Chapter 28 spatial resolution quiz

Formula to calculate penumbra

P= FSxOID/SOD

equation to find an object's actual size

O=!/M Where O=object size I=Image size M=magnification factor

X-ray tube angulations inherently: a. increase spatial resolution b. change the SID c. introduce magnification to some degree d. both b and c

d. both b and c

Factors affecting recorded detail include: a. kVp and filtration b. radiographic grids and collimation c. mAs and grid ratio d. focal spot size and patient thickness

d. focal spot size and patient thickness

A pixel bit depth of 2^16 will demonstrate _______ shades of gray: a. 32 b. 256 c. 4096 d. none of the above

d. none of the above

Shape distortion is calculated: a. as the ratio of SID and SOD b. using the tube angle and OID c. automatically in the computer postprocessing d. none of the above

d. none of the above

Change to 12:1 grid (from 8:1) (CONTRAST)

+

Decrease filtration to 1.75 mm (CONTRAST)

+

Decrease to a 50 RS (DETAIL)

+

Develop at 100 degrees (CONTRAST)

+

Increase to 14"x17" field size (DENSITY)

+

Increase to a 1" OID (CONTRAST)

+

Increase to a 1" OID (DISTORTION)

+

Increased time to .45 sec (DENSITY)

+

Reduce to 30" SID (DISTORTION)

+

Use a 2 mm FS (from 1 mm) (DISTORTION)

+

Use a fractional focal spot (DETAIL)

+

Change to 12:1 grid (from 8:1) (DENSITY)

-

Increase filtration to 3 mm (DENSITY)

-

Increase kVp to 100 (from 80) (CONTRAST)

-

Increase tissue density (CONTRAST)

-

Increase tissue density (DENSITY)

-

Increase to 14"x17" field size (CONTRAST)

-

Increase to 50" SID (DENSITY)

-

Increase to a 1" OID (DETAIL)

-

Reduce to 30" SID (DETAIL)

-

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

100%

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

50%

Magnification Factor formula

M = SID/SOD

Spatial resolution in digital imaging is determined by the: a. bit depth b. matrix size c. pixel size d. all of the above

d. all of the above

Of the choices given below, which one would yield the highest image quality? a. 600 mA, 85 kVp, .70 sec exp time, 1.2 mm fs, 1.5 mm Al filtration, 4 lp/mm, MTF=40% b. 300 mA, 97 kVp, .35 sec exp time, 1.2 mm fs, 1.5 mm Al filtration, 3 lp/mm, MTF=25% c. 600 mA, 85 kVp, .70 sec exp time, 0.6 mm fs, 1.0 mm Al filtration, 1.5 lp/mm, MTF=60% d. 200 mA, 110 kVp, .25 sec exp time, 2.0 mm fs, 1.2 mm Al filtration, 2 lp/mm, MTF=30%

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

Which examination does not exhibit an inherently large OID? a. AP lumbar spine b. lateral cervical spine c. lateral chest d. AP facial bones

a. AP lumbar spine

When switching from a 400 RS film screen combination to a 200 RS system, one should expect a. an increase in spatial resolution b. to use a longer exposure time c. a decrease in patient dose d. a decrease in spatial resolution

a. an increase in spatial resolution

A renal calculus that measures 0.2 mm in size: a. cannot be visualized with an effective focal spot of 0.5 mm focal spot due to penumbral overlap b. is best seen with magnification and a large focal spot c. most likely will be visualized with a small radiographic tube angle using a large target angle d. all of the above

a. cannot be visualized with an effective focal spot of 0.5 mm focal spot due to penumbral overlap

Which of the following occurs when the tube or the image receptor are not properly aligned? a. elongation b. magnification c. foreshortening d. minification

a. elongation

As size distortion decreases, the resolution of recorded detail: a. increases b. decreases c. is not affected d. is altered due to digital reprocessing

a. increases

Positioning patients is intended to eliminate anatomical superimposition, from a radiologist perspective. To optimize image resolution it is best to: a. keep the central ray and receptor perpendicular to the patient's anatomy, and rotate the part b. minimize central angulation and rotate the part only slightly c. use the small focal spot and extend the degree of part rotation d. lower the SID and increase the OID with part rotation

a. keep the central ray and receptor perpendicular to the patient's anatomy, and rotate the part

Because the x-ray beam is divergent: a. minification is impossible b. minification is collimated off from the edges of the beam c. minification is greater with a smaller target angle d. minification is greater with a larger target angle

a. minification is impossible

You have completed a chest radiograph on a 2-month-old infant using a restraining device at a 72" SID. Because of the design of the device, your OID is suboptimum. The image reveals good resolution of the bony anatomy but the pulmonary vasculature is blurred. The EI value is 2040 and the target EI value is 2000. In an effort to improve the quality of the repeat image, the competent radiographer would: a. raise the mA and decrease the exposure time b. decrease the SID and maintain the same mAs c. switch to a small focal spot d. ask for mild sedation of the infant to decrease respiration

a. raise the mA and decrease the exposure time

The overall general shape of human anatomical structures are: a. round or oval b. linear c. cuboid d. curvilinear

a. round or oval

The ________ represents a depth to the information in the digital image a. z axis b. y-x grid matrix c. y axis d. x-y grid matrix

a. z axis

The magnification factor for a radiographic procedure is calculated at 1.25. It may be assumed that there is a _____ magnification of the object size a. 25 percent b. 125 percent c. 0.25 percent d. 1.25 percent

b. 125 percent

As object spatial frequencies increase: a. MTF increases b. MTF decreases c. Nyquist is not a factor d. MTF is unaffected

b. MTF decreases

As the spatial frequency of objects increases: a. MTF increases proportionally b. MTF decreases c. MTF values approach 1 d. MTF computes to a value of 1

b. MTF decreases

Spatial resolution is improved when: a. OID increases b. OID decreases c. SID decreases d. the x-ray tube is angled

b. OID decreases

Spatial resolution is improved when: a. OID increases b. SID increases c. SID decreases d. the receptor is angled

b. SID increases

Which radiograph below exhibits the best recorded detail? a. a PA chest radiograph for evaluation of the heart at 40 in b. a PA chest radiograph for evaluation of the heart at 72 in c. a lordotic projection of the chest at 72" d. an AP chest radiograph for evaluation of the heart at 72 in

b. a PA chest radiograph for evaluation of the heart at 72 in

In general radiography, quantum noise is: a. filtered out of images b. a function of mAs and kVp c. designed into the receptor specifications d. a recorded detail parameter

b. a function of mAs and kVp

Enlargement of a digital radiographic image on the review monitor, is an example of a. purposeful geometric magnification b. electronic magnification c. shape distortion d. digital histogram distortion

b. electronic magnification

The ______ the SID, the _____ degree of magnification a. greater, larger b. greater, smaller c. lesser, smaller d. SID has no effect on magnification

b. greater, smaller

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

Examinations of body parts with a large inherent OID warrant a ______ whenever possible: a. small SID b. large SID c. small SOD d. large focal spot

b. large SID

The traditional unit of resolution measurement typically used in film/screen imaging is: a. dots per milimeter b. line pairs per millimeter c. pixel size d. the DEL size

b. line pairs per millimeter

On a PA projection of the wrist, you notice what appears to be a soft tissue mass superimposed over the bony anatomy. When you inspect the patient, you notice the presence of a large linear scar form a previous injury. The visualization of this scar is primarily due to what characteristic of digital detectors: a. temporal resolution b. low contrast resolution c. high contrast resolution d. the DEL fill factor

b. low contrast resolution

Size distortion in radiography can be _______ only: a. foreshortening b. magnification c. elongation d. minimization

b. magnification

The best method for controlling motion when the patient is unable to cooperate is to: a. decrease the focal spot size b. maintain mAs, while decreasing time c. maintain mAs, while decreasing mA d. decrease kVp

b. maintain mAs while decreasing time

The composite measure of image accuracy compared to the original object, on a scale of 0 to 1 is referred to as: a. line spread function b. modulation transfer function c. point spread function d. noise reduction function

b. modulation transfer function

A radiographic magnification factor (MF) of -.15 indicates: a. the object size and image size are nearly equal b. nothing, since negative MF is not possible c. the image size is smaller than the object size d. a change in OID is needed

b. nothing, since negative MF is not possible

The Nyquist frequency is: a. important in analog imaging b. sampling a minimum of twice per cycle c. unique to radiography d. related to involuntary motion

b. sampling a minimum of twice per cycle

When the sampling frequency is less than the Nyquist value: a. aliasing is eliminated b. the Moire effect can occur c. patient dose must increase d. the Nyquist value must be altered

b. the Moire effect can occur

opening up the intervertebral joints of the cervical spine would best be accomplished with: a. the patient in a PA projection at 72" SID b. the patient in an AP projection with a 40" SID c. a perpendicular central ray at 72" SID d. the patient in PA projection with a 40" SID

b. the patient in an AP projection with a 40" SID

As a last resort, which human immobilizer is used to hold a patient in position? a. the radiography student b. the radiologic technologist c. the ER nurse d. the male relative

b. the radiologic technologist

In order to achieve a true SID of 40" with an x-ray tube angle of 30 degrees, the overhead scale should read: a. 23 inches b. 95 cm c. 34.6 inches d. both b and c

c. 34.6 inches

Spatial resolution is: a. the degree of geometric sharpness b. definition c. the accuracy of the structural lines actually recorded in the radiographic image d. all of the above

d. all of the above

From the choices below, select the FALSE statement regarding Contrast-Noise-Ratio (CNR): a. It is the ratio of the signal difference between areas of interest b. It is affected by SNR c. A high CNR is only possible with a low SNR d. If image noise is high, the CNR will be low

c. A high CNR is only possible with a low SNR

A convenient and easy patient immobilization method an experienced radiographer will use is: a. high mA and short exposure time b. a high kVp and low mA c. a piece of tape wrapped around the patient's anatomy d. a tissue bolus material to hold the body part in position

c. a piece of tape wrapped around the patient's anatomy

In order to improve the temporal resolution on an image: a. a longer SID should be used b. a smaller x-ray beam angle should be used c. a shorter exposure time should be used d. the 15% rule should be considered

c. a shorter exposure time should be considered

Quantum noise impacts radiographic image quality by: a. decreasing geometric sharpness b. increasing temporal resolution c. diminishing the visibility of recorded detail d. adding artifacts to the image

c. diminishing the visibility of recorded detail

Which of the following occurs when the part is improperly aligned: a. elongation b. magnification c. foreshortening d. minification

c. foreshortening

As OID increases and SID remains constant, entrance skin exposure (ESE): a. remains unchanged b. decreases c. increases d. none of the above

c. increases

Which can negatively impact recorded detail: a. using small focal spot b. longer SID c. involuntary motion d. minimal OID

c. involuntary motion

Imaging noise is different from quantum noise in that imaging noise: a. is a function of mAs b. is dependent upon kVp c. is inherent in the imaging system d. cannot be filtered out

c. is inherent in the imaging system

Poor spatial resolution is caused by unacceptable levels of: a. IR exposure b. umbra c. penumbra d. contrast

c. penumbra

Proper alignment is achieved when the central ray is ____ to the part and ____ to the image receptor: a. perpendicular, parallel b. parallel, perpendicular c. perpendicular, perpendicular d. parallel, parallel

c. perpendicular, perpendicular

Performing a routine chest radiograph in the anteroposterior (AP) position will: a. decrease heart size on the image b. demonstrate higher resolution of the anterior ribs c. produce improved resolution of the thoracic spine d. decrease breast exposure

c. produce improved resolution of the thoracic spine

Distortion is a misrepresentation of: a. size only b. shape only c. size and shape d. detail

c. size and shape

For general radiography, an MTF value of 1 is: a. average b. suboptimum c. theoretically impossible d. a function of mAS

c. theoretically impossible

A digital detector with a high fill factor: a. will produce poor resolution b. will require longer processing time c. will produce high resolution d. requires more radiation exposure

c. will produce high resolution

All of the following affect visibility of detail EXCEPT: a. 15% rule b. filtration c. radiographic grids d. SID

d. SID

As focal spot size decreases: a. umbra is improved b. penumbra decreases c. spatial resolution increases d. all of the above

d. all of the above

Large patients receive a greater exposure than small patients because their: a. SOD is decreased b. OID is increased c. entrance skin surface is closer to the source d. all of the above

d. all of the above

Penumbra decreases as: a. focal spot decreases b. OID decreases c. SID increases d. all of the above

d. all of the above

Size distortion is controlled by: a. SID b. OID c. radiographic distances d. all of the above

d. all of the above

With digital image receptors (CR/DR) a. the geometric factors of distortion do not apply b. EI #s are inaccurate due to elongation distortion c. computer postprocessing corrects for shape distortion d. none of the above

d. none of the above

When the position of the patient is reversed, the direction of the tube angle must be ____ to maintain the relationship: a. maintained b. decreased c. increased d. reversed

d. reversed

Change to 12:1 grid (from 8:1) (DETAIL)

no effect

Decrease filtration to 1.75 mm (DETAIL)

no effect

Increase filtration to 3 mm (DISTORTION)

no effect

Increase to 300 mA (DISTORTION)

no effect

Reduce to 30" SID (CONTRAST)

no effect