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Imaging science and technology > Ct Flashcards > Flashcards

Ct Flashcards

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1
Q

What is Dynamic CT?

A

The process of producing a cross-sectional image of the body using a collimated beam of radiation that rotates around the patient.

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2
Q

What is Enhanced CT?

A

The use of a contrast agent to improve the appearance of vessels or organs that are similar in density to the surrounding tissues.

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3
Q

Define Field of View in CT imaging.

A

The part of the scanned plane which may be included in the final image.

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4
Q

What does ‘Helical’ refer to in CT terminology?

A

Spiral.

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5
Q

What is Image Acquisition?

A

The collection of data in order to produce an image.

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6
Q

Define Image Format.

A

The process of storing an image on computer disk, magnetic tape, film, or on the World Wide Web.

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7
Q

What is Image Manipulation?

A

To digitally change the appearance of the acquired image in order to improve it.

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8
Q

Define Image Reconstruction.

A

The process of generating an image from raw data or a set of unprocessed measurements.

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9
Q

What does Isotropic mean?

A

Having the same properties in all directions, e.g., density.

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10
Q

What is a Matrix in the context of imaging?

A

The columns and rows that form a digital image.

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11
Q

What is Mean Window Level?

A

The average range of pixel values in an image.

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12
Q

Define Noise in imaging.

A

Anything that distracts from the information required on an image.

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13
Q

What is a Nutating Detector Ring?

A

When the detectors vibrate in such a way as to keep the detectors nearest the tube out of the way of the X-ray beam.

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14
Q

What does Pitch refer to in CT imaging?

A

The table movement during one complete rotation of 360° divided by the column width (or slice thickness).

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15
Q

Fill in the blank: A Pixel is a _______.

A

two dimensional ‘picture cell’ or ‘dot’ that makes up the image on a digital display screen.

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16
Q

What is a Profile in imaging?

A

Line of data.

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17
Q

Define Slice in the context of CT.

A

A section through the patient which is recorded when the X-ray tube and detector make one complete rotation.

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18
Q

What is Slice Interval?

A

The distance between reconstructed slices.

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19
Q

What does Spatial Resolution refer to?

A

The smallest part of an image that can be seen.

20
Q

Fill in the blank: A Voxel is a _______.

A

three dimensional pixel.

21
Q

What is a Window in imaging?

A

The range of colour (or grey) scale values displayed on a digital image.

22
Q

What is Window Width?

A

The range of pixel values displayed in the digital image.

23
Q

Define Gantry in CT.

A

A circular device for holding the detectors.

24
Q

What is the function of the X-ray Tube?

A

A method of producing X-rays which are collimated so that they are aligned to a specific number of detectors.

25
Q

What are Detectors in CT?

A

Solid state devices containing caesium iodide crystals which collect the amount of radiation transmitted through the patient.

26
Q

What is the role of Photomultipliers?

A

A device for increasing the number of electrons produced from photons hitting a cathode.

27
Q

What is a Photodiode?

A

A light-controlled variable resistance that allows current flow in direct proportion to the quantity of light it is exposed to.

28
Q

Describe the Housing in CT machines.

A

A ‘doughnut’ shaped structure which contains the X-ray tube and the detectors.

29
Q

What was the original movement mechanism in CT machines?

A

High tension cables wound round a drum, which were replaced with slip ring and brushes.

30
Q

What is the purpose of the Table in CT?

A

For the patient to lie on and can move forward at a predetermined distance or at a constant speed.

31
Q

What does the Operator Console allow?

A

Where the operator can determine the settings for the scan.

32
Q

What is the Tomographic Principle?

A

The X-ray tube and detector move together and rotate around a set point, keeping that point in focus while blurring structures above and below.

33
Q

What is a Narrow Window in imaging?

A

The grey is distributed over a narrow range of units centered around the average HU for the structure of interest.

34
Q

What is a Wide Window in imaging?

A

The grey is distributed over a wide range of units centered around the average HU for the structure of interest.

35
Q

What is high density tissue?

A

(Bone), absorbs the radiation to a greater degree, and a reduced amount is detected by the scanner on the opposite side of the body

36
Q

What is low density tissue?

A

(Lungs) absorbs the radiation to a lesser degree, and there is a greater signal detected by the scanner

37
Q

Why is contrast often used in CT?

A

° used to visualise the cardiovascular system (e.g. investigating for suspected aneurysms, dissections)

° used to identity whether a tumour is malignant

38
Q

What does the density of body tissue determine?

A

The degree to which the X-rays are attenuated.in turn this affects the brightness and contrast of the imaged tissues.

39
Q

How do diff. Attenuation coefficients look on a CT

A

° high #attenuation coefficient tissues ( strong absorption) show up white, and law attenuation coefficients (weak absorption) show up black. This is quantified by hounsfield scale of radiodensity tissues with a high household unit have a high attenuation coefficient so look while.

40
Q

What are the household values for air, fat, water, blood and bone?

A

° air = - 1000

° fat = - 70

° water = O

° blood = 70

° bone = 1000

41
Q

What is volume rendering?

A

Voxel HU’s are coded with colour and transparency

42
Q

What is surface rendering?

A

Creates a one or more iso-surface (s) from voxels of same level.

43
Q

Benefits of CT regarding medical management.

A
  • determining when surgeries are necessary
  • reducing the need for exploratory surgeries
  • improving cancer diagnosis and treatment
  • reducing the length of hospitalisations
  • guiding treatment of common conditions e.g. injury, cardiac disease, stroke.
  • Improving patient placement into appropriate areas of care, such as intensive care units
44
Q

What are the principle advantages of CT?

A
  • Rapid acquisition of images
  • a wealth of clear and specific information
  • a view of a large portion of the body
45
Q

What are some of the basic components of a CT scanner?

A
  • Gantry aperture (720mm)
  • microphone
  • sagittal laser alignment
  • patient guide lights
  • XR exposure indicator
  • Emergency stop buttons
  • Gantry control panels
  • external laser alignment
  • patient couch
  • ECG gating monitor

Imaging science and technology (6 decks)

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