Determinantion of entrance skin dose from the diagnostic of human chest x-ray
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Department of Medicine
Abstract
Pediatric radiography is a challenging procedure from the perspective of
radiation dosage. Children are approximately ten times more sensitive to
radiation-induced cancer than middle-aged adults and three times more
sensitive than the population average.
A total of 100 patients were enrolled in this study. ESDs were evaluated for the
chest postero-anterior (PA) projection and abdomen antero-posterior (AP)
projection. For each studied examination, the patient anthropometrical data (sex,
age, weight and height) and technical parameters used (kVp, mAs and FSD)
were collected at the time of the examination on a self-designed data collection
sheet. The ESD was assessed by indirect method, with the data on the radiation
output of the X-ray tube and exposure factors (kVp, mAs and FSD). The image
quality for each examination was also assessed using quantitative technique.
The result of the study revealed that the (mean ± SD) for ESDs were found to
be (0.11 ± 0.03 mGy), (0.41 ± 0.15 mGy) for PA chest and abdomen
consequently. The maximum ESD for abdomen (0.723 mGy) observed at
maximum kVp (62 kVp) which emphases the significant correlation between
kVp and ESD, no correlation was found between patient age or weight and
ESD. Image resolution in term of information entropy was optimum and
correlated with selected Kvp and mAs.
The study is considered as an attempt to evaluate the ESDs received by digital
radiographic x-ray machine for children aged between 1 - 8 years old, taking
into considerations number of other variables. The mean ESD values obtained
are found to be within the standard reference. It may provide guidance on
where efforts on dose reduction will need to be directed to fulfill the
requirements of the optimization process and serve as a reference for future
researches.
List of Contents
Topic Page No
Dedication II
Acknowledgement III
List of figures IV
List of tables V
List of abbreviations VI
Abstract VII
VIII ØÂ�Ù„ØÂ�ØÂ�Ù„ØÂ�ØÂ�
Chapter One
11 Introduction 1
12 Problem of study 2
13 Objectives 3
14 Definition of Entrance skin dose (ESD( 3
15 ESD calculation 3
16 Thesis layouts 3
Chapter Two
21 X -ray beam quantity 4
22 X -ray beam quality 7
23 Interaction of radiation with matter 7
24 Biological Damage: 11
25 Direct and indirect damage 12
251 Direct damage 12
252 indirect damage 13
26 Organ response to radiation 13
27 Somatic and genetic effects 13
271 Somatic Cell Damage 13
271 Tissue Damage 14
28A stochastic effect 15
29 Radiation quantities 16
291 Absorbed Dose 16
292 Kerma 17
293 Equivalent Dose 17
294 Effective Dose: 18
295 Interaction of Radiation with Tissue: 18
296 Scattering: 18
210 Radiation Units and Measurements: 19
2101 Rem: 19
2102 Sievert (Sv): 19
2104Gray 20
2105 Rad: 20
211 Radiation protection in radiography
20
2111Methods of Exposure Control: 22
2111
1 Collimators: 22
21112Time: 22
21113Distance: 22
21114 Shielding: 23
2112 Protection of the Patient in Medical X-ray Imaging 23
21121 Tube Voltage and Beam Filtration 24
21122Field Area, Organ Shielding, and Geometry 24
21123 X-ray Image Receptors 25
2113Technique Factors in Radiography 25
2114 Scattered Radiation in Projection Radiographic Imaging: 26
21141Moving Grids 26
21142 Bucky Factor 26
2115 Optimization:
27
212 Dose Limits:
29
213 Dose Reduction 30
214 X-Ray Detectors 31
2141 Computed Radiography 31
2142 Flat Panel Thin-Film-Transistor Array Detectors: 31
2143 Ionization chamber
32
215 Image Quality:
32
216 Previous Studies
36
Chapter Three
31 Material: 38
311 Machine used 38
312 Subjects 38
32 Method 38
321 Technique used 39
322 Dose measurement 39
Chapter Four
Results 40
Chapter Five
51 Discussion 44
52 Conclusion 46
53 Recommendation 47
References 48
Chapter one
Introduction
11 Introduction:
Pediatric radiography is a challenging procedure from the perspective of
radiation dosage Because, it is well-known that the dose of radiation is an
extremely important issue in children, who are significantly more radiosensitive
and more likely to manifest radiation-induced changes over their lifetimes (Guo
et al, 2013) Children are approximately ten times more sensitive to radiation-
induced cancer than middle-aged adults and three times more sensitive than the
population average (Brenner et al, 2001) More people are exposed to ionizing
radiation for medical practice than any other human activity, and in many cases,
individual doses are highest Exposure to radiation in medicine involve people
undergo diagnostic radiographic, interventional procedures or radiation therapy
Diagnostic radiology examinations lead to higher risks per unit dose of
radiation to cancer in infants and children compared with adults
The International Commission on Radiological Protection (ICRP) asserted that
the use of effective dose is actually not recommended for assessing the risks of
stochastic effects in retrospective situations for exposures in patients, however
this quantity can be of value for comparing the use of similar technologies and
procedures in different hospitals and countries as well as the use of different
technologies for the same medical examination (2007)
The Entrance Skin Dose (ESD) is defined as the absorbed dose to air where the
X-ray beam intersects the skin surface of the patient including the backscatter
(Alm-Carlsson et al, 2007) The reasons for evaluating ESD is that; the
physical parameter recommended for monitoring the Diagnostic Reference
Levels (DRLs) in conventional radiography was the ESD and the dose is
greatest at the surface where radiation enters the body of the patient therefore the skin is the main organ for which there is a possibility of deterministic effect
ie, skin burn (Sharifat and Oyeleke, 2009) another reason the organs
equivalent dose can be estimate from the ESD and that very important especial
in case where the part of the body undergoing to be imaged contain sensitive
organ to the effect of radiation
DR has been shown to provide good resolution with no significant difference in
diagnostic quality at reduced radiation doses Volk’s study suggested that dose
reduction of approximately 50-75% had no significant impact on image quality
However, a more efficient detector on its own is not sufficient to ensure a
consistent low-dose operation in routine clinical practice (Völk et al, 2004)
The knowledge of the relationship that links image quality and radiation dose is
a prerequisite to any optimization of medical diagnostic radiology, because –
according to the ALARA concept – the dose received by the patient during a
radiological examination should be kept ‘as low as reasonably achievable’ The
image quality and dose required for a successful and reliable diagnosis depends
on physical parameters such as contrast, resolution and noise, the constitution
of the patient, the viewing conditions and also on the characteristics of the
observer that assesses the image (Al-Kinani and Mohsen, 2014)
This study was aimed to estimate the ESD for pediatric patients undergoing
diagnostic X-ray examinations of the chest and abdomen in pediatric hospital in
Khartoum, Sudan to help in applying optimization of radiation protection of the
patients
12 Problem of study:
Children increased mitotic activity and longer life expectancy, are more
radiosensitive than a middle-aged adult by a factor of up to 10
13 Objectives of study:
131General:
The main objective of this study was to estimate the radiation dose for pediatric
patients undergoing X-ray examinations of the Chest and Abdomen
132 Specific:
ï‚Â� To measure absorption dose for pediatrics during chest and abdomen
imaging
ï‚Â� To optimize the exposure factors those give good image quality and don't
exceed the radiation dose
ï‚Â� To measure effective dose for pediatrics during chest and abdomen
ï‚Â� To compare the estimated dose with published works and internationally
established diagnostic reference levels
14 Thesis layouts:
This study fells into fives chapters where; chapter one deals with introduction,
problem of the study, objectives, definition of Entrance Skin Dose and thesis
layout chapter two will high light about a theoretical background and literature
review, chapter three includes Methodology, chapter four about results , chapter
five present discussion, conclusion and recommendation
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