ULTRASOUND SHEAR WAVE IMAGING: A QUANTITATIVE TECHNIQUE TO MONITOR THE PROGRESS OF AMYOTROPHIC LATERAL SCLEROSIS
Minhua Lu1,2, Zhenzhou Li3, Chaochao Zhu1, Shuai Huang1, Qingfeng Gao1, Xiang Wu1, Rui Mao1,4
1Shenzhen University, China;
2Guangdong Key Laboratory for Biomedical Measurements and Ultrasound Imaging, China;
3The Second People’s Hospital of Shenzhen, China;
4Guangdong Province Key Laboratory of Popular High Performance Computers, China
Amyotrophic lateral sclerosis (ALS) is a nervous system disease that causes muscle weakness and impacts physical function. Electromyography is regarded as the golden method for the early diagnosis of ALS. During the recent years, muscle ultrasound has been also involved in the early diagnosis and differentiation of ALS from other neuromuscular disorders. However, how to quantify the weakness of the muscles of ALS patients, is still remained as a challenge. Shear wave elastography is an ultrasound-based technique that characterizes tissue mechanical properties based on the propagation of remotely induced shear waves. Various ultrasound shear elasticity imaging techniques have been developed in the last two decades. In this study, we utilized focused comb-push induced shear wave method with an open research ultrasound system (Verasonics Inc., Redmond, WA), to quantitatively evaluate the biomechanical properties of the skeletal muscle noninvasively. A linear array transducer L7-4 (Philips Healthcare, Andover, MA) was used to produce the push beams (center frequency = 4.09 MHz, 600 us duration), and then immediately switched to plane wave imaging mode with all transducer elements (center frequency = 5.208 MHz), to track shear wave propagation inside the muscles, either along the muscle fiber or perpendicular to the muscle fiber. The shear wave speed was then estimated and used to calculate the shear modulus of the muscles. Elasticity of biceps brachii and soleus under different loading was evaluated in a healthy volunteer (aged at 24 years old) and three ALS patients (aged at 54 ± 17.8). It is found that the values of shear wave speed were significantly higher in both relaxed and contraction situation for the healthy volunteer than those of the ALS patients. The results were discussed and correlated with the progress of muscle weakness.