Camera-Based Cardiac Signal Extraction for MRI Gating
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Solution Overview
Problem
Current methods for cardiac synchronization during medical imaging procedures, such as MRI and CT scans, rely on contact sensors like ECG electrodes, which are uncomfortable, time-consuming to set up, and can be distorted by high magnetic fields, leading to unreliable cardiac gating and contamination risks.
Innovation Solution
A camera-based system that uses remote observation to detect cardiac signals through photoplethysmography (PPG) without direct contact, employing image processing techniques to extract a signal indicative of the cardiac cycle from camera images, allowing for automated and efficient cardiac triggering in both prospective and retrospective modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contact sensors like ECG electrodes are used for cardiac synchronization, then reliable cardiac gating can be achieved, but the method becomes uncomfortable, time-consuming to set up, and prone to contamination
Solution Approach 1:
The patent replaces contact-based mechanical/electrical sensing (ECG electrodes) with optical sensing using a camera to detect cardiac signals through photoplethysmography. This substitution eliminates the need for physical contact while maintaining the ability to detect cardiac cycle information, thereby improving ease of operation and reducing contamination risks while preserving gating reliability
Solution Approach 2:
The patent introduces an intermediary optical detection system (camera-based PPG) that indirectly measures cardiac activity through blood volume changes in skin tissue rather than directly measuring electrical signals. This intermediary approach allows for contactless detection while maintaining sufficient accuracy for cardiac gating applications
2Measurement precision
If contact sensors are used for cardiac synchronization, then accurate R-peak detection can be achieved, but the risk of bacterial or viral contamination increases
Solution Approach 1:
The patent replaces direct electrical contact measurement with optical measurement through a camera system. This substitution eliminates skin contact entirely, removing the contamination pathway while maintaining the ability to detect cardiac cycle events with sufficient precision for gating purposes
3Manufacturing precision
If high field strength MRI is used for imaging, then high-quality images can be obtained, but the ECG signal becomes distorted and unreliable
Solution Approach 1:
The patent replaces electrical signal-based cardiac monitoring (ECG) with optical signal-based monitoring (camera-based PPG). Since optical detection does not involve electrical conductors or electrodes that are susceptible to magnetic field interference, the cardiac signal detection remains reliable in high-field MRI environments while maintaining image quality
4Productivity
If camera-based PPG is used for cardiac triggering, then workflow efficiency and comfort are improved, but the setup and processing requirements become more complex
Solution Approach 1:
The patent implements automated detection algorithms that can automatically identify the camera view of the subject and extract cardiac signals without requiring manual configuration or expert intervention. This self-service capability simplifies the workflow while maintaining the productivity benefits of contactless operation
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 a comfortable, efficient, and reliable method for cardiac synchronization, reducing contamination risks and maintaining accuracy even under suboptimal imaging conditions, with the ability to operate in high-field MRI environments and deliver near-real-time cardiac gating signals.
Implementation Method 1
A camera-based system that uses remote observation to detect cardiac signals through photoplethysmography (PPG)
Data Source
AI summary
A method (100) is disclosed for determining a signal indicative of a state of a subject during a diagnostic imaging or therapeutic procedure based on camera observation. The method comprises acquiring (101) camera images from a camera configured to monitor a body part of the subject during the procedure, e.g. via a reflection thereof in a reflective surface. The method comprises detecting (102) a shape or contour of the reflective surface in at least one acquired camera image to define a region of interest in the image that contains image information corresponding to the body part of interest, and segmenting (103) the region of interest in one or more camera images to select pixels that correspond to a feature of the body part of interest. The method also comprises determining (105) the signal indicative of the state of the subject from the selection. The invention further relates to a corresponding device, system and computer-program.