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Radiation Health and Safety

X-ray Equipment and Positioning Practice Questions

20 free X-ray Equipment and Positioning practice questions for the CDA. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.

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Question 1 of 20 Medium

Which component of the dental X-ray machine directs and restricts the size of the X-ray beam?

  1. A Transformer
  2. B Collimator
  3. C Anode
  4. D Filament

Correct answer: Collimator

The collimator limits the size and shape of the X-ray beam to reduce patient exposure. It ensures that only the area needed for imaging is exposed.

Question 2 of 20 Medium

What is the function of the position-indicating device (PID)?

  1. A Amplify the X-ray beam
  2. B Direct the X-ray beam toward the receptor
  3. C Reduce exposure time
  4. D Hold the receptor in the patient’s mouth

Correct answer: Direct the X-ray beam toward the receptor

The PID directs the beam accurately toward the receptor. Correct alignment reduces scatter radiation and prevents retakes.

Question 3 of 20 Medium

Which PID shape provides the greatest reduction in patient radiation dose?

  1. A Round PID
  2. B Pointed plastic PID
  3. C Rectangular PID
  4. D Closed-cone PID

Correct answer: Rectangular PID

Rectangular PIDs limit the beam to the receptor’s shape, reducing patient exposure by up to 70%. Round cones expose a larger area.

Question 4 of 20 Medium

What effect does increasing the source-to-film distance (long PID) have on the image?

  1. A Increases both magnification and blur
  2. B Less magnification, sharper image
  3. C Decreases sharpness and increases fog
  4. D Eliminates any need for collimation

Correct answer: Less magnification, sharper image

A longer PID reduces beam divergence, producing sharper images with less magnification. It also helps reduce patient exposure.

Question 5 of 20 Medium

The paralleling technique requires the receptor to be placed:

  1. A Directly against the tooth
  2. B Parallel to the long axis of the tooth
  3. C At a steep angle to the occlusal plane
  4. D Perpendicular to the occlusal plane

Correct answer: Parallel to the long axis of the tooth

In the paralleling technique, the receptor must remain parallel to the long axis of the tooth. This produces accurate, undistorted images.

Question 6 of 20 Medium

Which error occurs if the PID is not centered over the receptor?

  1. A Foreshortening
  2. B Elongation
  3. C Cone-cutting
  4. D Overlapping

Correct answer: Cone-cutting

Cone-cutting occurs when the X-ray beam does not fully cover the receptor. Proper PID centering prevents this problem.

Question 7 of 20 Medium

What is the correct vertical angulation for bitewing radiographs?

  1. A -10 degrees
  2. B 0 degrees
  3. C +10 degrees
  4. D +30 degrees

Correct answer: +10 degrees

+10 degrees ensures that both crowns and alveolar crest are visible. Incorrect angulation leads to distorted images.

Question 8 of 20 Medium

Which component of the X-ray tube generates electrons through heating?

  1. A Anode target
  2. B Cathode filament
  3. C PID cone
  4. D Step-up transformer

Correct answer: Cathode filament

The cathode filament heats up to release electrons, beginning the production of X-rays. This is the first step in the exposure process.

Question 9 of 20 Medium

What happens if the vertical angulation is too steep when taking a periapical radiograph?

  1. A Foreshortening
  2. B Elongation
  3. C Cone-cut
  4. D Overlap

Correct answer: Foreshortening

Excessive vertical angulation causes foreshortening, making teeth appear shorter. Proper angulation prevents distortion.

Question 10 of 20 Medium

Which technique generally produces the most accurate and least distorted periapical images?

  1. A Bisecting angle technique
  2. B Paralleling technique
  3. C Occlusal technique
  4. D Topographical technique

Correct answer: Paralleling technique

The paralleling technique reduces distortion and magnification. It is considered the preferred method for diagnostic accuracy.

Question 11 of 20 Medium

Which error results from insufficient vertical angulation?

  1. A Foreshortening
  2. B Elongation
  3. C Cone-cut
  4. D Film fog

Correct answer: Elongation

Insufficient vertical angulation produces elongated images. This occurs when the beam is too flat relative to the tooth.

Question 12 of 20 Medium

What is the function of aluminum filtration in the X-ray tube head?

  1. A Reduce scatter radiation
  2. B Remove low-energy photons
  3. C Increase receptor sensitivity
  4. D Improve PID alignment

Correct answer: Remove low-energy photons

Filtration removes low-energy photons that would be absorbed by tissues without contributing to the image. This reduces patient dose.

Question 13 of 20 Medium

What is the term for the area where the X-ray beam exits the tube head?

  1. A Anode window
  2. B Beam portal
  3. C Focal spot
  4. D Window aperture

Correct answer: Window aperture

The window aperture is the opening through which the beam exits the tube head. It forms the beginning of the path toward the PID.

Question 14 of 20 Medium

What positioning error causes the contact areas of teeth to appear overlapped on a bitewing radiograph?

  1. A Incorrect vertical angulation
  2. B Incorrect horizontal angulation
  3. C Receptor bending
  4. D Underexposure

Correct answer: Incorrect horizontal angulation

Improper horizontal angulation causes overlapping of proximal surfaces. Correct angulation is essential for detecting caries.

Question 15 of 20 Medium

Which step helps ensure correct image geometry when using the paralleling technique?

  1. A Using a short, round PID cone
  2. B Placing the receptor firmly against the teeth
  3. C Aligning the PID perpendicular to receptor
  4. D Angling the receptor at 45 degrees

Correct answer: Aligning the PID perpendicular to receptor

The PID must be perpendicular to the receptor to achieve accurate image geometry. This reduces distortion and improves clarity.

Question 16 of 20 Medium

Which type of PID reduces patient exposure the most?

  1. A Short, round PID
  2. B Long, rectangular PID
  3. C Short, rectangular PID
  4. D Long, round PID

Correct answer: Long, rectangular PID

A long, rectangular PID decreases beam divergence and reduces exposed tissue area. This results in the lowest patient dose.

Question 17 of 20 Medium

When using the bisecting technique, the central ray is directed:

  1. A Perpendicular to the receptor
  2. B Parallel to the long axis of the tooth
  3. C Perpendicular to the imaginary bisector
  4. D Parallel to the occlusal plane

Correct answer: Perpendicular to the imaginary bisector

The bisecting technique uses the rule of isometry: the beam is directed perpendicular to the bisector of the tooth and receptor angle. This minimizes distortion when paralleling is not possible.

Question 18 of 20 Medium

Which error results from bending a digital sensor or film?

  1. A Foreshortening
  2. B Elongation
  3. C Cone-cut
  4. D Image distortion

Correct answer: Image distortion

Bending the receptor distorts the recorded image. This is common in mandibular anterior exposures where space is limited.

Question 19 of 20 Medium

A blurred radiographic image is most likely caused by:

  1. A Incorrect horizontal angulation
  2. B Patient or tube head movement
  3. C Too much filtration
  4. D Excessive collimation

Correct answer: Patient or tube head movement

Any motion during exposure results in image blur. Stabilizing the patient and equipment prevents this artifact.

Question 20 of 20 Medium

What is the primary purpose of using receptor-holding devices?

  1. A To reduce patient exposure time
  2. B To decrease the required PID length
  3. C To stabilize and align the receptor
  4. D To eliminate the need for collimation

Correct answer: To stabilize and align the receptor

Holding devices ensure correct receptor placement and PID alignment. Proper positioning reduces errors and prevents retakes.

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