CT Instrumentation part 1

Question 1

Were the first Gen CT scanners able to rotate all the way around a patient?

Answer 1

No. They used cables to power the tube in the gantry and had to be reset after exposure.

Question 2

Which CT scanner generations were known as “translate-rotate”?

Answer 2

First Gen and Second Gen. The tube first “translated” across the patient and then the gantry “rotated” to the next position.

Question 3

Which CT scanner generation had a “pencil beam”?

Answer 3

First Gen

Question 4

Which scanner generation was limited to only scanning heads?

Answer 4

First Gen

Question 5

Which ct scanner generation was the first to utilize a fan beam?

Answer 5

Second Generation

Question 6

Which ct scanner generation used “rotate-rotate” technology?

Answer 6

Third Generation - both the tube and the detector array rotated around the patient

Question 7

Which generation of CT scanners operated under the principle of “rotate-stationary”?

Answer 7

Fourth Generation

Question 8

What kind of scanner does “EBCT” refer to?

Answer 8

Electron Beam CT

Question 9

Does the Electron Beam CT scanner use an x-ray tube?

Answer 9

No, it does not. And all of it’s parts are stationary

Question 10

What kind of studies does EBCT (electron beam CT) accel at?

Answer 10

cardiac imaging and anatomy and function scans

Question 11

Which scanner generation has a focusing and deflection coil?

Answer 11

Fifth Generation (EBCT). The electrons get focused and deflected

Question 12

Which ct scanner generation was known as EBCT?

Answer 12

Fifth Gen

Question 13

The scanner that generates x-rays as a result of a high=speed electron beam bombarding stationary target rings is called a ______ scanner.

Answer 13

EBCT

Question 14

Which of the following scanner generations first introduced the concept of whole body scanning (1st, 2nd, 3rd, 4th)?

Answer 14

Second Gen

Question 15

What “system” are the following a part of: rotating scan frame, x-ray generator and tube, colimators, beam filter, detectors and DAS, and slip rings?

Answer 15

The Imaging System

Question 16

Do ct scanners use three phase 12-pulse or high frequency generators?

Answer 16

The first scanners used three phase 12 pulse but modern scanners use High Frequency

Question 17

What kVp range to CT x-ray tubes operate in?

Answer 17

120-140 kVp

Question 18

What does the “RTM” in the RTM alloy anode of the ct x-ray tube stand for?

Answer 18

Rhenium Tungsten Molybdenum

Question 19

Do CT x-ray tubes have a shorter or longer life than diagnostic x-ray tubes and why?

Answer 19

CT tubes have a shorter life because of the tremendous amount of heat that is produced

Question 20

Do CT tubes have large and small focal spots like diagnostic tubes?

Answer 20

Why yes, they do.

Question 21

what unit does the following formula produce: mA x Time x kVp x GF (Generator Factor)?

Answer 21

HU or Heat units

Question 22

What is the formula to calculate Heat Units (HU)

Answer 22

mA x Time x kVp x Generator Factor (GF)

Question 23

What is the main purpose of the Filters in the CT system?

Answer 23

They ‘shape’ the beam by harening it to make it more uniform and less polyenergetic

Question 24

What material are filters usually made out of?

Answer 24

Copper and aluminum

Question 25

In single slice acquisition what mechanical device defines slice thickness?

Answer 25

The pre-patient collimators

Question 26

Does the pre-patient collimator help to reduce patient dose?

Answer 26

Yes, it does.

Question 27

What determines the slice thickness in a multislice CT?

Answer 27

The detector aperture

Question 28

What are three advantages of slip ring technology?

Answer 28

Faster Scan times, Less delay between scans, eliminates start-stop motion problems

Question 29

The purpose of filtration in CT is to: (absorb "hard" radiation, increase beam quality, produce a more heterogeneous beam, or deflect photons)

Answer 29

Increase beam quality (make it more homogeneous)

Question 30

Pre-patient commimators: (increase the energy of the beam, cause the beam to be heterogeneous, reduce patient dose, reduce scatter reaching the detector)

Answer 30

Reduce patient dose

Question 31

Post-patient collimators (increase the energy of the beam, cause the beam to be heterogeneous, reduce patient dose, reduce scatter reaching the detector)

Answer 31

Reduce scatter reaching the detector

Question 32

Which of the following affects slice thickness in single slice CT? (beam filters, beam collimators, x-ray tube, generator)

Answer 32

Beam collimators

Question 33

Development of ______ allowed CT scanners to operate using a 360 degree rotation of the x-ray tube (crystal detectors, beam collimators, fiberoptics, slip rings)

Answer 33

Slip rings

Question 34

Efficiency, Response Time, Dynamic Range, and Stability & Reproducibility are all characteristics of this "D" word.

Answer 34

Detectors

Question 35

The ratio of the largest to smallest signal that can be detected in the detector array is know as the _____ range.

Answer 35

Dynamic

Question 36

What are the two main types of CT detectors?

Answer 36

Xenon & Solid State

Question 37

What is the other "S" name for Solid State Detectors?

Answer 37

Scintillation

Question 38

What is the other name for Xenon detectors

Answer 38

Gas Ionization Detectors

Question 39

High detection efficiency and remembering the amount of radiation sensed are two advantages of what type of detector?

Answer 39

Scintillation or Solid State detectors

Question 40

More expensive, Afterglow with Sodium Iodide (NaI) [not used anymore], must be re-calibrated between patients if using PM (photomultiplier) tube [not common], and aging problems are all disadvantages of this type of detector.

Answer 40

Scintillation or Solid State Detectors

Question 41

Simple, compact, costs less, no afterglow are all advantages of this kind of detector.

Answer 41

Gas Ionization or Xenon Detectors

Question 42

What is the primary disadvantage of Gas Ionization (xenon) detectors?

Answer 42

They are less efficient than their Solid State (scintillation) detectors

Question 43

What type of detectors are used with 4th Gen CT scanners?

Answer 43

Solid State or Scintillation Detectors

Question 44

The purpose of the detector in CT is to: (Reduce patient dose, Measure the amount of scattered radiation only, Measure the x-ray transmission through the patient, Make the beam more homogeneous)

Answer 44

Measure the x-ray transmission through the patient

Question 45

Which of the following is not a property of the detector? (beam quality, efficiency, response time, stability & reproducibility)

Answer 45

Beam Quality

Question 46

Which of the following CT detectors exhibits after-glow? (xenon gas, bismuth germanate, calcium fluoride, sodium iodide)

Answer 46

Sodium Iodide

Question 47

Which of the following is not true about scintillation (Solid State) detectors? (they have a low QDE [quantum detection efficiency], they have a high efficiency percentage, they have the potential for afterglow, they can be easily replaced.)

Answer 47

They have a low QDE (they are actually very efficient)

Question 48

What is an average amount of heat units produced for an average CT scan?

Answer 48

4 - 5 million HUs

Question 49

This "B" word is the most common shape of filter used in CT.

Answer 49

Bowtie

Question 50

The photodiode in the scintillation detector converts _____ into _____.

Answer 50

light into electronic signal