Ch 11 Creation of the Projected image

What is the remnant beam in radiography?

• The beam that exits the X-ray tube

• Radiation absorbed by tissues

• The portion of the X-ray beam that exits the patient and strikes the detector

• All scattered radiation

Answer explanation

The remnant beam refers to the portion of the X-ray beam that exits the patient and strikes the detector, providing the necessary information for image formation in radiography.

Which interaction is primarily responsible for subject contrast in the image?

• Compton scatter

• Coherent scatter

• Photoelectric effect

• Characteristic radiation

Answer explanation

The photoelectric effect is primarily responsible for subject contrast in images, as it involves the absorption of photons by matter, leading to differences in brightness and detail based on tissue density.

Tags

NGSS.HS-PS4-4

What does OID stand for in radiographic geometry?

• Output-intensity dose

• Optimum image distortion

• Object-image distance

• Origin-incident direction

Answer explanation

OID stands for Object-Image Distance, which is a crucial concept in radiographic geometry that refers to the distance between the object being imaged and the image receptor. This affects image quality and distortion.

A 30-kV x-ray interacts with a K-shell electron in calcium (binding energy = 4 kV). What is the photoelectron’s kinetic energy?

• 4 kV

• 24 kV

• 26 kV

• 34 kV

Answer explanation

The photoelectron's kinetic energy is calculated by subtracting the binding energy from the x-ray energy: 30 kV - 4 kV = 26 kV. Thus, the correct answer is 26 kV.

Tags

NGSS.HS-PS3-1

NGSS.HS-PS4-3

What is the result of a Compton interaction?

• Total absorption of the X-ray photon

• No ionization

• Scattered photon and ejected electron

• No change to photon energy

Answer explanation

In a Compton interaction, an X-ray photon collides with an electron, resulting in the scattering of the photon and the ejection of the electron. This is why the correct answer is 'Scattered photon and ejected electron'.

Tags

NGSS.HS-PS4-4

The central ray (CR) is unique because:

• It is the only non-diverging (straight) ray

• It has the highest energy

• It rotates around the focal spot

• It always hits the thickest anatomy

Answer explanation

The central ray (CR) is unique because it is the only non-diverging (straight) ray in radiography, ensuring accurate alignment and optimal image quality, unlike other rays that spread out.

Tags

NGSS.MS-PS4-2

What type of radiation degrades subject contrast by adding random exposure?

• Photoelectric photons

• Scattered radiation

• Attenuated rays

• Characteristic photons

Answer explanation

Scattered radiation adds random exposure to the image, which degrades subject contrast. Unlike photoelectric photons, which contribute to image formation, scattered radiation interferes with clarity.

Tags

NGSS.HS-PS4-3

What does attenuation mean in radiography?

• Beam scatter enhancement

• Conversion of energy into heat

• Full absorption of radiation by detectors

• Partial absorption and reduction in beam intensity

Answer explanation

In radiography, attenuation refers to the partial absorption and reduction in beam intensity as radiation passes through materials, making this the correct choice. Other options do not accurately describe this phenomenon.

Which of the following contributes least to the final image?

• Remnant beam

• Coherent scatter

• Photoelectric effect

• Subject contrast

Answer explanation

Coherent scatter contributes least to the final image because it results in low-energy photons that do not significantly contribute to image formation, unlike the remnant beam, photoelectric effect, and subject contrast.

Tags

NGSS.HS-PS4-5

Why can missing image data due to full attenuation not be recovered later?

• The computer lacks access to DICOM tags

• Information never reached the detector and cannot be processed

• The data is encrypted

• Scatter blocks access to memory files

Answer explanation

Missing image data due to full attenuation cannot be recovered because the information never reached the detector, making it impossible to process. Thus, the correct choice is that the data cannot be retrieved.