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CT > Image Production > Flashcards

Image Production Flashcards

1
Q
  1. 5 Major Components of CT system: (Broad)
  2. Imaging System consist of:
A
  1. Imaging system, CT computer & processing system, Image display storage and communication, CT control console & PACS
  2. xray tube, generators, collimator, filters, detectors, detector electronics
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2
Q
  1. What is the CT control consol?
    - What does it consist of?
  2. What is the CT gantry?
    - What does it consist of?
A
  1. Integrated console that gives tech full control of system
    - Keyboard & Mouse
    - Touch Panel
    - Window Controls (width & level)
    - Optical Disc Drive
    - Control Functions (auto archive, auto window & auto voice)
  2. Mounted framework surrounds patient. Houses the following:
    - xray generator
    - xray tube
    - slip rings
    - collimators
    - detectors
    - DAS (Data Acquisition System)
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3
Q
  1. What does DAS stand for?
    - Where is it?
  2. What is Gantry Aperture?
    - Typical Range? Why?
  3. Typical Gantry Tilt Range?
    - What does this help?
A
  1. Data Aquisition System
    - In gantry
  2. Opening where patient is positioned
    - 70cm = allows approach patient from front or back of gantry
  3. 12-30 degrees
    - Help if patient can’t position correctly
    - Aid in aiming / containing beam
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4
Q
  1. Patient table typically made of?
    - Why?
  2. How can the CT table move?
    - Why?
  3. What is Optical Disk Drive?
    - Where located?
A
  1. Carbon fibers
    - Low radiation absorption & Durable
  2. Up/Down = help patient on and off
    - in & out = acquire images
  3. Erasable storage
    - CT control console
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5
Q
  1. Current CT scanners use what type of generator?
    - Where is it located?
  2. What does the generator consist of?
    - What is its function?
  3. Typical Range for generator?
    - Max kV & mA?
A
  1. High frequency
    - Housed In gantry
  2. High voltage transformer
    - Converts low frequency voltage alternating current into high frequency, high voltage current
  3. 60-100 killowatts
    - 140 kv 8 800 mA
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6
Q
  1. Current CT Generator converts ________ into _________.
  2. They do this by using a _________, housed in the _________.
  3. Two primary types of radiation produced in CT x-ray tube:
A
  1. Low frequency, Low voltage alternating current into high frequency high voltage current
  2. Transformer Inside the Generator, Housed inside Gantry
  3. Characteristic
    - Bremstrahlung
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7
Q
  1. Explain Characteristic Radiation?
    - Where does this take place?
  2. Explain Bremstraughl Radiation?
    - Where does this take place?
A
  1. When outer shell electron interacts with inner shell electron
    - Outter Shell electron fills inner shell void, Due to outter shell moving to inner shell, creates Characteristic Radiation
    - IN XRAY TUBE
  2. Electron is slowed through nucleus
    - As electron moves through nucleus, it loses some or all its energy’s Resulting in Brems Radiation
    - IN XRAY TUNE
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8
Q
  1. How many filament size options are in CT?
    - What do they Alter?
  2. How do you select filament?
  3. Why do you warm up CT xray tube?
A
  1. 2 filament sizes
    - Alter focal spot size
  2. Controlled through selection of mA & Scan FOV
  3. Ensure xray functions properly and avoid damage to tube
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9
Q
  1. Typical Filament size Range:
  2. Typical focal spot used in CT:
  3. Explain how above Focal Spot works
    - What does it result in?
    - Why is it beneficial?
A
  1. 0.5 - 1.2 mm
  2. Flying Focal Spot
  3. Beam of electrons guided to 2 separate areas on anode. The beam alternates between the 2 focal spots which result in 2 sources of radiation
    - Improves spatial & temporal resolution
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10
Q
  1. What do Modern CT xray tubes require to achieve high performance?
  2. What is the CT tube warm up for?
  3. Benefits of warming tube:
A
  1. Ability absorb and dissipate high amounts heat quickly
    - Small size & light weight = high rotation speed
    - Stable & Reliable = Long Lasting
  2. Gradually prepares tube for higher kV & mA usage
  3. Increase tube lifespan,
    decrease risk malfunction
    reduce scanner downtime
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11
Q
  1. What is required in CT xray tube?
  2. mA ranges:
    - kV ranges:
  3. Modern CT scanner use ________ & _______ to reduce patient dose.
    - How?
A
  1. Withstand high heats & cool quickly
  2. 30mA - 800m
    - 70kV - 150kV
  3. utilize Automatic Tube Current Modulation (ATCM) and Automatic exposure control (AEC).
    - ATCM optimizes the radiation dose that a patient receives based upon their size and the different densities of the tissues being imaged.
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12
Q
  1. ATCM stands for?
    - Purpose/Function?
  2. What does filtration do?
    - Whys this important?
  3. What is another name for above?
    - What can it result in?
A
  1. Automatic Tube Current Modulation (ATCM)
    - ATCM optimizes the radiation dose that a patient receives based upon their size and the different densities of the tissues being imaged.
  2. Remove long wave / low energy photons
    - These do not contribute to image formation, removing them lowers patient dose
  3. Beam hardening
    - Image artifacts
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13
Q
  1. What does hardening beam mean?
    - What does this?
  2. Inherit filtration is how thick?
    - Made of?
  3. Added Filtration consist of _______ or ______ sheets made of _______.
    - Size Range:
A
  1. removing low energy / long wavelength photons
    - Filtration in xray tube
  2. 3mm
    - Aluminum equivalent
  3. Added = flat or shaped copper sheets
    - .1 to ,4 mm
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14
Q
  1. Inherit vs Added Filtration:
  2. CT beam is __________, with _______ energy.
  3. What does filtration compensate for?
A
  1. Inherit = in Tube, Aluminum, 3mm Aluminum
    - Added = Shaped or Flat Copper Sheets, .1 - .4 mm
  2. Polychroratic beam
    - Different energies
  3. Varying photon energies
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15
Q
  1. CT beam is polychromatic, meaning what?
  2. What does filtration do?
    - Produces what?
  3. How dose filtration do this?
    - Results in:
A
  1. Varying energies
  2. Shapes energy of beam
    - Produce uniform xray beam
  3. Absorbing the long wavelength/lower energy photons that do not contribute to the image, but increase the patient’s dose.
  • increase in the average energy of the x-ray beam, and a hardened beam.
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16
Q

Filtration absorbs ____(1)_____, which results in a ____(2)_____ beam. This results in a lower ____(3)_____, & higher ____(4)_____. Filtration may result in ___(5)____.

A
  1. long wave, low energy photons
  2. hardened beam
  3. lower patient dose
  4. Higher average beam energy
  5. Beam Hardening Artifact
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17
Q
  1. _______ has been introduced to compensate for differences in beam paths through an object.
  2. This is important so that the beam
    _______________________
  3. What is desired for image production, low energy / long wave photons or high energy, short wave photons?
A
  1. Bowtie filter
  2. Comes in contrast w detector more evenly
  3. Short / High
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18
Q
  1. What is bow tie filter?
    - What is its function?
  2. What restricts beam to anatomy area of interest?
  3. CT beam is ________, meaning it has varying energies.
A
  1. Filter that compensates for different beam paths through object, and allow for uniform exposure to detector
  2. Collimation
  3. Polychromatic
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19
Q
  1. Collimation function:
    - Collimation effects:
  2. 2 Main Types Collimation:
  3. What/Where is Initial Collimator?
A
  1. RESTRICT BEAM TO ROI
    - Patient dose & Image quality
  2. Pre patient & Post patient
  3. Tube Housing = Initial Prepatient Collimator
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20
Q
  1. ______ acts an initial collimator in prepatient collimation.
  2. _______ shapes primary beam into ________.
  3. Prepatient occurs where?
    - Also know as?
A
  1. Tube housing
  2. Tube Aperture
    - Fan or cone
  3. Occurs prior to beam passing through tube housing
    - precollimation
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21
Q
  1. What is tube aperture?
    - Function?
  2. What is purpose of postpatient collimation?
  3. Where does postpatient collimation take place,
A
  1. Precollimator in tube that shapes primary beam into cones or flat shape
  2. Remove unwanted scatter from reaching detector
  3. After beam passes through patient but before reaching detector
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22
Q
  1. Prepatient vs postpatient collimation:
  2. Xray beam is collimated by ________ to ensure ___________.
  3. What does Precollimators determine?
    - How?
A
  1. Pre = in tube housing / shapes beam, occurs before reaching patient
    Post = After passing patient but before reaching detector
  2. precollimator to ensure beam falls on entire multirow detector
  3. Determine slice thickness
    - By forming beam width
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23
Q
  1. Which collimation determines slice thickness?
    - How?
  2. How is xray beam matched to detectors?
  3. As xray beam width increases, scatter ________.
A
  1. Precollimators
    - By forming beam width
  2. Xray beam divided into multiple beams to match detector array
  3. Increase width = increase scatter
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24
Q
  1. Why is xray beam divided?
  2. What’s relationship between beam width & scatter?
  3. How is scatter minimized before reaching detector?
A
  1. Match detector array
  2. DIRECT
    - increase one, increases other & decreasing one decreases other
  3. Postcollimators
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25
Q

1 Define Attenuation

  1. What does Attenuation depend on?
  2. What is Beam Geometry?
A
  1. Reduction of intensity of xray beam as it passes an object
  2. Atomic density, Incident object’s atomic number of the absorber
    & energy of incident photon
  3. Shape of beam as it leaves tube housing and strikes detector.
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26
Q
  1. What is the reduction of intensity of xray beam as it passes through an object?
  2. Relationship between Beam Width & Amount of Detector Rows?
    - Why?
  3. What does MDCT stand for?
A
  1. Attenuation
  2. As number of detector rows increase, beam becomes wider to cover detector array
  3. Multi Detector CT Scanners
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27
Q
  1. MDCT utilize what type of beam during image acquisition?
    - Why?
  2. CT detectors are responsible for measuring _____A_____ and converting it into an ___B_____. The ____C_____ is then emitted by the ___D____, and is equivalent to the ____E____ that struck the detector.
A
  1. Cone Beam
    - Expose entire row of detectors evenly to radiation
  2. A. measuring the transmitted radiation
    B. converting to electronic signal.
    C. electronic signal
    D. the detector
    E. transmitted radiation
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28
Q
  1. Detectors convert ____ to ______
    - Is it equal conversion or does it gain/lose energy?
  2. Why is it important for Detectors to have high efficiency?
  3. What is absorption efficiency?
A
  1. Radiation to electronic signal
    - Equivalent
  2. Must be efficient at absorbing x-rays & converting to electric signal
  3. Number photons absorbed by Detector
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29
Q
  1. What is capture efficiency?
  2. What does detector stability mean?
  3. What does an unstable detector require?
A
  1. Efficiency detectors obtain photons from patient
  2. Steadiness of detectors response to transmitted x-rays
  3. Frequent calibrations
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30
Q
  1. Two important types of detector efficiencies?
    - What are the differences
  2. What is detector response time?
  3. What should response time be for detector?
    - What can occur if it’s not?
A
  1. Absorption Efficiency = number photons absorbed in detector
    - Capture Efficiency = Detector ability obtain photons through patient
  2. Speed in which detector detects xray event and recover to detect another event
  3. Short response time
    - If not, “afterglow” can occur
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31
Q
  1. What is afterglow?
    - Is this desired?
    - When does this occur?
  2. What is Dynamic Range?
  3. Two types of detectors:
A
  1. Persistence of xray event after radiation has been turned off
    - Should be avoided
    - Occurs if response time isn’t short
  2. Ability of detector to detect wide arrange of exposures & differentiate between them
  3. Gas Ionization Detectors & Scintilators
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32
Q
  1. What do Gas Ionization Detectors consist of?
    - How do they work?
  2. Relationship between xray energy & signal created?
  3. What generation uses this type of detector?
A
  1. Small high pressure chambers of xenon gas.
    - X-ray photons interact with xenon gas which creates a small electrical signal
  2. DIRECT
    (The higher energy of the x-ray interaction, the larger the created signal will be)
  3. primarily in third generation CT scanners.
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33
Q
  1. What do Scintelation Detectors consist of?
  2. How does this detector work?
    - Is the output more, equal or less than input?
  3. What scanner typically uses this detector?
A
  1. Solid state detectors that consist of a scintillation crystal, coupled with a photodiode tube.
  2. The crystal emits light energy that is equivalent to the x-ray that it encounters.
    - The light is measured by the photodiode and is then converted into an electrical signal.
  3. Modern MSCT scanners all use solid state detectors consisting of scintillating crystal material
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34
Q

Scintillation detectors are ___1___ detectors that consist of a ___2____, coupled with a ____3____ tube. The ___4___ emits ___5___ energy that is equivalent to the ___6____ that it encounters.
The ____7___ is measured by the ___8____ and is then converted into an ____9_____.

A
  1. solid state detectors
  2. scintillation crystal
  3. photodiode tube.
  4. Crystal
  5. light energy
  6. x-ray that it encounters.
  7. light is
  8. photodiode
    9.electrical signal.
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35
Q
  1. Three primary categories of CT Detectors:
  2. In MSCT, what determines number of slices acquired and the thickness of the slices?
  3. What is Detector Collimation?
A
  1. Uniform Matrix Array, Adaptive Array & Hybrid Array
  2. Detector configuration used.
  3. Setting the desired thickness of slices to be acquired
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36
Q
  1. Describe Differences:
    A. Uniform Matrix Detector
    B. Adaptive Array Detector
    C. Hybrid Array Detector
  2. Number of Channels scanner has determines what?
  3. Setting Desired Slice Thickness To Be Acquired is known as:
A
  1. A. Uniform matrix array = channels that are equal in all dimensions.
    -B. Adaptive array = channels that are not equal, and have different sizes.
    -C. Hybrid array = channels of two different sizes.
  2. Number of sections acquired per gantry rotation
  3. Detector Collimation
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37
Q
  1. Detector with equal dimension channels?
  2. How does Beam collimation impact section width?
    - Beam must be what?
  3. What detector has channels not equal in dimensions
A
  1. Uniform Array
  2. Indirectly impacts section width
    - Beam must be wide enough to cover the entire section of channels active during each gantry revolution.
  3. Adaptive Array Detector
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38
Q
  1. What is Detector Configuration?
  2. Which Detector has 2 different channel sizes?
  3. If a detector channel is 1.25mm thick, each channel will produce an image how big?
A
  1. Describes the number of data channels active and the effective section thickness.
  2. Hybrid Array Detector
  3. Each channel will produce a 1.25mm image
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39
Q
  1. What describes the number of data channels active and the effective section thickness?
  2. Detector Channel size is ______ to Image Produced. (Smaller, Equal to, or Bigger than)
  3. When channels are group together, what can occur?
A
  1. Detector configuration
  2. Equal to
    - 1.25mm channel thickness = 1.25mm image produced
  3. Can form images of different thickness
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40
Q
  1. When grouped together,
    - Two 1.25mm channels =
    - Four 1.25mm channels =
  2. What is the term for grouping together detector channels to form a section width.
  3. The smallest slice thickness possible is determined by:
A
  1. Two 1.5mm = 2.5mm slice
    Four 1.25mm = 5.0mm slice
  2. Binning
  3. Determined by the smallest single detector element or channel.
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41
Q
  1. What is Bining?
  2. Smallest slice thickness is determined by smallest single detector element / channel, except in:
  3. Why is this the exception?
A
  1. term used to describe grouping together detector channels to form a section width.
  2. Except in adaptive arrays.
  3. In adaptive arrays, the x-ray beam can be adjusted so that only the inner half of two detector elements are exposed to the x-ray beam.
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42
Q
  1. What are Adaptive Arrays able to do that differs from other 2 detectors?
  2. Detector Elements not being used do what?
  3. When is slice thickness selected?
A
  1. Xray beam can be adjusted so only inner half of two detector elements are exposed to xray beam
  2. Switched off
  3. Must be selected prior to scanning & can not be narrowed after acquisition
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43
Q
  1. Can slice thickness be adjusted after acquisition?
  2. Where is The Data Acquisition System is located?
  3. What are the three major functions of Data Acquisition System?
A
  1. Can be widened / grouped together
    - CAN NOT BE NARROWED AFTER
  2. Between the detectors and the computer
  3. Measuring the transmitted radiation beam.
    - Converting the measurements into binary data.
    - Transmitting the binary data to the computer.
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44
Q
  1. What measures transmitted x-rays & converts them into electrical energy?
    - Then what occurs? By what?
  2. What is Logarithmic Conversion?
  3. What occurs when there are not enough incident x-rays measured?
A
  1. Detector
    - Signal is Amplified by the preamplifier.
  2. Process where Transmission measurement data is changed into attenuation and thickness data

3 Artifacts occur within the image.

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45
Q
  1. How is the Logarithmic Conversion carried out?
    - What is sent where?
  2. What does the DAS DO?
  3. What is ADC stand for?
A
  1. By Logarithmic Amplifier
    - Attenuation & Thickness data sent to analog to digital converter (ADC)
  2. Transmits ADC’s data to computer
  3. Analog to Digital Converter
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46
Q
  1. What does the ADC do?
  2. Where does ADC get its data?
  3. When does artifact occur within an image?
A
  1. Converts data into digital values which determine grayscale resolution
  2. From Logarithmic Amplifier
  3. When not enough incident xray is measured
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47
Q
  1. What is required in CT computer?
  2. What is main component of computer system in CT?
    - What is it?
  3. What determines grayscale resolution?
A
  1. Must be able to process large amounts of data in short periods of time
    - Must also have large amounts of storage
    - Must perform multiple tasks at time
  2. Array Processor
    - Dedicated electronic circuit capable of high speed calculations
  3. ADC converting attenuation & thickness data into digital values
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48
Q

Array processor consists of
- What is its function?
1.
2.
3.

A
  1. Multiple Processors & Storage = accommodate high speed data acquisition
  2. Dedicated Image Storage = Allow independent manipulation of data
  3. DICOM Functionality = Communication between equiptment
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49
Q
  1. What is DICOM?
  2. Where does Array processor receives data from?
    - What does it do with this data?
  3. After above occurs, what happens?
A
  1. Digital Imaging & Communication in Medicine / Allows communication between equipment
  2. From computer
    - Completed majority of image processing
  3. Stores images on computer
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50
Q
  • Components of Data Acquisition -
    Detector measures ___A____ & Converts it to ___B____. This is amplified by ____C_____.

____D_____ is changed into ___E____ & ___F____ through process called ___G___. It is carried out by ____H___ & sent to ___I____.

___I____ converts ____J____ into ____K___, which determines ____L____.
___M____ transmits it to ____N____.

___O___ receives ___P____ from __Q__ & completes ____R___.

A

A. transmitted x-rays
B. Electrical Energy
C. Preamplifier
D. Transmission Data
E. Attenuation
F. Thickness Data
G. Logarithmic Conversion
H. Logarithmic Amplifier
I. Analog-Digital-Converter (ADC)
I. ^
J. Attenuation & Thickness Data
K. Digital Values
L. Grayscale Resolution
M. DAS
N. CT Computer
O. Array Processor
P. Digital Data
Q. Computer
R. Processing Image

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51
Q
  1. What happens after array processor completes majority of image processing?
  2. What is Pitch?
  3. What is it used for?
A
  1. Stores images on computer
  2. Distance in mm that CT table moves during one revolution of xray tube / Slice thickness or beam collimation
  3. Calculate Pitch Ration
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52
Q
  1. What is pitch measured in?
  2. What is pitch ratio if the distance the table tracks during one revolution of xray tube is equal to slice thickness or beam collimation?
  3. What pitch is best image quality?
A
  1. mm
  2. 1:1
  3. Pitch of 1
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53
Q
  1. What is pitch ratio?
  2. What results in ratio of 1:1
  3. How can Pitch be adjusted to decrease scan time?
A
  1. Distance table travels during one revolution : Slice thickness or Beam Collimation
  2. Distance Table travels during one revolution of tube equals the slice thickness / beam collimation
  3. Increase Pitch = Extend Area of Coverage = Decrease Scan Time
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54
Q
  1. What does Pitch of less than 1 mean?
    - Patient Dose Is?
  2. What does Pitch of greater than 1 mean?
    - Patient Dose Is?
  3. Relationship between Pitch & Patient Dose?
    - How/Why?
    ** ONLY TRUE IF WHAT?**
A
  1. Pitch Less 1 = Overlapping Slices
    - Higher Patient Dose
  2. Pitch Greater 1 = Gaps between Slices
    - Lower Patient Dose
  3. Inverse (Increase Pitch = Decrease Dose, Decrease Pitch = Increase Dose)
    - Pitch Affects Area Of Coverage & Scan Time
    ** ONLY TRUE IF PITCH IS ADJUSTED AND ALL OTHER FACTORS REMAIN SAME**
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55
Q
  1. Which Pitch Results in overlapping slices?
    - Gap in slices?
  2. What defines beam width?
  3. What is Acquisition Thickness?
    - AKA?
A
  1. Lower than 1 = Overlap
    - Higher than 1 = Gaps
  2. Collimation
  3. Amount of anatomy covered along Z Axis
    - AKA SLICE THICKNESS
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56
Q
  1. What is Z Axis?
    - X Axis?
    - Y Axis?
  2. What is the amount of Anatomy covered along Z-Axis called?
  3. What controls this (above)
A
  1. Z = Beam Width in Longitudinal Axis
    - X = Indicates Width
    - Y = Indicates Height
  2. Acquisition Thickness / Slice Thickness
  3. Collimation of xray beam and detectors
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57
Q
  1. Acquisition Thickness is controlled by:
  2. In single slice CT Scanners, Acquisition Thickness is controlled by:
  3. What Axis is height?
    - Width?
    - Beam Width in Longitudinal Axis?
A
  1. Collimation of BOTH xray beam and detectors
  2. SOLELY by the collimation of xray beam
  3. Height = Y (Think Y Axis is Up&Down)
    Width = X (Think XTRA WIDE)
    Beam Wodth = Z ( Like Long. Length)
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58
Q
  1. What is SFOV stand for?
    - DFOV?
  2. What is SFOV?
    - What controls SFOV?
  3. Typical types of CT SFOV?
A
  1. SFOV = Scan Field of View
    - DFOV = Display Field of View
  2. Controls circular field of data acquisition
    - X & Y Axis
  3. Large SFOV (up to 52cm)
    - Small SFOV (25 cm)
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59
Q
  1. Typical size of Large SFOV?
    - Small SFOV?
  2. How can SFOV be adjusted?
  3. What is SFOV selected based off of?
    - Which SFOV is most common?
A
  1. Large = 52cm
    - Small = 25 cm
  2. Reducing number of detectors active during image acquisition
  3. Anatomy / ROI being scanned
    - Small SFOV
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60
Q
  1. What is DFOV?
  2. How is DFOVadjusted?
    - Based off of what?
  3. What makes up the matrix?
A
  1. Portion of acquired data that will be displayed on matrix
  2. By tech
    - Based off Anatomy / ROI being scanned
  3. Numbers that form rows and columns & come together to form pixels
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61
Q
  1. What is DFOV typically adjusted to?
  2. Decreasing DFOV results in:
  3. What is controlled by X & Y axis, and controls the circular field of image acquisition?
A
  1. Anatomy / ROI only
  2. Reduced display of areas outside ROI
    - Increased display size of ROI
    - Decreased pixel dimension & volume of voxel
  3. SFOV
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62
Q
  1. What are slip rings?
  2. Why are they important in CT?
  3. What do slip rings eliminate need of?
A
  1. Circular, electrically conductive rings and brushes that transmit electrical energy across rotating surface
  2. Make continuous rotations of gantry for spiral/helical scanning possible
  3. Wires / Cables to power Gantry that need to be unwound after each scan
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63
Q
  1. What was used/done before slip rings?
  2. What are 2 major functions of slip rings?
  3. What do slip-rings consist of?
A
  1. cables that powered gantry would need to be unwound after a complete rotation
  2. Allow continuous rotations of gantry / transmit electrical energy across rotating surface
    - Transfer data to computer
  3. Circular rings & brushes that are electrically conductive
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64
Q
  1. What is definition of Data Acquisition?
  2. Slice by Slice, how is it acquired?
  3. Axial Data acquisition is also known as:
A
  1. Collection of information from patient that produces image
    1. Tube rotates around patient
      - 2. Data collected
      - 3. Xray tube stops
      - 4. Patient table moves (indexed)
      - 5. Process begins again / repeats
  3. Sequential Scanning
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65
Q
  1. What is sequential scanning?
  2. What occurs during axial scan?
    - (Explain how it’s scanned/ steps)
  3. Is axial acquisition high or low resolution?
A
  1. AKA AXIAL SCANNING
  2. Xray beam collimated to preset slice thickness & detector configuration
    - During each rotation data only acquired with predetermined detectors @ desired slice thickness
    - Table moves
    - Repeat for entire ROI
  3. High resolution
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66
Q
  1. Volume data acquisition also known as:
  2. Why is volume data acquisition used?
  3. Explain how volume data is scanned:
A
  1. spiral / helical acquisition
  2. Acquisition of Large volumes of data at time
  3. Tube continuously rotates around patient
    - Table simultaneously and continuously moves until scan of ROI is covered
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67
Q
  1. What is helical scan also known as?
  2. In volume scanning, image is acquired during _____A____. Because patient moves ___B________.
  3. What is contiguous data?
A
  1. Spiral / Volume
  2. A. Entire breath hold
    - B. Constant speed through gantry
  3. When there is no gap of image acquisition data
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68
Q
  1. Difference between Axial & Helical scans?
  2. What is it called when there is no gap between image acquisition data?
  3. What type of scan is for high volumes / acquisition?
A
  1. Axial = Sequential Scanning = 1 Rotation, Table Moved & Repeats
    - Helical = Volume / SpiralScanning = One continuous scan through gantry
  2. Contiguous Data
  3. Volume / Helical / Spiral
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69
Q
  1. in single slice helical/spiral scanning one revolution results how many slices?
    - How about Multi-Slice Scanners?
  2. What are examples of Multi-slice scanners?
    - What is produced?
  3. Slices per revolution depends on what?
A
  1. Single = one revolution = 1 slice
    - Multi = multiple PER revolution
  2. 32, 40, 64, 320
    - multiple image slices per revolution of the tube (ex. 32 Slice scanner = 32 slices per 1 revolution)
  3. CT Scanner Systems abilities
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70
Q
  1. How many slices can the following generate per revolution?
    - 32, 40, single, 64, 320
  2. What describes the way the x-ray tube and the detectors are arranged to collect attenuation measurements?
  3. What is the most common type of data acquisition used in modern CT scanners?
A
  1. single = 1 slice per rotation
    - 32 = 32 slices per 1 rotation, etc..
  2. Data Acquisition Geometry
  3. x-ray tube and the detectors are coupled and rotate 360 degrees around the patient utilizing a fan beam
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71
Q
  1. What is Data Acquisition Geometry?
  2. Most common type of data acquisition used in modern CT scanners is one with ____A___ & ____B____ coupled and rotate ____C___ degrees around the patient utilizing a ____D___ Beam.
A
  1. Describes the way the x-ray tube and the detectors are arranged to collect attenuation measurements
  2. A. Xray Tube
    B. Detectors
    C. 360 Degrees
    D. Fan Beam
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72
Q
  1. What type of beam is typically used in CT?
  2. Dual Source CT Scanners consist of __________.
  3. What do Dual Source Scanners Allow?
A
  1. Fan Beam
  2. Two DASs offset by 90 degrees.
  3. 2 kVp values at same time.
    - Allows for improved resolution of soft tissue, improved temporal resolution, improved patient dose & ability separate bone & plaque from intravenous iodine
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73
Q
  1. Dual Source Scanners have 2 ___A__ offset by __B_ degrees. There are __C__ x-ray tubes capable of acquiring ___D___, at two different ___E___.
  2. What do Dual Source Scanners improve?
    -How?
A
  1. A 2 DAS
    B. 90 Degrees
    C. Two Tubes
    D. Two Simultaneous Acquisitions
    E. Two Different kVp
  2. Allows for improved resolution of soft tissue, -
    - improved temporal resolution,
    - improved patient dose
    - ability separate bone & plaque from intravenous iodine

-BY ALLOWING @ DIFF kVp VALUES AT SAME TIME

74
Q
  1. Advantages of MSCT include the following:
  2. Define “Ray”
  3. Define “Ray Sum”
A
  1. Increased Pitch and Increased Tube Rotation
    - Improved Spatial Resolution
    - Efficient X-ray Beam
    - Increase in speed and volume coverage
    - Improved Accuracy in Procedures
  2. part of the x-ray beam that travels through the patient and falls on one detector.
  3. Total measurement of radiation that has traveled through a patient and fell on a single detector.
75
Q
  1. in MSCT, Increasing Pitch & Tube Rotation = ___________
  2. In MSCT, How is Spatial Resolution improved?
  3. In MSCT, The x-ray beam is more _____. Meaning What?
A
  1. Inc Pitch / Rotation = Allow larger volumes of patient to be scanned in less time
  2. Isotropic Imaging provides higher quality images with less artifact
  3. More Efficient = Utilizes entire beam increases life of x-ray tube
76
Q
  1. In MSCT, Speed & Volume coverage are ____ (Increased/Decreased/Same)
  2. Above Results in _______ Dose.
  3. Why are MSCT Are used in Procedures?
A
  1. Increased Speed / Coverage
  2. Reduced Radiation Dose
  3. Improved Accuracy Aid in needle placements
77
Q
  1. MSCT Have Improved:
  2. Ray vs Ray Sum:
  3. What are above measurements are made by?
A
  1. Pitch, Tube Rotation, Spatial Resolution, XRAY Beam Efficiency, Speed & Volume Coverage, & Accuracy
  2. Ray = part of the x-ray beam that travels through the patient and falls on one detector.
    Ray Sum = total measurement of radiation that has traveled through a patient and fell on a single detector.
  3. By the DAS
78
Q
  1. Define “View”
  2. Define “Algorithms”
  3. What is required for an Algorithm?
A
  1. Collection of measurements that has been calculated by the DAS.
  2. set of rules or directions for getting a specific output from a specific input.
  3. An algorithm must not be vague, must describe an operation, and must terminate after a certain number of steps.
79
Q
  1. What is A set of rules or directions for getting a specific output from a specific input.
  2. “View” is calculated by what?
  3. “View” measurements are what in relationship to xrays striking detector?
A
  1. Algortihm
  2. DAS
  3. The measurement is proportionate to the number of rays that have struck the detector.
80
Q
  1. 3 Requirement for Algorithm?
  2. Where does Measurement Data or Scan Data comes from?
A
  1. An algorithm must not be vague, must describe an operation, and must terminate after a certain number of steps.
  2. The Detectors
81
Q
  1. Measurement Data AKA:
  2. What is Measurement Data? - What Occurs
  3. When do errors in measurement data occur?
    -What Results?
A
  1. Scan Data
  2. Measurement data undergo preprocessing before the image can be further reconstructed using a reconstruction algorithm.
  3. Errors occur during the acquisition process,
    - if they are not corrected it will result in poor image quality with image artifacts.
82
Q
  1. Define “Raw Data”
  2. Define “Image Data”
  3. Define “Convolution”
A
  1. The preprocessed scan data that undergoes reconstruction with image algorithms used by the scanner.
  2. Image data is the reconstructed data that creates the CT image.
    The image data has undergone convolution and is projected onto a matrix.
  3. Convolution is a filtration algorithm that removes blurring in an image during back-projection.
83
Q
  1. What is filtration algorithm that removes blurring in an image during back-projection called?
  2. What is a the preprocessed scan data that undergoes reconstruction with image algorithms used by the scanner called?
  3. What data undergo preprocessing before the image can be further reconstructed using a reconstruction algorithm called?
A
  1. Convolution
  2. Raw Data
  3. Measurement / Scan Data
84
Q
  1. What is the reconstructed data that creates the CT image that has undergone convolution and is projected onto a matrix called?
  2. What is the result of errors occurring during acquisition that are not corrected?
  3. Three main types of data during image acquisition are:
    - Differences?
A
  1. Image Data
  2. Poor image quality with artifacts
  3. Measurement/Scan Data = from detector, undergo preprocessing
    - Raw Data = is the processed data from scan data that is reconstructed with algorithms
    - Image Data = Reconstructed data that creates image
    (THINK M.R.I) for order of acquisition
85
Q
  1. Why is Image Reconstruction used?
    - What is utilized to do this?
  2. After data acquisition is complete, the data obtained by detectors goes through what steps?
A
  1. Used to remove motion artifacts caused during continuous scanning.
    - Utilizes interpolation to make corrections.
  2. Preprocessing
    - Reformation of the raw data
    - Convolution
    - Image reconstruction algorithm
    - Images are reconstructed utilizing CT numbers
    - CT Image is displayed
86
Q
  1. What is “Interpolation”
    - When is it used?
  2. What does interpolation help create?
A
  1. A Mathematical process that uses data points above and below a slice to reconstruct an image
    - Used in helical CT scans
  2. Interpolation helps to create an image that is free of motion
87
Q
  1. What might be used in a helical acquisition of a patient is constantly moving?
  2. Define “Back Projection”
  3. Why isn’t “Back Projection” used during clinical CT?
A
  1. Interpolation
  2. Mathematical process used to create images in which attenuation data are projected onto a matrix.
  3. Process does not produce a sharp image and is not used in clinical CT.
88
Q
  1. What is a mathematical process that uses data points above and below a slice to reconstruct an image called?
  2. What is “Filtered Back Projection” used for?
    - How does is do this?
  3. When does Filtered Back Projection take place?
A
  1. Interpolation
  2. Removes the blurring that occurs with back projection.
    - Uses a convolution filter
  3. Filtering takes place prior to the attenuation data being projected onto the matrix
89
Q
  1. Another name for Convolution Method?
  2. What uses convolution filters?
    - Results?
  3. Major concerns for Filtered Back Projection?
A
  1. Filtered Back Projection
  2. Filtered Back Projection
    - Removes blurring from back projection
  3. Noise and streak artifact
90
Q
  1. What is Prospective Reconstruction?
  2. Can this (above) be manipulated?
  3. What step does convolution occur after detectors obtain data?
A
  1. The initial image reconstruction process that takes place immediately after the acquisition is acquired
  2. The images can undergo further manipulation retrospectively, to adjust the displayed image.
  3. THIRD
    (* Data Obtained By Detector, THEN:*
  4. Preprocessing
  5. Reformation of the raw data
  6. Convolution
  7. Image reconstruction algorithm
  8. Images are reconstructed utilizing CT numbers
  9. CT Image is displayed)
91
Q
  1. What is The initial image reconstruction process that takes place immediately after the acquisition is acquired called?
  2. What is the first step after data is obtained by detector?
  3. Which step uses Reconstruction Algorithm
A
  1. prospective reconstruction
  2. Preprocessing
  3. 4th

(* Data Obtained By Detector, THEN:*
1. Preprocessing
2. Reformation of the raw data
3. Convolution
4. Image reconstruction algorithm
5. Images are reconstructed utilizing CT numbers
6. CT Image is displayed)

92
Q
  1. What is Iterative algorithms
    - How does it work?
  2. What can be used to reduce image noise which helps to improve the quality of the image, while also reducing patient dose?
  3. Do Iterative Recon Algorithms increase or decrease patient dose?
    - What about image quality?
A
  1. Algorithms that work to reconstruct an image by starting with an assumption of how a CT image is supposed to appear.
    - The assumption is then compared to measured values within the CT image.
  2. Iterative reconstruction
  3. Reduce Exposure & Increase Image Quality
    reduce image noise when using lower exposures, while also preserving image quality. This also helps to reduce image artifacts.
93
Q
  1. The iterative algorithm makes ___A___ to the ___B____ values, until it agrees with the __C___.
  2. Iterative algorithm starts with what?
  3. What is Iterative Reconstruction?
    - What does it help with?
A
  1. A. corrections
    - B. Measured values
    - C. Assumption.
  2. Assumption of how CT image should appear
  3. reduce image noise which helps to improve the quality of the image, while also reducing patient dose.
94
Q
  1. What makes makes corrections to the measured values, until it agrees with the assumption.
  2. How often does this occur?
  3. Iterative Reconstruction Algorithms ___A___ image noise when using ___B___ exposures, while also preserving __C____. This also helps to __D___ image artifacts.
A
  1. The iterative algorithm
  2. Repeated until the assumption and measured values within are within an acceptable limit.
  3. reduce image noise when using lower exposures, while also preserving image quality. This also helps to reduce image artifacts.
95
Q
  1. MPR Stands for:
    - Used for?
  2. Benefits of MPR: (4)
A
  1. Multiplanar Reconstruction (MPR)
    - Used to create coronal, sagittal, and paraxial images from contiguous axial images.
  2. MPR images allow for the visualization of structures in relation to the surrounding structures.
    - MPR images help to determine the true extent and localize lesions, as well as assist with fracture identification.
    - MPR images allow for different views of the same image without adjusting the voxels within each image, which occurs with retrospective reconstruction.
    - MPR images can be displayed at varying slice thickness and slice intervals. The slice thickness and interval chosen for reformation is based upon the desired area to be viewed.
96
Q
  1. What are used to create coronal, sagittal, and paraxial images from contiguous axial images.
  2. Difference between Sagittal, Coronal & Axial Images?
  3. How can oblique images be obtained?
A
  1. Multiplanar Reconstruction (MPR)
  2. Sagittal images divide the body from left to right
    - Coronal images divide the body from anterior to posterior
    - Axial images divide the body from superior to inferior
  3. reconstructed from arbitrarily selected angles.
97
Q
  1. What is MIP stand for?
  2. What does MIP utilize?
    - What is displayed?
  3. What CT Exam typically uses this?
    - Why?
A
  1. Maximum Intensity Projection (MIP)
  2. Utilizes volume rendering.
    - Only the tissues with the greatest attenuation within the voxel are displayed.
  3. This is often used for CTA studies because it clearly displays vessels containing contrast.
98
Q
  1. What does MinIP stand for?
  2. What is displayed with MinIP?
  3. MPR Slice thickness and interval chosen for reformation is based upon __________.
A
  1. Minimum Intensity Projection (MinIP)
  2. Only the tissues with the lowest attenuation within a voxel are displayed.
  3. the desired area to be viewed
99
Q
  1. What are two MPR techniques that adapt images?
    - Differences?
  2. Which MPR technique is used in CTAs?
  3. What is 3D imaging?
A
  1. MIP & MinIP
    MIP =
    Only tissue w greatest attenuation in voxel displayed
    MinIP = only tissue w lowest attenuation in voxel displayed
  2. MIP
    - Clearly displays vessels containing contrast
  3. A method by which data is collected from a patient and is processed and displayed on a monitor with the perception of depth.
100
Q
  1. What is “Modeling” in 3D imaging?
  2. Shading bs Lighting in 3D imaging?
  3. What is Rendering?
A
  1. Describes physical properties of an object.

2.Shading determines the appearance of the 3D image.
- Lighting enhances the appearance of the 3D image.

  1. A process that converts data collected from the patient into a 3D image.
101
Q
  1. ____A___ determines the appearance of the 3D image. While ___B_____ enhances the appearance of the 3D image.
  2. A process that converts data collected from the patient into a 3D image is called?
  3. What adds color, lighting, and texture to the 3D image?
A
  1. Shading
    - Lighting
  2. Rendering
  3. Rendering
102
Q
  1. Two types of Rendering:
    - Differences?
  2. Which results in higher image quality?
    - Why?
  3. Why are things slices used for image reconstruction?
A
  1. Surface Rendering = uses only parts of the data set for image recon
    - Volume Rendering = uses the entire data set for image recon.
  2. Volume
    - Because the entire data set is used, volume rendering creates a higher quality image.
  3. ensure that the 3D image contains a high level of image detail / overlap
103
Q
  1. Which rendering uses parts of data for image reconstruction?
  2. To ensure overlap / high image detail, 3D Reconstruction uses what type of slices?
  3. Where can 3D Reconstruction be done?
A
  1. Surface Rendering
  2. Thins
  3. Standalone 3D station or CT scanner itself
104
Q
  1. Stand-alone workstations are capable of producing the following 3D images:
  2. Which rendering uses entire data for image recon?
    - Results in?
  3. Which MPR technique allows for better contrast display?
A

1.MPR
Surface Rendering
MIP and MinIP
Virtual reality imaging

  1. Volume Rendering
    - Higher Detail
  2. MIP
105
Q
  1. Pixels represent what?
  2. What is Pixel Size Relation to Spatial Resolution?
  3. Does a pixel size impact the Matrix Size, or does the Matrix size impact Pixel size?
A
  1. a number that represents the tissue or area that was imaged
  2. INVERSE
    - DECREASE Pixel Size = INCREASE SR
  3. MATRIX impacts PIXEL (Pixel doesnt impact Matrix)
106
Q
  1. What size pixel has higher spatial resolution?
  2. What is size of Pixel is impacted by?
  3. Pixel vs Voxel?
A
  1. Small Pixel = Better SR
  2. impacted by the size of the matrix
  3. Pixel = Number that represents volume of tissue or area
    Voxel = Volume / Volume Element itself
    DEPTH TURNS PIXEL INTO VOXEL
107
Q
  1. Pixel Size Relationship To Matrix Size?
  2. What is a “Voxel”
  3. Voxel Size Depends on?
A
  1. The LARGER Matrix Size, the SMALLER the pixel size
    -INVERSE RELATION
  2. pixel is representative of a volume of tissue, this volume or volume element is referred to as a voxel.
  3. Depends on chosen slice thickness in the z-axis, DFOV, and matrix size.
108
Q
  1. What turns a pixel into a voxel?
    -What Axis is involved?
  2. As radiation passes through each Voxel, ________ is generated for each ______ in display image.
  3. What shade(s) of gray do Pixels have?
    - Based on?
A
  1. DEPTH
    - Z-Axis
  2. CT Number generated for each pixel in display image
  3. RANGE of grays
    - Based on CT number that was generated for that pixel
109
Q
  1. How many different grayscale values can an image have?
  2. What is “Isotropic” Imaging?
    - Does this result in good or bad image quality?
A
  1. 256 DIFFERENT values
  2. When the length, width, & height of a voxel is equal and form a perfect cube.
    - EXCELLENT QUALITY
110
Q
  1. What is it called When the length, width, & height of a voxel is equal and form a perfect cube?
  2. Does above result in good or bad image quality?
  3. What is the number within each pixel of a CT image that is representative of the attenuation of the density of the tissue that was imaged referred as?
A
  1. ISOTROPIC IMAGING
  2. EXCELLENT QUALITY
  3. CT Number
111
Q
  1. Define “CT Number”
  2. Another name for CT Number?
  3. How is attenuation for an object/tissue determined?
A
  1. a number within each pixel of a CT image that is representative of the attenuation of the density of the tissue that was imaged.
  2. Hounsfield Unit (HU)
  3. Determined by the linear attenuation coefficient.
112
Q
  1. What is a “Hounsfield Unit”
  2. How do you generate a CT Number?
  3. Does every tissue in a body have the same CT Number?
A
  1. number within each pixel of a CT image that is representative of the attenuation of the density of the tissue that was imaged.
    - AKA CT NUMBER
  2. Generated by comparing the attenuation of the tissue imaged to the attenuation of water.
  3. EVERY TISSUE HAS OWN # BASED ON CT MANUFACTOR
113
Q
  1. How does Linear Attenuation Coefficient determine the attenuation of an object / tissue?
  2. What is the CT Number for Water?
    - Bone?
    -Air?
  3. What is CT Number converted to in an image?
A
  1. The linear attenuation coefficient takes the attenuation signal that is created by a detector, and assigns it a numerical value.
  2. Water = 0
    - Bone = +1000
    - Air = -1000
  3. CT Number converted to Grayscale Image
114
Q
  1. LOW CT Number = ______ Appearance on Image
    - HIGH CT Number = ______ Appearance on Image
    (Trick to Remember?)
  2. How Do Numbers In-between LOW & HIGH CT Numbers Appear?
  3. What has HU of +1000?
    -0?
    - -1000?
A
  1. LOW = BLACK
    - HIGH = WHITE
    (Think H in White / High # = WHITE Appearance & L in BLACK = L In LOW Appearance )
  2. Gray
  3. Water = 0
    Bone = +1000 / Air = -1000
115
Q
  1. What is Window Width?
  2. What is Window Level?
  3. What is Windowing?
A
  1. Range of CT Numbers that compose CT Image
  2. Center of Range
    (Center of Window Width Range)
  3. Process in which the grayscale of a particular image can be adjusted.
116
Q
  1. WW & WL are adjusted to alter ______ & _______. This process is called _________
  2. Above is done by who or what?
    - Why?
  3. What does Large WW mean?
A
  1. Brightness & IMAGE CONTRAST
    - Windowing
  2. Tech / Radiologist
    - Better demonstrate anatomy & pathology
  3. LARGE WW = LONG Grayscale
    - Lots of Grays
    - Transition from Black to White will take LONGER
117
Q
  1. Window Width adjusts _________
    - Window Level Adjusts ______
  2. ____A_____ is the range of the grayscale that can be displayed.
    The center of grayscale range is referred to as the ____B_____.
  3. What does Narrow WW Mean?
A
  1. WW = Contrast
    - Level = Brightness
    (WWC / WLB)
  2. A = WW
    - B = WL
  3. NARROW WW= SHORT Grayscale
    -Transition between black & white quicker
118
Q
  1. If WW is 2000 HU, what could grayscale be?
    - What would be WL?
  2. Large WW vs Short WW?
  3. Why is adjusting WW settings important?
A
  1. ranges from -1000 HU to +1000 HU
    - WL of 0 HU.
  2. LARGE WW = Long Grayscale / Lots Gray / Long Transition
    - Narrow = Short Grayscale / Short Transition
  3. So that the structures of interest are properly displayed.
119
Q
  1. If WW is 100 HU, what could grayscale be?
    - What would be WL?
  2. What can including an unnecessarily wide WW range result in?

3.What WW should be used if ROI contains structures of similar densities?
-Why?

A
  1. ranges from 0HU to +100 HU,
    - WL of +50 HU.
  2. Can reduce the ability to differentiate between differences in attenuation.
  3. narrow WW should be utilized to properly display the differences between the structures with similar attenuation.
120
Q
  1. If WW is 600 HU, what could grayscale be?
    - What would be WL?
  2. Would an Abdomen have a wide or narrow WW?
    - Why?
  3. What should WL be set to?
A
  1. ranges from -300 HU to +300 HU
    - WL of 0 HU.
  2. WIDE WW
    - properly display the various tissues and densities present in the anatomical area.
    - It is common for abdomen imaging to contain fat, bone, air, and fluid.
  3. Set near the CT number for the area of interest that is being imaged.
121
Q
  1. Relation between WW & Contrast?
  2. What Type of WW has high contrast?
    - Low?
  3. What WW is best for contrast in most instances?
    - Why?
A
  1. INVERSE
    -INCREASE WW = DECREASE CONTRAST
    - DECREASE WW = INCREASE CONTRAST
  2. NARROW = HIGH CONTRAST / FEW GRAYS
    - WIDE = LOW CONTRAST / MANY GRAYS
  3. medium WW setting.
    - Allow for most structures and gray shades to be displayed.
122
Q
  1. Cine Viewing allows for what?
  2. Define “ROI”
    - Define “Mean”
  3. Define “Standard Deviation)
A
  1. for the review of large amounts of images quickly, and in a continuous loop.
  2. user identified area of tissue that displays the HU for that area.
    - MEAN = the average HU within a set ROI.
  3. the amount of variation of HU within a given data ROI.
123
Q
  1. What is VR used for?
  2. VR Imaging typically used in what?
    - This helps/allows what?
  3. What is used with above technique?
    - Why?
A
  1. visualization tools allow “fly through” images of organs for evaluation of structures.
  2. simulates endoscopic procedures and allows for unrestricted exploration of organs and structures.
  3. Volume rendering is utilized with this technique because it allows for optimum visualization of anatomy and minimizes partial volume averaging artifacts.
124
Q
  1. Define “Spatial Resolution”
  2. What is SR measured in?
  3. What is “In Plane Resolution”?
A
  1. The ability of the CT scanner to show small objects that are close together and to distinguish structures with different densities.
  2. line pairs per centimeter (lp/cm).
  3. In-plane resolution is the spatial resolution within the x and y directions.
125
Q
  1. Term for The ability of the CT scanner to show small objects that are close together and to distinguish structures with different densities.
  2. What is Spacial Frequency determined by?
  3. What is the spatial resolution within the x and y directions?
A
  1. Spatial Resolution
  2. determined by what is being imaged.
    - If imaged area is made up of objects with low variations densities, it would be considered to have low spatial frequency.
    - If imaged area is made up of objects with high variations in densities, it would be considered to have high spatial frequency.
  3. In-plane resolution
126
Q
  1. If image has LOW Spatial frequency, what does this mean?
  2. If image has HIGH Spatial frequency, what does this mean?
  3. Size of area being imaged relation to Spatial Frequency?
A
  1. LOW = imaged area is made up of objects with low variations in densities
  2. HIGH = imaged area is made up of objects with high variations in densities
  3. INVERSE
    - DECREASE area size = INCREASE Spatial Frequency
    - INCREASE area size = DECREASE Spatial Frequency
127
Q
  1. Is Increased Spatial Frequency good or bad?
    - Why?
  2. How is Spatial Frequency Measured?
  3. How is Spatial Resolution measured?
A
  1. Increases in the spatial frequency make it harder to accurately display what is being imaged.
  2. modulation transfer function (MTF)
  3. line pairs per centimeter (lp/cm).
128
Q
  1. What is MTF?
    - Stand For?
    - Function/Use?
    - How?
A
  1. modulation transfer function.
  • MTF is used to graph the CT scanners ability for spatial resolution, and this is known as the MTF curve.
  • MTF describes the accuracy of the image that was produced when compared to the actual object.
129
Q
  1. What is MTF curve?
  2. What does MTF describe?
    - Compare to?
  3. Perfect MTF?
    - MTF for Image not able to be provided?
A
  1. Graph of scanners ability for spatial resolution
  2. MTF describes the accuracy of the image that was produced when compared to the actual object.
  3. 1.0
    - 0
130
Q
  1. MTF of 0 =
    MTF of 1 =
  2. MTF Axis =
    - What is the other Axis?
  3. Higher Scanner Charts on x-axis =
A
  1. 0 = not imaged
    - 1 = Perfectly Imaged
  2. MTF on the y axis
    - spatial frequency on the x axis.
  3. The higher a scanner charts on the x axis = the scanner is capable of producing images with higher spatial resolution.
131
Q
  1. MTF Chart:
    Y Axis =
    X Axis =
  2. Is higher charts better or worse spatial resolution?
  3. What Impacts Spatial Resolution?
A
  1. Y = MTF
    - X = SPATIAL RES
  2. HIGHER CHART = HIGHER RESOLUTION ABILITY
  3. Focal Spot Size
    Detector Size
    Image Recons
    Pixel Size
    Sampling
132
Q

Spatial Resolution Relation To:
1. Focal Spot Size
2. Detector Size
3. Image Reconstruction
4. Pixel Size
5. Sampling

A
  1. SR & Focal spot size = INVERSE
    - DECREASE FSS = INCREASE SR
    (a smaller focal spot size will improve spatial resolution)
  2. Detector size = INVERSE
    DECREASE DETECTOR SIZE = IMPROVES SPATIAL FREQUENCY = IMPROVED SR
    (smaller detectors improve spatial resolution, as smaller detectors improve spatial frequency)
  3. Image Reconstruction– the algorithm that is selected for image reconstruction can improve spatial resolution b/c enhance the differences in densities objects.
  4. Pixel size = INVERSE
    DECREASE PIXEL SIZE = INCREASE SR
    (the smaller the pixel size, the better the spatial resolution)
  5. Sampling = DIRECT
    INCREASE SAMPLING = INCREASE SR
    (sampling of an object should be at least 2x the spatial frequency of the object being imaged)
133
Q
  1. Desired FSS, Detector Size, Pixel Size & Sampling Frequency for Improved Spatial Resolution?
  2. How/Why does Detector Size improve SR?
  3. How does Image Reconstruction Improve Spatial Resolution?
A
  1. SMALL FSS, SMALL DETECTOR SIZE SMALL PIXEL SIZE & AT LEAST 2x SAMPLING FREQUENCY
  2. smaller detectors = improve spatial frequency = improved SR
  3. algorithm have the ability to enhance the differences in densities between two closely situated objects.
134
Q
  1. How can Pixel Size impact spatial resolution?
  2. What is Nyquest Therom?
  3. Define Longitudinal spatial resolution
A
  1. Smaller pixels = less likely that tissues with different densities will be captured within the same pixel = Improved SR
  2. sampling of an object should be at least 2x the spatial frequency of the object being imaged, to ensure that the image can be accurately reproduced.
  3. The image quality in the z axis.
    - Can be described by the slice sensitivity profile, which identifies the amount of broadening that occurs along the z axis
135
Q
  1. What Axis Involves Longitudinal spatial resolution?
  2. SSP stands for?
    - What is this used to describe?
  3. SSP During Volumetric Scanning?
    - What occurs
A
  1. X Axis
  2. slice sensitivity profile
    - Longitudinal SR
  3. SSP of a section broadens as the patient moves and partial volume averaging occurs
136
Q
  1. Longitudinal resolution can be improved by:
  2. Sampling Frequency must be _________________
  3. What is Contrast Resolution?
A
  1. Utilizing narrow beam collimation
    Decrease the pitch
    Utilize thin detector collimation
  2. 2x frequency of object being imaged
  3. ability of the scanner to differentiate small differences in attenuation between closely spaced objects.
137
Q
  1. What is ability of the scanner to differentiate small differences in attenuation between closely spaced objects.
  2. What is ability of a CT scanner to produce a motion free image?
  3. Answer to #2 very important in what type of CT Exams?
A
  1. Contrast Resolution
  2. Temporal Resolution
  3. CT Cardiac studies.
138
Q
  1. How can Contrast Resolution be measured?
A
  1. use of a phantom that contains objects of different densities. The varying densities represent a certain level of attenuation and a representative HU that is able to be displayed for that scanner.
139
Q

How Contrast Resolution Improved By:
1. Object Contrast
2. Scatter
3. Image Reconstruction
4. Detector Size
5. Noise

A
  1. Object Contrast-the natural contrast of an object being imaged can impact the level of contrast resolution
  2. Scatter
    REDUCE SCATTER = IMPROVE CONTRAST RES.
  3. Image Recon
    - algorithms similar to a soft tissue kernel, will help to improve contrast resolution.

4 Detector size
- smaller detectors improve contrast resolution as thinner slices reduce the variation of attenuation within each pixel.

  1. Noise- DIRECT EFFECT
    - Decreasing the noise in an image will improve the contrast resolution. Increasing the noise will worsen the contrast resolution.
140
Q
  1. What is a way Object Contrast can be increased?
  2. How can you reduce scatter radiation?
    - Does this improve or decrease Cont. Res?
  3. How does Detector Size impact Contrast Resolution?
A
  1. Using contrast media
  2. reducing the radiation beam will also reduce the scatter radiation,
    - improve contrast resolution.
  3. smaller detectors = thinner slices = reduce the variation of attenuation within each pixel
    - IMPROVES CONT RES.
141
Q
  1. Does Noise Directly or Indirectly impact Contrast Resolution?
    - Explain How
  2. What are two primary ways in which the temporal resolution of a CT scanner can be impacted?
  3. Does Answer #2 Directly or Indirectly Impact Temporal Resolution?
A
  1. DIRECTLY (INVERSE RELATION)
    - Decreasing the noise in an image will improve the contrast resolution. Increasing the noise will worsen the contrast resolution.
  2. speed in which the gantry rotates
    - 8 Use of half-scan or multi-segment reconstruction
  3. DIRECTLY IMPACT TEMP RES*
142
Q
  1. What does Half-scan reconstruction consist of?
    - Utilized for?
    - Impact on Temporal Res?
  2. What does Multi-segment reconstruction consist of?
    - Utilized for?
A
  1. consists of a reconstruction of data that was obtained from only a half of a gantry rotation.
    - Utilization of this method allows for the scan time to be cut in half, and improves temporal resolution.
  2. consists of a reconstruction of data that was obtained at more than one point in time. The multiple image segments are reconstructed into one data set.
    - Used during CT Cardiac exams (use two or more segment reconstructions)
143
Q
  1. Half Scan Recon vs Multi Segment Recon:
  2. Define “Noise”
    - Results in:
  3. Noise effect on Image Quality / Details:
A
  1. HALF = Only data from half hangry rotation used
    - MULTI = Data from 2 points in time used
  2. Differences in the pixel values of a homogeneous object. The result of these fluctuations is an image that is grainy.
  3. degrades image quality and affects the perceptibility of detail.
144
Q
  1. How can you measure noise?
  2. Three major sources of noise:
  3. What is SNR?
A
  1. measured by observing the standard deviation of a given set of pixels within an ROI.
  2. Quantum mottle
    - Component limitations
    - Reconstruction algorithms
  3. signal-to-noise ratio
    - used to quantify the amount of noise in a CT image
145
Q
  1. What is Quantum Mottle?
    - Results in:
  2. What is Component limitations?
    - Results in?
    - AKA?
  3. Recon Algorithm can cause noise by:
A
  1. Result of an x-ray photon flux. When there are not enough photons that strike the detector,
    - Image that appears noisy when reconstructed.
  2. Limitations within the physical components of the CT scanner
    - attribute to the noise of an image
    - electronic noise.
  3. An algorithm that reconstructs an image with high resolution also tends to be an image with increased noise.
146
Q
  1. What is used to quantify the amount of noise in a CT image?
  2. Relationship between Spatial Resolution, Contrast Resolution & SNR
A
  1. The signal-to-noise ratio
  2. SPATIAL & SNR/ CONT. RES = INVERSE
    - SNR & CONT. RES = DIRECT (Increase Spatial Res = Decreasing SNR/CONT. Res
    - INCREASING SNR = INCREASING CONT. Res & Decreasing Spat. Res)
147
Q
  1. Improved SNR = ______ Contrast Resolution & _________ Spatial Resolution
  2. What is Photon Flux?
  3. Increasing the rate of photons results in a _____ in noise.
A
  1. IMPROVED CONT. RES
    - DECREASED SPAT. RES
  2. Rate that photons pass through an area in a set of time.
  3. DECREASED
148
Q
  1. What is the rate that photons pass through an area in a set of time?
  2. What does high pitch result in an image?
    - Why?
  3. What can be adjusted to compensate for above?
A
  1. Photon Flux

2.HIGH PITCH = noisy image
-less photons are interacting with detectors.

  1. To utilize higher pitch w/o ruining image quality, DOSE must be increased.
149
Q
  1. How does Increasing mA, kVp, or the scan time affect Photon Flux?
    - Downside?
  2. What pitch results in a noisey image? Why?
  3. What patient size results in more noise on an image?
    - How can this be fixed/adjusted?
A
  1. Increase the photon flux within an image
    - Also increases patient dose and decreased contrast resolution.
  2. HIGH PITCH / Less photons interact w/ detectors

3.LARGER PT = MORE NOISE - Radiation Dose Adjusted to Compensate

150
Q
  1. Do you want INCREASED photon flux or DECREASED?
    - Why?
  2. What Effects Photon Flux?
  3. To use high pitch without a noisey image, what is adjusted?
A
  1. INCREASED
    - Result in DECREASED Noise
  2. mAs, kVp & scan time
    - DIRECT (Increase mAs, kVp or Scan Time = INCREASED Flux)
  3. INCREASE patient dose
151
Q
  1. FACTORS that impact Noise:
  2. What is Dose Modulation?

3, How can Algorithms increase noise?
- Example?

A
  1. Photon Flux, Pitch, Patient, Algorithms & Voxel
  2. Used to adjust the patient dose to produce an image with an acceptable amount of noise, while keeping the increased patient dose to a minimum.
  3. Recon Algoirithms that require high resolution result in an image with increased noise.
    -Ex: high resolution algorithm would be the bone window.
152
Q
  1. What is used to adjust the patient dose to produce an image with an acceptable amount of noise, while keeping the increased patient dose to a minimum.
  2. High Resolution Algorithm Example?
  3. Voxel Size Relationship to Noise Level?
A
  1. Dose Modulation
  2. Bone Window
  3. DIRECT (INVERSE)
    - As the size of the voxel increases, the noise decreases.
153
Q
  1. As voxel and pixel size increases it results in ________ & _______ .
  2. Increasing Voxel Size = ______ Image Noise & ______ Spatial Resolution
  3. Three SOURCES of Noise?
  4. Five FACTORS Impact Noise
A
  1. loss of detail and lower spatial resolution.
  2. Increase Voxel Size = Decreased Noise & Decreased Spatial Resolution
  3. SOURCES = Quantum Mottle, Component Limitations & Recon Algorithms
  4. FACTORS = PHOTON FLUX, PITCH, PATIENT, POST PROCESS (RECON ALGO.) & VOXELS
154
Q
  1. HOW IS UNIFORMITY MEASURED?
  2. What Should occur if there is uniformity?
  3. What is the acceptable variation range in uniformity?
A
  1. Use of a uniform water phantom.
    - Imaging the phantom and placing several ROIs throughout the phantom on the CT image.
  2. measurements within each ROI should be the same.
  3. 5 HU range of variability that is acceptable when determining uniformity.
155
Q
  1. What is linearity?
  2. How is linearity measured?
A
  1. describes the accuracy of a CT number compared to the linear attenuation coefficient of the object that was imaged.
  2. CT phantom contains several materials with different densities with specific CT numbers.
    - Its imaged and ROI measurements are taken on the CT image to determine if the measured CT number for the different materials is appropriate.
156
Q
  1. What describes the accuracy of a CT number compared to the linear attenuation coefficient of the object that was imaged?
  2. What is Quality Control?
  3. What do QC Programs ensure?
A
  1. Linearity
  2. Program that tests the performance of a CT scanner to ensure that it is performing at an optimal level and meeting standards.
  3. QC program ensures that the images produced by a CT scanner are optimal quality, while utilizing acceptable doses.
157
Q
  1. What does Performance Testing Include?
  2. What Quality Control parameters are tested?
A
  1. INITIAL testing that is performed when a CT scanner is installed, and the - ROUTINE testing that is performed either on a daily, weekly, monthly, or yearly basis.
  2. Contrast resolution
    Spatial resolution
    Noise
    Uniformity
    Accuracy of the laser
    Patient dose
    CT numbers
158
Q
  1. Routine vs Initial Testing:
  2. Who creates QC programs?
    - What is required in them?
  3. Who is involved in a QC Program?
A
  1. ROUTINE = Daily / Weekly / Monthly
    - By Physicist to ensure that factors that impact image quality and patient dose are within an acceptable limit.
    -*INITIAL = When Installed
    - By physicist to ensure that the CT scanner is operating at the specifications of the manufacturer.
  2. Each CT department create own QC program
    - Must meet the requirements and standards of accrediting bodies.
  3. Involves radiologists, technologists and physicists of an organization.
159
Q
  1. Optimal QC program consists of:
  2. Who Preforms Initial Performance Testing?
  3. Who Preforms Routine Performance Testing?
  4. Who preforms QC?
A

1.QC testing is completed on a regular basis.
- QC testing results are interpreted & corrective measures are taken ASAP
- QC testing records are accurate and stored for future reference.

  1. PHYSICIST
  2. PHYSICIST
  3. TECHS
160
Q
  1. QC PROGRAMS Consist of:
  2. How do Artifacts occur?
    - Image Result:
  3. Common Sources of Image Artifacts: (11)
A
  1. Performance Testing (Routine & Initial by Physists)
    - Quaity Control done Daily/Weekly/Monthly by Department
  2. Artifacts appear on an image as a result of errors in the measurement of the attenuated radiation by the detectors.
    - images that are incomplete and missing information.
  3. Beam Hardening, Partial Volume Averaging, Motion, Metal, Edge Gradient, Out of Field, Ring, Streaks, Tube Arcing, Cupping, Cone Beam
161
Q
  1. Beam Hardening Artifacts Caused By:
  2. How Does Beam Hardening Artifact appear on image?
  3. Can this artifact be compensated? If So How?
A
  1. Caused by increase in the average energy of the x-ray beam.
    - Denser object being imaged = more likely it is that lower energy photons are absorbed by object.
  2. Results in an artifact that appears on the CT image as areas of low attenuation with streaking.
  3. YES
    - Reconstructive Algorithms
162
Q
  1. Partial Volume Averaging Artifacts Caused By:
  2. How Does Partial Volume Artifact appear on image?
  3. Can this artifact be compensated? If So How?
A
  1. When there are tissues with different density that are captured within the same voxel.
    - (When multiple densities within a single voxel vary greatly or if a tissue is not completely imaged within a voxel - ONE CT # MADE)
  2. Partial volume artifacts appear as shaded areas within an image.
  3. YES
    - Use of thin and overlapping slices
163
Q
  1. How does Motion Artifact appear on an image?
  2. Types of Patient Motion?
    - Differences?
  3. How can you prevent / compensate for motion?
A
  1. Streaks, misregistration of information, blurring, or step artifact.
  2. voluntary or involuntary.
    - Involuntary motion = beating heart or tremors.
    - Voluntary = Patient can prevent
  3. Communicating with the patient both prior to and during the procedure.
    - Patient safety devices may immobilize a patient
    - Involentary = During Breathold
164
Q
  1. Which Artifact Appears as Streaks, misregistration of information, blurring, or step on image?
    - Hows it Compensated?
  2. Which Artifact Appears “shaded areas” on an image?
    - Hows it Compensated?
  3. Which Artifact Appears on the CT image as areas of low attenuation with streaking.
    - Hows it Compensated?
A
  1. MOTION
    - Communication, Immobilizers, Breatholds
  2. Partial Volume Artifact
    - Thin Slices
  3. Beam Hardening Artifact
    - Recon Algorithms
165
Q
  1. Which Artifact is caused by increase in the average energy of the x-ray beam.
  2. Which Artifact is caused when two objects of vastly different densities that are close together are imaged.
  3. Which Artifact is caused when multiple densities within a single voxel vary greatly or if a tissue is not completely imaged within a voxel
A
  1. Beam Hardening Artifact
  2. Edge Gradient Artifact
  3. Partial Volume Averaging Artifact
166
Q
  1. Metal Artifacts Caused By:
  2. How Do Metal Artifact appear on image?
  3. Can this artifact be compensated? If So How?
A
  1. Either implanted devices within a patient or metal objects that are within the scan field of view.
    - Result of beam hardening and/or partial volume averaging.
  2. Appear as streaks within an image
  3. Removing the metal when possible.
    - Utilizing thin sections.
    - Utilizing a higher kV.
    - Utilizing software that can reduce the impacts of the streaking. (MAR)
167
Q

1.Edge Gradient Artifacts Caused By:

  1. How Does Edge Gradient Artifacts appear on image?
  2. Where is this artifact typically occurring?
A
  1. When two objects of vastly different densities that are close together are imaged.
  2. Edge gradient artifacts appear as streaks within the
  3. Commonly found in areas where bone is surrounded by soft tissue.
168
Q
  1. What is Aliasing?
  2. Which Artifact Appear as a ring or series of rings within a CT image.
    - How Compensate / Fix?
  3. Which artifact appears as streaks on an image, typically in areas where bone is surrounded by soft tissue?
A
  1. Streak artifacts in an image arise when there is an issue with the detectors, or not enough data was collected for an image
  2. Ring-Artifact
    - Calibration / Maintence
  3. Edge Gradient Artifact
169
Q
  1. Out-Of-Field Artifacts Caused By:
  2. How Do Out-of-Field Artifact appear on image?
  3. Can this artifact be compensated? If So How?
A
  1. When a patient is positioned outside of the scan field of view.
  2. Streaking within the CT image, in the area that is outside of the SFOV.
  3. Adjusting the patient so that they are within the SFOV can help to overcome the out of field artifact.
    - Depending on the size of the patient, this may be an unavoidable outcome.
170
Q
  1. Ring Artifacts Caused By:
  2. How Do Ring Artifact appear on image?
  3. Can this artifact be compensated? If So How?
A
  1. When there is an issue with the detectors.
  2. Appear as a ring or series of rings within a CT image.
  3. Calibration of the CT scanner can help to overcome the issue, or service may need to be called to repair the issue.
171
Q
  1. Streak Artifacts are caused by:
  2. Streak Artifacts appear as:
  3. Tube Arcing Artifacts are caused by:
  4. Tube Arcing appears as:
    - How Compensated?
A
  1. When there is an issue with the detectors, or not enough data was collected for an image (Aliasing).
  2. Appear as lines across a CT image.
  3. When the x-ray tube undergoes a short-circuiting event.
  4. Appear as streaks on a CT image.
    - Requires repairs to CT scanner to prevent the artifact from recurring.
172
Q
  1. Which Artifact Occurs When the beam becomes harder in the center of the object being imaged than it does at the edge?
  2. Which artifact is due to short-cirucit of tube?
  3. Which Artifact appear as lines across a CT image?
A
  1. Cupping
  2. Tube Arcing Artifact
  3. Streak / Aliasing
173
Q
  1. When does Cupping Artifacts Occur?
  2. What Scan is this common in?
  3. Cone Beam Artifacts are More Prevalent Where?
A
  1. When the beam becomes harder in the center of the object being imaged than it does at the edge.
  2. CT Heads
  3. Outter Edges of Image
174
Q
  1. Cone Beam Artifacts Caused By:
  2. How Do Cone Beam Artifact appear on image?
  3. Can this artifact be compensated? If So How?
A
  1. When the CT scanner does not acquire enough data during the acquisition, and only occur with cone beam geometries.
  2. Appear on an image as shaded areas within an image.
    - More prevalent at the outer edges of an image than on the inner aspect of an image.
  3. With the use of reconstruction algorithms.
175
Q
  1. What does image compression help with?
  2. Two Types of Image Compression?
    -Difference?
  3. PACS stands for:
A
  1. Help to reduce the overall memory that CT images occupy in the storage of the computer.
  2. Lossless-the data is compressed without any loss of data.
    Lossy-the data is compressed with the loss of data.
  3. Picture Archival and Communication System (PACS)
176
Q
  1. Which Image compression results in loss of data?
    - Which does not lose data?
  2. PACS system is in communication with ____________.
    - Why is this important?
  3. Which System Scheduling patients, Storing patient orders, Patient billing & Starting and ending exam functions?
A

1.Lossless-the data is compressed without any loss of data.
Lossy-the data is compressed with the loss of data.

  1. Organizations EMR
    - Ensures that the patient demographics are accurate and consistent.
  2. RIS
177
Q
  1. What is EMR?
    - Communicates With?
  2. What is RIS?
    - Uses?
  3. How do images transfer from CT to PACS?
A
  1. The EMR is the patient’s electronic medical record. The EMR communicates with the . The RIS is used for:
  2. RIS, or the radiology information system. Functions:
    Scheduling patients
    Storing patient orders
    Patient billing
    Starting and ending exam functions
  3. Through the Network?
178
Q
  1. Define “ Network”
  2. Two Types?
    - Differences:
  3. What is required of these networks?
    - Why?
A
  1. Group of computers that are linked together and have the ability to communicate.
    • Local area network (LAN)– a network consisting of computers that are within the same area as one another.
      - Wide area network (WAN)– a network consisting of computers that are spread out and not within the same area as one another.
  3. SECURITY*
    - Firewalls & Encryption to ensure that the patient’s privacy and information is safe
179
Q
  1. LAN is used for computers that are _________________.
    - WAN is used for computers that are __________.
  2. What does DICOM Stand for?
  3. DICOM Function?
A
  1. LAN = CLOSE
    - WAN = FAR / Not In Same Area
  2. Digital Imaging and Communication in Medicine standards.
  3. DICOM ensures that medical data can easily be transferred and viewed from any device with viewing capabilities.
180
Q
  1. Is tape an appropriate way to minimize motion artifacts?
  2. The medium used to measure the light that is emitted from the scintillation crystal is called?
  3. When not enough data is acquired for a sufficient image to be produced, the MTF would be
    A. 0.2 B. 0.1 C. 1.0 D. 1.2
A
  1. NO - Use Communication Before & During / Or Immobilizer Devices
  2. PHOTODIODE (Think LIGHT = PHOTO)

3.B
- When MTF is equal to or less than 0.1= NO IMAGE

181
Q
  1. CT scanner to produce a motion free image is referred to as:
    a. Contrast resolution b. Temporal resolution
    c. Longitudinal spatial resolution d. In-plane spatial resolution
A
  1. B - TEMPORAL
182
Q
A

CT (7 decks)

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