BOARD REVIEW RAD

Density

The —————- of a radiograph can also be called the darkness. —————- (darkness) is proportional to amperes, kVp, and time. Milliampere-seconds is a combo of milliamperage and time. To maintain similar density, if time is increased, milliamperage must be decreased. And vice versa. —————- is decreased if the targer structure is dense.

kVp

Contrast is dependent on ———. Increased ——— results in many shades of gray (long scale, low contrast). .

Low contrast (long scale, low contrast) many shades of gray. Increase kVp

Is high or low contrast best for detecting bone abnormalities, changes in bone density, and periodontitis progression.?

High contrast (short scale, high contrast) more black and white. Decrease kVp

Is high or low contrast best for detecting caries?

Sharpness

This is the capacity to produce details and distinct outlines.

Penumbra

Blurring at the edges of a structure on a radiograph.

Shorter

Does a longer or shorter distance create less magnification

Horizontal

Overlap is caused by improper ———————— angulation.

Vertical

Elongation and foreshortening are caused by improper ——————— angulation.

Elongation

This error in vertical angulation is caused by underangulation.

Foreshortening

This error in vertical angulation is caused by over angulation.

Bitewing

What image is used to mainly for the diagnosis of interproximal dental caries?

18 (14 PAs and 4 BWs)

How many images are usually in a FMS?

Bisecting technique

The ——————— technique is based on rule of isometry (2 triangles are equal when they share one complete side and have 2 equal angles). Requires ——————— of the angles formed by the film and long axis of the tooth. Primary beam hits 90 degrees to the ——————— line.

Chin

For the mandibular occlusal technique, the head is tilted backwards, negative 55° vertical angulation. Central rays are directed through the:

Tip of the nose

For the maxillary occlusal technique, the occlusal plane is parallel to the floor. With a positive 65° vertical angulation. Central rays are directed through the:

Eyebrows

For the cross-sectional maxillary occlusal technique, the occlusal plane is parallel to the floor. Beams are perpendicular to the receptor and directed between the:

ala-tragus line

For the cross-sectional mandibular occlusal technique, the head is tilted backwards until what line is almost perpendicular to the floor. Beams are perpendicular to the receptor and directed inferior to the chin.

Same Lingual Opposite Buccal

What does the SLOB rule stand for? This shows whether an artifact is lingual or buccal. a rad is a 2D image of a 3D space. Therefore, a BW or a PA only show the anteroposterior location. 2 images are needed, the second image is taken at a different angle. Compare the 2 images and see if the object moves toward the same or opposite direction compared to the change in the tube head position. If the tube head and the object moved in the SAME direction, the object is located LINGUALLY, if the object moved the OPPOSITE direction, the object is located BUCCALLY.

Focal through

The zone in which structures are clearly demonstrated on a panoramic radiograph.

rare earth intensifying screens

the intensifying screen that emits green light and must be used with green sensitive film is termed:

Lateral jaw exposure

This view (type of x ray) evaluates . The posterior portion of the mandible or lateral areas that are too large to capture in PAs.

Water's projection

This image provides images of the maxillary sinus.

Atom

This is the smallest component of an element.

Molecule

When atoms combine together, they form a:

Electrons

An atom consists of a nucleus and orbiting:

Nucleus

This is the core of an atom. Consisting of protons and neutrons. This contains nearly all of the atoms mass. Not to be confused with a ——————— in biology).

positively, (protons and neutrons)

The nucleus is ———————— charged

Electrons

These have a negative charge. Their orbiting shells are 3-D structures around the nucleus that contain ———————s. Shells are designated with capital letters KLMNOPQ. The closer the orbit is to the nucleus, the higher its binding energy. (Stronger bond). K shell interaction has the highest binding energy and is the most useful for medical imaging. To remove an orbital ——————— from its shell, energy equal to or greater than the binding energy of a specific shell is needed.

Roentgen

Who discovered x-rays in 1895?

X-rays

These can be described as powerful, invisible rays capable of penetrating substances.

Radiation

The propagation of energy through space in the form of particles or waves.

Ionization

The process by which an atom gains or loses electrons to become negatively or positively charged atom.

Ion

A charged particle that is either positive or negative

Ion pair

Positive ion (atom missing an electron) and a negative ion (ejected electron).

Ionizing radiation

This is ant type of radiation that is high in energy and is capable of producing ions. Particulate and electromagnetic radiation are formed because of this.

Particulate radiation

This type of radiation involves particles that have mass and travel in straight lines at high speeds. May have a charge, except for neutrons. This type of radiation includes neutrons, protons, electrons, Beta particles, and Gamma particles. Has mass.

Electromagnetic radiation

This type of radiation is electric and magnetic fields of energy that move through space in a wave-like motion. Includes radio waves, microwaves, visible light, UV rays, X rays, and gamma rays (from low to high energy). Only high energy waves have ionizing capacity. X rays are powerful electromagnetic energy capable of penetrating substances. Travels at the speed of light and has no mass or charge.

Wavelength

Distance between the peaks of crests of one wave to another. Measured in horizontal length. Determines the energy and penetrating power of the radiation.

Longer

If a wavelength is (shorter or longer), it has a lower energy (and frequency). Less ability to penetrate objects.

X rays

These are invisible, travel at the speed of light, travel in waves, have a high frequency and short wavelength. Can penetrate objects and can cause changes in cells.

Electricity

This is the power source of x-ray machines. With direct current (DC), electrons flow in one direction. With an alternating current (AC), electrons flow in 2 directions.

Circuit

This is the route the electric current takes. A high-voltage circuit uses 65,000 to 100,000 volts, providing high energy to produce x-rays.

Transformer

Mechanism used in an electrical circuit to increase or decrease voltage. It may be a step-up, step-down, or auto transformer type.

Control panel

This is a part of the x ray machine. Displays the on-off switches and milliamperage/time/kilovoltage settings.

Ampere (amperage)

This is the number of electrons. An increase in —————- increases the number of electrons produced in the x-ray tube. Dental machines operate with 5-8 milli———————, most commonly preset at 7 milli———————. This controls the temperature of the cathode filament.

Volt

force that moves electrons from the cathode to the anode.

Kilovoltage peak (kVp)

Peak voltage of an alternating current. This determines the speed at which the electron is propelled from the cathode. This also determines the penetrating power of the X-ray beam, this is called quality.

Lead gas vacuum housing

This part of the X-ray tube contains 2 type of electrodes - the cathode and the anode

Cathode

The negative electrode in the x-ray tube. Controlled by milliamperage (mA) settings.

Tungsten filament (also called filament)

This component of the x ray tube emits electrons when heated. An electron cloud forms around it.

Molybdenum/focusing cup

focuses the direction of electrons towards the anode.

Anode (positive) electrode

This electrode in the x ray tube is controlled by the kVp settings.

Tungsten target

This is the spot in the x ray tube where the electrons hit to produce x rays.

Focal spot (target)

This is the small area on the tungsten target on the anode toward which the electrons from the focusing cup of the cathode are directed. X rays originate at the ————— ————.

Copper stem

What part of the x ray tube? Dissipates excessive heat. X ray production (1%) and heat (99%).

Tube head

What part of the x ray tube? Protective metal covering that contains the x ray tube, high/low-voltage transformers, and insulating oil (oil helps dissipate the heat).

Position indicating device (PID)

What part of the x ray tube? Attaches to the tube head and directs the x ray beams to the object and film. Can be in the shape of a cylinder or rectangle (reduces exposure).

Thermionic emission

At the cathode, when power switch is activated, the (tungsten) filament produces electrons. An electron cloud forms around the filament. This process is called:

Primary radiation

After the tungsten filament creates the electron cloud, the exposure button is pressed. Electrons are propelled at a high speed towards the anode’s focal spot within the tungsten target. Electrons hit the target at the anode and transform kinetic energy into x rays (heat is formed but is dissipated through the copper stem). Photons leave the x ray tube as what? (Photons have not interacted with the patients body or any other objects). X rays are formed at the tube, mainly by 2 mechanisms: braking radiation and characteristic radiation

Photon

A bundle of energy.

Braking (Bremsstrahlung) radiation

This is a major source of x rays produced in dentistry.(70%). Results when high-energy electrons come close to the nuclei of the tungsten atoms. Electrons move toward the nucleus (since they have opposite charges) and then slow down (this is why this type of radiation has gotten this name). When the electrons brake, energy is released (photons).

Characteristic radiation

This type of radiation is formed when electrons from the cathode dislodge electrons from the inner orbital K/L shell of the tungsten atoms. When electrons of the inner shells are dislodged, electrons from other orbits fill the empty space left by the ejected electron. During this process, energy is produced. Not as significant a source of x rays as braking radiation.

Secondary radiation

created when the primary beam interacts with matter, less penetrating.

Scatter radiation

A form of secondary radiation; result of deflection of original path by interaction with matter; considered detrimental to patient and provider. Usually has a longer wavelength than primary radiation. Can cause fogging of a radiographic image. According to how the x rays interact with matter, different types of —————ing can occur, including Compton ———————, photoelectric effect, and coherent ———————. It is also possible that the x rays will not interact with any cells in their path.

Common scatter

This is the most common type of scatter radiation. Responsible for most interactions with the matter in dental x rays (around 60%). Ionization occurs. A photon interacts with the outer shell electron of a matter. Photon loses energy but continues to travel, and the electron is ejected. It is always easier to hit the outer shells than the inner ones because the outer shell is bigger and contains more electrons.

Photoelectric effect

This is a less common form of scatter radiation. Responsible for about 30% of all interactions with matter in dental x rays. A photon interacts with an inner shell electron. The photon is absorbed, and the electron is ejected. Ionization occurs.

Coherent scatter

This type of scatter radiation is responsible for about 8% of all interactions with the matter in dental x-rays. Photons interact with an outer shell electron but matter is not altered. Photons continue to travel with no loss of energy. Ionization does not occur.

Standard (traditional system) and system international (SI)

What are the 2 systems used to measure the amount of radiation?

100 rem

how many rem are in 1 Sv (Sievert)?

100 rad

1 Gy (Gray) is the SI equivalent of how many rads?

Roentgen

Exposure is measured by Coulomb (C/Kg) in the SI system. What is the measurement of exposure when using the standard (traditional) system.

Direct theory

Radiation damages a cell’s protein, lipid, carbohydrate, and DNA molecule and causes cell death. This accounts for 1/3 of radiation biological damage. What is this theory of living tissue damage by. Radiation?

Indirect theory

Radiation interacts with the cells water content (H20), and produces free radicals. Free radicals are mostly H and OH and are highly unstable. They interact with each other to produce toxins such as hydrogen peroxide (H2O2). This accounts for approximately 2/3 of radiation induced biological damage. This is proportional to the body water content (the body is composed of 60-80% water). What is this theory of living tissue damage by radiation?

Ionizing

All ——————— radiation is harmful and produces biological changes in living tissues.

Short term effects

These effects of radiation may occur in minutes, hours, or weeks following following exposure. This type of effect of radiation is not present in dentistry. High doses of radiation to the whole body may result in nausea, diarrhea, fever, hair loss, and death.

Long term effects

These effects of radiation may occur months, years, or decades following exposure. Low doses of radiation received over a long period of time may result in cancers. Exposure of the entire body results in more severe biological effects.

Somatic effect

This is the effect of radiation that involves damage/injury to the person being affected. Occurs in a nonlinear, threshold dose-response in which higher doses produce progressively more severe damage.

Genetic effect

This effect of radiation involves damage/injury to the future generation. Occurs in a linear, non-threshold dose response. This means that even small amounts have the potential to produce some mutations.

Stochastic effect

———————— effect means that the probability of the occurrence increases with dose, but the severity is not dependent on the dose (e.g., cancer). ———————— effects are “all or none”, a person either has or does not have the condition.

Non-stochastic effect

——— ———————— is also called deterministic effect. Severity of the damage is dependent on the dose (e.g., hair loss, decreased fertility).

DNA and chromosomes

This is the most sensitive part of the cell to radiation:

A cross country airplane flight

Dental radiation exposure is similar to doses received during:

Aluminum discs

Absorbent materials, usually ——————— ———— are placed in the path of the x rays to filter our longer, non productive wave lengths. This lowers the low energy (soft) x ray photons which would otherwise not contribute to the image quality but would add to patient dose and scatter. Inherent filtrations are built in to the machine (glass tube, oil, and 0.5-2mm of ———————— ————). Added filtration depends on the kVp used (at or below 70 kVp=1.5mm thickness of ————————, above 70 kVp = 2.5 mm thickness).

Collimation

This is the metal barrier with an opening in the middle that restricts the size and shape of the beam. Reduces film fog, improves image quality, and restricts patient exposure (primary and scatter). Rectangular ———————— exposes tissue 60% less than a round one.

8 and 16

The standard lengths for PIDs are — and —— inches. Long PIDs produce more parallel rays and reduce radiation exposure.

F-speed film (F=fastest, E=middle, D=slowest)

According to the FDA, — speed film produces a 60% reduction in exposure. The film speeds are: F,E, and D. Digital receptors require 50-90% less radiation exposure. Faster film has larger silver halide crystals, which may lower the quality of the image.

Intensifying screens

These are plastic sheets coated with fluorescent material called phosphors. Phosphors convert photon energy into visible light photons.

As low as reasonably possible

What does ALARA stand for?

Maximum permissible dose

What does MPD stand for?

5 rem/year (5000 mem) or 50mSv/year

What is the MPD for an occupational person?

0.1 rem/year or 1 mSv/year

What is the MPD for a non-occupational person?

Workers age multiplied by 10 mSv

an individual's cumulative occupational effective dose should not exceed what?

0.5 mSv/month

Pregnant patients should not exceed —.— mSv/month during pregnancy months:

Dark areas

Radiolucencies are the (light or dark) areas in a rad?

Light

Radiopacities are the (light or dark) areas in a rad?

Half value layer

Thickness of aluminum filters that reduces the intensity of the beam by half. The filters remove longer, less penetrating waves.

Inverse square law

This law states that radiation intensity is inversely proportional to the square of the distance from the radiation source. Step 1: note how much shorter or longer the distance is. Step 2: square the number. Invert the number only if the source is farther. Ex: 2 times farther = 2. 2 squared =4. The distance is FARTHER so you invert the number. This means that the beam is 1/4th as intense as the original beam.