A Low-Cost, Microcontroller-Based Gas Delivery System for Respiratory Stimuli in MRI Studies

Area of Science:

• Medical Imaging
• Physiological Monitoring
• Biomedical Engineering

Background:

• Automated control of respiratory stimuli is crucial for consistent physiological measurements during MRI.
• Existing systems can be expensive or lack precise synchronization capabilities.
• Developing a cost-effective and reliable solution is essential for broader research applications.

Purpose of the Study:

• To design and validate an inexpensive, microcontroller-based system for automated delivery of fixed inspired respiratory stimuli during MRI experiments.
• To synchronize gas delivery with MRI image acquisition using external timing signals.
• To provide a reliable and repeatable method for physiological stimulation in MRI.

Main Methods:

• A system using solenoid valves controlled by an Arduino circuit was developed to switch between medical gases.
• Gas delivery was synchronized with MRI acquisition using the scanner's external timing signal.
• The system was evaluated using hypercapnic and hyperoxic stimuli, measuring end-tidal gases and BOLD MRI responses at 3T.

Main Results:

• The system demonstrated reliable and repeatable gas transitions during MRI-triggered protocols.
• Hypercapnia (5% CO2) induced an 8.7 mmHg increase in end-tidal CO2, correlating with a 3.2% gray matter BOLD signal increase.
• Hyperoxia (60.5% O2) resulted in a 292.3 mmHg increase in end-tidal O2, with a 1.2% BOLD signal change.

Conclusions:

• The microcontroller-based system offers an affordable and dependable method for automated respiratory stimuli administration during MRI.
• This system bridges the gap between manual methods and expensive commercial gas blenders.
• It is highly suitable for technical studies in cerebrovascular reactivity and hyperoxia-BOLD applications.