Final Exam Questions Flashcards
what is said to be directly proportional to receptor exposure?
mAS, OID, SID, or grid ratio
mAS
what is the formula for mAS?
mA*time = mAS
how do you define grid ratio?
the ratio of the height of the lead strips to the distance between the lead strips in a radiographic grid
the construction of the grid provides for greater absorption of —- radiation than of —-
scatter, primary
grids are recommended for body parts measuring greater than — cm
12
The large number of exposures a DR detector can capture and display is its
dynamic range
If all other things are constant, increasing mAS is required when the part gets thicker in order to maintain
receptor exposure
what is the purpose of a beam restrictor?
minimizing scatter radiation, limit beam to precise anatomical area, and enhance contrast
a lead shield placed over male gonads can reduce dosage by as much as:
90%
more rows and columns will result in — pixels
smaller
the radiographic quality that is defined as misrepresentation of size/shape is?
distortion
what type of contrast is better for extremities and shows more detail?
high contrast
Which element is associated with indirect capture DR?
cesium iodide
Selecting from available shades of gray and assigning a numerical value to each pixel is known as;
quantization
what element is associated with direct capture DR?
a-selenium
what is not essential to the production of x-rays?
a rotating anode
the target of a diagnostic x-ray tube is usually made of what element?
tungsten
of total available energy, only about — % is converted to x-ray energy
less than 1%
the vast majority of available energy is transformed into:
heat
half-value layer
A materials half-value layer, or half thickness. Thickness of material at which the intensity of radiation entering it is reduced by one half
The interaction that usually occurs in the K or inner electron shell is:
photoelectron effect with true absorption
the acute dose of radiation that will result in the death of 50% of a group within 30 days (LD 50/30) is considered to be about – sv.
3
what is the typical exposure from a PA chest radiograph?
0.1-0.2mGy (10-20 mR)
the information for hereditary is contained in the:
nucleus