Introduction: Islet macroencapsulation is a promising treatment for type 1 diabetes (T1D) as it opens the possibility to transplant stem-cell derived islets without immunosuppression. Since, at the islet densities necessary to achieve therapeutic effect, adequate oxygenation becomes the limiting factor, it is critical to monitor oxygen levels. Herein, we describe the development of a desktop magnetic resonance imaging (MRI) oxygen scanner for making non-invasive oxygen measurements within islet macroencapsulation devices in humans.

Methods: A 0.5 Tesla (T) magnet with an 18 cm bore/36 cm length was interfaced to a CIERMag digital magnetic resonance spectrometer (DMRS). Pulse sequences were programmed on the DMRS system to allow measurement of T₁ relaxation time. A solenoid transceiver coil was constructed and utilized for measurements.

Results: A prototype oxygen scanner was constructed and system characterization / data acquisition is underway. Proton spectra and T₁ measurements have been made. Preliminary results suggest feasibility of using this scanner to make noninvasive oxygen measurements within islet macroencapsulation devices.


Discussion/Conclusion: Previously, it has been shown that 19F MRI can be used to noninvasively measure oxygen within islet macroencapsulation devices, in vivo. While, for those initial studies, the use of whole-body clinical MRI scanners sufficed, as islet macroencapsulation devices approach the clinic and are ultimately successful and routinely used to treat T1D, widely available, inexpensive and quick non-invasive oxygen measurements within them may be helpful in guiding treatment and/or evaluating implant status. The current MRI infrastructure within hospitals is ill-equipped, very costly and impractical for such measurements. To address this shortcoming, we have built a novel compact, portable MRI oxygen scanner (Fig. 1) and developed software and pulse sequences on the CIERMag DMRS to make oxygen measurements.