Topic Page No.
2.9.3 Equivalent Dose 17
2.9.4 Effective Dose: 18
2.9.5 Interaction of Radiation with Tissue: 18
2.9.6 Scattering: 18
2.10 Radiation Units and Measurements: 19
2.10.1 Rem: 19
2.10.2 Sievert (Sv): 19
2.10.4Gray 20
2.10.5 Rad: 20
2.11 Radiation protection in radiography
20
2.11.1Methods of Exposure Control: 22
2.11.1.1 Collimators: 22
2.11.1.2Time: 22
2.11.1.3Distance: 22
2.11.1.4 Shielding: 23
2.11.2 Protection of the Patient in Medical X-ray Imaging 23
2.11.2.1 Tube Voltage and Beam Filtration 24
2.11.2.2Field Area, Organ Shielding, and Geometry 24
2.11.2.3 X-ray Image Receptors 25
2.11.3Technique Factors in Radiography 25
2.11.4 Scattered Radiation in Projection Radiographic Imaging: 26
2.11.4.1Moving Grids 26
2.11.4.2 Bucky Factor 26
2.11.5 Optimization:
27
2.12 Dose Limits:
29
2.13 Dose Reduction 30
2.14 X-Ray Detectors 31
2.14.1 Computed Radiography 31
2.14.2 Flat Panel Thin-Film-Transistor Array Detectors: 31
2.14.3 Ionization chamber
32
2.15 Image Quality:
32
Chapter one
Introduction
1.1 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
i.e., 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.
1.2 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.
1.3 Objectives of study:
1.3.1General:
The main objective of this study was to estimate the radiation dose for pediatric
patients undergoing X-ray examinations of the Chest and Abdomen.
1.3.2 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.
1.4 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.
.
