clinical data.
Main Methods:
- Implementation of a block-circulant matrix for deconvolution, with and without oscillation minimization (oSVD and cSVD).
- Comparison of oSVD, cSVD, and sSVD using numerical simulations and clinically acquired PWI data.
- Introduction of an "oDelay" index to quantify tracer arrival time differences between AIF and tissue.
Main Results:
- PWI estimates from sSVD are significantly influenced by tracer arrival time differences, unlike oSVD and cSVD.
- oSVD demonstrates reduced sensitivity to blood volume variations compared to cSVD.
- The proposed oSVD method provides reliable, timing-insensitive CBF estimates.
Conclusions:
- oSVD and cSVD offer significant improvements over sSVD by eliminating sensitivity to tracer arrival time differences.
- oSVD is a promising technique for routine clinical PWI, providing more specific indicators of ischemic injury.
- Shift maps remain valuable for detecting disturbed hemodynamics.