RADIOLOGY LECTURE 7 ~~~~~~~

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Questions and Answers

What are the two most commonly used intraoral radiographs?

Cone beam CT and DPT

Periapical and lateral cephalogram

Occlusal and bitewing

Bitewing and periapical (correct)

How does a PA Mandible radiograph work?

X-rays are captured in a lateral direction

X-rays travel from the posterior to the anterior with the detector outside (correct)

X-rays travel from anterior to posterior

The detector is positioned inside the patient's mouth

What is the primary use of a lateral cephalogram?

To provide orthodontic analysis (correct)

To capture 3D images of teeth

To obtain panoramic images

To view the patient's jaw in multiple angles

What kind of images does CBCT imaging produce?

Cross-sectional and 3D images of anatomy Signup and view all the answers

What type of objects are likely to appear more radiopaque?

Denser and thicker objects that absorb more X-rays Signup and view all the answers

What is the goal of producing an X-ray image?

To produce images that are geometrically accurate with minimal distortion Signup and view all the answers

What part of a tooth appears most radiopaque on an X-ray image?

Amalgam fillings Signup and view all the answers

What happens when more X-rays hit the detector?

The area appears darker or radiolucent Signup and view all the answers

How does the distance of the object from the detector influence its appearance?

Further objects appear more magnified and distorted. Signup and view all the answers

What is the optimal positioning of the detector in relation to the object being imaged?

As close and as parallel to the object as possible. Signup and view all the answers

What effect does increasing the distance between the X-ray source and the detector have on image distortion?

Minimizes distortion and magnification. Signup and view all the answers

What causes the distortion in images when X-ray beams are not parallel to the detector?

X-ray beams hitting the detector at non-perpendicular angles. Signup and view all the answers

What is the primary characteristic of geometrical distortion in panoramic images?

They exhibit some level of geometric distortion. Signup and view all the answers

What happens to the image quality when exposure time to an X-ray is too low?

The image appears underexposed and light. Signup and view all the answers

What is the result of increasing the kV in an X-ray setup?

Increased photon energy and reduced patient dose. Signup and view all the answers

Why are film holders still important for intraoral radiographs?

They help maintain parallel alignment of the detectors within the patient's mouth. Signup and view all the answers

Study Notes

Intraoral Radiographs

Two common types: Periapical and Bitewing
Periapical: Shows full tooth anatomy; can image multiple teeth or a single tooth.
Bitewing: Shows only tooth crowns and bone levels; film bites down on a peg.

Radiographic Techniques

PA Mandible: Images mandible from posterior to anterior; detector on face outside patient's mouth.
DPT/Panoramic: Patient bites on peg; detector and X-ray source rotate around the head at 180°; creates panoramic projection.
Lateral Cephalogram: X-rays pass from one side of face to the other; primarily used by orthodontists; detector outside mouth.
CBCT (Cone Beam CT): Produces cross-sectional and 3D images of teeth and jaws using multiple angles and higher radiation doses; modern technique.
Image Types:
- Intraoral: Periapical, bitewing, occlusal
- Extraoral: DPT/Panoramic, PA mandible, lateral cephalogram
- 3D Imaging: CBCT

Image Quality

Goal: Geometric accuracy with minimal distortion.
Radiolucency/Radiopacity:
- Radiolucent: More X-rays hit the detector (darker).
- Radiopaque: Fewer X-rays hit the detector (lighter).
- Dense objects are radiopaque (absorb more X-rays); less dense objects are radiolucent (allow more X-rays to pass).
Examples: Amalgam fillings are radiopaque.
Distortion:
- Increased distance from detector increases magnification and distortion.
- Closer object/detector reduces divergence and distortion, resulting in higher accuracy.
- X-ray beams need to be as perpendicular as possible to the detector to minimize distortion.
  - Parallel detector/object is not enough- beam isn't actually parallel.
Image Accuracy vs Positioning: Objects should remain parallel and positioned as close to the detector as possible to minimize distortion.
Minimizing Distortion:
- Increase distance between x-ray source and detector.
- Decrease distance of object and detector.

DPT (Panoramic) Specifics

Focal Trough: The green area; the specific section/slice of anatomy that is in focus/imaging.

Image Types and Distortion

Panoramics have some geometric distortion; intraoral generally more accurate.
Overexposure/Underexposure:
- Overexposure: Too much X-ray; dark image.
- Underexposure: Too little X-ray; light image.

kV and Image Production

kV (Kilovoltage): Changes X-ray beam intensity, affecting photon energy.
- Increasing kV decreases contrast and patient dose (more photons reach detector).
- Decreasing kV increases contrast and patient dose (more photons absorbed by patient).

Film Holders

Film holders ensure detectors are parallel with each other.

Other Factors Affecting Image Quality

Proximity of the object or X-ray tube to the detector.
X-ray source further from detector results in less distortion; closer proximity causes more distortion (due to divergence)

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Description

This quiz covers essential intraoral radiographic techniques, including Periapical and Bitewing images. Learn about various methods such as DPT, lateral cephalogram, and the advancements in imaging technology like CBCT. Test your understanding of the types of images produced and their applications in dental practice.