[An Experiment into the Effects of FFD on Radiation Dose when using an Automatic Exposure Chamber]

by

ACKNOWLEDGEMENT

I would take this opportunity to thank my research supervisor, family and friends for their support and guidance without which this research would not have been possible.

DECLARATION

I, [type your full first names and surname here], declare that the contents of this dissertation/thesis represent my own unaided work, and that the dissertation/thesis has not previously been submitted for academic examination towards any qualification. Furthermore, it represents my own opinions and not necessarily those of the University.

Signed __________________ Date _________________

TABLE OF CONTENTS

ACKNOWLEDGEMENTII

DECLARATIONIII

CHAPTER 1: INTRODUCTION1

Differences between SDCT and MDCT3

Aim of the Study4

CHAPTER 2: LITERATURE REVIEW5

X-Rays5

X-Rays And Pregnancy6

Acute Health Effects6

Radiation7

History11

Health Effects12

CHAPTER 3: METHODOLOGY14

CHAPTER 4: RESULTS22

Responsibilities for patient dose management22

What are the responsibilities of manufacturers?23

Operator Choices That Affect Patient Dose24

General descriptors of image quality25

Different imaging tasks require different level of quality26

Equipment and protocol issues affecting patient dose28

Overbeaming28

Overranging29

CHAPTER 5: DISCUSSION31

Tube current (mA) and tube current-time product (mAs)31

Angular (x,y)33

Longitudinal (z)34

Combined Angular and Longitudinal (x,y,z)35

Image quality selection paradigms35

Assumptions regarding optimal noise levels37

Temporal mA modulation38

Tube potential (kVp)38

CHAPTER 6: CONCLUSION40

REFERENCES44

CHAPTER 1: INTRODUCTION

Atrial fibrillation (AF) is the most common clinically significant cardiac arrhythmia; it carries significant morbidity and mortality, and directs the allocation of sizeable health care resources. According to the current ACCF/AHA/HRS guidelines for AF management,2 catheter ablation is increasingly used as a therapeutic approach in patients with symptomatic drug-refractory AF.

Atrial fibrillation catheter ablation has undergone considerable technical evolution over the past decade. The integration of three-dimensional (3D) electroanatomical mapping systems with pre-acquired images of cardiac anatomy is recognized as a major advancement in the AF ablation technique.

Both computed tomography (CT) and magnetic resonance imaging (MRI) have been employed in this context,6 as they provide an accurate imaging of pulmonary vein (PV) and left atrial (LA) anatomy with excellent spatial resolution, supplying the necessary anatomic information for successful ablation.

In comparing these techniques, it should be emphasized that multi-slice CT angiography has become a standard non-invasive imaging technique to visualize vascular and cardiac anatomy. Moreover, CT is surely more widely available than MRI and is preferred in the evaluation of such structures as the pulmonary parenchyma, mediastinum, and upper abdomen.

The growing number of chest CT scans performed to diagnose coronary artery disease has led to a steep increase in the identification of so-called incidental or collateral findings, broadly defined as any finding that is unsuspected or unrelated to the clinical indication for imaging. Some of these findings may explain elements of the patient's clinical presentation, whereas others may reveal subclinical malignant disease, or even remain indeterminate and require further investigation or follow-up.

To date, no systematic data have been published on the prevalence and clinical implications of collateral findings in patients undergoing contrast-enhanced chest CT scan for image integration with electroanatomical mapping in view of an AF catheter ablation procedure. The aim of our study is to assess the prevalence and distribution of clinically significant collateral findings in such patients and to evaluate the impact of those findings on the further clinical management and prognosis of the study ...