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Imaging Ch.6
The X-Ray Imaging System
| Question | Answer |
|---|---|
| 90-90 tilting table | Can tilt from the horizontal position to a complete vertical position in either direction. |
| 90-30 tilting table | Can tilt the horizontal position to a complete vertical position in one direction & to a 30 degree tilt in the other direction. |
| Free floating | Has a locking mechanism that when it is turned off, allows the radiographer to move the table top manually. |
| Motorized | Has a switch that drive the table top in the desired direction. |
| Stationary | The table top does not move, the radiographer must move the patient. |
| Adjustable | The height of the table can be adjusted to a comfortable level for the patient & technologist. |
| NON-ADJUSTABLE Non- adjustable | The height may not be adjusted. |
| Mobile patient exam tables | Which is portable & may be used for various types of procedures & with various types equipment. |
| Radiogorphic only | Will be utilized to produce only over head films. |
| Radiogorphic & fluoroscopic(R/F OR R & F) | Will be utilized to produce over head films & fluoroscopic images. |
| Bucky slot cover | During fluoro the Bucky must be covered so that radiation may not be scattered from the X-ray tube towed radiographer or radiologist. |
| Ma control | - Controls the number of electrons crossing from cathode to anode per second & is measured in milliamperes (ma). - X-ray tube current is controlled through a separate circuit called the filament circuit. |
| Operating console | -ma control: Controls quantity or the number of x-rays & is expressed in mAs. -kVp control: Controls quality or the penetrability of the x-ray beam & is expressed in kVp. -LLine compensation. -Autotransformer. - Exposure timers. |
| Filment | Coil of wire that when a current is supplied will heat up & actually allow electrons to be emitted from the coil. |
| Filament Circuit | - Operates at b/w 3 & 6 A ( amperage from the autotransformer is stepped down so that the appropriate ma can be selected). |
| kVp control | kVp determines the quality or the penetrability if the x-ray beam. |
| Major kVp | Selects the kVp by factor of 10. |
| Minor kVp | Selects the kVp by factors of 1. |
| Combination | A______ of major & minor kVp gives the appropriate kVp readout for an exposure. |
| Line compensator | Compensates the incoming voltage so that a constant voltage may be used during exposure & not a crying voltage. |
| Autotransformer | Designed to supply the precise voltage to the filament circuit & to the high voltage circuit of the x-ray imaging system. |
| Synchronous timers | - Driven by a synchronous motor which operates at 60 revolutions per second. - Recognizable b/c exposure time are in intervals 60 exposure (1/60S, 1/20 S, 1/30 S). - Have to be reset after each exposure. |
| Electronic timers | -The most expensive, most complicated & most accurate of the x-ray timers. -Composed of complex circuitry. - Allow for a wide range of intervals. - Can be used to make serial exposures. |
| mAs timers | -An electronic timer. -The technologist selects the mAs & when the desired mAs is reached the exposure is terminated. |
| Automatic exposure control timers | The exposure will automatically terminate the exposure when sufficient radiation to provide the required optical density has reached the image receptor. |
| Automatic exposure control timers | - Aec measure the quantity of radiation reaching the image receptor. - Controlled by kVp setting. - Operates best at high kVp levels. |
| High voltage generator | Converts the low voltage supplied from the power company into high kilovoltage required to produce x-ray & the high amperage to the milliamperage need to produce current to the filament. |
| The filament transformer | A step-down transformer. |
| High voltage transformer | A step-up transformer. |
| Rectifiers | Converts AC to DC. |
| Rectificaton | Is required to ensure electron flow in only one direction in the X-ray tube, from cathode to anode. |
| Solid-state rectifiers | -Also called a solid state diode. -Composed of two types of semi-conductors. |
| P-types | Have electron traps mode up of positively charged holes the tend to attract & hold elections. |
| N-types | Have loosely bound electrons that are relatively free to move about inside the material. |
| Unrectified voltage | Voltage at the primary & secondary side of the high voltage step-up transformer. |
| Waveform | Is a sinusoidal wave. |
| __________________ takes place between the secondary side of the step up transformer & the X-ray tube. | Rectification. |
| Half-wave rectification | -The inverse (negative) voltage is removed from the wave making all voltage positive. - Only half of the AC waveform appears in the output . |
| Full-Wave rectification | - Converts the negative half of the AC wave form into positive wave form that can be used in x-ray production. -Must have 4 rectifiers to accomplish full wave rectification. |
| Single-Phase power | - Allows the incoming power to pulsate due to the rise and fall of current. -Full voltage ripple: 100%. |
| Three- phase power | -3 Wave forms are provided, so that the resulting waveform maintains a nearly constant high voltage. -4% Voltage ripple. |
| Three phase six pulse | Characterized by 6 pulses every 1/60sec. |
| Three phase 12 pulse | Characterized by 12 pulses every 1/60sec. |
| Capacitor discharge generator | -This is a battery type usually portable unit. -Discharge pre-selected amount of energy from a rechargeable battery unit. |
| High frequency generator | -Instead of using 60 pulses per second for incoming voltage, it used 500 pulses per second. - The most efficient of all x-ray generators. -1% Voltage ripple. |
| Falling load generator | Used primarily in high-capacity & interventional radiography system. |
| Half wave= | 100%. |
| Full wave= | 100%. |
| Three phase six pules= | 14%. |
| Three phase twelve pules= | 4%. |
| High frequency= | <1 %. |
| Transformers & high-voltage generators are identified by their__________. | Power rating. |
| Power | P = A X V. |
| Carbon fiber couches | Contribute to reduced patient radiation dose. |
| Radiation quantity | Is x-ray intensity. |
| Radiation quality | Is x-ray penetrability. |
| With _________ and ________ x-ray imaging systems, the three components are housed vert compactly. | Dental; mobile |
| kVp | Determines the quality of the x-ray beam. |
| Thermionic emission | Is the release of electrons from a heated filament. |
| The ___________________ has a single winding and is designed to supply a precise voltage to the filament circuit and to the high-voltage circuit of the x-ray imaging system. | Autotransformer. |
| The product of the x-ray tube current (mA) and exposure time (s) is __________, which is also electrostatic charge (C). | mAs. |
| Most exposure times are _____________ and are controlled by a microprocessor. | Electronic. |
| mAs timers | Are used on flailing-load and capacitor discharge imaging systems. |
| The ______________ contains three primary parts: the high voltage transformer, the filament transformer, and rectifiers. | Hgh-voltage generator. |
| Radiographers outside the United States may use a frequency of _____________. | 50 Hz. |
| Voltage rectification | Is required to ensure that electrons flow from x-ray tube cathode to anode only. |
| Rectifiers | Are located in the high-voltage section. |
| The main advantage of full wave rectification: | The exposure time for any given technique is cut in half. |
| The voltage applied to the x-ray tube is nearly constant when using the _______________________. | Three-phase power. |
| During ________________ the voltage fails approximately 1 kV/mAs. | Capacitor discharge. |
| Full-wave rectification or high voltage generation | Is used in almost all stationary x-ray imaging systems. |
| _________ voltage ripple results in ___________ radiation quantity and quality. | Less; greater. |
| High-voltage generator power (kW) = | Maximum x-ray tube current (mA) at 100 kVp and 100 ms. |
| Autotransformer Law | Vs = Ns. Vp = Np. |
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sassyrad
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