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X-rays production
X-rays are produced in an X-ray tube when high-speed electrons strike a heavy metal like tungsten (Perry, 1993). The process of X-rays production is very inefficient. For X-ray tubes operated at conventional voltages, only 1% of the energy released at the impact of electrons is in the form of X-rays, whereas 99% is released in the form of heat (Lavin, 2007). When high speed electrons strike a heavy metal (target), X-rays are produced by two atomic processes, which are radiative and collisional interactions (Thrall and Widmer, 2007).
In collisional interaction (K-shell emission), the oncoming high speed electron from the cathode ejects an orbital electron from the K-shell of the target atom (Thrall and Widmer, 2007). A more peripheral (outer shell) electron from the higher energy level or a free electron will fill the void in the inner shell (Thrall and Widmer, 2007). The difference in the energy level is emitted as characteristic X-ray (Hendee and Russell Ritenour, 2002). The ejected electron and the oncoming electron from the cathode may produce additional collisional or radiative interactions, but the X-ray photons produced are of low energy and not useful for diagnostic imaging (Thrall and Widmer, 2007).
Theoretically, any shell could contribute to collisional interaction. However, in practice, transition of electrons among shells beyond M-shell produce only low energy X-rays, visible light and ultraviolet light (Hendee and Russell Ritenour, 2002). These low energy X-rays are removed by inherent filtration and do not become part of the useful beam (Hendee and Russell Ritenour, 2002).
The characteristic X-rays produced by a target are usually dominated by one or two peaks with specific energies slightly less than the binding energy of the K-shell electrons (Hendee and Russell Ritenour, 2002). This is due to the fact that the most likely transition involves an L-shell electron dropping to fill a vacancy in the K-shell. This transition produces a characteristic X-ray photon, which is equal to the difference in electron binding energies of the K- and Lshells Hendee and Russell Ritenour, 2002). A characteristic X-ray photon with an energy equal to the binding energy of the K-shell alone is produced only when the vacancy in a K-shell is filled with a free electron from outside the atom and the probability of this event is very small (Hendee and Russell Ritenour, 2002). A characteristic X-ray released during transition of an electron between adjacent shells is known as X-ray e.g. K, whereas an Xray produced by transition involving non-adjacent shells is known as X-ray e.g. K (Hendee and Russell Ritenour, 2002).
In radiative (braking or bremsstrahlung) interaction, the oncoming high speed electron from the cathode is attracted by a positively charged nucleus of the target atom (Thrall and Widmer, 2007). It slows and bends around the nucleus of the target atom releasing X-ray photons. The oncoming electron may produce additional X-ray photons through radiative or collisional interactions (Thrall and Widmer, 2007). X-rays produced by collisional interactions account for only a small fraction of the total X-rays produced in an X-ray tube. When a peak kilovoltage (kVp) of 80−100 is applied across the X-ray tube, about 90% of the emitted X-rays are bremsstrahlung radiation and 10% are characteristic radiation (Perry, 1993).
CHAPTER ONE: GENERAL INTRODUCTION
1.1 Introduction
1.2 Hypothesis
1.3 Objectives
1.4 References
CHAPTER TWO: LITERATURE REVIEW
2.1 Red panda
2.2 Ring-tailed lemur
2.3 Radiography
2.4 Ultrasonography
2.5 References
CHAPTER THREE: THORACIC LIMB MORPHOLOGY OF THE RING-TAILED LEMUR (LEMUR CATTA) EVIDENCED BY GROSS OSTEOLOGY AND RADIOGRAPHY
3.1 Introduction
3.2 Materials and methods
3.3 Results
3.4 Discussion
3.5 Acknowledgements
3.6 References
3.7 Tables
3.8 Figures
CHAPTER FOUR: MORPHOLOGY OF THE PELVIS AND HIND LIMB OF THE RING-TAILED LEMUR (LEMUR CATTA) EVIDENCED BY GROSS OSTEOLOGY, RADIOGRAPHY AND
COMPUTED TOMOGRAPHY
4.1 Introduction
4.2 Materials and methods
4.3 Results
4.4 Discussion
4.5 Acknowledgements
4.6 References
4.7 Tables
4.8 Figures
CHAPTER FIVE: RADIOGRAPHIC THORACIC ANATOMY OF THE RING-TAILED LEMUR (LEMUR CATTA)
5.1 Introduction
5.2 Materials and methods
5.3 Results
5.4 Discussion
5.5 Acknowledgements
5.6 References
5.7 Tables
5.8 Figures
CHAPTER SIX: RADIOGRAPHIC AND ULTRASONOGRAPHIC ABDOMINAL ANATOMY IN CAPTIVE RING-TAILED LEMURS (LEMUR CATTA)
6.1 Introduction
6.2 Materials and methods
6.3 Results
6.4 Discussion
6.5 Acknowledgements
6.6 References
6.7 Table
6.8 Figures
CHAPTER SEVEN: THORACIC LIMB MORPHOLOGY OF THE RED PANDA (AILURUS FULGENS) EVIDENCED BY GROSS OSTEOLOGY AND RADIOGRAPHY
CHAPTER EIGHT: MORPHOLOGY OF THE PELVIS AND HIND LIMB OF THE RED PANDA (AILURUS FULGENS) EVIDENCED BY GROSS OSTEOLOGY, RADIOGRAPHY AND COMPUTED TOMOGRAPHY
CHAPTER NINE: RADIOGRAPHIC THORACIC ANATOMY OF THE RED PANDA (AILURUS FULGENS)
CHAPTER TEN: RADIOGRAPHIC AND ULTRASONOGRAPHIC ABDOMINAL ANATOMY IN CAPTIVE RED PANDAS (AILURUS FULGENS)
CHAPTER ELEVEN: GENERAL DISCUSSION AND CONCLUSIONS
11.2 References
