Skin Dose Measurements from Conventional X-Ray Equipment in Sudan

Transcription

1 Journal of Biomedical Image Processing Nov., Vol. Iss., PP. 7-7 Skin Dose Measurements from Conventional X-Ray Equipment in Sudan Alnazier O. Hamza, Mohamed O. Khider, Nuha O. Saeed, Sara A. Mohammed, Yosra E. Mohammed, Department of Biomedical Engineering, Faculty of Engineering, University of Medical Sciences and Technology P.O. Box 8, Khartoum, Sudan,,, Department of Biomedical Engineering, College of Engineering, Sudan University of Sciences and Technology Khartoum, Sudan Abstract-X-ray is an electromagnetic radiation located at the low wavelength end of the electromagnetic spectrum. X-ray technology is used in health care for visualizing bone structures and other dense tissues such as tumors. A radiological examination is one of the most important diagnostic aids available in the medical practice. It is based on the fact that various anatomical structures of the body have different densities for the X-rays. Skin is the quantity of radiation delivered to the skin surface or absorbed by the skin. The risk to the individual from a single radiographic examination is very low. However, the risk to a population is increasing by increasing the frequency of examination. For this reason, many international organizations put limitations for s during radiographic examination as well as s during their work life. Because of the importance of applying these limitations, this research was conducted. This research was intended to measure the skin for both s and s in the field of X-rays machines in hospitals of Sudan to examine the compliance of the limitations to the standard ones. Using Thermo Luminescent Dosimeter (TLD), the skin was measured for s at 9 X-ray units in Khartoum state hospitals. The calculations of the were performed at Radiation & Isotopes Centre Khartoum (RICK) using TLD analyzer. The result of our research shows that % of the X-ray machines emit unacceptable s for s and s. Keywords- Skin Dose; Dosimeters; Thermo Luminescent Dosimeter (TLD); Diagnostic Reference Levels; Conventional X-Ray; TLD Analysers I. INTRODUCTION X-rays are electromagnetic radiations like visible light. But, because of their greater energy, they are able to penetrate materials that absorb or reflect visible light. Discovered in 89, X-rays are widely used in medical, dental and chiropractic diagnosis as well as in medical therapy, veterinary practice, industry and research. When used for medical diagnosis, X-rays pass through the human body and are recorded on X-ray film or other imaging media. X-rays absorbed by the body during medical procedures release energy to produce ionisation. Ionisation is the release of electrons from atoms and molecules which may then produce chemical and biological change. An exposure to X-rays does not make a person radioactive nor is there any residual radiation in the body as a result of an X-ray exposure. Short term effects from the radiation s used in most diagnostic X-ray procedures should not occur (although there have been reports elsewhere of radiation burns to the skin as a result of lengthy invasive procedures). Long term concerns include the possible induction of cancer, foetal and hereditary effects, but the long term risk to an individual is low. Diagnostic X-rays cannot be considered to be completely without risk, but the risks will vary depending on the procedure. For many examinations, the radiation is no greater than the we receive from natural background radiation in one year. Nevertheless, X-ray examinations should be limited to those which are necessary for proper management of a 's condition. Examinations which are unlikely to be of clinical benefit should be avoided. Some pre-employment X-ray examinations, particularly those of the lumbar spine, are of dubious value. Examinations involving exposure of the lower abdomen or pelvis in pregnant women need particular consideration by the referring practitioner. The benefit of diagnosing a 's condition from a properly conducted and clinically necessary X-ray examination should far outweigh the small risk involved []. Accurate assessments of surface and superficial s in radiotherapy can provide valuable information for clinical consideration to avoid near-surface recurrence while at the same time limiting severe skin toxicity, especially for breast and head-and-neck treatments. Dose at the surface is primarily due to electron contamination from the flattening filter, beam modifiers and air. The magnitude of the surface depends on the field size, angle of beam incidence, air gap and the use of beam modifiers []. The irradiation of any particular portion of skin depends on rate, irradiation time, and beam geometry. It is not surprising that more inclusive measuring means, in the sense of providing information about the spatial and temporal distribution of absorbed, give better dosimetric estimates than simpler means do []. As a result of the bad influence of these radiations in the long run, both on a personal level or on society as a whole, this - 7 -

2 Journal of Biomedical Image Processing Nov., Vol. Iss., PP. 7-7 study was conducted to determine the s given in the Sudan for the s and staff in the field of radiation, and then to examine the conformity of the limits with the standard ones. II. BASIS OF DIAGNOSTIC RADIOLOGY A radiological examination is one of the most important diagnostic aids available in the medical practice. It is based on the fact that various anatomical structures of the body have different densities for the X-rays. When X-rays from a point source penetrate a section of the body, the internal body structures absorb varying amount of the radiations. The radiation that leaves the body has a spatial intensity variation. The X-ray intensity distribution is visualized by a suitable device like a photographic film. A shadow image is generated that corresponds to the X-ray density of the organs in the body section. The examinations technique varies according to the clinical problem. The main properties of X-rays, which make them suitable for the purpose of medical diagnostic, are the following: The capability of X-ray to penetrate matter coupled with different absorption observed in various materials. Ability to produce luminescence and its effect on photograph emulsions. The X-ray picture is called a radiograph, which is a shadow picture produced by X-rays. The X-ray picture is usually obtained on photographic film placed in the image plane. The skeletal structures are easy to visualize and even the untrained eye lens can sometimes observe fractures and other bone abnormalities []. III. PRINCIPLES OF RADIATION PROTECTION The current radiation protection standards are based on three general principles as follows: Justification of a practice i.e. no practice involving exposures to radiation should be adopted unless it provides sufficient benefit to offset the detrimental effects of radiation. Protection should be optimized in relation to the magnitude of s, number of people exposed and optimized for all social and economic strata of s, keep s As Low As Reasonably Achievable (ALARA principle). Dose limitation, on the other hand, deals with the idea of establishing annual limits for occupational exposures, public exposures, and exposures to the embryo and fetus[]. In order to measure the s of the exposed radiation, dosimeters or Personnel dosimeters are used. Personnel dosimeters refer to the monitoring of individuals who are exposed to radiation during the course of their work. Personnel dosimetry policies need to be in place for all occupationally exposed individuals. The data from the dosimeter are reliable only when the dosimeters are properly worn, receive proper care, and are returned on time. Proper care includes not irradiating the dosimeter except during occupational exposure and ensuring proper environmental conditions. Monitoring is accomplished through the use of personnel dosimeters, such as the pocket dosimeter, the film badge or the thermo luminescent dosimeter. The radiation measurement is a time integrated, i.e., the is summed over a period of time, usually about months. The is subsequently stated as an estimate of the effective equivalent to the whole body in msv for the reporting period []. A. Dosimetry IV. DOSIMETERS Doses for medical diagnostic procedures can vary widely between equipment and facilities. Numerous surveys have demonstrated that, for typical procedures, the difference in radiation s can be as wide as a factor of to. For interventional procedures, this difference can be even wider. The dosimetric quantity kerma, K, relates to the transfer of radiant energy from ionising particles (photons) to the kinetic energy of secondary ionising particles (secondary electrons). It is defined as the quotient of detr divided by dm, where detr is the sum of the initial kinetic energies of all the charged particles liberated by the uncharged particles in a mass element dm: The unit of kerma is J kg -. The special name for the unit of kerma is gray (Gy). K = de tr / dm () Entrance surface air kerma, Ka,e is the air kerma on the X-ray beam axis at the entrance surface of the or phantom, including the contribution from backscattering. For a single exposure, it is equal to the product of the backscattering factor and the incident beam air kerma. Single Ka,e values add up to a cumulative entrance surface air kerma only if the beam position and orientation relative to the are fixed during the procedure. The values from different projections are not additive, but virtual sums are used in some applications in the same way as the virtual cumulative Ka,i values [7]

3 Journal of Biomedical Image Processing Nov., Vol. Iss., PP. 7-7 The most reliable dosimetry quantities commonly used in diagnostic radiology to give an indication of the typical that is being delivered to an average adult are the Entrance Surface (skin) Dose (ESD), including backscatter for simple X-ray projections, and the Dose Area Product (DAP) for complex examinations [8], [9]. The ESD, in particular, is recommended as the most appropriate dosimetry quantity for simple X-ray projections since it meets the three basic conditions set out by the International Atomic Energy Agency (simple to measure, permits direct measurement on during the examination, and is representative of the received by the ). It is also recommended by the Commission of the European Communities (CEC) in the document on quality criteria for the most common radiographic images. In addition, the measurement of ESD permits easy comparison with published diagnostic guidance or reference levels []. In diagnostic radiology, the use of surface air kerma limits is not sufficient since these limits are usually set at a level high enough so that any s greater than the limit is clearly unacceptable. But this limit does not help in optimizing s. For this reason, the concept of Diagnostic Reference Levels (DRLs) is introduced, instead of using maximum limits. B. Thermo Luminescent Dosimeter (TLD) Monitoring Some inorganic phosphors emit light (i.e., fluorescence) when exposed to an ionizing radiation. This fluorescence can be immediate or delayed. In some cases, the crystalline forms of these materials store some of the energy imparted to them from ionizing radiation and release that energy as light when the temperature of the crystal is raised. Under carefully controlled conditions of heating, the amount of light produced is directly proportional to the amount of ionizing radiation to which the material is exposed. The reproducibility and linearity of thermo luminescent response are key properties that permit TLD use for measuring ionizing radiation levels in the environment []. In our research TLDs were provided from RICK. For s, TLDs were put in plastic badges and then were put on the s during radiographic procedure in the light field of X-ray. For s we gave s at 9 different departments the TLDs badges. They would wear the TLDs for months, and then the that they receive was measured. C. TLD Analyzer TLD was annealed in degrees Celsius for minutes so that any remaining electrons in the blanks were removed. The TLDs segments were carried by vacuum placer because of the toxicity of these segments. When the ionizing radiation entered the TLDs, the electrons became excited then moved from lower levels to higher levels. When electrons tried to return to the stable state, some remained in the blanks. TLDs were put again in a high temperature for freeing electrons, then photons were produced. After that, these photons would pass through the photo multiplier tube (PMT) to be converted into current (pulse). Finally the s were calculated using the following equations: where: Calibration factor =. Dose (mgy) = measured pulse (ma) / (calibration factor*) () Dose (msv) = Dose (mgy) * () From the two equations above the radiation can be computed. In Equation (), the measured pulse from the TLD is divided by a certain factor, this factor is called calibration factor which is used to compromise the effect of the heat or any environmental conditions in the TLD. As we can see the unit of the is mgy, so in order to get the in msv, we should use the Equation (). V. DIAGNOSTIC REFERENCE LEVELS The purpose of DRLs is to promote a better control of exposures to X-rays. This control must be related to the clinical purpose of the examination. DRLs must not be seen as limits, but instead as guidance to optimizing s during procedures. DRLs are based on typical examinations of standardized or phantom sizes, and for a broad type of equipment. While it is expected that facilities should be able to attain these levels when performing procedures using good methodologies, it is not expected that all s should receive these levels but that the average of the population should. DRLs are useful where a large reduction in s may be achieved, such as for computed tomography (CT) procedures, where a large reduction in collective s may be achieved, such as for chest X-rays, or where a reduction will result in a large reduction in risk, such as for paediatric procedures []. A. Recommended DRL Values Diagnostic reference levels (DRLs) are defined in the Council Directive 97/ Euratom as Dose levels in medical radio - 9 -

4 Journal of Biomedical Image Processing Nov., Vol. Iss., PP. 7-7 diagnostic practice or, in the case of radiopharmaceuticals, levels of activity, for typical examinations for groups of standard sized s or standard phantoms for broadly defined types of equipment. These levels are expected not to be exceeded for standard procedures when good and normal practice regarding diagnostic and technical performance is applied. Thus DRLs apply only to diagnostic procedures in radiology or nuclear medicine and does not apply to radiation therapy []. In conventional radiology, two parameters have been used to express DRLs: the entrance surface (ESD) and the area product (DAP).ESD is the absorbed (mgy) measured in air at the intersection of axis of the X-ray beam and the 's skin surface; ESD includes retro scattered rays. ESD can be easily calculated or even better measured with TLDs or with ionisation detectors placed on the 's body. DAP is the product of the mean absorbed s in air in the section of the X-ray beam in the absence of scattering medium by the section of the beam. Thus DAP unit is Gy.cm. DAP can be easily measured with an ionisation chamber placed at the window of the X-ray [].The parameter used in this research to convey the DRL is the ESD. Table presents representative DRL values for radiographic procedures performed on adults. Table presents DRL values for a -year-old child along with the mean body thicknesses for each examination []. Examination TABLE DRL VALUES FOR ADULTS Entrance Surface Dose (msv) Chest. Thoracic spine Lumbar spine. Abdomen 7- Pelvis - Skull - Ankle.7 TABLE : DRL VALUES FOR A -YEAR-OLDCHILD Examination Entrance Surface Dose (msv) Chest.-. Abdomen.-. Pelvis.-. Skull.8-. VI. RESULTS AND DISCUSSIONS The following diagrams illustrates the calculated s results of s acquired using different TLDs at 9 X-ray departments in Khartoum state. Machine No ().. chest limit=. msv. Fig. Chest X-ray of s measured using TLD and X-ray unit number In the top figure it is obvious that number and received s more than the DRL because there is no calibration for the equipment and lack of Quality Control (QC) programs. - -

5 Journal of Biomedical Image Processing Nov., Vol. Iss., PP. 7-7 Machine No () chest limit=. msv Fig. shows the chest X-ray of s measured using TLD and X-ray unit number In the above figure it is apparent that all s received s more than the DRL because there is no calibration for the equipment and a lack of QC programs. Machine No () chest limit=. msv Fig. Chest X-ray of s measured using TLD and X-ray unit number From Fig. above it is clear that number received s more than the DRL because there is a lack of QC programs. Machine no () 7 limit Fig. X-ray of s measured using TLD and X-ray unit number As seen in Fig. all s received s less than DRL because there is calibration for the equipment and good training for the s. - -

6 Journal of Biomedical Image Processing Nov., Vol. Iss., PP. 7-7 Machine No () 7 limit Fig. X-ray of s measured using TLD and X-ray unit number Fig. implies that all s received s less than DRL because there is calibration for the equipment and good training for the s. Fig. Lumbar spine X-ray of s measured using TLD and X-ray unit number Fig. explains that all s received s less than DRL because there is calibration for the equipment and good training for the s. Machine No (7) ankle limit=.7 msv Fig. 7 X-ray ankle of s measured using TLD and X-ray unit number 7 In the above figure it is noticeable that number received s more than the DRL because there is a lack of QC - -

7 Journal of Biomedical Image Processing Nov., Vol. Iss., PP. 7-7 programs. Machine No (8) ankle limit=.7 msv Fig. 8 X-ray ankle of s measured using TLD and X-ray unit number 8 In the ahead figure, it is observable that received s more than the DRL, because there is no calibration for the equipment and a lack of QC programs. Fig. 9 X-ray ankle of s measured using TLD and X-ray unit number 9 In the above figure it is evident that number and received s more than the DRL because there is no calibration for the equipment and a lack of QC programs. Fig. to Fig. illustrate the results of of s acquired using different TLDs at 7 X-ray departments in Khartoum state. The results show that all s received s less than the limit. The subsequent figures summarize the overall results obtained after conducting the research on hand. Hospital No () (msv) 's limit= msv/months Fig. X-ray of s measured using TLD, they work in hospital number - -

8 Journal of Biomedical Image Processing Nov., Vol. Iss., PP. 7-7 Hospital No () (msv) 's limit= msv/months Fig. X-ray of s measured using TLD and they work in hospital number Hospital No () (msv) 's limit= msv/months Fig. X-ray of s measured using TLD, they work in hospital number Hospital No () (msv) 's limit= msv/months Fig. X-ray of s measured using TLD, they work in hospital number - -

9 Journal of Biomedical Image Processing Nov., Vol. Iss., PP. 7-7 Hospital No () (msv) 's limit= msv/months Fig. X-ray of s measured using TLD, they work in hospital number Hospital No () (msv) 's limit= msv/months Fig. X-ray of s measured using TLD, they work in hospital number Hospital No(7) (msv) 's limit= msv/months Fig. X-ray of s measured using TLD, they work in hospital number 7 - -

10 Journal of Biomedical Image Processing Nov., Vol. Iss., PP acceptable unacceptable. machine machine machine9 machine machine machine machine machine7 machine8 Fig. 7 Summary of measurements from 9 machines in Khartoum region.... acceptable.. hospital hospital hospital hospital hospital hospital hospital7 Fig.8 Summary of X-ray measurements for s in 7 hospitals From Figs. 7 and 8, we can deduce that.% of the X-ray machines are emitting unacceptable s for s. In the other hand, % of the s received s less than the limits. We can conclude our results by making some comments: Any measurement was done only once for each in each facility because the measurements were obtained from exposure not from a phantom. Besides these s were examined once, so there is no way to have multiple measurements. Each facility has its own TLDs, and due to the research budget limitations, we could not afford to buy a single TLD for our measurements, so different TLDs were used at different facilities. VII. CONCLUSION The purposes of this research are to measure the skin from both s and s in the field of radiology in hospitals to examine the compliance of the measured s with the standard ones and to show deviations - if existed- from the standard measurements. In addition, the required and necessary recommendations for proper work, and better and s health have to be clarified, because if the s absorbed exceed a certain limit, this can expose both s and s to cancer hazards. Results analysis was performed. The analysis showed that recommended DRL values in some of results was not achieved in a number of hospitals in Sudan. That returns to many reasons including: There is no calibration procedures performed for X-ray equipments. There is no good training for technicians working in the field of radiology, besides the lack of awareness of radiation s and s limitation. Lack of qualified operators and engineers due to lack of training. - -

11 Journal of Biomedical Image Processing Nov., Vol. Iss., PP. 7-7 There is no routine service program for the X-ray equipments. By putting the above points into consideration, i.e. by conducting regular calibration and quality control programs to the X- ray equipment in Sudan, as well as carrying out appropriate training for s on the equipment and raising their knowledge about radiation safety procedures, we can guarantee the safety for both s and s in our hospitals. REFERENCES [] Environmental Health Directorate (EHD), Department of Health, How Safe are Medical X-rays? Environmental Health Guide, Western Australia,. [] S. H. Hsu, P. L. Roberson, Y. Chen, R. B. Marsh, L. J. Pierce, and J. M. Moran, A Assessment of skin for breast chest wall Radiotherapy as a function of bolus material, Physics in Medicine and biology, vol., pp. 9-, 8. [] S. Balter, D. W. Fletcher, H. M. Kuan, D. Miller, D. Richter, H. Seissl, and T. B. Shope, Techniques to estimate radiation to skin during fluoroscopically guided procedures, The American Association of Physicists in Medicine (AAPM(,pp. -,July. [] R. S. Khandpur, Biomedical Instrumentation: Technology and Applications, st ed., USA: McGraw-Hill Professional,. [] S. B. Grover, J. Kumar, A. Gupta, and L. Khanna, Protection against radiation hazards : Regulatory bodies, safety norms, does limits and protection devices, Indian journal of radiology and imaging, vol., iss., pp. 7-7,. [] F. J. Thompson andw. J. Ashworth, X-ray physics and equipment, st ed., Oxford, UK: Blackwell Scientific Publications,9. [7] M.Toivonen, T. Komppa, Report on methods of evaluating local skin in interventional radiology, Report of the DIMOND III working group of Work, Package., pp. -9,. [8] B. M. Moores, Radiation measurement and optimization, The British Journal of Radiology, vol. 78, iss. 9, pp. 8-88,. [9] B. F. Wall, Response to Radiation measurement and optimization, The British Journal of Radiology, vol. 79, iss. 9, pp. - 7,. [] E. K. Ofori, W. K. Antwi, D. N. Scutt, and M. Ward, Patient Radiation Dose Assessment in Pelvic X-ray Examination in Ghana, OMICS Journal of Radiology, vol., iss. 8, pp. -,. [] E. J. Antonio, T. M. Poston, and B. A. Rathbone, Thermoluminescent Dosimeter Use for Environmental Surveillance at the Hanford Site, 97, Washington, USA:Pacific Northwest National Laboratory,. [] Council Directive 97/ Euratom, Health protection of individuals against the dangers of ionizing radiation in relation to medical exposure, and repealing Directive 8//Euratom, Official Journal of the European Committees, No L 8/-7, 997. [] Radiation protection 9, Guidance on diagnostic reference levels for medical exposure, Office for official publications of European Community, Luxembourg,. Alnazier Osman Hamza, PhD, is an Associate professor of biomedical engineering at the University of Medical sciences & Technology. He received his BS degree in medical imaging from Sudan University Sciences and Technology; his MS in medical physics and biomedical engineering from Surry University UK; and PhD in medical physics and biomedical engineering from the University of Natal, South Africa. Mohamed Omer Khider, M.Sc., is a lecturer and the Head of Research and Development Centre at Faculty of Engineering, University of Medical sciences & Technology. He has a first-class Bachelor of Science degree in Biomedical Engineering from the University of Medical Sciences and Technology, Faculty of Engineering, Department of Biomedical Engineering, Khartoum, Sudan, his M.Sc. in Biomedical Engineering is from College of Graduate Studies, University of Medical Sciences and Technology, Khartoum, Sudan. Nuha Omar Saeed, B.Sc., is a biomedical engineer. She has bachelor of Sciences degree in Biomedical Engineering from Sudan University Sciences and Technology, Khartoum, Sudan. Sara Ahmed Mohammed, B.Sc., is a biomedical engineer. She has bachelor of Sciences degree in Biomedical Engineering from Sudan University Sciences and Technology, Khartoum, Sudan. Yosra Elfadhel Mohammed, B.Sc., is a biomedical engineer. She has bachelor of Sciences degree in Biomedical Engineering from Sudan University Sciences and Technology, Khartoum, Sudan