Myofascial pain syndrome (MPS) is a common skeletal muscle pain and dysfunction,characterized by the presence of myofascial pain points (MTrPs).At present,the main method of locating MTrPs is palpation which has lower intra-rater reliability,and lacks an objective evaluation approach for therapeutic effects.Therefore,the research on objective evaluation of the characteristics of MPS has been receiving great attention.These studies involve stiffness of trigger points,fascia thickness,surface temperature and other aspects through various methods,such as ultrasonic imaging,magnetic resonance imaging,infrared thermal imaging.In this paper,the research progress and methods of MPS in imaging were surveyed,which can provide the basis for the clinical diagnosis and objective evaluation of therapeutic effects.

Objective To explore a new method for synthesizing arginine modified chitosan ( AC ) with mono-arginine substitution and high degree of substitution, and to evaluate the biological effect of AC as gene carriers. Methods The single arginine modified chitosan (sAC) was synthesized by means of protecting and de-protecting the arginine amino group before and after chitosan modified arginine reaction. Liu's arginine-modified chitosan ( LAC ) was prepared according to the methods reported in the literature . The conjunction of arginine to chitosan was detected by infrared spectroscopy and nuclear magnetic resonance spectroscopy. Three kinds of chitosan gene nanoparticles were respectively prepared by complex coacervation and characterized, including sAC gene nanoparticles (sACGNs), the LAC gene nanoparticles (LACGNs) and the chitosan gene nanoparticles (CGNs). A10 rat vascular smooth cells transfected with sACGNs were used to estimate the in vitro cellular uptake, internalization mechanisms and transfection efficiency. Thiazolyl blue tetrazolium blue (MTT) assay was used to measure the cytotoxicity. Results The infrared spectrum analysis confirmed that sAC was obtained via the conjunction of arginine to chitosan. Nuclear magnetic resonance spectrum analysis showed that the degree of substitution of arginine in sAC and LAC was 21.3％and 6.4％, respectively. When the ratio of nitrogen to phosphorus (N/P ratio) was 2:1, the particle sizes of CGN, LACGN, and sACGN were (94.81±2.93) nm, (124.53±2.55) nm, and (128.53±2.04) nm, respectively, and the Zeta potentials were (3.50±1.61) mV, (5.74±0.41) mV, and (6.04±1.39) mV, respectively. For the cellular uptake, CGNs were mainly through the clathrin-mediated endocytic pathway, and LACGNs and sACGN were mainly through the caveolin-mediated endocytic pathway. Compared with CGNs, LACGNs and sACGNs showed higher cellular uptake and transfection efficiency , and the differences were statistically significant ( all P<0 . 05 ) . sACGNs achieved the highest transfection efficiency in the near-neutral pH environment. MTT results showed that when the mass concentration of sACGNs reached 100μg/ml, the survival rate of A10 cells was still higher than 90％, indicating the non-cytotoxicity of sACGNs. Conclusion The new method successfully synthesized single arginine-modified chitosan. As a gene carrier, sACGNs show higher gene transfection efficiency and lower cytotoxicity than CGNs and LACGNs in near neutral pH environment.