Module 3.2: Brain Imaging
-Provides an image of the structure of the brain
The precise location of abnormalities
X-rays (useful for medical imaging)
-Rays capable of penetrating solid materials, including wood, metal, and human tissue.
Describes the nature of the entry wound
Can be used therapeutically to destroy unwanted tissues, such as cancerous growth.
Useful when looking for bone fractures
Cannot differentiate between cerebrospinal fluid and brain structures very well
-Neuroradiology – studying the nervous system with imaging
-The more dense the material, the less penetrable the substances is to X-rays.
Computed tomography (CT)
-A means of imaging live brain tissue that combines X-ray technology with computing.
Involves the projection of X-rays from multiple angels followed by the computerized
reconstruction of the measures into three-dimensional (3-D) images.
Provides measurement of densities of various tissues (differentiation between white and
gray matter is rather poor)
Can be performed on an unconscious individual
-Computed axial tomography (CAT)
Axial refers to images being constructed in one plane, the axial plane (horizontal plane)
Most early CT images were constructed in this plane, but now they are often constructed
in two other planes as well.
Coronal plane – show slides perpendicular to the horizon, taken along the superior-
Sagittal plane – perpendicular to the horizon, taken along the dorsal-ventral axis.
-Some brain tumors can have densities very similar to those of the surrounding tissues, making
them difficult to detect on CT scans.
Magnetic resonance imaging (MRI)
-Method for studying tissues using magnetic fields and radio receivers
-When placed in a strong magnetic field, the atoms become aligned – the north poles on all the
atoms point in the same direction. Atoms can be perturbed in a uniform direction through the
application of a radio frequency pulse.
-MRI machine measures the relaxation time, that follows the pulse, which is the time taken by
the atoms to return to their normal, random state. MRI’s receiver coil measures the
information about the intensity of the signal, but the spatial information is provided from
variations in the gradient field. (combination of these two types of information allows the
construction of 3-D images of the brain)
Different substances relax at different rates along these dimensions. >> images of T1