Rad Protection Unit 3- personnel protection

NCRP occupational exposure limits

• annual effective dose

  • 50 mSv

  • does not include medical or background radiaiton exposure

• cumulative effective dose

  • age in years x 10 mSv

ALARA

• concept

  • as low as reasonably achievable

    • collimate

    • technique

    • shielding

    • minimize repeats

methods to reduce exposure

• avoid repeat exposure

• collimation- increase (make light field smaller)

• cumulative timer

• highest occupational exposures are: fluoro, portables, and OR

• stand 90 degrees from the patient

• filtration

  • non useful low energy photons are removed, less scatter

distance from patient…

• patient is a source of scatter radiation

• 3 feet from the patient (1 meter), the scatter radiation is approximately 1/1000 the intensity

• example: if patient exposure is 20 mGy, technologist standing 1 meter at 90 degrees would be exposed to 0.02 mGy

methods to reduce your exposure

• protective apparel

  • lead aprons and protective barries

• proper exposure factors

  • controls scatter (lower kVp, less scatter produced)

• correct image acquisition

  • reduces repeats

• high speed image receptors

  • high speed systems use smaller exposures which causes less scatter

• beam limiting devices

  • reduces scatter

protection of pregnant personnel

• should be able to continue duties without interruption of employment

• voluntary declaring vs. not declaring

  • couseling

  • second “baby badge” is issued worn at waist level

• to reduce risk of leukemia or other malignancies

  • 0.5 mSv in one month

  • 5 mSv for the entire pregnancy

• must read and sign a form acknowledging counseling

• if wearing a lead apron, the 2nd badge is worn inside the apron at waist level

• baby badge has a separate reading on the dose report

• maternal tissue decreases fetus dose by 30%

• work schedule rotation

  • does not necessarily have to be done

types of radiation

• primary radiation

• scatter radiation

• leakage radiation

primary radiation

• useful beam

• emerges directly from the tube collimator

scatter radiation

• highest does to technologist

• primary beam passes through matter and goes in various directions

leakage radiation

escapes the tube housing

protective structural shielding

• usually lead or concrete

• barriers

  • primary protective barrier

  • secondary protective barrier

primary protective barrier

• located perpedicular to the primary beam travel (undeflected line of travel)

• prevents direct or unscattered radiation from reaching personnel and general public

• for 130 kVp of peak energy a 1/16 (~1.6mm)inch of lead or lead equivalent and extends 7 feet (2.1m) upward from the floor if the tube is 5-7 from the wall (1.5-2.1m)

secondary protective barrier

• any wall or barrier that is never hit by the primary beam

• protects agaist scatter and leakage radiation

• 1/32 inch of lead or lead equivalent (~0.8 mm)

• overlaps the primary barries by ½ inch (~1.3 mm) and extends to the ceiling

protective device requirements

• lead apron

  • 0.5 mm lead (Pb) for fluroscopy, AIR, or operating systems aboe 100 kVp (NCRP #102)

    • protects from 95-99% of scattered radiation

• gloves

  • minimum of 0.25 mm lead (Pb)

• neck and thyroid

  • must be at least 0.5 mm lead (Pb)

• protective eyeglasses

  • 0.35 mm lead (Pb) to protect the eyes

protective tube housing

• lead lined metal that protects personnel and patients from leakage and off focus radiation

• cannot exceed 1 mGy per hour at 1 m away from housing

• no one should be touching the xray tube housing during an exposure

protection during fluoroscopy

• proper position to be standing

  • avoid high scatter areas

  • try to stand behind the physician/ radiologist or RA

  • 90 degrees from the patient, away from the source

• wrap around lead

  • need to move around the room to obtain supplies

• should be thyroid shield

  • unprotected areas are getting 10-20x more exposure

• collimation

• filtration

• technical factors

• high speed image receptors

• correct image acquisition

• appropriate skin to source distance

• cumulative timer

• rotational scheduling of personnel

• personnel must wear the badge on the outside of the lead apron at collar level

remote control fluoro units

can perform the study from the control booth and enter room only when necessary

scatter protection barrier in fluoro

• protective curtain

  • 0.25 mm lead equivalent

gonadal protection

• bucky slot cover

  • 0.25 mm lead equivalent

protection in mobile radiogrpahy

• cord length should be long enough to stand 6 feet (2m) from the patient

• stand 90 degrees from the patient

• use distance as a means of protection

• wear protective shield

• yell “x-ray” before taking exposure

• do not hold the image receptor

  • use cassette holders, pillows, sponges, or even a box of gloves

protection in C-arm fluoroscopy

• proper position to be standing

  • in a lateral view, on the side of the patient away from the x-ray tube

• protective shields and radiation monitros for all personnel

• properly orient the c-arm with the image intensifier on top

• minimise beam on time

• position the image intensifier as close to the patient as possible to lower the beam intensity needed

advanced interventional radiology (AIR) protection

• low dose fluoroscopy mode/ pulse fluoro

• collimation

• last image hold

• shortening duration of studies

• extremity monitors

  • rings- NCRP annual limits to 500 mSv

imaging personnel protection guidelines

• technologist should never stand in the path of the primary beam

• if holding is necessary, try to utilize a non-occupationally exposed person or immobilization

• pregnant technologist technologist are never to hold a patient for an exposure

• exposures should never be made witht the doors to room open

cardinal principles of radiation protection

• Time- amount of exposure is directly proportional to duration of the exposure

• Distance- most effective means of protection, it is indirectly proportional

• Shielding- absorbs most of the energy of scatter radiation

  • ~ 85% effectiveness

Inverse square law (ISL) equation

diagnostic protection design

• workload (W)

  • radiation on time during a week

  • mAs/week or mA- minute/week

• Use (U)

  • amount of time the bean is directed at the structure'

  • takes into account primary or secondary radiation

• occupancy (T)

  • time that the area is occupied behind a barrier

    • waiting room

    • empty courtyard

• distance (D)

  • distance from the source to the structure

calculating barrier requirements

• W x U x T

  • needs to be calculated for every barrier in an x-ray room

areas of the department

• controlled- occupied by workers who are trained and wearing monitoring devices; maximum permitted equivalent dose is 100 mrem per week

• uncontrolled- occupied by the general public; maximum permitted equivalent dose is 2 mrem per week

  • waiting rooms

  • hallways

  • bathrooms

  • stairways

radiation area sign posting

• radiation symbol that is magenta, purple or black on a yellow background

• radiaiton hazard (rad Onc and NM)

  • high radiaiton area

  • very high radiaiton area

  • Airborne radioactivity

  • radioactive materials

warning signs

signs that indicate the room is in use