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Diagnostic Imaging
Quiz Review #2
| Question | Answer |
|---|---|
| Define Developer solution | Converts the sensitized silver halide crystals into black metallic silver |
| Which solution is alkaline? | The developer solution |
| Define Fixer solution | Removes the unchanged silver halide crystals while hardening the emulsion |
| Which solution is acidic? | The fixer solution |
| Define Collimator | The glass window with 2 pairs of lead shutters that adjust the size of the primary beam to the size of the image recepter |
| What are three advantages of utilizing the collimator? | Increases image quality, reduces scatter radiation, reduces exposure for both the patient and staff |
| What is the air gap technique? | It is the method for limiting the scatter reaching the image receptor. Scatter radiation exiting the patient will miss the image receptor if there is an increased distance between the patient and the image receptor (increased OID). |
| Define intensifying screens | A device found in radiographic cassettes that consists of an emulsion spread on a polyester base containing phosphors that convert x-ray energy into light which then exposes the radiographic film. |
| Define Radiographic detail | The level of clarity between the edges of one tissue or structure and the edges of an adjacent tissue or structure |
| Define Rare Earth screen | A type of intensifying screen containing rare earth phosphors |
| Rare earth phosphors are more commonly found in which type of intensifying screen? | more commonly found in screens intended for green light sensitive films than those meant for the blue light sensitive films |
| Define rigid cassette | A rectangular or square film cassette made of plastic or metal used in radiography |
| Define Safelight | A light source suitable for use in photographic darkrooms. Allows enough light to work without damaging the film. |
| What color are safelights used for Blue light sensitive film? | Amber |
| What color are safelights used for Green light sensitive film? | Dark Red |
| What color of safelight can be used for both Blue and Green light sensitive film? | Dark Red |
| Define scale of contrast | A scale that shows the variance between black and white on a radiograph. |
| What is the difference between a short scale of contrast and a long scale of contrast? | Short = few shades of grey, long = many shades of gray |
| Define Grid | A device that has very thin lead strips with radiolucent interspaces located between the table top and the image receptor |
| Define foreshortening | Reduction in projected image size related to the angle of inclination of the object |
| Define latent image | The invisible image that exists on the exposed film before it has been chemically processed |
| Define Penumbra | Geometric unsharpness or focal spot blur. The blurry edges surrounding a radiographic object. |
| Define Film Fogging | Unwanted density on the radiographic image caused by extraneous heat, light or chemical fumes |
| What is a grid used for? | To absorb scatter radiation |
| What are the main components of the Cathode Assembly? | Filament or filaments, focusing cup |
| What are the main components of the Anode Assembly? | Anode disk, Induction motor, Rotor |
| What are the main components of the x-ray tube? | Cathode, Anode, and Glass Envelope |
| Define Rectification | Process of converting alternating current to direct current |
| What is required to ensure electron flow in one direction: from cathode to anode? | Voltage rectification |
| You have to increase the kVp by how much to double the density of the radiograph? | 20% |
| You have to increase the mAs by how much to double the density of the radiograph? | double the mAs |
| You have to decrease the kVp by how much to halve the density of the radiograph? | 16% |
| You have to decrease the kVp by how much to halve the density of the radiograph? | halve |
| What is the mathematical formula for mAs? | mA x seconds = mAs |
| What is the mathematical formula to find the number of mA from mAs? | mAs / seconds = mA |
| If the background is black, but the structures are muddled & grey you increase which mAs or kVp? | kVp |
| If the background is grey and the structures are grey muddled you increase which mAs or kVp? | mAs |
| How do you know which to increase the kVp or the mAs? | You look at the background, if it's black you are producing enough x-rays |
| Density increases with increased kVp due to what? | Increased x-ray energy, increased penetration, increased scatter radiation. More photons are able to reach the film so the density is increased. |
| If the anatomic density is low the x-ray density will be what? | higher |
| What is subject density? | It is the ability for different tissue densities to absorb x-rays due to their anatomic number and thickness |
| 4-5% change in kVp creates what kind of difference in the radiograph? | barely noticeable |
| The ease with which the details can be perceived on a radiograph is known as what? | Radiographic Quality |
| What factors influence quality? | Equipment, Radiographic density, Contrast, Detail, quantum Mottle, Distortion, Scatter, Grids, Artifacts, Proper processing, proper labeling |
| What is Thermionic emission? | The boiling off of electrons from the filament (cathode). As filament current increases, the filament becomes hotter and more electrons are released |
| Which side of the x-ray tube is high voltage? | Anode |
| Which side of the x-ray tube is low voltage? | Cathode |
| What is milliamperage? | a measurement of the number of electrons traveling from cathode to anode during the exposure. |
| Milliamperage is also known as what? | Tube Current |
| In radiology time measures what? | How long the x-rays are produced - length of exposure |
| Time is directly proportional to what? | The number of electrons crossing the tube and is therefore directly proportional to the number of x-rays created |
| True or False: Most machines have mA and seconds separate? | False |
| What factors affect Radiographic/Optical Density (OD)? | mAs, kVp, Focal Film Distance, SID, Intensifying Screens, Grids, Structural Considerations, Generator type, beam restriction, anode heel effect, processing |
| Density is defined as what? | Sufficient accumulation of black metallic silver on a radiographic image, the overall blackening of the film |
| Density is created by how? | Number of x-rays generated, sent through the patient, and then to the intensifying screen where it exposes the film emulsion |
| What is the primary controller of density? | mAs |
| Excessive mAs will result in what type of film? | an overly dense, dark film |
| Inadequate mAs will result in what type of film? | a light film |
| Patient dose is affected by the mAs how? | When mAs increase, patient dose increases and when mAs decrease patient dose decreases |
| What is Quantum Mottle? | It is a density variation caused by incomplete exposure of film. |
| Quantum mottle is more often seen in what type of film? Why? | rare earth films, they use lower mAs |
| How does an increase in quantum mottle affect detail? | It decreases it. |
| Why does an increase in mAs increase patient dose? | mAs is directly proportional to the number of electrons crossing the tube as this increases the number of x-rays created increases, and the more x-rays the more radiation is given off/higher the dose |
| What is the 30% Safety Rule? | A 30% change in mAs is needed to produce a barely noticeable difference in density so as a general rule it should be increased by at least 50% and if 50% is not required then another exposure is NOT necessary |
| Kilovoltage controls what? | Penetrability |
| How does the thickness of the anatomical part affect the kVp? | The thicker the anatomical part the higher the kVp |
| True or False: Penetration depends on kVp and object density? | True |
| How does increasing kVp affect the electrons? | It accelerates them, increasing their kinetic energy and acceleration |
| How does increasing kVp affect scatter radiation? | It increases it |
| How does kVp affect heat and x-rays? | Higher kVp allows you to use less mAs which decreases tube load which decreases tube heat |
| How does kVp affect contrast? | Contrast decreases with increased kVp due to increased x-ray energy, increased penetration, and increased scatter radiation |
| What type of contrast does low kVp have? | high contrast |
| What type of contrast does high kVp have? | low contrast |
| High contrast has what type of exposure latitude? Why | narrow, because at a lower kVp a difference of a few kVp will make a very noticeable difference (error on the lower side) |
| Low contrast has what type of exposure latitude? Why? | wide, because at higher kVp a difference of a few kVp will make little if any difference radiographically |
| If you have a kVp of 50 and the machine will only go to 49 or 51 which should you use and why? | 49 because you always error on the lower side |
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