Keywords: Quality confidence, quality control, environmental monitoring, radiation, X-ray end product
In Nigeria, X-rays is the most often used ionizing radiation in medical specialty despite progresss in magnetic resonance imagination and ultrasound techniques. It has maintained a cardinal function in diagnosing of diseases, hurt and in X-ray therapy. In consequence it is the largest manmade beginning of ionising radiation to the universe population ( ICRP, 1991 ; UNSCEAR, 1993 ; Muhogora and Nyanda, 2001 ) . X ray is the major subscriber to the effectual dosage of both the patient and the forces. Because of the radiological hazards involved, it is normally recommended that dosage to patient from X-ray be kept every bit low as moderately accomplishable ( ALARA ) with equal image quality ( IAEA, 1996 ) . In add-on, programmes for diagnostic imagination sections, irrespective of the size, should at least contain the undermentioned constituents: equipment quality control, administrative duties, hazard direction and radiation safety programme. Equipment quality control unit carries out rating of equipment public presentation to guarantee proper image quality, every bit good as patient and operator safety ( Papp, 2002 ) . Furthermore, radiation safety unit is to guarantee that patient exposure is kept every bit low as moderately accomplishable and that departmental forces, medical staff and members of the general populace are protected from overexposure to ionising radiation.
Presently, there are far above 4000 X-ray machines in Nigeria ( Elegba, 2006 ) out of which less than 5 % are under regulative control. These thereby pose a great jeopardy to the patient, forces and challenges to the regulative organic structure in Nigeria. As a consequence of handiness of X-ray installations, some new while others are 2nd manus ( known locally as Tokunbo ) , there has been a changeless addition in the figure and frequence of X-ray scrutinies in recent times. In Northwestern part of Nigeria for illustration, a study of 124 establishments with beginnings of ionising radiation indicates that 203 X-ray installings were found with merely 90 sealed radiation beginnings ( Mallam et al. , 2004 ) . In the same study, Ahmadu Bello University Teaching Hospital ( ABUTH ) complex on norm carries out over 250 diagnostic X-ray scrutinies per twenty-four hours in the three infirmary installations located in Zaria, Kaduna and Malunfasi. The population of the open persons and the frequence of exposure is an indicant that one-year collective dosage to patient can be rather important.
The quality control ( QC ) programme comprises the regular testing that must be carried out on each major constituent of the system to guarantee optimal public presentation within the system ( West,1993 ) . In diagnostic radiology QC trial is carried out to guarantee that a high quality diagnostic image is produced for a minimal radiation dosage to the patient ( NRPB, 1988 ) . The major equipment in diagnostic radiology to which quality control can be applied include X-ray production, sensing, image processing and image viewing equipment among others. The equipment testing is coupled with everyday environmental monitoring and appraisal of image quality ( Oluwafisoye et al. , 2009 ) .
( 1.1 ) Nigerian Nuclear Regulatory Authority ( NNRA )
Due to the hurtful effects of ionising radiation, the Nigerian Nuclear Regulatory Authority ( NNRA ) was established by the Nuclear Safety and Radiation Protection Act of 1995. This national regulative organic structure is charged with primary duty of atomic safety and radiation protection. The Act empowered the NNRA to categorise and licence activities affecting exposure to ionising radiation in peculiar, the ownership, production, processing, industry, purchase, sale, import, export, managing, usage, transmutation, transportation, trading, assignment, conveyance, storage, and disposal of any radioactive stuffs, atomic stuffs, radioactive waste, and any equipment breathing ionising radiation. In this respect, the NNRA in her papers made proviso for minimal demand for the equipment care in line with international regulative policies.
As portion of the attempt at heightening safety in the usage of ionising radiation in Nigeria, the National Institute of Radiation Protection and Research ( NIRPR ) was established under the counsel of NNRA. The Institute trains forces in the radiation protection.
The present measurings were conducted to look into the suitableness of the quality control trials and the stated tolerance degrees for assorted X-ray equipment at four Nigerian infirmaries. Additionally, environmental radiation supervising around the installations was carried out to determine the safety degree of both the patient and forces.
( 2 ) MATERIALS AND METHODS
Quality control trial ( kVp truth and duplicability, mAs one-dimensionality ) of four government-owned infirmaries, one general infirmary ( GHL ) , two specializer infirmaries [ Psychiatric infirmary ( PSH ) and National Orthopaedic infirmary ( NOH ) ] and one military infirmary ( NARH ) , all located in Lagos were carried out. The GHL has two functional X-ray units depicted as machine 1 ( M1 ) and machine 2 ( m 2 ) . The probe was carried out with the aid of the staff of the radiology section of each infirmary. Meanwhile, each of the X ray installations was used for both pediatric and big scrutinies. In all the infirmaries there was no old exposure and QC informations available. The information use was done utilizing Microsoft Excel, 2003.
( 2.1 ) Measurement of X-ray tubing Output and exposure clip merchandise
X-ray tubing end product is the sum of exposure, in millirontgens ( Mister ) delivered to a point in the Centre of the utile X-ray beam at a distance of 1 meter from the focal topographic point for 1 ma of negatron passing through the tubing. The end product expresses the ability of the tubing to change over electronic energy into X-ray exposure. X-ray tubing end product is the individual most of import parametric quantity to quantify radiation output ( Zoetelief et al, 2006 ) . The free-in-air exposure, FAE ( Mister ) was measured utilizing mill calibrated KV metre ( US made Victoreen X-ray trial device, theoretical account 4000 M+ ) obtained from the Department of Physics ( DOP ) University of Ibadan. The consistence of X-ray tubing end product with the tubing current ( ma ) or tube current exposure-time merchandise ( ma ) was measured for the scope of ma or ma values used in pattern. The sensor ( KV metre ) measures the mean, effectual and maximal extremum tubing electromotive force, power stage, exposure and exposure clip. This system determines the tubing electromotive force with truth of ± 2 % ( Victoreen, 1995 ) . The internal ionisation chamber that measures exposure has volume of 36 cm3. The exposure clip is measured to an truth of ± 2 % . The FAE ( Mister ) measured is converted into end product in mGy ( ma ) -1 by multiplying by a factor 0.00877/ ma ( Chang Jong and Hui- Yu, 1999 ) where ma in the denominator is the merchandise of the tubing current and exposure clip set at the clip of measuring of the end product.
( 2.2 ) Environmental Monitoring and General Observations
The guiding rule used in all regulative paperss is that, radiation doses to the populace and to the people who work with radiation must be kept every bit low as moderately accomplishable ( ALARA rule ) . In kernel, radiation workers and the patient should be monitored at all times when working. The ground for this monitoring is to guarantee that the pattern being followed by the workers in their day-to-day modus operandi are safe and do non ensue in high doses being received. In the present survey, the dose rate at different points of involvement ( the console, entryway door behind the wall, patient waiting seats ) was measured with radiation sensor ( radiation proctor 4 minirad 1000+ ) . This device measures radiation dosage rate in ?Sv/ hour.
( 2.3 ) Optical and Radiation Field Congruence/ Beam Alignment
The beam control system is required for modulating the size of X-ray field country. Therefore, it plays an of import function in dose delivered to the patient because it controls the sum of patient surface country exposed to radiation and image contrast ( due to scattered radiation ) . The parametric quantities taken into consideration in beam control system include ; beam alliance, optical radiation field congruity, truth of the x Y graduated tables and illuminator bulb brightness. In this survey optical radiation field and beam alliance were examined.
( 2.4 ) Ocular reviews
One of the three parts of a quality control programme for a radiographic installation is ocular review. This portion includes look intoing the chief constituents of the equipment for proper operation, safety and good mechanical status. It is expected that they should include ; protective lead dress, lead shield of the cell wall, overhead tubing Crane, radiographic tabular array, control panel and other installations such as door and automatic visible radiation.
( 3 ) RESULTS AND DISCUSSION
Five X-ray units in four infirmaries were investigated in the survey. Both the QC and environmental appraisal of the installations were carried out. Table 1 presents the radiographic equipment information at assorted infirmaries investigated. The old ages of industry of the equipment scope from 9 to 31 old ages, while the twelvemonth of installing is between 5 and 31 old ages. The consequence of age on the end product of an X-ray machine is good documented ( Mallam et al. , 2004, Ogundare et al. 2004 ) .
( 3.1 ) X ray tubing Output
The consequence of X-ray tubing end product at a distance of 1m each from the focal point of five X-ray units are presented in Table 2. The values of end product obtained in GHL ( M2 ) are comparatively low, those measured in GHL ( M1 ) are higher than those found in M2. It ranged from 0.0318 to 0.1192 mGy ( ma ) -1. However, higher end products are found at the same electromotive force in PSH and NOH. As an illustration, at 80kVp the end products are 0.0796, 0.1676, 0.2156 and 0.0762 mGy ( ma ) -1 for GHL ( M1 ) , PSH, NOH and NARH severally. The fluctuation in the end product could be attributed to the wave form, anode stuff, filtration, and tube age and anode surface harm. Knowledge of the end product value for a given X-ray tubing permits the finding of both patient and movie exposures. It is besides used in the computation of Entrance Surface Dose ( ESD ) delivered to the patient at the point where the X-ray beam enters the patient. This dosimetry parametric quantity ( ESD ) gives the perspective appraisal of absorbed dosage to the patient. Although the entryway surface dosage is a hapless hazard index, it can be used to gauge the effectual dosage ( ED ) which better quantifies patient hazard ( Gkanatsios and Huda,1997 ) . The fluctuation in the end product among the infirmaries could take to fluctuation in doses delivered to the patients during the scrutinies.
The consistence of X-ray tubing end product with ma was measured for a scope of ma for the five X-ray units at different electromotive forces. The consequences are presented in figures 1-3. Furthermore, consequences of end product measured at different kVp above 80 kVp ( GHL and NARH ) show strong correlativity with ma, nevertheless, the end products measured at lower electromotive force of 60 and 75 kVp indicate weak correlativity with ma. The X-ray tubing and the anode current are extremely stabilized at this point ( Suliman and Elshiekh, 2008 ) .
The consequences of the tubing electromotive force truth for five X-ray units investigated are presented in tabular arraies 3a-3d. The tabular arraies show the tubing electromotive force set, the tubing electromotive force measured and the magnitude of divergence. It should be noted that the magnitude of divergence in kVp vary from infirmary to infirmary. In GHL, the divergence ranged between 0.9 and10.9 % for the two machines ( M1 and M2 ) . The scopes of magnitude of divergence for the three other infirmaries are ; 0.2 to 0.5 % , 45.5 to 72.7 % ( highest in this survey ) and 22.9 to 23.3 % in PSH, NOH and NARH severally. Both m1 ( GHL ) and PSH comply with the demand of ± 5 % , while M2 ( GHL ) , NOH and NARH exceeded the demand. The grounds for higher divergence in kVp found in NOH and NARH are multifactorial.
The European Commission recommended a high technique of 125 kilovolts IAEA ( 1995 ) which likely consequences in low doses, but the radiotherapists prefer the higher contrast thorax radiogram which consequences from low kVp. Earlier study indicated that increasing the tubing potency ( kVp ) from 8-13 kilovolt in lumbar and pectoral spinal column scrutiny resulted in a dose decrease of 26-36 % ( Martin et al, 1993 ) . The higher divergences outside the tolerance bound as obtained in the present survey show disagreements in kVp between the measured and the set values particularly if the tubings are non adequately maintained. Furthermore, the overly high divergence between the set and the measured kVp could cut down the image contrast ( Livingstone et al, 2004 ) . The unexpected elevated value of proficient parametric quantities which consequences from defective machine could impact both patient dosage and image quality. The tendencies found in GHL ( M2 ) , NOH and NARH require regular and repeated QC trials.
( 3.2 ) Quality Control ( QC ) Trial
Table 4 is the sum-up of the QC trials carried out on the equipment at different infirmaries. The kVp truth trials show conformity with acceptable bound in GHL ( M1 and M2 ) and PSH while NOH and NARH show non-compliance with acceptable bound of 5 % . As respects the kVp consistence, similar tendency is found in the infirmaries as those found in kVp truth.
In footings of timer truth, it is postulated that exposure clip straight affect the entire measure of radiation emitted from an X-ray tubing. Therefore, an accurate exposure timer is critical for decently exposed radiogram and sensible patient radiation exposure. Both GHL and PSH met the the acceptable variableness bound. Since the timer truth in NOH and NARH are above the bound of acceptableness, it is expected that the radiation dosage delivered to the patient will be higher than the expected value required to bring forth the movie. Furthermore, the one-dimensionality of tubing current ( ma ) and beam alliance of both NOH and NARH fell abruptly of the acceptable bound of 10 % and 3 % severally. Regulation of X-ray tubing filament temperature ( along with the exposure clip find the quality of X raies in the X-ray beam ) is done with millampere picker in an X-ray generator. The beam limitation system is required for modulating the size of the X-ray field country. The mechanism controls the sum of patient anatomy exposed to radiation beam ( Papp, 2002 ) . This plays a cardinal function in patient dose and image contrast. The addition in country increases the production of the scattered radiation, hence higher patient dosage and wellness hazard.
The non-compliance of optical radiation field and radiation field congruity may stem from the displacement in mechanism that moves the shutter, doing improper public presentation. This leads to higher patient dosage and repetition images ( consequence in more movies being used and more disbursals ) .
( 3.3 ) Forces Distribution
The saloon chart in figure 4 shows the distribution of forces. It indicates that two classs of forces are losing ; Radiation Protection Officer/ Medical Physicist and Record Officer. The tendency is similar to the earlier work reported elsewhere ( Oluwafisoye et al. , 2009 ) . The tendency shows that radiation protection of the patients, visitants and forces is non the preoccupation of the direction of the infirmaries investigated. The absence of the record officers indicate that record maintaining at the infirmaries is far from being equal. A record maintaining system is necessary to document the quality control processs, the figure of culls and other activities traveling on at the X-ray units of the infirmary.
( 3.4 ) Visual/ General Observations
The consequence of ocular observations is presented in table 5. It shows that all the basic constituents inspected were functional except LED index on the control panel found in GHL ( M2 ) . Table 6 shows the general observations carried out at assorted infirmaries investigated. Columns 1 and 2 show that the chief door taking to the X-ray room is non lead-lined. Columns 3 and 4 indicate that merely NOH has efficient 2nd door and lead-lined. The cells of the four infirmaries are efficient. This indicates that the interior decorator of the console put in topographic point equal steps that prevent the technicians from immaterial beams during exposures. The doors to the units lack automatic control, connoting that during the exposure the doors do non shut automatically as a consequence, controlled entree to the country where radiation exposure may be taking topographic point is non ensured. Lead apron was non provided in NARH. Nevertheless, the lead apron provided in GHL was non efficient. Regulation for good pattern stipulates that lead aprons and baseball mitts should be available in the radiographic room and have a lower limit of 0.5 millimeters of lead tantamount thickness ( Papp,2002 ) . It is besides apparent that technique charts were losing in all the units, an indicant that technique parametric quantities are chosen at random by the radiographers responsible for the exposure of the patient. This could take to hapless matching of patient size and technique parametric quantities.
Furthermore, warning visible radiation was non provided in any of the units to warn visitants or other forces of the exposure traveling on in the X-ray room. The forces monitoring badge was merely available in NOH, bespeaking that forces dose supervising in GHL, PSH and NARH are non-existent.
( 3.5 ) Dose degree
Consequence of environmental dose monitoring at the chosen locations within and in the immediate environment of each of the X-ray units investigated is presented in table 7. The consequences in all the five units indicate that the dose rate measured at the sofa are by and large really high. At the border of the cell the dosage rates recorded are greater than the background dosage rate by a factor of 7, 20, and 10 in GHL ( M1 ) , PSH and NARH, severally. The dose rate measured within the cell is comparable to the background. This status is safe for the radiographer ; nevertheless, the dose rate is high within the entryway door in GHL ( M1 ) and NARH, it is greater than the background dosage rate by a factor of 6 and 7.5 each. In add-on, the dose rate measured at the waiting anteroom of the patients is comparable with the background dosage rate in PSH and NARH, but higher than the background dosage rate by a factor of 10 in NOH. The high dosage rate experienced in NOH could be attributed to damaged door of the X-ray units. Another possible account for the high dosage rate at the waiting anteroom is the direct nexus between the anteroom and the X-ray machine. It is interesting to observe that there were no escapes experienced in the five X-ray units investigated as reported in the earlier survey carried out in Nigeria ( Oluwafisoye et al. , 2009 ) .
Apparently, this present survey is the first QC trial and environmental monitoring attempts carried out in the five X-ray units in four infirmaries investigated. This is an indicant that the consequences are preliminary against which future measurings could be compared. Besides, the usage of thermoluminescent dosemeters ( TLD ) for the forces monitoring has ne'er been undertaken in the five units. Personnel monitoring is indispensable, since there is a nexus between the ionizing radiation and coevals of reactive O series [ ROS ] ( Cohen, 2002 ) . These ROS have been implicated in the etiology of over 100 diseases. Radiation is one of the major exogenic beginnings of free groups in adult male and it has been proved that ionising radiation produces ROS in biological system capable of destructing biomolecules such as DNA, lipoids, proteins and saccharide ( Olisekodiaka et al. , 2009 ) . Workers runing X-ray equipment are exposed to long term low doses of ionising radiation which may impact their antioxidant position.
Consequences of the QC trials and monitoring were sent to the direction of the four infirmaries investigated. In Addition, recommendations on the necessity of regular QC trial were forwarded to each infirmary for necessary actions.
( 4 ) Decision
Quality control trials of five X-ray units are undertaken with intent of safety and dose optimisation in the X-rays Centres investigated. The ages of three out of five machines are good over 10 old ages. In add-on, the divergence of the measured kVp from set value on the control panel varied among the infirmaries. Two out of the five machines complied with the needed criterion of pattern, while three exceeded the demand. The QC trial carried out on kVp truth and consistence show non- conformity in two infirmaries. The distribution of forces show that, the preoccupation of the authorization of the X-ray unit investigated was the quality of the radiogram produced at the disbursal of safety of the patient. The fluctuation in the end product of the assorted tubing is an indicant that doses among the infirmaries differ. In each of the X-ray units investigated there was no specialised installation to execute pediatric scrutinies and movie screening.