Lecture 3 Flashcards
Patient dental image radiation protection occurs when?
Before, during and after exposure
How do we implement patient protection before exposure?
• Proper prescribing of dental images
• Proper equipment: Filtration, Collimation, PID
How do we implement patient protection during exposure?
Lead apron, thyroid collar, image receptor
How do we implement patient protection after exposure?
Proper receptor handling and image retrieval
Effect of x-radiation on living cells and tissues
X-radiation causes biologic changes in living cells and adversely affects all living tissues.
With the use of proper patient protection techniques, the amount of x-radiation received by a dental patient can be____.
minimized
______can minimize the amount of x-radiation that a dental patient receives before X-ray exposure
Proper prescribing of dental images and the use of equipment that complies with state and federal radiation guidelines
What the does the ALARA Principle stand for?
• As Low As Reasonably Achievable
The dentist must prescribe images based on the____.
individual needs of patients
The dental x-ray tubehead must be equipped with ______for patient protection.
appropriate aluminum filters, lead collimator, and position-indicating device
In the x-ray tubehead, aluminum disks are used to_____
filter out the longer-wavelength, low-energy x-rays from the x-ray beam.
Collimation is used to_____
restrict the size and shape of the x-ray beam and to reduce patient exposure.
How does the collimator restrict the size and shape of the X-ray beam to reduce patient exposure?
A collimator, or lead plate has a hole in the middle
Which shape collimator is better to reduce patient exposure?
A rectangular collimator exposes 60% less tissue than a circular collimator
The position-indicating device (PID) appears as______ and is used to_____.
an extension of the x-ray tubehead; direct the x-ray beam
Which is better, an 8 in PID or a 16 in PID?
16 in PID is better because it produces less divergence of the xray beam
PID come in what shape?
Open- ended, lead-lined circular and rectangular PIDs
The use of the thyroid collar is recommended for______.
all intraoral exposures but not recommended with extraoral exposures because it obscures information and results in a nondiagnostic image.
Lead Apron come in different types for____but may or may not come with____
intraoral & extraoral; thyroid collar
Receptor types
• Digital Sensor
• Fast films
Beam Alignment devices help____
stabilize the receptor in the mouth to reduce the chances of movement
One common type of beam alignment device
XCP: “extension cone paralleling”
How can the dental image radiographer/operator protect themselves?
• Shielding
• Distance and Position recommendation
• Radiation Monitoring: Equipment monitoring, Personnel monitoring
Ideally, during exposure, the radiographer should_____
either leave the room or take a position behind a suitable barrier or wall during exposures.
If leaving the room is not possible or if no barrier is available, the radiographer must
adhere to distance and position recommendations. To avoid the primary beam, which travels in a straight line, the dental radiographer must position himself or herself 6 feet away, perpendicular to the primary beam, or at a 90-degree to 135-degree angle to the beam
Primary beam travels____
in a straight line
The dental radiographer should not ____during exposure.
• hold a receptor in place for a patient.
• hold or stabilize the x-ray tubehead.
Dental x-ray machines must be monitored for
leakage radiation.
Leakage radiation is
any radiation, with the exception of the primary beam, that is emitted from the dental tubehead.
For example, if a dental x-ray tubehead has a faulty tubehead seal, leakage radiation results.
Dental x-ray equipment can be monitored for leakage radiation using
a device that can be obtained through the state health department or from the manufacturers of dental x-ray equipment.
The amount of x-radiation that reaches the body of the dental radiographer can be measured through the use of a
personnel-monitoring device known as a radiation monitoring badge
• Also known as dosimeter
• After the dental radiographer has worn the badge for a specified interval (e.g., 1 month), the badge is returned to the service company.
What is the Maximum Permissible Dose (MPD)?
The maximum dose equivalent that a body is permitted to receive within a specific period.
What does the MPD represent?
The maximum dose of radiation that the body can endure with little or no injury.
Who defines the MPD?
Defined by the National Council on Radiation Protection and Measurements (NCRP).
What is the MPD for occupationally exposed persons?
50 mSv/year (0.05 Sv/year or 5.0 rem/year).
What is the recommended maximum dose for dental radiographers?
Not to exceed a maximum dose of 50 mSv in any 1 year.
What is the radiation exposure limit for pregnant dental personnel?
0.5 mSv per month during the pregnancy months.
What is the MPD for nonoccupationally exposed persons?
Approximately 1 mSv/year (0.1 rem/year).
What is the recommended cumulative occupational effective dose according to the NCRP?
An individual’s cumulative occupational effective dose should not exceed the worker’s age multiplied by 10 mSv.
What is the recommended cumulative occupational dose for a 50-year-old worker?
The recommended cumulative occupational dose is no more than 50 × 10 mSv = 500 mSv (0.5 Sv).
How should dental professionals respond to patient’s concerns about radiation exposure?
Show confidence and competence.
What should dental professionals do regarding patient’s concerns?
Acknowledge patient’s concerns.
What information should be provided to patients about radiation exposure?
Inform the patient of the dosage.
What are some examples how operator could respond to a patient’s concern with receiving radiation?
Give examples FMX exposure compared to daily exposure.
Example: ‘Before we expose you to any radiation, the dentist custom-orders your x-rays based on your individual needs. The x-ray equipment we use is tested to ensure that state and federal radiation safety guidelines are met.’
“During x-ray exposure, we use a thyroid collar and a lead apron to protect your body from excessive radiation.”
What are the radiation characteristics?
Radiation characteristics include x-ray beam quality, quantity, and intensity.
What factors affect radiation characteristics?
Affected by X-ray unit buttons for kilovoltage, milliamperege, and time.
How can operators limit patient exposure using the xray unit buttons ?
Operators should use optimal settings.
What is the optimal kilovoltage setting?
The optimal kilovoltage setting is 60 to 80 kV.
What is the optimal milliamperage setting?
The optimal milliamperage setting is 6 to 8 mA.
What is the recommended exposure time for diagnostic images?
Use the shortest exposure time possible to create a diagnostic image.
What is voltage?
A measurement of force that refers to the potential difference between two electrical charges.
What does voltage measure inside the dental x-ray tubehead?
Voltage is the measurement of electrical force that causes electrons to move from the negative cathode to the positive anode.
How does voltage affect the speed of electrons?
Voltage determines the speed with which electrons move. When voltage is increased, the speed of the electrons is increased.
What is the result of increased electron speed due to higher voltage?
The electrons strike the target with greater force and energy, resulting in a penetrating x-ray beam with a short wavelength.
In what units is voltage measured?
Voltage is measured in volts or kilovolts.
What is the unit of measurement for voltage?
The volt (V) is the unit of measurement used to describe the potential that drives an electrical current through a circuit.
What type of voltage do dental x-ray equipment require?
Dental x-ray equipment requires the use of high voltages.
What is the relationship between kilovolts and volts?
Most radiographic units operate using kilovolts; 1 kilovolt (kV) is equal to 1000 volts.
Exposure time refers to
the interval of time during which x-rays are produced. The timer controls the length of exposure time and determines how long the x-rays will be emitted from the machine.
The longer the exposure time,___
the more x-rays are delivered, and a darker image results.
Amperage determines
the amount of electrons passing through the cathode filament.
The ampere (A) is the unit of measure used to
describe the number of electrons, or current, flowing through the cathode filament.
The number of amperes needed to operate a dental x-ray unit is small; therefore amperage is measured in
milliamperes.
One milliampere (mA) is equal to
1/1000 of an ampere.
Intensity
Intensity is the total energy contained in the x-ray beam in a specific area at a given time;
intensity is affected by
kilovoltage, milliamperage, exposure time, and distance.
What is the formula for intensity?
What does contrast refer to in imaging?
Contrast refers to how sharply dark and light areas are differentiated or separated on an image.
What is an image with high contrast?
An image that exhibits areas of black and white is termed high contrast.
What is an image with low contrast?
An image that exhibits many shades of gray is termed low contrast.
What is the result of low kilovoltage (kV)?
When kV is low, the result is low density and high contrast.
What creates an optimal image in radiography?
The optimal image is created when a proper balance between kV and milliamperage (mA) is obtained.
Why is the optimal image considered optimal?
This image is considered optimal because it provides a full range of tones from white to black.
What is the result of high kilovoltage (kV)?
When kV is high, the result is very high density with very low contrast.
What is sharpness in dental imaging?
Sharpness (also known as detail, resolution, or definition) refers to the capability of the receptor to reproduce the distinct outlines of an object—in other words, how well the smallest details of an object are reproduced on a dental image.
What are the influencing factors of sharpness?
The influencing factors of sharpness include:
- Focal spot size
- Film composition
- Movement
What is penumbra?
Penumbra can be defined as the unsharpness, or blurring, of the edges.
What does radiolucent refer to?
Radiolucent refers to that portion of an image that is dark or black.
For example, air space freely permits the passage of dental x-rays and appears radiolucent on a dental image.
What characterizes a radiolucent structure?
A structure that appears radiolucent lacks density and permits the passage of the x-ray beam with little or no resistance.
What does radiopaque refer to?
Radiopaque refers to that portion of an image that appears light or white.
Structures that resist the passage of the x-ray beam include enamel, dentin, and bone and appear radiopaque on a dental image.
What characterizes a radiopaque structure?
Radiopaque structures are dense and absorb or resist the passage of the x-ray beam.
What does the term ‘periodontium’ refer to?
The periodontium refers to tissues that invest and support teeth, such as the gingiva and alveolar bone.
What is the lamina dura?
The lamina dura represents the thin, smooth cortical bone of the tooth socket.
What is the location of the normal healthy alveolar crest?
The normal healthy alveolar crest is located approximately 1.5 to 2.0 mm apical to the CEJ of adjacent teeth.
What does the normal periodontal ligament space appear as?
The normal periodontal ligament space appears as a thin radiolucent line between the root of the tooth and the lamina dura.
