Seite - 53 - in Cyborg Mind - What Brain–Computer and Mind–Cyberspace Interfaces Mean for Cyberneuroethics

Neuronal Interface Systems • 53 Computed Tomography (CT) Adding computers to X-rays enabled more information to be obtained, since X-rays can come in many different power settings showing up different kinds of soft tissue. Thus, a Computed Tomography (CT) scanner can take thou- sands of horizontal brain images, in sections, using varying levels of X-rays that can then be used by a computer to build up these fragments of infor- mation to create a picture. With enough scans, it is even possible to create a three-dimensional image of the whole brain. The first clinical CT scan on a patient took place in 1971 in England.30 The patient had a suspected frontal lobe tumour and the scanner produced an image with a sufficient amount of detail to see the growth. Since then, image quality has improved and CT has become a valuable clinical tool. For example, it is used in many hospitals throughout the world to immediately assess the results of a stroke or head injury, since it has the ability to quickly detect bleeding within the skull. Moreover, CT scans can be used to look for brain tumours in a person or to better evaluate, in more detail, abnormali- ties seen in normal X-rays. However, it is worth noting that for research and increasingly many clinical purposes, CT has now generally been replaced by Magnetic Resonance Imaging (MRI). Positron Emission Tomography (PET) Positron Emission Tomography (PET) scans were developed in the 1970s and have revolutionised the understanding of how the brain works. The procedure requires a patient to lie in a scanner, while radio-labelled trace particles, such as a radioactive form of oxygen, are injected into the blood to be used as markers. The scanner then detects the radioactivity of the tracer molecules, thereby creating real-time images of the concentration of these tracers in different parts of the body. When it is used to look at the brain, PET may reveal which areas are most active while a person performs specific tasks. For example, it is possible to ask a person to imagine doing nothing or playing tennis. The computer can then compare the two sets of images, making it possible to distinguish an increase in radioactivity in a particular area that is related to the blood flow changes resulting from brain activity. In other words, the rise in radioactiv- ity in a certain region indicates that the brain is working harder and calling in more oxygen. While such assumptions are probably correct, a difficulty exists in that it is usually a whole area of the brain that ‘lights up’. PET scans can therefore provide information about general function, but give little or nothing in the way of fine detail. This open access edition has been made available under a CC-BY-NC-ND 4.0 license thanks to the support of Knowledge Unlatched. Not for resale.