Device for the controlled cooling and freezing of excised plant specimens during magnetic resonance imaging

Camilo Villouta, Benjamin L. Cox, Beth Rauch, Beth Ann A. Workmaster, Kevin W. Eliceiri, Amaya Atucha

Cooling circuit and device design: Schematic showing the cooling circuit detailing locations of the refrigerant pool and pump in the control room (A) and the cooling device within the MRI (B). CAD diagram of assembled cooling device (B) highlighting the sample chamber (pink). The remaining interior volume is comprised of the surrounding coolant chamber through which chilled ethylene glycol is pumped. Scale bar is approximately 2 cm.

Woody plants’ adaptations to withstand freezing temperatures are key for their survival in environments with extreme winter temperatures, as well as, in the case of agricultural crops, for the attainment of consistent yields under the threat of climate change. Currently, magnetic resonance imaging (MRI) is the only tool that allows the non-destructive study of the propagation and distribution of ice formation in complex plant organs at different experimental temperatures. However, despite its benefits and past successes, the use of MRI in plant sciences remains low, likely due to limited access, high costs, and associated engineering challenges. Engineering challenges are of particular concern when attempting the study of plant buds with MRI at freezing temperatures, given the need to keep plant samples at consistent freezing temperatures within the MRI equipment for many hours. Addressing these challenges, here we describe the design, fabrication, and testing of a low-cost MRI-compatible sample holder and cooling device that enables the controlled freezing of plant specimens while samples are scanned in an MRI device.

Shown in the figure below are all of the components of both the novel device, but also the cooling circuit used for cooling plants during MRI experiments. The device consists of many commercially-available parts and hardware, as well as three custom, 3D printed parts. The design files needed to print these custom pieces are included in the attached zip file. Please see the linked manuscript for more details on the development and use of this device.


Components of the cooling device and experimental cooling circuit: The fabricated cooling device (A-C), including the individual device parts (A), view of cap end of the assembled device (B), and view of coolant inlet/outlet end of the assembled device (C). Neoprene-insulated Tygon® tubing, conducting the chilled ethylene glycol (D), is further wrapped in an additional layer of polyethylene pipe insulation (E). A peristaltic pump (F) delivers the chilled ethylene glycol to the cooling device while situated in the MRI unit (G, H) from the circulating bath (refrigerant pool) (I) via the insulated tubing. Chilled coolant flows through the sample chamber, containing the sample holder comprised of several individual sample tubes. Sample holders were made to hold tubes of three different sizes (J), to accommodate a range of excised plant specimens.