Design of a stimulation protocol to predict temperature distribution in subcutaneous tissue using the finite element model

Computational Modeling of Deep Tissue Heating by an Automatic Thermal Massage Bed: Predicting the Effects on Circulation

Automatic thermal and mechanical massage beds support self-managed treatment, including reduction of pain and stress, enhanced circulation, and improved mobility. As the devices become more sophisticated (increasing the degrees of freedom), it is essential to identify the settings that best target the desired tissue. To that end, we developed an MRI-derived model of the lower back and simulated the physiological effects of a commercial thermal-mechanical massage bed. Here we specifically estimated the tissue temperature and increased circulation under steady-state conditions for typical thermal actuator settings (i.e., 45-65°C). Energy transfer across nine tissues was simulated with finite element modeling (FEM) and the resulting heating was coupled to blood flow with an empirically-guided model of temperature-dependent circulation. Our findings indicate that thermal massage increases tissue temperature by 3-8°C and 1-3°C at depths of 2 and 3 cm, respectively. Importantly, due to the rapid (non-linear) increase of circulation with local temperature, this is expected to increase blood flow four-fold (4x) at depths occupied by deep tissue and muscle. These predictions are consistent with prior clinical observations of therapeutic benefits derived from spinal thermal massage.

Depth of thermal dispersion of monopolar radiofrequency heating in the vaginal wall

The use of energy-based devices to treat genitourinary syndrome of menopause, termed vaginal thermotherapy (VTT), has gained significant interest in recent years. Among the primary safety concerns of this relatively new procedure is the possibility of unintentionally heating tissues adjacent to the vaginal wall, i.e., heating too deeply. Herein we use numerical simulations to evaluate monopolar radiofrequency-based (RF) VTT specifically focusing on the resultant depth of heating through a range of input parameters. Varying RF power, exposure time, and the simulated rate of blood perfusion, we map the parameter space identifying which combinations of input parameters are likely to heat past the depth of the vaginal wall and affect adjacent tissue. We found that the device parameters commonly used in the literature are likely to heat past the vaginal wall and merit further investigation. In addition, we found that the parameter typically used to describe VTT devices, total energy delivered, does not reliably indicate the resultant depth of heat dispersion.