Radiation Physics Quiz

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Questions and Answers

Which restorative material is described as completely radiopaque?

Porcelain restorations

Gold restorations (correct)

Composite restorations

Stainless steel crowns

Which restorative material is typically radiolucent to radiopaque?

Composite restorations (correct)

Porcelain-fused-to-metal crowns

Amalgam

Endodontic materials

What is the radiographic appearance of stainless steel and chrome crowns?

Radiolucent

Radiopaque, but less dense than amalgam (correct)

Slightly radiopaque

Completely radiopaque

Which material is described as slightly radiopaque?

Porcelain restorations Signup and view all the answers

Which of the following statements accurately describes post and core restorations?

The core resembles the prepped portion of a tooth. Signup and view all the answers

What is the primary benefit of using intensifying screens in extraoral radiography?

They reduce the amount of radiation the patient receives. Signup and view all the answers

What is the effective distance a dental radiographer should maintain from the x-ray tubehead?

At least 6 feet. Signup and view all the answers

Which positioning angle is recommended for the dental radiographer relative to the x-ray beam?

90-135 degrees. Signup and view all the answers

What does the Maximum Permissible Dose (MPD) for occupational exposure represent?

The maximum dose allowed for a specific time period. Signup and view all the answers

How does the size of the focal spot influence radiographic sharpness?

A smaller focal spot improves sharpness. Signup and view all the answers

What effect does an increase in target-to-film distance have on image magnification?

It decreases the magnification. Signup and view all the answers

What is the goal of the ALARA principle in radiography?

To keep radiation exposure as low as reasonably achievable. Signup and view all the answers

Which of the following must be true to minimize distortion in a radiographic image?

The object and film must be positioned parallel to each other. Signup and view all the answers

What effect does using concentrated developer on film have?

Leads to overdeveloped film appearance Signup and view all the answers

What is the recommended distance for a low wattage bulb used for safelighting in a darkroom?

4 feet Signup and view all the answers

What is a common cause of yellow-brown stains on the film?

Inadequate rinsing Signup and view all the answers

Which imaging error is caused by excessive time in the developer?

Overdeveloped film Signup and view all the answers

What does the presence of static electricity on film typically appear as?

Black lines Signup and view all the answers

What causes film to appear fogged due to a lack of contrast?

Improper safelighting conditions Signup and view all the answers

What appears on the film when the central ray is not in the center?

Cone-cut Signup and view all the answers

What is a likely result of a film being placed backwards in the mouth during exposure?

Herringbone or tire track pattern Signup and view all the answers

What type of processing error can result in elongated roots on teeth images?

Too little vertical angulation Signup and view all the answers

What type of error is identified by dark spots appearing on the film?

Developer spots Signup and view all the answers

What unit is used to measure exposure in air?

Roentgen Signup and view all the answers

What is the minimum aluminum filtration required for dental x-ray machines operating above 70 kVp?

2.5 mm Signup and view all the answers

Which of the following best describes collimation in radiation protection?

Shapes the x-ray beam into a more restricted area Signup and view all the answers

What percentage of scatter radiation does a lead apron typically absorb?

90% Signup and view all the answers

What is the lead equivalent typically used for a lead apron?

0.25 mm Signup and view all the answers

Which film type is considered the fastest and requires the least radiation exposure?

F-speed film Signup and view all the answers

What does the term 'Position Indicating Device' (PID) refer to in radiation protection?

A cone that directs and limits the x-ray beam Signup and view all the answers

What is the primary benefit of using fast film in radiation exposure?

Reduces the amount of radiation needed Signup and view all the answers

What is the result of placing the Frankfort plane too high during a panoramic radiograph?

A radiopaque cone-shaped artifact obscuring the mandible Signup and view all the answers

Which air space is depicted as a horizontal radiolucent band on panoramic radiographs?

Palatoglossal Air Space Signup and view all the answers

How does the appearance of the anterior teeth change if they are positioned anterior to the focal trough?

They appear skinny and out of focus Signup and view all the answers

What does the midsagittal plane do in a panoramic radiograph?

Divides the body into right and left sides Signup and view all the answers

Which error occurs when the cervical spine is positioned incorrectly during a radiograph?

Radiopacity of the cervical spine Signup and view all the answers

What is the effect of placing the Frankfort plane down during a radiograph procedure?

Condyles may not be visible Signup and view all the answers

What causes ghost images on a panoramic radiograph?

Presence of earrings and eyeglasses Signup and view all the answers

How can an exaggerated smile line appear on a panoramic radiograph?

Chin positioned too high Signup and view all the answers

Where do the maxillary tuberosity and the mental foramen appear, and to which landmark are they associated?

Both associated with the maxilla Signup and view all the answers

What results from a tongue not positioned against the hard palate during a panoramic radiograph?

A dark radiolucent shadow obscuring teeth apices Signup and view all the answers

What role does the anode play in an X-ray tube?

It converts bombarding electrons into X-ray photons. Signup and view all the answers

How does increasing the kilovoltage peak (kVp) affect the X-ray beam?

It results in darker film density due to increased energy of the beam. Signup and view all the answers

Which material is used in the focal spot of the anode?

Tungsten Signup and view all the answers

What is the effect of lowering the kVp on film contrast?

It leads to a low contrast film with fewer black and white areas. Signup and view all the answers

What happens to the intensity of X-rays as the distance from the source increases?

Intensity decreases as distance increases. Signup and view all the answers

What is the primary purpose of the cathode in the X-ray tube?

To supply electrons necessary for X-ray production. Signup and view all the answers

What is a characteristic of an X-ray beam produced with a high kilovoltage peak (kVp)?

It generates harder X-rays. Signup and view all the answers

Which statement is true regarding the structure of the X-ray tube?

There is no air in the tube enclosure to prevent electron loss. Signup and view all the answers

Study Notes

I. RADIATION HISTORY

Wilhelm Roentgen discovered X-rays in 1895
He was experimenting with cathode ray tubes

II. RADIATION PHYSICS

Ionization: The process where an atom gains or loses an electron, becoming electrically unbalanced.
An ion pair forms when an electron is removed from an atom during ionization.
- Positive ion: Atom that loses an electron
- Negative ion: Ejected electron
Ionizing Radiation: Radiation capable of creating ions by adding or removing electrons from atoms. X-rays produce ionization
- Particulate Radiation: Tiny particles with mass travelling in straight lines at high speeds.
  - Electrons
  - Beta particles
  - Cathode rays
  - Protons
  - Alpha particles
  - Neutrons
- Electromagnetic Radiation: Wave-like energy propagation without mass.
  - Cosmic rays
  - Gamma rays
  - X-rays
  - Ultraviolet rays
  - Microwaves
  - Radio waves
  - Visible light
  - Velocity: Speed of a wave.
  - Wavelength: Distance between crests of consecutive waves.
  - Frequency: Number of wavelengths passing a point in a given time.
  - X-ray: Electromagnetic ionizing radiation with very short wavelengths resulting from high-speed electrons hitting a target (tungsten) in a vacuum.

III. PROPERTIES OF X-RADIATION

X-rays are wave-like; travel at the speed of light (186,000 miles/second).
X-rays can penetrate substances
X-rays are invisible
X-rays have no mass, no weight, and no charge
X-rays are absorbed by matter.
X-rays affect living tissue; able to stimulate or destroy live cells
X-rays lose intensity with distance; travel in straight lines and cannot be focused to a point.

III. RADIATION CHARACTERISTICS

Kilovoltage Peak (kVp): Electrical pressure between electrodes. Determines the penetrating power (quality) of the X-ray beam. Higher kVp = faster electrons = harder X-rays = more penetrating ability.
- Density: Overall darkness or blackness of a film. Higher kVp = darker film.
- Contrast: Sharpness of dark and light areas on a film. Lower kVp = higher contrast (black/white), Higher kVp = lower contrast (more shades of gray).
Milliamperage (mA): Quantity of electrical current, Influencing the number of electrons travelling from cathode to anode. Higher mA = more electrons available, more x-rays produced. Also affects the temperature of tungsten filament. Higher mA = increased density on the resulting image. Exposure time and mA together form mAs.

IV. RADIATION BIOLOGY

Ionization: results in positive atom and dislodged electron. Can affect cells but damage may be repairable or permanent.
Free Radicals: a neutral atom or molecule with an unpaired electron in its outermost shell. Highly reactive, especially when water is ionized.
Adverse reactions of body to radiation can accumulate over time.
Somatic Effects: Effects on the person exposed (e.g., cancer, cataracts).
Genetic Effects: Effects that can be passed down to future generations.
Radiation Effects on Cells: Cell sensitivity depends on factors like rate of cell division, and metabolism.

V. RADIATION PROTECTION

Filtration: Reduces the amount of low-energy X-rays before reaching patient. Improves image quality.
Collimation: Restricts the size of the X-ray beam. Reduces scatter radiation.
Position Indicating Device (PID): Cone-shaped attachments to restrict the X-ray beam.
Shielding: Protective barriers, aprons, collars. Reduces radiation exposure to operator and patient. This will reduce the scatter and radiation exposure to the operator (more shielding).
Distance: X-rays lose intensity with distance.

VI. DENTAL X-RAY IMAGE CHARACTERISTICS

Sharpness - ability to accurately reproduce clear details of an object on the image. Factors influencing include: focal spot size, film composition, and movement. Smaller focal spot sizes result in greater sharpness.
Magnification - representation of an object on the film, larger than the actual size. Target-to-film distance and object-to-film distance influence magnification.
Distortion - variation in the true size and shape of the object in the image. Minimized with parallel alignment of object, film and beam direction.

VII. FILM PROCESSING

Manual Processing: Developer softens and reduces the exposed silver halide crystals into black metallic silver. Rinsing and fixer steps remove unexposed crystals. Water baths wash excess chemicals.
Automatic Processors: concentrated chemicals and higher temperatures are used in automatic processing.

VIII. PROCESSING AND TECHNIQUE ERRORS

Appearance of films: Common problems like completely black/clear if no x-ray exposure or excessive/insufficient development.
Errors resulting from positioning/technique: Errors in angles to film and/or positioning of patient or equipment produce issues such as out-of-focus teeth/issues with imaging position.

IX. LOCALIZATION TECHNIQUES

Buccal Object Rule: Movement of structure on second film relative to the first (positioned to lingual/buccal).
Right Angle Technique: Occlusal film for proper angulation results in image visualization of structures.

X. NORMAL ANATOMY BASICS

Landmarks identified in xrays.

XI. COMMON RESTORATIVE MATERIALS

Radiographic appearance of various dental materials.

XII. EXTRAORAL FILMS, PANORAMIC ERRORS

Identifying possible errors during or in the process of producing panoramic films.

XIII. PANORAMIC ERRORS

Errors in technique and positioning (Frankfort plane, midsagittal plane) and other visible problems.

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Description

Test your knowledge on the history and types of radiation. This quiz covers key concepts like ionization, types of radiation, and the contributions of Wilhelm Roentgen. Perfect for students studying physics or those interested in the science of radiation.