FREE RADIOLOGY AND STUDY GAMES ABOUT CT PHYSICS

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FREE RADIOLOGY AND STUDY GAMES ABOUT CT PHYSICS

TERMS III EXAM QUESTIONS

Actual Qs and Ans Expert-Verified Explanation

This Exam contains:

-Guarantee passing score -49 Questions and Answers -format set of multiple-choice -Expert-Verified Explanation Question 1: 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

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milliamperes Question 2: 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

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Nyquist sampling theorem Question 3: Phantoms used to measure the radiation dose delivered for various CT examinations.

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CTDI phantoms Question 4: 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

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reconstruction algorithm

Question 5: Determination of the accuracy of the alignment of the laser light used for patient positioning

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laser light accuracy Question 6: Inaccuracies in the image caused when parts of the patient are located outside the scan field of view. These artifacts occur because the anatomy outside the SFOV attenuates and hardens the x-ray beam, but is ignored in the image reconstruction process

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out-of-field artifacts Question 7: A solid phantom that contains 4 modules & is made primarily from a water equivalent material. Each is 4cm deep & 20cm in diameter, w/ external align't markings to center phantom in the x, y, & z axes, & is used to measure diff. aspects of image quality

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ACR CT accreditation phantom Question 8: The relationship between CT numbers and the linear attenuation values of the scanned object at a designated kVp value

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linearity Question 9: Time the x-ray beam is on for the collection of data for each slice. Most often it is the time required for the gantry to make a 360 degree rotation, although with overscanning and partial scanning options there may be some mild variation

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scan time

Question 10: Image accuracy

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image fidelity

Question 11: Equal in all directions; a voxel that is cube-shaped

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isotropic

Question 12: 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

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slice thickness Question 13: 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

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uncoupling effect Question 14: 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

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modulation transfer function (MTF) Question 15: The ability of the scanner to yield the same CT number regardless of the location of an ROI within a homogeneous object

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uniformity

Question 16: Resolution in the z direction

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longitudinal resolution Question 17: Ability of the system to differentiate between objects with similar densities. Also called low-contrast resolution

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contrast detectability Question 18: Artifacts that result from lower-energy photons being preferentially absorbed, leaving higher-intensity photons to strike the detector array

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beam-hardening artifacts

Question 19: Factors that can be controlled by the operator & affect the quality of the image produced. These factors include mA, scan time, slice thickness, FOV, reconstruction algorithm, & kVp. When using helical scan methods, operator also has a choice of pitch

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scan parameters Question 20: Relates to the inherent properties of the object scanned. For ex., the lung possesses high ___ b/c it's primarily air-filled. The low attenuation lungs provide a background that makes nearly any other object visible b/c of its difference in density

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subject contrast Question 21: Undesired surge of electrical current within the x-ray tube. A common cause of equipment-induced artifact

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tube arcing

Question 22: Defines the quality (average energy) of the x-ray beam

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kVp Question 23: The subjectivity inherent in the method of evaluating contrast resolution that requires an observer to detect objects as destine. Result can vary because different observers will often look at the same image and evaluate it differently

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receiver operator characteristics Question 24: Artifacts that result from insufficient projection data; cause fine stripes that appear to be radiation from a dense structure

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aliasing Question 25: 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

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temporal resolution