Abstract: BACKGROUND: Crosslinked sodium hyaluronate gel has good mechanical property, biocompatibility, and biodegradability, and can be used as an isolated protective material in tumor radiation therapy to protect endangered organs from damage caused by excess radiation dose.
OBJECTIVE : To investigate the safety and efficacy of crosslinked sodium hyaluronate gel in reducing the dose of radiation to dangerous organs during brachytherapy.
METHODS: A total of 16 specific pathogen-free Kunming mice of the same age and similar body weight were selected as experimental subjects and divided into experimental group and control group by the random number table method, with 8 mice in each group. 125I seeds were implanted subcutaneously in the back of mice in the experimental group, and then crosslinked sodium hyaluronate gel was injected around the radioactive particles. Only 125I seeds were implanted subcutaneously in the back of mice in the control group. After injection, the distance between the radioactive particles and the epidermis was measured by spiral CT scan, and the surface radiation dose was measured by radiation dosimeter. Within 10 weeks after injection, the growth state, survival rate, skin radiation damage, and gel retention of mice were observed.
RESULTS AND CONCLUSION: (1) Spiral CT scan showed that the implanted gel was relatively concentrated and created an effective distance between the radioactive seeds and the epidermis. The body surface radiation dose of the experimental group was significantly lower than that of the control group (P < 0.01). (2) During the experimental observation period, mice in both groups survived; mice in the control group showed obvious irritability and other unstable behavior in the late experimental period, and some mice in the experimental group showed similar behavior. The daily food intake of mice in the two groups had no significant change, and the body mass showed the same increasing trend. After implantation of radioactive seeds, the two groups of mice showed different degrees of radioactive skin injury. From day 23 after injection to the end of the experiment, the skin radiation injury score of the experimental group was lower than that of the control group (P < 0.01). At week 10 after implantation, 6 mice in the experimental group had no obvious gel residue under their skin, and 2 mice had a very small amount of scattered gel-like samples under their skin. (3) Therefore, the crosslinked sodium hyaluronate injection technique can increase the space between the radioactive target area of 125I seeds and the organ at risk outside the target through physical space occupying, which can effectively reduce the dose of the organ at risk, and play a role in the isolation and protection of the organ at risk.

Key words: crosslinked sodium hyaluronate gel, 125I seeds, organ at risk, isolation and protection, animal experiment, brachytherapy