exposures II Test 8 sharpness of detail

Sharpness of detail is improved in a radiographic image by ______

• decreased OID

• Increased SID

• Immobilization

• Use of cones and cylinders (close collimation)

Sharpness of detail is not affected by ______

Anode not rotating during the exposure

The intensity of radiation would increase as the _______

SID is decreased

If the tube is angled with regard to the planes of the IR and if a thick object is parallel to the IR, ______ type distortion will result

Elongation

______ will contribute to geometric unsharpness

• FSS

• OID

• SID

• Image penumbra

To take advantage of the heel effect, the cathode portion of the tube should be directed toward the body area of the ______

Greatest thickness

If the small FS of an xray tube is used instead of the large FS, the penumbra will be ______

Decreased

An increase in the OID produces increased ______

More than one, but not all of the above

Variation in xray intensity along the longitudinal tube axis is known as the _______

Anode heel effect

Use of an increased OID is necessary in ______

Air gap techniques

Any variation in the true size and shape of the part being radiographed is defined as ______

Distortion

Which of the following factors minimizes distortion?

Correct use of the CR

What type of distortion results from an increased OID or a decreased SID?

Magnification of the object

A circular object measures 6 inches in diameter. If the magnification factor is equal to 1.8, what will be the image diameter? _______ inches

10.8

If the object is angled with regard to the plane of the IR with the CR perpendicular to the IR, _______ distortion will result

• foreshortening

• True

Size distortion can be lessened by the use of _______

A longer SID

In cases where it is impossible to position an object close to the IR, _____ would improve sharpness of detail

Increasing SID

Radiographic sharpness is improved at ______

More than one, but not all of the above

Which letter represents the following items according to the diagram:

Electron stream

B

Which letter represents the following items according to the diagram:

Target angle

A

Which letter represents the following items according to the diagram:

Effective focal spot size

D

Which letter represents the following items according to the diagram:

Actual focal spot size

C

Which of the following statements concerning the anode heel effect is incorrect?

The principle can be used effectively in foot examinations

For the control of motion, which of the following ma/time combinations would be most effective?

500 mA, 0.2 sec.

Decreasing OID will decrease ______

Magnification

The most significant factor in the consideration of size distortion is the ______

OID

The ______ portion of the xray beam should be most perpendicular to the part being examined

Central

When elimination of motion is absolutely essential for a radiographic examination, the best factor adjustment to make is to ______

Decrease the exposure time

Which of the following standard radiographic positions purposely employs shape distortion?

• AP coccyx

• PA semi axial clavicle

• Axial os calcis

• AP lumbo sacral joint

Radiographic misrepresentation of the shape of the structure is _______ distortion

More than one, but not all of the above

Penumbra is not influenced by _____

mA

Calculate the unsharpness factor (penumbra) in the following situation:

1 mm FSS, 5 inch OID, 40 inch SID

Unsharpness = ______ mm

0.14

The area marked X is referred to as the _____

Penumbra

For magnification radiography, the usual enlargement factor is _______ %

100

If an actual object measures 6 inches and it’s radiographic size is 12 inches, the magnification factor is _____%

100

Listed below is a series of guidelines. From the list, choose those which will keep true distortion and magnification to a minimum

2,3,4

The best method for limiting involuntary motion is _______

Reducing the exposure time

The primary prerequisite for magnification radiography is ______

A fractional FS

The ability of an imaging system to form a distinct image of two or more objects located close together is called ______

Resolution

What is the value of 40% of 30?

12

How will increasing system speed affect the recorded detail in a radiograph?

Decrease detail

Which of the following may be used to control voluntary motion during a radiographic examination?

• proper explanation of the procedure

• Short exposure time

• Immobilization

Which of the following situations will produce the greatest amount of size distortion?

40 in. SID, 7 in. OID

Which of the following can be used to reduce penumbra?

• decrease system speed

• Decrease FSS

• Increase SID

Which of the following affects shape distortion?

CR angulation

What is the average anode angle?

17 degrees

Fractional focal spots can range between _______?

0.1 mm- 0.3 mm

Which technique factor should be the prime consideration when choosing FSS?

mAs

What factor causes or creates penumbra?

FSS

The circular band on the rotating anode where electrons strike is the _____

Focal track

With all other factors remaining constant, the penumbral shadow will be the smallest at an SID of _____ in.

72

A magnified radiograph of the sella turcica is taken at an SID of 49 in. and an OID of 10 in. If the image of the sella turcica measures 16 mm, its actual size is ____ mm

12

From these anode illustrations, complete questions 50-52 by selecting A or B:

Which would be considered the anode with the largest effective FS

B

From these anode illustrations, complete questions 50-52 by selecting A or B:

Which tube would produce the best sharpness of detail

A

From these anode illustrations, complete questions 50-52 by selecting A or B:

Which tube would produce the most penumbra?

B

True or false:

Most modern tubes contain two different sized focal spots

True

True or false:

The steeper the anode bevel, the smaller the effective FSS

True

True or false:

Increased SID equals increased contrast

False

True or false:

Increased SID equals increased sharpness of detail

True

True or false:

Increased SID equals increased magnification

False

True or false:

Decreased SID equals increased penumbra

True

True or false:

Increased OID equals increased contrast

True

True or false:

Decreased OID equals increased density/ IR exposure

True

True or false:

No geometric changes will be apparent in the image as long as the SID/SOD ratio remains equal

True

True or false:

A larger target area enables a longer exposure

True

True or false:

To minimize unsharpness, you should place the body part with the greatest OID toward the anode end of the tube

True

True or false:

If you were to look at the anode from the position of the IR, you would be viewing the actual FS

False

True or false:

When motion is a problem, time can be reduced by half if the kVp is increased 15%

True

True or false:

Increase motion equals decreased contrast

True

True or false:

Increased grid ratio equals increased recorded detail

False

True or false:

All xray tube anode bevels are less than 45 degrees in order to keep the actual FS smaller than the affective FS

False

List three geometric factors affecting sharpness of detail

• focal spot size

• SID

• OID

Write the exposure maintenance formula (square law)

1.8 mR/hr

Write the magnification ratio formula

SID/SOD

Using the factors listed in #49, what would be the magnification percentage?

33.33%

Give an example of a projection you would use the anode heel effect in and state which anatomy you would place under the anode?

• AP T-Spine

• I would place the upper, thicker thoracic portion of the body under the cathode end and the lower thoracic area under the anode because it is thinner

Place the best answer in the blank provided. Each possible answer in the right hand column can be used once:

Quantity of radiation

Density/ IR exposure

Place the best answer in the blank provided. Each possible answer in the right hand column can be used once:

Sharpness of detail and contrast combined

Resolution

Place the best answer in the blank provided. Each possible answer in the right hand column can be used once:

Geometric sharpness

Sharpness of detail

Place the best answer in the blank provided. Each possible answer in the right hand column can be used once:

Misrepresentation

Distortion

Place the best answer in the blank provided. Each possible answer in the right hand column can be used once:

Density differences

Contrast