Determination of Radiation Dose from Routine X-ray Examination at Three Selected Hospitals in AlNajaf, Iraq

People who undertaken different X-ray examinations are already exposed to ionizing radiation which causes biological effects. Therefore assessing the patient radiation dose is a prerequisite element in optimizing the X-ray practice and to avoid the unnecessary radiation dose. The aim of this research is to assess the skin radiation dose for those patients who undertaking routine X-ray examinations in selected three hospitals in Al Najaf city. Three X-ray units were involved in this experimental study; these were belonging to three hospitals in Al Najaf city-Iraq, namely Al-Sadder teaching hospital, AlHakeem general hospital and Al-Zahraa hospital. Data of exposure parameters (tube potential (kVp), tube current (mAs) and source to detector distance (d cm)). The data were collected from 160 patients exposed to radiation during different X-ray examinations. Patients were chosen to be within adult range (>18 years) and the selection was random (male and female). Patient skin dose was calculated mathematically using an established formula depending on the recorded exposure factor (kVp, mAs and d). Different X-ray examinations were considered, namely skull Posterior –anterior (PA), skull Lateral (LAT), chest PA, chest LAT, abdomen Anterior-posterior (AP), pelvis AP, lumbar spine AP and lumbar LAT. The average skin dose for all X-ray examinations considered in this research were as follow: 0.9, 0.76, 0.23, 0.41, 1.85, 1.82, 2.03 and 3.44 mGy, for skull PA, skull LAT, chest PA, chest LAT, abdomen AP, pelvis AP, lumbar spine(LS) AP and Lumbar spine (LS)LAT respectively. The results demonstrate that the dose values were comparable to those that were previously reported in published reference.


Introduction
In both developed and developing countries, the number and the range of X-ray facilities and Xray equipment have been increased rapidly [1]. Although alternative means for diagnosis such as ultrasound and MRI are becoming increasingly available, steady improvement in the quality of X-ray images and patient protection have ensured that diagnostic X-rays remain the most used tool in the diagnosis [2] This reason makes X-ray a major contribution to man's exposure to ionizing radiation from man-made sources. In recent years, health physicists have devoted much effort to minimize a patient dose of radiation in diagnostic radiology [3]. Through these efforts, substantial reductions in radiation dose to patients resulting from radiographic procedures have been achieved in many countries [4].The International Atomic Energy Agency (IAEA) has recommended guidance levels of dose for diagnostic radiography for a typical adult patient. These levels were intended to act as thresholds to trigger investigations or corrective actions in ensuring optimized protection of patients and maintaining appropriate levels of good practice. Since guidance levels should be derived from a wide scale, surveys of exposure factors performed in individual hospitals [5]. Several dose surveys were conducted recently in different countries such as Sudan, Syria, Iran and Saudi Arabia. Some of these studies found the patient doses were comparable to the published international levels, whereas others found it to be higher than the recommended level [6][7][8][9][10].
The aim of this study is to measure patients' surface dose arising from X-ray examinations of the pelvis AP, abdomen AP , skull (PA and LAT) , chest(PA and LAT) , and lumbar spine (AP and LAT) in three hospitals in Al Najaf city. The result of this study can be used as a reference for radiographic examinations. The patient dose was estimated in the present study in terms of Surface dose.

Material and Methods
The data were collected from 160 patients with an average mass of 70 kg at three major hospitals in Al Najaf city, Iraq, which comprising three x-ray units. Radiographic projections studied were: Chest PA/LAT, Lumbar Spine AP/LAT, abdomen AP, Pelvis AP and Skull PA/LAT. For each patient, the following exposure parameters were recorded: peak tube voltage (kVp), exposure current-time product (mAs), and the focus-to-film distance (FFD). These parameters were used in surface dose assessment using the following formula [11,12]: Surface dose(µGy)= 418(kVp) 1 …… (1) Where kVp is the peak voltage which responsible for the quality of penetration, mAs is the tube current responsible for the quantity of electrons from the filament, T is the total filtration of the beams (2.5mmAl) and skin source distance (SSD) where SSD = focal film distance (FFD)patient thickness. The above equation was formulated into a program using matlab to facilitate the process of mathematical calculations of patients' skin dose and to reduce the error (Figure-1).

Results
This work was carried out in three major hospitals in Al Najaf city-Iraq. These hospitals are Al-Sadder teaching hospital, Al-Hakeem general hospital, and Al-Zahraa hospital. The mean and standard deviation of the exposure factors( kV, mAs, SSD) were determined for the following examinations: Skull PA/LAT, Chest PA/LAT, Abdomen AP, Pelvis AP, L-S AP/LAT Tables-(1-4). The weights of the patients were considered.

Discussion
In this study kVp, mAs and SSD were ranged from (63-120) kVp, (1.754-40) mAs and (80-160) cm, respectively. The surface dose at (Al-Sadder hospital) was the highest and for all X-ray examinations and this may due to the high tube output of the machine combined with low tube filtration [14]. For Skull (PA&LAT) all values were below the IAEA recommended level. In LS (LAT) examinations, all hospitals showed that the surface dose values were higher than the IAEA reference dose. This could be attributed to the relatively high exposure parameters used in these hospitals [15]. It is also possible that the skills and the experience of the radiographers had certain effect on the resulted patients' doses [16]. Similar reason can be made for other hospitals where high surface dose values were observed, to lower the dose, radiographers should decrease either the tube potential or the tube voltage or both when no impact on the image quality is observed. Also, one can keep the tube potential and tube loading constant while altering the distance taking advantage of the inverse square law. In general, all values of surface dose in this study within the IAEA recommendation in spite of a slight increase in some cases.
The high doses can be attributed to the relatively higher X-ray tube parameters used. In examinations (Skull PA/LAT, Chest PA/LAT, Abdomen AP, Pelvis AP and L/S AP/LAT), the highest values of the surface dose for LA LAT were found to be around 4.1 mGy ±0.77 in Al-Sadder hospital, 3.17 in Al-Zahraa hospital and 3.2 in Al-Hakeem general hospital. The variations in results of the three hospitals, as reflected in the range values, were partially due to variations in patient size and used technique. The highest tube potentials used were reported in Al-Sadder teaching hospital for LS-LAT (120 kVp).

Conclusions
Radiation dose for the patient who undertaken chest (PA and LAT), skull (AP and LAT), abdomen (AP), pelvis (AP) and LS (AP and LAT) examinations in three hospitals in Najaf were determined. The individual skin dose values were observed to be consistent with the range of values that were reported in other studies with some slight decrease and increase in certain value at certain radiological positions. The mean values of the present study were comparable with reference levels in literature.