Objective To observe the duration of local reactions after subcutaneous micro-invasive catgut-embedding stimulation in Zusanli(ST 36)region in normal human body by using magnetic resonance(MR)T2 -mapping

so as to find a reasonable interval between every two catgut-embedding performance.Methods A total of 8normal volunteers(3women

and 5men)were enrolled in the present study.Before and 8h

and 3

7

14

21

28 and 35days after the subcutaneous micro-invasive embedment of catgut(Gauge 2.0

2cm long)in the left Zusanli(ST 36)area

the local T2 -weighted images(T2 WI)and fatsuppression T2 -weighted images(FS T2 WI)were detected and recorded by using MR scan(GE Optima MR 360 1.5T)and analyzed using FuncTool software.Results Compared with pre-catgut-embedment

the local signal strength of T2 FS WI and T2 relaxation time began to rise on the 8th hour after catgut-embedment

peaked on the 3rd day

began to descend on the 7th day

but being still higher than pre-embedment

and turned to the normal level on the 21 st day to the 35 th day.Results of statistical analysis displayed that compared with pre-catgut-embedment

T2 relaxation time levels were significantly higher on the 8th h

day 3

7and 14 after the embedment(P<0.01)

and were comparable to that of pre-embedment on day 21

28 and 35(P>0.05).Conclusion Catgut-embedment of Zusanli(ST 36)induces an apparent change of MRI signals from the 8th h to the 14 th day in normal volunteer subjects

suggesting that an interval of 21 days may be reasonable for the micro-invasion catgut-embedment in clinical practice.