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Radiology > Cone Beam CT: Part 1- The Basics > Flashcards

Cone Beam CT: Part 1- The Basics Flashcards

1
Q

What is image reconstruction?

A

Data is utilized by other software programs and produces different image presentations

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2
Q

What are the digital image processing/modifications?

A
  • Compression
  • Imaging manipulations (Automated image analysis)
    —Qualitative – changes pixel’s digital value
    —Quantitative – counts the number of pixels
  • Image Reconstruction
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3
Q

What is computed tomography (CT)?

A

Use of computers to generate multiple images of an object from digitized density information obtained from various signals; x radiation (MDCT, CBCT), magnetic fields (MRI), sonar radiation (ultrasound), etc.

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4
Q

What are the two main forms of x-ray CT?

A

-CBCT (Cone Beam Computed Tomography)
–MDCT (Multi Detector Computed Tomography)

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5
Q

Nearly all CBCT units are…

A

good quality high-end imaging equipment made for a very competitive marketplace

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6
Q

CBCT machines become outdated due to competition from competitor brands and technical innovations such as…

A
  • memory
  • bit depth
  • FOV options
  • operating systems
  • compatibility with software technologies
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7
Q

The lifetime of a CBCT unit is ___ years

A

6-8

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8
Q

CBCT has less radiation than other forms of CT (i.e. MDCT) for hard tissue imaging because of:

A
  • less scanning of X-radiation
  • lower radiation
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9
Q

1 day of background radiation ____µSv

A

~8.5

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10
Q

CBCT Dosimetry Study Values Vary
because Studies are not…

A

Directly Comparable

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11
Q

What are the factors affecting dose for the CBCT?

A
  • FOV
  • Exposure
  • Voxel
  • Sensors
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12
Q

What is a CBCT FOV flat panel detector?

A

Cylindrical shape and measurement characteristics
- Diameter (mm) x Height (mm)

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13
Q

What is a CBCT FOV image intensifier detector?

A

Round spherical shape and measurement characteristics
- Diameter (mm) only

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14
Q

CBCT units have capabilities for scanning a range of _______ sizes

A

FOV

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15
Q

What is the range of kV for a CBCT?

A

ranges between various units
75 kV – 120 kV

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16
Q

What is the range of mA for a CBCT?

A

7 mA – 20 mA

17
Q

How does the image production for CBCT work?

A
  • X-ray beam projection scheme shows “cone” beam (left) imaging geometry with the resultant image production.
  • Multiple basis image projections form the projection data.
  • A volumetric data set is then constructed by an imaging software program which then displays various image reconstructions.
18
Q

Multiple basis image projections form the…

A

projection data

19
Q

A _______________ is constructed by an imaging software program which then displays various image reconstructions.

A

volumetric data set

20
Q

What is the CBCT basis-image capture sequence?

A

Two basis-image capture sequences as the machine rotates counterclockwise from Position 1 to Position 2

21
Q

What is the range of images the CBCT basis-image captures?

A

scans routinely capture in the range of 100 to 600 basis images per rotational scan

22
Q

Number of basis images in a CBCT affects…

A
  1. Image Quality
  2. Dose
23
Q

What does the voxel size do?

A

increased voxel size…
- worse resolution

24
Q

small voxel yields _____ resolution

A

high

25
Q

What is the typical voxel size for a CBCT?

A
  • 0.3mm3 = 300µm3
  • 0.075mm3 = 75 µm3
26
Q

Small voxel yields LOWER signal to noise ratio, i.e., degraded image _________

A

quality

27
Q

Small voxel yields ________ radiation dose

A

high

28
Q

What is the threshold for a small versus large FOV when considering voxel size?

A

> 0.200mm = 200µm – for larger FOVs

<0.200mm = 200 µm – for smaller FOVs

29
Q

Small voxel yields high resolution but requires more __________________ to capture signal in the greater number of the smaller voxels

A

x-ray photons (higher exposure)

30
Q

Current scanners are not configured for the longer scan times and longer processing times for a _______ FOV with a ______ voxel size

A

large
small

31
Q

Smaller voxels need more photon signal which yields a ______ radiation dose

A

higher

32
Q

What are the different types of CBCT image detectors?

A
  • charge-coupled image intensifier detector
  • flat-panel detector
33
Q

Charge-coupled image intensifier detector has distortion of the image grid when moving __________ the center

A

away from

34
Q

Do flat panel decectors have distortion?

A

Even at more distant areas from the center of the grid, there is minimal to no distortion of the grid pattern.

35
Q

Flat panel image receptor area receiving the signal from the
flat-panel detector’s __________ is flat.

A

scintillator

36
Q

Improved image quality and the higher signal-to noise ratio are noted in which type of detector?

A

flat-panel detector

37
Q

Lower radiation dose for which type of detector?

A

Charge-coupled device image intensifier

Radiology (39 decks)

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