CT Hardware & System Operation

Question 1

What does the detectors convert the number of photons that pass through the patient into?

Answer 1

Tiny electrical signals that represents the attenuation information of the body

Question 2

What is the operator’s console used for?

Answer 2

Viewing images
Post-processing images
Archiving images
Filming images
Patient registration

Question 3

Where is the CT raw data storage device located?

Answer 3

Host computer

Question 4

The patient table moves so that the anatomical region we want to scan always aligns with:

Answer 4

The beam of x-ray photons

Question 5

In what ways can a gantry move?

Answer 5

By rotation and angling

Question 6

Why would a gantry be angled?

Answer 6

To select oblique slices through the anatomy

Question 7

What determines the number of electrons that flow from the cathode to the anode?

Answer 7

Temperature of the cathode filament

Question 8

Why does the anode rotate?

Answer 8

Great amount of heat

Question 9

Tube currents are generally selected in the range of:

Answer 9

Tens to hundreds of milliamperes (mA)

Question 10

How does mA and photons correlate to one another?

Answer 10

The greater the mA, the more photons are produced

Question 11

The energy level of the x-ray photons determines how:

Answer 11

Easily they will penetrate the patient’s body

Question 12

Tube voltages are generally selected in the range of:

Answer 12

90 to 140 kilovolts (kV)

Question 13

How does kV and photons correlate to one another?

Answer 13

The greater the kV, the more penetrating the photons will be.

Question 14

The only opening in the tube housing that allows passage of the x-ray photons

Answer 14

Tube Window

Question 15

What are collimators made of?

Answer 15

X-ray opaque material

Question 16

Collimations restricts x-rays to only:

Answer 16

The selected cross-sectional region

Question 17

What is the difference between pre-patient collimation on a single-row detector scanner versus a multi-row detector?

Answer 17

On a single-row detector scanner, the thickness of the cross-sectional slice is determined by the collimation
On a MDCT, the slice thickness is determined during image reconstruction

Question 18

Which type of collimation acts to minimize scatter radiation as well as minimizing dose of ionizing radiation administered to the patient?

Answer 18

Pre-patient

Question 19

Which type of collimation acts to minimize scatter radiation as well as provides better definition to the slice thickness?

Answer 19

Post-patient

Question 20

Post-patient collimation is also referred to as:

Answer 20

Pre-detector Collimation

Question 21

For an x-ray photon to generate a signal, it must:

Answer 21

Enter the detector
Collide with a detector atom
Produce a measurable event

Question 22

What are the two basic categories of detectors?

Answer 22

Gas and solid state

Question 23

What is the gas used in a gas detector?

Answer 23

Xenon

Question 24

Having a large distance between xenon atoms could _____ the chance of x-ray production.

Answer 24

Decrease

Question 25

Xenon gas is pressurized by up to __ times normal atmospheric pressure.

Answer 25

30

Question 26

What happens when an incoming photon collides with a xenon atom?

Answer 26

That atom splits into a xenon ion and an electron

Question 27

What is the charge of a xenon ion?

Answer 27

Positive

Question 28

When charged particles migrate to the plate with the opposite polarity, what can this be measured as?

Answer 28

An electrical pulse

Question 29

Xenon detectors have only been used in which generation scanners?

Answer 29

Third-generation due to the chamber aligning straight onto the CT x-ray tube at all times

Question 30

Which detector is the most prevalent type of detector used on today’s CT scanners?

Answer 30

Solid state

Question 31

A solid state detector is also referred to as:

Answer 31

Scintillation detector

Question 32

What happens when a photon strikes with the solid state material of a detector?

Answer 32

It emits a flash of light converting into an electrical impulse by a photodiode

Question 33

On MDCT scanners, how do you calculate the acquired slice thickness?

Answer 33

The thickness of the x-ray beam divided by the total number of slices acquired in a single rotation

Question 34

What are the two different approaches for varying the acquired slice thickness?

Answer 34

Symmetric / Asymmetric detector arrays

Question 35

How does DICOM and PACS relate to one another?

Answer 35

DICOM is neccessary for the transfer of data that occurs with PACS

Question 36

Through which part of the CT x-ray tube do the electrons enter?

Answer 36

Cathode terminal

Question 37

What control does the operator have over the x-rays in a CT exam?

Answer 37

Energy level and quantity of x-rays can be selected

Question 38

What is the purpose of the tube window?

Answer 38

To allow x-rays to exit the tube

Question 39

How is collimation accomplished?

Answer 39

By physically blocking x-rays

Question 40

What affects the slice thickness on a single-row detector scanner?

Answer 40

Size of cathode filament
Size of focal spot (dependent on size of cathode filament)
Collimation thickness

Question 41

The signals measured at the detectors must be digitized after they are amplified which is done by the:

Answer 41

Array processor

Question 42

How do gas detectors create an electrical event?

Answer 42

By ionizing the detector material (an electrical event) when struck by a photon

Question 43

How can an MDCT scanner obtain thicker slices?

Answer 43

The attenuation information from detectors in more than one detector array may be added together