As the Greek philosopher and natural scientist Aristotle pondered the enigmatic parts and organs of the human body, he postulated that the brain was made up of the elements earth and water. Today – almost 2,400 years later – we have gained numerous fascinating insights into our nervous system and the jelly-like mass inside our head. Weighing approximately 1.4 kilograms, our brain is made up of around 100 billion nerve cells, linked up to one another by some 100 trillion junctions. The neural pathways in an adult human have a total length of approximately 5.8 million kilometers or about 145 times the circumference of planet Earth. Our central nervous system controls bodily processes via electrochemical signals that travel through our brain and spinal column at over 300 kilometers an hour. Using X-rays to depict these complex structures as accurately as possible – so that physicians can use the images to diagnose diseases – represents an enormous technical challenge.
Wilhelm Conrad Röntgen discovered X-rays on November 8, 1895, and the first images of the skull appeared soon afterwards. With an exposure time of an hour, these images allowed physicians to estimate where a bullet was lodged inside a patient’s head following a gunshot wound, for example. Still it was not until two decades later, by which time over 200 methods had been trialed, that diagnostically relevant X-rays could be taken of the brain: In the procedure known as pneumoencephalography, cerebrospinal fluid was extracted via the patient’s lumbar spine and replaced with air, gas, or iodized oil. The subsequent X-ray image showed a relatively clear distinction between the air and the brain tissue. In addition to tumors, this allowed physicians to visualize and assess issues such as swelling and, under certain circumstances, even cerebral hemorrhages. However, pneumoencephalography was associated with a number of serious side effects. Apart from several days of vomiting and severe headaches, it could also lead to seizures or even encephalitis.
Pneumoencephalography remained the most important tool for localizing brain tumors until the 1970s; by this stage, the X-ray equipment designed especially for this technique – such as the Siemens MIMER III – had achieved a remarkable degree of technical sophistication, with numerous automatic programs as well as X-ray tubes optimized for imaging the brain. Siemens opted not to continue developing the sophisticated specialized functions for pneumoencephalography found in MIMER III – because this painful procedure would soon be rendered superfluous by a completely new and unexpected invention: computed tomography.
Computed tomography completely transformed the field of neuroradiology and quickly became the method of choice for examinations of brain tissue. Just two years after the SIRETOM cranium scanner, Siemens presented its first whole-body CT scanner, SOMATOM. Now, neurologists could also refer to slice images of the spinal cord and other nervous system structures when making their diagnoses. Image quality improved considerably within the space of a few years, as illustrated by the two brain scans below. The image on the left is from 1974, whereas the image on the right was taken with the SOMATOM of 1983. Although the older image allowed physicians to detect and localize larger tumors or hemorrhages, the image taken almost ten years later provided a clear view of detailed brain structures and the optical nerves.
Thanks to modern imaging procedures, disorders can now be identified with a high degree of accuracy, and lesions such as tumors can be localized with millimeter precision. Using X-rays, modern angiography systems such as ARTIS icono can visualize regions near the top and base of the skull almost without any picture noise. This field is known as precision medicine and uses robot-supported minimally invasive techniques that shorten treatment times and improve treatment accuracy. The interplay between accurate imaging and high-precision robotics, supported by increasing digitalization and artificial intelligence, will continue to improve treatment methods in coming years.