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Advanced Modalities

Computed Tomography

QuestionAnswer
CT eliminates ____________ encountered in X-ray by passing a __________ __________ ________ through a part at many different __________. Superimposition; Tightly collimated beam; Angles
CT creates a _________-__________ ___________ plane of any part of the body. Cross-sectional tomographic
The CT scan is obtained by an __________ _________ rotating around a body part. X-ray Tube
Exit ___________ is measured by a _____________ assembly. Radiation; detector
The __________ assembly sends the measured __________ __________ information or ___________ data to the computer. Detector; Exit Radiation; Primary
CT has improved ___________ resolution due to the reduction in ___________ radiation. Contrast; scatter
The newest method of data acquisition from CT is __________/__________ CT. Spiral/Helical
With Spiral/Helical CT the __________ rotates continuously while the table moves through the aperature at the same time. Gantry
_________ _________ technology makes continuous rotation of the tube possible. Slip-ring
__________ _________ forms a spiral path from which raw data is obtained. Continuous motion
Multi-slice gathers _____ slices in ______ mS. 4; 350
The significance of Spiral/Helical CT is that it scans a ___________ of tissue rather than __________ _________. Volume; Individual slices
3 Advantages of Spiral/Helical CT: 1)Respiratory motion is minimized; 2)Useful for detecting small lesions 3)Useful for noncooperative, combative, trauma and pediatric patients.
The technical aspects of CT is that it provides information on _________ relationships and ___________ characteristics. Positional; Tissue
The radiation __________ measures exit radiation and coverts it to an _____________ ___________ and sends it to the computer. Detector; Electronic signal
The Raw Data is the __________ __________ ______________ values. Measured X-ray transmission
The computer ____________ the signal received which is actually assigning a ___________ _________ to each signal. Digitizes; Whole number
The Matrix is an array of ___________ arranged in a ___________ of ________ and ________. Numbers; Grid; Rows and columns
A _________ is a single square or picture element within a matrix. Pixel
The __________ is the volume element of the digital image and matrix; It is the product of the __________ area and _________ ___________. Voxel; Pixel and slice thickness
Each __________ represents a piece of anatomy and is displayed on the image monitor as a dot of light in one of the shades of gray. Pixel
The __________ the pixel, the ____________ the piece of anatomy being represented and the better the __________ _________ __________ will be. Smaller; Smaller; Image Quality Resolution
Each pixel is assigned a number that is related to the ___________ _____________ __________ of the tissue within each __________. Linear Attenuation Coefficient; Voxel
The numbers assigned to each pixel are called ____ numbers or _____________ Units. CT numbers or Hounsfield Units
Hounsfield numbers of tissue varies according to the ______________ of that tissue. Density
More dense tissue have __________ numbers and less dense tissue have ___________ numbers. Higher numbers; Lower numbers
Hounsfield numbers range between _____________ and _____________ and has recently been expanded to ____________ for bone imaging. -1000 HU to +1000 HU; +4000 HU
The average Hounsfield units for the following: (1) Air; (2) Water; (3) Blood; (4)Muscle; (5) Bone (1)Air: -1000; (2) Water: 0; (3) Blood: +20 to +50; (4) Muscle +35 to +50; (5) Bone: +150 to +1000
Higher HU numbers appear ___________ and lower HU numbers appear ___________. Lighter; Darker
___________ determines the amount of data displayed on the monitor. Field of View (FOV)
The _________ _________ and the _________________ determines the pixel size. Matrix size; Displayed FOV
Pixel Size = _________/_________ DFOV/Matrix Size
_____________ is the ability of an imaging system to differientiate among objects. Resolution
___________ is the reference material for CT because: (1) __________ in the body; (2) has ___________ __________; (3) and is assigned an arbitrary value of ___________. Water; (1) Abundant; (2) Uniform Density; (3) Arbitrary value of 0
__________ CT numbers are more dense than water and ___________ CT numbers are less dense than waater. Positive; Negative
CT numbers scale range from __________ for air to ___________ for dense bone. -1000; +14,000
The __________ _________ on the display corresponds to the CT number for that pixel. Gray level
__________ ____________ allows the technologist to alter the _________ of the displayed image by adjusting the window _______ and window _________. Windowing Technique; Contrast; Level; Width
Windowing is ________-_______ mapping. Gray-Level
The Window _________ is the range of CT numbers used to map signals into shades of gray and establishes the __________ of gray levels displayed. Width; number
Narrow Window = _________ shades of gray and __________ contrast (or _______-scale contrast) Fewer; Higher; Short-scale
A Wide Window = ___________ shades of gray and __________ contrast (or ________ scale contrast) Greater; Lower; Long-scale
___________ ___________ determines the midpoint of range of the gray range displayed. Window Level
The Window Level should be set to the CT number of the __________ of interest. tissue
The increments that the table moves through the gantry is termed ___________. Indexing
Contrast Media is used to help distinguish _____________ anatomy from ___________ and increases the visibility of _____________ ______________. Normal anatomy; Pathology; Disease Processes
Contrast media for CT may be administered: (1) (2) (3) (1) IV; (2) Orally; (3) Rectally
MPR is ____________ ____________ and is the ability to reconstruct ___________ images into __________, __________, or ___________ body planes without additional radiation to the patient. Multiplaner Recontruction; Axial; Sagittal; Coronal; Oblique
The initial introduction of _________ raised concerns that CT would become obsolete. MRI
CT demonstrates _________ better than MRI. MRI demonstrates _____________ better than CT. CT demonstrates bone better than MRI. MRI demonstrates Soft Tissue better than CT.
Created by: foster1317