1. Overview of radiation dose to patients from medical
X-ray examinations in Nigeria
BI Akinlade1
. FB Odefemi2
and IP Farai2
.
Department of Radiation Oncology1
, College of Medicine and
Department of Physics2
, University of Ibadan, Nigeria
Afr. J. Med. med. Sci. (2016) 45,
Abstract
Objectives:Medical Imaging accounts for the largest
radiation exposure of population from artificial
sources of radiation. The radiation dose received by
patients from medical x-ray examinations in Nigeria
has shown large variations within and among
diagnostic centers for similar examinations. This
could be traceable to lack of imaging protocols and
local/national diagnostic reference levels. Hence, the
need to assess the trend of radiation dose to patients
from radiological practice in Nigeria.
Methods:Entrance surface doses(ESDs) reported by
Nigerian authors forcommonx-ray examinations
from 2000 – 2014 were extracted from articles
published in peer reviewed journals, analyzedand
compared with internationally recommended
Diagnostic Reference Levels(DRLs).
Results:Among x-ray examinations, skull accounted
for 32% followed by chest (22%), lumbar
spine(13%), abdomen(12%), pelvis(8%),
extremities(8%), thorax and cervical spine(5%). The
range of mean ESDs reported for various projections
of x-ray examination arechest (2.28 – 3.70 mGy);
Abdomen (4.42 – 7.22 mGy); Skull (3.81 – 5.19
mGy); Pelvis (5.93 mGy); Lumbar spine (5.73 –
10.98 mGy); Thorax (0.96 – 1.85 mGy); Cervical
spine (1.45 – 1.49mGy) and Extremities (0.31 – 0.49
mGy).In this study, it was found that the mean ESDs
received by patients from chest, skull and pelvis
examinations were higher than the published DRLs
for similar x-ray examinations.
Conclusion: The results of this study showed that to
harmonize radiation protection of patients and
improve radiological practice in Nigeria there is need
for development of comprehensive national
diagnostic reference levels.
Keywords:Medical x-ray examination, Patient
Dose, Diagnostic Reference Levels, Radiation
Protection.
Résumé
Contexe: L’imagerie médicalecomptepour la plus
grande expositionde la population aux rayonnements
provenant de sources artificielles de rayonnements.
La dose de rayonnementdes examens radio
Correspondence: Dr. B.I. Akinlade, Department of Radiation
Oncology, College of Medicine, University of Ibadan, Nigeria.
E-mail: bidy2012@yahoo.com; bakinlade@comui.edu.ng
graphiquesmédicaux reçue par les patients au Nigeria
a montré de grandes variations au sein et entre les
centres de diagnostic pour des examens similaires.
Cela pourrait être traçable au manque de protocoles
d’imagerie et au diagnostic de référenceau niveau
local/national. Par conséquent, la nécessité d’évaluer
la tendance de la dose de rayonnement pour les
patients des pratiques radiologiques au Nigeria.
Méthodes: Les doses d’entréede surface (DES),
rapportés par les auteurs nigérians pour examens
radiographiquesmédicauxde l’an 2000 à 2014, ont
été extraites des articles publiés dans des revues,
analysés etcompareravec les niveaux de référence
diagnostique(NRD) recommandées
internationalement.
Résultats: Parmi les examens radiographiques,
lecrâne représentait 32% suivie de la poitrine (22%),
l’épine lombaire (13%), l’abdomen (12%), le bassin
(8%), les extrémités (8%), thorax et épine cervical
(5%). Le rangmoyen des DES rapportés pour diverses
projections d’examen radiographique sont la
poitrine(2,28 - 3,70 mGy); l’abdomen (4,42 - 7,22
mGy); lecrâne(3,81 -5,19 mGy); lebassin(5,93 mGy);
épinelombaire(5,73 -10,98 mGy); Thorax (0,96 - 1,85
mGy); épine cervical (1,45 - 1.49mGy) et extrémités
(0,31 à 0,49 mGy).Dans cette étude, il a été constaté
que les DES moyennesdes examens reçues par les
patients provenant de la poitrine, du crâne et du bassin
étaient plus élevés que les NRD publiées pour des
examens radiographiques similaires.
Conclusion: Les résultats decetteétudeont montré que
pour harmoniser la protection radiologiquedes patients
et améliorer la pratique radiologique au Nigeria, il y a
un besoin pour le développement des niveaux de
référence diagnostique compréhensif national.
Mots-clés: Examen radiographique médical, Dose
dePatient, Niveaux de référence diagnostique,
protection contre les radiations.
Introduction
Medical exposure of man to ionizing radiation arises
from practices such as diagnostic, therapeutic and
nuclear medicine procedures. Consequently, the
patients,medical radiation specialists and the general
population receive significant exposure to ionizing
radiation. Medical exposure to radiation,from
artificial or man-made radiation sources, contributes
the largest component of radiation dose to general
population [1].It has also been estimated that

2. diagnostic radiology and nuclear medicine
procedures contribute 96% and 88% of dose to the
collective effective dose from man-made sources of
radiation in the United Kingdom [2] and United State
of America [3]respectively.
Exposure to ionizing radiation carries risk
of cancer induction and risk of hereditary disease in
descendants of the exposed person. There is also the
possibility of manifestation of deterministic effects
of radiation such as erythema, cataracts, temporary
or permanent infertility among others. However, the
overall benefits from diagnostic use of ionizing
radiation in medicine greatly exceed the associated
risks to an individual’s exposure to radiation.
Patients’ dosesfrom medical x-ray
examination reportedin peer reviewed journals by
Nigerian authors [4-16]have shown large inter- and
intra-hospital variations for similar radiological
examinations. Thus, presented the needto have a
national standard for medical diagnostic procedures
and set reference dose level for individual x-ray
examinations in Nigeria. This will go a long way in
reducing inter- and intra-hospital dose range factors,
thus bringing radiation doses to as low as reasonably
achievable (ALARA principle) and consistent with
clinical objectives of the examinations.
The European Commission [17]introduced
the use of diagnostic reference levels (DRLs) as an
efficient standard for optimizing radiation protection
of patients in diagnostic radiology. Thisdose quantity
was introduced to ensure that exposure factors (dose
descriptors) used during imaging processarewithin
the European recommended values. In Nigeria, both
local (limited to specific centres) diagnostic
reference levels (LDRLs) and national diagnostic
reference levels (NDRLs) are not available.
The aim of this study is to review the trend
of radiation doses to patients from common
radiological examinationsin the last 14 years (2000
– 2014) and compare them with recommended
(international) diagnostic reference levels (DRLs)
for assessment of radiological practice in Nigeria.
Materials and methods
Various studies on entrance surface dose (ESD) from
x-ray examinations in Nigeria were searched online
using the google scholar search engine. The inclusion
criteria includes articleson entrance surface dose
from x-ray examination published by Nigerian
authors from 2000 – 2014. The articles that met the
criteria wereassessed from their respective peer
reviewed journals for extraction of necessary data.
These includeESD values for common x-ray
examinations namely, the skull, chest, abdomen,
pelvis, spine (lumbar and cervical) and extremities.
These x-ray examinations were performed at
different x-ray diagnostic centres, widely distributed
across the country and are presented in Table 1.
The model of x-ray machines used to
perform x-ray examination in each of the centreswere
also extracted and are presented in Table 2 even
though some authors did not report this.The exposure
parameters used for various x-ray examinations and
other dose quantitiesextractedfrom the articles
include tube voltage (kVp),tube loading (mAs),
organ dose and effective dose received from the
procedure.These values were used to assess the trend
BI Akinlade. FB Odefemi and IP Farai
Table 1: List of Diagnostic Centres and their respective Regional Location
S/N Hospital/Diagnostic Centres Geo Political Zone in Nigeria
1. University College Hospital, Ibadan South-West
2. Two-Tees X-ray Diagnostic Centre, Ibadan South-West
3. Adeoyo Hospital, Ibadan South-West
4. Oluyoro Catholic Hospital, Oluyoro, Ibadan South-West
5. St. Mary’s General Hospital, Eleta, Ibadan South-West
6. Federal Medical Centre, Owerri South-East
7. Braithwaite Memorial Specialist Hospital, Port-Harcourt South-South
8. Niger State Hospital, Minna North-Central
9. Ladoke Akintola University of Technology Teaching Hospital South-West
10. Ogun State Hospital, Ijebu-Ode South-West
11. National Hospital, Abuja North-Central
12. Obafemi Awolowo University Teaching Hospital Complex, Ile-Ife South-West
13. University of Port-Harcourt Teaching Hospital South-South
14. University of Benin Teaching Hospital South-South
15. Central Hospital, Benin-City South-South

3. of radiation dose received by patients from various
medical x-ray examinations.
The range and mean values of applied
exposure parameters were compared with the values
in the guidelines on image quality criteria published
by the European Commission [18] and National
Radiological Protection Board (NRPB) [19]. Also,
the corresponding ESD reported for each x-ray
examination wascompared with the international
DRLs for similar examinations.All the extracted data
were analyzed using Microsoft Excel 2010 and
presented in tables and pie chart.
Results
The exposure parameters and patients’ data such as
thetube voltage (kVp), tube loading(mAs), age,
weight and entrance surface dose (ESD) were
carefully collated for common x-ray examinations
Trend in radiation dose from diagnostic x-ray examinations
Table 2: X-ray Centres and their respective X-ray Machines
S/N Hospital X-rayUnit/Model Number
1. University College Hospital, Ibadan Apollo (GEC Medical) (Dnamax HD 50D)
2. Two-Tees X-ray Diagnostic Centre, Ibadan GEC Medical Roentgen 201
3. Adeoyo Hospital, Ibadan Not stated in the published report
4. Oluyoro Catholic Hospital, Oluyoro, Ibadan Medirol-1
5. St. Mary’s General Hospital, Eleta, Ibadan GEC medical
6. Federal Medical Centre, Owerri Visitor (AR 30)
7. Braithwaite Memorial Specialist Hospital,
Port-Harcourt Italray (MOEPXH 04 rev 01)
8. Niger State Hospital, Minna GEC Medical Dynamax 40
9. Ladoke Akintola University of Technology
Teaching Hospital Not stated in the published report
10. Ogun State Hospital, Ijebu-Ode Not stated in the published report
11. National Hospital, Abuja Not stated in the published report
12. Obafemi Awolowo University Teaching
Hospital Complex, Ile-Ife Not stated in the published report
13. University of Port-Harcourt Teaching Hospital Not stated in the published report
14. University of Benin Teaching Hospital Not stated in the published report
15. Central Hospital, Benin-City Not stated in the published report
Table 3: Summary of patients’demographic data and exposure parameters used for common X-ray examinations in
Nigeria with their range and mean values (in parenthesis)
Examination Age (year) Weight (kg) kVp Range mAs Range Mean (kVp, mAs)
Chest PA 14 – 75(44) 38- 116 (55) 50 -110 5 – 60 76.1, 24.1
Chest LAT 16 – 70(44) 42 – 88 (69) 33 – 100 5 – 75 69, 52
Abdomen AP 16 – 85(44) 45 – 81 (69) 54 -100 25 – 80 85.5, 80.5
Abdomen PA 18 – 57(46) 60 – 75 (71) 69 – 110 80 – 160 87, 125.5
Skull AP 20 – 71(41) 52 – 95 (68) 63 – 100 30 – 100 81, 41.8
Skull PA 20 – 71(40) 52 – 95 (75) 69 – 90 30 – 100 86.3, 69
Skull LAT 20 – 65(40) 48 – 100 (63) 63 – 90 30 – 100 68.3, 69
Pelvis AP 18 – 73(53) 37 – 85 (74) 50 – 112 5 – 160 84.8, 103.5
Lumbar Spine AP 27 – 74(55) 65 – 73 (71) 60 – 91 20 – 250 68.3, 160
Lumbar Spine LAT 27 – 80(53) 65 – 73 (70) 80 – 92 200 – 250 89.9, 225
Thorax PA 20 – 70(49) 60 – 73 (45) 67 – 77 12.5 – 25 71, 20.78
Thorax RLAT 27 – 80(47) 60 – 73 (64) 70 – 80 25 – 35 76.2, 30.7
Cervical Spine AP 26 – 65(46) 67 – 75 (71) 69 – 80 25 – 35 77, 30.5
Cervical Spine LAT 26 – 65(46) 60 – 78 (72) 69 – 83 30 – 35 77, 31.5
ExtremitiesAP 19 – 75(45) 68 – 73 (70) 45 – 75 5 – 40 60.5, 18.0
Extremities LAT 19 – 75(43) 67 – 75 (68) 45 – 91 5 - 40 63.5, 31.5
Hand and Wrist PA NA NA NA NA NA
PA: Posterior-Anterior; AP: Anterior-Posterior; LAT: Lateral; RLAT: Right Lateral; NA: Not Applicable.

4. namelychest, thorax, abdomen, skull, spine (lumbar
and cervical), pelvis, and extremities. In all, the skull
had the highest frequency (32%),followed by chest
(17%), lumbar spine (13%) and abdomen (12%).
The frequency of the remaining x-ray
examinations wasless than 10% each and the
distribution of all examinations is shown in figure
1.The exposure parameters(kVp and mAs) and
BI Akinlade. FB Odefemi and IP Farai
Fig.1: Pie chart showing distribution of examinations in percentage.
Table 4: Distribution of Entrance Surface Dose (ESD) values (mGy) from 17 X-ray projections
Radiograph Projection Minimum Maximum Mean Max/Min
Chest PA 0.40 5.59 2.28 13.98
Chest LAT 3.70 3.70 3.70 1.00
Abdomen AP 0.70 0.96 4.42 8.30
Abdomen PA 7.22 7.22 7.22 1.00
Skull AP 3.00 8.55 5.19 2.85
Skull PA 3.00 5.17 3.81 1.73
Skull LAT 1.70 6.97 3.84 4.10
Peliv AP 0.67 10.21 5.93 15.24
Lumber spine AP 0.62 10.93 5.73 17.63
Lumber spine LAT 1.3 20.67 10.98 15.90
Thorax AP 0.96 0.96 0.96 1.00
Thorax RLAT 1.85 1.85 1.85 1.00
Cervical spine AP 1.45 1.45 1.45 1.00
Cervical spine LAT 1.49 1.49 1.49 1.00
Extremities AP 0.47 0.47 0.47 1.00
Extremities LAT 0.49 0.49 0.49 1.00
Hand and wrist PA 0.31 0.31 0.31 1.00
PA: PA Posterior - Anterior -AP: Anterior Posterior; LAT: Lateral: RLAT: Right Lateral

5. patients’ demographic data (age and weight) for
various x-ray examinations are presented in Table
3. The age of patients ranged from 14 - 80 years
whereas their weight ranged from 38 - 116 kg. The
tube voltage and tube loading selected for various
x-ray examinationsranged from 50 – 115 kVp and 5
– 250 mAs respectively.
The ESD received by patients from various
x-ray examinations are presented in Table 4. In
general, the lowestvalue of ESD (0.31 mGy) was
obtained from x-ray examination of the hand & wrist
while the maximum value (10.98 mGy) was from
examination of the lumbar spine.The mean
ESDsfrom various x-ray examinations were
compared with the dose reference level, published
by various international bodies, for similar x-ray
examinationsand are presented in Table 5.
Discussion
Thetrend of radiation dose received by patients
undergoing common x-ray examinations in some
Nigerian hospitals and diagnostic centrewithin the
period of fourteen years has been reviewed. The
mean age and weight of patients for chest x-ray
examination (PA and Lateral) were 44 yearsand 62
kg respectively whereas, the mean exposure
parameters (kV and mAs) selected for the
examination were 76 kV and 38mAs respectively,
as seen in Table 3. While the tube loading (mAs)
was higher, the tube voltage (kVp) applied for these
Trend in radiation dose from diagnostic x-ray examinations
patients is lower than the kVp(125 kV) published
for chest PA in the European guidelines [18] and
mean values (85 kV, 5mAs)published by the NRPB
[2] for patients (63 years, 70 kg).
This variation in kVp may be due to
variation in patients’ weight or size, while the
variation in mAs may be attributed to aged or
obsolete x-ray machines, usually used in most
diagnostic centres in Nigeria. The use of high mAs
in x-ray examination is usually associated with
increase in radiation dose to patient.However, the
combinationof low mAsand high kVp techniques has
been reported in literature for chest x–ray
examinations [20]and it has been shown that the use
of high voltage (more penetrating radiation)
techniquefor chest radiography reduces the entrance
surface dose to patient by 50% without loss of image
quality.
In the case of abdominal x-ray examination
of patients (45 years, 70 kg), the mean exposure
parameters (86 kV, 103 mAs) used for this procedure
were found to be higher than the mean value (74kV,
46mAs) published by the NRBP for patients (52 71
kg). The situation is the same for skull x-ray
examination, where the mean exposure parameters
selected (85 kV, 60 mAs) for patients (40 years, 69
kg) were higher than the NRPB values (72kV, 30
mAs) for patients (45 years, 70 kg). Also, the mean
exposure parameters (85 kV, 104 mAs) selected for
patients (53 years, 74 kg) during pelvis x-ray
Table 5: Comparison of mean ESDs (mGy) obtained in this study with the DRLs (mGy) published by various
International bodies
Examination This Study CEC (1996) IAEA (1996) Malaysia (1998) NRPB (2000)
Chest PA 2.8 0.30 0.20 0.28 0.28
Chest LAT 3.70 NA NA 1.40 1.00
Abdomen AP 4.42 10.00 10. 10.00 6.00
Abdomen PA 7.22 10.00 10.00 10.00 6.00
Skull PA 5.19 5.00 2.50 4.78 3.00
Skull AP 3.81 3.00 2.50 4.78 3.00
Skull LAT 3.84 5.00 1.50 3.34 1.50
Pelvis AP 5.93 NA NA 8.41 4.00
Lumber spine AP 5.73 10.00 5.00 10.56 6.00
Lumber spine LAT 10.98 30.00 10.00 18.60 14.00
ThoraxAP 0.96 NA NA NA 3.50
Thorax RLAT 1.85 NA NA NA 10.00
Cervical spine AP 1.45 NA NA NA NA
Cervical LAT 1.49 NA NA NA NA
ExtremitiesAP 0.47 NA NA NA NA
Extremities LAT 0.49 NA NA NA NA
Hand and wrist PA 0.31 NA NA NA NA
PA: Posterior-Anterior; AP: Anterior-Posterior; LAT: Lateral; RLAT: Right Lateral; NA: Not Applicable.

6. examination were found to be higher than the NRPB
mean values (74 kV, 35mAs) for patients (61 years,
70 kg).
With the exception of tube loading, the mean
exposure parameters (89kV, 193 mAs) selected for
patients (54 years, 71kg) during x-ray examination
of the Lumbar spine were similar to that of NRPB
values (87 kV, 75 mAs, 53 years & 70 kg). The same
was found in x-ray examination of the thorax
(thoracic spine) of patients (48 years, 55kg), where
the mean exposure parameters selected (74kV, 26
mAs) were similar to the mean NRPB values (75kV,
49 mAs, 53 years, 70 kg)except for the applied low
mAs, which could be attributed to the differences in
patients’ weight or size.
The mean exposure parameters (77 kV, 31
mAs) selected for patients (46 years, 72 kg) during
cervical spine x-ray examinations andthose (62 kV,
31 mAs) selected for patients (44 years, 69 kg) during
extremities examination could not be compared with
NRPB values. This is because x-ray examinations
of the cervical spine and extremities were not listed
in the NRPB publications.
When the entrance skin dose (ESD) obtained
in this study was compared with similar x-ray
examination published by the NRBP, as seen in Table
5,it was found that the ESD values for PA chest
(2.28mGy) andAP skull (5.19mGy)were higher than
the NRPB values (0.20mGyand 3.00mGy
respectively). Similarly, when the mean ESD
obtained in this study for various x-ray examinations
was compared with the dose reference levels (DRLs)
published by some international bodies namely,
Commission of European Communities (CEC) [18]
and International Atomic Energy Agency
(IAEA)[19], it was again discovered that the x-ray
examinations of the chest (PA)and skull (AP)have
values (2.28 mGy and 5.19mGy respectively) higher
than the DRLs published by the CEC (0.30 mGy and
5.00 mGy) andthe IAEA (0.20 mGy and 2.50 mGy).
It is important to note that the highest ESD
value (10.98mGy) obtained in this study was from
x-ray examination of the Lumbar spine (LAT)and
yet it is lower than the value (14.00mGy) published
by NRPB for similar examination. However, the
DRLs published by NRPB for pelvisx-ray
examination (4.00 mGy) is lower than the mean ESD
(5.93 mGy) obtained in this study for similar
examination.
In general, the variations in the values of
ESDs (mean, minimum & maximum)obtained in this
study for various x-ray examinations and the DRLs
values published in literatures for similar x-ray
examinations may be attributed to several factors,
such as differences in the number of patients
recruited into the study, patient weight, exposure
parameters used by different operators (mAs, kVp),
total tube filtration and the use of grids in some of
the x-ray procedures.
In conclusion, thesignificant dose variations
for similar x-ray examination found in this study is
an indication that further optimization is possible.
This would be achieved through establishment and
implementation of local and national diagnostic
reference levels. This national dose reference levels
(NDRLs) would serve as a guide in the choice of
exposure parameters and imaging protocol that will
ensure adequate control of medical radiation
exposure to a level corresponding to the objective
of an imaging task. Furthermore, NDRLs will
enhanceprocess of patient exposure optimization and
provide a framework with which dose levels from
hospitals and diagnostic centresare compared.
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