Key Features:
- No of Pages: 67
- No of Chapters: 05
Introduction:
Abstract
Film sensitometry has become a valuable tool of determining the sensitometric parameters of films and film-screen performance. But in our locality, there seems to be no accurate data of sensitometric parameters of mammography films. This study compared the sensitometric parameters such as relative speed, maximum density, base plus fog density and average gradient (film contrast) of Begood and Agfa (HDR-C) mammography films.
An experimental research design was adopted and two films Begood and Agfa (HDR-C) were loaded in the same mammography screen cassette and placed in contact with each other on the imaging couch
Series of radiographic exposures were made based on time-scale sensitometry, after which both films were processed in the same automatic processor to avoid day-to-day variations in processing conditions of each film. Density of each exposed step was measured by densitometer and characteristics curves constructed for both films, while sensitometric parameters such as relative speed, average gradient and maximum density were measured after processing without exposure to radiation.
Findings here showed that Agfa (HDR-C) had a relative speed which is 1.2 times faster than Begood, while Begood had a better average gradient of 1.76 than Agfa (HDR-C) which had average gradient of 1.59. The baseplus fog density of Agfa (HDR-C) was 0.17 while Begood was 0.19, but Agfa (HDR-C) had a maximum density of 2.66 while Begood had a maximum density of 2.56. In comparison of sensitometric parameters of both mammography films with other mammography films done use such as Kodak MinR2000 and others, findings showed variations in sensitometric parameters. There was no significant difference between density and net density of Begood and Agfa (HDR-C) mammography films (P<0.05)
Finally, Agfa (HDR-C) had a better sensitometric parameters such as relative speed, maximum density and baseplus fog density than Begood mammography film, but Begood mammography had a better average gradient than Agfa (HDR-C).
Table of Content
Title page - - - - - - - - - i
Approval page - - - - - - - - ii
Certification page - - - - - - - - iii
Dedication - - - - - - - - - iv
Acknowledgement - - - - - - - v
Abstract - - - - - - - - - vi
Table of contents - - - - - - - - vii
List of tables - - - - - - - - ix
List of figures - - - - - - - - x
CHAPTER ONE
INTRODUCTION
1.0 Background of the study - - - - - - 1
1.1 Statement of problem - - - - - - 4
1.2 Specific objectives of the study - - - - - 4
1.3 Purpose of the study - - - - - - 5
1.4 Significance of the study - - - - - - 5
1.5 Scope of the study - - - - - - - 5
1.6 Hypothesis - - - - - - - 5
1.7 Literature review - - - - - - - 6
CHAPTER TWO
2.0 THEORETICAL BACKGROUND
2.1 Definition of terms - - - - - - 14
2.1.1 Time-scale sensitometry - - - - - - 14
2.1.2 Intensity-scale senstometry - - - - - 14
2.1.3 Maximum Density - - - - - - - 14
2.1.4 Baseplus fog Density - - - - - - 14
2.1.5 Speed - - - - - - - - - 15
2.1.6 Average Gradient (G)
2.2 Characteristic curve - - - - - - 15
2.2.1 Use of characteristic curve - - - - - 16
2.2.2 Features of the characteristic curve (sensitometric curve) - 16
2.3 X-ray films - - - - - - - - 20
2.3.1 Two major types of X-ray films - - -- - - 22
2.4 Types of screen and their uses - - - - - 23
CHAPTER THREE
3.0 RESEARCH METHODOLOY
3.1 Research design - -- - - - - - 25
3.2 Mammography films being compared - - - - 25
3.3 Time scale sensitometry - - - - - - 25
3.4 Method of data collection - - - - - 25
3.5 Method of data analysis - - - - - - 25
CHAPTER FOUR
DATA PRESENTATION AND ANALYSIS
CHAPTER FIVE
DISCUSSION, SUMMARY, CONCLUSION, RECOMMENDATION, LIMITATION OF STUDY AND AREA OF FURTHER STUDY
5.0 Discussion - - - - - - - - 43
5.1 Summary of Findings - - - - - - - 45
5.2 Conclusion - - - - - - - - 46
5.3 Recommendation - - - - - - - 46
5.4 Limitation of the Study - - - - - - 46
5.5 Area of Further Study - - - - - - 46
References - - - - - - - - - 47
Appendix - - - - - - - - - 52
LIST OF TABLES
Table 1: Exposure factors used for both mammography films 30
Table 2: Distribution of densities and log relative exposure values of Begood mammography film 31
Table 3: Distribution of densities and log relative exposure values of Agfa (HDR-C)mammography film 33
Table 4: Net density and log relative exposure value of both mammography films 35
Table 5: Sensitometric parameters of Begood and Agfa (HDR-C) 37
Table 6: Result of sensitometric indices of Kodak minR 2000 mammography at varied temperature (0C) 38
Table 7: Result of sensitometric indices of Kodak minR 2000 mammography at varied development times 39
Table 8: Result of sensitometric evaluation of eight mammography films included in this study 40
Table 9: Result of two-tailed test comparison of density of both mammography films 41
Table 10: Result of two-tailed test comparison of net density of both mammography films 42
LIST OF FIGURES
Figure 1: Cross-section of duplitized film 22
Figure 2: Characteristic curve of density over log relative exposure of Begood mammography film 32
Figure 3: Characteristic curve of density over log relative exposure of Agfa (HDR-C) mammography film 34
Figure 4: Characteristic curve of both net density of Begood and Agfa (HDR-C) over log relative exposure value 36
Introduction
The main concern in mammography screening is the detection of features characteristic of breast disease. These features often have sizes of the order of 1mm and differ from the normal tissue only slightly in composition, thus setting high requirements for the resolution and contrast that an imaging system must offer in order to be appropriate for mammography1.On the other hand, given the high radiosensitivity of breast and large number of women examined many times during their life, it is evident that doses during mammography should be kept as low as possible.
While digital mammography may look promising, the vast majority of mammography examinations are still carried out with screen-film systems. In recent years, most film manufacturers have presented new films and intensifying screens for mammography that reduce the dose to the breast and produce the image quality required to maintain the diagnostic sensitivity and specificity of mammography at high levels.
During film coating, constant thickness of emulsion is applied over entire area of film base, due to difference in thickness would result in density variation in final image, because sensitivity of an emulsion depends partly on its coating thickness and emulsion, but sensitivity involves response of film/film-screen system to exposure to form image density. Wavelength of electromagnetic radiations are usually absorbed by the emulsion and behavior of emulsion in this respect is known as spectral response and which of course is a critical feature of film emulsion.
Mammography films serves as an image recording medium and mammography is a very tasking procedure in which change in film design and screen design can have a significant effect on image quality, which of course has promoted research for use of better films and screens for mammography.
In radiography, it is essential to evaluate and compare the performance of one film or film-screen system against another and need to define various aspects of image being examined and performance of film is tested by subjecting it to a range of different exposures and examining the radiographic densities which results by use of densitometer.
Film characteristics can be determined and monitored for changes due to processing by sensitomety. Since it has been noted that processing conditions such as chemicals, temperature and processing time affect image quality. Inappropriate chemicals or a developing temperature lower than recommended may result in unacceptable mammograms and this is why some films have been modified to be less dependent on processing conditions.
Furthermore, processor design also affects the sensitivity of films, due to the fact that new processors have option of not only varying the developer temperature, but also the processing cycle thus changing the developing time and chemicals.
Manufacturers often make films according to their own specifications and usually introduce new films with special properties during manufacturing such as addition of much or less silver halide grains, which of course determine film sensitivity, contrast and density. Due to variation in film design by manufacturers.It tends to results in variation in film quality and performance coupled with spectral response to exposure.
Finally, screen-film characteristics can be determined and monitored using an appropriate quality control (QC) phantom, or by film sensitometry with which changes in film quality due to processing or other reasons can be identified. One of the parameters routinely monitored with the quality control phantom is the background or reference optical density (OD) of the mammographic images. Apart from the personal preferences of radiologists, it has been shown that for a given screen-film combination, subtle details and small contrast differences are best stressed when the film optical density is within a certain range and varies from one film/film-screen system to another. For this reason, it has been recommended that each institution should determine the optimum sensitometric parameters such as speed and optical density (OD) for film/film-screen combination being used and processing conditions specific to it.
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