Rapid Prototyping of Inspired Gas Delivery System for Pulmonary MRI Research

Specific ventilation imaging (SVI) is a noninvasive magnetic resonance imaging (MRI)-based method for determining the regional distribution of inspired air in the lungs, useful for the assessment of pulmonary function in medical research. This technique works by monitoring the rate of magnetic resonance signal change in response to a series of imposed step changes in inspired oxygen concentration. The current SVI technique requires a complex system of tubes, valves, and electronics that are used to supply and rapidly switch inspired gases while subjects are imaged, which makes the technique difficult to translate into the clinical setting. This report discusses the design and implementation of custom three-dimensional (3D) printed hardware that greatly simplifies SVI measurement of lung function. Several hardware prototypes were modeled using computer-aided design software and printed for evaluation. After finalization of the design, the new delivery system was evaluated based on O₂ and N₂ concentration step responses and validated against the current SVI protocol. The design performed rapid switching of supplied gas within 250 ms and consistently supplied the desired concentration of O₂ during operation. It features a reduction in the number of commercial hardware components, from five to one, and a reduction in the number of gas lines between the operator's room and the scanner room, from four to one, as well as a substantially reduced preparation time from 25 to 5 min. 3D printing is well suited to the design of inexpensive custom MRI compatible hardware, making it particularly useful in imaging-based research.