Computed Tomography- Test 4 || 100% Valid Solutions.
Selectable Scan Factors correct answers 1. Scan Field of View
2. Display Field of View
3. Matrix Size
4. Slice Thickness
5. Reconstruction Algorithm
6. Scan Time & Rotation
7. Radiographic Tube Output
8. Region of Interest
9. Magnification
10. Focal Spot Size and Tube Geometry
11. Table Increment
12. Pitch
Scan Field of View (FOV) or.. Reconstruction Circle correct answers -is a circular region from
which the transmission measurements are recorded during scanning
-during data collection & image reconstruction, a matrix is placed over the scan FOV to cover
the slice to be imaged
-a technologist can select the FOV appropriate to the examination
Display Field of View (DFOV) correct answers -is the real dimensions of a view (width &
height) with reference to the RAS (right, anterior, superior) coordinates.
-the DFOV can be equal to or less than the scan FOV
Matrix Size correct answers -is the predetermined at 512 x 512 on current equipment
-matrix size is sometimes referred to as the FOV
-as the images become larger, they require more processing time and more storage space
Slice Thickness correct answers -should be adapted to the area of interest
-the number of millimeters (thickness) of anatomy penetrated by the x-ray beam
-determined by the collimation of the x-ray beam and partially determined by the focal spot
-affects anatomical coverage, image noise, resolution, and dose
-image noise is decreased with thicker slices
, -resolution is reduced with thicker slices (multiple tissues of different densities are superimposed
within the same slice and displayed as a single pixel)
-spatial resolution is better with thinner slices
********
-Routine Head: 2.5 to 5 mm slices
-C-Spine: 1 to 3 mm slices
-Lumbar: 3 to 5 mm slices
Reconstruction Algorithm correct answers -is a computer adapted mathematical calculation
applied to raw data during image reconstruction
-Basic Algorithm (used for brain, neck, and spine are):
*standard
*bone
*detail
-Standard Algorithm is chosen for most soft tissue imaging. Ex. brain and intervertebral discs
because it provides good spatial contrast
-Detail Algorithm is used for studying the soft tissues of the neck
*it increases edge definition of similar tissues
-Bone Algorithm is used to increase the sharpness of the bony detail
*optimizes spatial resolution; contrast resolution is poor
Scan Time and Rotation correct answers -refer to the duration of the scan
-the scan time depends on the patient's respiratory condition
-increasing the scan rotation time will result in better resolution because each image is generated
from more projections
-longer scan times can offer tube cooling but can increase pt motion
Radiographic Tube Output correct answers -AEC uses a technique referred to as Automatic Tube
Current Modulation (ATCM) to control the dose to the pt while maintaining constant image
quality regardless of pt size and tissue attenuation differences
-dose is directly proportional to the mA
-ATCM automatically controls the mA in 2 directions of the patient (x-y axis and z axis)
-Patient Coordinate System: Supine position
*z-axis extends along the patient table and the long axis of the patients body
Selectable Scan Factors correct answers 1. Scan Field of View
2. Display Field of View
3. Matrix Size
4. Slice Thickness
5. Reconstruction Algorithm
6. Scan Time & Rotation
7. Radiographic Tube Output
8. Region of Interest
9. Magnification
10. Focal Spot Size and Tube Geometry
11. Table Increment
12. Pitch
Scan Field of View (FOV) or.. Reconstruction Circle correct answers -is a circular region from
which the transmission measurements are recorded during scanning
-during data collection & image reconstruction, a matrix is placed over the scan FOV to cover
the slice to be imaged
-a technologist can select the FOV appropriate to the examination
Display Field of View (DFOV) correct answers -is the real dimensions of a view (width &
height) with reference to the RAS (right, anterior, superior) coordinates.
-the DFOV can be equal to or less than the scan FOV
Matrix Size correct answers -is the predetermined at 512 x 512 on current equipment
-matrix size is sometimes referred to as the FOV
-as the images become larger, they require more processing time and more storage space
Slice Thickness correct answers -should be adapted to the area of interest
-the number of millimeters (thickness) of anatomy penetrated by the x-ray beam
-determined by the collimation of the x-ray beam and partially determined by the focal spot
-affects anatomical coverage, image noise, resolution, and dose
-image noise is decreased with thicker slices
, -resolution is reduced with thicker slices (multiple tissues of different densities are superimposed
within the same slice and displayed as a single pixel)
-spatial resolution is better with thinner slices
********
-Routine Head: 2.5 to 5 mm slices
-C-Spine: 1 to 3 mm slices
-Lumbar: 3 to 5 mm slices
Reconstruction Algorithm correct answers -is a computer adapted mathematical calculation
applied to raw data during image reconstruction
-Basic Algorithm (used for brain, neck, and spine are):
*standard
*bone
*detail
-Standard Algorithm is chosen for most soft tissue imaging. Ex. brain and intervertebral discs
because it provides good spatial contrast
-Detail Algorithm is used for studying the soft tissues of the neck
*it increases edge definition of similar tissues
-Bone Algorithm is used to increase the sharpness of the bony detail
*optimizes spatial resolution; contrast resolution is poor
Scan Time and Rotation correct answers -refer to the duration of the scan
-the scan time depends on the patient's respiratory condition
-increasing the scan rotation time will result in better resolution because each image is generated
from more projections
-longer scan times can offer tube cooling but can increase pt motion
Radiographic Tube Output correct answers -AEC uses a technique referred to as Automatic Tube
Current Modulation (ATCM) to control the dose to the pt while maintaining constant image
quality regardless of pt size and tissue attenuation differences
-dose is directly proportional to the mA
-ATCM automatically controls the mA in 2 directions of the patient (x-y axis and z axis)
-Patient Coordinate System: Supine position
*z-axis extends along the patient table and the long axis of the patients body
