Ultrasound (US) apparatus and method for applying low energy US onto an internal tissue/organ, including a non-invasive US appliance used on a treatment region over the internal tissue/organ, and an electrical stimulation apparatus for simultaneously inducing interferential electrical stimulation. A controller controls parameters of the electrical stimulation apparatus and the US appliance, and dynamically changes at least one of the parameters, for maintaining the impedance of the body tissue in the treatment region within an impedance range. The US apparatus includes an impedance monitoring apparatus for continuously measuring, tracking, and monitoring impedance in the treatment region, wherein the controller dynamically changes at least one of the parameter in response to the impedance as monitored, for maintaining the impedance within the predefined range. The internal tissue/organ can be a female fertility organ which can be an ovarian follicle, a blood vessel of the uterus (womb), the ovary, the endometrial lining, and the Fallopian tube; a lung, a pulmonary organ, an adipose tissue, ulcer, closed wound, internal injury, inflammation. and nerves.