IA Ch. 11 Workbook

The remnant beam is said to carry an organized _______, which is the information that will form an image, but also includes random noise such as scatter radiation

signal

On average, the intensity of the ________ beam that emerges from the body behind the patient and strikes the detector plate, is less than 1% of the primary beam radiation

primary

Primary x-rays fan out evenly or diverge _______ from the focal spot. The center ray, used for centering, is the only “straight” ray in the x-ray beam

isotropically

All anatomy projected by the diverging beam is _____ in the final image to some degree

distorted

In projection geometry, the three important distances through which the x-ray beam passes are abbreviated as the _____, the ______, and the ______

SID, SOD, and OID

List the 6 general types of radiographic variables

Technical Variables, Geometric Variables, Patient Status, Image Receptor Systems, Image Processing, Viewing Conditions

What are some examples of Technical Variables?

kVp, mA

What are some examples of Geometric Variables?

SID, SOD, OID

What are some examples of Patient Status?

body habits

What are some examples of Image Receptor Systems?

Grids

What are some examples of Image Processing?

format changes

What are some examples of Viewing Conditions?

contrast and brightness

All of the visibility characteistics of a remnant radiographic image prior to computer processing- its initial brightness, subject contrast, and level of noise- are controlled by the relationship of the electrical _____ variables employed to the variables of ______ status

tequnique, patient

The photoelectric effect is an “all or nothing” absorption effect that occurs only in the _____ shells of an atom

innermost

An electron ejected out of an atom by completely absorbing an x-ray photon called a ________

photoelectron

The photoelectric effect is primarily responsible for the production of subject ______ in the radiographic image

contrast

The photoelectric effect only occurs when the energy of the incoming x-ray photon is _____ higher than the binding energy for the inner shell electron

slightly

The ideal circumstance for producing high subject contrast is for the _____ kV (which is about 1/3 of the set kVp) to be slightly higher than the binding energies of the tissues in the body

What is the formula for energy distribution during the photoelectric effect?

Ep= Eb + Eke

In the ______ interaction, only a portion of the photon’s energy is absorbed, and the energy left over is re-emitted as a secondary x-ray photon which can be scattered

compton

The Compton interaction is also known as _______ scattering or ________ scattering.

modified, incoherent

However, the scattered x-ray from a Compton interaction should be considered as a _____ x-ray, not as a modified version of the “original x-ray”

new

What is the formula for energy distribution for the Compton interaction?

Ep = Es + Eb + Eke

After subtracting the energy imparted to the scattered x-ray photon, the remaining kV (energy) goes into the kinetic _____ of the recoil electron

energy

A scattered photon from a Compton interaction is very likely to penetrate out of the patients body and reach the image receptor because it carries what?

most of the energy from the original x-ray

From a single original x-ray photon, a _____ of Compoton interactions can occur

series

Scattered rays with higher energy are deflected less, so they travel in a more _____ direction

forward

In diagnostic radiography only a small percentage of generated scatter strikes the image receptor. Most of it is emitted at reversed oblique angles and is called what?

backscatter

even ______ x-rays still retain about 68% or two-thirds of the original photon energy

backscatter

At highter levels of kVp, the scatter radiation produced is directed more ______ the image receptor

toward

Since scatter radiation is a form of noise in the remnant beam image, we might say that Compton interactions work in direct _______ to photoelectric interactions

opposition

Approximately ___% of all scattered x-rays originate from Compton interactions within the patient. The remainign scatter comes from coherent scattering

97

For the _______ interaction, the orbital electron becomes excited but remians in place, so the atom is not ionized

coherent

Since the energy and the wavelength of the incoming and outgoing x-ray photons are identical, coherent scattering is also called ________ scattering

unmodified

The _______ interaction is identical to the Thompson interaction, except that the entire atom is raised to a state of excitation for a brief moment before re-emitting the x-ray photon

rayleigh

The characteristic interaction can follow after any _____ event within the patients body, including both compton and photoelectric interactions

ionizing

Due to the small “size” of the atoms in the soft tissues of the patient, electromagnetic waves emitted from characterstic interactions in these tissues have too low ______ to make it out of the patient to reach the image receptor

energies

General attenuation of teh x-ray bean includes all three types of interactions since both the absorption and the ______ of x-rays can prevent them from reaching the image receptor

scattering

The exponential attenuation of x-rays is about _____% for every 4 to 5 centimeters of soft tissue thickness

50

A related rule of thumb used by radiographers to adjust technique for diffrent body thickneesses is to change the radiographic technique by a factor of ___ for every 4 cm change in part thickness

2

If a body part is 4 cm thinner than average, cut the usual mAs setting in half or reduce the kVp by ___%

15

Even though two organs may be of the same thickness, due to differences in atomic number and physical density, they can produce _______ absorption in differernt portions of the x-ray beam

differential

The difference in radiation intensity between the various portions of the projected image carried by the remnant x-ray beam behind the patient is referred to as what?

subject contrast

Any information missing from the _____ _____ of radiation cannot be recovered at a later stage by computerized post-processing, nor by manipulation of the brightness or contrast of the TV screen

remnant beam

To achieve good subject contrast, sufficient ______ of the x-ray beam must match the properteis of the various tissues such that some x-rays penetrate through every tissue within the body part

penetration

Every anatomical detail in an image must be depicted as a particular shade of ____

gray

For image receptors, the only way that such a thin layer of material can effectively absorb x-rays is by using elements with a high ______ number so that they have a dense electron cloud

atomic

Since the goal for image receptors is to absorb as much x-ray energy as possible, the ________ interaction is preferred

photoelectric