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Safe MRI‐Compatible electrical muscle stimulation (EMS) system
Author(s) -
Akbari Alireza,
Rockel Conrad P.,
Kumbhare Dinesh A.,
Noseworthy Michael D.
Publication year - 2016
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.25316
Subject(s) - phosphocreatine , biomedical engineering , skeletal muscle , magnetic resonance imaging , medicine , imaging phantom , stimulation , in vivo , electrical muscle stimulation , motor unit recruitment , nuclear medicine , nuclear magnetic resonance , materials science , anatomy , electromyography , physics , radiology , physical medicine and rehabilitation , biology , microbiology and biotechnology , energy metabolism
Purpose To develop an inexpensive magnetic resonance imaging (MRI)‐compatible electrical muscle stimulation (EMS) unit and test it for safety and efficacy. Materials and Methods A simple MRI‐compatible EMS device was developed using radiofrequency (RF) translucent electrodes at 3T. RF heating concerns were assessed using optical temperature measurements at electrode sites, during scanning of a phantom. EMS efficacy and consistency was investigated through in vivo ( n = 5) measures of 31 P‐MRS phosphocreatine (PCr) reduction, and altered blood oxygen level‐dependent (BOLD) signal and the results were compared to effects from equivalent voluntary effort on the same subjects. Results The presence of an EMS pulse did not interfere with the T 2 * signal in a phantom. However, signal‐to‐noise ratio (SNR) was reduced by 70% at electrode sites, but only by 10% 4 cm distally. Under RF intense conditions, the temperature at the electrode site increased by only 4.7°C over a 16‐minute time span. In vivo muscle stimulation resulted in 13.5 ± 1.8% reduction in PCr, which was not significantly ( P < 0.195) different from voluntary contraction. Reproducible muscle BOLD signal changes following EMS were noted, with a maximal increase of 10.0 ± 2.6% seen in the central soleus. For soleus and gastrocnemius compartments, EMS produced significantly higher BOLD signal change compared to voluntary contraction ( P < 0.05). Conclusion A safe and inexpensive MRI‐compatible EMS unit can be easily built for evaluating muscle function and metabolism within a 3T MRI scanner. Clinical applications might include evaluating skeletal muscle function in patients with limited or absent voluntary skeletal motor function or inadequate exercise capacity. J. Magn. Reson. Imaging 2016;44:1530–1538.