DANB RHS Ultimate Review

Radiology is the study of radiation as it’s used in medicine

History Of Radiology

  • Discovered by Wilhelm Conrad Roentgen (German physicist) on November 8, 1895

  • X-rays were referred to as roentgen rays

  • Radiology was referred to as roentgenology

  • Radiographs were referred to as roentgenographs

  • Roentgen was awarded the first Nobel prize in Physics in 1901

  • Otto Walkhoff made the first DENTAL radiograph

  • Dr. C. Edmund Kells is credited with the first practical use of radiographs in dentistry in 1896

    • Suffered from radiation exposure

  • Dental radiology has evolved overtime and new technology continues to improve dental images

Radiation Physics and Biology

  • Everything is composed of energy and matter

    • Atoms are the basic form of matter and they contain energy

    • Energy is the ability to do work

    • Matter is anything that takes space and has form or shape, made of molecules

  • The nucleus is made up of protons and neutrons

    • Protons have positive electrical charges

    • Neutrons has negative or no electrical charges

  • Electrons are small negatively charged particles that have little mass, they orbit the nucleus of the atom

  • Ionization:

    • Ionization is the process by which an atom or molecule acquires a negative or positive charge by gaining or losing electrons to form ions.

    • Producing an ion (an atom that gains or loses an electron and becomes electrically unbalanced) is a process called ionization

    • In the context of dental radiology, ionization occurs when X-rays or other forms of ionizing radiation interact with tissue. This can lead to disruptions in atomic and molecular structures, potentially resulting in biological effects

  • Properties of X-Rays:

    • X-rays are a form of energy that can penetrate matter

    • The Shorter the wavelength, the greater the energy and vice versa

    • Short wavelengths with high frequency = more energy

    • Long wavelengths with low frequency = less energy

    • Dental radiographs need short wavelengths or hard radiation — they have high frequency, high energy, and high penetrating power

  • Types of Radiation

    • Primary radiation →made of x-rays that come from the target of x-ray tubes

    • Secondary radiation →x-radiation that is created when the primary beam interacts with matter

    • Scatter radiation →form of secondary radiation that happens when an x-ray beam is deflected from its path when it comes into contact with matter

    Radiation types from x-ray tube

  • Primary radiation:

    • comes from the central beam of x-ray tube

    • has high energy, short wavelength, and travels in a straight line

  • Secondary Radiation

    • Primary x-rays come into contact with matter or strike the patient

    • Waves are longer

    • long = less energy

    • less energy = less diagnostic x-ray

  • Scatter Radiation

    • Defected from its path when it strikes matter

    • Scatters in all directions (hint hint) → DANGEROUS to everyone

    • Reason why operator must stand 6 feet away from the patient or behind a barrier that is thick

  • Leakage Radiation

    • Escapes in all directions from tubehead

    • X-rays must be checked for leakage and can’t be used until problem is addressed

    • Not useful

    • Long wavelengths cause harm only

X-ray anatomy

  • Plugged into wall outlet and when turned on the electrical currents enter the control panel

  • The current travels from the control panel to the tubehead through the electrical wires in the extension arm

  • Current travels through the step-down transformer to the filament to the cathode

  • The Filament circuit uses 3 to 5 V to heat the tungsten filament in the cathode portion of the x-ray tube

  • By heating the filament, the thermionic emission electrons are released

  • When the exposure button is pushed the high voltage circuit is activated

  • The electrons are accelerated across the x-ray tube to the anode

  • When the electrons strike the tungsten target, the kinetic energy is converted to x-ray energy and heat

  • Less than 1% of the energy is converted to x-rays and the remaining is lost as heat

  • Heat is carried away from the copper stem and absorbed by the oil in the tubehead

  • X-rays travel through the uleaded glass window, tubehead seal, and aluminum filter

  • Aluminum filter removes the long wavelengths

  • X-ray beam travels though the collimator

  • The beam then travels down the lead-lined PID and exits at the end of the PID

Dental X-Ray Machine

  • Tubehead:

    • Contains the x-ray tube that produces dental x-rays

    • Made of leaded glass or aluminum to keep the oil in the tubehead and acts as a filter for the x-ray beam

    • The metal body of tubehead is called metal housing filled with insulating oil

    • the x-ray tube is where x-rays are produced

    • Made of glass

    • About 6 inches long and 1 inch in diameter

  • PID

    • Lead lined to aim the x-ray bean to mouth

    • Placed against patients face

    • Cylinder or rectangle

  • Extension Arm

    • Moves

    • important in positioning the tubehead

  • Control panel

    • Contains master switch, indicator light, selector button, and exposure button

Interactions of X-Rays with matter

  • When x-rays come in to contact with matter:

    • No interaction

    • Photoelectric effect →when light shines on a metal, electrons are ejected from the surface of the metal

    • Compton scatter →x-rays are scattered on a material with an x-increase in wavelength

    • Scatters off

Radiolucent and Radiopaque Characteristics

  • Radiolucent structures allow x-rays to pass through them

    • Is dark or black on the radiograph

  • Radiopaque don’t allow x-rays to pass through them

    • appears white or light grey

Characteristics of the X-ray

  • Quality describes the energy or penetrating ability of x-ray beam

  • Quantity refers to the number of x-rays produced

  • Intensity combines quality and quantity →# of photons and energy of each photon

  • The sharpness and detail of the x-ray is determined by the movement, film speed, PID placement, and subject matter

Contrast

  • Contrast of image clearly shows radiopaque white of metal restoration, radiolucent black of air, and many shades of grey between

  • Contrast = difference between shades of grey

  • high kilovoltage produces more penetrating x-rays and lower radiographic contrast

  • 90 kVp (maximum voltage applied) setting requires less exposure time and produced a radiograph that has low contrast

  • 70 kVp requires slightly longer exposure time and produces a radiograph with high contrast

  • Higher kVp penetrates through areas BETTER and radiation does is LOWER

  • BUT a higher kVp will decrease the image contrast

Density

  • Density = overall blackness or darkness of an image

  • The correct density allows the dentist to see black areas (air spaces), white areas (enamel, dentin, and bone)

  • the degree of density is determined by the milliampere seconds (mA) —the amount of electrical current flowing through the x-ray tube

  • mA controls the temperature of the cathode filament →controlling how many electrons are produced

  • the MORE electrons the MORE x-rays emitted →better quality image

  • Intensity →combo of # of photons (mA) and the energy of photons (kV)

Geometric Characteristics

  • Sharpness →detail, resolution, or definition

  • Distortion →disproportion change in size caused by excessive or insufficient vertical angulation

  • Magnification →proportionate enlargement of dental image

Radiation Effects

  • all ionizing radiation is harmful and produced biological changes

  • entire x-ray area is considered to be a hazard area

  • Ionization is the process by which electrons are removed from electrically stable atoms

  • Atoms that lose electrons become positive ions, they are unstable and capable of interacting/damaging other atoms, tissues, or chemicals

  • Critical organs include: skin, thyroid gland, LENSES OF THE EYE (according to danb), and bone marrow

  • The effects of radiation may not become evident for many years after x-ray absorbed →called latent period

  • Radiation exposure has a cumulative effect over lifetime

  • Acute radiation is when a large dose of radiation is absorbed in a short time

  • Chronic radiation is when small amounts of radiation is absorbed repeatedly over a long time

Genetic and Somatic Effects

  • Genetic effects can’t be repaired and can be passed to generations

  • Reproductive cells are harmed and include sperm and ova

  • Somatic effects are not passed to the next generation and the consequence of radiation exposure remains with the person effected

  • Effects cells all over the body

  • USE LEAD APRON AND THYROID COLLAR FOR PROTECTION

Maximum Permissible Dose

  • The MPD is 5000 mrem (5.0) per year

  • Strive for 0

Radiation Safety

  • The effects of exposure increase every time the individual is exposed →called the long-term effect

  • Latent period = the period between direct exposure and the development of biological effects

  • ALARA = As Low As Reasonably Achievable

    • Using the least amount of radiation possible

  • Using x-rays during pregnancy is safe and doesn’t need to be altered

  • Radiation is monitored by a film badge, a pocket dosimeter, or a thermoluminiscent (TLD)

Fast-Speed Film

  • The film speed refers to the amount of radiation required to create the image

  • The size of the silver bromide crystals is the main factor in determining the film speed →the larger the crystals, the faster the film

  • Fast film requires less exposure to produce quality radiographs

  • Fast-speed film is the most effective method of reducing a patient’s exposure to x-rays

  • Fast-speed film is available for both intra and extraoral radiography

Digital Radiography

  • conventional x-ray machine is needed to expose an x-ray

  • digital radiography:

    • quick, less radiation, no chemicals, no processing errors, enhance images, etc.

  • Film is made with an emulsion of silver bromide, silver halide, and silver iodide that is sensitive to radiation

  • Latent Image: the image which is not visible before processing

  • Film Sizes:

    • 0 for child

    • 1 for narrow anterior

    • 2 is adult size

    • 3 is preformed bitewing

    • 4 is occlusal size

  • Film Packet

    • One corner of the film packet is a small raised bump known as the identification dot

    • the black film wrapper protects the film from light

    • the lead foil sheet protects from back-scattered (secondary) radiation

    • the outer layer seals the film packet

    • The white side of the film must face the teeth and tubehead and the raised dot toward incisal/occlusal surface

  • Steps in Film Processing

    • Development

    • Rinsing

    • Fixation

    • Washing

    • Drying

  • Processing Solutions

    • 3 forms: powder, ready-to-use liquid, and liquid concentrate

Intraoral Imaging

  • FMX

    • Contains periapical images and bitewing images

    • has 18-20 images

  • Periapical

    • Entire tooth from occlusal surface or incisal edge to a little over the apex →shows the periapical bone

  • Bitewing

    • Upper and lower teeth in occlusion

    • only crown and small portion of root exposed

Extraoral Imaging

  • Taken when large areas of the skull or jaw must be examined or when patients can’t open their mouths

  • Includes

    • Panoramic (360)

    • Cephalometric projection

    • Computed tomography (CT)

    • TMJ projection

    • Cone beam CT (CBCT)

  • Frankfort Plane: imaginary line from the middle of the ear to just below the eye socket →must be parallel with the floor

  • Midsaggital Plane: Imaginary line the evenly divides the face into right and left halves →must be perpendicular to the floor so that the head is not titled (image distortion)

  • Errors:

    • Ghost images (metal objects that aren’t removed)

    • Lead apron artifact (lead apron too high up and shown on x-ray)