34 Questions
What is the primary effect of projection radiography?
To record an image of a 3D object in 2D
What is the result of the superposition of anatomy along each ray in projection radiography?
A 2D image with superposition of anatomy
What is the typical range of fine focal spots in radiography?
0.3-1.0 mm
What is the main factor that affects the magnification of an object in projection radiography?
The OID of the object
Why do objects appear progressively larger in a projection radiograph?
Due to their differences in position
Why must lower mAs be used with fine focal spots?
To protect the tube from heating effects
What is the effect of angulation on the projected length of an angled object?
It causes foreshortening of the object
What is the formula for magnification (m) in radiography?
XF / SOD
What is the effect of increasing the OID in magnification imaging?
Increased magnification
What is the ideal image sharpness produced by?
A point source
What is the main factor that limits the spatial resolution in a projection radiograph?
The image receptor factors
What is the compromise required in choosing an appropriate focal spot size?
Between exposure time and resolution
What depends on the focal spot size in projection radiography?
The spatial resolution of the image
What is the result of using a very small focal spot size?
Good spatial resolution with low tube current
What is the effect of increasing the FID on magnification imaging?
Increased magnification
What is the effect of motion blur on magnification imaging?
Decreased spatial resolution
What is the effect on the scatter fraction at the image receptor when increasing the OID?
It decreases substantially
What is the consequence of increasing the OID on image sharpness?
It decreases due to geometric blur
What is the primary consideration for choosing the kV setting in screen-film systems?
Required contrast
What is the effect of magnification on spatial resolution?
It improves compared to contact methods
What is the reason for increasing the mAs when increasing the OID?
To maintain the dose to the image receptor
What is the limitation of using magnification for large body regions?
It requires a larger image receptor
What is the consequence of increasing the OID on the SNR?
The effect on SNR is not mentioned
What is the difference between magnification and a simple zoom of a digital image?
Magnification improves spatial resolution, but a simple zoom does not
What is the primary source of noise in imaging?
Random arrival of photons at the image receptor
What is the formula to determine the number of detected photons required per unit area?
N = k2/C2d2
What is the effect of increasing contrast C on the number of photons required at the image receptor?
It reduces the number of photons required
What is the usual value of k in Rose's expression?
5
What is the effect of reducing kV on image quality?
It produces an image of satisfactory quality at a lower image receptor dose
What is the effect of reducing kV on patient dose?
It increases patient dose
How does patient dose (Ki) relate to mAs and kV?
Ki is proportional to mAs and approx to kV2
How does penetration through the patient relate to kV?
It is proportional to kV3
How does the total dose to the image receptor depend on kV?
It depends approximately on kV5
What is the 15% rule in technique selection?
A reduction in kV requires an increase in mAs of at least 15%
Understanding the primary effects of projection radiography, including the superposition of anatomy and its implications on equipment design, image production, and interpretation.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
