| Term | Definition |
| heat units (HU) | used by the anode cooling chart to tell the time needed for the anode to cool completely in order to continue making exposures |
| HU formula | kVp (anode speed) x mA x s (technique) x rectification constant (generator factor) |
| generator factor to caculate HU | single phase: 1
three phase 6 pulse: 1.35
3 phase 12/14 pulse: 1.41
high frequency: 1.41 |
| total pixels in a matrix formula | rows x columns |
| pixel size formula | FOV/matrix |
| bit depth determines: | contrast resolution |
| bit depth formula (number of shades) | 2n^2 |
| magnification factor (MF) | Full-size input phosphor diameter / Selected input phosphor diameter |
| What circumstances are most likely to lead to an increase in grid cutoff when using a parallel grid
Inc in the exposure time
Improper positioning of the grid
Large SID
Use of sm digital display devices
Use of large-area image receptors | improper positioning of the grid, use of large image receptors |
| How much voltage ripple is produced by three-phase, twelve-pulse power
100.0%
4.0%
0.9%
14.0% | 4.0 % |
| Select the factors that influence the amount of beam attenuation.
tissue density
tissue thickness
x-ray beam quality
atomic number
x-ray beam quantity | tissue density, tissue thickness, xray beam quality, atomic number |
| If the source to image distance is 150 cm, how much variance between the light field and the x-ray beam is acceptable
6 cm from the IR
15 cm from the IR
3 cm from the IR | 3cm, 2% variance |
| A radiograph is made using 40 milliampere seconds (mAs) at a 40-inch SID. If the image must be repeated at a 72-inch SID, what mAs value is necessary to maintain the same exposure
Incorrect answer:
120 mAs
Correct Answer:
130 mAs
12 mAs | |
| What factors influence receptor exposure
Correct answer:
SID
Incorrect answer:
kVp
Missed Option - Incorrect
Correct answer:
Grid Ratio
Correct answer:
mAs | |
| From the following, select the factor(s) that mAs affect in digital imaging
Correct answer:
patient dose
Incorrect answer:
contrast
Selected Answer - Incorrect
Incorrect answer:
spatial resolution
Selected Answer - Incorrect
Correct | |
| What are the functions of the anode
Incorrect answer:
Reducing off-focus radiation
Selected Answer - Incorrect
Answer,
Reducing the intensity of leakage radiation
Answer,
Protecting the x-ray tube from damage
Incorrect answer:
Pro | |
| Which factors influence image contrast
Incorrect answer:
IR
Missed Option - Incorrect
Correct answer:
OID
Answer,
SID
Incorrect answer:
Alignment of the anatomical part
Selected Answer - Incorrect
Answer,
FSS | |
| The feature of the image intensifier that automatically adjusts kVp and mAs during fluoroscopy is the:
automatic gain control.
, Not Selected
photocathode.
, Not Selected
electron-focusing lens.
, Not Selected
Incorrect answer:
aut | |
| If a 30/23/15 cm image intensifier is operated in the 23-cm mode, the fluoroscopic image will be magnified by a factor of
1.5
, Not Selected
Incorrect answer:
1.3
Correct Answer:
2
1.7
, Not Selected
2 | |
| hen using automatic exposure control (AEC), the radiologic technologist can still select or change which factors
Correct answer:
Optical Density
Correct answer:
kVp
Correct answer:
Backup time
Incorrect answer:
mA
Missed Option | |
| The measure of the imaging system’s ability to display the contrast of anatomic objects varying in size is the:
Incorrect answer:
spatial frequency.
Correct Answer:
modulation transfer function.
modulation transfer function.
, Not Select | |
| If the source to image distance is 150 cm, how much variance between the light field and the x-ray beam is acceptable
Higher; larger
, Not Selected
Incorrect answer:
Lower; smaller
Correct Answer:
Higher; smaller
Higher; smaller
, | |
| Photoelectric interactions result in the production of
Incorrect answer:
Secondary photon
Missed Option - Incorrect
Correct answer:
Photoelectron
Answer,
Compton electron
Correct answer:
Characteristic radiation | |
| voltage ripple | Voltage ripple is the variation in the output voltage waveform of an X-ray generator. It's expressed as a percentage, calculated as (Vmax - Vmin) / Vmax * 100%, where Vmax is the maximum voltage and Vmin is the minimum voltage during a cycle |
| how voltage ripple affects xrays | affects the energy and intensity of the X-ray beam. Lower voltage values during the cycle produce lower energy X-rays, some of which may be absorbed by the patient or have little diagnostic value |
| Single-phase: | These generators have the highest ripple (100%), as their output voltage fluctuates between the peak voltage and zero |
| Three-phase | Three-phase generators (6-pulse and 12-pulse) have lower ripple (around 13% and 4%, respectively) due to their smoother waveform |
| High-frequency generators | These generators use inverters to produce a nearly constant DC waveform, minimizing ripple to less than 1% |
| half/full wave(rectified) ripple | 100% ripple |
| three phase six pulse ripple | 14% |
| three phase twelve pulse | 4% |
| high frequency | <1% |
| When performing a quality control test to ensure that the penetrating ability of the x-ray beam is accurate, the result must be within this amount of the control panel setting:
5%
4%
2%
10% | 5% |
| exposure indicator | The numerical value that is displayed on the processed image to indicate the level of x-ray exposure received on the digital image receptor |
| sampling frequency. | How often the analog signal is digitized |
| A grid has lead strips 3 mm high and 0.5 mm apart. What is the grid ratio | 6:1 |
