RADT 311: Exam 3

The x-ray beam is primarily divided into what 2 parts?

Primary beam and Remnant beam

What is the primary beam?

Radiation emitted by tube but not yet passed through patient or object

What is the remnant beam?

Radiation that emerges from body tissues behind the patient or object and it is the IMAGING-FORMING RADIATION

Primary x-rays diverge isotropically (fan out) except the ___________.

central ray (CR)

What are the six types of radiographic variables?

Technical, geometrical, patient status, IR systems, image processing, and viewing conditions

What are the 3 interactions applicable to diagnostic radiography?

Photoelectric effect, Compton interaction, Coherent scattering (Thompson, Rayleigh)

The photoelectric effect was first explained by:

Albert Einstein

The Photoelectric effect: The patient's body __________ (completely/partially/momentarily) absorbs the x-ray photon.

completely

The Photoelectric effect: A photon intersect an orbital electron in the _____________ shell.

innermost

_____________ is primarily responsible for the production of subject contrast in the radiographic image.

The Photoelectric Effect

The Photoelectric effect: Leaves a microscopic spot that is unexposed or ____________.

white

What is another name for Compton Scatter?

Modified / Incoherent Scatter

Who discovered Compton Scatter?

Arthur Compton

Compton Scatter: _________ (complete/partial/momentary) absorption of the x-ray photon’s energy occurs and the energy left over is reemitted as a new x-ray photon.

Partial

Compton Scatter: Occurs in the _______ electron shells of an atom.

outer

T/F: Compton Effect: The recoil electron cannot reach the IR, but the scattered x-ray photon can reach the IR.

True

A series of Compton interactions can occur, until, when the remaining energy is slightly above the binding energy of a shell, a __________ interaction may take place

photoelectric

Scatter x-rays with ________ (higher/lower) energy are deflected less from the direction of the original x-ray.

higher

T/F: Scatter x-rays with higher energy travel in a more forward direction and are more likely to reach the IR.

True

Approximately _____ % of all scatter is caused by the Compton interaction.

97%

_____ % of all scatter is caused by Coherent Scatter.

3%

Coherent Scatter: __________ (complete/partial/momentary) absorption of the x-ray photon’s energy by an orbital electron or by the atom as a whole

Momentary

Coherent Scatter: The emitted photon has _________ energy to the original

identical

T/F: Coherent Scattering: The scattered photon may reach the IR and degrade contrast.

True

Coherent scattering is also called ____________ scattering.

unmodified

With a Thompson interaction, the photon energy is absorbed and re-emitted by a ______________.

single orbital electron

With a Raleigh interaction, the photon energy is absorbed and re-emitted by the excited ______________.

atom as a whole

For every 4 cm (1.5 in) increase in part thickness, increase technique by _________

a factor of 2 (double the mAs or increase kVp by 15%)

T/F: Any information missing from the remnant beam cannot be recovered later by computer processing nor by image manipulation at the display monitor.

True

Photon energy is ______ dependent.

kVp

__________ is produced by the differential absorption between various tissues of the body.

Subject Contrast

__________ is defined as mass per volume in the patient. It may be thought of as the concentration of atoms or molecules packed into a given space.

Tissue Density

The occurrence of all interactions, (both Photoelectric and Compton), is __________ proportional to the physical density of the tissue through which the x-rays pass.

directly (twice as many molecules per cubic cm causes twice as many interactions)

_____________ is an average that takes into account the number and “size” of each type of atom.

Tissue atomic number

The occurrence of the Photoelectric effect is ______ (increased/decreased) as kVp is increased.

decreased

Penetrating x-rays produce what shade in the image.

darker (black) areas

Photoelectric interactions produce what shade in the image.

lighter (white) areas