This document discusses the techniques of macroradiography and microradiography. It defines macroradiography as producing a magnified image using increased object to film distance. It describes the principles of magnification using fixed focus-film distance or fixed focus-object distance. Unsharpness from movement or geometry is discussed. Applications include skull and wrist radiography. Microradiography uses ultra-fine film and high voltages for small object imaging. Mass miniature radiography was used to screen for tuberculosis using portable fluoroscopic equipment. Distortion can occur if objects are not parallel to the central x-ray beam.

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