The Focuse Film Distance Used By Radiographers On Mobile Chest X-rays - Coursework Example

Title- Improving Emergency Radiological Investigations- A Review BACKGROUND Radiology is an important investigative tool in the modern medicine but it is responsible for both somatic and hereditary effects pertaining to its use of ionizing of radiations. In real terms there is no optimum dose that exists which can be called safe as the effect may be get manifested sometimes at a very low dose levels as well. This is due to the fact that radiations have the tendency to behave randomly. Hence the current IAEA guidelines do quote a dosage but emphasizes that the dose should be kept as low as reasonably attainable. This kind of mandatory medical exposure has been recorded to be the biggest radiation exposure to the human community today. And it has been found statistically to be relevant as both somatic and the genetically significant dose equivalent (GSD). The data from different countries especially UK highlights it the best. The statistical data here represents 31% of the somatic and 9% of the total GSD. These amount to 95% and 85% respectively of the man made contribution. The largest dose contribution, among man made radiation sources, comes from medical irradiation of which diagnostic radiology accounts for the 90%. Since X-rays are such a large contributor to radiation hazard it is imperative that it be minimized as much as possible. Therefore, it calls for its use to be both warranted and optimized. The pros and cons of benefit and the risk involved should be dispassionately weighed. To this effect knowledge of the dose received during each x-ray procedure is essential for the assessment of radiological hazards which helps stimulate the awareness in radiological personnel on what are safe and acceptable norms in radiation protection practices. Chest x-ray’s are the most commonly used to diagnose infections and other trauma conditions and even cancer. Hence its relative contribution to the population radiation dose is considerable. Hence to control the actual exposure to radiation it is important to measure dose received by patients from such a common radiological examination. INTRODUCTION Mobile Chest X-Rays have been a crucial aid to detecting several acute conditiond where either the patient cannot be moved to a radiology department or where there is an increased risk of spreading of infection to the rest of the community. In fact such units are being used on a regular basis in the emergency departments as well as ICUs. A mobile X-ray invariably reduces the time to result as compared to the regular radiology x-ray. However, mobile X-ray films have always remained of inferior quality and hence unnecessarily expose the staff to added risk of radiation exposure. IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology specifies a minimum skin-focus distance of 30 cm in case of general radiography (except dental) and fluoroscopy with X Ray mobile equipment. In a very recent publication it has been found that the radiation leak is much higher of the current limit of {mSvh(-1)} in mobile units as compared to the sedentary ones. In spite of the fact that the a number of companies and vendors were changed in this survey study it was realized that it was not the manufacturing which was faulty but the methodology used in shielding tubing which was at fault. (1) Hence it has now become mandatory that certain proper interventions be carried out improve the procedure and bring it under the acceptable norms of radiation control. Research has shown that increasing film-focus distance (FFD) from the traditional 100 cm to 130 cm could be an effective method of reducing dose whilst maintaining image quality. However there is a wide variation of the techniques employed, equipment performance and radiation dose in different hospitals. On the contrary some researches have pointed out from their own experience that the saving in effective dose at increased SIDs (Distance from the source to the centre of the x-ray image) rather modest and maintains results as well. IAEA also brings to the forefront the importance of optimization of patient radiation protection. This calls for a periodic evaluation of doses and image quality apart from an understanding by the operators of interdependence between technical parameters, dose and image quality. It is felt that there is an urgent need to undertake comprehensive review of the literature, research material on the subject, so that evaluations could be made of the potential possibility of increasing the film-focus distance for reducing dose, radiation hazards while ensuring image quality. AIMS AND OBJECTIVES The aim is to evaluate the potential possibility of increasing the film-focus distance for reducing dose, radiation hazards while ensuring image quality. The Objective is Undertake review of the literature, research material on the subject Undertake survey of the radiology practices in some of the hospitals to understand the practical difficulties faced by operators in the use of X-ray mobile equipment for variable film-focus distance. PLAN OF INVESTIGATION Focus film distance (FFD) is the distance between the X-ray source and the film in diagnostic radiography. Review of literature on the subject includes a comprehensive look-in for the published research about increasing FFD that ensures reduced dose and radiation hazards without impairing film quality. Publications from the archives of the Radiation Protection Dosimetry, Oxford University Press, British Journal of Radiology, and International Commission on Radiological Protection shall be studies and discussed. 1990, Recommendations of the ICRP, (2) and inputs from many other such publications shall be scanned and material collected and collated for the project. “Increasing film-focus distance (FFD) from the traditional 100 cm has been shown to be an effective method of reducing dose whilst maintaining image quality. In particular, previous work increasing the FFD from 100 to 130 cm for lumbar spine examinations demonstrated an effective dose reduction of 44 %.”(3) Another quote by the same authors “As for our claim that the dose reduction to be obtained by an increase in SID is modest, we stand by this.” In this case quoted by the authors positive results are obtained by changing the SID from 75 cm to 200 cm SID, an extreme case not likely to occur in practice. The authors of another study found that effective dose reduction can be easily obtained by increasing SID from the commonly used 100 cm to 125 cm is nearly 10% or so and is fairly acceptable to improve the apparatus. (4) Thus a further review of literature on the same lines is proposed to further enhance the background of the study. It is also proposed that if dose-reducing measures are going to be useful clinically, a thorough understanding of the effect of specific measures on patients of varying size, state of health, gender and so on must also be established. This will help in before widespread implementation. Mathematical modeling would also need to be extensively employed so as to sort out these difficulties. It is further proposed to undertake survey of the radiology practices in some of the hospitals to understand the practical difficulties faced by operators in the use of X Ray mobile equipment for variable film-focus distance because there is a wide variation of the techniques employed, equipment performance and radiation dose in different hospitals. For the purpose a Questionnaire /data sheet shall be prepared and made available to operators for specific answers and their comments how the image clarity compares vis a vis increase in film-focus distance (FFD). The periodic measurement (at least once a year) of the entrance patient dose (or similar quantity), a periodic evaluation (at least once a year) of the image quality and the comparison with the guidance (or reference) levels and with values from previous controls will make comparisons quite useful. The use of the appropriate screen-film combination, the "fastest" compatible with the type of image that is looked for, may be recommended to guarantee the lowest patient dose so that comparisons do not falter for reasons of differing quality of the screen films. The information thus collected will be collated and compared and attempt made to ascertain in practical terms, the advantage gained in terms of dose reduction, hazards reduction while maintaining image quality for variable film-focus distance. The results of the findings shall be submitted to the authorities for scrutiny and approval. It is of utmost importance that the participants are given a feed back so that they know their short comings. Visits shall also be made to the hospitals to apprise them of the findings STEPS IN INVESTIGATIONS 1. A comparison of technique and entrance skin dose- Distribution of forms in which the radiographers shall fill up the details of their technique, methodology, equipment, exposure factor, focus to skin distance, the angle of inclination between the patient torso and the machine, the age, height and weight of patients were recorded. The type and model of the machine would be maintained as far as possible. Standard calculations will be used for ESD and FSD. 2. Image quality- For this different curves, will be made between two consecutive exposures for the same patient and evaluated by different radiographers and clinical interpretations. The results shall be recorded on tables and graphs and a follow up study performed if needed. DISCUSSION The hospital data in various countries across the globe shows that there is a lot of variation existing in the technique, ESD, FFD, ESAK, Tube potential of the equipment used. Since there is an increased radiation protection monitoring and audit even for diagnostic radiology in most developed countries a lot of procedures and protocols have been laid to minimize this danger. In this review and a planned survey we will measure the entrance skin exposures (ESEs) of the standard size patients for the routine radiographs in the some hospitals that will help us study and observe the wide disparity of the patient dose in the similar X-ray examination in the different hospitals. In any case the literature review has already proven that the in use mobile X-ray machines are prone to generate higher levels of radiations due to the design as well as technology constraints. Some of the other contributing factors to the observed variation in the patient exposure are the use of suboptimal imaging equipment, poor choice of technical factors and/or incorrect film processing procedures. It is suggested that a significant reductions in the radiation dose is possible without adversely affecting the image quality primarily by increasing the FFD which is highly effective in reducing the ESE by 30 to 40%. Almost all will be using almost similar combination of technology in their mobile apparatus. Their development drugs would also be the same so that the patient dose exposure becomes an out put due to the choice of exposure factors, FFD and the X-ray units output. In general, the FFD to be used in this study would be both short (the one in use) and long (i.e. proposed). Shorter FFD has high skin entrance dose. It is so because when the FFD increases the beam becomes harder which in turn leads to air filtering out the weaker beam from the x-ray spectrum. The high skin entrance dose on the bases of the short FFD generally used among operators has some kind of impact on breast and thyroid. Thus this situation is not very healthy for otherwise weaker patients as it increases the radiation-induced risk to these radiosenstive organs. Dose measurements done in previous studies have established that breast and thyroid glands were exposed to the the highest dose from chest x-ray compared to other radiological procedures. Radiation exposure has a cumulative effect as the dose repetition increases exposure and hence generates higher risk for the patient. This then brings forth the issue of considering seriously the risk and benefit of indiscriminate use of radiation for any and all purposes. Since in this study we are more concerned about mobile units we will focus primarily on FFD which in earlier studies has given an indication of reducing entrance exposure considerably. In addition the working condition of radiological equipment is among the most critical factors known to influence dose to patients in any radiological investigation. Most mobile units are under tremendous load due to their usage in emergency set ups. In cognizance with this regular quality assurance of machines and radiological procedures are important to reduce dose to patients. Apart from the FFD the quality of film employed, applied mAs, kilo-voltage selected and the skill of the operator are also important causal features for patient dose reduction. Not only should they be kept in mind so also be stringently followed and updated. SOME NEWER SYSTEMS Some of the newer systems made with the idea of reducing the radiation problems and the safety of both the operator as well as the patient have the following features: The manufacturing company (Daltec Occupational Health Services Inc) has recently launched mobile unit which according to the data presented is compareable to a main system. It claims that this mobile unit is capable of performing 14” X 17” chest x-rays with the same quality as normally seen. The unit is usually used in conjunction with pulmonary function tests in industries where exposure to coal dust, silica dust, grain dust and asbestos are present. It may also be used in situations where tuberculosis is an issue. Equipment description-This equipment is made up of a Picker Clinix C processor with Daylight loader and unloader. The entire patient area of the unit is lead lined and has been inspected by Radiation Health. There has never been scatter radiation with this type of unit and workers are exposed to the same amount of radiation as 20 minutes in the sunlight. The quality control is maintained by expert radiographers, as claimed by the company. It is advantageous as it definitely reduces time to result as well as time to access. References 1. Tsalafoutas IA. Excessive leakage radiation measured on two mobile X-ray units due to the methodology used by the manufacturer to calculate and specify the required tube shielding. Br J Radiol. 2006 Feb;79(938):162-4. 2. Publication 60. Oxford, UK: Pergamon, 1991 3. P. C. Brennan*, S. McDonnell and D. O'Leary of UCD School of Diagnostic Imaging, Herbert Avenue, Dublin 4, Ireland 4. J Poletti and D McLean, Health and Community Studies, Unitec, Private Bag 92025, Carrington Road, Auckland, 1003 New Zealand, Adjunct A/Prof University of Sydney, School of Medical Radiation Sciences, Faculty of Health Sciences, University of Sydney, PO Box 170 Lidcombe NSW Australia 2141 5. Awwad KH. Radiation oncology, Radiobiology and physiological perspectives, 1990;2. 6. Coregy CE. Radiation risks with diagnostic x-ray; Radiology, 1976;123:447 Read More