Lecture 1

What happens during ionization?

X-ray photon hits atom → ejects electron → creates ion pair → atom unstable → tissue damage

How are free radicals formed?

From ionized water molecules

Why are free radicals dangerous?

They are unstable + highly reactive

• form toxins like hydrogen peroxide

What is the charge of an electron?

negative

What is the charge of a proton?

Positive

Which particle can be knocked out during ionization?

Electron

What is the direct theory of radiation injury?

Photons hits DNA directly, causing damage

What is the indirect theory of radiation injury?

Photons ionizes water → free radicals form → cause cell damage Wh

Which radiation injury theory is more common?

Indirect theory

What toxic byproduct forms when water is disrupted?

Hydrogen peroxide

What is the latent period?

Time between exposure and symptoms

What happens during the period of injury?

Cell death or changes in function

What is the recovery period?

Some repair occurs, not always complete

What are cumulative effects?

Repeated low-level exposures add up over time

How does total dose affect injury?

Higher dose = more damage

How does dose rate affect injury?

Faster rate = more damage

Which cells are most sensitive to radiation?

Rapidly diving cells

• lymphocytes

• Bone marrow

• Reproductive

Are children more or less sensitive to radiation than adults?

More sensitive

Give examples of short-term radiation effects

• Nausea

• Diarrhea

• Hair loss

Give examples of long-term radiation effects

• Cancer

• Genetic defects

• Abnormalities

What are somatic effects?

Effects seen in the irradiated person

What are genetic effects?

Damage to reproductive cells, passed to offspring

Name some radiosensitive tissues

• Lymphoid tissue

• Bone marrow

• Reproductive cells lymphocytes

• Intestines

• Skin

Name some radioresistant tissues

• Muscle

• Nerve

• Mature bone

• Cartilage

List 4 critical organs exposed in dental radiology

• Thyroid gland

• Bone marrow

• Skin

• Lens of eye

What units measure exposure?

Roentgen (R) and Coulomb (C/kg)

What units measure absorbed dose?

Rad and Gray (Gy)

What units measure dose equivalent?

rem and Sievert (Sv)

List types of natural/background radiation

• Cosmic

• Terrestrial

• Internal

• Radon gas

What is the #1 source of natural radiation exposure?

Radon gas

What is the largest source of man-made radiation?

Medical radiation

What is the average U.S annual radiation exposure?

6.2mSV/year

What is the risk of fatal cancel from dental X-rays?

About 3 in 1 million

Which critical organs are at risk if not protected?

Thyroid, bone marrow, skin , lens of eye

What does ALARA stand for?

As Low As Reasonably Achievable

What does ALARA mean for dental radiology?

Always minimize patient and operator exposure

Why do we take dental X-rays despite radiation risk?

Diagnostic benefit outweighs the small radiation risk

What is the 6-foot rule ?

Stand at least 6 feet away from the X-ray beam

What is the 90-135 degree rule?

Stand at right angle to beam, not in direct line

What protects the operator from exposure?

Leaded wall/barrier

What do dosimeter badges measure?

Operator’s radiation exposure

What should an operator never do during exposure?

Never hold film or tube head

How thick must the lead apron be?

At least 0.25 mm lead

What must always be used with a lead apron?

Thyroid collar

What items should be removed before taking X-rays?

Glasses, dentures, chewing gum

How is the treatment area prepared for radiographs?

Disinfect and cover surfaces with barriers

What must be labeled before taking X-rays?

• Disposable cup with patient’s name (and yours for dexter)

• 2 mounts

• 1 coin envelope

Where are unexposed film and holders arranged?

On cart, on tray cover

Where is the empty cup placed?

Upper left corner of cart

How are exposed films transported?

In labeled cup, carried with clean hands only

What are two cups used for inside the daylight loader?

• Clean cup (clean films)

• Contaminated cup (trash/contaminated wrappers)

How should films be handled before processing?

• By edges only

• Never with contaminated gloves