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Chapter 6 & 7
Key Words
| Question | Answer |
|---|---|
| Anatomically programmed radiography | a programmable chart within the computer of the x-ray machine in which techniques for each body part and technique is programmed in to the machine |
| Automatic exposure control | an electronic circuit within the x-ray machine that automatically terminates the exposure when predetermined quantity of x-rays has been detected |
| Autotransformer | a single coil transformer that serves three functions, provides the means for kVp selection, provides for fluctuation in the incoming line, supplies power to the other parts of the x-ray circuit |
| Back-up timer | a timer that backs up the AEC, to ensure that the patient does not get overexposed |
| Diode | an electronic device that permits current to flow in one direction only; prevents back flow. When one used is placed between the anode and the transformer and when two is used the second is placed between the cathode and anode |
| Electric ground | a wire is connected to the mA meter that absorbs or drain off excess electric charges |
| Electronic timer | capable of ultrashort exposure times and are designed for 3 phase and high frequency ge nerators |
| Exposure switch | completes the circuit so that x-rays are made |
| Exposure time | the time in which x-rays are being made |
| Full wave rectification | utilizes the entire electric cycle, the use of 4 diodes in a circuit and redirecting the current during the negative half of the electric cycle so that current will flow in the same direction during both halves of the cycle |
| Heat unit (HU) | the measurement of heating in the x-ray tube, all tubes have a maximum heat limit |
| High frequency x-ray generator | a unit that employ special inverter circuit that convert rectified AC into a series of square pulse that results in even less exposure time and lower patient dose |
| Ionization chamber | a chamber enclosed volume of dry air connected into the circuit, the air is ionized by remnant radiation, a minute amount of current flows through the circuit when a specific quantity of current has been measured the exposure is terminated |
| Phototimer | a fluorescent screen under the Bucky tray that gives off light when exposed to radiation that has passed through the patient and IR that terminates the exposure after a specific amount of light has been detected |
| Rectifier | a unit that makes the current flow in one direction |
| Rheostat (mA selector) | varies the resistance in a circuit |
| Rotor/prep/ready/standby switch | the button in which starts the rotor to heat the filament in preparation for exposure |
| Self – rectification | primitive and inefficient form of rectification in which the x-ray tube itself controls the direction of current flow |
| Single phase current | a current in which is only using one phase of the alternating current results in a pulsating x-ray beam |
| Synchronous timer | controlled by a small electric motor rotating at 60 revolutions/sec time settings will be stated as fractions and multiples of 1/60 second the duration of an electric impulse |
| Three phase current | alternating current is generated in 3 overlapping cycles that produce a more constant & efficient voltage and when rectified is in a waveform that has the appearance of a ripple with no real low points |
| Tube rating chart | a graph that is made by the company that is used to determine if the mA and time chosen will be a safe exposure |
| Line meter | a voltmeter wired to measure the incoming voltage |
| Rectification – | to make right; the process of changing alternating current into direct current so the current flows only in one direction |
| Contrast | the difference in radiographic density between any two adjacent portions of the image |
| Density (radiographic) | the overall blackness or darkness of the radiograph |
| Distortion | difference between the actual subject and its radiographic image |
| Elongation | projects the object so it appears longer than it really is |
| Foreshortening | projects the part so it appears shorter than it really is |
| Involuntary motion | movements of the body in which the patients has no control over such as tremors, peristalsis and heart beat |
| Magnification | result of the geometry of the image set up |
| Object-image distance | the relationship between the distance of the subject and the IR |
| Over exposed | a film that is too dark |
| Penetrometer (step-wedge) | a solid piece of aluminum with steps of varying thickness |
| Fog | unwanted exposure to the film |
| Penumbra | the unsharp edges of an image; the blur; geometric unsharpness |
| Quantum mottle | a grainy or mottled (spotty) appearance of the image usually caused by the use of an insufficient radiation exposure for the boy part or for the requirement of the image receptor. Not desirable in creating x-ray |
| Radiographic contrast | the overall contrast seen in the radiographic image |
| Recorded detail | the sharpness of the structures in the image the terms detail, sharpness and resolution are sometimes used to refer to recorded detail |
| Shape distortion | result in unequal magnification of the actual shape of the structure |
| Short scale contrast | range of densities are few (short) (shades of gray are few) |
| Size distortion | form of magnification |
| Source-image distance | the distance between the x-ray tube and the IR |
| Subject contrast | the range of differences in the intensity of the x-ray beam after it exits the patient |
| Tissue density | the mass density of the body part |
| Umbra | the actual anatomic area, body part or structure |
| Underexposed | a film that is too light |
| Voluntary motion | motion that is normally controllable |
| Long scale contrast | has many densities (shade of gray) |
| Inverse square Law | the relationship between SID & beam intensity; A law that states the x-ray intensity is inversely proportional to the square of the distance from the source I1/I2 = SID22/ SID12 |
| Control console | the part of the x-ray equipment where the factors are set to take a radiograph and is behind a lead barrier |
| Filament circuit | the subcircuit of the circuit that supplies and controls the heat required by the x-ray tube filament for thermionic emissionbefore processing; used to measure contrast |
| Low voltage circuit | the circuit between the alternating current (AC) power supply and the primary (input) side of the high voltage (step-up) transformer |
| High voltage circuit | subcircuit of the x-ray circuit that begins and ends with the secondary side of the step up transformer, it increases the voltage to make x-rays |
| Line voltage compensator | a device that ensures that the outgoing voltage is accurate regardless of fluctuations in the incoming line |
| kVp meter | device that measures the voltage output from the autotransformer |
| Milliammeter | device that is connected midpoint of the secondary side of the step-up transformer that measures the current flowing in the high-voltage circuit during exposure |
| Alternating current | the polarity of the power source reverses at regular intervals |
| Direct current | current that flows only in one direction |
| Falling load generator | x-ray units that begin at the highest mA compatible with the desired filament and focal spot selection. mA decreases during exposure if necessary to avoid over heating |
| Film screen contact | uniform tight contact with two intensifying screens with the film between them |
Created by:
mdtodd
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