A magnetic resonance-compatible programmable synchronized optical stimulation system

Abstract

A magnetic resonance-compatible programmable synchronized photostimulation system includes a main control unit and a stimulation execution unit. The main control unit is located outside the magnetic resonance scanning room, while the stimulation execution unit is located inside the scanning room and consists only of an LED light panel shielded by a magnetic field. The main control unit is configured to: receive photostimulation sequence parameters configured by the user in a modular manner through a graphical interface; receive a scan trigger signal from the magnetic resonance equipment, and automatically control the start and stop of the photostimulation sequence based on the trigger signal using hardware triggering; thereby achieving high-precision time synchronization between photostimulation and magnetic resonance scanning while maintaining magnetic resonance compatibility. This invention solves electromagnetic compatibility issues through a split architecture, achieves millisecond-level synchronization accuracy through hardware TTL triggering, and enhances experimental paradigm flexibility through modular programmable sequences, making it suitable for neuroscience research fields such as functional magnetic resonance imaging.

Description

Technical Field

[0001] This invention relates to neuroscience and medical imaging technology, specifically to an experimental stimulation technique used in brain science research such as functional magnetic resonance imaging (MRI). Background Technology

[0002] In cognitive neuroscience and psychology research, functional magnetic resonance imaging (fMRI) is a crucial non-invasive method for studying brain function. To explore the brain mechanisms of visual processing, attention, perception, and other functions, researchers often need to present subjects with precisely controlled light stimuli (such as flashing, patterns, color changes, etc.) during MRI scans and simultaneously record their brain activity signals.

[0003] However, directly deploying and using electronic stimulation devices within an MRI scanning chamber presents significant challenges. First, the presence of the main magnetic field necessitates that all equipment entering the scanning chamber be made of completely non-magnetic materials to prevent them from becoming dangerous projectiles or interfering with magnetic field homogeneity. Second, the electromagnetic noise generated during equipment operation, as well as the powerful gradient magnetic field switching and radio frequency pulses during scanning, can interfere with electronic equipment, leading to equipment malfunctions, uncontrolled stimulation, or the introduction of artifacts that affect image quality. Therefore, conventional LED stimulation devices cannot be used directly in an MRI environment.

[0004] Currently, several solutions have been proposed to address these issues. One common approach is a comprehensive MRI-compatible modification of the entire stimulation device, including the use of non-magnetic materials and rigorous electromagnetic shielding and filtering. This approach is costly, and the equipment is bulky and lacks flexibility. Another approach uses fiber optic transmission, placing the light source outside the scanning room and guiding the light into the room via fiber optics. While this method solves the magnetic field compatibility problem, it suffers from issues such as light intensity attenuation, difficulty in achieving multi-channel or complex pattern stimulation, fiber optic breakage, and complex system deployment. More importantly, existing solutions often fall short in terms of the flexibility of stimulation sequence programming, millisecond-level precise synchronization with MRI scan sequences, and convenient control of the experimental process. Many systems have fixed stimulation modes, making parameter adjustment difficult, or rely on manual operation for synchronization, introducing uncontrollable time delays and human error, which severely affects the reliability and reproducibility of experimental data.

[0005] In summary, there is an urgent need for a photostimulation solution that is fully compatible with the harsh magnetic resonance environment and provides a highly flexible, programmable, and precisely time-synchronized solution to meet the increasing demands of modern brain science research for the complexity of experimental paradigms and the precision of data.

[0006] Furthermore, existing methods have significant shortcomings in terms of the time synchronization accuracy between stimulation sequences and magnetic resonance scans, as well as the flexibility of sequence programming. Most systems rely on manual stimulation by the operator or software-timed triggering, which introduces uncontrollable human delays and communication errors, making it difficult to achieve millisecond-level precise locking. Simultaneously, stimulation modes are mostly fixed presets, making parameter adjustment difficult and hindering the rapid construction of complex experimental paradigms involving multiple channels, variable frequencies, and variable duty cycles. These deficiencies severely restrict the data reliability and paradigm design freedom of functional magnetic resonance imaging experiments. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to address the shortcomings of existing photostimulation systems, such as insufficient time synchronization accuracy with magnetic resonance scanning sequences due to reliance on software timing or manual triggering, and the difficulty in constructing complex experimental paradigms due to fixed stimulation modes. The present invention provides a photostimulation system that can operate stably in strong magnetic field and radio frequency interference environments and achieve high-precision time synchronization with magnetic resonance scanning equipment.

[0008] The technical solution adopted by the present invention to solve the above-mentioned technical problems is a magnetic resonance-compatible programmable synchronous optical stimulation system, comprising:

[0009] The main control unit is located outside the magnetic resonance scanning room;

[0010] The stimulation execution unit is located in the magnetic resonance scanning chamber and includes an LED light panel that has been shielded by a magnetic field.

[0011] The main control unit is configured as follows:

[0012] The system receives light stimulation sequence parameters configured by the user in a modular manner through a graphical interface.

[0013] It receives a scan trigger signal from the magnetic resonance imaging device and automatically controls the start and stop of the photostimulation sequence based on the trigger signal in a hardware triggering manner;

[0014] This allows for high-precision time synchronization between optical stimulation and magnetic resonance scanning while maintaining compatibility with magnetic resonance imaging.

[0015] Specifically, the main control unit includes:

[0016] A signal generator is used to generate multi-channel pulse width modulation (PWM) signals based on optical stimulation sequence parameters.

[0017] The controller is connected to both the signal generator and the stimulation execution unit, and is used to receive the PWM signal and drive the LED light panel to perform light stimulation.

[0018] This invention employs a separate internal and external structure with key shielding. The device mainly includes a main control unit located outside the magnetic resonance scanning room, and a stimulation execution unit located solely inside the scanning room.

[0019] The main control unit includes a laptop running dedicated control software, a multi-channel PWM signal generator, a controller, and their respective independent power supplies. The control software provides a graphical user interface, allowing users to flexibly edit complex optical stimulation sequences in a modular manner. Defineable parameters include at least: the flicker frequency of each independent channel, the pulse duty cycle, the duration of a single stimulus, and the rest time between stimuli, allowing users to freely combine these time periods to construct complete experimental paradigm sequences of arbitrary length and structure. The core functionality of the software is to receive scan start / end trigger signals from the MRI machine, enabling automatic, precise start, stop, and synchronization of the stimulation sequence, while also providing an independent manual control mode for equipment testing and sequence preview.

[0020] The stimulation execution unit is an LED light panel that has undergone special magnetic field shielding. This light panel is the only hardware located in the scanning chamber, positioned behind the MRI machine. It precisely guides the light path to the subject's field of vision via a built-in or attached reflector in the MRI head coil. The LED light panel is connected to the outdoor main control unit via a shielded through-wall cable, receiving only drive signals and power from the controller.

[0021] The signal flow between components is as follows: the control software sends the edited sequence parameters to the signal generator through the serial communication interface; the signal generator generates a corresponding multi-channel PWM digital signal accordingly; the PWM signal is transmitted to the controller, the controller analyzes the signal and converts it into a corresponding current to drive the LED board, precisely controlling its on / off timing, frequency and brightness.

[0022] To achieve magnetic resonance compatibility, the LED light board and its connecting cables have undergone strict non-magnetic and electromagnetic shielding treatments, such as using all non-magnetic electronic components and sealing and shielding the circuit board to eliminate interference with the main magnetic field and resist the influence of gradient field and radio frequency field on its operation.

[0023] The beneficial effects of this invention are:

[0024] Excellent magnetic resonance compatibility and operational stability: By placing most of the electronic equipment outside the scanning room and only providing targeted enhanced shielding for the LED light panel that must be placed indoors, interference from strong magnetic fields and radio frequency pulses to the core control circuit is fundamentally avoided, ensuring the absolute stability and reliability of the equipment during the scanning process, while eliminating the risk of introducing image artifacts.

[0025] Sub-millisecond high-precision time synchronization: By directly triggering software control sequences with hardware signals, extremely high-precision time locking between optical stimulation and magnetic resonance scanning sequences is achieved. This direct electrical signal triggering mechanism overcomes the errors caused by manual or software communication delays, providing a reliable data foundation for research such as functional magnetic resonance imaging that has extremely high requirements for time accuracy.

[0026] Highly flexible programmability and ease of operation: The modular sequence design software based on a graphical interface allows researchers to quickly design, modify, and test complex and ever-changing photostimulation paradigms without requiring programming knowledge, greatly improving the efficiency of experimental preparation and the flexibility of scientific exploration. The combination of manual and automatic modes facilitates equipment debugging and experimental process control.

[0027] Easy deployment and safe use: The modular design allows for quick and easy deployment of the equipment, eliminating the need for complex modifications to the scanning room. The indoor section consists of only a lightweight shielding light panel, significantly reducing safety risks and minimizing the space occupied in the limited scanning room.

[0028] This invention is particularly applicable to visual cognitive neuroscience, psychology and clinical brain function research conducted in a magnetic resonance environment, and can effectively improve the technical level and data quality of related experiments. Attached Figure Description

[0029] Figure 1 This is a schematic diagram showing the position of the LED light panel and the magnetic resonance sensor after shielding.

[0030] Figure 2 This is a schematic diagram of the path of LED light entering the retina;

[0031] Figure 3 This is a schematic diagram of the circuit of a two-channel photostimulation device. Detailed Implementation

[0032] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be described in detail below with reference to specific embodiments.

[0033] (1) System overall architecture and layout

[0034] The MRI-compatible LED synchronous stimulation device adopts a clearly defined split layout to address compatibility issues in the MRI environment.

[0035] Outside the scanning room (control area): Located outside the MRI scanning room, this area houses all components of the main control unit, including the laptop, signal generator, controllers, and their respective DC power adapters. All equipment is placed on dedicated carts or workbenches for easy operation by researchers.

[0036] The scanning chamber (scanning area): Located within the magnetic resonance scanning chamber, it contains only a magnetic field shielding LED light panel, such as... Figure 1 As shown. The light panel is fixed to the back of the examination table of the MRI machine or the equipment housing by a universal bracket or special clamp, ensuring that its light output hole is aligned with the center of the reflector integrated inside the MRI head coil.

[0037] Physical Connection: The scanning room and the outside are connected via a dedicated waveguide duct within the magnetic resonance shielded room. A composite shielded through-wall cable integrating power and signal lines passes through this duct, connecting one end to the controller output of the main control unit and the other end to the LED light panel inside the scanning room. This cable itself has an RF shielding layer to prevent it from becoming an interfering antenna.

[0038] (2) Stimulus execution unit (indoor part):

[0039] In this embodiment, the LED light panel is specifically designed for a 3T magnetic resonance environment. Its core is a printed circuit board on which multiple high-brightness LEDs of specific wavelengths are soldered. The key to achieving magnetic resonance compatibility lies in:

[0040] Non-magnetic materials: All electronic components (resistors, capacitors, driver ICs), connectors and housings are made of non-ferromagnetic materials (such as oxygen-free copper, aluminum, ceramics, and certain plastics).

[0041] Electromagnetic shielding and filtering: The LED board's circuitry is encapsulated within a continuous, grounded copper foil or aluminum shell, with only light-transmitting windows. All power and signal lines entering the shell pass through feedthrough filters mounted on the shell walls to filter out high-frequency radio frequency noise. The LED drive current loop area is minimized as much as possible to reduce gradient field induced current.

[0042] Light transmission: The light emitted from the LED panel is collimated by a short-focal-length lens group and then directed towards a high-quality reflector fixed inside the magnetic resonance head coil. This reflector deflects the light path by 90 degrees, ensuring that the light stimulus is horizontally transmitted to the eye of the subject lying supine inside the coil. Figure 2 As shown. This design avoids the need to install complex optical fibers or light guides within the scanning chamber. The reflector is either an integral or additional optical component of the MRI head coil.

[0043] (3) Main control unit, including control software, signal generator and controller:

[0044] Control Software: This device's dedicated control software runs on a laptop computer and features a graphical interface. The main interface provides a sequence editing area, allowing users to construct sequences on the timeline by dragging and dropping graphical modules such as blinking and still blocks. Each module can have its parameters set independently, such as the corresponding LED channel, frequency (0-100 Hz), duty cycle (1%-99%), and brightness level. The software includes a trigger setting menu for selecting the trigger source (e.g., manual, external TTL) and setting the delay after triggering. A separate serial communication module handles data packet communication with the signal generator.

[0045] Signal Generator: In this embodiment, a microcontroller-based multi-channel pulse width modulation (PWM) signal generation module is used. It connects to a laptop computer via a USB interface. After receiving command packets from the software (containing parameters such as channel, frequency, duty cycle, and duration), its internal timer accurately generates the corresponding digital PWM waveform.

[0046] Controller: In this embodiment, the controller is a constant current LED driver board. It receives a PWM signal from the signal generator and uses it as a switching signal to control the on and off of its internal high-power MOSFETs, thereby providing a stable and rapidly switchable drive current to the LED board. The controller and the LED board are connected via a twisted-pair shielded cable to transmit the drive current.

[0047] This embodiment uses a two-channel example for illustration. Two independent PWM signals output from the signal generator are connected to two input terminals of the controller, which in turn sets two drive outputs, each connected to one of two groups of LEDs on the LED board. Each group of LEDs can correspond to a different stimulation region or wavelength in physical space. When editing the sequence, the control software can independently set parameters such as frequency, duty cycle, and duration for each channel, achieving independent or coordinated stimulation of multiple channels. The circuit diagram for the two-channel device is as follows: Figure 3 As shown.

[0048] (4) Signal flow and synchronization process

[0049] The complete experimental procedure is illustrated in the following example:

[0050] Experimental Preparation: Design a visual experiment paradigm in the control software. For example, the LED in channel 1 blinks at a frequency of 10Hz for 500 milliseconds, then all channels are turned off (quiet) for 1500 milliseconds. Repeat this blinking and quieting combination 10 times to form a sequence with a total duration of 20 seconds. The software compiles this sequence into a series of commands containing timestamps and parameters.

[0051] System Connection and Startup: Connect all devices. Start the software and connect the signal generator via the serial port. Switch the software to external trigger mode.

[0052] Synchronous Scan Trigger: Before the MRI scan sequence begins, the technician activates the trigger-wait state in the software. When the MRI scan sequence starts, its scan console outputs a TTL rising edge pulse. This pulse is sent directly to a specific digital input port of the laptop's data acquisition card (or a trigger box with a USB interface) via a signal line. The control software monitors this port in real time, and once a rising edge is detected, it immediately retrieves the first instruction from the pre-loaded command sequence and sends it to the signal generator via the serial port.

[0053] Stimulation Execution: Upon receiving the command, the signal generator immediately outputs a PWM signal with the corresponding frequency and duty cycle on the designated channel. This PWM signal is transmitted to the controller, which then drives the LED board, causing the corresponding LEDs to blink precisely. The software sends subsequent commands sequentially according to the time sequence, and the signal generator dynamically updates the PWM output, thereby achieving complex stimulation patterns.

[0054] Sequence Termination: When the preset sequence is completed, or the software receives a TTL pulse from the end of the magnetic resonance scan (or the operator manually clicks stop), the software will send a full-channel shutdown command, the signal generator will stop outputting PWM, and the LED panel will turn off.

[0055] The system described in this example creatively solves the challenge of high-precision, programmable light stimulation in a magnetic resonance environment through spatial separation (external main control), localized enhanced shielding (processing only the lamp panel), precise digital control (software programming, PWM signals), and hardware signal synchronization (TTL direct triggering). The entire system is quick to deploy and intuitive to operate, providing a reliable, flexible, and powerful tool for neuroscience research.

Claims

1. A magnetic resonance-compatible programmable synchronized optical stimulation system, characterized in that, include: The main control unit is located outside the magnetic resonance scanning room; The stimulation execution unit is located in the magnetic resonance scanning chamber and includes an LED light panel that has been shielded by a magnetic field. The main control unit is configured as follows: The system receives light stimulation sequence parameters configured by the user in a modular manner through a graphical interface. It receives a scan trigger signal from the magnetic resonance imaging device and automatically controls the start and stop of the photostimulation sequence based on the trigger signal in a hardware triggering manner; This allows for high-precision time synchronization between optical stimulation and magnetic resonance scanning while maintaining compatibility with magnetic resonance imaging.

2. The system as described in claim 1, characterized in that, The main control unit includes: A signal generator is used to generate a multi-channel pulse width modulation (PWM) signal based on the optical stimulation sequence parameters. The controller is connected to both the signal generator and the stimulation execution unit, and is used to receive the PWM signal and drive the LED light panel to perform light stimulation.

3. The system as described in claim 2, characterized in that, The signal generator is configured to output at least two independent channels of PWM signal, and the parameters of each channel can be set individually.

4. The system as described in claim 2, characterized in that, The controller is an LED driver controller with at least two channels, which provides driving current to the LED board by receiving external PWM signals.

5. The system as described in claim 2, characterized in that, The parameters of the light stimulation sequence configured in the modular manner include at least: the flashing frequency, duty cycle, duration of a single flash, rest time between adjacent flashes for each LED channel, and a complete stimulation sequence composed of multiple flashing periods and resting periods.

6. The system as described in claim 5, characterized in that, The main control unit is also equipped with a manual control mode, which allows users to manually start, stop, or test the light stimulation sequence through the graphical interface, independent of the scanning trigger signal of the magnetic resonance device.

7. The system as described in claim 1, characterized in that, The main control unit receives the scan trigger signal through the digital input port of the data acquisition card or USB trigger box. The scan trigger signal is a TTL pulse signal.

8. The system as described in claim 1, characterized in that, The main control unit and the stimulation execution unit are connected for signal and power via a shielded cable that passes through the wall. The LED light panel is the only hardware component located in the magnetic resonance scanning room.

9. The system as described in claim 1, characterized in that, The magnetic field shielding treatment includes encapsulating the circuit board and cables of the LED light panel with non-magnetic materials and / or wrapping them with an radio frequency shielding layer.

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