IMAGING SYSTEM DESIGN Flashcards

1
Q

3 MAJOR COMPONENTS

A

1.) Gantry
2.) Operating Console
3.) Computer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

 Largest component

A

GANTRY

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Subsystems:

A

x-ray tube, detector array, high
voltage generator, patient couch and
mechanical support

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

X-RAY TUBE
 Special requirements:
o Power capacity: must be high
___ kVp
 ___ mA

A

> 120
400

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

X-RAY TUBE
 Special requirements:
High speed rotors: for

A

heat
dissipation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

X-RAY TUBE
Anode heat capacity: __MHU
(Spiral CT)

A

7 MHU

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

X-RAY TUBE
Heat storage capacity: _- MHU

A

8

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

X-RAY TUBE
Anode cooling rates: __MHU/min

A

1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

X-RAY TUBE
Focal spot size:
Focal spot design: must be
robust or strong
 Heat dissipation

A

small

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

X-ray tube life: approx.___
exposures (Conventional CT)

A

5000

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

CT scanners
designed for____ imaging not for
direct projection imaging

A

high spatial
resolution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

o Design to predict the focal spot
thermal state
o To adjust the mA setting accordingly

A

Focal-Spot Cooling Algorithms:

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

o The entire collection of detectors
o Group of detectors
o The image receptor in CT

A

DETECTORY ARRAY

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

absorbs radiation and converts it
to electrical signal

A

Detector:

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

 The ability of the detector to
capture transmitted photons and change them to electronic
signals

A

High detector efficiency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

 A brief, persistent flash of
scintillation that must be
taken into account &
subtracted before image
reconstruction

A

Low or no after glow

17
Q

Optimal Characteristics: OF DETECTOR

A

High detector efficiency
Low or no after glow
High scatter suppression
o High stability

18
Q

 Allows a system to be used
without interruption of
frequent calibration

A

High stability

19
Q

2 TYPES OF DETECTOR

A

Gas-filled detector – previously used
o Scintillation & solid-state detectors –
recently used

20
Q

o Basis: ionization of gas

o Characteristics:
 Excellent stability
 Large dynamic range
 Low quantum efficiency

A

Gas detector:

21
Q

Three types: OF DETECTOR

A

 Ionization chamber
 Proportional counter
 Geiger-Muller counter

22
Q

Scintillation detector: CRYSTAL USED

A

SODIUM IODIDE

23
Q

detector:
o Characteristic: high x-ray detection
efficiency (90%)
 Reduces patient dose
 Allows faster imaging time
 Improves image quality

A

Scintillation

24
Q

Scintillation detector: Replaced by:
 (BGO)
 (CsI)

A

Bismuth germinate
Cesium iodide

25
Q

SCINTILLATION DETECTOR Current crystal of choice:
 (CdWO4)

A

Cadmium tungstate
Special ceramics

26
Q

converts light into electrical
signal

A

Photodiode:

27
Q

Characteristics: OF PHOTODIODE

A

Small,
 Cheap
 Does not require power
supply

28
Q

THREE IMPORTANT FACTORS
CONTRIBUTING TO DETECTOR EFFICIENCY

A

GEOMETRIC EFFICIENCY
QUANTUM
CONVERSION

29
Q

 The product of geometric, quantum and
conversion efficiency

A

OVERALL/DOSE EFFICIENCY

30
Q

The product of the following factors
o

A

Stopping power of the detector
material
o Scintillator efficiency (in solid-state
types)
o Charge collection efficiency (in
xenon types)
o Geometric efficiency
o Scatter rejection

31
Q

Normal value: b/n ___

A

0.45-0.85

32
Q

Value <__: non ideal detector system
o Result: increased in patient dose to
maintain image quality

A

1

33
Q

 Refers to the ability with which the detector
obtains photons that have passed through the
patient

A

CAPTURE EFFICIENCY

34
Q

 Refers to the number of photons absorbed
by the detector
 Depends on: physical properties of the
detector face
o Thickness
o Material

A

ABSORPTION EFFICIENCY