Choroid Plexus AIF Measurement for Consistent Perfusion MRI
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Solution Overview
Problem
Current methods for determining arterial input function (AIF) in perfusion magnetic resonance imaging (MRI) are prone to errors due to signal variations from the middle cerebral artery (MCA), leading to inconsistent evaluation of perfusion metrics and inability to calculate absolute hemodynamic values.
Innovation Solution
Determine the AIF based on magnetic signals from the choroid plexus (CP) using a contrast agent, such as gadolinium-based or deoxyhemoglobin, by inducing concentration changes and measuring magnetic signals to compute the AIF accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the arterial input function is derived from the middle cerebral artery using conventional MRI methods, then the measurement can be obtained, but the measurement precision is reduced due to signal variations from adjacent tissues and peak truncation effects
Solution Approach 1:
The patent extracts the AIF measurement from the conventional MCA location and relocates it to the choroid plexus. This extraction removes the harmful influence of adjacent tissue overlap and volume averaging effects that plague MCA-based measurements, thereby improving both precision and reliability of AIF evaluation.
Solution Approach 2:
The choroid plexus serves as an intermediary structure that provides a cleaner signal source for AIF determination. By using the CP as a mediator between the contrast agent bolus and the measurement system, the patent eliminates direct contamination from surrounding brain tissues and venous structures, resulting in more reliable perfusion metric calculations.
2Measurement precision
If conventional AIF determination methods are used from the MCA, then relative hemodynamic values can be determined, but absolute hemodynamic values cannot be accurately calculated due to signal saturation and non-linearity
Solution Approach 1:
The patent extracts the measurement location from the MCA to the choroid plexus, where the signal profile is less confounded by peak truncation and contrast agent non-linearity. This enables accurate determination of absolute hemodynamic values while maintaining a relatively simple imaging and processing approach.
3Adaptability or versatility
If the AIF signal is measured over the middle cerebral artery, then the arterial input function can be obtained, but the signal profile varies with voxel location and overlap with adjacent tissues
Solution Approach 1:
The patent extracts the AIF measurement from the MCA voxel-based approach and relocates it to the choroid plexus, which has distinct anatomical boundaries and less overlap with adjacent tissues. This makes the measurement more robust to voxel location variations and improves signal consistency.
Solution Approach 2:
The patent exploits the unique local quality of the choroid plexus - its distinct anatomical structure and location within the ventricular system - to obtain a cleaner AIF signal. The CP's specific characteristics provide a measurement environment that is less sensitive to voxel placement variations compared to the MCA.
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
Provides a consistent and accurate method for calculating absolute perfusion metrics like mean transit time and cerebral blood flow, enabling identification of abnormalities and reducing errors in hemodynamic measurements.
Implementation Method 1
dynamic susceptibility contrast (DSC)
Implementation Method 2
the contrast agent is deoxyhemoglobin
Data Source
AI summary
Conventionally, the arterial input function is determined by administering a contrast agent and measuring the responsive magnetic signal in a reference voxel located in a large artery such as the middle cerebral artery. By instead measuring the signal in a voxel of the choroid plexus, a more accurate profile for the arterial input function may be obtained. The metabolic activity in the choroid plexus is negligible, which provides greater certainty for signal sampling.