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295 Cards in this Set
- Front
- Back
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Photograph: |
*A picture made from light |
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Radiograph: |
A picture made with radiation |
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Radiograph history? |
*First named "Roentgenograms *Discovered by... William Roentgen *Discovered in 1895 |
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Why do dentists make radiographs? |
*Detect dental caries *Detect alveolar bone loss *Detect periapical disease
(provide medical/legal documentation) |
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Periapical Radiographs: |
*Captures the crown, roots, and some periapical bone. |
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Bitewing Radiographs: |
*Capture crowns and alveolar crests *Can be taken vertical or horizontal |
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Occlusal Radiographs: |
*Display dental arch, and may include palate or floor of mouth. *Useful in determining location of objects in all 3 dimensions.
(supernumerary, unerupted, duct pathology, lateral outline of maxillary sinus, fractures) |
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Cone Beam CT: |
*Cone shaped X-ray beam *Rotates around patient *Reconstructs a 3D image |
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Examples of good radiographic practice: |
*Use of fastest image receptor *Collimation of beam to size of receptor *Proper film exposure/processing *Use leaded apron and thyroid collars, especially in children, childbearing age, and pregnant. |
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How often should bitewing radiographs be utilized in primary dentition through prior to 3rd molar eruption if the proximal surfaces of teeth cannot be visualized? |
*6-12 month intervals |
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How often should bitewing radiographs be utilized in a dentate adult? |
*6-18 month intervals |
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Patient exposure notes: |
*70% of dentists use D-speed film (highest dose) *30% of dentists use digital *Most dentists do not radiograph pregnant women, even though the dental dose of radiation is incredibly low. No restrictions if radiograph is needed for treatment. |
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Alpha Radiation: |
*heavy, positively charged particles *emitted by uranium and radium (etc) *Can be stopped by thin barriers (skin) *Harmful if taken into body
(20x more dangerous than x-rays if ingested) |
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Beta Radiation: |
*High speed electrons *More penetrating, can pass through 1-2 cm of water *Generally, can be stopped by thin aluminum foil. |
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Gamma Rays: |
*Electromagnetic (like x-rays, light, radio) *Can pass though body, but thick walls and lead will stop them. |
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X-Rays: |
*Ionizing radiation *Travel at speed of light, shorter wavelength, and greater energy *no mass, no charge
*When using dental x-rays, the energy is totally gone at 6 feet. |
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True or False:
Dental X-rays have lower exposure compared to medical X-ray exposure. |
True
Mammogram and GI series among highest |
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Exposure:
(Dosimetry) |
*The ability of X-rays to produce ionization of air under standard conditions of temperature and pressure. |
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Dose:
(Dosimetry) |
*The amount of energy that is absorbed per unit mass of tissue at a particular site. |
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Roentgen: |
*Traditional unit of x-ray exposure *500 roentgens in five hours is usually lethal for humans. *Typical exposure... 200 milliroentgens/year |
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What is Effective Dose? |
*An estimate of the stochastic effect that a non-uniform radiation dose has on a human.
*Represents the does the whole body could receive uniformly that would give the same risk as various organs receiving different doses. |
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What is Stochastic Effect? |
*One classification of radiation effects that refer to the random, statistical nature of damage.
*"cancer is a stochastic effect" |
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What is the radiographic examination for a 5 year old without clinical evidence of caries? |
*Posterior bitewings 12-24 month intervals if proximal surfaces cannot be examined visually. |
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What is the radiographic examination for a 55 year old recall patient with a clinical history of caries? |
*Posterior bitewings at 6-18 month intervals |
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Microwaves vs X-rays: |
Microwave: Low energy electromagnetic wave.
X-ray: High energy electromagnetic wave. |
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What will penetrate deeper, an x-ray or a gamma ray? |
*Gamma rays pass straight through the human body, only to be stopped by thick concrete and/or lead. |
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Fluorescense vs. Phosphorescence: |
*Fluorescense: Visible light from irradiation interaction.
*Phosphorescence: Light emission delayed or continue after radiation exposure. |
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Radiation measurements: |
*Rad: Common unit for absorbed dose. -1 erg --> 1g *Rem: Common unit for dose equivalent. -1 rem = 0.01 Seivert *Gray: SI unit for absorbed dose. -1 Gray = 100 rads, 1 J --> 1 Kg matter *Seivert: SI unit for dose equivalent. -1 Seivert = 1 Gray |
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What tissues are radiosensitive? |
*Most: Blood-forming organs
*Least: Nervous system |
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Convert 15 rads to millisieverts: |
1 Gray = 100 Rads 15 Rads = .15 Gray .15 Gray = .15 Seiverts .15*1000 = 150 milliseiverts |
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What is responsible for the annual effective dose of radiation doubling over the last 30 years? |
*Increase in the number of CT scans, Fluoroscopic diagnostic tests, and nuclear medicine studies. |
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Radiobiology: |
*The study of the effects of ionizing radiation on living organisms.
*1st effects at level of electron at 10^-13 seconds after exposure. |
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Direct effects of ionizing radiation: |
*The initial ionizing radiation occurs on that molecule.
*1/3 of radiation on humans is direct |
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Indirect effects of ionizing radiation: |
*The initial ionizing radiation occurs on a noncritical molecule, such as water, and the energy of ionization is transferred to the target molecule.
*The body is 80% water, so radiation on humans is mostly indirect. (2/3) |
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What is threshold dose? |
*The minimum dose of radiation that produces a detectable biological effect. |
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What is a Deterministic Effect? |
*Above a the threshold dose, severity of harm also increases with dose.
*Example: Radiation induced Cataracts |
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What is Stochastic Effect? |
*As cells are irradiated, the probability of cancer increases with dose, but the severity of cancer is not dose related.
*The severity of damage is not dose related.
*example: cancer |
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What stage of mitosis can chromosomal damage be evaluated? |
*Metaphase
*Most sensitive in M and G2 phase.
*Resistant in late S phase |
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What are some chromosome aberrations caused by radiation injury? |
*Deletion *Duplication *Inversion *Trisomy |
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Law of Bergonie and Tribondeau: |
*Radiosensitivity is a function of metabolic state of the tissue being irradiated.
*stem cells are most radiosensitive
*more mature cells are less radiosensitive |
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Biological Effects of Radiation: |
100-1000: Damage to blood cells. ex: 1st degree burn 1000-3000: Damage to small intestine. ex: skin tissue death 3000-5000: Damage to PNS ex: Death within hours |
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True or False:
There is such thing as a "safe dose" of radiation. |
False |
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What is radiation therapy? |
*The art of using ionizing radiation to destroy malignant tumors while being able to minimize damage to normal tissues.
1. Cure cancer 2. Reduce symptoms |
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What is fractioning of x-ray dose? |
*Breaking up the x-ray dose into multiple small doses, which allows time for cells in normal tissue to repair. |
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Mucositis: |
*The most common complication of cancer treatment. *Inflammation and ulcerative lesions of the mouth and oropharynx. *More common in younger patients. |
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Candidiasis: |
*Colonization of yeast on damaged tissue from radiation. *Pseudomembranous: wipes away *Chronic Hyperplastic: Leukoplakia, don't wipe *Can be caused by hyposalivation. |
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Salivary Gland Dysfunction: |
*Radiation causes irreversible harm to salivary gland cells. *Thick and Sticky saliva *Permanent damage after 6000 cGy |
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Signs and Symtoms of Xerostomia: |
*Sticky, dry feeling mouth *Thick, stringy saliva *Burning sensation *Difficulty chewing, swallowing, talking |
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Xerostomia Treatment: |
*Radioprotectant Medication: Amifostine *Saliva Substitute: Hyetellose, Hyprolose *Saliva Stimulator: Pilocarpine *Patients should visit dentist 2 weeks prior to starting radiation treatment. |
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What is radiation caries? |
*Tooth decay that results from radiation-induced xerostomia. |
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Osteoradionecrosis: |
*An inflammatory condition of bone that occurs after bone has been exposed to radiation to the head and neck. *The most serious complication of oral cancer patient. |
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Radiation effects on embryo: |
*After 1st few days of implantation can cause miscarriage. *Morula or Blastocyst stage can prevent normal development of embryo. *3-8 weeks: Congenital malformation, miscarriage. *Fetal growth stage, can cause birth defects. *9 weeks-birth: Mental retardation, stunting of growth. |
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What is a cathode?
(x-ray tube component) |
*negative terminal of the x-ray tube and serves as a source of electrons. |
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What is a filament?
(x-ray tube component) |
*Tightly wound helix of tungsten connected to 2 circuits. It is where the electrons are emitted. -1 circuit heats the filament -1 circuit provides voltage to accelerate electrons. |
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What is the tube current? |
*The current flowing through the wires controlling the temperature of the filament. *Determines the quantity of electrons available. 5 mA = 1x electrons 10 mA = 2x electrons 20 mA = 4x electrons |
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What is thermionic emission? |
*The heating of a filament from an electric current to a point where electrons are boiled off. |
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What is the focusing cup?
(x-ray tube component) |
*Negatively charged, curved block of molybdenum that houses the filaments. *Reflects the electron stream towards the anode. |
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What is the electromotive force? |
When kilovoltage is applied by a step-up transformer and the electrons are accelerated from the cathode to the target anode at high speeds. |
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What is the anode? |
*The positively charged collector plate that serves as a source for the x-rays. -contains tungsten -stationary -rotating |
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What is the focal spot? |
*Tungsten is material of choice for target -high atomic number, high MP, low vapor P -1% energy converts into x-rays (sharper image)
*Larger angle of focal spot = larger focal spot |
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What is the copper stem?
(x-ray tube component) |
*Dissipates the heat to the surrounding gas or oil of the tube.
*without, target would pit or melt. |
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What is the vacuum tube?
(x-ray tube component) |
*Housing of the anode and cathode |
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What is Bremsstrahlung X-ray Production? |
*High speed electrons are slowed down and bent off course by the positive pull of the nucleus. The kinetic energy lost is converted into an x-ray.
*Continuous spectrum |
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What is Characteristic or Line X-ray Production? |
*High speed electrons hits and dislodges a K-shell electron. Another x-ray in an outer shell quickly fills the void and an x-ray is emitted.
*Characteristic radiation does not produce an image.
*Sharp peak spectrum |
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What is the focal-object distance? (FOD) |
*measured from the focal spot on tube housing, to the end of the position indicating device (PID). |
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Conversions of Impulses --> seconds:
(Control panel selects exposure time) |
*1 Impulse = 1/60 second
*30 impulses = 1/2 second
*16 impulses = 4/15 second |
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What is the proper operator position for x-rays. |
*6 feet away from the tube head |
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Beam Quality: |
*Controlling factor = kilovoltage *Shorter wavelength = Greater energy |
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Size and Shape of Beam: |
*Collimator: 1/16 inch lead diaphragm directs the primary beam at the area desired.
*Federal regulation requires a diameter no bigger than 7 cm, or 2.75 in. |
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True or False:
Rectangular collimator's decrease the amount of excess radiation. |
True
*Can reduce the amount of exposure by 60% compared to circular collimators. |
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What is scattered radiation? |
*Primary radiation with altered energy deflected from its original direction. |
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What is Remnant Radiation? |
*The part of the beam that penetrates an object and is available to react with the image receptor to provide diagnostic image. (primary + secondary radiation) |
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What is attenuation? |
*The loss of energy from an x-ray beam because of its interaction with matter.
*>90% of dental exposures are attenuated. |
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What is X-ray Intensity? |
*The rate that energy is propagated through an area perpendicular to the beam.
I = Quantity / Unit Time |
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What effect predominates in the diagnostic range? |
*The Compton Effect
*The number of interactions is higher in dense tissue than in soft tissue. |
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True or False:
A thicker object attenuates more. |
True |
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True or False:
A higher density object attenuates more. |
True |
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Radiographic Images are dependent on.... |
1. Object thickness 2. Object density 3. Beam energy (kV) |
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What are sources of natural radiation? |
*Sun and Stars send steady amount like "rain" falling down. *Elements in the earth crust *Radon
*Differences in elevation, atmosphere condition, etc changes the amount of natural radiation we receive. |
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What is Radon? |
*Natural source of radiation. *Gas from decaying Uranium. *Can leak into homes and accumulate. *May contribute to 10,000-20,000 lung cancer deaths per year. |
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True or False:
Since 1980, Americans are exposed to 7x as much ionizing radiation. |
True
*largest increase is from CT scans |
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What is the goal of dental radiography? |
*To obtain diagnostic information while keeping the exposure to the patient and dental staff to a minimum level. |
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What is Effective Dose Equivalent? |
*Estimates the risk in humans which allows the risk from exposure to one region of the body to be compared with the risk of exposure to another region.
*Unit = Sv |
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What is Background Equivalent Radiation Time? (BERT) |
*Radiation unit to the public compared to natural background radiation.
*Unit = days
*Example: 1 Panoramic Radiograph = 1-3 days |
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What does the EPA regulate? |
*Radon |
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What does the NRC regulate? |
*Nuclear plants *Transportation and storage of radioactive material. |
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What does the FDA regulate? |
*Food safety *Tobacco *Pharmaceuticals *Medical devices *Cosmetics |
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What does the NCRP regulate? |
*Recommendations on radiation protection and measurement. |
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What are the objectives of radiation protection? |
*To prevent clinically significant radiation deterministic effects, and to limit stochastic effects to a reasonable level. |
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Who is an occupational exposed person? |
*A dentist or dental assistant is an example. Individuals who perform diagnostic and therapeutic procedures, and are exposed to ionizing radiation. |
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Who in a dental office is "occasionally exposed"? |
Examples: *Cleaning workers *Front desk staff |
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What is the source for radiation standards in Florida? |
*The bureau of radiation control -1 of 4 branches of the division of environmental health. -Perform inspections of machines and licenses. -5 Regulatory programs |
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What does the NCRP recommend? |
*Benefit of exposure to ionizing radiation outweighs its risk. *They created all the guidelines for radiology and imaging professionals in the US. |
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What is BEIR VII? |
*Biologic Effects of Ionizing Radiation *Report focusing on health effects of low LET ionizing radiation. *LET is less destructive *Examples of LET = X-rays and Y-rays |
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What are the 3 Principles of Protection for radiation exposure? |
1. Time: less time near source
2. Distance: Greater distance from source
3. Shielding: Behind shield from source |
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What is the safe operator distance away from exposing radiographs? |
*6 feet (4x more radiation if standing only 3 feet away)
*90-135 degrees away from central beam. |
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How is operator protection regulated? |
*An operator may not hold the patient or receptor during exposure.
*An operator may not hold tube or PID during exposure. |
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Where should an operator be standing for a panoramic radiograph? |
*Behind a protective barrier 4 feet from tube head. |
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What is the annual occupational dose of adults? |
5000 mrems
*Dental workers are usually 70% below the monitoring dose. |
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What is the annual occupational dose for pregnant operators? |
500 mrems |
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What is the limit for radiation levels in controlled areas? |
*The limit is no radiation workers can receive more than 20 mSv / year. |
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What is the limit for radiation levels in uncontrolled areas? |
*The limit is no person can receive more than 1 mSv / year. |
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Rectangular Collimation: |
*5x less radiation dose than circular. *Should be used for periapical and bitewing radiographs. |
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What is the purpose of Aluminum filtration? |
*Absorbs the low energy photons. *Low energy photons are more easily absorbed by soft tissues. *Most modern x-ray tubes come with 2.5 mm thick aluminum filter. |
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Protective measures for patients: |
*Paralleling techniques, giving more accurate radiographic images. (film holders ↓ retake by 50%) *Selecting appropriate exposure factors (kV, mA, Time) *Receptors requiring less exposure time. *Set mA to highest setting, and adjust time appropriately. |
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Advantages of digital imaging: |
*Reduces radiation exposure by up to 90% for D speed film. *60% for E speed film. |
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When is shielding with thyroid collar indicated? |
*Intraoral dental examinations
*Contraindicated for Panoramic X-rays because it will interfere with the image. |
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How should you handle a declared pregnant patient? |
*A radiograph may be needed for treatments that may cause harm to the fetus. *Practice ALARA (as low as reasonable acheivable) |
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What % of dentists use digital imaging? |
*40%
(60% of non-users show no interest) |
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Requirements of a receptor: |
*Responsive to differential absorption of x-rays. *Require relatively low radiation exposure. *Produce real time/latent image. *Reproduce anatomically accurate images. *Be manufactured in specific sizes. |
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What type of receptor is used for intraoral and occlusal radiographs? |
*Direct exposure film |
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*What type of receptor is used for panoramic and cephalometric radiographs? |
*Screen film |
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What are the 2 types of x-ray film? |
1. Screen film emulsion
2. Direct exposure emulsion |
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Screen Film: |
*Low sensitivity to x-rays, and is actually more sensitive to visible light. *Almost all conventional radiographs require the production of light by the interaction of x-rays with intensifying screens. (95%) *5% exposure due to ionizing radiation. |
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What is an Intensifying Screen? |
*Sheets of luminescent phosphor crystals mounted on a plastic base. (consists of fluorescent material) *x-rays absorbed are stimulated to give off light *The screen amplifies or intensifies the effect of x-rays. **Reduces radiation exposure needed to produce a radiograph. |
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_____________ refers to the stimulated emission of light by certain materials. |
*Luminescence |
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_____________ is the term used to describe the ability of certain inorganic phosphors to emit light instantaneously when excited by x-rays. |
*Fluorescence |
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What is phosphorescence? |
*If the light emission is delayed or continued after the radiation exposure
*Glow in the dark toys |
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Direct Exposure Film: |
*latent image produced by interaction of silver halide crystals directly by x-rays. *exclusive to intraoral radiographs *light and heat sensitive *must be processed in a darkroom |
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What is the purpose of the lead foil in the oral film packaging? |
*Adds rigidity *Absorbs primary x-rays *Prevents backscatter from entering the package. |
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Significance of identification dot |
*Helps orient the radiograph. *Convexity is oriented toward the source of radiation. *Helps orient whether the film is from the patients right or left side. |
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Intraoral receptor sizes: |
*0-4+
*0: smallest *4+: film only, and achieved with phosphor plates. |
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Film speed: |
*C, D, E, F
*Speed groups represent a factor of 2x
*E is twice as fast as D *E requires 1/2 the radiation exposure as D
*D is used by 70% of dentists still!!! |
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What is film speed affected by? |
1. Thickness of silver emulsion
2. Size of the silver grains
3. Single or double-sided emulsion |
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The film's _________ is the visible difference between adjacent densities and is displayed as black to white, and shades of gray. |
*Contrast |
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Radiolucency: |
*Represents low atomic density and decreased thickness.
*Dental Caries, Pulp chamber, PA cyst |
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Radiopacity: |
*Object with high atomic dense or thick object that does not allow the penetration of x-rays.
*Enamel, Bone, Alloy, Restorations
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Density Explained: (sort of) |
Toe: No density Shoulder: Maximum density Latitude (film gamma): Slope of contrast |
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What happens with too little exposure? |
The processed image is to light |
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What happens with too high exposure? |
The image is too dark |
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Rule 64E-5.502(1)(a)(3):
(Technique Chart) |
*Florida code requires registrants with radiation machines used in the healing arts to have a chart specifying techniques and procedures for all examinations performed by that system. |
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Steps in processing of film. |
1. Developing -5 minutes @ 68 degrees -AgBr --> Ag 2. Fixing -10 minutes -Stops developing (removes AgBr) 3. Wash -30 minutes -removes chemical residue 4. Dry -Hardens emulsion |
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Management of fixer solution: |
*can bleach clothing *Contains metallic silver and cannot be placed in municipal water.
*note: lead backing can not be disposed in water either. |
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How long is film "safe" under a safe light in a dark room? |
2-3 minutes |
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What is a pixel? |
*Picture element *Smallest unit of a picture |
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*What is a voxel? |
*A 3D picture element |
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1 Byte = ___ Bits |
*8
*Provides 256 shades of gray |
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How many bits in a CBCT scanner? |
*14 bits
*16,384 shades of gray |
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How many pixels are required for the detection of fine detail? |
5 pixels/mm |
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How is spacial resolution measured? |
*Line pairs / mm
*↑ lp/mm = greater resolution |
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Advantages of Digital Imaging: |
*Image enhancement *Brightness and Contrast *Lots more! |
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What is DICOM? |
*Digital Imaging and Communication in Medicine:
*Standard for handling, storing, printing, and transmitting medical imaging.
*Exchange of images between 2 medical entities. |
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What are the 2 types of solid state detectors? |
1. Charge-Coupled Device (CCD)
2. Complementary Metal Oxide Semiconductor (CMOS) |
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Solid State Detector: |
*Semiconductors mounted on a silicon chip. *The chip converts x-ray energy into digital signal *Digital signal sent to computer for reconstruction of image. |
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Cons of Solid State Detectors: |
*Bulky *Imaging area less than film (up to 30%) *Cost *Less resolution than film |
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Photstimulable Storage Phosphor (PSP): |
*Exposed x-rays store energy in phosphor as a latent image or phosphorescence. *Latent image converted to digital by scanning with laser light.
*Bright lights erase the memory *Plates can be reused. |
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__________ __________ is an unwanted appearance of the image that has been produced by an operator, mechanical, or other artificial means. |
*Radiographic Artifact
*Caused by error in processing, image acquisition, or handling. |
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Causes for too light an image: |
*Processing errors: -Underdevelopment -Low Temperature -Short Time -Excessive Fixation *Exposure errors: -Insufficient MAS (time) |
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Causes for too dark an image: |
*Processing errors: -Overdevelopment -Accidental exposure to light -Improper safelight *Exposure errors: -Excessive MAS (time) |
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Examples of Processing Errors: |
*Fingerprints on film *Static Electricity (cold climates) *Fixer Stain *Light leak *SP plates overlap |
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Examples of Operator Errors: |
*SP plate placed backwards in mouth and magnet shows *Horizontal overlap *Elongation (vertical angulation small) *Foreshortening (vertical angulation large) |
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__________ is an invasion by and multiplication of pathogenic microorganisms in a bodily part or tissue, which may produce subsequent tissue injury and progress to overt disease through a variety of cellular or toxic mechanisms. |
*Infection |
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___________ ___________ is an approach to infection control to treat all human blood and certain human body fluids as if they were known be to infected with HIV, HBLV, an other blood-borne pathogens. |
*Universal Precautions |
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___________ ___________ integrates and expands the elements of universal precautions into a standard of care designed to protect Health Care personnel and patients from pathogens that can be spread by blood or any other body fluid, excretion, or secretion. |
*Standard Precaution
(new term) |
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True or False:
Saliva is a potentially infectious material in dental infection control. |
True |
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What are the elements of standard precautions? |
*hand washing *gloves, mask, eye protection, gowns *patient care equipment *environmental surfaces *injury protection |
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True or False:
Hands are the most common mode of pathogen transmission, and hand hygiene is considered the most critical measure for reducing the risk of transmitting organisms to patients and health care professionals. |
True |
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______-________ ________ are those instruments that get in contact with mucous membranes but do not penetrate soft tissue. |
*Semi-Critical Instruments
Example: Mirror, Hand Pieces |
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_________ _________ are those instruments that penetrate or contact bone, the blood stream, or other normally sterile tissues of the mouth. |
*Critical Instruments
Example: Surgical Instruments, Scalers |
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True or False:
X-ray tube heads are considered a Non-Critical Instrument or Device. |
True
(Instruments that get in contact with intact skin) |
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General cleaning recommendations for radiology: |
*X-ray tube heads *Exposure button *Time selector and on/off switch *Mouse and Keyboard |
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What is EPHI? |
Electronic Protected Health Information
*Any information created, maintained,and transmitted in electronic form. *HIPAA governs the EPHI. |
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What are the goals of HIPAA? |
*Confidentiality *Integrity *Availability |
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HIPAA notice of privacy practice: |
*Notify all patients of: -Ways you will use their personal health information. -Their rights under HIPAA -Health care center's responsibilities -Must be signed by all patients, new and established. |
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What is the quality assurance plan for radiology? |
*A plan to ensure optimal and consistent operation of each component in the imaging chain with minimum exposure to patient and personnel. -regularly test equipment -increase quality of radiographs -quality of administration and techniques |
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Benefits of Quality Control: |
*Improved diagnosis *Reduce radiation exposure to patient *Reduce retakes *Reliable equipment *Time savings *Cost savings |
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Rating Quality Basis: |
Excellent: No errors
Diagnostic Acceptable: Some errors, but does not detract from diagnostic utility of radiograph.
Unacceptable: Errors and radiograph is unusable. |
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Digital Equipment Maintenance: |
*Scanners should be lubricated regularly. *Clean CCD/CMOS detectors regularly. *Test and calibrate monitors regularly. (SMPTE RP-133 or AAPM TG-18 are suitable) |
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True or False:
SMPTE Test Patterns, 5% and 95% test patterns should be visibly and distinctly different than 0% and 100% areas. |
True
White = 100% Black = 0% |
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_____-_______ _______ is the lateral, vertical plane drawn through the patient's midline. |
*Mid-Sagittal Plane |
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_________ _________ __________ is the anthropologic plane from orbitales (inferior border of orbital cavity) to the Porions (superior border of external auditory meatus). |
*Frankfort Horizontal Plane |
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_________ _________ is a soft tissue line from the wing of the nose to the tragus of the ear. |
*Alatragus Line |
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_________ _________ is a soft tissue line from the outer canthus of the eye to the central portion of the external auditory meatus. |
*Canthomeatal Line |
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Type of Intraoral Radiographs:
(3) |
1. Periapical 2. Occlusal 3. Bitewings |
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What are Periapical Radiographs used for? |
*Show all of tooth with surrounding bone. *Show full length of root and 2mm of periapical bone. *With pathology, the entire lesion should be captured with surrounding normal bone. |
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What are Bitewing Radiographs used for? |
*Also called interproximal radiographs *Shows crowns and alveolar crests.
(The x-ray tube should be angled 0-10 degrees to project the beam parallel to the occlusal plane) (The contacts of MX molars are often more anteriorly angled than MN molars) |
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What is the head position for an occlusal radiograph of the maxillary arch? |
*Occlusal Plane should be parallel to the floor.
(patient bites on plate) |
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What is the head position for an occlusal radiograph of the mandibular arch? |
*Occlusal Plane should be perpendicular to the floor.
(patient bites on plate) |
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What is horizontal angulation? |
*The central ray is directed through the contact points, perpendicular to a line drawn tangent to the lingual surfaces of the teeth. |
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What is vertical angulation?
(paralleling technique) |
*Receptor is placed intraorally parallel to the long axis of the teeth. *The central ray is directed at right angles to the teeth. *Special receptor holders help align everything.
*To achieve parallelism, the receptor is placed further from the teeth. |
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-8 inch source to object distance -1/2 inch object to receptor distance
What is the magnification? |
*6.7% |
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-12 inch source to object distance -1 inch object to receptor distance
What is the magnification? |
*9% |
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-16 inch source to object distance -1 inch object to receptor distance
What is the magnification? |
6.7% |
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What are the advantages of paralleling technique? |
*Minimize geometric distortion. *True anatomic relationships *Simplified beam alignment *Standardized receptor placement *Head positioning not critical. -MX, occlusal plane parallel to floor -MN, head slightly tilted back |
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Bisecting angles technique: |
*1904 *Cieszynski's Rule of Isometry -2 triangles are equal when they have a common side and 2 equal angles. *Long axis of tooth will form 2 legs of a triangle. *Useful when paralleling technique is not possible due to anatomic variations. *Place receptor as close to lingual surfaces of teeth as possible. |
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What are advantages to bisecting angles technique? |
*No film holder needed *No anatomic restrictions *More comfortable for patient |
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What are disadvantages to bisecting angles technique? |
*Anatomic inaccuracies. -Example: different angle needed for each root of multirooted tooth. *As vertical angulation increases, objects on the same plane will be projected at different levels. *Distortion caused by non-parallel object/receptor. *No aligning device (prone to mistakes) *Head Position Important! -MX: Occlusal plane parallel to floor -MN: Head slightly tilted back |
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Angulation Guidelines for Bisecting-Angles Technique: |
Maxilla: Incisors ↑ degrees, Molars ↓ degrees Incisors > Molars
Mandible Incisors ↓ degrees, Molars ↑ degrees Incisors < Molars |
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True or False:
Bitewings are the image of choice for detection of interproximal caries. |
*True
-can be use receptor vertical or horizontal -can do in premolor and molar area |
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True or False:
In anterior bitewings, the receptor is always oriented vertical. |
*True
-Done in centrals or canine areas -Receptor ALWAYS vertical in anterior bitewings. |
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Radiographic Examination of Children: |
*Reduce Exposure (lead aprons, thyroid collars, fast receptors)
*Use minimal number of receptors to achieve diagnostic information. |
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Radiographic Examination of Edentulous Patients: |
*Panoramic X-ray is most convenient. *Reduce exposure to 25% less than what is used for dentulous ridge. |
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Dealing with the tongue for radiography: |
*There is room for sensor if the patient relaxes the tongue. (mylohyoid muscle) *Angle sensor to the lingual, medially toward the tongue itself. (less resistance from tongue in this position) |
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Effective tips to deal with patients with a strong gag reflex: |
*Breath deeply in and out of nose. -nasal decongestant before treatment *Table salt on tip of the tongue. *Patient hold ice bags in each hand as a distraction. *Patient life one foot and concentrate on it for distraction. *Patient hums a song *Topical anesthesia |
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Radiographic precautions that are important for pregnant women: |
*Use faster film *Paralleling technique *Rectangular Collimation *Use of lead apron or thryoid collar
(full mouth series, <1 mrem) (natural radiation in 9 months, 75 mrem) |
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Steps for Exposure: |
1. Prepare unit 2. Wash hands 3. Position tube head 4. Position receptor 5. Position x-ray tube 6. Make exposure |
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Criteria for quality of radiograph: |
*Least possible distortion
*Optimal density and contrast |
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Components of XCP Instrument: |
A: Aiming Ring B: Indicator Arm/Connector C: Receptor holder/Biteblock |
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What area of the mouth is the red biteblock used? |
*Anterior (always vertical)
*Posterior (horizontal or vertical) |
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What area of the mouth and what application is the yellow biteblock used? |
*Posterior *Periapical |
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What area of the mouth and what application is the blue biteblock used? |
*Anterior *Periapical |
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What is the green biteblock used for? |
*Endo |
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True or False:
Increasing the film-object distance makes it easier to get appropriate parallelism. |
True |
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True or False:
The ring of the XCP instrument should be as close to the skin as possible. |
True |
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True or False:
The PID should be equidistance from the ring and within 1/4" of the ring. |
True |
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Why are posterior bitewings made? |
*Interproximal Caries Detection *Marginal caries detection on previously restored teeth. *Incipient alveolar bone loss |
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Full Mouth Series: |
Anterior PA: #1 size, oriented vertically -centered on contacts -MX: R and L centrals/laterals. R and L canines -MN: centrals, R and L canines
Posterior PA: #2 size, universal oriented horizontally.
Premolar PA: anterior edge includes 1/2 of canines
Molar PA: Anterior edge includes 1/2 of 2nd Premolar |
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______________ is transmission of radiological patient images for the purpose of sharing studies with other radiologists and physicians. |
*Teleradiology
(improves patient care by networking between professionals) |
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Mounting: |
*The patients right side is placed on the left, just like the patient were face to face. *Be sure there is a name label. |
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Nasal Fossae Radiographically: |
*Eliptical radiolucency separated by a vertical radiopaque nasal septum and oblique nasal floor. |
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Anterior Nasal Spine Radiographically: |
*Radiopaque, V-shaped projection from the nasal floor in the midline. |
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Nasopalatine/Incisive Foramen Radiographically: |
*Radiolucent round or oval shadow in the midline behind the MX central incisors. |
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True or False:
A shadow from the soft-tissue of the nose can sometimes be superimposed over the anterior teeth in a radiograph. |
*True |
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True or False:
The maxillary sinus and the nasal floor often create an inverted Y appearance on a radiograph. |
*True
(Located between the lateral incisor and the canine) |
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What is the Lateral Fossa? |
*A radiolucency from a depression above and posterior to the lateral incisors. To rule out pathology look for intact lamina dura surrounding the adjacent teeth. |
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Where is the nasolabial fold located on a radiograph? |
*Across the canine and premolar region. |
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Where is the maxillary sinus located on a radiograph? |
*Between canine and tuberosity posteriorly. |
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What is Pneumatization? |
*Expansion of the sinus wall into surrounding bone, usually in areas where the teeth have been prematurely lost prematurely. *Increases with age |
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Malar Process of Zygoma radiographic appearance: |
Well-defined, U shaped radiopaque band superimposed over apices of the molars. |
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_________ represents the relative degree of darkening of an x-ray exposure and the density of the film or image. |
*Density
(The optimal density range in radiography is 0.3, very light, to 2.0, very dark) |
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What is the Hurter and Driffield Curve? |
*Represents the quantitative relationship between the x-ray exposure and the density of a film. |
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________ refers to high film density, which appears in a range from dark gray to black. |
*Radiolucent
-An object that easily permits penetration of x-rays due to reduce atomic density or decreased thickness. -Air is the most radiolucent substance. |
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________ refers to an area of low film density, which appears in a range from light gray to white. |
*Radiopaque
-An object does not allow penetration of x-rays due to high atomic density or increased thickness. |
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________ is the visible difference in densities between light and dark regions on a radiograph. |
*Contrast
-The greater the density difference, the greater or higher the contrast. -C=D1-D2 |
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True or False:
Low kVp leads to low penetration, high contrast, and good caries detection. |
True |
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True or False:
High kVp leads to high penetration, low contrast, and good for bone deformation. |
True |
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_________ is the measurement of the range of exposures recorded as a series of distinguishable densities. |
*Latitude
-Wide latitude --> Long scale contrast -Narrow latitude --> Short scale contrast |
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_________ is the uneven densities on a processed radiograph. |
*Mottle
-The graininess or noise "mottle" is a result of the size of silver halide crystals. |
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The density of a processed film is determined by: |
1. The amount of X-rays emitted from the source. 2. The amount of X-rays reaching the object. 3. The amount of X-rays transmitted through the object. 4. The amount of X-rays the reach the film or receptor. 5. The type of film used 6. Chemical processing |
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Density Controlling Factor: |
*MAS
*Change exposure factors without altering the quantity of x-rays produced maintains a constant density. -5mA x 2sec = 10 MAS -10mA x 1sec = 10 MAS |
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What causes film fog? |
*Scattered radiation *Improper safelight *Prolonged development time *High processing temperature *Improper storage of film *Increased kilovoltage |
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______ ______ reduces contrast and makes the whole film darker. This makes it harder to see the density differences (contrast), making the film undiagnostic. |
*Film Fog |
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Achieving Optimal Radiograph: |
*Radiation source as small as possible. *The source-tooth distance should be large. *The tooth-film distance should be small. *The tooth and film should be parallel *The x-ray beam should be perpendicular to tooth and film. |
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_________ measures how well a boundary between 2 areas of differing densities is revealed. |
*Sharpness
Affected by... -Edge gradient, source-object-film distance -Motion -Materials used |
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_________ _________ measures how well a radiograph is able to reveal separate objects that are close together. |
*Spacial Resolution |
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True or False:
Diagnostically acceptable images require high sharpness and resolution. |
*True |
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Penumbra vs. Umbra: |
*Penumbra: (edge gradient) is the zone of sharpness along the edge of images in a radiograph.
*Umbra: Is the zone of absolute shadow. |
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*Benson Line Focus Principle: |
*Smaller focal spot results in smaller Penumbra, and a sharper image. *Decrease anode angle will decrease focal spot. *Increase anode angle will increase focal spot. |
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What affects magnification? |
*Focal spot to receptor distance *Object to receptor distance *Focal spot to object distance |
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A _________ distance between the focal spot and the object results in an _________ sharpness and _________ magnification. |
*Larger, Increased, Less
(image size distortion) |
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What affects image shape? |
*Receptor to object relationship -Place teeth and receptor parallel *Beam alignment -CR perpendicular to teeth/receptor |
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True or False:
Insufficient vertical angulation causes elongation. |
*True
*low angle = elongation *Use paralleling technique |
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True or False
Excessive vertical angulation causes foreshortening. |
*True
*high angle = foreshortening *Use paralleling technique |
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True or False:
The goal of aligning radiographs should produce no overlaps. |
True |
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Clinically acceptable overlap is less than _____ % of the entire enamel thickness. |
*50% |
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___________ is a technique in which two radiographs are taken with exactly the same geometry except that the horizontal angulation is shifted the distance equal to the distance between the two pupils of the eye. |
*Stereography
(Very difficult and rarely used) |
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Clark's method for locating an object: |
*SLOB (2 radiographs taken)
"Same Lingual, Opposite Buccal"
*Lingual if object moves in same direction as tube shift. *Buccal if object moves in opposite direction as tube shift. |
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True or False:
The lamina dura is an example of the Peripheral Eggshell Effect. |
*True
-Rounded things are thicker in the periphery. |
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Advantages of panoramic radiograph: |
*Increased area of coverage *Reduced radiation dose *Ease of application *Good for patients who can't open their mouth *Reduced exam time *Good for patient education |
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Disadvantages of panoramic radiograph: |
*Decreased image quality -increased object to receptor distance *Overlapped proximal surfaces of premolars *Superimposition of cervical spine |
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_________ _________ is a diagnostic imaging modality which uses x-rays to image individual cross-sectional slices through the body. |
*Computer Tomography (CT) |
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True or False:
Panoramic radiographs come from a much narrower beam than the round-collimated beam used in intraoral radiography. |
*True |
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What is the width of maxillofacial tomographic slices? |
*1.5-6 mm |
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True or False:
In panoramic radiographs, objects farther from the center of rotation are diminished. |
*True |
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True or False:
In panoramic radiographs, objects closer to the center of rotation are magnified. |
True |
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What are the 3 major axes of panoramic radiographs? |
1. Anterior-Posterior 2. Vertical 3. Midsagital |
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Panoramic Technique: |
1. Frankfort plane parallel to floor (porion-orbitale) 2. Patient with slight downward gaze 3. Occlusal plane slopes anteriorly downward
Problems: Head tilted too much downward can cause superimposition of hyoid/teeth overlap. Problems: Head tilted upward can put incisors out of focus, and condyles can be off film. Problems: Patient too far back can cause out of focus incisors and wide appearance. Problems: Too far forward can caused out focus anterior teeth and spine superimposed with ramus. (missing anterior teeth!) |
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Criteria for acceptable panoramic image: |
*Covers TMJ and chin *Good symmetry *Occlusal plane 10 degrees downward *No overlap of cervical spine on mandibular anterior teeth. |
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In panoramic x-ray:
What causes anterior teeth to be blurry, small, and narrow, with the spine is visible on sides of film? |
*Patient too far forward. |
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In panoramic x-ray:
What causes anterior teeth to be blurry and wide, with ghosting of mandible and spine? |
*Patient too far back. |
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In panoramic x-ray:
What causes roots of lower incisors to be blurry, the mandible to be in a "V" shape, and spine forms arch like "gazebo"? |
*Patients chin is tipped too far down |
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In panoramic x-ray:
What causes upper incisors to be blurry, the hard palate to be superimposed on roots, and the mandible to be broad and flat? |
*Patients chin is tipped too far up |
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In panoramic x-ray:
What causes the teeth to be wider on one side than the other? |
*Patients head is twisted in the machine |
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In panoramic x-ray:
What causes the condyles to be at unequal heights and the nasal structures to be distorted? |
*Patients head rotated, or tipped, in the machine |
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True or False:
When interpreting a panoramic x-ray, you should examine the teeth first. |
*False
(You should examine the maxilla, mandible, zygoma, soft tissue, and air spaces, but you should save the teeth for last) |
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What are the 4 components of CBCT image production? |
1. X-ray generation 2. Image detection 3. Image reconstruction 4. Image display |
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True or False:
The preferred CBCT exposure is done with a pulsing x-ray beam. |
*True
(This means actual exposure time is less than the scanning time) |
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Image acquisition in a CBCT: |
*Rotation of scanner exceeds 180 degrees *Single images known as "Basis Images" are taken and resemble lateral cephalograms. *The complete series of basis images are known as "Projection Data". |
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What are the 3 planes of image display with a CBCT? |
1. axial 2. sagittal 3. coronal |
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What are the 3 sizes (Field of view) for CBCT scanner? |
1. Large, 16-20cm, and useful for ortho and surgical
2. Medium, 8-15cm, and used for implant planning
3. Small, 4-8cm, specific use like endo |
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CBCT Limitations: |
*Poor soft tissue contrast *May have image artifacts -"beam hardening" = low energy photons absorbed. *Distortion and blurry if patient is not still |
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True or False:
CBCT should be used before implant placement, sinus lift and bone grafting |
*True |
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Radiation dose of CBCT: |
*4-67 times the dose of a 2D panoramic x-ray. (3-74 days of background radiation) *Selection criteria needs to be followed to minimize patient radiation. *Lower dose than conventional medical CT. |
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Requirements for CBCT referral: |
*Referring Dr. name *Address *Phone number
(If prescription is incomplete, the CBCT technician must contact referring dentist) |
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True or False:
It is the responsibility of the practitioner obtaining the CBCT images to interpret the findings of the examination. |
*True
(an imaging report must accompany a CBCT scan) |
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_________ _________ is the ability to distinguish very small differences in tissue density. |
*Contrast Resolution
(High contrast resolution is a CT advantage) |
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_________ _________ is the ability to discriminate between adjacent objects. |
*Spatial Resolution
(Moderate spacial resolution is a CT advantage) |
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What is the primary limitation of CT scans? |
*High radiation dose
*The average person now receives as much man made radiation as natural background radiation annually. |
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________ ________ ________ is a medical imaging technique used in radiology to visualize internal structures of the body in detail. |
*Magnetic Resonance Imaging (MRI)
(does not require ionizing radiation) |
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What are indications for MRI's in dentistry? |
*Neoplastic lesions of the nasopharynx, salivary glands,paranasal sinuses, the orbits, and intracranial structures. *TMJ (cartilaginous disk) *Differentiates between solid and cystic lesions (jaw tumors) |
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Contraindications for MRI: |
*Pacemakers *Cochlear implants *1st trimester of pregnancy *Aneurysm clips |
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___________ is a diagnostic technique to acquire a 2D internal body tissue image by detection of radiation emitted by a radioactive substance administered to the body. |
*Scintigraphy
Dental Application: Osteoblastic activity, TMJ, odontogenic lesions, Ameloblastoma, Malignant neoplasms. |
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Radiography is the _________, and radiology is the __________. |
*Technique, Interpretation |
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True or False:
The ability to optimally view every aspect of a radiographic image is crucial. |
*True |
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True or False:
Inappropriate treatment decisions based on non-diagnostic radiographs will not be defensible in a court of law. |
*True
(A signed and dated radiographic report [interpretation] must be included in all patient records) (All relevant findings must be recorded) |
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What method of analysis of abnormal findings will be used at LECOM SDM? |
*The Systematic (Analytic) Method.
(step by step analysis of all image features) |
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Systematic Image Analysis: |
1. Anatomical landmarks of all 4 quadrants 2. Trabecular pattern 3. Height of interdental bone |
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LESIONS: |
LOCATION EDGE SIZE and SHAPE INTERNAL STRUCTURES OTHER (teeth, lamina dura, PDL space) |
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"Onion skin appearance" |
*Garre's Osteomyelitis *Ewing's Sarcoma |
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"Sunburst appearance and codman's triangle" |
*Osteosarcoma |
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"Ground glass pattern" |
*Fibrous Dysplasia |
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"Cotton wool appearance" |
*Paget's Disease |
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Radiographic "RED FLAGS": |
*Poorly Defined Radiolucency -rapid, irregulary malignancy *Unilateral Widening of PDL Space *Floating Tooth *Cortical Perforation -malignant lesions *"Spiked Roots" -malignant lesions |
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Radiographic Narrative: |
*Age *Gender *Race *Type of dentition *Degree, magnitude, and location of Caries (no individual tooth numbers needed) *Describe defective restorations *Describe bone loss *Describe any lesions *Recommendations (more radiographs, clinical tests, and referrals) |
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True or False:
Radiographic findings must be verified clinically. |
*True
(Radiographic consultation with faculty must be done before odontogenic exam is finalized) |
