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CT Sys. Op. & Compo.
Study Questions
| Question | Answer |
|---|---|
| What CT system component translates each command as it is entered into the system's machine language before passing it on to the scan controller? | host computer |
| What does the scan controller do? | responsible for the timing and operation of the table, gantry, and high-voltage generator |
| Which system components operating using analog waveform? | continuous waveform |
| What gantry component collects the attenuation information? | detectors |
| Where is the tiny electrical signal output from the detector elements sent? | to the amplifier |
| In what electrical form does the amplifier output its signal/information? | in analog form |
| Where does the analog signal go to after it leaves the amplifier component? | to the Sample-and-Hold component (S/H) |
| Where does the analog signal go to after it leaves the sample-and-hold component? | to be digitized by the ADC |
| Where is the data stored after it leaves the DAC? | in a raw data file |
| In which system component is data calculated into an image? | array processor |
| Where does the calculated image go after it leaves the array processor and what for? | to the host computer so that it may be maintained on a storage device and displayed on the console monitor |
| How many detectors were in the 1st generation CT systems? | one |
| What was it called when the tube/detector configuration in a 1st generation scanner scanned across the patient's body in a linear path before rotating and repeating? | it "translated" |
| In a 1st generation scanner, what did you call the series of measurements that was collected as the tube/detector assembly translated across the patient? | projection |
| How many different projections were needed in a 1st generation system in order to construct an image? | 180 (180 degree arc) |
| 2nd generation CT systems used an x-ray tube that produced an x-ray beam that had a shape similar to a/an: | opened paper fan (fan shape) |
| 2nd generation systems are referred to as having ____ geometry. | fan beam |
| 2nd generation CT systems contain a group of detectors referred to as an: | detector array |
| About how many detectors comprised the detector array in 2nd generation scanners? | about 30 |
| After a projection of data is obtained in a 2nd generation CT system, the tube/detector rotates typically _____ degrees or more covering an arc of _____ degrees around the patient. | 5; 180 |
| 3rd generation systems incorporate what type of beam geometry? | fan beam |
| What was the major difference in the configuration between 2nd and 3rd generation CT systems? | 3rd generation detector array is arranged in a curved arc rather than a straight line |
| What is the beam geometry of a 4th generation system? | fan beam |
| Describe the detector arrangement in a 4th generation CT system. | the detectors do not travel with the tube but instead form a complete circle around the gantry in a ring configuration, which nutates or angles during the scanning process. |
| Most continuous rotation scanners use ____ technology. | slip ring |
| What type of architecture do MDCT scanners have? | 3rd generation |
| What are the three things that are transferred by the slip ring? | 1.) electrical power 2.) scanning instructions 3.) detected signals |
| What is the fastest CT on the market? | EBCT |
| How long does one “rotation” take on an EBCT scanner? | 50 to 100 milliseconds |
| What do we call the comparison of two imaging modalities yielding co-registered images? | fusion imaging |
| What are the two most common modalities to fuse? | CT/PET |
| Where does the radioactive pharmaceutical used in PET accumulate after it is injected? | in tissues having areas of rapid growth and increased metabolism |
| What console component serves the purpose of providing feedback to the technologist and data entry? | monitor |
| What system component is the primary link between the technologist and the other components of the imaging system? | host computer |
| What component controls the storage devices such as hard disks and removable media? | host computer |
| The _____ is located toward the central aspect of the gantry, about the perimeter of the gantry aperture. | rotating frame assembly |
| The rotating frame assembly contains the ____, ____ and the ____. | tube; detector array; data acquisition system (DAS) |
| How much can a gantry tilt/angle? | approximately 30˚ from the vertical plane |
| Where is the CT x-ray tube mounted? | on the rotating frame assembly within the gantry |
| What is another name for Bremsstrahlung radiation? | breaking radiation |
| What percentage of the x-ray beam emitted from a CT x-ray tube is characteristic radiation? | 10% to 12% |
| What is the main source of the enormous amount of heat that builds up in a CT x-ray tube? | the generation of x-rays from the collision between the electrons and the anode target |
| What is the atomic number of tungsten? | 74 |
| What is the melting point of tungsten? | approximately 3400˚ C |
| What is located on the surface of the rotating anode? | tungsten |
| What is the minimum amount of time that must transpire between the end of one scan and the initiation of the next scan called? | inter-scan delay time |
| What do pre-patient collimators do in single-row detector scanners? | they restrict the x-ray beam to the thickness of the slice. |
| What do pre-patient collimators do in multi-row detector scanners? | they select the thickness of the x-ray beam, which spreads out over multiple detectors |
| What are the thick, metal pre-patient collimators attached to? | to the bottom of the tube housing |
| What are the two basic categories of detectors? | gas and solid state detectors |
| Most gas detectors used on CT systems contain a gas called ____. | xenon |
| What is a solid state detector made of? | a solid crystalline substance which is much more dense than Xenon |
| What is another name for solid state detectors? | scintillation Detectors |
| Which type of detector is the most sensitive to x-rays coming in from various angles? | solid state detectors |
| Which type of detector generates a flash of light in response to an incoming x-ray photon? | solid state |
| When a solid state detector generates a flash of light, it is sensed by the ____. | photodiode |
| On single row detector scanners, what determines the final slice thickness? | collimation |
| Where is the primary place for all complex mathematical calculations involved in generating CT images? | array processor |
Created by:
sspatel
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