Laser Doppler spectroscopy towards the detection of spontaneous muscle activity

Objective We used laser Doppler spectroscopy to detect hyperactivity of muscle fibers caused by the presence of fibrillations, positive waves and fasciculations. Methods The proposed method relies upon the dynamic scattering of light by moving particles, which causes a Doppler shift of the original frequency. For resolution of small alterations in frequency the heterodyne detection was used. One hundred seventy-three normal and 109 EMG diagnosed denervated first dorsal interosseous muscles were examined. Results Denervated muscles with fasciculations showed significant differentiation from control muscles, whereas denervated muscles without fasciculations were not significantly differentiated. The smallest differentiation compared to controls was seen in chronic denervated muscles without spontaneous activity. Conclusions Presence of fasciculations in denervated muscles allowed Doppler spectroscopy to differentiate them from normal muscles. Presence of atrophy reduced the diagnostic potential of the method. Significance Our findings can be used as a basis for further improving painless and noninvasive laser Doppler spectroscopy to be used clinically as an alternative to painful and invasive EMG.