Chapter 11 Filtration and HVL

What is the primary purpose of a filter

absorb low energy xray photons, reducing pt dose, hardens beam

the use of filtration is not associated with which of the following

increase in beam quantity

list two ways the emission spectrum is affected by adding filtration

increases average energy of beam (shifts to the right)

changes shape of emission spectrum (decreases quantity -> decreasing amplitude)

inherent filtration is defined as

permanently fixed within the tube and housing

what components make up inherent filtration

tube envelope, tube window, dielectric oil

how much filtration is required of equipment operating above 70kVp

2.5 mm Al/eq

how is filtration expressed (unit)

al/eq (aluminum equivalency)

which curve would represent the beam with more filtration

lower of the two

which curve would represent the beam with higher average energy

lower of the two

which curve would represent the harder beam

lower of the two

which type of filter would be most useful in imaging the mediastinum

trough filter

which type of filter would be most useful in imaging an AP foot

wedge filter

filtration located outside the glass envelop is called

added filtration

what components make up added filtration

sheets of aluminum, collimator, mirror

a high energy xray source requires 4 mm of aluminum to reduce the original intensity by 50%. what is the half value layer of this xray source?

4 mm al/eq

a compound filter that utilizes 2 or more materials that complement one another's absorbing abilities is called

k-edge/ compound filter

which filter is used in radiation therapy

thoreaus fitler

a 100 mR/hr xay source has a half-value layer of 1 mm aluminum. how many half-value layers are required to reduce the beam intensity to 12.5 mR/hr?

3 HVL

the general term used for a filter that helps produce an acceptable image when the thickness of the body part imaged varies from one area to the next

compensating

why is it important to absorb low energy xray photons

reduce pt dose

total filtration is the sum of ____ and ___

inherent

added

the term used to express the penetrability, quality, or hardness of the beam

half value layer

how can the xray beam be hardened

increase kvp, high frequency generator, increase filtration

define half-value layer

amount of absorbing material that reduces beam intensity to one half it's original value

what half-value layer is required for equipment operating at 80 kvp

2.3 mm al/eq

what component found in the collimator provides most of the filtration that occurs there

mirror

an increase in total filtration of the beam will increase

average energy of beam

which of the following statements expresses the HVL of an xray beam whose initial value is 300 R/min

2.0 mm Al required beam to 150 R/min

how many half value layers will it take to decrease beam intensity from 500 mR to 125 mR

2 HVL

2mm of al/eq reduces beam intensity from 300 mR to 150 mR. what is the half value layer

2 mm al/eq

the HVL of the equipment is 4 mm al. how many hvl will it take to reduce a 400 mR beam to 100 mR

2 HVL

how many hvl will it take to reduce an xray beam whose intensity is 78 R/min to 9.75

3 HVL

a given exposure of 100R/min requires 3.5 mm al to reduce beam intensity to 50 R/min. what is the HVL?

3.5 mm al/eq

which of the following expresses the HVL of 140 R/min

2.5 mm al yields a beam of 70 R/min

how many HVL are required to reduce beam intensity form 560 mR to 35 mR

4 HVL

the HVL is 2mm al. beam intensity is 150 mR. how many mm of al will reduce the beam to 75 mR

2 mm al/eq

if 6 mm al/eq reduces beam intensity from 200 mR to 50 mR. what is the HVL

3 mm al/eq