trigeminal neuralgia by inserting an electrode into the trigeminal nerve and ablating it. He published this in 1933. In 1947 and 1949, two neurosurgeons working at Temple University in Philadelphia, Ernest A. Spiegel (who had fled Austria when the Nazis took over) and Henry T. Wycis, published their work on a device similar to the Horsley–Clarke apparatus in using a cartesian system; it was attached to the patient's head with a plaster cast instead of screws. Their device was the first to be used for brain surgery; they used it for psychosurgery. They also created the first atlas of the human brain, and used intracranial reference points, generated by using medical images acquired with contrast agents. The work of Spiegel and Wycis sparked enormous interest and research. In Paris, Jean Talairach collaborated with Marcel David, Henri Hacaen, and Julian de Ajuriaguerra on a stereotactic device, publishing their first work in 1949 and eventually developing the Talairach coordinates. In Japan, Hirotaro Narabayashi was doing similar work. In 1949, Lars Leksell published a device that used polar coordinates instead of cartesian, and two years later he published work where he used his device to target a beam of radiation into a brain. Leksell's radiosurgery system is also used by the Gamma Knife device, and by other neurosurgeons, using linear accelerators, proton beam therapy and neutron capture therapy. Lars Leksell went on to commercialize his inventions by founding Elekta in 1972. In 1979, Russell A. Brown proposed a device, now known as the N-localizer, that enables guidance of stereotactic surgery using tomographic images that are obtained via medical imaging technologies such as X-ray computed tomography (CT), magnetic resonance imaging (MRI), or positron emission tomography (PET). The N-localizer comprises a diagonal rod that spans two vertical rods to form an N-shape that allows tomographic images to be mapped to physical space. This device became almost universally adopted by the 1980s and is included in the Brown-Roberts-Wells (BRW), Kelly-Goerss, Leksell, Cosman-Roberts-Wells (CRW), Micromar-ETM03B, FiMe-BlueFrame, Macom, and Adeor-Zeppelin stereotactic frames and in the Gamma Knife radiosurgery system. An alternative to the N-localizer is the Sturm-Pastyr localizer that is included in the Riechert-Mundinger and Zamorano-Dujovny stereotactic frames. Other localization methods also exist that do not make use of tomographic images produced by CT, MRI, or PET, but instead conventional radiographs. The stereotactic method has continued to evolve, and at present employs an elaborate mixture of image-guided surgery