Radiology

Chapter 38Foundations of Radiology,

Radiographic Equipment, and Radiologic Safety

Uses of Dental Radiographs

• Detect dental caries in the early stages• Identify bone loss in the early stages• Locate abnormalities in the surrounding

hard and soft tissues• Evaluate growth and development• Provide information during dental

procedures (ie root canal)• Document a patient’s condition at a

specific time

Properties of Radiographs

• X-rays are a form of energy• X-rays belong to a group classified as

Electromagnetic radiation• Electromagnetic radiation is made up of

photons that travel through space at the speed of light in a straight line with wavelike motion

• Shorter the wavelength the Greater its energy

Dental X-ray Machine

• Tubehead—tightly sealed—contains tube• X-ray tube—in the heart of the system

– Cathode—negative electrode– Anode—positive electrode

• Position Indicator Device (PID)• Extension Arm• Control Panel

– Master Switch and indicator lights– Exposure Button– Milliamperage – Kilovoltage selector

Types of Radiation

• Primary– X-rays that come from the target to the x-ray tube,

(the useful beam)

• Secondary– Created when the primary beam interacts with matter

(less penetrating, not useful)

• Scatter – Form of secondary, that is deflected from path in all

directions (dangerous to all)

• Leakage

Characteristics of Radiograph Beam

• Quality, quantity and intensity of beam

• Determine contrast, density and image detail (good x-ray)

Radiolucent and Radiopaque Characteristics

• Radiolucent– Structures that radiation can pass through

easily (dark)– Such as:

• Radiopaque– Structures that radiation cannot pass through

easily (light)– Such as:

Contrast

• Images appear in a range of shades• Black to white• Ideal?• Higher kVp produces more penetrating

radiograph and lower contrast• 90 kVp requires less exposure time and

produces low contrast on x-ray (more shades of gray

• 70 kVp requires slightly longer exposure and gives high contrast (fewer shades of gray)

Density

• Overall blackness or darkness of a film

• Should enable view of air spaces (black) and enamel, dentin and bone (white) and tissue (gray)

• mAs control amount of time given to the exposure of x-ray

Other factors that Influence Density

• Distance from the x-ray tube to the patient– It changes the exposure setting and will be

light or less dense

• Developing time temperature– Process time too long, will appear dark

• Body size of patient– Very small/thin—requires less rad than

heavier patient

Geometric Characteristics

• Sharpness– Reproduction of fine details, and/or outlines– Such as TV control (fuzzy) referred to as

penumbra– Focal spot size– Film composition– Movement

Geometric cont

• Distoration– Disproportional change in size of images– Too much or too little vertical angulation

• Magnification– Proportional enlargement of radiographic

image

Radiation Effects

• ALL ionizing radiation is harmful• Tissue damage—radiation that is absorbed can

result in chemical changes and biologic damage– Ionization—can cause disruption of cellular

metabolism and permanent damage to living cells and tissue

• Biologic effects—can take many years to become evident– Cumulative effect– tissues can repair some damage,

tissue does not return to their original state

Effects cont.

– Acute and chronic rad exposure• Acute—large does in short period of time• Chronic—small amounts absorbed repeatedly over

long period of time

– Genetic and somatic effects• Genetic- (sperm and ova) passed on to

succeeding generations, genetic mutations• Somatic- (body) not passed on to future

generations

Effects cont.

• Critical Organs– Skin—seen as reddening or erythema

• Thyroid gland—(how do you protect)

• Lens of eye—can cause cataracts

• Bone Marrow--leukemia

Radiation Measurement

• Traditional system or standard system (older system of measurement)– Roentgen (R) radiation absorbed dose (rad)

and roentgen equivalent in human (rem)

• System Internationale (newer system)– Metric equivalent– Coulombs per kilogram (C/kg), gray (Gy), and

sievert (Sv)– UNDERSTAND each system

• Maximum Permissible DoseOccupation persons = 5.0 rem per year

Non-occupation persons = 500 mrem per year

Radiation Safety

• Background radiation—comes from natural sources

• Protective devices– Aluminum filtration ?– Collimator ?– Position Indicator device ?

Safety cont.

• Patient protection– Lead apron and thyroid collar– Fast-speed film– Film-holding devices– Exposure factor– Proper technique

• What does the ADA and FDA state regarding pregnancy and dental radiation?

Safety cont

• Operator protection and monitoring– What are the rules ?

• Never stand in direct path of primary beam• Always stand behind lead barrier or stand at right

angles from beam• Never stand closer than 6 feet from the x-ray unit

Safety

• Equipment monitoring– What are the rules

What is the ALARA concept?

Chapter 39Dental Film and Processing

Radiographs• What is a film holder ?

• Explain some of the few holding systems that are available

Dental Film

• Understand the following– Film composition– Latent image– Film speed

Intraoral Film

• Understand the following– Film packet

• Packet info, wrapper and lead sheet, package positioning, package disposal

– Outer packet• Tube side, label side

– Film sizes• #’s 0, 1, 2, 3, 4 (what is each size used for)

Extraoral film

• Film packaging ?

• Film cassette ?

• Intensifying screen ?

• How and where do you store film ?

• If you were duplicating film what equipment would be needed?

Film Processing

• What are the five steps in processing film

• What are the requirements for a film processing darkroom?

• Know the techniques/steps for Manual and Automatic film processing

Errors

• Fully understand the possible errors that can take place while processing films

• How would you correct or prevent these errors

Chapter 40Legal Issues, Quality

Assurance, and Infection Control

• Quality assurance– Regular testing to detect equipment

malfunctions, planned monitoring and scheduled maintenance

Legal Considerations

• Federal and State regulations ?• Licensure requirements ?• Risk management—polices and

procedures that reduce chance of lawsuits– Key areas

• Patient consent, patient records, liability issues and patient education

• Informed Consent• Liability

Cont

• Patient records

• Patient Refusal

• Patient Education

(Understand all of the above)

Quality Assurance

• What is a quality control test and what does it monitor?

• There is a lot of information under Quality Assurance, make sure that you understand each type and the steps involved

Administrative Quality Control Steps

• Develop and maintain a written description of the quality assurance plan

• Assign specific duties to staff members and ensure that each individual is thoroughly trained

• Maintain records of monitoring and maintenance

• Review the plan periodically and revise if needed

Infection Control

• There is a high risks for cross-contamination

• CDC has guideline for Infection control (make sure you know them)

• There is a checklist for Infection Control during radiographs, be familiar with these steps

ICE

• There are procedures that can be performed for equipment and supplies– Understand these procedures, such as how to

handle film, film packets, holders.

• Procedures during and after exposure must be followed:– What are these procedures; such as drying

exposed film, etc.

Infection Control Steps

• There are several steps to practice during film exposure– Some are common sense and others are not– Read and think about the many ways you can

practice this.• Such as barriers for operatory, washing hands,

how to unwrap an exposed film or how to transport an exposed film

Chapter 41Intraoral Radiography

• Steps to quality radiographs– Placement– Exposure – Processing– = Quality radiographs

Full Mouth Series

• Intra oral films

• What type of x-rays are take in FMX

• Two types of methods for exposing intra oral films

Paralleling Technique

• Five basic rules– Film Placement—cover teeth involved– Film Position—parallel to long axis of tooth– Vertical Angulation—central ray perpendicular

to film and long axis– Horizontal Angulation central ray directed

through contact areas – Central Ray—beam must be centered on the

film

Guidelines for Placement

• There are seven (fill them in below)

• Patient Preparation– Make sure that you read over the procedure

in your book

• Exposure sequence for film placement– Make sure you understand what teeth should

be present in what x-ray

Producing Full Mouth

• There is a whole procedure outline in your book for each tooth/teeth– Be very familiar with each section

Bisecting Technique

• Based on the geometric principle of equally dividing a triangle

• Places film directly against the teeth to be radiographed, so teeth and film are not parallel but are at a right angle

• Film holders are used rather then the XCP

• Understand patient positioning– Beam alignment

Bite Wing Technique

• Shows the crowns and interproximal areas of max and mand teeth and the areas of the crestal bone

• Basic principles– Placed parallel to the crowns of upper and lower– Stabilized when the patient bites on the tab or

holder– Central beam is directed through contacts of

teeth using +10 degrees vertical angulation

Occlusal Technique

• Take an x-ray of entire maxillary or entire mandibular arch at one time

Mounting Radiographs

• You need to be able to recognize anatomic landmarks– If I showed you an x-ray with a Nutrient canal

and Lingual foramen on it, would you be able to tell me that this is a mandibular anterior x-ray????

Guidelines for Mounting

• Handle films by the edges

• Learn normal anatomy

• Label and date film mount before mounting films

• Mount immediately

• Use clean dry hands

• Use order of teeth to distinguish right from left

cont

• Use definite order for mounting

• Mount bite-wings with the curve of Spee upward (makes a smile)

Chapter 42Extraoral and Digital

Radiography• Extraoral—large areas of skull or jaw must

be examined (outside of mouth)

Panoramic—entire dentition and structures on single fillm

Why would they be used?

What type of equipment is used

What would be some errors that could take place

Advantages and Disadvantages

• Field size

• Ease of use

• Patient acceptance

• Less radiation

• Image sharpness

• Focal trough limitations

• Distoration

• Cost of equipment

• Cephalometric films– Takes side view of skull– Used mostly in orthodontics and surgery

Digital Radiography

• Advances in computers have made this the way of the future

• Filmless

• Records images

• What is the basic concept?

• Understand types of digital imaging

Advantages and Disadvantages

• Gray-scale resolution• Reduced radiation exposure to the patient• Faster viewing of images• Lower equipment and film costs• Patient education• Initial set-up costs• Quality of images• Sensor size• Infection control