A method and system for measuring time variations of a response of a blood perfused fleshy medium to an external electromagnetic field is provided. The response of the medium to the external electromagnetic field can be a photo-acoustic signal, obtained in response to the exciting light, and/or impedance of the medium, in response to the applied ac electromagnetic field. Measurements of the time variations of the response of the medium are carried out when the condition of artificial kinetics is created and maintained over a certain time period by applying primary over-systolic pressure to a certain location at the medium with normal blood flow, so as to achieve a state of temporary blood flow cessation at the medium downstream of the certain location. When required, the control of the condition of the artificial kinetics can be further achieved by applying a perturbation of secondary pressure to the fleshy medium.