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NMIS Instrumentation II > Block 1 > Flashcards

Block 1 Flashcards

1
Q

The basic framework consists of a collimated detector system capable of acquiring data at varying degrees within a

A

360° Radius, ADC conversion

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2
Q

Choice of collimator changes the

A

Image resolution

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3
Q

Does spect improve sensitivity or specificity

A

Sensitivity and specificity

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4
Q

Which two areas are CT used

A

SPECT- Thallium etc. & PET - Rubidium etc.

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5
Q

One limitation of SPECT/scintillation cam

A

It depicts 3D images in 2D until after reconstruction

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6
Q

SPECT Removes

A

Out of plane information

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7
Q

Which collimator is used for SPECT

A

Parallel hole

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8
Q

What focal slices are done with SPECT

A

Transverse, coronal, sagital

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9
Q

SPECT stands for

A

Single photon emission computed tomography

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10
Q

Two limitations to SPECT

A

Limited number of projection angles and the in-focus plane image still is obscured by counts from the former

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11
Q

Does the parallel.hole collimator change image size?

A

No it stays the same, no mag or min

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12
Q

Transverse is also called

A

Short axis

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13
Q

What increments are the data stored in

A

64 x 64
128 x 128
256 x 256 matrix

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14
Q

Describe each image plane

A

Coronal- front to back
Saggital- left and right
Transverse- superior and inferior

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15
Q

Most popular way to do SPECT

A

With a rotating Anger/angle camera mounted on a gantry that allows 360° rotation

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16
Q

Most common detector system

A

Two or three heads which increase sensitivity

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17
Q

T or F: a detector acquires data from a thin axial section containing radioactivity by linear scanning from multiple directions around the cross section

A

True

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18
Q

What is a projection

A

The counts of the detector at different positions along a scan line at different angles

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19
Q

Multiplying for matrix size example

A

Example: 8x8 is 64

So 64x64 is 4096
128x128 is 16384
256x256 is 65536

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20
Q

Pixel width determines the

A

Resolution

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21
Q

Reducing pixel width improves

A

Resolution

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22
Q

If you reduce pixel width…

A

Resolution increases, sensitivity decreases

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23
Q

Cardiac SPECT looks at which area of the heart

A

Left ventricle. Due to the blood flow.

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24
Q

CT versus SPECT degree radius

A

CT does 180° SPECT does 360°

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25
Q

Two effects of spatial resolution

A

First the image is blurred the second effect is more subtle.

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26
Q

Scatter effects

A

The photons detected in SPECT and PET are electromagnetic radiation.

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27
Q

Two major types of interactions

A

Photoelectric effect and Compton scattering

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28
Q

The photoelectric effect results in…

A

Complete absorption of the photon, reducing the observed count rate, although scattered photons may still be detected.

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29
Q

To reduce Compton scatter

A

Use narrower pulse height windows

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30
Q

Ideal image peaks

A

Narrow tall peaks

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31
Q

Attenuation

A

Cold spot or loss of photons by a combination of photoelectric and Compton scatter

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32
Q

The higher the number of counts in a reconstructed image…

A

The less smoothing or cutoff a window function should have

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33
Q

One of the commercially available types of filter window combinations is the

A

Ramp Hann

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34
Q

A window function is used to improve the……. ratio in the reconstructions

A

S to N ratio

35
Q

Filters are used to eliminate
…. and ….. so that we only get target material

A

Noise and background

36
Q

When a point source is projected into each pixel representative of the acquired angle, a ……. suppresses the ….. effect

A

Ramp filter and star effect

37
Q

We might define frequency as the ………. or cycles per pixel or centimeter

A

Number of peaks per unit distance

38
Q

Which filter is the mathematically perfect filter

A

The ramp filter

39
Q

Which correction is the most important QC procedure in SPECT

A

Uniformity correction

40
Q

What is this showing?

A

A “bulls-eye” on a uniformity correction which shows a decreased number of counts on a 360° image

41
Q

Is this aligned or misaligned

A

Misaligned

42
Q

Is this aligned or misaligned

A

Aligned

43
Q

Center of rotation errors are fixed by

A

Specialists

44
Q

Is this aligned or misaligned

A

Misaligned

45
Q

What artifact is only seen on a 180° rotation SPECT QC

A

The “tuning fork”

46
Q

Which artifact is shown on a 360° rotation QC image

A

The bulls eye

47
Q

Benefit of spect

A

Improved contrast. Able to see organ edges

48
Q

SPECT facts

A

Has no effect on spatial resolution, provides quantitative measurements, not higher radiation to patient

49
Q

What determines the number of stops in step and shoot method

A

Matrix

50
Q

Other names for transverse, sagittal and coronal

A

Axial
Lateral
Frontal

51
Q

2 systems with spect

A

Rotating camera system
Ring camera system
(Ohjay camera)

52
Q

3 important considerations in acquisition that pertains to scan time

A

Pixel width
Number of pixels
Number of linear scans

53
Q

2 or 3 camera heads improve

A

Sensitivity, ability to do the scan

54
Q

Heart wall attenuation

A

Anterior- breasts
Lateral- fat
Posterior- diaphragm/fat

55
Q

Way to remember heart slices
ALPS, AAPB, ALBS.

A

ALPS anterior to posterior
AAPB septal to lateral
ALBS posterior to anterior wall

56
Q

Factors that effect image appearance

A

Attenuation of photons
Spatial resolution
Detection of scattered photons
Accidental counting
Noise

57
Q

Spatial resolution

A

The ability of a scanner to tell the difference between 2 objects

58
Q

Photoelectric effect

A

Complete absorption of a photon

59
Q

To reduce scatter

A

Narrow the pulse height window

60
Q

What degrades spect images and what makes up for this

A

Noise, limited counts, attenuation. Filters make up for this

61
Q

Imaging technique that gives cross sectional images

A

CT

62
Q

Term applied to pixels in image

A

Filter

63
Q

Filters are used to

A

Reduce noise

64
Q

Back projection is also referred to as

A

Brute force

65
Q

_____ is replacing FBP

A

Iterative reconstruction

66
Q

_____ is a form of disteria

A

Noise

67
Q

___< filter is used for FBP and gets rid of star

A

Ramp

68
Q

Label

A
69
Q

Higher the _________ the sharper the image

A

Frequency

70
Q

Ramp filter gets rid of

A

Low frequency, and background

71
Q

Higher the number of _____ in an image the less smoothing

A

Counts

72
Q

Resolution _____ as pixel volume ______

A

Decrease. Increase

73
Q

What phantom is used for spect qc

A

Jasczack phantom

74
Q

QC is a _____ factor

A

Critical

75
Q

What artifact do you get when COR is off

A

Ring

76
Q

Uniformity Cor artifact is

A

Bullseye NOT ring

77
Q

COR qc is done

A

Weekly

78
Q

Number of counts per sec for 1st pass

A

150,000-200,000

79
Q

What mode stores data based on physiological markers

A

List mode, gives most flexibility

80
Q

______ filter allows smooth transition between frames

A

Temporal

81
Q

Spatial filter removes

A

Noise

82
Q

Counts per matrix

A

64 matrix 30m
128 matrix 120m
256 matrix 480 m

83
Q

True transaxial tomography with nuc med

A

SPECT

NMIS Instrumentation II (1 decks)

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