Uncertainty assessment of target localization for rTMS treatment

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive method for treating various neurological and psychiatric disorders. This paper focuses on a technical aspect of this treatment method for neuropathic pain that can be caused by a lesion or disease of the central or peripheral nervous system, including stroke, trauma or surgical operation. rTMS uses electromagnetic induction to induce weak electric currents by rapidly changing the magnetic field. Targeting a specific part of the brain to locate the magnetic field works as a treatment for pain relief. This is the reason why the current style of rTMS treatment is still developing and is so technically specialized that only a limited number of hospitals and only a handful of specialists can provide this therapy. The existing systems of rTMS are based on an optical maker-based 3-dimensional (3D) sensing technique for positioning the stimulation coil to target the small spot in the region of interest in the brain, and for referring pre-scanned MRI data to check the target position. Furthermore, the existing systems require the patient to be fixed on a bed in which optical markers for 3D sensing are placed during the treatment to maintain positioning precision. With the growing demands of neuropathic pain patients and their increasing numbers, new approaches and systems to achieve more supportive and easy-to-handle navigation have been proposed lately for rTMS treatment. This paper proposes a quantitative index for localization precision, considering an uncertainty measure. Uncertainty is technically defined as a parameter, associated with the result of a measurement that characterizes the dispersion of the values that could reasonably be attributed to the measurement. This paper shows a detailed example of the uncertainty derivation for rTMS treatment, based on trial tasks for searching the spots on the brain that cause muscle twitch.