Rad 227 Exercise 8

How many milliseconds are in .05 seconds?

50

How will increasing the focal spot size affect the spatial resolution in a radiograph?

Decrease spatial resolution **Increasing the focal spot size increases the divergent angle of the x-ray beam, which decreases spatial resolution.**

How does magnification affect image quality? 1. Decreases spatial resolution 2. Decreases receptor exposure 3. Lowers contrast

Decreases spatial resolution

A light radiograph may be caused by which of the following?

Grid cuttoff

What is the greatest advantage of digital imaging?

contrast resolution

Tube angulation will produce which of the following types of shape distortion?

elongation

Which of the following focal spot sizes should be used when doing macro radiography?

.3 mm ***Macroradiography is magnifying an object. It is often used in angiography and mammography. The smaller the focal spot size the less unsharpness***

Which of the following would be used to minimize size distortion? 1. Shortest possible OID 2. Smallest focal spot size 3. Longest SID

1 & 3

How could a KUB taken at 25 mAs, 70 kVp and a 400 speed film-screen system be properly converted for CR? 1. 25 mAs, 80 kVp 2. 50 mAs, 60 kVp 3. 50 mAs, 70 kVp

1 & 3 only **25 mAs at 80 kVp would reduce patient exposure and still produce a quality image. 50 mAs at 70 kVp would produce an optimum quality image.**

How well an imaging system reproduces the actual object is referred to as what?

Modulation transfer function

Which of the following types of motion must be considered when setting a radiographic technique? 1. Voluntary 2. Involuntary 3. Equipment

1, 2, 3

Which of the following methods can be used to control motion by reducing exposure time? 1. Use highest mA station possible 2. Increase kVp 3. Decrease SID

1, 2, 3 **Increasing mA or kVp and/or decreasing SID are ways of increasing exposure. Therefore, time can be reduced to maintain the proper exposure.**

The histogram is used to automatically rescale the image to the proper brightness. Which of the following could cause an error with the histogram analysis? 1. Exposure field NOT detected 2. Unexpected metal in the data set 3. Gross overexposure

1. 2, 3

What are the advantages of using high kVp techniques? 1. Less patient exposure 2. Longer tube life 3. All parts are well penetrated

1.2,3

A technique of 300 mA, 1/10 second and 60 kVp is to be changed to 69 kVp, what would be the new time?

1/20 sec ***A 15% increase in kVp will double the exposure to the image receptor. Therefore, you would have to cut your time in half to compensate. 1/2 of 1/10 is 1/20.***

Which of the following techniques will produce the highest contrast?

100 mAs, 70 kVp, 8:1 grid ***he lowest kVp and the highest grid ratio will produce the highest radiographic contrast***

What percentage increase is usually used for magnification radiography?

100% ****Magnification radiography can produce an image twice as large as the object by putting the object halfway between the source and the image receptor (100%). Mammography magnification uses a 50% increase.***

Which of the following grid ratios should be used to maintain contrast when using over 100 kVp?

12:1 **100 kVp x rays will mostly scatter when passing through a patient. Therefore, a high ratio grid is needed to absorb this large amount of scatter radiation.**

Which of the following imaging plates should be selected to produce an image with the best spatial resolution? A. 18 cm x 24 cm (8 x 10) B. 24 cm x 30 cm (10 x 12) C. 30 cm x 35 cm (11 x 14) D. 35 cm x 43 cm (14 x 17)

18 cm x 24 cm (8 x 10)

What advantage is there to magnifying an object? 1. Spatial resolution increases 2. Small objects become visible 3. There is less distortion

2 only

A technique of 400 mA, .25 seconds, non-grid could be converted to a technique of 200 mA, with an 8:1 grid at _______ seconds.

2.0 sec

If 50 mAs provides an optimum exposure at 40", how much mAs is necessary at 80"?

200 mAs **According to the inverse square law, if the distance is doubled, the mAs must be increased 4 times in order to maintain the same receptor exposure.***

When an object is placed halfway between the tube and the image receptor the image will be how many times larger?

2x **If the SID is 40" and the object is placed half way between the tube and the image receptor it would be placed at 20" SOD. Magnification = SID/SOD or 40"/20" = 2.**

What is the spatial resolution of a 24 cm x 30 cm (10 x 12) imaging plate?

4 lp/mm **A 24 cm wide imaging plate is also 240 mm wide. If the plate is scanned at a frequency of 2000, then there would be 8 pixels/mm. It takes two pixels to make a line pair, so the spatial resolution would be 4 lp/mm.***

Which of the following speed classes will produce the greatest brightness on a radiograph?

400 speed **the higher the speed class, the greater the brghtness**

The SID should be reduced by 1 inch for every _______ degrees of CR angle.

5 degrees

How much should kVp be increased when radiographing a part in a fiberglass orthopedic cast?

5 kvp

A sampling frequency of 10 pixels per millimeter would produce how much spatial resolution?

5 line pairs per millimeter **It takes 2 pixels to make a line pair, therefore, 10 pixels would produce 5 line pairs per millimeter.**

How could a knee taken at 4 mAs, 70 kVp and a 400 speed film-screen system be properly converted for CR? 1. 4 mAs, 80 kVp 2. 8 mAs, 60 kVp 3. 8 mAs, 70 kVp

8 mas 79 kvp

Which of the following can be done to help compensate for an angled part?

Align the tube, part and image receptor

Which of the following can be used to reduce unsharpness? 1. Increase SID 2. Decrease focal spot size 3. Decrease OID

All of the above

Which of the following is a reason for the loss of spatial resolution in a radiograph? A. Large focal spot B. OID C. Patient motion

All of the above

Why is automatic exposure control (AEC) useful in controlling receptor exposure? 1. Receptor exposure must remain constant 2. Faulty receptor exposure causes repeats 3. Receptor exposure greatly affects quality

All the above

The size of the pixel produced when an imaging plate is read depends on which of the following? 1. The speed of the imaging plate as it passes through the reader 2. The frequency with which the data is sampled 3. The dimensions of the laser beam

All the above **The slower the imaging plate speed the better the spatial resolution. However, the slower the speed the longer it takes to acquire the image. The sampling frequency and the laser dimension also contribute to pixel size and therefore, spatial resolution***

Where is the ionization chamber located in an automatic exposure control (AEC) device?

Between the patient and the IR **The ionization chamber must be located between the patient and the image receptor so the number of x rays can be measured before they reach the image receptor. Once the correct number of x rays have passed through the patient the exposure will automatically shut off.**

Which of the following radiographic procedures requires a long scale of contrast? A. Lumbar spine B. Chest C. Myelography D. Angiography

CHest

uminance refers to the brightness of the light emitted from an image display monitor. What are the SI units for luminance?

Candela per square meter

Scatter radiation will have the greatest effect on which of these radiographic qualities? A. Spatial resolution B. Receptor exposure C. Contrast D. Distortion

Contrast

Spatial resolution can be improved by reducing which of the following? A. SID B. SOD C. Focal spot size D. Patient size

Focal spot size

If the central ray is perpendicular to the image receptor, but the part is angled, what will be the result?

Foreshortening

Which of the following directly influences radiographic contrast? A. mA B. SID C. Grid ratio D. Exposure time

Grid ratio ***Radiographic grids remove scatter radiation before it reaches the image receptor to cause fog. This decrease in fog provides a higher contrast radiograph.***

Fog will have the greatest adverse effect on which of the following? A. Low brightness areas of the image B. Middle brightness areas of the image C. Median brightness areas of the image D. High brightness areas of the image

High brightness areas of the image

Subject contrast will be the lowest with which of the following body types? A. Sthenic B. Asthenic C. Hyposthenic D. Hypersthenic

Hypersthenic **Subject contrast refers to the differences in tissue densities in the patient. Large patients (hypersthenic) have a higher fat content which creates smaller differences between tissues which produces a lower contrast radiograph.***

Which of the following occurs when the OID is increased? A. Image size is reduced B. Image is magnified C. Image is elongated D. Image is foreshortened

Image is magnified **increasing the OID, reduces the SOD, which increases the magnification ratio (SID/SOD). **

If it is impossible to get the part close to the image receptor, what can be done to compensate?

Increase SID **Having the part away from the image receptor creates magnification. The magnification ratio is SID/SOD. If the SID increases, the SOD will increase an equal amount which will reduce magnification.**

Which of the following would increase the contrast-to-noise ratio (CNR)? A. Increase x-ray intensity B. Increase scatter radiation C. Increase electronic noise D. Increase background noise

Increase x ray intensity **As the number of x rays increases, noise decreases. This increases the contrast-to-noise ratio**

As contrast lowers, how is the number of brightnesses in an image affected?

Increases ***Lower contrast means a longer scale of contrast. Scale of contrast refers to the number of different brightnesses seen in the radiograph. A long scale means there are several brightnesses visible.***

How are mA and seconds related to each other when used to maintain exposure?

Inversely proportional **Inversely proportional means that if one increases the other must decrease in order to maintain the same exposure.**

The image in an image receptor after exposure but before processing is known as what?

Latent **The latent image is produced when the image receptor captures the x-ray image. This produces an invisible image**.

Fractional focal spots are necessary for which of the following? A. Magnification radiography B. Stereoradiography C. Soft tissue radiography D. Tomography

Magnification radiography

Why is contrast needed in a radiographic image?

Makes detail visible

The image after processing is known as what?

Manafest

A wavy pattern that results when two geometrically parallel lines are superimposed is referred to as what?

Miore

Geometric unsharpness is directly proportional to which of the following? 1. SID 2. OID 3. SOD

OID

Which of the following accessories can be used to demonstrate a scale of contrast or test for contrast?

Penetrometer ***A penetrometer, also known as a step wedge, is used to produce a scale of contrast. This can be used to test kVp accuracy, mAs reciprocity and a number of other quality assurance tests.***

Density was the term used to describe the overall blackening of a film-screen radiograph. What term is used in digital imaging to describe this radiographic quality?

Receptor exposure

What is the main reason why beam filters are used in radiography?

Reduces patient exposure

Which of the following factors will NOT have an effect on radiographic contrast? A. Patient B. Grid ratio C. SID D. Radiation fog

SID

Which of the following is NOT one of the three elements that affect shape distortion? A. Central ray B. SID C. Object D. Image receptor

SID

Which of the primary factors will always have an effect on spatial resolution?

SID

Which of the following would NOT be used as contrast media in radiography? A. Air B. Saline C. Barium sulfate D. Sodium iodide

Saline **Two types of contrast media are used in radiography, negative and positive. With negative contrast media (air) the x rays penetrate it very easily and produce a negative (dark) affect. Positive media (barium and iodine) absorbs the x rays and produces a light affect. Normal saline does neither of these.**

What are the two types of distortion that can reduce the quality of a radiograph?

Size and shape

The measure of the amount of detail in a digital image defines which of the following? A. Brightness B. Spatial resolution C. Definition D. Detail

Spacial resolution **Spatial resolution is measured in line pairs per millimeter.***

A flat-panel detector's detector element (DEL) size determines which of the following? A. Dynamic range B. Detective quantum efficiency (DQE) C. Spatial resolution D. Speed class

Spatial resolution ***With DR flat-panels, the pixel size is determined by the detector element (DEL) size; with CR imaging plates the pixel size is determined by the sampling frequency.**

The ability of a digital system to display details (expressed as the number of line pairs per millimeter) is known as what?

Spatial resolution **A display monitor must be able to display at least 2.5 line pairs per millimeter according the American College of Radiology's digital standards.**

Which of the following radiographic qualities determines the sharpness of detail in the finished radiograph?

Spatial resolution and distortion ***Sharpness of detail is controlled by maximizing spatial resolution and minimizing distortion.****

Which of the following tests will determine the focal spot size? A. Safelight test B. Wire mesh test C. Wisconsin test cassette D. Star pattern test

Star Pattern Test **Focal spot sizes can be determined by a pinhole camera or a star resolution pattern.**

Which of the following will occur when the OID is decreased?

The image is closer to actual size ***You can never get the image to be equal to the object's actual size, but decreasing the OID will produce an image that is closer to the actual size.**

What is the correct name for the loss of sharpness due to the use of a large focal spot?

Unsharpness

The brightness of a digital image affects which of the following? A. Sharpness of detail B. Visibility of detail C. Distortion D. Exposure

Visibility

Size distortion can be used to an advantage for which of the following radiographic procedures? A. Gastrointestinal B. Skeletal C. Angiographic D. Neurological

angiographic

If the mA is increased, how must the time be changed in order to maintain the same exposure?

decreased **mAs is the controlling factor for exposure. Therefore, if mA is increased, time must be decreased in order to maintain the same exposure.**

If the exposure time is cut in half, how must the mA be adjusted to maintain the same exposure?

doubled

Which of the following will NOT contribute to the underexposure of an image? A. mA set too low B. kVp set too low C. SID set too high D. Focal spot size too large

focal spot size too large

Size distortion is affected by which of the following? A. Intrinsic factors B. Geometric factors C. Motion factors D. Technical factors

geometric factors

How would an image with just a few, wide brightness differences be described?

high contrast

Contrast resolution is a major advantage of digital imaging. What determines high contrast resolution in a digital image?

high exposure and low noise

Spatial resolution is NOT affected by which of the following? A. SID B. SOD C. OID D. kVp

kvp ***kVp will affect the visibility of detail by the amount of scatter radiation it produces. The higher the kVp the more scatter.***

Which of the following scales of contrast will produce a more consistent radiographic quality?

long scale **A long scale of contrast provides more exposure latitude which makes it easier to produce consistent quality radiographs.***

After the values of interest have been determined from the histogram, which of the following is used to readjust those numbers to produce the proper contrast? A. Contrast chart B. Look-up table C. Values graph D. Number diagram

look up table

Which of the following controls contrast in a digital system?

look up table

If the SID is halved, which of the following changes must be made in order to maintain the same exposure? A. mAs halved B. mAs reduced by 4X C. mAs doubled D. mAs increased by 4X

mAs reduced by 4x ***Cutting the SID in half will increase the exposure to the image receptor by 4X. Therefore, mAs would have to be reduced by 4X to maintain the same exposure.***

Spatial resolution in digital imaging is determined by which of the following? A. Exposure to the image receptor B. Brightness and contrast C. Matrix size D. Matrix size and the size of the field of view

matrix size and the size of the FOV

Which of the following will have the greatest effect on size distortion? A. SID B. OID C. Focal spot size D. Image size

oid

Which of the following defines image brightness? A. Pixel light intensity B. Difference in light intensity between pixels C. Sharpness of the pixels D. Visibility of the pixels

pixel light itensity

An insufficient amount of mAs will produce a digital image with:

quantum noise

Which of the following will have the greatest effect on radiographic contrast?

reducing scatter radiation

What type of distortion results from an increase in OID?

size

Which of the following will occur when the tube angle is decreased? A. The image will be foreshortened B. Contrast will be lower C. Shape distortion will decrease D. Size distortion will increase

shape disrotion will decrease **The greater the tube angle the greater the elongation of the object. If the tube angle is decreased, the elongation will decrease which means shape distortion decreases.**

Which of the following may be the cause of an overexposed image? A. mAs too low B. OID too high C. SID too low D. Grid ratio too high

sid too low

Which of the following is NOT considered one of the geometric factors that control spatial resolution?

size of the object **OID, SID and focal spot size all affect the angle of the x-ray beam, which affects spatial resolution.**

Which of the following is the main determinant in selecting a focal spot size?

the mA used **A small focal spot cannot dissipate the heat generated from a high mA technique. Therefore, the radiographer must go to a larger focal spot or a low mA at a longer exposure time.***