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MARIANNE EXAM 3

Quality Management Created by Krystal

QuestionAnswer
What affect does an increase in filtration have on Density and Contrast? density - decreases density because it eliminates quantity(mA) of beam used contrast - lower contrast as leaves with higher kVp
An increase in SID(from 40" -> 72") will have what affecton Density and Contrast? decrease density and have no effect on contrast
What affect does increasing the grid ratio have on Contrast and density? increase the contrast and decrease the density( High grid ratio= higher contrast)
What affect does increasing the OID have on Density and Contrast? decrease density and increase the contrast.
If you Increase kVp what will happen to Contrast?...Density? decrease contrast and increase density
If you increase beam restriction what will happen to Density? ...Contrast? increase contrast and decrease density
mAs controls what? Density
If you increase mAs what happens to Contrast?...Density? No affect on Contrast, and increase in density
A 15% increase in kVp does what to density? doubles the density. (This is why when we use the 15% rule we either halve or double the mAs to MAINTAIN the same density on our image
An increase in SID ( from 40"-> 72") will have what affect on Detail?....Distortion? increase the detail which in turn will decrease distortion
An increase in Focal Spot Size (from a small to a large) will have what affect on Detail?...Distortion? decrease the detail and has no affect on distortion.
An increase in motion will have what affect on detail?.....distortion? decrease the detail cause it'll look blurry and increase the distortion
An increase in OID will have what affect on Detail?...Distortion? decrease detail and increase distortion ( the closer you have the object to the IR the better detail)
Define Radiographic Quality refers to the fidelity with which the anatomical structure that is being examined is imaged on the radiograph. A image that faithfully reproduces structure and tissue is identified as a high-quality radiograph
Define Spatial Resolution refers to the ability to image small objects that have high subject contrast such as a bone-soft tissue interface, a breast micro calcification or a calcified lung nodule
Define Contrast resolution is the ability to distinguish anatomical structures of similiar subject contrast such as liver-spleen and gray matter-white matter.
Define Noise Radiographic noise is the random fluctuation in the optical density of the image
Define Quantum Mottle refers to the random nature by which x-rays interect with the IR. When few x-rays are cast at the IR, the resulting image appears mottled or blotchy.
Define the Characteristic Curve The relationship between OD and radiation exposure create the curve. Need an optical step wedge(sensitometer) and a densitometer to create this
Define magnification when an image on the radiograph is larger then the object they represent.
How can you minimize magnification? Use the largest SID and the smallest OID
Define Distortion unequal magnification of different portions of the same object.
Distortion depend on......? 1. Object thickness 2. object position 3. object shape
Define Focal spot blur A blurred region on the radiograph over which the rad tech has little control. Occurs because the focal spot is not a point.
Focal spot blur is greatest on which side?.... Cathode or Anode? Greater on the cathode side
How can you minimize focal spot blur? Use small focal spot and position patient so that part is close to IR. SID's are usually fixed already but use as far as possible.
Define Heel effect varying intensity across the x ray field in the anode-cathode direction
Factors effecting subject contrast patient thickness, tissue mass density, effective atomic #, object shape, kilovolt peak
Define Motion Blur movement of the patient or the x ray tube during exposure results in blurring of the image
Define Sensitometry the study of the relationship between the intensity of exposure of the film and the blackness after processing is called this
Sharpness of image detail is best measured by.....? Spatial resolution
The visibility of image detail is best demonstrated by.....? Contrast resolution
Define foreshortening means that the anatomical part appears smaller than normal
Define elongation means that the anatomical part of interest appears bigger than normal
Visibility of image detail describes the ability to see the detail on the radiograph and is best measured by contrast resolution
How does Latitude affect the Characteristic Curve? If you have a Narrow latitude(short scale, hign contrast)you have a steep slope. If you have a Wide latitude you'll have a long slope with long scale and low contrast.With wider latitude mAs can vary and still produce good image.
Procedures for reducing motion blur? Use shortest exposure time, provide good communication or using restraining device. Use a Large SID, and Small OID
How does phototimer work? Its a device that allows AEC. It senses the amount of radiation incident on the IR, through electric feedback circuit, radiation exposure is terminated when sufficient # of x-rays has reached IR to produce an acceptable optical density
Base plus fog optical density has a range of approx? 0.1 to 0.03
The straight line portion of a characteristic curve represents..... the region in which a properly exposed radiograph appears. Its the diagnostic range.
How can you reduce quantum mottle? use high mAs and low kVp setting, slower IR
What are the principal exposure technique factors? kVp, ma x s or mAs, and SID
With AEC, explain how the exposure could terminate early? the cells cannot tell the difference between the primary beam and the scattered radiation, so if a high proportion of scatter radiation reachs cells, exposure is terminated prematurly
How can you reduce magnification? Large SID, shortest OID
The useful reange of OD is approx? 0.25 to 2.5
Fast IR's have_____ noise and what does it do to spatial resolution and contrast resolution? they have high noise and low spatial resolution and low contrast resolution
High spatial resolution and contrast resolution require____noise and __________ IR's low noise and slow IR's
Focal spot does not affect...... it only affects...... Focal spot does NOT affect contrast or density, it affect recorded detail and focal spot blur.
Distortion can be reduced by...... positioning the anatomiacal part of interest in a plane parallel to that of the IR
Increased Pt thickness does what to contrast and density? Decreased Contrast(cause more scatter) and Density...Has a indirect relationship with both
Increase grid ratio...what happens to contrast and density? Increased contrast and decreased density. (Higher grid ratio=higher contrast cause more lead strips absorbing more scatter so image with be more black and white)
Increased compression has what affect on contrast, density, detail and distortion? Nothing on Density, Increased contrast cause less scatter, also increased detail and no effect on distortion.
Created by: mcc radiology