Radiology is one of the most common diagnostic tools used today, and the plain film X ray is the most well-known and widely-used form of radiology. X rays rely on three key principles to create the images needed for diagnostic purposes: the ability to create electromagnetic radiation at the appropriate wavelength, the capacity to focus radiation on the required area, and the capability of the radiation to be detected once it has passed through a patient's body.
Different tissues absorb X rays differently, with higher density tissues, such as bones, absorbing a greater amount of X rays, and thus appearing white on the X ray. Conversely, low-density tissues, such as the lungs, absorb fewer X rays, thus appearing black on the X ray.
Computerized tomography (CT) scans are a form of radiology which uses a combination of X rays taken at different angles to produce a 3D image of the body. As with plain film X rays, high-density tissues absorb more of the radiation, while low-density tissues absorb less. Contrast agents can be injected into the patient to enable better visualization of the cardiovascular system, for example.
Magnetic resonance imaging (MRI) is excellent at visualizing soft tissue and is often used to detect tumors and other soft tissue masses. MRI images can be presented in three planes: sagittal, coronal, and transverse. Depending on the weighting of the image, different soft tissue structures can appear either bright or dark.
T1 weighted images are ones in which fat appears bright while fluid appears dark. On the other hand, T2 images represent fluid as bright and fat as dark.
