The document discusses various geometric factors that impact image quality in radiography, including magnification, distortion, and focal spot blur. It explains that magnification causes images to appear larger than the actual object and is determined by the ratio of the source-to-image distance to the source-to-object distance. The document provides examples of calculating magnification factors for different source-to-image and source-to-object distances and using the magnification factor to determine the actual size of an object based on its imaged size.

1. FUNDAMENTAL
S OF IMAGING
RAD 206
Geometric factors

3. 15.1: Optimization of protection in radiography: technical aspects
3
IMAGE QUALITY
CHARACTERISTICS
Density
Contrast
Resolution
Unsharpness
Noise
Distortion & Magnification
MTF
Distortion Bushong Ch 10 pg 173

4. Which car is the biggest

6. WHICH ONE IS AN EGG

9. To produce high quality radiographs, the technologist must
maximize the geometric factors
Geometric Factors
• Magnification
• Distortion
• Focal-Spot Blur

10. DISTORTION
Misrepresentation of the true
SizeSize or ShapeShape or PositionPosition of an
object
• size distortion is only Magnification
• shape distortion is True Distortion
Why ?? Because Shape distortion is just unequal magnification of
different proportion of the same object

11. MAGNIFICATION
(SIZE DISTORTION)
TRUE
DISTORTION
(SHAPE DISTORTION)
Magnification is a type of distortion
Every pixel or area is equally
Magnified
True Distortion is unequal
Magnification of areas
DISTORTION

14. MAGNIFICATION
Why magnification
happens
As the X-ray beam diverges,
the image produced on the
film is always slightly
larger than the original
image, and this effect is
called magnification.

15.  All images on the radiograph are Larger than the
actual object
 For almost ALL Radiographic Exams , minimizing
magnification is required ..by:
 Reducing OID
 Increasing SID
 Minimizing Magnification also improves Detail

16. The position of the tube
to IR (SID) will influence
how the structures
appear on the image
The farther away
the less magnified
SID Magnification

18. THE MAGNIFICATION
FACTOR “M“
is the degree or ratio of magnification , and is
calculated by:
M = SID/SODM = SID/SOD

19. PRACTICE
If the SID is 100 cm and the SOD is 80 cm,
what is the magnification factor?
If the SID is 115 cm and the SOD is 80cm,
what is the magnification factor?
If the SID is 115 cm and the SOD is 95cm,
what is the magnification factor?
If the SID is 100 cm and the SOD is 95 cm,
what is the magnification factor?
If the SID is 115 cm and the SOD is
110cm, what is the magnification factor?
1.25
1.44
1.21
1.053
1.045

20. The magnification factor allows for the
calculation of the actual size of an object
from the image by using this formula:
O = IO = I // MM
O = object size
I = image size
M = magnification factor
the value of M can be substituted by
M = SID/SOD
O = I / (SID/SOD)

21. PRACTICE
QUESTIONS
A child brought for a chest x-ray
who said that he swallowed 100
fills coin, SID used was 115 cm
and the estimated S0D is 105cm,
how big the image would be?
2.6mm
A child brought for abdomen x-ray
who said that he swallowed 100 fills,
SID used was 100 cm and the
estimated OID is 8cm, the image on x-
ray shows a 2.4 mm, is he saying the
truth ?
Yes,
two 50 fills coins
stuck together

22. PRACTICE
QUESTIONS
Two erect chest x-ray were
done using AP and PA
techniques,
Estimate distance between
the heart and the back
surface of the patient..
Note:
Direct exposure on film, No
Bucky was used,
SID for erect CXR is 180cm