RF Saturation Pulse for Non-Contrast MR Angiography
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Solution Overview
Problem
Catheter-based interventions face challenges in visualizing vessel paths during procedures due to the risks associated with contrast agents, particularly in low-field magnetic resonance facilities where higher doses are required, which can be adverse for patients with pre-existing conditions.
Innovation Solution
A method using RF saturation pulses to saturate blood flows within specific volume segments, allowing for the creation of Time-Of-Flight non-contrast-enhanced MR angiography images that visualize vessel paths without contrast agents, enabling precise guidance of intervention tools within vessels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If contrast agents are used to visualize blood vessels during catheter-based interventions, then vessel paths become visible, but patient health is at risk due to adverse effects from contrast agent administration
Solution Approach 1:
The patent extracts and removes the harmful contrast agent from the imaging process by implementing a non-contrast-enhanced MRA method that uses RF saturation pulses and time-of-flight effects to visualize vessels without any contrast medium, thereby eliminating the health risks associated with contrast agent administration
Solution Approach 2:
The patent changes the imaging parameters by using specific RF saturation pulse sequences and timing parameters to create flow-related contrast that highlights vessel paths without requiring contrast agents, transforming the imaging approach from contrast-dependent to flow-dependent visualization
2Object-affected harmful factors
If higher field strength magnetic resonance facilities are used to reduce contrast agent dose, then patient safety improves, but device complexity and cost increase
Solution Approach 1:
The patent removes the dependency on high field strength by extracting the contrast enhancement function from contrast agents and implementing it through RF saturation pulse sequences that work effectively at lower field strengths, making the system accessible to more facilities
Solution Approach 2:
The patent substitutes the physical/chemical mechanism of contrast agent enhancement with an electromagnetic mechanism using RF saturation pulses and time-of-flight effects, replacing the need for high field strength hardware with a pulse sequence-based solution
3Object-affected harmful factors
If contrast agents are minimized or eliminated, then patient safety improves, but vessel path visualization becomes difficult
Solution Approach 1:
The patent converts the natural flow of blood (which would normally be difficult to visualize without contrast) into a beneficial signal by using time-of-flight effects where moving blood protons experience different RF saturation than stationary tissue, creating inherent flow contrast that highlights vessel paths
Solution Approach 2:
The patent applies preliminary RF saturation pulses to specific volume segments upstream of the region of interest before acquiring the imaging data, so that when contrast-free blood flow enters the imaging region, it has not been saturated and appears bright against the saturated background, achieving vessel visualization without contrast agents
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 the determination of intervention tool position and visualization of vessel paths in real-time, reducing the need for contrast agents and minimizing adverse effects on patients, while maintaining effective imaging quality.
Implementation Method 1
At least one RF saturation pulse is radiated into the first volume segment, in order thereby to saturate the fluid within the first volume segment, which flows to the position of the front end of the intervention tool in the flow direction in the vessel
Implementation Method 2
A position of a front end of the intervention tool is determined in a computer in the insertion direction within the vessel
Implementation Method 3
MR data are acquired within a second volume segment, which comprises the front end of the intervention tool and a region in front of the intervention tool in the insertion direction. This step is performed at a time so that at least some of the fluid that was saturated in the previous step has flowed into the second volume
Data Source
AI summary
In a method and magnetic resonance (MR) apparatus for monitoring an interventional procedure with an intervention tool in a vessel of an examination subject, the intervention tool is moved in an insertion direction in the vessel and the position of a front end of the intervention tool in the insertion direction is determined. A first volume segment is determined dependent on the position and the flow direction of a fluid within the vessel. An RF saturation pulse is radiated into the first volume segment that saturates nuclear spins in the fluid within the first volume segment. MR data are acquired in a second volume segment, which contains the front end of the intervention tool and a region in front of the intervention tool in the insertion direction. An MR image is generated from the acquired MR data.