Non-invasive skin treatment device using r.f. electrical current with a treatment settings determiner

Abstract

The invention provides a non-invasive skin treatment device () comprising an r.f. treatment electrode (); a return electrode (); an r.f. generator () configured and arranged such that, during treatment, an r.f. treatment signal is applied between the r.f. treatment electrode () and the return electrode () for heating an inner region () of skin; an impedance measurement circuit () configured and arranged to measure, before treatment of the inner region, an initial skin impedance (Z) between the r.f. treatment electrode () and the return electrode (); and a treatment settings determiner () configured and arranged to determine, before treatment of the inner region (), treatment settings associated with the r.f. treatment signal depending on the initial skin impedance (Z) and on a dimension of the r.f. treatment electrode () in the contact plane, the treatment settings comprising at least one of a treatment duration (T) associated with a desired treatment result, and an r.f. electrical parameter associated with the r.f. treatment signal. The skin treatment device () further comprises a controller () configured and arranged to consecutively activate the impedance measurement circuit () and the treatment settings determiner () before treatment of the inner region (), configure the r.f. generator () to provide the r.f. treatment signal according to the treatment settings, and activate the r.f. generator () to apply the r.f. treatment signal to the inner region () for the treatment duration (T). The invention is based on the insight obtained from multiple measurements made during the creation of microscopic thermal lesions in an inner region of skin by applying r.f. measurement and treatment signals. By analyzing the histological and heating results, a relationship was obtained between the initial impedance (Z), the dimension of the r.f. treatment electrode (), and the treatment settings required to obtain a particular skin treatment result. This relationship has been found to be relatively constant for different subjects, different treatment locations on the body and different skin moisture contents. The invention makes it possible to preset or predetermine, i.e. in advance, the treatment duration (T) and/or the r.f. electrical parameters associated with the r.f. treatment signal accurately enough to avoid undesired skin damage during the treatment. The device can be simpler, as it is no longer essential to continuously monitor the impedance during treatment to determine the onset of undesired skin damage, such as ablation, which is the safety feature known from conventional devices.