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RADT425

Chapter 2

QuestionAnswer
The histogram represents the _________ __________ in the remnant radiation and is determined by the total _______ that is used to create the image. subject contrast, exposure
On a histogram graph, the x-axis identifies_________ and the y-axis identifies_____. x: pixel gray shade value; y: # of pixels with that gray shade value
The VOI on a histogram graph identifies S1 as the (minimal/maximal) gray shade value. minimal
The ________ represents the ideal histogram for the projection. LUT
If the image histogram was positioned farther to the left and was wider that the LUT's histogram, how would the displayed projection differ from that the LUT's histogram represents? the displayed projection would have brighter gray shade value & lower contrast
Where is the exposure indicator reading taken from on the histogram after the histogram has been developed? halfway between S1 & S2 (at the midpoint of the defined VOI)
In computed radiography systems, how much of the IP should be covered with anatomy to avoid and EI error? 30%
What technical factors effect the amount of exposure to the IR receivers? mAs, kV, SID, OID, collimation, grids
Quantum noise is demonstrated on a projection by a(n) __________pattern and indicates ___________________. random (grainy), underexposure
The IR exposure can be off by a factor of ___ and still create an acceptable image. 2
What is the technical factor that controls subject contrast and contrast resolution? kV
True or False, Subject contrast can be recovered with digital post-processing techniques. False
Optimal kV has been used for a projection when the cortical outlines of the _________ & _________ bony structures in the VOI are demonstrated. densest, thickest
Saturation is demonstrated on a projection when details in the VOI demonstrates a(n) __________shade and occurs when the IR exposure is ____________times more that the ideal. pitch black, 4-5
How can the amount of scatter radiation reaching the IR be controlled? use a grid, use tight collimation, place a flat contact shield or edge of apron along the anterior collimation border
When an OID increase causes significant scatter radiation to be diverted from the IR, what technical factor should be increased and by how much ? mAs should be increased by 10% for every cm of OID increase to compensate for IR exposure loss
What type of patient condition causes the tissues to increase mass density or thickness and become more radiopaque? additive
Contrast resolution refers to the degrees of difference in ___________ levels between adjacent tissues with (high/low) contrast demonstrating (lesser/greater) difference. brightness, high, greater
Adjusting the window width changes the _________on the displayed projection and adjusting the window level changes the _______of the displayed projection. contrast, brightness
True or False, The technologist should window a less than optimal projection and save it to PACS so the radiologist can display the manipulated projection. false
True or False, The contrast mask should be used to improve the appearance of collimation on the projection. false
Grid cutoff resulting from poor grid alignment will be greater on the side the CR is angled (toward/away from), will (increase/decrease) with increase severity of misalignment and will be more noticeable with (higher/lower) grid ratios. toward, increase, higher
When should a projection be repeated because of an artifact? when the artifact can be removed and is obscuring a ortion of the VOI
Created by: ashollings