Radiology Exam 5 Flashcards
What is the purpose of an occlusal radiograph?
Is to view large areas of the maxilla or the mandible (the film is placed between the teeth)
What are the twp types of occlusal radiographs?
Topographical and Cross-Sectional
Topographical
Produces a large PA radiograph
-a greater amount of information of the alveolar crest and the apical areas than PA’s
Cross-sectional
Gives more information about tori, impactions, and malpositioned teeth
It will show calcifications in soft tissues; salivary gland stones or calcifying cysts
Occlusal radiographs are used to locate:
Supernumerary, Impacted, Unerupted teeth Retained Roots Cysts & Tumors Foreign bodies Sialoliths Bone fractures Size & shape of Tori Sinus borders Cleft palates
5 Typical Radiographs
Maxillary Anterior Maxillary Posterior Mandibular Anterior Mandibular Posterior Mandibular cross-sectional
SLOB
Same Lingual Opposite Buccal
3 Methods of Localization:
Definitive Evaluation
Right Angle
Tube Shift
Definitive Evaluation
Based on shadow casting priniciples that is an object positioned farther away from the film will be magnified and less clearly imaged
Which method of localization is the least reliable of all the methods?
Definitive Evaluation
Not an acceptable method in endodontic procedures; really not effective if looking for a foreign body
Right Angle Method
Tube Shift Method
(Buccal-Object Rule)
Most versatile and the one used most often
When 2 radiographs are taken from a slightly different angle (either horizontal or vertical), the structures shift slightly on the radiographs. If the structure moves in the same direction as the tubehead then the structure is on the lingual.
Tube Shift Method
Refers to the technique for producing a broad view image of the entire dentition both maxillary and mandibular on a single film
Panoramic Radiography
It depicts not only the teeth and alveolar bone but also the sinuses, the TMJ, the maxilla, and the mandible
Panoramic Radiography
Panorex is best used for:
large caries examining large areas of the face/jaws locating impacted teeth or root tips evaluating trauma, lesions, diseases assessing growth and development
Lacks in sharpness and detail so if often prescribed with BW’s or additional PA’s to focus on detail
Panorex
Advantages of Pano radiographs:
- Diagnostic quality with less radiation than a full mouth series
- Less discomfort for patient
- Easier which means less retakes
- Better time management for the dental team
DISadvantages of Pano radiographs:
- Less sharp & less detail
- Magnifies more & distortion
- Ghost images (mirror images present)
- Info overload (including artifacts)
- Not all patients fit into the average
- Increased overlapping
- Labial & Lingual teeth do not image well (they tilt)
- Cannot depict early bone loss
- The spine is sometimes visible
- Patients may get too impatient
- COST
Specialized radiographic technique to show images of structures located within a selected plane of tissue while blurring structures outside of the selected plane
It utilizes a narrow beam of x-rays to image a curved layer or slice of tissue
Tomography
What happens during tomography and rotational panoramic radiography?
The tube head and film do not remain stationary as in intraoral radiography but moves in relationship to each other to FOCUS the x-ray beam on a selected layer of interest while blurring out structures outside of that layer
When taking a panoramic radiograph, where is the patient’s head placed?
Between the tubehead and the film cassette. The tube head and the cassette rotate around the head for 15-20 seconds while blurring out the spine, skull, etc…
In what direction do the tube head and cassette move?
They rotate behind the patient’s head and the cassette moves in front in concert with each other. They are ALWAYS opposite of each other to create a perpendicular angle for the x-ray beam to film.
Defined as the axis on which the tube head and the cassette rotate is the functional focus of the projection
Rotational centers
When taking a panoramic radiograph, how does the radiation beam pass through a patient?
Vertically through the patient toward the cassette and through another vertical slit in the cassette holder to expose the film as it rotates.
Round cassette
Rotates in concert with the rotations around the patient to keep exposing a new area of film
Hard flat cassette
Moves to the side in concert with the other rotations to keep exposing new film
What kind of rotational center is this?
The tube head and cassette rotate to the mid-line the nthe radiation resumes along with continuation of the rotation. A split image results with a blank space at the mid-line
Double center rotation
What kind of rotational center is this?
Three centers of rotation are used but the shift of the x-ray beam is so efficient that a continuous image results on the film.
Triple Center Rotation
What kind of rotational center is this?
Most modern machines fall in this category. The elliptical pattern closely matches the arc of the teeth. A continuous image is produced. The horizontal and vertical magnification are relatively constant. The elliptical pattern can be adjusted to fit most people.
Moving Center Rotation
Horizontal Plane
The focus is at the center of the rotation
Vertical Plane
The focus is at the target in the tubehead
Width of the trough and the distance from the rotational center is controlled by:
The speed of the moving cassette controlled by manufacturer
The vertical is preset in the tube head and the trough is a set shape. You cannot aim the tube head so you MUST do what?
Place the patient properly to put them in the correct line of radiation
Types of Machines:
Stand-up, Sit-down, Flexible cassettes, and Hard cassettes
Generates electrons to generate x-rays. The fixed vertical position is usually around 8 degrees or pointing slightly upward.
X-ray Tube Head
Can be flat or a drum and rotates in front of the patient and rotates or moves to the side to advance the film into the x-ray beam as the tube head rotates
Cassette Holder
Transfers x-ray energy into visible light
Allows for much less radiation since intensified
Smooth plastic almost looks like cardboard
Coated with minutes fluorescent crystals called phosphors
When exposed to x-rays phosphors fluorescence and emit blue or green light
Intensifying Screens
Screen film must be placed between intensifying screen inside of a cassette either rigid or flexible.
Blue sensitive film must be paired with blue light screens.
Extraoral Film
Most machines are equipped with a bite block or forehead rest. Side positioners or a mirror is used for determining the correct alignment of the mid-saggital place and a chin rest to correctly locate how far up or down the arches should be positioned.
Head Positioner Guides
Allows for the selection of the mA and kVp as recommened by the manufacturer according to the size of the patient and the density of the tissures to be imaged.
kVp controls are adjusted up for better penetration of larger patients or denser tissues and adjusted down for children and edentulous patients
Exposure Control Panel
Lead Aprons are used with panoramic radiographs but not with a thyroid collar. Why?
The beam will be obstructed and the film not diagnostic.
3 Facial landmarks are:
Mid-saggital Plane: Imaginary line divides the patient into a right and left halves down the center of the nose assuming the patient is positioned perpendicular to the floor
Ala-tragus Line: Imaginary line from the ala of the nose (side of the nose) through the tragus (front of the ear)
The Frankfort Plane: Imaginary line from the orbital ridge (under the eye) to the acoustic meatus ( ear opening). When positioned correctly, this line will be parallel to the floor.
The better the positioning, the _________
less the magnification and loss of sharpness in the radiograph
Errors:
Pt too far forward: Anterior teeth will be blurred and diminished in width
Pt to far back in trough: Anterior teeth are blurred and magnified
Pt head tilted or rotated: Teeth closer to the film will be smaller or teeth closer to the rotational center (farther from film) will appear magnified
Pt’s chin tipped too low (Frankfort place angled downward) exaggerated smile
Pt’s chin is tipped up: The image will appear as an exaggerated frown
Pt is slumped
Patient Prep Errors:
Failures to remove any object
Thyroid collar is not used
Thickly padded clothing may impede tubehead
Patient must understand and cooperate by holding still and resting tongue against palate and close lips around the bite guide.
Filmless imaging
Digital Radiographs
Converts conventional radiographs to digital via. a scanner equipped with a transparency adapter OR via use of a digital camera
Indirect Digital Imaging
A digital imaging system is used to replace the traditonal film.
Direct Digital Imaging
Direct Digital Goals:
To produce high quality diagnostic images by improving the quality through pixels, spatial resolution, and gray scale
Direct Digital Uses:
To detect and classify oral disease and lesions, to detect trauma, evaluate growth and development and working film used in endo or surgery
Digitally merging 2 images to show changes that occur over time
Digital Subtraction
“Short” for picture element
Pixel
Discernable seperation of closely adjacent image details and determined by the number and size of the pixels
Spatial Resolution
Greatest number of paired lines visible in 1mm of image and increasing resolution increases sharpness
Line Pair
Special plate sensitive to x-rays that captures the radiographic image
Sensor
Very much like contrast in an image. It is defined as the number of shades in an image
Gray Scale
The human eye can only distinguish approximately __ shades of gray
32
3 Types of Sensors:
CCD: Charged- coupled device, most widely used, each element represent 1 pixel
CMOS: Complementary metal oxide semiconductor , requires less computer power
PSP: Photo Stimuable Phosphor, completely different kind of sensor, rare earth phosphor
Allows for manipulation of the image by the operator
Digital software
Advantages of Digital:
Less radiation Quicker viewing Eliminates darkroom Diagnostic image may be manipulated Improved gray scale Remote transfer for consultation (email) Use in patient education via monitor
Disadvantages of Digital:
Expensive as crap Technology concerns Learning curve Sensor size- thicker, most exposure needed to cover Infection Control Legal Issues
DICOM
Digital Imaging and Communications in Medicine is addressing the ID theft. This will be ever changing.
Purpose of Extraoral radiographs:
Examine large areas of jaw or skull Study growth Detect fractures and evaluate trauma Detect lesions/diseases TMJ Sub for intraoral when patient cannot open mouth
Used in conjunction with a pair of intensifying screens housed inside a light-tight cassette
It is loaded into a cassette in the darkroom that is safe for extraoral film
Screen Film
Proper Film Handling:
Edges only
Clean, dry hands
Do not slide film across the intensifying screens (makes static electricity)
Use 1 film only
Be sure box is closed before turning on light or opening door to darkroom
Transfers x-ray energy into visible light which exposed the screen film
Intensifies the effect of the x-rays on the film
Allows for reduction radiation
Works in pair
Smooth cardboard or plastic sheets in appearance
Intensifying Screens
Screens that emit green light when energized by x-rays and must be paired with a green-light sensitive film
Rare Earth screens
Screens that emit a blue to violet fluorescent light and must be paired with blue-light sensitive film
Calcium Tungstate screens
Hold intensifying screens in close contact with the film protecting all from light exposure
Cassettes
A type of cassette that is usually 5x7 inches and have a front and back joined with a hinge. The front cover is plastic and the back cover is metal.
Rigid Cassette
A type of cassette with sleeves usually 5x6x12 inches with snaps or velcro to fasten plastic. Very easy to tear if handles roughly
Flexible cassette
Sometimes used to absorb scatter radiation
Placed between the patient and film in order to absorb scatter radiation and reduce film fog to improve image contrast
GRIDS
Extraoral film does not have a dot which means?
It is impossible to tell front and back without small “L” or “R” lead letters places inside the cassette on one of the screens.
7 most common projections:
Lateral Jaw Radiograph aka Mandibular Oblique
Lateral Cephalometric Radiograph
Posterioranterior Cephalometric Radiograph
Waters Radiograph (Sinus Projection)
Reverse-Towne Radiograph
Submentovertex Radiograph (Base projection)
Transcranial Radiograph (TMJ projection)
Aids in diagnosing ankylosis (stiffening) of the TMJ caused by fibrous or bony union via malignancies, fractures, and arthritis
Transcranial Radiograph
Used to show the base of the skull, the position, and orientation of the condyles, the sphenoid sinus and fractures of the zygomatic arch
Submentovertex Radiograph (Base projection)
Used to examine fractures of the condylar neck of the mandible. Placed vertically with the patient’s forehead on the cassette with mouth open and head tipped down until chin touches chest
Reverse-Towne Radiograph (Open mouth projection)
Similar to posterioranterior except the center of interst is focused on the middle 1/3 of the face. It evaluates maxillary frontal and ethmoid sinus areas.
Waters Radiograph (Sinus projection)
Show entire skull; It examines facial growth, and dev. disease, trauma, etc
Posterioranterior Cephalometric Radiograph (PA projection)
Device used to standardize the placement of the head during exposure for a series of identically angled exposures.
Cephalometer
May either be a lateral skull projection or a frontal projection
Lateral Cephalometric Radiograph
Cassette is positioned flat against the cheek and is centered over the mand. 1st molar area. The edge of the cassette should protrude slightly beyond the tip of the nose and chin.
Lateral Jaw Radiograph
