Data Acquisition Flashcards
Shifting the center of a sagittal image requires changes to which two data coordinates?
- Y-axis
2. Z-axis
Pitch is defined as the ratio of the table movement to the
Beam width
When the table movement per tube rotation is the same as the beam width, the pitch is equal to 1.
What CT data acquisition mode collects a series of adjacent axial sections
Axial scanning
If the pitch is equal to 1.1, how far is the patient table moving during rotation of the tube
1.1 times the beam width
A CT detector configuration is changed from 0.625 mm x 16 rows to 1.125 mm x 8 rows. The change may result in:
Decreased patient dose
Thinker detector rows require less radiation to produce a quality signal, which allows for a decrease in patient dose. This change will actually decrease the spatial resolution, but the total scan time and beam coverage will stay the same.
During an axial scan, the total amount of anatomical coverage per tube rotation is dependent on which of the following two variables?
- Number of activate detector rows
2. Thickness of activated detector rows
During helical scanning, if the table moves a greater distance than the width of the beam the pitch will be
Greater than 1
When imaging a patient in computed tomography, what portion of the patient is processed for viewing on the technologist’s computer monitor?
Any part of the patient within the display field of view (DFOV)
Which of the following statement accurately describes the orientation of the Z-axis in CT imaging?
- Extends longitudinally through the scanner
2. Represents data coordinates in terms of superior and inferior
What two CT scanning modes activate the x ray tube only while the patient table is stationary?
- Axial scanning
2. Volume scanning
If routine helical scan of the chest is pre-programmed to use 16 rows and a pitch of 1.13, how will the resulting views comprise the scan data?
missing views in the scan data
When the pitch is less than one, how do the resulting views comprise the scan data?
overlapping views in the scan data
What portions of a patient receive radiation exposure during CT scanning?
Any portion of the patient within the scanner gantry
Based on feedback from an American College of Radiology (ACR) site-visit, your imaging department needs to design a new low-dose CT protocol for patients who weigh less than 30 pounds. Which of these detector configurations would be most suited for this protocol?
4 mm x 4 rows
How is anatomical data from the scan field of view (SFOC) used during CT image production?
Data from the SFOV is used for image reconstruction
Which of following statements accurately describes the orientation of the z-axis in CT imaging?
- Extends horizontally across the scanner
2. Represents data coordinates in terms of right and left
Acquisition thickness refers to the:
Thickness of active detector rows
Ct angiography (CTA) imaging of the heart is sometimes performed with the CT scanner in the volume acquisition mode. This means that the
Scan data is acquired in one rotation of the x-ray tube
Which of the following statements regarding the scan field of view (SFOV) are true?
- The SFOV is larger than the display field of view (DFOV)
2. Data in the SFOV is saved on the CT computed system
The sequential acquisition mode is described by
The patient table moves only between x-ray exposure
What Ct scanning mode induce patient motion artifact from several stops and starts of the gantry table during data acquisition?
Axial mode
What portion of the patient can be visualized through the process of the retrospective reconstruction?
only parts of the patient within the scan field of view (SFOV)
The helical acquisition mode is the most common technique used for imaging which three body sections?
- Chest
2, Abdomen - Extremities
Except cranium and virtually exams
During which acquisition mode is the patient table in constant motion?
Helical scanning
A CT scanning protocol is set to use a pitch of 0.79. This will result in:
Overlap in the scan data
What portion of the CT data collected during a scan is saved by the scanner but not reconstructed for viewing
Any portion of the patient within the scan field of view (SFOV), but outside of the display field of view (DFOV)
What CT scanning mode forms a spiral of scan data during imaging?
Helical scanning
The inner rows of a non-uniform detector array have the advantage of:
increased spatial resolution
During what CT acquisition mode dose the patient table move between x-ray exposures?
Axial scanning
The localizer images are used by the technologist to assign which variable of a CT scan?
Display field of view (DFOV)
Increasing the acquisition thickness of a CT scan means:
Combining detector rows together to function as one detector row
Acquiring a z-axis measurement of pathology is possible in which two imaging planes
- Sagittal
2. Coronal
What is the primary reason for decreasing the detector thickness for CT angiography examinations?
Increased spatial resolution
What CT scanning method requires a large detector array with numerous data collection channels?
Volume scanning
What is the relationship between acquisition thickness and spatial resolution?
As acquisition thickness increases, spatial resolution decreases
Helical (spiral) scanning is usually preferred over axial scanning mode for what three reasons?
- decreased scan time
- Improved intravenous (IV) contrast timing
- Improved post-processing
Consider two identical scanning protocols, where one protocol uses a pitch of 0.73 and the other uses a pitch of 0.87. The protocol using a pitch of 0.87 will result in which two of the following differences?
- Decreased scan time
2. Decreased patient dose
