RADR 1213 exam 5 principles of radiographic imaging ROD

The principal controlling factor of radiographic receptor exposure is

mAs

The recorded detail of a digital RADIOGRAPHIC image is primarily visible because of ?

A. Sufficient contrast

B. Sufficient receptor exposure

C. Both a & b

C both a & B

The principle controlling factors of radiographic contrast

A. Kvp

B. MAs

C.Focal spot size

D. Anode angel

Kvp

A radiograph that demonstrates considerable differences between densities is called

short scale

high contrast

increased contrast

(all of the above)

short scale, high contrast, increased contrast (all of the above)

The difference between two adjacent shades of gray shades on a RADIOGRAPHIC image ?

A. Recorded detail

B. Quantum mottle

C. Radiographic contrast

C. RADIOGRAPHIC contrast

A radiograph with few shades of gray exhibits

A. Low contrast

B.high contrast

C. Medium contrast

D. Long scale contrast

B.high contrast

Which type of radiography produces the most clinical information?

Low contrast images

Which factor influences the number of photons reaching the IR?

mAs

Because of the "heel effect," x-ray beam intensity

Is greater under the cathode side of the tube

If a radiograph using 30 mAs (400 mA at 0.075 sec.) produced a radiograph with satisfactory image quality, what new mA should be used at 0.20 sec.?

150 mA

A radiograph of the forearm is produced using 4 mA at 55 kVp. What kVp would be required to double the exposure?

63 kVp

If a satisfactory EI # is obtained with 40 mAs at 72 in, what mAs is required to maintain the same receptor exposure at 40 in?

12 mAs

If a satisfactory radiograph is obtained at 72 in with a patient exposure of 4 R, what will the exposure be if the distance is reduced to 40 in?

13 R

The difference between two adjacent gray shades on a radiographic image is

Radiographic contrast

A radiograph with few shades of gray exhibits

High contrast

In imaging using a DR dectector, image contrast decreases with

A. Excessive Kvp values

B. Underexposure

C. MAs values that are too low

D. RADIOGRAPHIC grids

A. Excessive Kvp values

Which of the choices below does not increase contrast?

A. Increasing grid ratio

B. Increasing the amount of irradiated tissue

C. Decreasing filtration

D. Decreasing Kvp

B. Increasing the amount of irradiated tissue

A fluoroscopic examination that uses barium as a contrast material would typically produce images with?

A.long scale

B. Short scale

C. Low contrast

D. A & C

D. A and C

Which type of radiograph provides the most clinical information?

Low-contrast images

The principal controlling factor for radiographic contrast using film-screen technology is

kVp

A radiograph that demonstrates considerable differences between gray shades is said to have

Short scale, high contrast, and increased contrast

With digital imaging technologies, the final brightness and contrast appearance of an image is due to

Look-up table (LUT) application

A frontal projection best radiograph that demonstrates a faint outline of the thoracic spine and many shades of gray to show the pulmonary markings of the lungs illistrates

Long-scale contrast and adequate penetration

IR contrast of radiographic film is expressed as the ____________ of the D log E curve

Slope

Varying tissue thickness and densities is referred to as

Subject contrast

As kVp ______________, a _____________ range of photon energies is produced

Increases; wider

High contrast is directly related to

The number of photoelectric interactions

What increases contrast?

Increasing grid ratio, decreasing filtration, and decreasing kVp

Radiographic image contrast is a combination of

Receptor contrast and subject contrast

As kVp increases, the percentage of Compton interactions ____________ and contrast ___________

Increases; decreases

When the tissue structure of the ankle joint is considered, the dramatic tissue difference between the muscles and bones of the ankle produce

High subject contrast

The total amount of irradiated material is a function of

Body part thickness and area of exposure

In order to reduce patient entrance skin exposure (ESE), higher kVp exposures are a consideration. It is important to remember that

kVp values that are extremely high can negatively impact the data histogram

kVp controls the proportional relationship of

Compton and photoelectron interactions

When digital imaging receptors are used,

An exposure at 90 kVp would require a grid

What factors would affect radiographic subject contrast?

Part thickness, average tissue density, and using barium as a contrast agent

In digital imaging systems, increasing sampling frequency of the data?

A. Increases dose

B. Increases image fidelity

C. Decreases MTF

d. decreases dose

b. increases image fidelity

An increase in x-ray beam filtration,

Increases the number of Compton interactions, reduces contrast, and increases the average photon energy

Because the x-ray beam is divergent,

minification is impossible

With digital imaging systems, the primary factors affecting final image contrast are the

Histogram and look-up table (LUT)

Spatial resolution is

The degree of geometric sharpness, definition, and the accuracy of the structural lines actually recorded in the radiographic image

The traditional unit of resolution measurement typically used in film/screen imaging is

Line pairs per millimeter

Poor spatial resolution is caused by unacceptable levels of

Penumbra

What can negatively impact recorded detail?

Involuntary motion

Factors affecting recorded detail include

Focal spot size and patient thickness

Spatial resolution is improved when

OID decreases

Spatial resolution in digital imaging is determined by the

Bit depth, matrix size, and the pixel size

What radiographic positioning and SID exhibits the best recorded detail?

A PA chest radiograph for evaluation of the heart at 72 in

Penumbra decreases as

Focal spot decreases, OID decreases, and SID increases

The best method for controlling motion when the patient is unable to cooperate is to

Maintain mAs, while decreasing time

The _____________ represents a depth to the information in the digital image

z-axis

The composite measure of image accuracy compared to the original object, on a scale of 0 to 1 is referred to as?

Modulation transfer function (MTF)

What affects visibility of detail?

15% rule, filtration, and radiographic grids

As the spatial frequency of objects increases,

MTF decreases

For general radiography, and MTF value of 1 is

Theoretically impossible

Imaging noise is different from quantum noise in that imaging noise

Is inherent in the imaging system

The Nyquist frequency is

Sampling a minimum of twice per cycle

When the sampling frequency is less than the Nyquist value,

The Moire effect can occur

The overall general shape of human anatomical structures are

Round or oval

Quantum noise impacts radiographic image quality by

Diminishing the visibility of recorded detail

A convenient and easy patient immobilization method an experienced radiographer will use is

A piece of tape wrapped around the patient's anatomy

What technique would yield the highest image quality?

600 mA, 85 kVp, 70 sec. exp time, 1.2 mm fs, 1.5 mm Al filtration, 4 lp/mm, MTF=40%

Calculate the penumbra for an image taken with a 1.0 mm focal spot, at a 40 in. distance, and OID of 2 in.

0.05 mm

Calculate the penumbra for an image taken with a 2.0 mm focal spot, at a 72 in. distance, and OID of 1 in

0.03 mm

Calculate the SID necessary to achieve a penumbra of 0.8 mm if the focal spot size is 1.0 mm and the object is 3 inches from the detector

40 inches

Distortion is a misrepresentation of

size and shape

Size distortion in radiography can be _______ only

magnification

Size distortion is controlled by

SID, OID, and radiographic distances

As size distortion decreases, the resolution of recorded detail

Increases

The ____________ the SID, the ____________ the degree of magnification

Greater; smaller

Examination of body parts with a large inherent OID warrant a _____________ whenever possible

Large SID

What examination does not exhibit an inherently large OID?

AP lumbar spine

As OID increases and SID remains constant, entrance skin exposure (ESE)

Increases

Large patients receive a greater exposure than small patients bc their

SOD is decreased, OID is increased, and the entrance skin surface is closest to the source

What occurs when the tube or the IR are not properly aligned?

Elongation

What occurs when the part is improperly aligned?

Foreshortening

Proper alignment is achieved when the CR is ____________ to the part and __________ to the IR

Perpendicular; perpendicular

When the position of the patient is reversed, the direction of the tube angle must be _____________ to maintain the relationship

Reversed

X-ray tube angulations inherently

Change the SID and introduce magnification to some degree

Performing a routine chest radiograph in the AP projection will

Produce improved resolution of the thoracic spine

Opening up the intervertebral joints of the C-spine would best be accomplished with

The patient in an AP projection with a 40" SID

Enlargement of a digital radiographic image on the review monitor, is an example of

Electronic magnification

Positioning patients is intended to eliminate anatomical superimposition, from a radiologist perspective. To optimize resolution it is best to

Keep the CR and receptor perpendicular to the patient's anatomy, and rotate the part

What is the ratio between image size and magnification factor?

Object size

What is an image in which the object is actually shorter?

Elongation

What is best seen with the patient supine?

Kidneys

What is the magnification factor formula?

SID/SOD

SID/MF =

SOD

The _________ is inherently magnified in an AP projection

Patella

Calculate the MF when the SID is 40 in and the SOD is 25 in.

1.6

Calculate the MF when the SID is 72 in and the SOD is 25 in

2.88

Calculate the MF when the SID is 40 and the OID is 5 in

1.14

Calculate the MF when the SID is 72 in. and the OID is 2 in.

1.02

If a projected image measures 3 in. and the MF is 1.1, what is the size of the actual object?

2.72 in

If an object is measured at 4 in. in distance on the image and 2 in. from the film, what is the actual size of the object if the SID is 40 in.

3.8

If an object is measured as 4 in. in diameter on the image and 4 in. from the film, what is the actual size of the object if the SD is 40 in.?

3.6

If an object measures 2 cm and the image measures 4 cm, what is the percent magnification of the object?

100%

If an object is measured as in 4 in diameter on the image and 2 in from the film, what is the actual size of the object?

3.8 in

If an object measures 2 cm and the image measures 3 cm, what should the percent magnification of the object?

50%

Which statement is true?

A. As MAs increases, scatter decreases

B. As MAs decreases, quantum noise can appear

C. As MAs increases, remittent radiation decreases

B. As MAs decreases, quantum noise can appear