CT Instrumentation part 1 Flashcards
Were the first Gen CT scanners able to rotate all the way around a patient?
No. They used cables to power the tube in the gantry and had to be reset after exposure.
Which CT scanner generations were known as “translate-rotate”?
First Gen and Second Gen. The tube first “translated” across the patient and then the gantry “rotated” to the next position.
Which CT scanner generation had a “pencil beam”?
First Gen
Which scanner generation was limited to only scanning heads?
First Gen
Which ct scanner generation was the first to utilize a fan beam?
Second Generation
Which ct scanner generation used “rotate-rotate” technology?
Third Generation - both the tube and the detector array rotated around the patient
Which generation of CT scanners operated under the principle of “rotate-stationary”?
Fourth Generation
What kind of scanner does “EBCT” refer to?
Electron Beam CT
Does the Electron Beam CT scanner use an x-ray tube?
No, it does not. And all of it’s parts are stationary
What kind of studies does EBCT (electron beam CT) accel at?
cardiac imaging and anatomy and function scans
Which scanner generation has a focusing and deflection coil?
Fifth Generation (EBCT). The electrons get focused and deflected
Which ct scanner generation was known as EBCT?
Fifth Gen
The scanner that generates x-rays as a result of a high=speed electron beam bombarding stationary target rings is called a ______ scanner.
EBCT
Which of the following scanner generations first introduced the concept of whole body scanning (1st, 2nd, 3rd, 4th)?
Second Gen
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?
The Imaging System
Do ct scanners use three phase 12-pulse or high frequency generators?
The first scanners used three phase 12 pulse but modern scanners use High Frequency
What kVp range to CT x-ray tubes operate in?
120-140 kVp
What does the “RTM” in the RTM alloy anode of the ct x-ray tube stand for?
Rhenium Tungsten Molybdenum
Do CT x-ray tubes have a shorter or longer life than diagnostic x-ray tubes and why?
CT tubes have a shorter life because of the tremendous amount of heat that is produced
Do CT tubes have large and small focal spots like diagnostic tubes?
Why yes, they do.
what unit does the following formula produce: mA x Time x kVp x GF (Generator Factor)?
HU or Heat units
What is the formula to calculate Heat Units (HU)
mA x Time x kVp x Generator Factor (GF)
What is the main purpose of the Filters in the CT system?
They ‘shape’ the beam by harening it to make it more uniform and less polyenergetic
What material are filters usually made out of?
Copper and aluminum
In single slice acquisition what mechanical device defines slice thickness?
The pre-patient collimators
Does the pre-patient collimator help to reduce patient dose?
Yes, it does.
What determines the slice thickness in a multislice CT?
The detector aperture
What are three advantages of slip ring technology?
Faster Scan times, Less delay between scans, eliminates start-stop motion problems
The purpose of filtration in CT is to: (absorb “hard” radiation, increase beam quality, produce a more heterogeneous beam, or deflect photons)
Increase beam quality (make it more homogeneous)
Pre-patient commimators: (increase the energy of the beam, cause the beam to be heterogeneous, reduce patient dose, reduce scatter reaching the detector)
Reduce patient dose
Post-patient collimators (increase the energy of the beam, cause the beam to be heterogeneous, reduce patient dose, reduce scatter reaching the detector)
Reduce scatter reaching the detector
Which of the following affects slice thickness in single slice CT? (beam filters, beam collimators, x-ray tube, generator)
Beam collimators
Development of ______ allowed CT scanners to operate using a 360 degree rotation of the x-ray tube (crystal detectors, beam collimators, fiberoptics, slip rings)
Slip rings
Efficiency, Response Time, Dynamic Range, and Stability & Reproducibility are all characteristics of this “D” word.
Detectors
The ratio of the largest to smallest signal that can be detected in the detector array is know as the _____ range.
Dynamic
What are the two main types of CT detectors?
Xenon & Solid State
What is the other “S” name for Solid State Detectors?
Scintillation
What is the other name for Xenon detectors
Gas Ionization Detectors
High detection efficiency and remembering the amount of radiation sensed are two advantages of what type of detector?
Scintillation or Solid State detectors
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.
Scintillation or Solid State Detectors
Simple, compact, costs less, no afterglow are all advantages of this kind of detector.
Gas Ionization or Xenon Detectors
What is the primary disadvantage of Gas Ionization (xenon) detectors?
They are less efficient than their Solid State (scintillation) detectors
What type of detectors are used with 4th Gen CT scanners?
Solid State or Scintillation Detectors
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)
Measure the x-ray transmission through the patient
Which of the following is not a property of the detector? (beam quality, efficiency, response time, stability & reproducibility)
Beam Quality
Which of the following CT detectors exhibits after-glow? (xenon gas, bismuth germanate, calcium fluoride, sodium iodide)
Sodium Iodide
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.)
They have a low QDE (they are actually very efficient)
What is an average amount of heat units produced for an average CT scan?
4 - 5 million HUs
This “B” word is the most common shape of filter used in CT.
Bowtie
The photodiode in the scintillation detector converts _____ into _____.
light into electronic signal
