Dose limits and protective barriers/apparel

Cumulative effective dose limit

Age in persons years times 10 mSv (1 rem)

Annual occupational effective dose

50 mSv

General public effective dose limit CONTINOUS

1 mSv

Occupational dose limits to the hands and skin

500 mSv

General public effective dose limit Infrequant

5 mSv

Monthly EqD to embryo

0.5 mSv

Annual effective dose to students older than 18

50 mSv

Occupational dose limits to the eyes

150 mSv

Scattered x-ray intensity at 90 a degree angle to the primary beam

At 1 meter 1/1000 0.001 1/10%

Lead apron lead content

.25mm minimum .5mm standard

EqD during entire pregnancy

5 mSv

Maternity apron

0.5mm lead eq and 1mm panel transverse the width

Primary protective barriers are located

Perpendicular to the undeflected line of travel of the x-ray beam

Primary protective barrier when beam is 130 kvp

1.6mm (1/16 in) lead at 7 feet tall

Secondary protective barrier located

Where radiation had been deflected from the primary beam. Protects against leakage and scatter. Any wall not hit by primary beam.

Secondary barrier should overlap primary barrier by

1.27 cm (1/2 in)

Secondary barrier thickness

0.8 mm (1/32 in) lead

Control booth barrier

Protects against secondary radiation. 7ft high

Doors to x-ray rooms

0.8mm (1/32 in) lead

Control booth window

1.5 mm lead eq

Clear overhead barrier - cath lab

0.5 mm lead eq

Apron when peak energy is 100 kvp

0.25 mm lead eq 0.5mm recommended

Thyroid shield

0.5mm lead eq

Eyeglasses

0.35mm lead eq

Gloves

0.25mm lead eq

Fluoro curtain

0.25 mm lead eq to intercept scatter from table top

Bucky slot

0.2 mm lead eq Protects the radiologist at the gonad level

Exposure switch cord length for mobile

2mm (6 feet)

Apron for C-arm use

0.5mm lead eq

Thyroid shield for C-arm use

0.5mm lead eq

Max entrance exposure rate for regular fluoro

10 cGy/min (100 mGy)

Max entrance exposure rate for high level fluoro

20-40 cGy/min

Workload (W) defined as

Radiation output weighted time that the unit is actually delivering radiation during the week. Used to determine barrier shielding requirements. Measured in mAs per week.

Use factor

Portion of beam on time that the x-ray is directed at the primary barrier. Full use=1

Occupancy factor

Zero occupancy - other side of wall always empty

Full occupancy - Other side of wall always has people

Controlled area

Region adjacent to a wall of an x-ray room is used only by occupationally exposed personnel. 1000 uSv (1 mSv)

Uncontrolled area

Area frequented by general public 20uSv max

Three ways to specify radiation received by a patient

1. ESE

2. Bone marrow dose

3. Gonadal

Genetically significant dose

0.20 mSv

Fetal dose greater than .4 Sv

Mental retardation

Greatest risk for mental retardation

8-15 weeks

Organogenesis

10 days to 12 weeks after conception

Air Kerma

Approximate skin dose where x-ray entered a patient.

Radiation depositing energy at a specific point.

Air kerma

GrayT multiplied by a radiation weighing factor equals

Air kerma

Unit of measurement that is determined by measuring ions produced in air

Air kerma