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2403 Physics > Chapter 11 Exam > Flashcards

Chapter 11 Exam Flashcards

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1
Q

What type of relationship does mAs have with the exposure reaching the image receptor?
a. Direct
b. Inverse
c. Direct proportional
d. Inverse proportional

A

c. Direct proportional

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2
Q

Which of the following describes the relationship between mA and time to maintain exposure to the image receptor
a. Direct
b. Inverse
c. Direct proportional
d. Indirect proportional

A

d. Indirect proportional

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3
Q

Increasing the mAs (within reason) has ______ effect on brightness displayed in digital imaging.
a. Direct
b. Proportional
c. Inverse
d. No

A

d. No

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4
Q
  1. Given the anatomic part is adequately penetrated, changing the kVp will affect:
    a. Brightness
    b. Compton scatter
    c. Subject contrast
    d. b and c
A

d. b and c

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5
Q

Which of the following factors do not affect spatial resolution?
a. Focal spot size
b. SID
c. OID
d. Grid

A

d. Grid

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6
Q

The amount of remnant radiation will decrease when increasing:
a. Focal spot size
b. Tissue thickness
c. mAs
d. kVp

A

b. Tissue thickness

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7
Q

A diagnostic image was produced using 70 kVp, 15 mAs at 40 inch SID. Which of the following exposure techniques would maintain the exposure to the image receptor when decreasing the SID to 30 inches?
a. 80 kVp at 15 mAs
b. 70 kVp at 8.4 mAs
c. 70 kVp at 11.3 mAs
d. 60 kVp at 27 mAs

A

b. 70 kVp at 8.4 mAs

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8
Q

What factor affects the amount of radiation intensity and scatter reaching the image receptor, magnification and spatial resolution?
a. OID
b. SID
c. Grid ratio
d. Bema restriction

A

a. OID

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9
Q

A diagnostic image is created using 80 kVp, 10 mAs, and a grid ratio of 12:1. Which of the following exposure techniques would maintain exposure to the image receptor when the grid is removed?
a. 68 kVp at 10 mAs
b. 80 kVp at 2 mAs
c. 92 kVp at 5 mAs
d. 80 kVp at 50 mAs

A

b. 80 kVp at 2 mAs

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10
Q

What is the magnification factor when using a 72 inch SID and 1.5 inch OID?
a. 0.979
b. 1.021
c. 1.5
d. 2.0

A

b. 1.021

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11
Q

How is the primary beam affected when increasing the tube filtration?
a. Increase in the number of x-ray photons
b. Increase in the proportion of lower-energy x-rays
c. Increase in the proportion of higher-energy x-rays
d. Increase in the speed of the x-ray photons

A

c. Increase in the proportion of higher-energy x-rays

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12
Q

A digital image of the T-spine was created using 75 kVp at 10 mAs, 12:1 grid, 40 inch SID, and small focal spot size. The exposure indicator value denotes insufficient exposure to the image receptor, and the image displays excessive noise. What adjustments to the exposure technique would improve the quality of the image if repeated?

A

10 mAs x 2 = 20 mAs

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13
Q

A good-quality AP hip was created in the radiology department using 80 kVp at 15 mAs, a 40 inch SID, and a 12:1 grid ratio. A request to image a similar-sized patient’s hip with the mobile x-ray unit requires the SID to be increased to 48 inches and the use of an 8:1 grid ratio. What adjustments in the exposure technique would provide a similar quality image?

A

80 kVp at 17.3 mAs, a 48 inch SID, and an 8:1 grid ratio

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14
Q

A good-quality KUB image was created on a patient measuring 10 cm using 70 kVp at 30 mAs, 40 inch SID, 12:1 grid, and large focal spot size. What adjustment in exposure technique would be done if the next patient requiring a KUB measured 15 cm?

A

30 mAs x 2 = 60 mAs

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15
Q

what are the primary technique factors?

A

milliamperage (mA), time of exposure (s), and kilovoltage peak (kVp)

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16
Q

Directly proportional to radiation quantity reaching the patient and the amount of remnant radiation reaching the IR

A

mAs (quantity)

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17
Q

As the mAs is increased the quantity of radiation reaching the IR is ______ proportionally.

A

increased

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18
Q

As the mAs is decreased, the amount of radiation reaching the IR is _______ proportionally

A

decreased

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19
Q

how to calculate mAs

A

milliamperage x seconds = mAs

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20
Q

What is the relationship between mA and exposure time

A

mA is inversely related to exposure time to maintain exposure to IR

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21
Q

What effects the brightness of a digital image?

A

Image brightness is adjusted during computer processing for low and high exposure errors

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22
Q

When adjusting mAs, what is the minimum adjustment that will make a difference?

A

Either doubling or halving the mAs

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23
Q

Exposure errors can result in:

A

increased quantum noise visible or increased patient exposure

24
Q

Alters the amount and penetrating ability of the x-ray beam and affects the amount of radiation exposure to the IR

A

kVp (quality)

25
Q

what is the 15% rule?

A

Changing the kVp by 15% has the same effect as doubling the mAs, or reducing the mass by 50%

26
Q

To maintain exposure to the IR when the kVp is adjusted by 15% the mass needs to be changed by a factor of __

A

2

27
Q

what do you multiple kVp by to increase by 15%?

A

1.15

28
Q

what do you multiple kVp by to decrease kVp by 15%?

A

0.85

29
Q

To maintain exposure:
(increasing kVp)

A

kVp x 1.15 = mAs / 2

30
Q

To maintain exposure:
(decreasing kVp)

A

kVp x 0.85 = mAs x 2

30
Q

a radiograph with a large number of densities but little differences among them

A

long scale contrast (low contrast)

31
Q

a radiograph with few densities but great differences among them

A

short scale contrast (high contrast)

32
Q

how does increasing kVp affect wavelength/frequency?

A

As kVp is increased the wavelength of the photon decreases and the frequency increases

33
Q

what affect does higher kVp have on subject contrast?

A

decrease in contrast

34
Q

what affect does lower kVp have on subject contrast?

A

increase in contrast

35
Q

what is the size of a small focal spot?

A

0.5 or 0.6mm

36
Q

what is the size of a large focal spot?

A

1 or 1.2mm

37
Q

What does the focal spot size effect?

A

Focal spot size affects sharpness but not IR exposure, determined by filament size

38
Q

how does the inverse square law effect beam intensity?

A

The intensity of the x-ray beam is inversely proportional to the square of the distance from the source

39
Q

what is the calculation for the inverse square law?

A

I1 (D2)^2
— = ———
I2 (D1)^2

40
Q

Direct square law (exposure maintenance formula) calculation

A

mAs1 (SID1)^2
——- = ————
mAs2 (SID2)^2

41
Q

affects the amount of radiation reaching the patient
- Inversely related to radiation intensity
- Changing this requires a change in mAs to maintain exposure to image receptor

A

SID

42
Q

refers to distance from the x-ray source (focal spot) to the object being imaged

A

SOD
Can be expressed as:
SOD = SID - OID

43
Q

affects radiation intensity reaching the image receptor, amount of scatter radiation reaching the image receptor, magnification, and spatial resolution
- Increasing this increases magnification and decreases spatial resolution
- Decreasing this decreases magnification and increases spatial resolution

A

OID

44
Q

indicates how much size distortion or magnification is demonstrated on a radiographic image

A

Magnification factor formula

45
Q

Magnification factor formula

A

MF = SID / SOD
Object size = image size / MF

46
Q
  • a device placed between the body part and the IR to absorb scatter radiation exiting the patient
  • limiting scatter improves radiograph quality and increases contrast
  • absorbs some radiation
A

grid

47
Q

what are the grid ratio to grid conversion factor numbers?

A

Grid Ratios (GCF)
No grid 1
5:1 2
6:1 3
8:1 4
12:1 5
16:1 6

48
Q

Grid factor formula for adjusting mAs

A

mAs1 grid ratio1
——– = ————–
mAs2 grid ratio2

49
Q

X-ray tubes operated above ____kVp are required to have a minimum of _____ of aluminum filtration

A

70 kVp, 2.5mm

50
Q

Increasing tube filtration _______ the percentage of higher penetrating x-rays to lower penetrating x-rays, which increases scatter

A

increases

51
Q

When imaging an anatomic area that varies greatly in tissue thickness, a _______________ can be placed in the primary beam to produce a more uniform exposure to the image receptor

A

compensating filter

52
Q

Use of a compensating filter requires an _______ in mAs to maintain the overall exposure to the image receptor

A

increase

53
Q

accounts for approximately 50% of the adult population and is commonly called a normal or average build

A

sthenic body habitus

54
Q

accounts for approximately 35% of adults and refers to a similar type of body habitus as sthenic, but with a tendency toward a more slender and taller build.

A

hyposthenic body habitus

55
Q

a large, stocky build and accounts for only 5% of adults

A

hypersthenic body habitus

56
Q

refers to a very slender body habitus and accounts for only 10% of adults

A

asthenic body habitus

2403 Physics (8 decks)

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