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1. MAGNIFICATION
(MACRORADIOGRAPHY/
MICRORADIOGRAPHY)
DISTORTION
PARTHA JYOTI DAS
MSc MIT

2. Contents
 Macroradiography
 Principles
 Magnification with fixed FFD
 Magnification with fixed FOD
 Unsharpness with macroradiography
 Applications
 Microradiography
 Mass miniature radiography
 Distortion
 References

3. The technique of producing an image by direct
magnification is called macroradiography.
Enables fine anatomical details than the original
and accurate diagnosis.
Macroradiograp
hy

4. Principles
 Magnified image can be produced
by increasing the object to film
distance in which the x rays
diverging from the point source
will produce a directly magnified
image.

5. Relation:
 The
relationship
between
size of
object and
it’s image.
FFD
FOD
OFD
Image Size
X-ray Focus
Film
Plane
Object
Plane

6. Principles
 Magnification (M) can be calculated by the
following formula:
focus to film distance (FFD)
focus to object distance(FOD)
. The focus to object distance (or object to film
distance) is taken from the mid level or part.
M =

7. MAGNIFICATION WITH FIXED
FFD
Magnification is increased by bringing the object
nearer to the x ray tube
FOD = FFD/Magnification.
For eg : With a fixed FFD of 100cm, if a
magnification factor of 1.6 is required then;
FOD = 100/1.6 = 62.5 cm

9. MAGNIFICATION WITH FIXED
FOD
 The required magnification is obtained by
moving the film away from the object.
 The required OFD for a given magnification is
then calculated from
OFD = FOD(M – 1)
Eg. FOD is fixed at 100cm , given magnification
factor 1.6
OFD = 100(1.6 – 1) = 60cm

11. UNSHARPNESS WITH
MACRORADIOGRAPHY
Movement
Unsharpness
Geometric
Unsharpness

12. MOVEMENT UNSHARPNESS
 Direct magnification by increased object to
film distance can be carried out if there is
complete immobilization of the patient
 Any movement due to lack of immobilization or
involuntary movement will be magnified on the
radiograph due to increased OFD

13. Movement
unsharpness

14. Some steps
 Use of immobilization devices, e.g. supports,
binders,sandbags and pads.
 Instructions should be given to the patient to
remain still.

15. GEOMETRIC UNSHARPNESS
 Occurs because the source of x rays is not a
point source and any distance between the
object and film will cause an image penumbra
in addition to magnifying the image

16.  The geometrical unsharpness for given focal
spot size calculated by
Focal Spot Size x Object-Film
Distance
Ug =
Focus-Object Distance

17. Geometric unsharpness

18. How to minimize Ug:-
 Focal Spot size:- By reducing Focal Spot
Size.
 Object image Distance:- By reducing object
image distence.
 Focus object Distance:-By increasing the
Focus object distence.

19. Relationship between focal spot
size and magnification
 For a given focal spot size there is a limit to
magnify the image without significant loss of
details.

20. APPLICATIONS
Limited use of macroradiography
 Dacrocystography of Skull (Lacrimal ducts after injection
of contrast)
 Imaging the carpal bones in cases of suspected fracture
of scaphoid
 Localised areas of the lung
 Localised areas during angiography eg: cerebral
angiography

21. Macroradiograph of wrist with a magnification
factor of 2

22. Microradiography
 An imaging technique used to examine
very small objects or minute details, often
with the use of high-voltages, very small
focal spot size, and an ultrafine film
emulsion.

23. Ultrafine Emulsion film
 Photo print made by these films performs rich
sharpness, high definition, strong scratch
resistance, as well as long lasting by pigment

24. Microradiography
 It is also called as chest fluoroscopy.
 The image on a fluorescent screen is
photographed on a small film. Screen and film
are separated and the image is focused on the
film by a camera lens
 Miniature radiographs (70mmx70mm or
100mmx100mm roll or cut films were used).
 A permanent record is possible.

25. Mass Miniature Radiography(MMR)
 In order to control tuberculosis, medical research
council, London appointed their Committee on
Tuberculosis in 1941.
 The detection of symptomless or latent pulmonary
tuberculosis by mass radiography had been the
subject of much careful investigation.
 An excellent instrument was designed by the
council for this purpose and in 1943 the Ministry of
Health announced that a limited number of mobile
miniature radiography sets.

26. The equipment consist of
 Fluorescent screen(emits blue or green light)
 A mirror optics system on recording exposure
on film

27. Survey in progress
Control Panel

28. Apparatus for MMR
1.Power unit:- High tension unit
 Four valve rectification
 An output of from 100 to 400mA
 A maximum kilovoltage of 100 kVp and 91 kVp
respectively

29. 2. X-ray Tube
 The rotating anode X-ray tube
 Dual focus, Focal-spot sizes are 1mm and
2mm square.
 An optical centring device.
 Adjustable diaphragm

30. 3.Fluorescent Screen and Grid:
 16 by 16 inches fluorescent screen
 Covered by a sheet of protective lead glass.
 Yellow-blue or green type of screen
 A stationary grid is also present which
reduces scatter
4.The Camera.:
 An electrically operated camera is linked with the
X-ray exposure switch.
 Lead glass protection is present on the camera side of
screen
5.The lens: a number of different lenses

31. Developing MMR films
 Special tanks meant for roll films on a spiral frame
Development time was 7min at 68 degree F

33. Viewing of MMR FILMS
 Projector for viewing miniature radiographs
Magnifying glasses

34. DISTORTION

35. DISTORTION
 Misrepresentation of the true size and
shape of an object is called distortion.
 Distortion results from unequal
magnification of different parts of the
same object.

36. Foca
l
Spot
Film
•The object AB is
tilted with respect to
the plane of the film.
•The size and shape
of image vary with
the amount of tilting.
Distortion
A
B
A B

37. Distortion of the image of an object will be
different in different parts of the x-ray beam.

38.  Distortion of thick object occurs if they are
not directly in the central part of the x-ray
beam.

39.  When the part to be imaged does not lay parallel
with the IR (cassette).
 If the Central Ray is not perpendicular to the part.

40.  Caused by improper alignment object with relation
to tube focus and film .
 Distortion of an object will be different in different
part of the x-ray beam.

41. Elongated Foreshortened Normal

42.  GOOD RADIOGRAPHS
 MAKES EVERYONE HAPPY

43. REFERENCES
 CHESNEY’S RADIOGRAPHIC IMAGING, 6TH EDITION
 JOHN BALL, TONY PRICE HDCR
 CLARK’S POSITIONING IN RADIOGRAPHY, 12TH
EDITION
 A. Stewart Whitley Charles Sloane Graham Hoadley Adrian D. Moore
Chrissie W. Alsop
.

44. Thank You