Detection of muscle damage by B-mode ultrasonography : relationship between echo intensity and histological changes following injection of bupivacaine to rat hind limb muscles
Date of Award
Master of Science
School of Exercise, Biomedical and Health Sciences
Faculty of Computing, Health and Science
It is reported that the echo intensity of B-mode ultrasound images increases when human elbow flexors are damaged by eccentric exercise. However, it is unknown what causes the increase in echo intensity, and its relationship to histological changes is unexplored. This study tests the hypothesis that infiltration of inflammatory cells in damaged muscle fibres causes an increase in the echo intensity of B-mode ultrasound images. The study is carried out by injecting bupivacaine hydrochloride (BPVC), which is known to result in infiltration of mononuclear cells, into rat hind limb muscles. This study was approved by the Institutional Animal Research Ethics Committee. BPVC (0.5 % of 0.5 ml) or saline (0.9 % NaCl of 0.5 ml) was injected to the tibialis anterior muscle (TA) of 14-19 wk male Wistar rats (n=12). Ultrasound images were taken from the muscles before, 0, 2, 4, 6, 9, 12, 24, 48, 72, 120, 168, and 336 hours after the injections using a 7.5 MHz probe connected to an Image Point HX® (HP, USA). The images were analysed by an Image J (NIH, USA) to assess the changes in echo intensity of a region of interest, and changes in the intensity were compared between BPVC and controlled conditions. In the subsequent study, the rats (n= 16) were sacrificed before and 0, 2, 6, 12, 24, 48, and 168 hours after BPVC or saline injection into the TA after assessing changes in the echo intensity up to the time of sacrifice in the same time course of the first study. "Histological changes in the muscle after the injection were observed and compared with the ultrasound images. Changes in the echo intensity in the TA after BPVC injection were compared between the control (non and saline injection) and injected limbs by a two-way analysis of variance with repeated measures. The echo intensity did not change significantly in muscles that did not receive an injection. BPVC injection induced greater (P<0.05) increases in the echo intensity compared with saline injection, peaking 0 to 24 hours after the injection. The time course of changes in the echo intensity did not match with the time course of infiltration of inflammatory cells to the muscle, which showed small increases in the first 6 hours followed by profound increases between 24 and 168 hours after injection. It was concluded that infiltration of inflammatory cells to damaged muscle fibres is not a direct cause of the increase in echo intensity.
Fujikake, T. (2008). Detection of muscle damage by B-mode ultrasonography : relationship between echo intensity and histological changes following injection of bupivacaine to rat hind limb muscles. Retrieved from http://ro.ecu.edu.au/theses/166