Radiation Protection (Lecture 2)

If no barrier, how should the operator stand?

Atleast 6 feet away, 90-135 degrees to the beam

What do dosimeters do?

Monitor operators exposure

What are the requirements for the lead apron?

Protects reproductive/blood tissues

• Minimum 0.25 mm thick

• Used for all procedures

What does the thyroid collar protect and when is it used?

Protects thyroid from scatter

• used for all intraoral exposures

What does ALARA mean?

As Low As Reasonably Achievable

• minimize all exposures

Why is the paralleling technique preferred?

Most accurate images for less patient exposure

• Tube/teeth/receptor parallel

How should exposure factor (kVp, mA, time) be chosen?

Lowest possible settings

What does collimation do?

Restricts beam size/shape (circular or rectangular) with lead diaphragm in the PID

Which PID best and why?

Long PID (16in) due to less divergence, lower dose, and better quality

How does rectangular PID compare to round?

Reduces exposure 60-70%

• But round has fewer retakes

Why are film holders important?

• Keep receptor stable

• Prevent bending/movement

• Reduce exposure

What is the maximum diameter allowed at the patient’s/ skin?

(Less than) <2.75 inches

What does aluminum filtration remove?

Low-energy, long wavelengths

How much filtration is required?

• more than 2.55 mm for anything above 70kVp

• at least 1.55 mm for anything below 70kVp

What is the fastest film and why it recommended?

F-speed film

• 20% less exposure than E-speed

What reduces dose even further than fast film?

Digital sensors