De Qi, a Threshold of the Stimulus Intensity, Elicits the Specific Response of Acupoints and Intrinsic Change of Human Brain to Acupuncture
Blood flow changes at acupoints following acupuncture before and after de qi. A PeriScan PIM II laser Doppler perfusion imaging (LDPI) was used in this study for analysis and processing of the acupoint blood perfusion image. Before the acupuncture needle stimulation, the basal blood flow of the healthy subjects was low and then significantly increased when deep-punctured but without De qi (). When the healthy subject felt de qi sensation, the skin blood flows at the acupoints were more evident than those before de qi () and these changes were time-dependent (Figures 4(a1) and 4(a2) for Hegu and Figures 4(b1) and 4(b2) for Zusanli).