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312 Final Review
| Question | Answer |
|---|---|
| If a satisfactory density is obtained with 20mAs at 40 inches, what mAs is required to maintain the same density at 72 inches? | 65 mAs |
| Calculate the magnification factor when the SID is 72 inches and the OID is 2 inches | 1.6 M=SID/SOD |
| T/F When kilovoltage is increased with no other changes in technical factors, fewer scattered photons will result | False |
| T/F Scattered photons from Compton interactions are of no use in demonstrating radiographic structures of interest | True |
| T/F Shape distortion can be the result of a patient's body habitus | True |
| A filament may break due to: | vaporization |
| ______ is the metal of choice for the source of x-ray photons because of its high atomic number | Tungsten |
| Cracking of the anode typically occurs when: | a cold anode is hit with a high exposure |
| What is the area of the focal spot that is projected out of the tube toward the object being radiographed? | effective focal spot |
| What is the physical area of a rotating anode focal track that is affected by the cathode electron beam? | actual focal spot |
| What is the actual focal spot controlled by? | length of the filament |
| The protective housing of the x-ray tube controls leakage and scatter radiation through: | absorption |
| Beam filtration does what to patient dose? | decreases patient dose |
| During the process of attenuation, the x-ray photons may interact with: a. the nucleus b. the entire atom c. an orbital electron d. all of the above | D |
| When an x-ray photon passes through matter, it undergoes a process called: | attenuation |
| When filtration is _____, technical factors must be ____ to maintain the same density | increased; increased |
| Beam filtration affects patient dose by: | removing low energy photons |
| In diagnostic radiography, radiographic image contrast is principally due to the predominance of: | photoelectric interactions |
| A radiographer can best reduce the amount of scatter radiation from reaching the receptor by: | beam restriction (collimation) and using a grid |
| As more photons pass through the irradiated material unaffected, the resulting image receptor exposure has: a. greater image distortion b. less image distortion c. greater radiographic image density d. less radiographic image density | C |
| The effect of mAs upon IR exposure is: | directly proportional |
| A change in kVp, as an exposure factor, affects: | average beam energy, beam intensity, and the amount of scatter produced |
| A radiograph with few shades of gray exhibits: a. low contrast b. high contrast c. medium contrast d. long scale contrast | high contrast |
| Size distortion in radiography can be _____ only | magnification |
| Filament materials are chosen primarily for their: | high melting points |
| What is one of the most important concepts to consider when determining whether or not to use a grid? | thickness (size) of soft-tissue part being radiographed |
| What is the number of lead strips counted per inch when scanning transversely across a grid? | Grid frequency |
| In general, the use of a grid is needed for body parts larger than what? | 10-13cm |
| An increase in scatter radiation has what effect on subject contrast? | decreases subject contrast |
| When exposure needs to be adjusted, the minimum change that should ever be made in radiographic technique is a ____ percent change in mAs or a _____ percent change in kVp | 35; 5 |
| In general, what exposure technique adjustment is required for post-reduction radiographs with a full plaster cast? | Double mAs or 12-15% increase in kVp |
| _____ is the term used to express the resolution of a diagnostic image | Line pairs per millimeter (lp/mm) |
| An increase in kilovoltage will serve to produce a ______ scale of contrast | longer |
| A decrease in kilovoltage will _____ patient dose | increase |
| T/F A smaller field size will produce a longer scale of contrast | False |
| The unit of current is known as _____ | ampere |
| T/F Scattering occurs when there is partial transfer of energy to matter | True |
| Grids with lead strips running in only one direction are called ____ grids | linear |
| Decreasing the field size from 14 x 17 to 8 x 10 with no other changes will affect scatter in what way? | decreases the amount of scatter radiation generated within the part |
| The relationship between the height of a grid's lead strips and the distance between them is referred to as grid: | ratio |
| Calculating 400 mA and 0.05 seconds will provide a result of ____ mAs | 20 mAs |
| The smaller the collimated field size, the ___ the subject contrast present | higher |
| The higher the kilovoltage the ______ the scale of contrast | longer |
| A 15% decrease in kilovoltage accompanied by a 50% increase in milliampere-seconds will result in a ______ scale of contrast | shorter |
| The Potter-Bucky moving grid was developed to eliminate: | visible grid lines |
| With all other factors unchanged, if grid ratio is increased, magnification of the image would: | not change at all |
| The production of scatter radiation is most dramatically affected by the: | amount of tissue exposed |
| As x-ray beam energy increases, the absolute amount of scattered radiation produced within the patient: | increases |
| Within the signal of the remnant radiation beam reaching the IR, scattered radiation can destroy what? | image contrast, gray scale, and visibility |
| With all other factors unchanged, if grid ratio is increased, penetration of the x-ray beam in regards to the patient would: a. increase directly b. decrease directly c. not change d. may be affected indirectly, but not directly | C |
| What is the mechanism that moves the grid back and forth in a linear movement during exposure? | reciprocating Potter-Bucky mechanism |
| The use of a grid will ____ subject contrast and _____ patient dose | improve; increase |
| Battery powered constant potential mobile x-ray machines require about ___ kvP less when compared to 3-phase stationary untis | 8 |
| _____ is a means in which the degree of penetration of an x-ray beam is measured | half value layer (HVL) |
| T/F The main purpose of filtration is to protect the patient's body from excess radiaiton | True |
| On most digital systems, image brightness can be increased by: | holding the mouse button down and moving the cursor to the right |
| Mottle is likely to appear in the computerized image any time the exposure indicator is ____ | low |
| Mottle in a CR or DR image can result from: a. insufficient kVp b. insufficient mAs c. improperly calibrated AEC d. all of the above | D |
| For a quality digital image, the highest possible ___ should be achieved a. brightness b. contrast c. gray scale d. signal to noise ratio | D |
| What is displayed after every exposure to indicate how far off the radiographic technique was from an ideal exposure level? | Deviation index |
| Spatial frequency is measured in: | LP/mm |
| Changing from a 5:1 grid ratio to a 16:1 grid ratio will have an affect on: a. image detail b. image contrast c. maximum wavelength striking the patient d. all of the above | B |
| Which of the following has no impact on receptor exposure a. mA b. SID c. kVp d. focal spot size | D |
| Which of the following has no impact in spatial resolution a. SID b. OID c. kVp d. focal spot size | C |
| The air gap technique can be used as an alternative to: | grids |
| Which of the following has a direct impact on size distortion on a radiograph? | OID |
| To effectively take advantage of the anode heel effect, where should the thicker part of the anatomy by placed? | over the cathode |
| A particular radiographic grid contains lead strips that are 0.5mm high, 0.025 inches thick, and 0.05mm apart. What is the ratio for this grid? | 5:1 |
| This is a term that applies to the numeric value that is representative of the exposure the image received | Log mean |
| The mAs multiplication factor for a 12:1 grid is: | 5 |
| Which of the following does not have to be set when using an automatic exposure control system? a. mA b. receptor exposure setting c. back up time d. kVp | A |
| What combinations are needed in digital radiography systems to produce an image? a. intensifying screen and TFT b. Scintillator and CCD c. storage phosphor plate and CCD | B |
| The input phosphor of an image intensification tube is typically comprised of: | cesium iodide |
| What x-ray conversion process occurs when utilizing flat-panel detectors that use indirect conversion technology? | x-rays are converted into visible light |
| A ______ directly converts x-ray energy into a digital electrical signal | photoconductor |
| In digital imaging window level is responsible for doing what? | altering receptor exposure/brightness |
| The requirements necessary for the production of x-rays includes : | a means of accelerating the electrons, a means to suddenly stop electrons, a focusing of electrons and a source of free electrons |
| The cumulative timer on a fluoroscopic unit is designed to interrupt the production of the fluoroscopic beam after a period of ___ minutes of fluoroscopy has elapsed | 5 |
| With increasing levels of beam filtration where will the greatest dose savings be realized? | in the initial layers of tissue struck by the beam |
| Which combination will result in the least amount of radiation dose to the patient? a. high kVp, high mAs b. high kVp, low mAs c. low kVp, low mAs d. low kVp, high mAs | B |
| If 75 kVp and 50 mAs are used for an exposure, which technique will decrease patient exposure by one-half? a. 85 kVp and 50 mAs b. 75 kVp and 25 mAs c. 65 kVp and 50 mAs | B |
| The glass envelope and cooling oil are examples of _____ filtration | inherent |
| The minimum amount of total filtration for radiographic units operating above 70 kVp is what? | 2.5mm Al equivalent |
| What is the primary purpose of beam filtration? | reduce patient skin dose |
| The exposure cord for a portable radiographic unit must be a minimum of _____ feet | 6 |
| X-radiation is produced as a result of hot, high-speed electrons bombarding the: | Tungsten Target |
| With the use of filtration, x-ray quality is said to _____ and x-ray quantity is said to ______ | increase;decrease |
| A reduction of x-ray intensity as it passes through matter defines: | attenuation |
| As the distance from source of radiation to the patient is doubled, the intensity of the exposure will: | decrease 4x's |
| What are the exposure/technical factors used to create an image? | milliamperage (mA), exposure time (s), kilovoltage (kV), and SID |
| List different patient variables that have a significant impact of factor selection/technique | tissue density, tissue thickness, pathology and ability to cooperate |
| The term visibility of detail refers to what? | how well the recorded detail can be seen |
| ______ describes how closely fine details may be associated and still be recognized as separate details before seeming to blend into each other | resolution |
| _____ refers to misrepresentation of the actual size or shape of structures imaged | distortion |
| How does focal spot size affect detail? | increased focal spot size increases blur and decreases detail |
| Unsharpness/blur is ______ related to focal spot size and OID, and ______ related to SID | directly; inversely |
| T/F The use of a small focal spot improves recorded detail but generates more heat at the anode | True |
| The effective or projected focal spot size is always ____ than the actual focal spot size according to the line focus principle | smaller |
| The anode heel effect is most pronounced when? | large IR's, short SID's and small anode angles |
| Radiographic image density and mAs are quantitative factors and are ______ related | directly |
| As SID increases what happens to exposure rate and image density? | exposure rate and image density decrease |
| With changes in SID, what is the formula called that is used to calculate the new exposure rate? | inverse square law |
| With changes in SID, what is the formula called that is used to calculate the new mAs? | density maintenance formula |
| Increased kV produces ______ high energy x-ray photons, that is, exposure rate increases | more |
| If a focused grid requirements are not met, what will the resulting image demonstrate? | loss of density as a consequence of grid cutoff (absorption of useful beam) |
| What things do focused grids require? | correct surface facing tube (not upside down), tube angle parallel to lead strips, SID within stated focusing distance/range. x-ray CR not off center laterally |
Created by:
lrkelley