Occupational radiation safety in Radiological imaging

Dr Roshan S Livingstone

Associate Professor

Department of Radiology

Christian Medical College, Vellore

Concerns

• Increased use of man-made radiation globally

• Increase in the purchase of radiation based high-end modalities

• Lack of orientation/training of staff – technique and radiation safety

• Lack of awareness among the staff and public

Occupational radiation workers order of dose severity

• Cardiology cath lab

• Radiology cath lab

• Endovascular surgery – operation theatre

• Operation theatre procedures (ortho, uro..)

• Barium and ERCP (Radiology and Gastro)

• Conventional Radiography (Radiology)

• Dental

• Lithotripsy

• Mobile radiography

• Dual energy xray absorptiometry (DEXA)

• CT

OUTLINE

• Factors influencing radiation dose to staff in Radiology

• Principles of radiation safety

• Monitoring radiation dose to staff and radiation safety accessories

• Conclusion

Early x-ray imaging

• Discovery of x-rays by Wilhelm C Roentgen in 1895

• Medical imaging specialty to visualize internal anatomy of a human body without surgical exploration.

• Early imaging modalities

• Fluorescent screens

• Film-screen cassettes

• Image intensifier

• CT scanner

Early days

Factors influencing radiation dose to staff from x-ray modalities

Scatter radiation

• When x-rays enter through the body surface most of the energy is absorbed by tissues while some amount is scattered from the body surface (eg., patient).

• Staff are are exposed to these scatter (secondary) radiations.

Most of a operator’s occupational exposure comes from scatter radiation Using radiation safety accessories will effectively lower operator’s occupational exposure.

Loss of hair among interventionalists

• Duration of fluoroscopic screening – reduce wherever possible

Courtesy: Wagner, Biomed Imaging Interv J 2007

Wiper et al., Heart, 91 (11); 1432, 2005

Loss of hair among

interventionalists from cath labs

Ill-effects

Cataract among interventionalists

• Eye lens opacities and cataracts among interventionalists working in catheterization labs for several years.

• Cumulative median values of lens doses were estimated at 6.0 Sv for cardiologists and 1.5 Sv for associated medical personnel.

Vano E et al., Radiat Res.Oct;174(4):490-5, 2010

Ill-effects

Work practices

• Tube Angulation

• Steep angulations – LAO 45o CAU 35o

• Demands more radiation for imaging

• Increases staff dose

• Increases patient dose

Less radiation dose More radiation dose

Factors influencing radiation dose to staff

Work practices..

X-ray

tube

X-ray

tube

Image

detector

The distance between

patient and image

detector should be

minimum and

maximum between

patient and the source.

Image

detector

Low dose

High dose

Factors influencing radiation dose to staff

Work practices..

• Collimation

• Radiation beam should be collimated along the region of interest to reduce scatter and improve image quality

Collimated beam

Less scatter

More scatter

Factors influencing radiation dose to staff

Work practices…

• Excessive use of image magnification increases

radiation doses

• Use image magnification modes judiciously

Normal view Magnified view

Factors influencing radiation dose to staff

Work practices..

• Use of radiation safety accessories is mandatory in all x-ray rooms

• Lead rubber aprons / lead free aprons

• Lead goggles

• Thyroid shield

• Ceiling mounted lead glass

• Lead drapes

• Shield barrier

Factors influencing radiation dose to staff

Basic principles of radiation protection

Time

• Radiation dose is directly proportional to time of x-ray exposure.

• Examination time should be minimum

• Lesser the time spent lesser is the dose.

• Increasing the screening time will increase the radiation dose • Do not depress the footswitch continually for long periods; • Use last image hold options • Use pulsed fluoroscopy modes

• Radiation dose is inversely proportional to the square of the distance.

• Increasing the distance reduces the dose effectively.

• Do not put your arm under the primary beam

Source

64 units of

intensity

16 units of

intensity

4 units of

intensity

2 units of

intensity

Distance

• Shielding is warranted for all staff working in radiation areas.

• Use of lead aprons (0.25-0.5mm), ceiling mounted lead barriers, lead glass goggles, lead drapes.

• Always work behind the barriers .

Shielding

Practice: As Low As Reasonably Achievable principle

Am I protected?

MONITORING STAFF DOSES AND SAFETY ACCESSORIES

Radiation dose monitoring

• Thermo-Luminescent Dosimeters

• Real-time monitoring devices

• Pocket dosimeters

• Area surveillances using survey meters

Survey meter Real time monitoring

INSTRUCTION TO USERS - Do’S

• Use TLD card of the valid service period

• Handle the TLD badge with care

• Store the badge in a radiation free place when not in use

• Report any unusual radiation incident to your Supervisor/RSO/

Head of the Institution

• Return the TLD card on or before 5th of every fourth month

(quarter)

Don’ts…

• Don’t wear the TLD badge outside the apron

• Don’t leave the TLD badge in the washing machine or in the vicinity of hot plate, ovens

• Don’t leave the badge in the radiation area when it is not in use

• Don’t share your TLD badge with someone else. Your badge is your own

Ceiling mounted lead glass

There can be a reduction of about 50% of dose savings to the operator with the use of articulated lead screen between the patient and the operator

Safety accessories (fixed/movable) in cath lab

With the use of 0.5 and 1

mm over-couch and

under-couch shielding, it

is possible to reduce the

mean operator radiation

exposure to 14% and 6%,

respectively

Other personal safety accessories

Implementation

Periodic screening of aprons

Awareness among patients and public

Follow low dose protocols for angiography procedures to avoid

complication

(a) 6-8 weeks after multiple coronary angiography and angioplasty procedures.

(b) 16-21 weeks

(c) 18-21 months after the procedures showing tissue necrosis .

(d) Close-up photograph of the lesion shown in (c).

(e) Photograph after skin grafting.

(d) (e)

(a) (c) (b)

(Photographs courtesy of T. Shope & ICRP).

Radiation Dose in MDCT

Y Imanishi et al. Eur Radiol (2005) 15:41-46

Patient relatives waiting inside the x-ray rooms should be avoided

50 mR/hr

CONCLUSION

• Use radiation safety accessories when required.

• Use personal monitoring devices

• Follow the basic principles of radiation safety

• Follow radiation dose reduction techniques

• Radiation safety awareness and training program

For safe practice of radiation in health care

ALARA is still “WAY FORWARD”

Thank You