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RADT425
Chapter 2
| Question | Answer |
|---|---|
| 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
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