Ultrasound (US) apparatus for applying low energy US onto an internal tissue/organ , comprising: (a) a non-invasive external US appliance operational for applying low energy US energy, at an US frequency and an US intensity, onto a treatment region over the internal tissue/organ ; and (b) an electrical stimulation apparatus comprising two pairs of electrodes operational for inducing interferential electrical stimulation configured for positioning at crossed configuration onto the skin at the treatment region in proximity to the internal tissue/organ , by applying, simultaneously with said applying US energy, a first current at a first electric frequency and a first electric intensity via one of said two pairs of electrodes , and a second current at a second electric frequency and a second electric intensity via another of said pairs of electrodes , thereby defining an interference pattern of resonant waves that revolve at an interferential frequency in said treatment region , characterized by further comprising (c) an impedance monitoring apparatus for continuously tracking and monitoring the impedance of the body tissue in said treatment region ; and (d) a controller for controlling parameters of said electrical stimulation apparatus and said US appliance , operational for dynamically changing at least one of said parameters in response to the impedance monitored by said monitoring apparatus , for maintaining said impedance within a predefined impedance range which is effective for delivery of US energy, wherein said parameters are selected from the group of electrical stimulation parameters and ultrasound parameters consisting of: (i) said interferential frequency; (ii) said interference pattern; (iii) said US frequency; and (iv) said US intensity. (a) a non-invasive external US appliance operational for applying low energy US energy, at an US frequency and an US intensity, onto a treatment region over the internal tissue/organ ; and (b) an electrical stimulation apparatus comprising two pairs of electrodes operational for inducing interferential electrical stimulation configured for positioning at crossed configuration onto the skin at the treatment region in proximity to the internal tissue/organ , by applying, simultaneously with said applying US energy, a first current at a first electric frequency and a first electric intensity via one of said two pairs of electrodes , and a second current at a second electric frequency and a second electric intensity via another of said pairs of electrodes , thereby defining an interference pattern of resonant waves that revolve at an interferential frequency in said treatment region , characterized by further comprising (c) an impedance monitoring apparatus for continuously tracking and monitoring the impedance of the body tissue in said treatment region ; and (d) a controller for controlling parameters of said electrical stimulation apparatus and said US appliance , operational for dynamically changing at least one of said parameters in response to the impedance monitored by said monitoring apparatus , for maintaining said impedance within a predefined impedance range which is effective for delivery of US energy, wherein said parameters are selected from the group of electrical stimulation parameters and ultrasound parameters consisting of: (i) said interferential frequency; (ii) said interference pattern; (iii) said US frequency; and (iv) said US intensity. <EOS>