Geometry of Projection Radiography

What is the primary effect of projection radiography?

To record an image of a 2D object in 3D
To decrease the magnification of the object
To increase the spatial resolution of the image
To record an image of a 3D object in 2D (correct)

What is the result of the superposition of anatomy along each ray in projection radiography?

An image with increased spatial resolution
A 3D image of the patient
An image with no distortion
A 2D image with superposition of anatomy (correct)

What is the typical range of fine focal spots in radiography?

0.3-1.0 mm (correct)
1.0-3.0 mm
3.0-5.0 mm
0.1-0.3 mm

What is the main factor that affects the magnification of an object in projection radiography?

The OID of the object (A) Signup and view all the answers

Why do objects appear progressively larger in a projection radiograph?

Due to their differences in position (A) Signup and view all the answers

Why must lower mAs be used with fine focal spots?

To protect the tube from heating effects (B) Signup and view all the answers

What is the effect of angulation on the projected length of an angled object?

It causes foreshortening of the object (C) Signup and view all the answers

What is the formula for magnification (m) in radiography?

XF / SOD (B) Signup and view all the answers

What is the effect of increasing the OID in magnification imaging?

Increased magnification (A) Signup and view all the answers

What is the ideal image sharpness produced by?

A point source (D) Signup and view all the answers

What is the main factor that limits the spatial resolution in a projection radiograph?

The image receptor factors (A) Signup and view all the answers

What is the compromise required in choosing an appropriate focal spot size?

Between exposure time and resolution (D) Signup and view all the answers

What depends on the focal spot size in projection radiography?

The spatial resolution of the image (B) Signup and view all the answers

What is the result of using a very small focal spot size?

Good spatial resolution with low tube current (D) Signup and view all the answers

What is the effect of increasing the FID on magnification imaging?

Increased magnification (D) Signup and view all the answers

What is the effect of motion blur on magnification imaging?

Decreased spatial resolution (A) Signup and view all the answers

What is the effect on the scatter fraction at the image receptor when increasing the OID?

It decreases substantially (D) Signup and view all the answers

What is the consequence of increasing the OID on image sharpness?

It decreases due to geometric blur (C) Signup and view all the answers

What is the primary consideration for choosing the kV setting in screen-film systems?

Required contrast (B) Signup and view all the answers

What is the effect of magnification on spatial resolution?

It improves compared to contact methods (C) Signup and view all the answers

What is the reason for increasing the mAs when increasing the OID?

To maintain the dose to the image receptor (D) Signup and view all the answers

What is the limitation of using magnification for large body regions?

It requires a larger image receptor (C) Signup and view all the answers

What is the consequence of increasing the OID on the SNR?

The effect on SNR is not mentioned (D) Signup and view all the answers

What is the difference between magnification and a simple zoom of a digital image?

Magnification improves spatial resolution, but a simple zoom does not (A) Signup and view all the answers

What is the primary source of noise in imaging?

Random arrival of photons at the image receptor (A) Signup and view all the answers

What is the formula to determine the number of detected photons required per unit area?

N = k2/C2d2 (C) Signup and view all the answers

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 (C) Signup and view all the answers

What is the usual value of k in Rose's expression?

5 (B) Signup and view all the answers

What is the effect of reducing kV on image quality?

It produces an image of satisfactory quality at a lower image receptor dose (D) Signup and view all the answers

What is the effect of reducing kV on patient dose?

It increases patient dose (B) Signup and view all the answers

How does patient dose (Ki) relate to mAs and kV?

Ki is proportional to mAs and approx to kV2 (C) Signup and view all the answers

How does penetration through the patient relate to kV?

It is proportional to kV3 (A) Signup and view all the answers

How does the total dose to the image receptor depend on kV?

It depends approximately on kV5 (C) Signup and view all the answers

What is the 15% rule in technique selection?

A reduction in kV requires an increase in mAs of at least 15% (B) Signup and view all the answers