|Year : 2011 | Volume
| Issue : 1 | Page : 18-20
Optimization of sensitometric properties of blue and green light sensitive dental radiographic films employing an automatic processor
Suchetha N Malleshi, Karthikeya Patil, Mahima V Guledgud
Department of Oral Medicine and Radiology, JSS Dental College and Hospital, JSS University, Mysore, India
|Date of Web Publication||29-Jul-2013|
Department of Oral Medicine and Radiology, JSS Dental College and Hospital, JSS University, Mysore-15
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: Accurate film processing is of paramount importance in acquiring a good diagnostic radiograph. Radiographic films show variations in densities and contrast, with changes in processing conditions, and also film type, all of which are interdependent. Therefore, this research was conducted to recognize the effect of time and temperature variations of automatic processor on the sensitometric properties of blue and green light sensitive screen films. The study also aimed to note the effect on sensitometric properties when mismatch occurred when using between the screen and film belonging to different manufacturers. Materials and Methods: Sixty green light sensitive and 60 blue light sensitive spectrally matched screen film combinations were used in the study. However, the films and the intensifying screens employed belonged to different manufacturers. These films were exposed to five different exposure times and subsequently processed in an automatic processor, using two different protocols. Initially, at constant processing time of 2.5 min, five different processing temperatures were employed. Later, maintaining constant processing temperature of 35°C and five different processing times were engaged. Density, contrast and speed were calculated, using H and D curve. Results: Results revealed increasing density, contrast and speed values with increasing processing times and temperatures of both green and blue sensitive films. Conclusion: This investigation clearly establishes the possibility of obtaining optimal sensitometric properties, despite using intensifying screens and films of different manufacturers, if spectral match is ensured.
Keywords: Image quality, radiography, screen-film systems, technology, X-ray
|How to cite this article:|
Malleshi SN, Patil K, Guledgud MV. Optimization of sensitometric properties of blue and green light sensitive dental radiographic films employing an automatic processor. J Int Clin Dent Res Organ 2011;3:18-20
|How to cite this URL:|
Malleshi SN, Patil K, Guledgud MV. Optimization of sensitometric properties of blue and green light sensitive dental radiographic films employing an automatic processor. J Int Clin Dent Res Organ [serial online] 2011 [cited 2019 Dec 5];3:18-20. Available from: http://www.jicdro.org/text.asp?2011/3/1/18/115768
| Introduction|| |
Ideal diagnostic radiograph is interplay of innumerable factors. Of all the properties that influence image characteristic's pivotal role is played by density, contrast and speed. , Literature is replete with data implying faulty processing as one of the prime reasons for repeating a radiograph. , Frequently, radiologists modify the settings of an automatic processor without comprehending the consequences. Recognizing the influence of processing on the final outcome of a radiograph is fundamental, and this can be efficiently monitored by sensitometry. 
This investigation, basically aimed at analysing the effects of time and temperature changes of automatic processor on sensitometric properties of blue and green light sensitive radiographic screen films. Since the intensifying screens and radiographic films employed belonged to different manufacturers, this research concomitantly evaluated the effect of this mismatch on the sensitometric properties; which is conceptually unique. Despite the fact that radiographs are digitized now-a-days, physically processing of the radiographic films is still prevalent. An extensive literature search revealed scanty data on these concepts, which further prompted us to investigate this concept.
| Materials and Methods|| |
This in-vitro research incorporated analysis of 60 5" × 6" blue light sensitive screen XBT films (Eastman Kodak Co, Rochester, NY) with 5" × 7" cassette affixed with blue light emitting intensifying screens (Conventional, Kiran, India; 400 speed) and 60 5" × 6" green light sensitive screen TMX films (Eastman Kodak Co, Rochester, NY) and 5" × 7" cassette with green light emitting intensifying screens (Rare Earth, Kiran, India; 400 speed). Accurately calibrated panoramic X-ray machine (Orthoslice 1000 C, Trophy, France) comprising cephalostat and an option for skull radiograph was operated at 80 kVp and 10 mA and at fixed distance of 60 inches throughout the study.
Of the 60 films, 50 each were exposed to radiation and the rest ten each were left unexposed to analyse the base and fog density. Initially, 50 of the 60 XBT were grouped into ten groups, each containing five films. Five different exposure times of 0.25 s, 0.50 s, 1.00 s, 1.60 s and 2.00 s were applied. In each group, the first film was subjected to 0.25 s of exposure and subsequently the next 4 to 0.50 s, 1.00 s, 1.60 s,2.00 s of exposure. To each of these groups one unexposed XBT film was added to estimate base plus fog value. Identical procedure was pursued with TMX film-screen combination. This exposure procedure was repeated for all the ten groups.
Promax 5 speed automatic processor (Chayagraphics Pvt. Ltd., Bengaluru, India) for screen radiographic films, equipped with self-replenishing facility was utilized with Kodak X-Omat automatic film processing solutions. Two constantly monitored processing setups were adapted. Initially, at a constant processing time of 2.25 min, processing temperatures of 28°C, 30°C, 32°C, 35°C and 37°C were used. Later, at constant processing temperature of 35°C, processing time settings of 1.5, 1.75, 2.25, 2.78 and 3.33 min were sequentially applied.
Optical density (OD) was recorded using at five places (four corners and centre, and mean calculated) using a transmission densitometer with 2 mm aperture (Optel Trans-4V transmission densitometer, Mumbai, India). All film densities were recorded above base plus fog and H and D curve was plotted. Contrast was obtained by dividing the difference between density 2.5 and density 0.5 by the difference between log (10) relative exposure at those densities. Speed was calculated as the reciprocal of the exposure required to yield a density of 1.00 above base plus fog. The data was statistically analysed using repeated measure ANOVA and Paired t-test analysis (SPSS for windows version 16).
| Results|| |
At both the processing protocols, the base plus fog, OD, contrast and speed values generally increased with increasing processing temperatures and times, in accordance with studies by Thunthy et al. and Kircos et al., However, at the higher end of the processing spectrum the sensitometric properties displayed properties which did not confine within the acceptable limits. The contrast curves are plotted in [Figure 1]and [Figure 2] and speed data is assayed in [Figure 3] and [Figure 4].
|Figure 1: Contrast of blue screen and green screen fi lms at fi xed processing time of 2.25 min and varying temperatures|
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|Figure 2: Contrast of blue screen and green screen fi lms at fi xed processing temperature of 35oC and varying processing times|
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|Figure 3: Speed of blue screen and green screen fi lms at fi xed processing time of 2.25 mins and varying temperatures|
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|Figure 4: Speed of blue screen and green screen fi lms at fi xed processing temperature of 35oC and varying processing times|
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Paired samples t test showed statistically significant values (P = 0.000) at each variation of processing time and temperature for both films.
| Discussion|| |
At constant processing time of 2.25 min and varying processing temperatures: The base plus fog density values of both the films exhibited a gradual increase with increasing processing temperatures, in accordance with Thunthy et al. and Kircos et al., However, only XBT film, at 37°C processing temperature, displayed base plus fog density above permissible range of 0.15-0.3. ,
Akin to findings by Thunthy et al., this study yielded increasing OD, contrast and speed values, with increasing processing temperatures.  Only, XBT film at processing temperature of 37°C (subsequent to 2 s exposure), displayed elevated OD. TMX films, at all the processing temperatures employed exhibited OD within the admissible range of 0.6-3.0. ,
The contrast values, for XBT films at all processing temperatures were acceptable, in comparison to TMX films where ideal contrast was obtained only at 32°C, 35°C and 37°C. Speed, for both films at 35°C and 37°C did not demonstrate any significant difference.
At constant processing temperature of 35°C and varying processing times: The base plus fog value, OD, contrast and speed of both the films showed a gradual increase with corresponding increase in processing times, in consensus with Thunthy et al. Only XBT film, at processing time of 3.33 min yielded undesirable base plus fog density value.
On processing XBT film, at 2.78 min (after exposure time of 2 s) and at 3.33 min (following exposure time of 1.6 and 2.0 s) OD values were unsuitably elevated. This could be attributed to amalgamation of longer exposure and processing parameters. In comparison, TMX films displayed ideal OD values all along.
Contrast value for XBT film at 3.33 min of processing increased substantially. For TMX film, at 1.5 min processing low and at 3.33 min high contrast value was recorded. Speed, for both films at 2.78 and 3.33 min of processing was almost similar. Factually, speed, which increases with increasing processing time, fails to increase after a certain limit.  Similar effect was observed in this study as well.
Although both rare earth and calcium tungstate screens demonstrate significant energy dependency; speed increases with beam energy, this effect is more marked for rare earth screens.  It must be emphasized that, though rare earth and related screens are approximately 5 times faster than calcium tungstate screens but demonstrate a drawback of decreased resolution. ,
| Conclusion|| |
In conclusion, this investigation reinforces the fact that, as the exposure time, processing time and processing temperature increase sensitometric properties also increase. Analyzing the cumulative effect of density, speed and contrast obtained on pursuing this research protocol; at 2.25 min processing time, for XBT films processing temperatures of 28-35°C and for TMX films processing temperatures of 32-35°C can be employed. Similarly, at processing temperature of 35°C; processing time of 1.5-2.78 min for XBT films and 1.75-2.78 min for TMX films can be adapted. This investigation also establishes possibility of obtaining optimal sensitometric properties, despite using intensifying screens and films of different manufacturers, if spectral match is ensured. In conclusion, when manufacturer's recommendation cannot be adhered to, optimal sensitometric properties are nevertheless achievable by orchestrated processing parameters. Notwithstanding the constraints and scale of the study, it has nonetheless emphasized the need for further in vivo studies with subject factors contributing to the analysis.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]