Lecture 2 Flashcards
What is an X-ray?
A beam of energy that has the power to penetrate substances and record image shadows on receptors (photographic film or digital sensors).
What is radiation?
A form of energy carried by waves or a stream of particles.
What is radiology?
The study of images produced on a receptor by exposure to ionizing radiation.
What is a radiograph?
An image or picture produced on a receptor (radiation-sensitive film, phosphor plate, or digital sensor) by exposure to ionizing radiation; a two-dimensional representation of a three-dimensional object.
Who is a dental radiographer?
Any person who positions, exposes, and processes dental x-ray image receptors.
What is an image?
A picture or likeness of an object.
What is an image receptor?
A recording medium; examples include x-ray film, phosphor plate, or digital sensor.
Uses of dental radiograph
• To detect lesions, diseases, and conditions of the teeth and surrounding structures that cannot be identified clinically
• To confirm or classify suspected disease
• To localize lesions or foreign objects
• To provide information during dental procedures (e.g., root canal therapy, placement of dental implants)
• To evaluate growth and development
• To illustrate changes secondary to caries, periodontal disease, and trauma
• To document the condition of a patient at a specific point in time
• To aid in development of a clinical treatment plan
Who discovered x-rays?
Roentgen discovered x-rays in 1895.
Who made the first dental radiograph?
Otto Walkhoff made the first dental radiograph.
Who was the first to practically use radiographs?
C. Edmund Kells was the first to practically use radiographs in 1896.
What health issues did C. Edmund Kells face due to x-ray exposure?
C. Edmund Kells exposed his hands to numerous x-rays every day for years, developing numerous cancers in his hands and ultimately losing his fingers, hands, and then his arms.
What is the charge of most atoms?
Most atoms are neutral.
What does a neutral atom contain?
A neutral atom contains an equal number of protons and electrons.
What are the charges of protons and electrons?
Protons have positive charges and electrons have negative charges.
What is an ion?
An atom that gains or loses an electron and becomes electrically unbalanced is known as an ion.
What is ionization?
Ionization is the production of ions, or the process of converting an atom into ions.
The loss and gain of which molecule in an atom leads to ionization?
Ionization deals only with electrons and requires sufficient energy to overcome the electrostatic force that binds the electron to the nucleus.
What happens when an electron is removed from an atom during ionization?
When an electron is removed from an atom in the ionization process, an ion pair results.
The atom becomes the positive ion, and the ejected electron becomes the negative ion.
What occurs after an ion pair is formed?
This ion pair reacts with other ions until electrically stable, neutral atoms are formed.
Ionizing radiation can be defined as
radiation that is capable of producing ions by removing or adding an electron to an atom.
Long wavelength=
Low frequency
Short wavelength=
High frequency
What is the appearance of X-rays?
X-rays are invisible.
Do X-rays have mass?
X-rays have no mass or weight.
What is the charge of X-rays?
X-rays have no charge.
At what speed do X-rays travel?
X-rays travel at the speed of light.
What is the wavelength of X-rays?
X-rays travel in waves and have short wavelengths with a high frequency.
How do X-rays travel?
X-rays travel in straight lines and can be deflected, or scattered.
Can X-rays be focused?
X-rays cannot be focused to a point and always diverge from a point.
What is the penetrating power of X-rays?
X-rays can penetrate liquids, solids, and gases.
What determines the absorption of X-rays?
The absorption depends on the atomic structure of matter and the wavelength of the x-ray.
What is the ionization capability of X-rays?
X-rays interact with materials they penetrate and cause ionization.
Can X-rays cause fluorescence?
X-rays can cause certain substances to fluoresce or emit radiation in longer wavelengths.
What effect do X-rays have on receptors?
X-rays can produce an image on a receptor.
What effect do X-rays have on living tissues?
X-rays cause biologic changes in living cells.
What are the component parts of a dental X-ray machine?
• (1) control panel
• (2) extension arm
• (3) tubehead
List all parts
A. X-ray tube
B. Anode [+]
C. Unleaded glass window of X-ray tube
D. Insulating oil
E. Metal housing of X-ray tubehead
F. Position indicating device
G. Aluminum disks
H. Lead collimator
I. Cathode [-]
J. Filament circuit
K. Tubehead seal
What is this?
X-ray Tube
What does the x-ray tube produce?
The x-ray tube produces x-rays.
What is a x-ray tube?
The x-ray tube is a glass vacuum tube from which all the air has been removed.
What is the purpose of the copper stem?
The purpose of the copper stem is to dissipate heat and conduct it away.
A transformer is a device that is used to
either increase or decrease the voltage in an electrical circuit
- Focal spot on tungsten target
- Glass envelope
- Vacuum
- Copper stem
- Anode (+)
- Useful X-ray beam
- Tube window
- Cathode (-)
- Electronic focusing cap
- Filament electron cloud
What is shown in this picture?
The production of X-rays in the X-ray tube
What is primary radiation?
Primary radiation refers to the penetrating x-ray beam that is produced at the target of the anode and that exits the tubehead.
What is secondary radiation?
Secondary radiation refers to x-radiation that is created when the primary beam interacts with matter. Secondary radiation is less penetrating than primary radiation.
What is scatter radiation?
Scatter radiation is a form of secondary radiation and is the result of an x-ray that has been deflected from its path by the interaction with matter.
Scatter radiation is deflected_____
in all directions by the patient’s tissues and travels to all parts of the patient’s body and to all areas of the dental operatory.
Scatter radiation is detrimental to____
both the patient and the radiographer.
What are the different way an X-ray can interact after being exposed to the patient?
• X-rays can pass through the patient without any interaction.
• X-ray photons can be completely absorbed by the patient.
• X-ray photons can be scattered
What is the effect of all ionizing radiation on living tissue?
All ionizing radiation is harmful and produces biologic changes in living tissue.
What causes radiation injury?
Radiation injury results from ionization or free radical formation.
What are the phases of radiation injury?
Radiation injury follows a sequence of events: latent period, period of injury, and period of recovery.
What factors affect radiation injury?
Radiation injury is affected by total dose, dose rate, amount of tissue irradiated, cell sensitivity, and patient’s age.
How may Xrays lead to biological changes?
What is the mechanism of direct radiation injury?
X-ray photons directly strike the DNA of a cell.
What is the mechanism of indirect radiation injury?
X-ray photons are absorbed within the cell and cause the formation of toxins, which in turn damage the cell.
E.g. H2O2 formed from free radicals.
What are the two mechanisms for radiation injury?
Direct and indirect
A dose-response curve is
used to demonstrate the response (damage) of tissues to the dose (amount) of radiation received.
A threshold dose for damage does not exist, and the response of tissues is_____ to the dose received.
directly proportional
All the cells in the body can be classified as either
somatic or genetic.
Somatic cells are
all the cells in the body except the reproductive cells.
The reproductive cells are
termed genetic cells. (e.g., ova, sperm)
What is this picture demonstrate?
That somatic mutation affects the body of the person exposed, but not future generations, while genetic mutation affects future generations, but not the body of the person exposed
What is total dose in radiation injury?
Total dose refers to the quantity of radiation received, or the total amount of radiation energy absorbed. More damage occurs when tissues absorb large quantities of radiation.
What is dose rate?
Dose rate is the rate at which exposure to radiation occurs and absorption takes place (dose rate = dose/time). More radiation damage takes place with high dose rates because a rapid delivery of radiation does not allow time for the cellular damage to be repaired.
How does the amount of tissue irradiated affect radiation injury?
The amount of tissue irradiated refers to the areas of the body exposed to radiation. Total-body irradiation produces more adverse systemic effects than if small, localized areas of the body are exposed.
An example of total-body irradiation is the exposure of a person to a nuclear energy disaster.
What is cell sensitivity in the context of radiation injury?
Cell sensitivity indicates that more damage occurs in cells that are most sensitive to radiation, such as rapidly dividing cells and young cells.
How does age affect susceptibility to radiation damage?
Age plays a role in susceptibility to radiation damage, with children being more susceptible to radiation damage than adults.
What units are used to define three quantities of radiation?
Unit for exposure: Si unit: C/kg and roentgen-traditional unit
Unit for Dose: Si unit: gray (Gy) or J/Kg
rad - traditional unit
Unit for dose equivalent: Si unit: Sievert (Sv) rem - traditional unit
What are the three quantities of radiation defined by units?
Exposure, Dose, and Dose Equivalent.
In the context of the three quantities of radiation, What does exposure refer to?
Exposure refers to the measurement of ionization in air produced by x-rays.
Measures the amount of energy that reaches the surface of an organism
What is the SI unit for exposure?
C/kg.
What is the traditional unit for exposure?
Roentgen.
In the context of the three quantities of radiation, How is dose defined?
Dose can be defined as the amount of energy absorbed by a tissue.
What is the SI unit for dose?
Gray (Gy) or J/Kg.
What is the traditional unit for dose?
Rad.
In the context of the three quantities of radiation, What is dose equivalent?
Dose equivalent is used to compare the biologic effects of different types of radiation.
What is the SI unit for dose equivalent?
Sievert (Sv).
What is the traditional unit for dose equivalent?
Rem.
“The risks from dental imaging are not significantly greater than
the risks of other everyday activities in modern life.” pg 28
The critical organs at risk from dental imaging include
the thyroid gland and active bone marrow. The skin and eyes may also be considered critical organs.
What is the impact of using digital sensors on radiation exposure?
Using digital sensors reduces radiation exposure by decreasing exposure time by 50% to 90% compared with conventional radiography.
How does the choice of film affect radiation exposure?
The use of F-speed film instead of D-speed reduces the absorbed dose by 60%.
What is the effect of collimation on radiation exposure?
Radiation exposure can be limited by using rectangular collimation, which reduces the absorbed dose by 60% to 70% compared to round collimation.
How can technique influence radiation exposure?
Increasing the target-receptor distance and using the paralleling technique can reduce the skin dose.
What factors reducing exposure during dental imaging?
Receptor choice
Collimation
Technique
The average annual radiation dose per person in the U.S.
6.2 millisieverts
What is a dosimeter?
A dosimeter is a small device worn by dental professionals to monitor their exposure to radiation.
Why is monitoring radiation exposure important for dental professionals?
Monitoring radiation exposure helps ensure that dental professionals stay within safe limits, which is crucial for long-term health.
What are the risks of excessive radiation exposure?
Excessive exposure to radiation can increase the risk of cancer and other health issues.
How do dosimeters contribute to safety in dental clinics?
By using dosimeters, we can make sure that everyone in the clinic is working safely.
What should be done regarding dosimeter usage during pregnancy?
Change checks from Every 3 months to 1 month, inform the program director and main faculty.
What information must dosimeters have?
Dosimeter badges must have each individual’s first and last name.
