module 2: radiation biology and safety

insulating oil

oil contained within tubehead; absorbs heat, prevents overheating

What does milliamperage (mA) control?

The quantity of X-rays produced.
↑ mA = more X-rays = darker image
↓ mA = fewer X-rays = lighter image

What does exposure time control?

How long X-rays are produced, affecting X-ray quantity.

↑ time = more X-rays = darker image
↓ time = fewer X-rays = lighter image

What is the relationship between mA and exposure time?

They can be adjusted inversely to maintain the same mAs/exposure.

What does kVp control?

The quality/energy and penetrating power of the X-ray beam. It also strongly affects image contrast.

What happens when kVp increases?

↑ kVp → ↑ penetration → shorter wavelength → LOW contrast → more shades of gray

What happens when kVp decreases?

↓ kVp → ↓ penetration → longer wavelength → HIGH contrast → more black and white

How does kVp affect contrast?

High kVp → LOW contrast → many shades of gray

Low kVp → HIGH contrast → fewer shades of gray / more black & white

mA

QUANTITY of X-rays produced.

kVP

QUALITY/ENERGY and penetrating power of X-rays.

What happens to wavelength when kVp increases?

kVp ↑ → wavelength ↓ → penetration ↑

What happens to wavelength when kVp increases?

Primary radiation is the original X-ray beam that comes directly from the X-ray tube.

secondary radiation

Radiation produced when the primary X-ray beam interacts with matter, such as the patient's tissues. It has less energy and penetrating ability than the primary beam.

scatter radiation

When the primary X-ray beam interacts with the patient, some radiation is deflected away from its original direction. so like it gets on the DA or Dr

What happens with no interaction?

The X-ray photon passes through matter without interacting.

what happens during the photoelectric effect?

The X-ray photon is completely absorbed and ejects an inner-shell electron, causing ionization.

What happens during coherent scatter?

The X-ray photon changes direction without ejecting an electron. It is non-ionizing.

What happens during Compton scatter?

An X-ray photon ejects an outer-shell electron, loses energy, and changes direction. It causes ionization and produces scatter radiation.

What happens when many X-rays reach the image receptor?

The area appears radiolucent (dark).

What happens when a dense object absorbs or blocks X-rays?

Fewer X-rays reach the receptor, so the object appears radiopaque (white/light).

What are the three common types of dental X-ray image receptors?

Film, digital sensors, and phosphor plates.

What do Roentgen and C/kg measure?

Radiation exposure in AIR.

What do RAD and Gray measure?

The absorbed dose, meaning the amount of radiation energy absorbed by tissue. 1 Gy = 100 RAD

What do REM and Sievert measure?

Equivalent dose, which accounts for the biological effect of radiation.

what is dose rate?

The amount of radiation received per unit of time. A high dose delivered quickly generally causes more biological damage.

Which cells are most radiosensitive?

Cells that are rapidly dividing, immature, and less specialized.

How does total radiation dose affect biological damage?

As total dose increases, the risk of biological damage increases.

How does the area exposed affect radiation damage?

The larger the area of the body exposed, the greater the potential biological effect.

Why are children more radiosensitive?

Their tissues contain more rapidly dividing and developing cells.

Are all organs equally sensitive to radiation?

No. Some tissues and organs are more radiosensitive than others. like bone marrow and reproductive organs

What is direct radiation damage?

Radiation directly hits a critical cell structure, such as DNA, causing damage.

What is indirect radiation damage?

Radiation ionizes water in the cell, producing free radicals that can damage the cell.

What does radiation hit in indirect damage?

water molecules

What can ionized water produce?

free radicals

what are somatic cells

All body cells except reproductive cells (sperm and ova).

What is somatic cell damage?

Radiation damage to body cells, such as skin or bone cells

Who is affected by somatic radiation damage?

The person who was exposed.

What factors influence somatic cell damage?

Radiation dose, dose rate, tissue radiosensitivity, and area exposed.

What is the latent period?

The time between radiation exposure and the appearance of the first signs or symptoms.

What is the period of injury?

The period when cellular damage from radiation becomes observable.

What is the recovery period?

The period when the body repairs or replaces damaged cells.

what are genetic cells

Reproductive cells: sperm and ova.

what is genetic radiation damage

Radiation-induced damage or mutation involving reproductive cells, which could potentially affect future generations.

what are gonads

The ovaries and testes.

Who can be affected by genetic cell damage?

Potentially future offspring/generations if a heritable mutation occurs.

Who is affected by somatic cell damage?

The exposed individual.

What does MPD stand for?

Maximum Permissible Dose.

According to this slide, what is the annual MPD for a radiation operator?

0.05 Sv or 5 REM/year.

According to this slide, what is the annual MPD for the general public?

0.005 Sv or 0.5 REM/year.

formula for MAD

MAD = (N − 18) × 5 REM or (N − 18) × 0.05 Sv.

What does MAD stand for?

Maximum accumulated dose.

what does ALARA stand for?

As Low As Reasonably Achievable

what is the purpose of ALARA?

To keep radiation exposure as low as reasonably possible while obtaining necessary diagnostic information.

What should be done with unnecessary radiation exposure?

reduce or eliminate it

What does ALADA stand for?

As Low As Diagnostically Acceptable.

What is the main idea of ALADA?

Use the lowest radiation exposure that still produces a diagnostically acceptable image.

Why should dental X-ray exposure frequency be limited?

To minimize unnecessary ionizing radiation exposure and follow ALARA.

Should every new patient automatically receive a full-mouth series?

No. Radiographs should be based on the patient's individual clinical needs and existing diagnostic images.

What factors help determine how often bitewings are needed?

Age/dentition, caries risk, clinical findings, and previous radiographs.

Who generally needs X-rays more frequently: high-caries-risk or low-caries-risk patients?

High-caries-risk patients.

Who determines which dental radiographs are needed?

The dentist, based on clinical judgment and patient needs.

What is the purpose of collimation?

To limit the size and shape of the X-ray beam.

What is the collimator made of?

Lead.

What type of collimation reduces patient exposure the most?

Rectangular collimation.

What is the maximum diameter of a circular beam at the patient's skin according to the slide?

2.75 inches or 7 cm.

What does filtration remove?

Low-energy, long-wavelength X-rays.

Why remove low-energy X-rays?

They increase patient exposure without helping form the image.

What material is commonly used for added filtration?

aluminum

How much filtration is required at 70 kVp or above according to the slide?

2.5 mm aluminum equivalent.

Below 70 kVp?

1.5 mm aluminum equivalent.

what does PID stand for?

Position-Indicating Device.

What is the main purpose of the PID?

To direct and limit the X-ray beam.

Which is preferred for reducing beam divergence, a longer or shorter PID?

longer PID

What target-to-receptor distance is recommended on this slide?

16 inches

what is shielding?

Using protective barriers to block radiation exposure.

what are examples of shielding?

lead apron and thyroid collar

why are image receptor holders used

to stabilize the receptor and reduce movement and retakes

Which requires less exposure time: digital imaging or conventional film?

digital imaging

how do digital sensors help protect patients?

They require less radiation and shorter exposure times.

What is the purpose of a protective barrier?

To protect the operator from scatter radiation.

What materials can be used as radiation barriers?

lead, concrete, and steel

Where should the operator ideally stand during X-ray exposure?

behind a protective barrier

What does a dosimeter do?

measures radiation exposure

Does a dosimeter protect you from radiation?

No. It measures exposure.

What does a pocket dosimeter measure?

cumulative radiation exposure

Which monitoring device is identified as the most accurate on this slide?

Thermoluminescent dosimeter (TLD).

How long may a TLD be worn according to the slide?

up to 3 months

How far should the operator stand from the radiation source?

at least 6 feet

At what angle should the operator stand from the primary beam?

90°–135°

What happens when you double your distance from the radiation source?

Radiation intensity decreases to ¼.

Should the operator hold the image receptor during exposure?

no

Should the operator hold the tubehead during exposure?

no

What are three ways an operator can protect themselves during exposure?

Leave the room, stand behind a barrier, or maintain proper distance and position.