FoundationalConceptsNeuroscience

individual who has the lesion. Historically, it was necessary to wait
until after a person died to examine the brain and attempt to locate
any lesions. A big breakthrough occurred with the advent of x-ray
technology and its application to visualizing the internal structure of
living bodies. X-rays are a kind of electromagnetic radiation having
energy substantially higher than that of visible light or ultraviolet
light. X-radiation was first described at the end of the nineteenth
century by Wilhelm Réntgen (1845-1923), who received the very first
Nobel Prize in Physics in 1901 in honor of his discovery. Because of
their high energy, x-rays can penetrate many kinds of solid matter.
Not long after R6ntgen’s discovery, people figured out how to use x-
radiation to take photographs of the interior of a living body. Because
bone is less permeable to x-rays than the surrounding tissue, it was
most easy to visualize the skeletal structure inside a body and detect
the location and nature of damage, such as a broken bone. With finer
tuning of the amount of radiation used, technology was developed
that permitted visualization of different kinds of organ tissue on an
x-ray photograph. Tissue abnormalities associated with brain lesions
became detectable on x-ray photographs of the head and brain.
While a simple x-ray photograph may permit a brain lesion to be
seen, it is limited in its ability to locate the lesion. Increased precision
is obtained by taking a series of x-ray photographs from different
angles and then combining the resulting images to construct a three-
dimensional picture of the brain. The advent of sufficiently powerful
computers allowed this to be accomplished beginning in the late
1960s. The result is a CT scan—C for computed (using a computer) and
T for tomography (making a series of images, essentially of slices of the
brain), sometimes referred to as a CAT scan, with A for axial (the slices
are along a central axis of symmetry of the brain). A CT scan is a so-
phisticated x-ray imaging process that generates a three-dimensional