Radiology Exam 2

7 tissues that are considered critical regarding exposure to ionizing radiation

• Thyroid gland

• Bone marrow

• Skin

• The lens of the eye

• Lungs

• Reproductive tissues

Stochastic effects

Non-threshold

• Effects do NOT depend on the magnitude of the absorbed dose

Non-stochastic effects

Threshold

• Effects increase severity with increasing absorbed dose

Background radiation

Natural source of radiation

• Cosmic (external) and terrestrial (internal); 50% of human exposure to radiation

• Radioactive materials in the earth, air, stars, and sun

• Accounts for 50% of human exposure

Maximum permissible dose (MPD)

The upper limit of allowed radiation dose that one may receive without the risk of significant side effects

Density

Degree of blackness

Contrast

Differences in density

Intensity

Quantity of electrons, number of photons

Energy

Quality of the electrons, energy of photons

Magnification

Equal enlargement

Shape distortion

A variation of the true size and shape of an object being radiographed

Radiolucent

Darker/blacker area on X-ray

Radiopague

Lighter/whiter on X-ray

Attenuation

Ability of a substance to absorb x-ray energy and reduction of the strength of a signal

• Weakening of the energy of a beam as it passes through an object

Diagnostic dental image

• Anatomical accuracy

• Adequate coverage of the area

• Visual characteristics (Density/Contrast)

• Minimal geometric characteristics (Un-sharpness, Magnification, Distortion)

Factors that influence Density

Influenced by mA and kVp (mostly mA)

Factors that influence Contrast

Influenced by kVp; the object’s thickness and density of tissues

• Low kVp = High contrast

• High kVp = Low contrast

High contrast

Very distinct blacks and whites

Low contrast

Many shades of gray

Short scale contrast

An image that shows only two densities

• High contrast

Long-scale contrast

An image that exhibits many shades of gray

• Low contrast

Step-wedge

Used in the calibration of the x-ray machine

Three geometric characteristics of the radiographic image

• Un-sharpness

• Magnification

• Distortion

Factors that influence Sharpness

Focal spot

• Smaller focal spot = sharper image

• Larger focal spot = Less sharp image

• Movement: Loss of sharpness occurs if the tube head, the receptor or the patient moves during x-ray exposure

Factors that influence Magnification

Divergent paths of the X-ray beam as they radiate from the focal spot

• Target-receptor distance: Longer PID and target-receptor distance = less magnification

• Object-receptor distance:

• An increase in object-receptor distance = results in more image magnification

Distortion

A variation in the true size and shape of an object being radiographed

• Object-sensor alignment: The object and sensor must be parallel to each other, or there will be distortion

• X-ray beam angulation: The x-ray beam must be directed perpendicular to the tooth and the sensor

Umbra

Shadow

Penumbra

The fuzz, unclear area that surrounds the tooth

Five principles of shadow casting

• Small focal spot

• Long focal-sensor distance

• Short- object sensor distance

• Long axis of tooth is parallel to the sensor

• Central ray is perpendicular to the sensor

ALARA

As Low As Reasonably Achievable

• Try to reduce exposure to radiation as much as possible

Rectangular collimator exposes ___ less tissue than circular collimator

60%

Six ways to protect the patient from excessive radiation during x-ray exposure

• Thyroid collar

• Lead apron

• Image receptor

• Beam alignment devices

• Exposure factor selection

• Proper technique

Operator protection

• Distance: At LEAST 6 feet away

• Position: 90-135 degrees from primary beam

• Shielding: Lead walls, dry wall, plaster steel, cinderblock

Maximum permissible dose

The maximum dose equivalent that a body is permitted to receive within a specific period

Quality Assurance (QA)

The steps taken to ensure consistent, high-quality radiographs, reduce retakes

• Quality Control tests- Physical Testing

• Quality Administration procedures- Management role

Malpractice

Results when dental practitioner is negligent in delivery of care

Negligence

Diagnosis or treatment falls below the standard of care

Standard of care

Quality of care that a prudent practitioner in similar location under similar conditions would provide

Statue of limitations

Time-period when patient may bring a malpractice suit against dental practitioner

Self-determination

Patients have the right to make choices about the care they receive, including refusal

Disclosure

Informing patient

Liability

Being legally accountable for actions or inaction

HIPAA

The HIPPA Privacy establishes strict guidelines to protect patient privacy and control over their health data, ensuring it is handled securely and confidentially

Three possible routes for disease transmission

• Direct contact with pathogens present in saliva, blood, respiration secretion or lesions

• Indirection contact with contaminated objects/instruments

• Direct contact with airborne contaminants/aerosols

Universal/ Standard precaution

Measures that include standard of care designed to protect healthcare personnel and patients from pathogens that can be spread by blood, and other other body fluid, excretion, or secretion

Describe the conditions that must be present for disease transmission to occur

• A susceptible host

• A pathogen with sufficient infectivity and numbers to cause infection

• A portal through which the pathogen may enter the hose