RHS Exam Study Material

True or False the skin tissues of the patient being radiographed absorb some x-rays

true

Somatic cells

cells found in the body except the reproductive cells (e.g. liver cells, kidney cells, and brain cells)

Which of the following are NOT somatic cells:

• Brain Cells

• Kidney Cells

• Reproductive Cells

• Liver Cells

reproductive cells

Radiation monitoring badge

a device that can measure the amount of radiation that reaches the body of the radiographer

What is the direct result when an image receptor is exposed with a high milliamperage or mA setting?

high density

What is the correct way for a dental assistant to wear a dosimeter?

only when he/she is at the dental office

According to the National Council on Radiation Protection and Measurements, what is the maximum permissible dose of radiation that a dental auxiliary can receive in 1 year?

5 rems

Using the proper what assists in controlling the amount of radiation emitted to the patient?

exposure factors

Soft Waves

• x-rays with longer wavelengths

• have less penetrating power

Hard Waves

• x-rays with shorter wavelengths

• move fast

• greater penetrating power than long wavelengths

When the Kv or kilovoltage in the tubehead is increased what occurs?

the electrons move from the cathode to the anode at a greater speed (this causes the resulting image to have a lower contrast as the x-rays are able to penetrate more objects in the oral cavity)

What does the kilovolt setting in the dental tubehead control?

how fast the electrons and resulting x-rays travel

Cathode

negative side of tubehead

Anode

positive side of tubehead

The amount of radiation absorbed per gram of tissue is referred to as a ..

rad.

What does “rad” stand for and its definition?

radiation absorbed dose

defined as amount of radiation that is absorbed by the tissue following an exposure

What does Rem stand for?

roentgen equivalent man

measures the biological effect radiation may have on a patient

What does a Roentgen measure?

the quantity of radiation that produces an electrical charge in the air

Respondeat Superior

the dentist accepts responsibility for the actions of other professionals

Maximum Permissible Dose

• MPD

• recommendation of the NCRP

• max. dose of radiation a person is permitted to receive from artificial causes

• higher for those occupationally exposed

Areas of the body to avoid during dental radiography

• gonads

• reproductive organs

• bone marrow

• thyroid gland

• eyes

• unnecessary areas of skin

Greatest biological risks from dental radiation exposure

possible development of two types of malignancies

• leukemia

• thyroid cancer

The photoelectric effect

x-rays can be taken into matter and tissues when the two interact

Electromagnetic Radiation

energy traveling in space while generating electric and magnetic force fields

• Gamma Rays: discharged from disintegrating radioactive nuclei

• X-rays: emitted outside the nucleus without mass or electrical charge (can travel through tissue further other forms of radiation without focal localization making them important for forms of diagnostic radiology)

Transformers

• electromagnetic prices of equipment

• step the voltage potential difference up or down in an efficient manner

• consist of iron core surrounded by two different loops of wire at either end

• as current passes through the core and the first primary circuit wire a magnetic field is shifting

X-ray Generators Components

• Control Panel: contains all controls for parameters (exposure time, current selection/mA, potential difference/kVp, x-ray emission light)

• Tubehead Assembly: consists of the x-ray tube and transformers (all of the tubehead assembly/parts are submerged in oil to avoid heat.

Characteristic Radiation

• generated when a high-energy electron from the cathode ionizes or removes an electron from an inner orbit of the target

Bremsstrahlung Radiation

• dominant type of x-ray elicited by dental x-ray equipment

• represents photons of energy emitted as a result of deceleration of the high-speed electrons at the tungsten anode target

Generation of Electrons

• electrons are generated in the tungsten filament of the cathode of the x-ray tube

• when the filament is heated thermal energy is transmitted to the tungsten and the electrons in its outer orbital shells are stripped off to form a cluster of electrons

• known as thermionic emission

Increased (too much/excessive) vertical angulation

• for shortening

• blunted/short/wide teeth

Central area of the anode

called the focal spot