Phys Chapter 29

Distortion is a misrepresentation of
size only.
shape only.
size and shape.
detail.
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Terms in this set (31)
Distortion is a misrepresentation of
size only.
shape only.
size and shape.
detail.
size and shape
Size distortion in radiography can be ____ only.
foreshortening
magnification
elongation
minimization
magnification
Size distortion is controlled by
SID.
OID.
radiographic distances.
all of the above.
all of the above
As size distortion decreases, the resolution of recorded detail
increases.
decreases.
is not affected.
is altered due to digital reprocessing.
increases
The ____ the SID, the ____ the degree of magnification.
greater; larger
greater; smaller
lesser; smaller
SID has no effect on magnification.
greater; smaller
Examinations of body parts with a large inherent OID warrant a ____ whenever possible
small SID
large SID
small SOD
large focal spot
large SID
Which examination does not exhibit an inherently large OID?
AP lumbar spine
lateral cervical spine
lateral chest
AP facial bones
AP lumbar spine
As OID increases and SID remains constant, entrance skin exposure (ESE)
remains unchanged.
decreases.
increases.
none of the above.
increases
Large patients receive a greater exposure than small patients because their
SOD is decreased.
OID is increased.
entrance skin surface is closer to the source.
all of the above.
all of the above
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.
25 percent
125 percent
0.25 percent
1.25 percent
125 percent
Which of the following occurs when the tube or the image receptor are not properly aligned? elongation magnification foreshortening minificationelongationWhich one of the following occurs when the part is improperly aligned? elongation magnification foreshortening minificationforeshorteningProper alignment is achieved when the central ray is ____ to the part and ____ to the image receptor. perpendicular; parallel parallel; perpendicular perpendicular; perpendicular parallel; parallelperp; perpWhen the position of the patient is reversed, the direction of the tube angle must be ____ to maintain the relationship. maintained decreased increased reversedreversedBecause the x-ray beam is divergent, -minification is impossible. -minification is collimated off from the edges of the beam. -minification is greater with a smaller target angle. -minification is greater with a larger target angle.minification is impossible.X-ray tube angulations inherently increase spatial resolution. change the SID. introduce magnification to some degree. both b and cboth b and c.In order to achieve a true SID of 40" with an x-ray tube angle of 30 degrees, the overhead scale should read 23 inches. 95 cm. 34.6 inches. both b and c.34.6 inches.Performing a routine chest radiograph in the anterioposterior (AP) projection will -decrease heart size on the image. -demonstrate higher resolution of the anterior ribs. -produce improved resolution of the thoracic spine. -decrease breast exposure.produce improved resolution of the thoracic spine.A renal calculus that measures 0.2 mm in size -cannot be visualized with an effective focal spot of 0.5 mm focal spot due to penumbral overlap. -is best seen with magnification and a large focal spot. -most likely will be visualized with a small radiographic tube angle using a large target angle. -all of the above.cannot be visualized with an effective focal spot of 0.5 mm focal spot due to penumbral overlap.Opening up the intervertebral joints of the cervical spine would best be accomplished with -the patient in a PA projection at 72" SID. -the patient in an AP projection with a 40" SID. -a perpendicular central ray at 72" SID. -the patient in a PA projection with a 40" SID.the patient in an AP projection with a 40" SID.With digital image receptors (CR/DR) -the geometric factors of distortion do not apply. -EI#s are inaccurate due to elongation distortion. -computer postprocessing corrects for shape distortion. -none of the above.none of the above.A radiographic magnification factor(MF) of โˆ’.15 indicates -the object size and image size are nearly equal. -nothing, since negative MF is not possible. -the image size is smaller than the object size. -a change in OID is needed.nothing, since negative MF is not possible.Enlargement of a digital radiographic image on the review monitor, is an example of purposeful geometric magnification. electronic magnification. shape distortion. digital histogram distortion.electronic magnification.Positioning patients is intended to eliminate anatomical superimposition, from a radiologist perspective. To optimize image resolution it is best to -keep the central ray and receptor perpendicular to the patient's anatomy, and rotate the part. -minimize central angulation and rotate the part only slightly. -use the small focal spot and extend the degree of part rotation. -lower the SID and increase the OID with part rotation.keep the central ray and receptor perpendicular to the patient's anatomy, and rotate the part.Shape distortion is calculated -as the ratio of SID and SOD. -using the tube angle and OID. -automatically in the computer postprocessing. -none of the above.none of the above.ratio between image size and MFobject sizean image in which the object is actually shorterelongationbest seen with the patient supinekidneysMFSID SODSID รท MFsodinherently magnified in AP projectionpatella