Tumor Treating Fields (TTFields) is a tissue ablation technology that inhibits the uncontrolled growth of cells in the body, such as cancer cells, with non-contact electromagnetic fields. Electrodes attached to the skin, such as on a shaved skull, deliver the electromagnetic fields. In order to achieve a therapeutic effect, this minimally invasive cancer treatment must be delivered continuously, over a long period of time. The therapy is monitored with MRI imaging, every one to three months.In between MRI scans, the effects of treatment can be monitored through additional electrodes attached to precise locations on the skin. For example, when treating the brain, electrodes tightly attached to the skull can detect changes in the complex electrical impedance of the monitored tissue. Data collected from the electrodes can be also used to control and optimize treatment parameters.