CVT 102

 Time  Distance  Shielding

 Establish standard protocols (including limits on fluoroscopic exposure time)  Know dose rates of equipment  Assess procedure protocol for potential radiation injury  Modify procedure to limit cumulative radiation dose  Medical physicist should help implement principles

 Pulsed fluoroscopy  Low tube current ◦ Less radiation, less exposure  Higher kVp –Higher voltage causes radiation to go through patient; less absorption; less skin dose –Balance contrast and distance

 Distance ◦ Keep image intensifier as close to patient as possible ◦ Increase distance from x-ray tube to patient  Field of view ◦ Collimate to reduce field of view to region of interest  Limit use of magnification techniques ◦ Magnification increases patient dose

 Last image hold ◦ Displays last image captured on monitor  Beam on-time ◦ Intermittent fluoroscopy ◦ 5 minute reset timer  Rotate fluoroscope around a center (do obliques and laterals)  Keep other body parts (arms, breasts) out of the x-ray field  Maintain logs to track trends in exposure and analyze problems

 Inverse square law ◦ The exposure is inversely proportional to the square of the distance from the source of radiation (scattered radiation from the patient). ◦ To minimize exposure, stand as far away from the patient as practical  Do not put any part of your body in the primary beam  Distance is the most important method of protection

 Reduce the time you are exposed to radiation ◦ Fluoroscopist should use intermittent fluoroscopy ◦ Minimize beam-on time  5 minute audible timer ◦ High dose fluoroscopy requires audible signal while on ◦ Use last image hold ◦ Use pulsed technique

 Lead aprons (.5mm Pb equivalent)  Thyroid collars  Lead gloves  Leaded glasses

 Dose limits ◦ Whole body – 5,000 mrem/year (50 mSv) ◦ Skin, hands, feet – 50,000 mrem/year (500 mSv) ◦ Cumulative – 1,000 mrem (10 mSv) X age in years  Monitors worn on collar outside the protective aprons  Interventional personnel use additional monitor at waist level under the lead apron

 The National Council on Radiation Protection and Measurements recommends using the ALARA (As Low As Reasonably Achievable) principle ◦ Try to keep exposure to less than 1/10 recommended dose limit

Exposure levels—CR vertical, PA projection, intensifier on top. *† (Least exposure to operator) Vertical orientation with tube on top (increases exposure to head and neck of operator —NOT recommended.  operation

Exposure levels—CR 30° from vertical. *† (CR angle increases exposure to operator) Exposure patterns and levels—CR horizontal.*† (Least exposure at intensifier side)