Radiology - Board Review!
Dental radiation exposure risks
(fairly high to high sensitivity) Thyroid gland Bone marrow Skin Eyes - High
Zygoma
- A diffuse, RO band extending posteriorly from the zygomatic process of the maxilla
3 conditions must exist for x-rays to be produced
- A source of free electrons - High voltage to impart speed to the electrons - A target that is capable of stopping the electrons
High voltage circuit:
- Accelerates the electrons from the cathode- to anode+ target - 65K to 100K Volt - Controlled by kV setting, velocity needed to shoot from filament to target
Silver points
- Are used with root canals to fill the canals. They are metal and appear much like metal restorations. Appears radiopaque, but appears more radio dense than gutta percha.
Cemental caries radiographic appearance
- Becomes evident once it enters into advanced stage
Mistaken for caries on radiographs
- Cervical burnout: RL at thin cervical root surface inferior to crown - Mach band effect: optical illusion of RL lines caused by overlapping - Non-metallic restorations: RL appearance of composite, bases, resins
Film processing
- Converts a latent image to a visible image that is permanent - Safelight used in dark room w 15 watt or less (red light) at least 4 feet away - There is NO rinse step between developer and fixer when using an automatic processor - Consists of 5 steps: 1. Development: hydroquinone and elon, softens the film emulsion, converts exposed silver halide crystals to black metallic silver 2. Rinsing: stops the development process, removes developer from film 3. Fixing (clearing agent): sodium thiosulfate and ammonium thiosulfate aka HYPO, removes unexposed silver halide crystals, hardens film emulsion 4. Washing: removes all excess chemicals from emulsion 5. Drying: films must be dried before they can be handled
What is in the anode(+)?
- Copper stem - Target - Step-up transformer - kVp
Object localization
- Definitive method: Based on principles of shadow casting, if positioned farther way will be magnified and less clear, if it is clear it is likely to be on lingual closest to receptor - Right angle method: expose a cross-sectional occl. at a right angle to right angle to see if object is buccal or lingual - Tube-shift method: 2 images needed using SLOB, same, lingual, opposite, buccal, if moves in same direction it is lingual, if moves in opposite direction it is buccal
Milliamperage (mA)
- Determines the number of electrons passing through the cathode filament and the quantity of x-rays Increase in mA: increases temperature - Increases number of electrons which increases number of x-rays - Increases density which makes it darker - Uses 7-15 mA Image density: - Increased mA = darker image (increased density) - Decreased mA = lighter image (decreased density) - When mA is increased, exposure time is decreased
Kilovoltage (kV)
- Determines the speed of electrons and QUALITY of x-rays - Dental radiography uses 65-100kV - Image density: overall darkness of an image - Increased kV = darker image (decrease exposure time) - Decreased kV = lighter image - kVp and time are the ONLY things that affect contrast Low kV: - 65-70 = high contrast image - Black/white, few shades of gray - Short scale contrast - Good for caries detection High kV: - >90 = low contrast image - Many shades of gray (Because it was able to penetrate some structures that are more dense/radiopaque in a lower kVp) - Long scale contrast - Good for perio and periapical disease detection
Cone Beam Computed Tomography (CBCT)
- Developed 1990s - Produces a 3D image - Good for assessing implants and ortho, eval with tooth extraction and impaction and guide for reconstructions
Stochastic effect: Long Term of Chronic effects
- Direct function of dose - Probability of the occurrence - Severity of the effects - No dose threshold
2 theories of biological effects
- Direct: 1/3 of biological alterations, x-ray photon collides with cells and breaks them apart - Indirect: radiolysis of water, poison water theory, can cause chemical damage to a cell by ionizing water within it, ionization causes water molecules to break into hydrogen and hydroxyl radical and reform into hydrogen peroxide
Electricity and x-ray productions
- Electricity: flow of electrons through a wire - Direct current (DC): study flow of electrons in one direction, not in US - Alternating current (AC): pulsing flow of electrons in both directions, in US
Exposure timer
- Establishes the time during which electrons are available for bombardment of target material - The higher the setting the more electrons available for x-ray production
Occlusal caries radiographic appearance
- Evident and distinguished in advanced and severe stage
Buccal/lingual caries radiographic appearance
- Evident once enters into advanced stages
Units of measurement
- Exposure: coulombs /kg - amount of radiation in the air - Dose: Gray (Gy) - amount of radiation absorbed by the tissue - Dose equivalent: Sievert (Sv) - measurement of the effect on the tissue - International commission of radiation units and measurements (ICRU) established standards 1. Traditional units (older) - Roentgen (R) - Rad (radiation absorbed dose) - Rem (radiation equivalent in man) 2. Systeme International (SI) units (newer) - Coulombs per kilogram (C/kg) - Gray (Gy) - Sievert (Sv)
Position-indicating device (PID)
- Extension of the x-ray tubehead used to direct the beam - Longer the PID the less divergence of beam (more time to shape beam)
What is in the cathode(-)?
- Filament - Focusing cup - Step-down transformer - mA - Timer
Intraoral film composition
- Film base: 0.2 mm thick piece of polyester plastic (what you hold), provides stable support for emulsion - Adhesive layer: covers both sides of film base (the glue) - Film emulsion: coating mixture of gelatin and silver halide crystals (absorb radiation) and covers both sides of film base - Protective layer: thing coating over delicate emulsion to protect it (like saran wrap)
Fogged film causes:
- Film looks gray and lacks image detail and contrast - Improper safelighting and light leaks in darkroom - Improper film storage - Outdated films - Contaminated processing solutions
Properties of tungsten
- High atomic number - High melting point - Good conductor of heat - Can also be drawn into fine wires (used in filament part of x-ray tube)
Filtration
- Inherent filtration: glass window of x-ray tube, insulating oil, tubehead seal - Added filtration: aluminum disk - Total filtration: sum of inherent and added filtration, results in higher energy/more penetrating useful beam Above 70 kVp must have a total filtration of 2.5mm aluminum Below 70kVp need to have a total filtration of 1.5 mm
Inverse square law
- Intensity of radiation is inversely proportional to the square of the distance from the source of radiation - When distance is doubled = beam is 1/4 as intense - When distance is 1/2 = beam is 4x as intense
Types of radiation injury
- Ionization: all ionizing radiation is harmful, dental exposure is minimal - Free radical formation: most common (70%) type of cell damage in humans, created by ionization of water in cells but eventually join back together again (indirect theory)
Transcranial extraoral image
- Like lateral cephalometric (position laterally see entire skull) but beam is at a +25 degree angle
Cell sensitivity - radioresistant
- Mature bone and cartilage - Nerve - Muscle - Salivary glands - Thyroid gland??? - Kidney - Liver
Maximum Permissible Dose (MPD)
- Max dose a body can receive with little to no injury - Occupational: 5 rem/yr (5000 mrem) or 0.05 Sv/yr (50mSv) - Non-occupational: 0.5 rem/yr (500mrem) or 0.005 Sv/yr (5 mSv) - It is 10x less for non-occupational - ME: 5rem-50mSv - them: 0.5rem-5mSv?? Class: Non-occupational 1mSv/year (.001 sV = 0.1 rem/year)
Occlusal vertical angulation
- Max topographical occl. anterior: +65 - Max topographical occl. posterior: +45 - Mand topographical occl. anterior: -55 - Mand topographical occl. posterior: -45 - Mand cross-sectional occl.: 0
Collimation (lead washer)
- Maximum size of beam at patient's face not to exceed 2.75 in
Cell sensitivity - radiosensitive
- More sensitive cells are rapidly dividing and young cells - Lymphatics - Blood cells - Bone marrow - Reproductive cells - Intestinal mucosa - Skin - Lens of eye - Oral mucosa - Immature bone - Epithelial cells
Paralleling technique (PAs)
- Most likely to create best image - Object-receptor distance: must be increased to keep receptor parallel with long axis of tooth - Target-receptor distance: must be increased to ensure that only most parallel rays will strike tooth Errors: - Vertical angulation is excessive: cut off incisal edges - Vertical angulation is inadequate: apices cut off - Horizontal angulation: overlap - Point of entry: cone cut
Interactions of x-radiation with matter (secondary radiation)
- No interaction This type of interaction (or lack thereof) is responsible for producing densities (radiolucency) that make dental radiography possible - Coherent scatter: Low energy x-ray scattered in different direction (8%) - Absorption or Photoelectric effect: x-ray is completely absorbed and vanishes (30%) - Responsible for radiopacities - Compton effect: new, weaker x-ray is formed and scattered in new direction (62%) An x-ray photon collides with a loosely bound, outer-shell electron and gives up part of its energy to eject the electron from its orbit. The x-ray photon then changes direction and scatters around other atoms until it loses its energy. The ejected electron is termed a Compton electron or recoil electron 1. No interaction (9%): - x-ray photon can pass through an atom unchanged and no interaction occurs 2. Coherent scattering (8%): - Incoming x-ray photon interacts w electron by causing electron to vibrate at same frequency as incoming photon. - Incoming x-ray no longer exists. - The vibrating electron emits a new, unmodified x-ray photon that is scatter but in a different direction. 3. Photoelectric effect (30%): - Incoming x-ray photon collides w an orbital electron - Conveys electromagnetic energy to electron in form of kinetic energy - Kinetic energy knocks electron from orbit creating an ion pair 4. Compton scattering (60%): - Similar to photoelectric effect - Only a part of the x-ray energy is transferred to the electron - A new, weaker x-ray photon is formed and scattered
Latent period
- Period of time from exposure to visible damage - More radiation/faster dose = shorter latent period (ex. sunburn) - Less radiation/slower dose = longer latent period - Proper radiation doses allow for tissue repair
Gutta percha
- Plastic type of filling material used in endodontics
Pediatric exposure
- Primary exposure: reduce adult exposure by 1/2 - Mixed dentition: reduce adult exposure by 1/2-1/4
Inverted Y
- RO upside down Y formed by intersection of lateral wall of nasal fossa (nasal sinus is over ant teeth) and anterior border of max sinus (max sinus is over post teeth) - Located above maxillary canine on canine PA (canine has a longer, sharper root)
Protection for the radiographer
- Radiographer must avoid primary beam - Stand 6 feet away and 90-135 degree angle from beam - Wear radiation monitoring badge
Cervical burnout
- Radiolucent artifact seen on dental images Appears as a collar-shaped or wedge-shaped area between the CEJ and alveolar bone - May also appear as an ill-defined wedge-shaped radiolucency on the mesial or distal root surfaces near the CEJ of posterior teeth
Film speed is determined by what?
- Size of silver halide crystals: larger crystals = faster speed = less radiation but also reduces sharpness - Thickness of emulsion: thicker = faster = less radiation - Presence of special radiosensitive dyes
Retention pins
- Small metal pins placed for restoration retention
Non-stochastic effect: Acute effects
- Somatic effects - Threshold - Larger radiation doses - Acute reactions - Can see them in the patient
Transformers
- Step down transformer: decreases voltage entering into tube - Step up transformer: increases voltage to propel electrons - Autotransformer: before anode and cathode circuits (power constant)
Radio activity
- The emission of ionizing radiation or particles caused by the spontaneous disintegration (decay) of atomic nuclei
Half-value layer (HVL)
- The thickness of material that, when placed in the path of the x-ray beam, reduces the exposure rate by 1/2 - Aluminum filters are placed in the path of the beam inside the x-ray tubehead
Correlation between the damage of tissue with the amount of radiation received 3 dose response curves:
- Threshold curve - Linear curve - Linear Non-threshold curve (This is what we work under in dentistry) - A response is seen at any dose - No matter how small the dose of radiation, cell damage will occur
What determines radiation injury?
- Total dose - Dose rate - Amount of tissue irradiated - Cell sensitivity - Age
Image receptors for digital images
- Up to 50-90% radiation reduction when using digital vs traditional film Direct digital imaging: - Made up of a grid of light-sensitive cells (pixels) - Charge-coupled device (CCD) - Complementary metal oxide semiconductor active pixel sensor (CMOS-APS) - Wired or wireless - Rigid - Sizes 0-2 Indirect digital imaging: - Plate captures x-ray energy as analog data and indirectly produces a digital images on a computer when scanned - Photostimulable phosphor (PSP) - Wireless - Thin and flexible - Sizes 0-4
Extraoral x-ray film
- Used for images like panos and cephalometric - Requires a cassette with a screen in it - Sensitive to fluorescent light, instead of direct exposure to direct radiation - Intensifying screen inside cassette transfer the x-ray energy into visible light - Visible fluorescent light then exposes the film - Process lowers the radiation dose to the patient
Post and build up
- Used in a root canal treatment to strength and the tooth and aid in fabrication of the final restoration
What does a step-wedge do?
- Used to test the amount of radiation reaching the image receptor through each of the increments
Evolution of radiology
- Wilhelm Conrad Roentgen discovered xrays in 1895 - Received 1st nobel prize in 1901 - Called then Roentgen Rays - Called them x-rays because the x was unknown - Began as glass plates wrapped in black paper and rubber - Digital was introduced in 1987
Contrast is only affected by what?
- kVp
X-ray beam intensity
- kVp: higher kVp = increased intensity of x-ray beam - mA: higher mA = x-ray beam with more energy, increasing the intensity of the beam - Exposure time: longer time = more x-rays and more intense beam - Distance: increase distance = reduction of intensity in beam
Density is primarily affected by what?
- mA and time (time is the easiest factor to change) - Secondarily by kVp
Field of View (FOV)
-Region of interest of the patient anatomy -Smallest FOV is used to obtain necessary diagnostic information -Small, medium, large
Typical exposure time for digital radiographs
0.06 seconds
Typical exposure time for conventional film based radiographs
0.125 seconds
ICRU - International Commission on Radiation Units and Measurements Measurements of radiation
1 rad = 0.01 Gray (Gy) 1 rem = 0.01 Sievert (Sv)
Sources of radiation
1. Background radiation: - 50% of exposure for most people - Radon - Terrestrial and space sources - Internal sources natural exposure 2. Medical applications: - 48% of overall exposure for most people - CBCT - Nuclear medicine - Interventional fluoroscopy - Conventional radiography/fluoroscopy 3. Consumer, industrial, occupational exposures: - 2% of overall exposure for most people
Sharpness is determined by
1. Focal spot size (tungsten target, source - small is better) 2. Film composition (halide crystal and emulsion) 3. Motion (patient, receptor, PID)
Sequence of radiation injury
1. Latent Period 2. Period of Injury 3. Recovery Period
Radiation types (primary vs secondary vs scatter)
1. Primary Radiation: Penetrating x-ray beam that is produced at the target of the anode. This beam is also referred to as the primary beam or useful beam 2. Secondary Radiation: Created when the primary beam interacts with matter (i.e. head, bones, teeth). Less penetrating than primary radiation. 3. Scatter Radiation: Form of secondary radiation that is deflected in all directions and can be detrimental to the patient and the radiographer
What are the two primary methods of determining the buccolingual location of objects?
1. Right-angle Technique (Occlusal projection) 2. Tube-shift technique (SLOB rule)
Normal Alveolar Crest height
1.5-2mm apical to CEJ
One CBCT scan can result in how many individual 2D basis images?
150-1,000 individual 2D basis images
Average natural background radiation
3 mSv/year
The annual effective dose of radiation from all sources of the US population is?
6.2 mSv
How many impulses are in a second?
60
What is conventional film exposure time vs the digital?
8 impulses for film 8/60 (0.13) of a second 4 or 5 impulses for digital sensor 4-5/60 (0.06-0.08) of a second
Digital subtraction
A method of reversing the gray scale as a digital image is viewed
Complimentary Metal-Oxide Semiconductor (CMOS)
A solid state detector that contains a silicone chip and is similar to the CCD but it differs in: - The way the pixels are read - Has built-in control functions - Smaller pixel size - Lower power requirements - Production cost of the chip is lower
Charged Coupled Device (CCD)
A solid-state detector that contains silicon chip that is sensitive to x-rays or light and is an analog-to-digital converter by process of electrons deposited in each pixel transferred in a sequential manner to a read-out for image display on the monitor Most commonly used
Cone beam Computed Tomography (CBCT)
A three-dimensional digital imaging method that uses a cone-shaped beam of radiation that rotates around the patient.
Radiation safety councils
ADA Council on Scientific Affairs U.S. Department of Health and Human Services Public Health Service FDA These agencies have adopted guidelines for prescribing the number, type, and frequency of dental images.
What size sensor would you use for occlusal projection?
Adult: Size 4 Pedo: Size 2
DICOM images
Allow practitioner to see field of view in 3D Data viewed in 3 planes: 1. axial 2. coronal 3. sagittal
At a distance of 2ft from the x-ray tubehead the exposure intensity is 16 C/kg. If the distance is 4ft what is the intensity?
Answer: 4 C/kg
Supports and encases roots of teeth
Aveolar Bone
What radiographs are most reliable for crestal bone evaluation?
Bitewings
Computer-assisted three-dimensional digital imaging in dentistry
CBCT
Solid state detector that contains silicone chip that is sensitive to x-rays or light and has an active transistor built into each pixel that requires less system power to process image, offers durability and resolution
CMOS
Solid-state detector that contains silicon chip that is sensitive to x-rays or light and is analog to digital converter by process of electrons deposited in each pixel transferred in a sequential manner to a read-out for image display on the monitor
Charged coupled device (CCD)
Arrange the annual sources of radiation exposure in the U.S from smallest to largest Medical procedures Radon and thoron Cosmic (space) Consumer products Terrestrial (soil)
Consumer products Terrestrial (soil) Cosmic (space) Medical procedures Radon and thoron
Coronal portion of alveolar bone found between teeth
Crestal bone (alveolar crest)
What is phase 1 of CBCT?
Data acquisition Xray unit connected to an x ray detector that circles the head of a patient producing 2D radiographic images
What is phase 2 of CBCT?
Data reconstruction Reconstructing series of images into 3D information
cortical plate
Dense supporting bone that serves to sustain the alveolar bone on the buccal/facial and lingual surfaces
X-ray photons come in contact with intraoral sensor causing electrons to be released from silicone chip and produce latent image. Electrons travel to computer converted into pixel arrangements that can be visualized on computer monitor
Direct digital
What are the three different methods of producing a digital radiograph?
Direct digital (1) Indirect digital - Scan conventional radiographs (2) - Storage phosphor imaging (3)
What is waters projection used for? Where is it placed?
Eval maxillary sinus Midsagittal plane of head is perp to the film Chin touches the film, tip of nose is 0.5-1 inch from cassette Xray beam is perp to film (coming from behind the pt)
Why do we use TMJ imaging? Where is it placed?
Evaluate superior surface of condyle, L and R joint spaces, open and closed positions Cassette is placed flat against ear, centered over TMJ Central ray goes above and behind ear canal at +25 degrees downward angle
T/F - Occlusal technique should not have cone cuts on film
FALSE Cone cuts are common and acceptable with occlusal technique
T/F - Occlusal film processing times are longer than PA or BW
FALSE they are the same
The two mechanisms in which the kinetic energy of electrons is converted into x-ray photons (What are the two ways x-ray photons are created at the tungsten target?)
General/Bremsstrahlung/Braking radiation: - Majority of production (70%) - Produced when high-speed electrons are stopped or slowed down by tungsten atoms - Produced when an electron hits the nucleus (one strong x-ray) of a tungsten atom or it passes very close to the nucleus (multiple weaker x-rays) - The energy here comes from the loss of energy from the electron "braking" and not from dislodging a secondary electron - As a result, this type of radiation accounts for many different energies and wavelengths Characteristic radiation: - Produced when a high-speed electron dislodges an inner-K shell electron - Occurs only at 70 kV and above - Accounts for a very small part of x-rays produced
Axial Image
Horizontal plane dividing into superior and inferior slices
Right angle technique
Identifies buccolingual location, also may confirm mesiodistal location seen on periapical - Once you have identified an object on the periapical film, you can take an occlusal film with the beam at a right angle (perpendicular) to the direction of the beam for the periapical
How to properly diagnose periodontitis
Identify attachment loss Identify the form of periodontitis - Necrotizing, manifestation of systemic conditions or periodontitis Description of the presentation (staging and grading)
Why do we use cephalometric? Where is it placed?
Image lateral view of the skull Evaluate growth and development of ortho, facial reconstruction Pts midsagittal plane must be perp to the floor and parallel to cassette Central ray directed perp and through center of cassette
Frankfort plane
Imaginary plane that passes through the top of the ear canal and the bottom of the eye socket
Annual effective dose increase for radiation
Increase to 6.2 mSv/year largely due to medical technology up from 15% to now 48%
Scanning of conventional radiograph, converting image from analog to digital and then display on computer monitor
Indirect digital
What is CBCT projection data?
Individual 2D images that make up the 3D image
labial mounting vs lingual mounting
Labial is what we use: Raised side of dot on film faces the viewer (clinician) ADA recommends labial mounting. Lingual mounting the dot faces away from clinician - The films are viewed as if you are standing on the patient's tongue
Extraoral image types
Lateral cephalometric image: - Evaluate facial growth and development, trauma and disease - Side image Posteroanterior projection: - Evaluate facial growth and development, trauma and disease - Facing forward, straight on Waters projection: - Evaluate maxillary sinus area - Nose up Reverese towne projection: - Identify fractures of condular neck and ramus area - Head tilted down w mouth open Submentovertex projection: - Identify position of condyles, demonstrate the base of the skull and evaluate fractures of zygomatic arch - View straight up from chin
What are common extraoral imaging techniques?
Lateral jaw imaging Temporo-mandibular joint Cephalometric Waters projection CBCT Pano
Advantages of 3D Digital Imaging
Lower radiation dose* Brief scanning time Anatomically accurate images 1:1 ratio Ability to save and easily transport images *Higher radiation than digital panoramic, cephalometric, or 4 BWX intraoral radiography (but maybe lower than an FMX??)
What are the projections and corresponding vertical angulations for - Maxillary occlusal film
Max arch is parallel to the floor angulation is set at 65 degree for anterior image and 60 degrees for lateral
Occlusal Projections and Corresponding Vertical Angulations
Max topographic: +65 Max lateral: +60 Max pediatric: +60 Mand topgraphic: -55 Mand cross sectional: 90 Mand pediatric: -55
What are other characteristics of normal alveolar crest?
Parallel to line joining CEJ of adjoining teeth Smooth Continuation of lamina dura, has the same radiopacity
What are the projections and corresponding vertical angulations for - Mandibular occlusal film
Patient is laid back so occlusal plane is as close to perpendicular as possible and the tubehead is placed under chin making a 90-degree angle
Digital equivalent of a sliver crystal used in conventional radiograpy
Pixel
Subtraction radiography
Purpose is to produce 2 radiographs of same area in mouth at different time intervals and identify changes that may have occurred
Quality vs Quantity - what affects them?
Quality is increased with increase in kVp or an increase in filtration Quantity is increased with an increase mA and exposure time
What is the difference between REM and RAD?
RAD - is the amount that is absorbed within different tissues REM - is the amount factored generally for all tissues in the body
What is the American equivalent for Sievert?
REM
Dental x-ray image characteristics
Radiolucent: - Area of image that is dark/black - Structures are thin and x-rays fly through hitting the receptor - Things like decay or air space Radiopaque: - Area of image that appears white or light gray - Structures are dense and absorbed/blocked from hitting the receptor - Things like bone or metal crowns Sharpness: - Distinct outlines of an object - Lack of sharpness = penumbra = fuzzy/blurred area around an image - Influenced by focal spot size (smaller=sharper), film composition (smaller crystal size=sharper) and movement (less sharp) Magnification: - Magnification is increased by a short PID = short target/receptor distance - Magnification is increased by increased object/receptor distance Distortion: - Variation from true size/shape of object being imaged - Influencing factors are: -- Object/film alignment must be parallel to each other -- X-ray beam angulation: beam must be perpendicular to tooth and film
What is the #2 reason for lung cancer?
Radon
The SI unit for measuring radiation dose equivalent is termed
Sievert
After radiation exposure, captures image and high speed scanner used to convert information into electronic image
Storage phosphor imaging
Purpose to produce 2 radiographs of same area in mouth at different time intervals and identify changes that may have occurred
Subtraction radiography
What does SI stand for?
System International
What is a cephalostat (craniostat)?
The arm extensions that hold the head in place during extraoral imaging
Umbra and Penumbra
The image of a tooth or other structure is called the umbra, or complete shadow The unsharp, blurry area around the umbra is called the penumbra
Why do we use lateral jaw imaging? Where is it placed?
Used for pts with limited jaw opening/ difficulty with intraoral receptors Cassette is placed against cheek and centered over body of mandible Head is tipped 15 degrees to side being imaged Central ray is 15-20 degrees perp to horizontal of receptor size 4 receptor
Tube shift technique (SLOB rule)
Utilizes two films with different horizontal or vertical angulations - Same Lingual, Opposite Buccal
Coronal Image
Vertical plane dividing into anterior and posterior slices
Sagittal image
Vertical plane dividing into right and left slices
Voltage vs Amperage
Voltage = Force of electrons Amperage = AMount of electrons
Properties of x-rays
Weightless bundles of energy (photons), invisible, travel in straight lines, travel at speed of light, no charge, impact w/ matter causing ionization, can penetrate tissues & structures, can cause biologic changes is living cells, & can affect photographic film emulsion
Storage phosphor imaging
Wireless digital radiography Image plate is used (PSP - Photostimulable phosphor plate) Plate is flexible: similar to intensifying screen Plate stores image: high speed scanner converts information onto electronic files Less rapid than direct imaging
Film packaging
X-ray film: - 1 or 2 films with emulsion on both sides - ID dot used to determine film orientation Paper film wrapper: - Black protective sheet that covers film to protect from light Lead foil sheet: - Located behind the film - Shields the film from scatter radiation - Has a pattern that will be visible be visible if film is placed improperly Outer package wrapping: - Soft vinyl or paper to seal film contents and protect them from light and moisture - Tube side: usually white with raised bump, faces x-ray - Label side: has film info and a flap to open flap
Ionization steps
X-ray photon interacts with tissue --> Ionization: breaking of bonds occurs --> Chemical changes can take place --> Biological changes
You usually take a bitewing at 12 impulses. Which of the following exposure time is the same a. .12 sec b. .2 sec c. .6 sec d. 1.2 sec e. 2.4 sec
b. .2 Math: 12/60 = 0.2
The SI unit for measuring radiation dose equivalent is termed a. coulomb b. gray c. rem d. roentgen e. sievert
e. Sievert
Peri implantitis
inflammatory reaction in the hard and soft tissues surrounding a dental implant that results in bone loss
What is the ideal temperature for manual vs automatic processor?
manual - 68 degrees auto - 82 degrees
When viewed together DICOM images are referred to as:
multiplanar reconstructed images (MPR images)
SLOB rule example
on the buccal
What is the shape of the CBCT x-ray beam?
pyramidal or cone shaped
Thermionic emission
the release of electrons from the tungsten filament (wire) when the electrical current passes through it and heats the filament = ELECTRON CLOUD Uses step-down transformer (low-voltage circuit) 3-5 volt Controlled by mA setting, increase mA = increase number of electrons
When should vertical BWs be used?
when pocket depths are beyond 5mm
