Image Production Flashcards
For a given ct acquisition the calculated mas applied to each reconstruction slice may be referred to as
Effective mas
When using a 3rd generation ct scanner it is important that reference detectors positioned at the peripheral portions of the detector array be exposed to
Unattenuated radiation
What two scientists got the Nobel prize in 1979
Hounsfield and cormack
Which of the following terms accurately describes the type of Xray beam used in a 3rd gen ct scanner
Fan beam
Decreased mas will do what to patient radiation dose
Decrease
In MSCT the beam pitch is equal to the table feed per rotation divided by the
Total collimation
In an MSCT system the detector array is composed of multiple rows of individual detector elements along the
Z-axis
The type of MSCT detector array that contains midline narrow elements flanked by wider detectors is called
Hybrid array
The process of scanning a phantom device of known density to improve the accuracy of CT attenuation measurement is
Calibration
Which of the following types of image reconstruction was used in the first prototype ct scanner
Iterative technique
Ct images that have been reconstructed from a portion of the data acquisition process in the hopes of reducing pt motion artifacts are called
Segmented images
As a solid state ct detector measures transmitted radiation it emits a proportional response in the form of
Analog signal
During a ct scan each sample of ray sum measurements made by the data acquisition system DAS is called
View
The ability of an object to attenuate the Xray beam is assigned a value known as
Linear attenuation coefficient
The primary advantage of an isotopic MDCT data set is
High quality multiplanar reformations
The technique that allows the user to select the range of pixel values used in a 3D ct reformation is termed
Thresholding
—— is part of 3D image processing
Surface rendering
How much oral contrast
750-1500 mls
C spine images require slice thickness of
1mm
—-mm required to create lower extremity reformats
2mm
Type —— dissections affect the ascending aorta
A
What is a coagulopatgy bleed
Head bleed caused from blood thinners
What causes a amyloid headache bleed
Abnormal buildup of protein A disease that may be heritage and causes person to have spontaneous small vessels to burst
What is the main part of the CT’s computer system
Array processor
What is pitch
The distance the table travels during 1 revolution
Pitch ratio is
When the tube revolution equals the slice thickness is 1:1
Filament size has an impact on
Special resolution
—- is the ability to distinguish between objects that differ in density
Special resolution
—- detectors are used used primarily in 3rd gen scanners
Gas ionization
Voxel size depends on
Slice thickness (z axis)
MIP uses
Volume rendering
Volume rendering uses data from a
2d projection to produce a 3D image
A volume of tissue or volume element is a
Voxel
The z axis is
Longitudinal
Perfect image has a
1.0
Imperfect image has
0.1
The Y axis is the
AP image or up and down
The frequency response to create an image
MTF
HU number for hepatic cysts
0-20
HU number for normal brain
15-22
HU for muscle
50
HU for air
-600 to -1000
PET scans measure
The uptake of PDG
— area of the pt that is exposed to radiation
Dose profile
FWHM is a measure of
Effective section width
Accounts for dose in the X Y and Z axis
CTWI vol
Doesn’t matter if scan is spiral or helical
CTDI W
Ct filament size
0.5-1.2
Grouping together detector channels
Binning
To calculate CTDI the acquisition must
Be contiguous
The P way correlates to
Atrial systole
The T wave correlates to
Cardiac diastole
The QRS complex correlates to
The ventricular systole
What is DLP
The total amount of exposure for an exam
Typical kv for ct scanners
60-100
Term to describe X-rays ability to ionize a volume of air
Exposure
Exposure is measured in
Roentgens
Amount of Xray energy absorbed in a unit of mass
Absorbed dose
Absorbed dose is measured in
Grays
Accounts for the type of tissue that radiation is deposited in
Effective dose
Effective dose is measured in
Sev
Approximate measure of dose received in a single ct slice
CTDI
CTDI100 corresponds to
Pencil ionization chamber
As pitch increases the dose per section
Decreases (CTDI VOL)
What is displayed in all ct reports
DLP and CTDI
Window width is the ———————————————
Range of ct numbers with in an image
Absorbed dose is measured in
Gray
Dose profile is the
Area of the pt that’s exposed to radiation
MA is always increased to produce
Thinner images
The peritoneum contains
Stomach Small bowel Small portion of duodenum Jejunum and ileum Transverse colon Liver Gb spleen Ovaries
What is in the retroperitoneum
Duodenum Pancreas Adrenals Kidneys Ureturs Bladder Aorta. IVC prostate uterus
What is in the mediastinum
Heart. Greater vessels Esophagus.
Trachea. Phrenic and cardiac nerves. Thoracic duct. Thymus. Central chest lymph nodes
What is spondylosis
Age related wear and tear of disk
L spine
What is spondylolysis
Occurs to the pars
What is spondylolisthesis
One vertebral body slips over another
A ring artifact in a ct head scan would most likely be caused by
A detector malfunction
The stair step artifact of 3D aortic/heart images most likely is caused by
Not enough overlap