A myelography is a radiographic imaging procedure to visualize the spinal canal, the spinal cord, cerebrospinal fluid (CSF), intervertebral disks and nerve roots. A special contrast agent (dye) is injected through a needle into the subarachnoid space of the spinal canal. A myelogram provides a very detailed picture of the spinal cord and spinal column. A fluoroscopy displays the bones and the fluid-filled space of the spine also in motion. An additional computerized tomography (CT or CAT) scan helps to differentiate the spinal conditions better. The indications include disc herniation, spinal stenosis, tumor, and vertebral fracture.

See also Myeloscintigraphy, Fluoroscopic System, Hounsfield Unit, Bone Densitometry, Nonionic Contrast Agents.

Optiray® is a radiographic contrast agent. Optiray® is available in concentrations from 160 to 350 mg/mL organically bound iodine. Optiray® solutions have osmolalities 1.2 to 2.8 times that of plasma (285 mOsm/kg water).
Optiray® 160 is recommended for intraarterial digital subtraction angiography (IA-DSA).
See also Single-Head Contrast Media Injector, Dual-Head CT Power Injector, Syringeless CT Power Injector.

Oxilan® is a radiographic contrast agent used in diagnostic imaging studies. The degree of contrast enhancement is directly related to the iodine content in the administered dose. Dependent on the iodine content, the osmolalities are 2.1 or 2.4 times that of plasma (285 mOsm/kg water).

A phantom is an artificial object of known size and composition that is imaged to test, adjust or monitor the linearity, sensitivity, homogeneity, imaging performance and geometric aspects of CT scanners, gamma cameras or other radiographic systems. A phantom can be a fluid-filled container or bottle including structures of various materials, sizes and shapes.

See also Daily Quality Assurance and Acceptance Checking.

The photoelectric effect describes the following interaction of electromagnetic radiation with a metallic surface: a photon with an energy (frequency) above the binding energy of an electron gets absorbed and the electron is emitted. The positive energy difference is transferred to the electrons kinetic energy. If the photons energy is not high enough for the electron to overcome its binding forces, the photon will be re-emitted. It is not the intensity of a photon beam (amount of photons) which allows the photoelectric effect; it is the energy (frequency) of a single photon which will allow the emission of a single photoelectron.
The discovery and study of the photoelectric effect leads to a new quantized understanding in physics. Albert Einstein was awarded the Noble prize for physics in 1921 'for his services to theoretical physics and especially for his discovery of the law of the photoelectric effect'.
The photoelectric effect is the most important effect in medical radiography. E.g. it is photoelectric absorption that is responsible for most of the absorption in a mammogram which creates the contrast in the image.

See also Photon, Electron.