MRI Head Coil Layout for Non-Contact Photoplethysmography
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Solution Overview
Problem
The integration of photoplethysmography (PPG) in magnetic resonance imaging systems is hindered by space restrictions and strong magnetic and radio frequency fields within the MRI system.
Innovation Solution
A head coil device with integrated light sources and optical sensors is used to perform remote photoplethysmography (rPPG), illuminating and detecting light scattered at the subject's skin without direct contact, utilizing the MRI system's bore for signal acquisition, and avoiding the need for additional mirrors or sensors within the bore.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical sensors and light sources are integrated within the MRI bore for PPG measurement, then measurement capability is improved, but space restrictions and interference from magnetic and radio frequency fields worsen the feasibility
Solution Approach 1:
The optical sensor and light source are extracted from the MRI bore environment and positioned externally. The system uses the bore's inner surface as a reflective intermediary to redirect light between the external sensor and the subject's skin, thereby removing the sensor from the harmful magnetic and radio frequency field environment while still enabling PPG measurement
Solution Approach 2:
The bore's inner surface serves as an optical intermediary (mirror) that redirects light from the external light source to the subject's skin and back to the external sensor. This intermediary allows optical signal transmission without requiring the sensor to be physically present in the MRI bore, solving the field interference problem
2Measurement precision
If additional mirrors or sensors are installed within the bore to enable rPPG, then measurement capability is improved, but device complexity increases
Solution Approach 1:
The MRI bore's existing inner surface is utilized as the optical mirror, eliminating the need for additional mirror components. The system leverages the bore's inherent structure to perform the optical reflection function, thereby reducing device complexity while achieving rPPG capability
Solution Approach 2:
The bore's inner surface serves dual functions: its primary function for MRI operation and its secondary function as an optical mirror for rPPG. This multi-functionality eliminates the need for dedicated mirror components, reducing overall system complexity
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
Enables non-contact monitoring of physiological processes like heart rate and respiration during MRI, improving signal-to-noise ratio and reducing claustrophobia, while avoiding interference from MRI fields and space constraints.
Implementation Method 1
providing light emitted by the at least one light source and scattered at the target area for a remote photoplethysmography signal acquisition
Implementation Method 2
Photoplethysmography (PPG) is a technique that uses changes in light interaction, e.g., light absorption, to measure blood volume changes in the microvasculature
Implementation Method 3
The received light comprises emitted light, which is scattered additionally at the inner surface of the bore
Data Source
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AI summary
Disclosed herein is a head coil device (100) comprising one or more magnetic resonance imaging coil elements and at least one light source (102) for a remote photoplethysmography. The at least one light source (102) is configured to illuminate at least one target area (106). The illuminating is configured for providing light (104) emitted by the at least one light source (102) and scattered at the target area (106) for a remote photoplethysmography signal (320) acquisition from the at least one target area (106).