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Radiation Physics > Special Imaging > Flashcards

Special Imaging Flashcards

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1
Q

What does CT stand for?

A

Computerized Tomography

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2
Q

What is CT (computerized tomography) also known as?

A

Computerized axial tomography (CAT)

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3
Q

What does a CT scan do?

A

Diagnostic imaging procedure that uses x-rays to present a cross-sectional image “slices” of the body

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4
Q

What are the cross sections reconstructed from?

A

Measurements of Attenuation coefficients (this calculates the ability of x-rays to pass through tissues)

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5
Q

What calculates the ability of x-rays to pass through tissues or being weakened or _____ by the tissues?

A

Attenuation coefficients

- Attenuated

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6
Q

CT is based on what fundamental principle?

A

The density of tissue that is passed by the x-ray beam is able to be measured from a calculation of the attentuation coefficients!

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7
Q

T/F: The emitter of x-rays rotates around the patient and the detector, placed in diametrically same sides.

A

FALSE

- The emitter of x-rays rotates around the patient and the detector, placed in diametrically OPPOSITE sides

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8
Q

T/F: Unlike x-ray radiography, detectors of the CT scanner do not produce an image

A

TRUE

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9
Q

CT scanners will measure the transmission of a thin beam, how thin is it?

A

1-10mm slices

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10
Q

The image of the certain section being imaged is taken from different angles, which allows the information to be viewed at a certain depth…. what depth is this? (i.e. 1-d, 2-d, 3-d)

A

3-dimension

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11
Q

T/F: CT scanning allows you to view body sections in all available planes and three dimensional imaging.

A

TRUE

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12
Q

What is each square in the image matrix called?

A

Pixel

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13
Q

What is the tiny elongated block of tissue known as?

A

Voxel

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14
Q

T/F: The size of the pixel was not determined by the computer program, but determined by the dimensions of the x-ray beam.

A

FALSE

- The size of pixel was determined by the computer program and NOT by the dimensions of x-ray beam

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15
Q

T/F: CT slice thickness is determined by computer programming and not the x-rays themselves.

A

TRUE

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16
Q

What are the units used in CT scans?

A
  • Hounsfield units (HU)
  • These are determined by the intensity of x-ray attenuation coefficient in tissues of different densities that can be a reliable measure of different compositions of body tissues
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17
Q

In HU, what are the measurements of Air, Fat, Water, Compact bone…

A

Air = -1000HU
Fat = -60 to -120 HU
Water = 0 HU
Compact Bone = + 1000 HU

18
Q

Who pioneered the CT scan?

A

Sir Godfrey Hounsfield - Nobel Prize in 1979

19
Q

Clinical application and indication for CT scanning?

A
  • Head/Neck Pathology + paranasal sinuses
  • CTA-CT angiography
  • Chest and abdomen
  • Imaging of acute trauma: fractures/dislocations
  • CT is also used if MRI or other imaging is contraindicated
  • Note: CT axial slices are modality of choice for investigating head trauma and cerebrovascular events (stroke)
20
Q

Neck Ct+C is used in the diagnosis or what?

A

Lymphoma and Head/Neck Neoplasms

21
Q

T/F: For cervical and other skeletal trauma CT imaging w/o contrast is the modality of choice especially if plain radiographs are unrewarding or require further special imaging.

A

TRUE

- ex. sagittal reconstruction of a cervical spine CT showing flexion teardrop fracture at C5

22
Q

Correct ID of various radiographic densities referring to HU scale will help with accurate diagnosis and clinical management. If looking at a axial cut of a liver, what could one find?

A

Lipoma within the liver

23
Q

What does MRI stand for?

A

Magnetic Resonance Imaging

24
Q

T/F: Like CT an MRI helps look at the body within different planes.

A

TRUE

25
Q

What two views are most helpful in an MRI?

A

Coronal, Sagittal

26
Q

MRI uses what for imaging instead of radiation?

A

Detects magnetic changes in hydrogen atoms

27
Q

T/F: Carbon is the most abundant in both water and fat.

A

FALSE

- Hydrogen is the most abundant

28
Q

MRI uses two common sequences, what are they?

A
  • T1 weighted image - fat is bright

- T2 weighted image - water is bright

29
Q

Which weighted image is used for visualizing and appreciating normal anatomy?

A

T1

30
Q

Which weighted image method is used for detecting disease process, since most pathologies lead to cell damage with inflammation and edema seen as bright or high signal intensity on __ and other fluid sensitive pulse sequences.

A

T2

31
Q

What is based on imaging of protons?

A

MRI

32
Q

T/F: In general Hydrogen atoms show strong (-) charge and spin at varied frequency along their own small EM field.

A

FALSE

  • Hydrogen atoms show (+) charge
  • and spin at CONSTANT frequency along their own small EM field.
33
Q

T/F: When a strong magnet is applied N>S pole, protons line up along the stronger magnetic axis just like the needle of a compass.

A

TRUE

34
Q

Which scan can be explained as the “Spinning Top” analogy?

A

MRI

35
Q
  • In the MRI scanner an external radio-frequency of the same frequency as the spinning protons is applied and the protons will then absorb this energy and become energized and being to resonate
  • The external radiofrequency will then be “turned off” and the protons begin to decay or revert back to their original energy
  • The decay frequency is then received as a radio wave and converted or digitized by the computer creating an image that depends on the number of protons in different tissues.
A

How an MRI works

36
Q

What are loops of wire/thin conductive sheets on a cylindrical shell lying just inside the MRI scanner?

A

Gradients

37
Q

What happens when a current is passed through these coils?

A

Secondary magnetic field is created

38
Q

What is the primary function of gradients?

A
  • It allows spatial encoding of the MR signal
  • These are also critical for a wide range of physiologic techniques such as MR angiography, diffusion, and perfusion imaging
39
Q

What are used to receive and transmit signal, from the patient in respect to an MRI?

A

Patient coils

40
Q

_____ coils are the “antenna” of the MRI system. These coild can broadcast the RF signal to the patient and/or receive the returned signal.

A

Radiofrequency

41
Q

T/F: MRI is far superior to any other imaging in detecting variations in soft tissue anatomic details.

A

TRUE

42
Q

T/F: MRI is particularly helpful in detecting pathology of muscles, ligaments, soft tissues of the solid organs, bone marrow and the brain.

A

TRUE

Radiation Physics (5 decks)

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