MRI Radial K-Space Sampling for Cerebral Perfusion Quantification
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for quantifying cerebral vascular reserve (CVR) are limited by the need for radioactive tracers, high radiation doses, and coarse spatial resolution in MRI-based systems, making it difficult to accurately assess perfusion and identify patients who would benefit from interventions for cerebrovascular diseases like ischemic stroke.
Innovation Solution
An MRI-based system employing a 3D pulse sequence with radial k-space sampling and a self-calibration technique to quantify cerebral blood volume (CBV) and perfusion, using a stress challenge to calculate CVR as (Stress−Rest)/Rest×100%, allowing for precise imaging and scoring of vascular reserve without radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PET imaging with radio-labeled tracers is used to quantify cerebral perfusion, then measurement precision is improved, but device complexity and availability are worsened due to the requirement of a cyclotron
Solution Approach 1:
The patent replaces the complex mechanical system of a cyclotron with an MRI scanner using paramagnetic contrast agents. The MRI system with dynamic susceptibility contrast (DSC) imaging provides quantitative cerebral perfusion measurements without requiring radioactive tracer production facilities, thereby substituting a mechanically complex system with a more accessible imaging modality while maintaining measurement precision.
Solution Approach 2:
The patent changes the measurement parameters from radioactive tracer concentration (PET) to paramagnetic contrast agent signal intensity (MRI). By using the T2* relaxation effects of paramagnetic agents like gadolinium and analyzing the signal decay characteristics, the system achieves quantitative perfusion measurement through different physical parameters, eliminating the need for cyclotron-based tracer production.
2Measurement precision
If CT perfusion imaging is used, then quantification capability is improved, but object-affected harmful factors worsen due to large radiation doses and iodinated contrast agents
Solution Approach 1:
The patent substitutes CT imaging with MRI imaging for perfusion quantification. MRI using paramagnetic contrast agents does not involve ionizing radiation, thereby eliminating the harmful radiation effects associated with CT while maintaining the capability for quantitative perfusion measurement through analysis of T2* signal changes during contrast bolus passage.
Solution Approach 2:
The patent uses paramagnetic contrast agents as an intermediary substance that provides signal modulation in MRI without causing radiation damage. These agents temporarily alter the magnetic properties of blood and tissue, enabling perfusion quantification through T2* weighting while avoiding the harmful effects of both radiation (CT) and radioactivity (PET).
3Manufacturing precision
If conventional MRI pulse sequences are used, then spatial resolution is improved, but productivity worsens due to long acquisition times
Solution Approach 1:
The patent employs periodic sampling of k-space during the passage of the contrast agent bolus. By acquiring data at multiple time points as the bolus passes through different vascular beds, the system reconstructs dynamic perfusion information from periodic measurements, achieving both high spatial resolution and adequate temporal sampling without excessively long acquisition times.
Solution Approach 2:
The patent performs preliminary localization and timing of the contrast agent injection before the actual perfusion imaging sequence. By pre-positioning the imaging parameters and triggering the acquisition sequence based on the expected bolus arrival time, the system optimizes the timing of data collection to capture the perfusion dynamics at appropriate moments, improving both resolution and acquisition efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides high-resolution, radiation-free quantification of cerebral perfusion and CVR, enabling more accurate assessment of vascular reserve and guiding treatment decisions for cerebrovascular diseases.
Implementation Method 1
When a substance such as human tissue is subjected to a uniform magnetic field (polarizing field B0), the individual magnetic moments of the spins in the tissue attempt to align with this polarizing field, but precess about it in random order at their characteristic Larmor frequency. If the substance, or tissue, is subjected to a magnetic field (excitation field B1) which is in the x-y plane and which is near the Larmor frequency, the net aligned moment, Mz, may be rotated, or 'tipped', into the x-y plane to produce a net transverse magnetic moment Mt. A signal is emitted by the excited spins after the excitation signal B1 is terminated
Implementation Method 2
Perfusion weighted images (PWI) show the degree to which tissues are perfused by the change in their brightness as a bolus of contrast agent washes through the vasculature
Data Source
AI summary
In one aspect of the disclosure, an MRI-based system includes an MRI scanner having a first axis and a first plane perpendicular to the first axis, a pulse sequence module configured to provide a 3D pulse sequence to the MRI scanner, and a control module configured to instruct the MRI scanner to conduct radial k-space samples having N second planes that each are perpendicular to the first plane and through which the first axis passes, N being an integer greater than 1. The 3D pulse sequence instructs the MRI scanner to a radio-frequency (RF) pulse, conduct a gradient readout in the first plane, and conduct a gradient readout in one of the N second planes.