CT
Pitch directly relates to:
- patient dose - volume scanned
The range of CT numbers varies frkm
-1000 to +3000
The smaller the scan field size, the
-better resolution -less risk of motion -faster scan time
The CT console provides the radiographer access to
-data display -the software program -data acquisition
In order for CT X-ray to be measured, it must
-enter the detector -be absorbed by the detector material -be converted to electrical energy as a signal
The CT radiation beam is collimated
-pre-patient and post patient -at the tube exit -at the detector entrance
Compared with conventional computed tomography scanners, slip ring scanners offer the following advantages:
-removal of cable wraparound -elimination of start-stop action -continuous rotation of X-ray tube and minimal interscan delays
The computed tomography number for water is?
0
Which of the following pitch ratios is considered to be oversampling?
0.5-1
Calculate pitch for the following parameters: Couch movement of 10 mm/seconds and slice thickness per 360° rotation of 20mm
0.5:1
Approximately ?? of all head CT generally require intravenous contrast media
50% to 90%
An undesirable feature or density in the CT image not representative of anatomy is an:
Artifact
The reduction of the intensity of a beam of xrays as it passes through the patient is:
Attenuation
Which of the following is best used to describe patient dose in computed tomography?
CTDI & MSAD
The slice thickness in computed tomography is ultimately determined by the:
Collimator width
Who shared the Noble Prize in Medicine and Physiology with Hounsfield for his contributions to the computed tomography technique?
Cormack
The detectors convert the attenuation data into ?? signals
Electrical
True or False: The aperture houses the X-ray tube and the detector array
False
True or False: a pitch greater than 1 will result in an increase dose
False
Fourth generation CT scanners are characterized by:
Fan beam geometry and complete rotation of X-ray tube around a stationary ring of detectors
First generation CT scanned the ?? only
Head
The most recent generation of CT scanners use a ?? motion
Helical
A series of tissue density values that evolved for CT measurements are called ?? units
Hounsfield
Who developed the first clinically useful computed tomography scanner?
Hounsfield
The CTDI dose measurement
Is slice-based
The capability to create accurate reconstruction of patient data into alternative planes is termed:
Multiplanar reconstruction
What controls the actual thickness of the CT slices?
Prepatient collimator
Which of the following chest structures would not be located at the level of the jugular notch?
Pulmonary artery
The localization image produced by CT scanner is technically called an
Scanogram
Which generation of CT scanner used a fan beam and a translate-rotate acquisition pattern?
Second
In which of the following data acquisition methods is a volume of tissue scanned during a single breath hold while the couch moves continuously?
Spirical/helical computed tomography
With computed tomography scanner is based on a fan beam geometry and complete rotation of the X-ray tube and detectors?
Third generation scanner
Computed tomography sections are available as
Transverse, sagittal and coronal
True or False: Artifacts caused by patient motion are reduced with volume CT scanning as compared with earlier generation scanners
True
True or False: the number of shades of gray assigned to a CT image can be controlled by the technologist
True
Which material serves as the baseline for CT numbers?
Water
The gantry of the CT until contains the
X-ray tube
CT scan pitch uses all of the following technical parameters EXCEPT
acquisition mAs
What specifically do the CT detectors measure?
attenuation
The most obvious difference between computed tomography and radiography is that:
computed tomography shows cross-sectional images or transaxial anatomy
Sectional images are obtained from all of the following EXCEPT
conventional radiography
As the pitch increases, the image quality:
decreases
The pitch ratio is expressed as:
distance the table travels during 360 degrees/slice thickness
The CT radiographer usually varies the ?? to control the primary beam.
mA
Electromechanical devices made up of rings and brushes to transmit electrical energy across a rotating interface are called:
slip rings
All of the following apply to CT except:
x-ray film is used as the detector