Magnetic resonance navigator echo diaphragm monitoring in patients with suspected diaphragm paralysis

Real-time magnetic resonance (MR] navigator echo (NE) monitoring of the dia phragm is now possible. Using this technique, temporal changes in diaphragm position can be analyzed in a non-invasive fashion, without x-ray exposure . In this preliminary study. we have optimized three NE parameters (the NE column area, the NE repeat time, and the location of the NE on the diaphrag m surface), and demonstrated the clinical application of MR NE diaphragm mo nitoring in patients with suspected diaphragm paralysis. The NE parameters were defined in 10 healthy volunteers, and diaphragm traces were scored for variance in NE diaphragm position registration. Using the optimal NE colum n parameters, we investigated four patients with diaphragm paralysis, one o f whom required positive pressure ventilation while in the MR scanner, to s how the utility of this technique. The NE diaphragm position registration w as significantly affected by the area of the NE column, with poor position registration for the smallest column area (2.25 cm(2) vs. 4 cm(2) vs, 6.25 cm(2), variance 6.3 vs. 0.6 vs. 0.3, P = 0.006), Diaphragm position registr ation was also significantly affected by the NE repeat time, with misregist ration for the shortest repeat time (250 msec vs. 500 msec vs. 1000 msec, v ariance 11.9 vs. 0.6 vs. 1.0, P = 0.02), and data clipping, with loss of en d-expiratory and end-inspiratory position registration, for the longest rep eat time. Finally, if the NE was positioned too anteriorly, the diaphragm t races were of poor quality (anterior vs. dome vs. posterior, variance 11.8 vs. 0.6 vs, 3.2, P < 0.001), Application of the technique confirmed diaphra gm paralysis in all four patients. The technique can be applied during posi tive pressure ventilation if necessary. The optimal NE parameters for diaph ragm monitoring at 0.5 T were: column area, 400 mm(2); NE repeat time; 500 msec; NE column positioned on the diaphragm dome. MR NE diaphragm monitorin g provides a safe, non-invasive method of assessing diaphragm motion in pat ients with suspected diaphragm paralysis and may prove useful for long-term follow-up and monitoring of therapeutic interventions in these subjects. J , Magn, Reson, Imaging 1999;9:69-74. (C) 1999 Wiley-Liss, Inc.