1 Flashcards
Afterglow
Flash of scintillation subtracted before image reconstruction
Detector rows with various sizes
Adaptive array/ non uniform / hybrid rays
Algorithm
Steps in a specific order to solve problem
Attenuation profile
Attenuation properties that correlate position of rays
Automated inj triggering
2 methods
Test bolus
Bolus triggering
Step and shoot is also called
Axial
Conventional
Serial
Sequence
Back projection
Converting —>attenuation profile—> matrix
Beam pitch
Table movement per rotation % beam width
B blockers
Reduces motion artifact on cardiac CTA images by lowering pts heart rate
Bolus inj
Rapid inj of contrast done by hand or inj system
Bolus phase
What phase is it?
Initial phase that follows iv bolus inj and arterial structures r filled with contrast
Not reaching venous structures
Bolus phase = arterial phase
Bolus triggering
Use contrast bolus to initiate the scan.. Then uses a series of low xrt scans to monitor contrast bolus… Once level is enhanced table moves starting scan
Capture efficiency
Detector obtaining photons passed through patient
1cgy=
1rad
100rads =
1 gy
Clinical information systems
Systems that keep track of clinical data
Clustered scans
Grouping more than one scan in a single breath hold
Compensating filters
Reduce dose to patient and minimize artifacts
Completed stroke / established stroke
Acute episode of interrupted blood flow to the brain
Lasts longer than 24 hrs
Computed tomography dose index
Dose reported to FDA
Cone beam is a what kind of detector
Multidetector row ct system
Cone beam artifact are created how?
The larger the cone beam (detector channels) the more the effect
Artifacts that relate to the cone shaped beam for mdct helical scans
Contiguous
One slice abuts the next
Acquisition scan aka
And meaning
Aka: helical , spiral , volumetric
Means continuously rotating xraytube, constant output, uninterrupted table movement
Low contrast resolution
Objects with similar densities
Convolution
Filter
Ct angiography
How r scans done
Ct techniques used to c arterial and venous vessels thru body
Scans done in helical mode
How does Cupping artifact happen
Results from beam hardening
Data acquisition system (DAS)
Measures the number of photons that strike detector
Converts info to digital signal then sends to computer
Delayed reaction
Contrast reactions that occur btw 1 hr - 1 week
Detector array
Collection of detectors in an arc
Detector pitch
Table movement per rotation time % slice thickness = detector pitch
DAC
digital to analog converters
Changes digital signal back to analog format so that it’s views on monitor
Direct axial plane
Positioning pt in specific position
Explain direct axial plane for foot
Plane parallel to plantar surface of foot
Display field of view
Section of info for display on image
Display processor
Assigns a group of HU to each shade if gray
Double contrast technique
Contrast and air out in joint space arthrography
Edge gradient effect
Irregularly shaped obj that hve a pronounced difference in density frm surrounding tissue
Streak or shading
Effective dies is written as
SV or rem
Ebonics stroke
Ischemic stroke
A traveling particle that eventually become lodged
Embolism
Clot within vascular system that detaches frm original site
Equilibrium phase
Delayed phase
Phase of tissue enhancement after the iv inj of contrast media
Begins as early as 2 min after bolus phase or drip infusion
Equil phase is emptied into arteries and and soaked by organs
Excretory phase
Renal enhancement happens 3 min after iv
Fan beam
Is used on single row detectors
Helical interpolation methods
To tke slant and burr out if helical image
Hepatic arterial phase
First phase
15-29 seconds after bolus material
High contrast resolution and
Aka
A.k.a. spatial resolution a.k.a. detail resolution
The images seen as two separate forms.
High-frequency generator
Produces high-voltage and transmits it to the x-ray tube
Hi osmolality contrast media a.k.a. HOCM
It’s a higher osmolality agent
HR CT high-resolution CT
CT of the chest is a technique used for assessment of lung parenchyma in patients with diffuse lung disease i.e. fibrosis and emphysema
Huber needle
Non-coring hook used to access implantable port
Hybrid arrays also called what and what are they
Detector rows variable widths and sizes
a. k.a. adaptive
a. k.a. nonuniform arrays
Hyperosmolar
Great number of particles in solution
Hypertonic
Great number of particles in solution
Idiosyncratic reactions
Unexplained reactions largely unpredictable, occurs within an hour of contrast administration, not related to delves.
Image data
Once computer has processed raw data assigning one HU value to each pixel
What is Raw data used for
raw data is used and then image reconstruction takes place
Image reformation? Image formation is also called what?
Image reformation is stacked across slices
generates an image in a plane orientation different from prospective image
a.k.a. image rendering
Image rendering
an image that is used to stack of cross-sectional slices and generates an image and a plane orientation different from prospective image
a.k.a. imagery formation
Input device
Computer hardware design to input information into the computer examples keyboard, mouse, plasma screen, CT detector.
Ischemic heart disease
One plaque builds up in coronary arteries
Isotropic
Equal in all directions
Iso tonic
Not having the same number of particles in a solution compared to blood
example iso tonic the word not in tonic
KV P the defines what
Quality of the beam how penetrating the beam is
MAS
Amount radiation
Kinetic energy
Energy in motion
Line pairs Phantom
Phantom used to measure spatial resolution
It appears as closely spaced metal strips embedded
Linear attenuation coefficient
Amount of x-ray beam scattered or absorbed per thickness
Linear interpolation
Unknown point falls along a straight line between two known points
Metformin therapy
Given to non insulation dependent diabetics
Negative contrast agents
Contrast agent of lower density example: air or carbon dioxide.
Nephrogram phase
Renal enhancement that follows corticomedullary phase happens 100-120 seconds after IV
Nonequilibrium phase
Follow the bullets phase contrast brighter in the arteries ,parenchyma , and veins
Starts one minute after bolus injection
AKA Venus phase
Nonuniform arrays
Nonuniform arrays a.k.a.’s
Detector rows with variable widths and sizes
A.k.a. adaptive of AKA hybrid arrays
Partial volume artifact
Artifacts when the object is not appear all views
Unit of absorbed dose?
RAD’s radiation absorbed dose
Quantum noise and quantum mottle
Insufficient number of photons are detected
Inversely proportional to image and noise. Image decreases noise increases the smaller the image gets the more noisy will see
Positive contrast agents
two examples?
Contrast agents that are of higher density example barium or iodine
Portal venous phase
Enhancement that follows hepatic arterial phase
Begins at 60 to 70 seconds after IV
Pixel
Picture element two-dimensional
Pitch formula
Table speed to slice thickness. The find is the travel distance of the CT scan table her 360° rotation of the x-ray tube divided by the X x-ray beam I’m collimation with
Peripherally inserted central catheters (PICC)
Long catheter inserted through a large vein of the upper arm located in the lower third of day S BC
Roentgen R
X-ray exposure in air
Scanfield of view SFOV
Scanned area of images where raw data is acquired
Ray sum
Detector senses Ray knows how much being attenuated
Scan parameters
Factors controlled by operator these factors are MAs, scan time, slice thickness, Silverview, reconstruction algorithm, and kv. Helical scans operator has choice of pitch.
Segmentation errors
Reformatted image one important vessels are inadvertently edited out
Seivert
Quality factor added to radiation dose new quantity is called dose equivalent
Slice misregistration
When patient breaths differently with each accusation information maybe missed due to this effect creates an incorrect anatomic position
Slice sensitivity profile
Slice thickness represented on ct image opposed to the size selected by the collimator
Slice thickness accuracy
Accuracy of slice thinkness selected by operator vs. width of collimator opening
Slice thinkness blooming
Slick thickness on imager wider than what selected
Slip rings
Brushlike apparatus providing continuous electrical power
Allows frame to continuously rotate
Eliminating need to straighten cables
Spatial resolution
Separate smll obj that are close together
Spatial resolution is what kind of contrast
High contrast resolution
Split bolus
Contrast inj techniques
Total dose is split in half
1st dose is given
Delay 2 min ( allows time for structures that are slower to enhance to b opacified)..
2nd bolus given containing remaining contrast
Scanning is initiated soon after the second inj is complete ( 2nd inj fully opacify the vessels )
Mild side effects
Heat
Nausea
Mild flushing
Test bolus
Scan delay administrating contrast
Performing trials scans to determine length of time frm inj to peak contrast enhancement ie aorta
Third generation design
Produces fan shaped beam
Transient ischemic attack
TIA
Reversible episode tiny emboli lodged in artery
Aliasing/ undersampling
Inaccuracies related to sharp edges and small objects
View
Complete set of Ray sums
When do windmill artifacts.
MDCT HELICAL SYSTEMS
