Luminescence Process In Radoigraphy
Luminescence
It refers to the emission of light by a substance when stuck by electromagnetic radiations (x-rays).
It is caused by various kinds of stimuli-
- Light
- Chemical Reactions
- Ionizing Radiations
Types
- Fluorescence
- Phosphorescence
Fluorescence
Refers to the emission of light (production of luminescence) by a substance when ionizing radiation strikes on it (fluorescent materials).
In this case light is emitted instantaneously ( at a time only) within 10⁻⁸ sec of the stimulation.
Fluorescent Materials
1. Conventional type:
- Inorganic Phosphors (inorganic salts)
- Calcium tungstate (phosphor in intensifying screens)
- Copper-activated zinc cadmium sulfide (phosphor in fluoroscent & photofluorographic screens)
2. Modern type:
- Cesium iodide (image intensifier tubes)
New- intensifying screen phosphors:
- Silver-activated zinc cadmium sulfide, Barium strontium sulfate, Yttrium and Rare earths gadolinium & lanthanum
Uses
- Use for Fluoroscopy Imaging in Medical Imaging Department.
- Used in Radiological Special Procedures (intensifying screens, image intensifier etc.)
- Used in Digital Radiography.
Phosphorescence
It refers to the emission of light (production of luminescence) by a substance when ionizing radiation strikes on it or passes through it, after some time it emits light.
Also called afterglow. In this case the emission of light is delayed beyond 10⁻⁸ sec of stimulation.
Phosphorescent Materials
- Europium-activated barium fluoro halide (PSP/IP)
- Lithium fluoride (TLD)
- Lithium borate, calcium fluoride, calcium sulphate, calcium furate (TLD)
Uses
- Used in Computed Radiology (PSP/IP).
- Useful for detection & measurement of radiation dose (personnel dosimeter such as TLD).
By – Assistant Professor – Mr. Binoo
Radiology Department
Uttaranchal (P.G.) College Of Bio-Medical Sciences & Hospital