Minimizing Exposure to Personnel Flashcards
Devices for Operator Protection that should be used with fluoroscopy
- Full use must be made of the protective devices provided with X-ray equipment such as shielded panels, drapes, bucky slot covers, ceiling-suspended lead acrylic screens, etc.
- Full wrap around type protective gowns of 0.50 mm Pb in the front panels and 0.25 mm Pb in the back panels are recommended.
- Protective thyroid shields with an equivalent of 0.50 mm Pb are recommended.
- In the situation where scatter radiation to the lenses of eye could approach the annual equivalent dose limit of 20 mSv, the use of leaded glasses is recommended.
- May have additional TLD badges worn outside of aprons
Fluoroscopy and Scatter
- The exposure rate caused by scatter near the entrance surface of the patient exceeds the exposure rate caused by scatter near the exit surface of the patient
- The location of the lower potential scatter dose is on the side of the patient away from the x-ray tube
Shielding during fluoroscopy
- Scattered radiation produced during a fluoroscopic examination can be absorbed by a spot film device protective curtain, or sliding panel, with a minimum of 0.25-mm lead equivalent placed between the fluoroscopist and the patient
Dose reduction techniques dure fluoroscopic procedures
- Adequate beam collimation
- PPE’s
- Adequate filtration
- Adequate gonadal shielding
- Control of technical exposure factors
- Use of high-speed image receptor systems
- Appropriate source-to-skin distance (SSD)
- Use of a cumulative timing device
- Diagnostic-type protective x-ray tube housing
- Standing in the appropriate place
- Proper orientation of tube/IR
Maximum permissible levels of radiation exposure
- Radiation dose in excess of 1/20th of the whole body dose limit to radiation workers, must be monitored with personal dosimeter
- When a protective apron is worn, the personal dosimeter must be worn under the apron
- If extremities are likely to be exposed to significantly higher doses, additional dosimeters should be worn at those locations on the body
Annual Dose limits for radiation workers
Whole body - 20 mSv
Lens of the eye - 20 mSv per year averaged over a 5 year period, 50 mSv in any single year
Skin - 500 mSv
Hands - 500 mSv
All other organs - 500 mSv
Annual Dose limits for members of the public/students
Whole body - 1 mSv
Lens of the eye - 15 mSv
Skin - 50 mSv
Hands - 50 mSv
All other organs - 50 mSv
Distance in reducing personnel dose
- Most effective means of protection from ionizing radiation
- Imaging personnel receive significantly less radiation exposure by standing farther away from a source of radiation because there is a significant decrease in the radiation level.
- Application of the Inverse Square Law (ISL
- need to stand at least 3 metres or 9 feet away from x-ray tube for mobile x-rays
application of inverse square law when at a right angle from the tube?
At a 90-degree angle to the primary x-ray beam at a distance of 1 m, the scattered x-ray intensity is generally approximately 1/1000 of the intensity of the primary x-ray beam
Time in reducing personnel dose?
- The amount of radiation a worker receives is directly proportional to the length of time for which the individual is in the path of ionizing radiation.
- Rotational scheduling of personnel: Diagnostic imaging personnel who receive the highest occupational dose during exposure
Shielding in reducing personnel dose
- used when it is not possible to use the principles of time and/or distance to minimize occupational exposure
classic lead lined glasses are better than sport wrap why?
because better at blocking any radiation that may be hitting you from the side
Dose reduction methods
- avoiding repeat examinations
- filtration of the diagnostic x-ray beam
- adequately collimate radiographic beam
- appropriate technical exposure factors
Types of shielding
All personnel must use available protective devices (SC35)
Wall Barriers/ Control Booth
Operator/Patient
Wall barriers/control booth shielding
Pb, concrete, lead-glass
Entrance to control booth: x-rays should scatter at least twice before entrance
Personnel must remain completely behind the barrier
Exposure cord must be short enough that the exposure switch can be operated only when the radiographer is completely behind the control-booth barrier.
Operator/patient shielding
Aprons, gloves, thyroid shields
Pb-rubber
Controlled area
Occupied ONLY by occupationally exposed
- Radiation levels for Controlled Areas: Same as
- occupational DL
- control booth
- processing areas
- corridors used only by personnel
Uncontrolled areas
Pubic/Others
- radiation level: 1mSv/yr
Reducing exposure for imaging professionals
Direct radiation exposure of personnel by the primary X-ray beam must never be allowed. (SC35)
The patient as a source of scattered radiation
- During a diagnostic examination, the patient becomes a source of scattered radiation as a consequence of the Compton interaction process.
- operators SHOULD not hold patients
- Pregnant women are never to be permitted to assist in holding a patient during an exposure.
Pointing the beam
always try for unoccupied areas or point towards primary barriers
Secondary barriers
never expose a secondary barrier with primary beam
- control booth is a secondary barrier
