5 & 6 X-Ray Contrast, Radiation Dose, & Image Artifacts

In ________, contrast represents the difference in attenuation properties (μ) of materials along a path.

________ is measured in roentgen (R) and coulomb /kg.

As ________ interact with matter, they are absorbed, scattered, or transmitted.

________ is the weighted average of the spectrum energies (needed because x- rays are polychromatic)

________ to different tissue is dependant on tissue type and the type of radiation.

The amount if radiation in air measured by radiation monitors

The dose of radiation (energy) you are delivering to the tissue, measured by the energy absorbed

A measure of the biological damage to living tissue as a result of the absorbed dose; the biological dose that delivers the same degree of risk to a tissue regardless of the radiation type

An estimate ofo the stochastic effect that a non-uniform radiation dose has on the whole body; weighted sum of dose equivalent by all organs

weighting factor times (absorbed dose of the organ times f)

The difference between foreground and background on an image

The rate of change of the number of photons per unit area, represented by I

Something used to reshape the radiation spectrum to eliminate energies that dont contribute to the image, but do deliver dose

Units for exposure

Units for absorbed dose

Units for dose equivalent

Units for effective dose

The absorbed dose is the amount of energy per mass of tissue, measured in Gy or (BLANK) per (BLANK)

Dose equivalent is equal to Sv, calculated as…

Which will have a higher effective dose, the heart or the hand? Why?

_____ beam geometry has a more compact, practical design, and is more consistent with physics

The ideal beam geometry, stating that all the beams from an x-ray move parallel to one another

T or F: No magnification effect from a parallel beam

Fan beam geometry requires the __________ factor to be taken into account, as well as depth dependent magnification (objects must be the same distance from tube)

To reduce the radiation sent to parts of the body that we don’t want to image, we use a __________, which focuses beam on the center of the object, making the beams closer to parallel

To reduce non-parallel beams and scattered photons, we use a detector-side collimator, or more commonly a _________, to absorb any scattered photons that are trying to reach the detector that would otherwise create noise

An object added to the detector that eliminates perpendicular rays to improve image quality, but may reduce the number of usable photons

The thin, usually lead strips that make up a radiographic grid are called…