Radiation Protection in Medical Radiography

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Wendy Wiredu
XRA 230

A. PERSONNEL PROTECTION
* Primary X-Ray Beam
* Emerges directly from the x-ray tube collimator.
* It moves without deflection (toward a wall, door, viewing window, etc). * Primary radiation is also known as direct radiation.

* Secondary Radiation (aka Scatter radiation & Leakage Radiaiton) * Scatter Radiation – results whenever a diagnostic x-ray beam passes through matter. * Compton interactions between the x-ray photons and the electrons of the atoms within attenuating object deflect x-ray photons from their initial trajectories. * X-ray photons emerge from the object in all direction. * Leakage Radiation – radiation generated in the x-ray tube that does not exit from the collimator opening but rather penetrates through the protective tube housing and to some degree through the sides of the collimator. * Leakage radiation is always present in some amount.

* Patient as a Source
* During diagnostic examination the patient becomes a source of scattered radiation. * At a 900angle to the primary x-ray beam, at a distance of 1m (3.3 ft), the scattered x-ray intensity is generally approximately 11000 of the intensity of the primary x-ray beam. * Use of any devices and appropriate technique can lessens the amount of scattered radiation and significantly reduce occupational exposure. * Automatic collimation, or positive beam limitation device (PBL), restrict the size of radiographic beam so that its margin do not extend beyond the image receptor. B. Basic Method of Protection

* Time
* The amount of exposure is directly proportional to the duration of exposure. * As the length of exposure time increases, the radiation dose received increases in direct proportion. * During fluoroscopy, reduced exposure time will decrease both the patient and personnel exposure. * Fluoroscopic x-ray units are equipped with 5 minute timers to alert the radiologist or other authorized equipment operator that a specific period of time has elapsed. * The effectively minimize radiation exposure use the cardinal principle of time.

* Distance
* Is the most effective protection from ionizing radiation. * Dose is governed by the inverse square law.
* The greater the distance from the radiation, the lower the dose. * Dose varies inversely according to the square of the distance.

* Shielding
* Lead equivalent shielding absorbs most of the energy of the scatter radiation. * A lead apron of at least 0.25mm lead equivalent must be worn. * 0.5mm lead equivalent should be worn during exposure to scatter radiation. * Thyroid shield of at least 0.5mm lead equivalent should be worn for fluoroscopy * The radiographer should never be exposed to the primary beam.

C. Protective Devices
* Types
* Protective lead aprons and shielded barriers function as gonadal shields for diagnostic imaging personnel. These devices protect personnel from secondary (scatter and leakage) radiation. * Structural barriers provide radiation shielding for both imaging personnel and the general public.

* Attenuation Properties
* Primary protective barrier prevent direct, or unscattered radiation from reaching personnel or the general public on the other side of the barrier * Primary protective barriers are located perpendicular to the undeflected line of travel of the x-ray beam. * Secondary protective barriers protect protects against secondary radiation (scatter and leakage) radiation. * Any wall or barrier that is never struck by the primary x-ray beam is classified as a secondary barrier. * X-ray rooms housing stationary (fixed) radiographic equipment contains a control booth for the protection of the radiographer.

* Minimum Lead Equivalent
* If the peak energy is 130 kVp, the primary protective barrier in a typical installation consists of...
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