radiation protection: management of imaging personnel radiation dose

federal government follows _______ recommendations, oermitting diagnostic imaging personnel to recieve an annual occupational effective dose of _________ for whole body exposure

NCRP

50 mSv

lifetime effective dose

cumulative dose limit (CumEfD)

measured in mSv

occupational EfD

50 mSv

countinous or frequent expsosures from artificial sources other than medical and natural background radiation

1 mSv

infrequent annual exposure

5 mSv

allowing workers to recieve more radiation than the general public is allowed because they will not significantly cause an increase in disease in the population as a whole,

they will not alter the GSD dose

areas that increase the radiographers risk of expsoure

general fluoroscopy

interventional procedures with HLCF

mobile exams

c arm fluoroscopy

ALARA

as low as reasonably achievable

apply ALARA to radiation control procedures by

utilizing time, distance, sheilding

adequately collimating the radiographic beam

dose reduction methods and techniques

avoiding repeat imaging

the patient as a source of scattered radiation

at 90 degree angle to the primary xray beam, at a distance of 1 m, the scattered xray intensity is generally approximately 1/1000th of the intensity of the primary xray beam

-1/1000 the intensity or .1% the intensity boards can ask either way

scattered radiation- occupational hazard

reduced the size of the radiographic beam, this reduces the number of xray photons available to undergo compton scatter= reduced occupational dose

filtration of the diagnositc beam primarily benefits the

patient

protective apparel

protect personnel from both scatter and leakage radiation- types of secondary radiation

lead aprons come in various thickness, standard is

0.5 mm lead equivalent

-can be made at .25 mm but the NRCP guideline is .5 mm

technical exposure factors- use higher kVp techniques

-increases the mean energy of the photons comprising the radiographic beam, decreasing large angle scatter

-requires less mAs, less scatter production

repeats in digital image

take care to position correctly the first time

radiographers must ______ stand in the _________ to restrain a pt during a radiographic exposure

never

primary beam

use pt restraint to

immobilize the pt when possible

use non occupational person, preferably

male or person of non childbearing age to hold when necessary

protection for pregnant personnel- imaging department protocol

worker should declare pregnancy

RSO will provide fetal radiation dosimeter

protection for pregnant personnel- additional dosimeter will ensure that the ________ EqD to the embryo- fetus does not exceed _______

monthly

.5 mSv

ALARA guidelines have all workers

rotating equally to distribute radiation exposure risk evenly to all employees

work schedules alterations- if a pregnant worker is pulled from a rotation, then the rest of the staff need to rotate more frequently, __________________________. therefore, a declared pregnant radiographer dose ____________ to be reassigned to a lower radiation exposure position

increasing their overall risk

does not need

3 basic principles of radiation protection- cardinal principles

time

distance

shielding

the amount of radiation a worker recieves at a particular location is ________________ to the length of time the individual is in the path of ionizing radiation

directly proportional

time- important in fluoroscopy

fluoroscopic xray units are equipped with 5 min timer alerts

what is the most effective means of protection from ionizing radiation?

distance

personnel will receive significantly less radiation exposure by standing

farther away from a source of radiation

to reduce exposure, follow the

inverse square law

ISL stands for

inverse square law

ISL expresses the relationship between _______and______of radiation and is a _____ to be used in...

distance and intensity

tool

governing the dose recieved by personnel

shielding

when time and or distance to minimize radiation exposure arent available, then shielding may be used to provide protection from radiation

sheidling structural barriers

lead and concrete

shielding accessory protective devices

aprons, gloves, thyroid shields, eyeglasses

protective structural shielding used to protect

imaging personnel and general public

protective structural shielding

lead sheets of appropriate thickness are placed in the walls of the radiography and fluoroscopy rooms

_______ determines the exact protection requirements needed

physicist

two types of barriers

primary protective barriers

secondary protective barriers

primary protective barriers

protects from primary beam

secondary protective barriers

protects from scatter and leakage

primary protective barriers prevent ______, or ___________ from reaching personnel or members of the general public on the other side of the barrier

direct, or unscattered radiation

primary protective barrier is located

perpendicular to the undeflected line of travel of the xray beam

primary protective layer consists of ____________________ and extands _______________ upward from the floor

1.6 mm (1/16th lead)

2.1 m

secondary protective barrier protects against

leakage and scatter radiation

secondary protective barrier overlaps the primary barrier by __________ and consists of ___________

1/2 an inch

1/32 in lead (.8 mm)

any barrier that is never struck by the primary xray beam is

secondary

control booth barrier

-barrier that protects the radiographer

-expands 2.1 m upward from the floor

-permanenly secured to the floor

xray photons should scatter at least __________ before reaching any area behind this barrier

2 times

control booth barrier exposure will not exceed a maximum allowance of

1 mSv per week

accesory protective devices

aprons, gloves, thyroid shields, protective glasses

come in variety of shapes, sizes, thickness

should be properly stored to prevent cracking

apron with _________ is most widley used and recommended thickness

.5 mm lead equivalent

thyroid shields is used to guard the thyroid during fluroscopy and should be a minimum of _________

.5 mm lead

gloves ______ to be worn when hands are near the fluoroscopic field

.25 mm lead equivalent

protective glasses protect against scatter radiation to the lens of the eye. made of clear lenses that contain _____________, may come with side shields for additional protection

.35 mm lead equivalent

personnel protection to reduce dose from scatter one should:

-stand far away from the pt

-wear a .5 mm lead apron and .25 mm gloves if hands are near beam

-stand behind the radiologist, when possible

dose reduction techniques

adequate beam collimation

adequate filtration

control of technical factors

appropriate source to skin distances

use of timing device

protection tube housing

fluoroscopic protective curtain with minimun of ________ should normally be positioned between pt and fluoroscopist to intercept scatter above _______

.25 mm lead

tabletop

you cant use fluoro curtain when doing

needle work

bucky slot sheild of at least _________ must automatically cover the bucky slot opening in the side of the xray table during __________ fluoroscopic exams when bucky tray is at the foot of the table

.25 mm lead

standing

-protects at the gonadal level

mobile units and safety

some units have a remote control exposure devices, allowing

for more distance

mobile units and safety

cord should be long enough to allow radiographer to stand at least

2 m from the pt, xray tube, and useful beam

protection during c-arm fluoroscopy

position of the c arm can ____________ or ____________ the scatter in the room

increase or decrease

position the c-arm with the xray tube _____ the table and the image intensifier _____ the table results in higher exposure of the pt and ___________

over

under

increased scatter radiation

keep the image intensifier as ______ to the pt as possible, reducing beam intensity and works as a barrier against _______

close

scatter

additional protection during the c arm fluoro

collimate

last image hold

use foot pedal or handheld switch

limit use of boost and magnification

HLCF stands for

high level control fluoroscopy

protection from high level control fluoroscopy (HLCF)

limit boost mode

use low dose or pulse mode operations

manual collimate

time intervals

last image hold

road mapping

limit boost mode

maximum allowed entrance exposure rates:

regular 8.8 cGy/min (10 R/min)

boost mode 20-40 cGy/min

road mapping

vessel contrast studies

ways a radiologist can reduce exposure

-decrease duration of procedure, reduced beam on time

-take fewer digital images

-reduce use of continous fluoro mode

-use last image

radiologist and physicians performing interventional procedures can be subjected to high doses to the exterminites

NCRP recommends an annual EqD limit to localized areas of the skin and hands of 500 mSv

primary radiation

emerges directly from the xray tube collimator and moves without deflection toward a wall, door, viewing window

primary radiation requires the most

protective shielding

scatter radiation

occurs when xray beam passes through matter, undergoes compton interactions, and emerge from the object in all directions

leakage radiation

radiation generated in the xray tube that dose not exit from the collimator opening but penetrates through the protective tube housing

primary barriers

anything that the tube would be pointed at during a procedure

calculation considerations

workload

kVp

inverse square law

use factor

occupational factor

controlled vs uncontrolled

workload (W)

reflects the units radiation on time, which is important for determining barrier sheilding

workload

radiation output- weightied time that the unit is

actually delivering radiation during the week

workload (W) units

mAs per week or mA-min per week

inverse square law helps calculate the

intensity of the beam which is important in design of radiation safety barriers

inverse square law helps determine

primary and secondary barrier thickness values

use factor (U)

quantity that is used to select fractional contact time

use factor- beam direction factor

time that a wall or structure is struck by radiation to some degree for some fraction of weekly beam on time

U (primary)

time the primary beam is directed at a primary barrier during the week

U (secondary)

time scatter and leakage radiation emerged and stuck surfaces

-1 for all radiation- accessible structures (DX)

use factor- because scatter and leakage emerge in all directions in the xray room,

all surfaces will always be struck by some quantity of radiation

occupancy factor (T)

used to modify shielding requirements for a particular barrier by taking into account the fraction of the work week during which the space beyond the barrier is occupied

controlled area

when the region adjacent to a wall of an xray room is used only be occupationally exposed personnel

uncontrolled area

nearby hall or corridor that is frequently by the general public

maximum permitted equivalent dose (MPED)

uncontrolled area MPED is equal to

20 uSv/ week ( microsieverts)

maximum permitted equivalent dose (MPED)

controlled area MPED is equal to

1000 uSv/week or 1 mSv/ week

calculating barrier shielding requirements

it is the product of mA-minutes x U x T must be determined

-planner must know whether the area beyound the barrier is controlled or uncontrolled

NCRP states the calculation is now described as determining the

thickness of a barrier sufficient to reduce the air kerma in a full or partially occupied area to a value that is less than or at most equal to the ration P/T

calculation is complicated but takes into account

-xray transmission

-air kerma values

-distance from xray source to representative locations

-number of pt examined in room per week

-use factor and occupancy factor

-uncontrolled vs uncontrolled area

-kVp is important for determining air kerma measurements

what to know about primary barrier calculation

united states shielding is in fractions of lead

1/16th for primary (1.6 mm)

1/32 for secondary (.8mm)

secondary barrier calculation

intercept both scatter and leakage radiation

scatter and leakage emerge in

all directions, so use factor is always 1

-intensity of radiation scattered at a 90 degrees at 1 meter from its source is reduced by a factor of 1000 relative to the primary radiation

leakage

regulatory standards mandates that maximum permissible leakage exposure rate at 1 meter from the target of xray tube in all directions can not exceed 100 mR/hr or .88 mGya/hr when it is operated continuously at its maximal permitted kVp and mA combinations