Projection X-ray

Question 1

List a number of engineering controls designed to restrict radiation exposure within a diagnostic facility

Answer 1

Wall, floor, ceiling, doors materials
Fixed Screens
Emergency Stops
Warning signs / Lights
Dead man’s handle
AEC device
Tube design (shielding)

Question 2

What are local rules?

Answer 2

Summary of key working instructions that are required for all Radiation Controlled Areas with the intention on restricting routine exposures to ionising radiation and to control the exposure in the event of a radiation incident.

Question 3

What must the local rules contain?

Answer 3

Essential:
Description of Designate Area
Arrangements for Restricting Access
Summary of Work instructions (but not comprehensive set of SOPs)
Dose Investigation Levels
Continency Plans
Names of RPSs

Optional:
Persons with responsibilities: e.g. Employer, Managers, RPA (MPE), Equipment Engineers / Estates Maintenance
Maintenance/Testing of Engineering Controls and Safety Features
Environmental Monitoring
Contamination Monitoring (radioisotope)
Testing of Monitoring Equipment (radioisotope)
Personal Dosimetry Arrangements
Pregnant or Breast Feeding Staff

Question 4

Who write the local rules?

Answer 4

RPS and Local Management aided by RPA. Also involve other relevant staff groups (for example surgeons within theatres).
Rules formulated on the back of a prior risk assessment

Question 5

Who should read the local rules?

Answer 5

IRR ACOP: ‘available to all employees and other people directly involved or likely to be affected at or near the area concerned’.

Summary displayed on wall

Signed record sheet as evidence

Question 6

List some forms of PPE you may find in radiology

Answer 6

Lead aprons
Thyroid Shield
Portable screens
Leaded glasses
Leaded gloves
Radpads
Personal monitoring

Question 7

Is it better to wear a thicker lead apron (from 0.25-0.5mmPb) or wear a thyroid shield? How would you calculate this?

Answer 7

It is usually more effective to wear a thyroid shield but this depends on kVp

Assume a uniform irradiation (big assumption!)
Calculate the effective dose with no shielding
Calculate the shielded (0.25 mmPb) organ doses and then relative effective doses with and without a thryoid shield
Repeat for a 0.5 mmPb apron and compare results.

Question 8

What do we call the effect of distance on radiation dose-rate?
Give an example of a staff group outside of medical physics that needs to be most aware of this.

Answer 8

Inverse square law.

Examples:
Interventional radiologists
Cardiologists
Scrubbed nurses