Dry Film Technology Swastik

Presented in department of radiology
Maharajgunj Medical Campus
Institute Of Medicine

1. Swastik sagar poudel MMC IOM DRY FILM TECHNOLOGY

2. DRY FILM Dry film is classified as “Long-Term film” according to ANSI definition: “ Dry film is a photographic film that is suitable for the preservation of records for a minimum of 100 years when stored under archival conditions, providing the original images are of suitable quality” As a consequence the Dry film stored at 25°C can be archived for more than 100 years

3. Contd..... Archival quality refers to the film performance of the radiograph : the image does not deteriorate with age but remains in its original state. Dry film thickness; Thickness of a coating measured over the substrate. T his can consist of a single or multiple layers .

4. Dry film features S ilver based photo thermographic technology. Low silver content less than 0.2 gm/ sq m 810 nm IR laser diode sensitivity. 0.18 polyester based blue or clear. Continuous tone image capability

5. Early laser imagers Introduce in 1984 Initially single modality connection. Electronic images easy to manipulate. Hence multi-format options greater. Multiple image of same image set possible. Wet processing with docked processor or remote processor- silver halide film technology . Multiple modality connect soon followed with up to 16 users per laser Printer interconnect followed over proprietary network.

6. Laser Imaging Began in multi-format camera ,known as early laser imaging. Current technology in laser imaging

7. Advantages of using laser imager Images can be placed in any preferred position in the film . C hoice of positive or negative images. The unit can be controlled remotely. Choice of black or clear borders to the film. The imager is self monitoring so any equipment fault can be identified and corrected quickly.

8. Multi-format camera Involves optical process taking a photograph of a CRT and capturing image on film matched to CRT phosphor spectral emission. Multi format of images formed by moving film or lens or CRT . Different magnification of images done by altering distance between film and lens- massive cabinets. Could only connect to one modality. Suffer from dust, vibrations, CRT drift. Needed much more intervention- cassette changes

9. DIGITAL OUTPUT DEVICES CRT(CATHODE RAY TUBE) A CRT is a vacuum tube that is used as a display screen in a computer or video display terminal (VDT) . LCD&LEDs Flat panel display (liquid crystal display (LCD))are thinner and lighter and consume less power than CRT.

10. CONSTRUCTION OF DRY FILM High quality silver based photographic material. The light/heat sensitive material consists of silver halide and silver behenate crystals .

11. DRY PROCESSING Dry processing refers to the development of images without the use of wet chemistry . ADVANTAGES No dark room required(space saved). No plumbing required. Less environmental impact . Reduced capital cost. Reduced operating cost .

12. Contd …………… Although dry processing can be performed through several approaches ,two technologies prevail at this time . PHOTOTHERMOGRAPHY(PTG) THERMOGRAPHY(TG) Photo thermography and thermography are the image processing method that do not require chemistry and all attendant requirements of the chemistry.

13. Concept of Photothermography The photothermographic imaging process uses light (infrared laser radiation) to create a “latent image”. Uses low power modulated laser beam to record the image signal on the film ,thereby generating the latent image. The latent image so formed on the sensitized silver halide emulsion is subsequently developed by thermal process at 25 C that takes approx.15sec so called DWELL TIME

14. Contd..... The “latent image” is revealed by means of a dry thermal process. After thermal processing the image becomes visible due to a modulated density of black metallic silver particles.

15. Latent Image formation

16. The photothermographic process starts with the formation of latent image . A latent image is an invisible image produced by the exposure to light of a photosensitive material such as photographic film. The laser beam releases the photon into sensitive layer . Photons converts silver ions[Ag + ] into metallic silver[Ag ].

17. Thermal Process After exposure , the dry film absorbs thermal energy from rotating drum whose temperature ranges from 120 to 140 C for 15 sec. The thermal energ y acts on the latent image site to develop by the catalyt process, silver atoms on the neighbouring silver behenate crystals thus forming the visible silver grain.

18. Very expensive and complex printer hardware. High media cost. Low productivity of < 55 film/hr.

19. Thermography (TG) Thermography uses a modulated thermal print head that converts electrical energy into heat using resistive elements . No latent image is produced as the organic silver salts are deveoped directly by heat.

20. Direct Thermal Process

21. It is a single-stage process with black and white densities created by a thermal print head. In thermal print head technology, tiny heaters produce images. Digital signals from various modalities are processed and converted into electrical pulses. These are then transferred to a thermal print head, whose microscopic heat resistor elements convert electrical energy into heat energy. A thermal sensitive film passes close to the print head, with transfer of heat from each element. A chemical reaction results and a pixel is developed. Different shades of gray of a modality image generate varying strengths of electrical signals. The outcome of this modulation of electrical signals leads to corresponding changes in the gray level of the print images.

22. Transport & Storage of unexposed film Stored in cool ,dry dark place and protected from all types of radiation. Temperature must be less than 24 C. Relative humidity :30-60% Unexposed film can withstand short term temperature spikes[35 C for 24 hrs]. Temperature above 35 C will gradually detoriate shelf – life.

23. Image stability Proved through 2 severe tests: (1) ANSI IT9.1-1988 (2) Arrhenius test

24. ANSI IT9.1-1988 An unexposed processed film is incubated in conditioning air oven at the following conditions : The change density of the incubated film shall be no greater than 0.05 density units.

25. Arrhenius test: Most accepted method of estimating the long term stability of an imaged film. Based upon incubation of exposed and processed film. At different temperatures and times varying from a few hours to many weeks. A failure point is determined. Failure point is the time required to produce a density change of 0.20 optical units in the mid density range.

26. Image stability Humidity has no significant effect on developed dry film. Prolonged exposure to the intense light and excessive heat 54 C for more than 3 hrs may cause gradual darkening of the image and discoloration. Not recommended :- Leaving films in vehicles in hot climate . Leaving films in a light box exceptionally hot 50 C for more than 8 hrs . Cleaning the dry film with alcohol or cleaning agents. Using dry films for slide projector.

27. Printing in a dry laser camera A typical print sequence in Carestream/Kodak laser camera is outlined in the figure. A suction cup lifts a single film out of supply cartridge and feeds it into vertical transport rollers. Film moves to a film platen (flat glass pane) which is the exposure area. Platen holds the film while the scanner writes the image onto the film. Film is transported over a processor drum, wherein the heat develops the film. Film transport rollers move the exposed film through densitometer to a sorter and out to bins or alternatively placed at the top hood

28. Printing in a direct thermal print camera A vacuum pump lifts a single film from a supply cartridge, at the pickup unit. The film is fed into rollers driven by a gearbox module. The rollers move the film between thermal print head and a drum which are in close apposition [Figure 5]. The heat generated by a thermal print head develops the film. Output rollers send the developed film to the sorter bin.

29. Dry v/s conventional Film material: Dry film contains silver behenate emulsion layer as wet film contains silver halide crystals layer to produce visible image. Objective image quality: Dry film demonstrates a range of OD from a base fog of 0.24 to a maximum density of 3.34 as wet film demonstrates a range from 0.12 to 3.62. Dry film eliminates the need for fluid chemistry and waste materials as in conventional film.

30. Contd.. When the films were exposed between 40 c to 100 c ,dry film showed gray scale degradation at a temperature above 70 c the wet film did not show gray scale degradation. At 100 c, whole film sample turned black.

31. THANK YOU !!! !