Physiorack: an integrated MRI safe/conditional, gas delivery, respiratory gating, and subject monitoring solution for structural and functional assessments of pulmonary function.

PURPOSE

To evaluate the use of a modular MRI conditional respiratory monitoring and gating solution, designed to facilitate proper monitoring of subjects' vital signals and their respiratory efforts, during free-breathing and breathheld 19F, oxygen-enhanced, and Fourier-decomposition MRI-based acquisitions.

MATERIALS AND METHODS

All Imaging was performed on a Siemens TIM Trio 3 Tesla MRI scanner, following Institutional Review Board approval. Gas delivery is accomplished through the use of an MR compatible pneumotachometer, in conjunction with two three-way pneumatically controlled Hans Rudolph Valves. The pneumatic valves are connected to Douglas bags used as the gas source. A mouthpiece (+nose clip) or an oro-nasal Hans Rudolph disposable mask is connected following the pneumatic valve to minimize dead-space and provide an airtight seal. Continuous monitoring/sampling of inspiratory and expiratory oxygen and carbon dioxide levels at the mouthpiece/mask is achieved through the use of an Oxigraf gas analyzer.

RESULTS

Forty-four imaging sessions were successfully monitored, during Fourier-decomposition (n=3), fluorine-enhanced (n=29), oxygen-enhanced, and ultra short echo (n=12) acquisitions. The collected waveforms, facilitated proper monitoring and coaching of the subjects.

CONCLUSION

We demonstrate an inexpensive, off-the-shelf solution for monitoring these signals, facilitating assessments of lung function. Monitoring of respiratory efforts and exhaled gas concentrations assists in understanding the heterogeneity of lung function visualized by gas imaging.