Stereography 1234.pptx

for DXRT , BMRIT and MMRIT student

1. JAI HIND Stereography Virendra k M aurya

2. Index History Stereography Procedure Viewing, Stereoscopes, Advantage & disadvantage

3. History J. MacKenzie Davidson introduced stereoscopy to radiology in 1898, and it won immediate and widespread acceptance. Stereoscopy grew in popularity, and by 1930 most radiographs were taken stereoscopically. Its popularity from a statement made by Jarre and Teschendorf in 1933.

4. History Stereoscopic techniques were used widely by the Royal Air Force in World War II , owing to their ability to provide greater detail to imagery analysts. 19th and 20th centuries. (a particular period of 100 years that is used for giving dates) We live in the 21st century [the period between the year 2000 and 2099]

5. Stereography Stereoscopy refers to a viewing modality in which binocular vision allows appreciation of the three dimensionality of an object . Stereoscopic vision is an inherent part of the human visual system, enabling perception of depth that is independent of cues such as relative size and motion parallax .

6. In this way, more information can be conveyed than is possible with virtual three-dimensional (3D) models , simulated by perspective and shading, and more again than by two dimensional planar images. It is this possibility of achieving a richer data display and the associated chance of improvements in speed and accuracy of diagnosis that prompts this study.

7. Procedure Stereoscopic filming techniques are simple and require no special equipment . Two films are exposed, one for each eye. Between exposures, the x-ray tube is shifted 10% of the target-film distance (6°); the films are changed, taking care to position the second film in exactly the same position as the first film . The films of the stereoscopic pair present the eye with slightly different, or discrepant, images .

8. Monocular Depth Perception- . Size - Near objects are larger than distant objects. Overlapping Contours- Near objects overlap distant objects. Perspective- The objects from a particular vantage point, Perspective. By following lines and contours we gain a sense of depth.

9. Shading. A sphere has the contour of a circle , but with proper shading we perceive its true shape. Air Haze. Water vapor, dust, and smoke in the atmosphere absorb and reflect light, casting a veil over distant objects and causing them to appear farther away and less sharp .

10. Stereopsis Binocular depth perception, called " stereopsis ," is a unique characteristic of man and other primates. It is dependent on the brain 's ability to receive slightly different images from each eye , discrepant images, and then to fuse them into a single image that has depth. Discrepant images are the heart of stereopsis , and fusion occurs in the brain. The degree of discrepancy is of vital importance.

11. Accommodation and Convergence. Relative and Absolute Depth Perception.

12. Parallax Parallax is the apparent displacement of an object when viewed from two different vantage points.

13. parallax

14. STEREOSCOPIC FILMING Stereoscopic filming techniques are simple, and usually require no special equipment . Two films are exposed , one for each eye . the relationship between the x-ray tube, patient, and film. The film is changed between exposures . The second film should be placed in exactly the same position as the first film . The tube is shifted from the left to the right eye position between exposures , and it is the only part that moves. Usually the film is placed in a Bucky tray under the grid so that it can be changed without disturbing the patient. If the examination does not require a grid , the film is placed in a flat box with an open end (stereo tunnel ),

15. Magnitude of Tube Shift Direction of Tube Shift

16. TUBE SHIFT

17. STEREOSCOPIC VIEWING The first step is to identify the tube side of the film , that is, the side that is closer to the patient and thus facing the x-ray tube during the exposure. The next step is to determine the direction of the x-ray tube shift. The last preliminary step is to determine which film is to be viewed by the left eye, and which by the right eye .

18. TUBE SHIFTING

19. Viewing Systems Stereopsis , or binocular depth perception, is only qualitative. With stereoscopic radio graphs we are incapable of judging the absolute distance between objects.

20. All we can appreciate is which of two objects is closer to us (i.e., a rank order type of depth perception). All we need for stereopsis are discrepant images, and the degree of discrepancy must be sufficiently great to permit an appreciation of depth , and yet not so great that the brain cannot fuse the images .

21. The same stereoscope can be used to interpret all stereoscopic films , no matter what distance was used for the exposure.

22. Cross-Eyed Stereoscopy. Both eyes are focused at a single area of interest, Accommodation and convergence are coordinated , And both eyes see identical structures in sharp focus. Two films are interpreted at the same time.

23. Wheatstone Stereoscope. The Wheatstone stereoscope will be used to illustrate how they function. With a Wheatstone unit, convergence is assisted by a pair of mirrors that are located halfway between the films.

24. Prism stereoscope A stereoscope designed by Caldwell in 1906. It consists of a pair of prisms mounted into binoculars. The unit is compact and convenient to use. Gass and Hatchett have described a similar system, in which they mounted a pair of thin prisms into eye glasses.

25. Simple mirror stereoscope The simplest stereoscope, described by Kerekes , requires only a small pocket mirror and a steady hand.

26. Advantage Education . The teaching of normal anatomy is simplified with stereoscopic images. Foreign Body Localization- Stereoscopy is superior for the localization of many foreign bodies, such as multiple pellets from a shotgun wound . Localization of Intracranial Calcifications - on the lateral views, Unimposing Confusing Shadows - The more confusing a radiograph is, the more likely stereoscopy is to be helpful, For eg - a collection of gas in the colon

27. Disadvantage Expense- Stereoscopy requires two films, which adds to the cost of an examination. Patient Exposure- use the two film for interpretation Need the practice- stereoscopist require the more practice for good interpretation.

28. References Stewart N, Lock G, Hopcraft A, Kanesarajah J, Coucher J. Stereoscopy in diagnostic radiology and procedure planning: does stereoscopic assessment of volume-rendered CT angiograms lead to more accurate characterisation of cerebral aneurysms compared with traditional monoscopic viewing?.  J Med Imaging Radiat Oncol . 2014;58(2):172-182. doi:10.1111/1754-9485.12146 Stereoscopic Imaging [Internet]. SlideShare . 2014 [cited 2024 Jan 26]. Available from: https://www.slideshare.net/punjabimunda17/stereoscopic-imaging christensen,s radiation physics