Image Quality & Quality Assurance
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each of the black spaces below before clicking
on it to display the answer.
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| show | scan parameters
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| show | scan time
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| One a single-detector row system this is controlled by the width of the collimator opening. On a multidetector row system it is controlled by a combination of collimation and detector configuration | show 🗑
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| show | spatial frequency
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| show | standard deviation
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| show | signal-to-noise ratio (SNR)
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| show | subject contrast
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| How rapidly data are acquired. It is controlled by gantry speed, the number of detector channels in the system, and the speed with which the system can record changing signals | show 🗑
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| show | sampling theorem
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| show | contrast-detail curve
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| show | contrast-detail response
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| The displayed contrast of an image is dependent on the window settings used for its display | show 🗑
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| show | image fidelity
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| show | isotropic
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| Resolution in the xy direction | show 🗑
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| Most commonly used method of describing spatial resolution ability. It is often used to graphically represent a system’s capability of passing information to the observer | show 🗑
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| show | MTF graph
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| A phantom used to measure spatial resolution. This type of phantom is made of acrylic and has closely spaced metal strips embedded in it | show 🗑
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| Ability of a system to resolve, as separate forms, small objects that are very close together. Also called spatial resolution or detail resolution | show 🗑
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| show | kVp
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| show | receiver operator characteristics
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| Measure of the tube current used in the production of x-ray energy. In conjunction with the scan time, it is the quantitative measure of the x-ray beam | show 🗑
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| The product of mA setting and scan time | show 🗑
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| Determines how the data are filtered in the reconstruction process. The appropriate reconstruction algorithm selection depends on which parts of the data should be enhanced or suppressed to optimize the image for diagnosis | show 🗑
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| With digital technology, the image is not as directly linked to the dose, so even an mA or kVp setting that is too high is used, a good image results. This effect can make it difficult to identify when a dose that is higher than necessary is used | show 🗑
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| Ability of the system to differentiate between objects with similar densities. Also called low-contrast resolution | show 🗑
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| The spatial frequency possible on a given CT system at an MTF equal to 0.1 | show 🗑
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| Resolution in the z direction | show 🗑
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| Because an object may not lie entirely within a pixel, the pixel dimension should be half the size of the object to increase the likelihood of that object being resolved | show 🗑
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| show | quantum mottle; AKA quantum noise
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| show | ACR CT accreditation phantom
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| Artifacts that result from insufficient projection data; cause fine stripes that appear to be radiation from a dense structure | show 🗑
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| Artifacts that result from lower-energy photons being preferentially absorbed, leaving higher-intensity photons to strike the detector array | show 🗑
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| show | cone-beam artifacts
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| Phantoms used to measure the radiation dose delivered for various CT examinations. | show 🗑
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| show | edge gradient
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| Result in subtle inaccuracies in CT numbers and can be easily misinterpreted as disease. These artifacts can best be avoided by using a low pitch whenever possible | show 🗑
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| Anything appearing on the image that is not present in the object scanned | show 🗑
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| show | laser light accuracy
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| show | linearity
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| show | out-of-field artifacts
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| Artifact that can result when an object does not appear on all views. Inconsistencies between views cause shading artifacts on the image | show 🗑
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| show | pencil ionization chamber
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| show | reference dose values
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| Determination of the accuracy of the slice thickness selected by the operator versus the width of the collimator opening | show 🗑
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| Undesired surge of electrical current within the x-ray tube. A common cause of equipment-induced artifact | show 🗑
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| show | undersampling
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| show | uniformity
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| show | windmill artifacts
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Created by:
sspatel
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