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TRAINING IN RADIOPROTECTION AT UNDERGRADUATE AND POSTGRADUATE LEVEL AT THE SCHOOL OF PHARMACY AND BIOCHEMISTRY, BUENOS AIRES UNIVERSITY. R. Bergoc (1), R.A. Caro (1), E.S. Rivera (1), C. Menossi (2). Radioisotopes Laboratory, School of Pharmacy and Biochemistry, Buenos Aires University, 956 Junín St., 1113 Buenos Aires, ARGENTINA. Nuclear Regulatory Authority, ARGENTINA.
INTRODUCTION The advancement of knowledge in molecular and cell biology, biochemistry, medicine and pharmacology which has taken place in the last 60 years is really outstanding. One of the reasons for this fact is the application of radioisotope techniques in these fields. The research on metabolisms, biodistribution of pharmaceuticals, pharmacodynamics, etc., is mostly carried out by means of techniques employing radioactive materials. Radioisotopes and radiations are frequently used in medicine both as diagnostic as therapeutic tools. Thus, in Nuclear Medicine, many diagnostic procedures are done with radiopharmaceuticals; their production and control are sometimes the responsibility of biochemists. Also, radiometric assays are today a routine method to determine many hormones in endocrinology and in clinical medicine. Receptor determination and characterization is a steadily growing methodology used in clinical biochemistry, pharmacology and medicine. For these reasons we consider of great importance to teach radioisotopes methodology at the undergraduate and graduate level on medicine and biomedicine and give to the future professionals, graduates and technicians who assist this professionals an adequate knowledge of this current tool. At the same time it is necessary to harmonize the use of these methodologies with enviromental preservation. At present, the School of Pharmacy and Biochemistry of the University of Buenos Aires offers four different Courses on Methodology of Radioisotopes in which the Radiological Protection is focalized under different aspects: 1) A Course for students at the undergraduate level, in the Biochemistry cycle; 2) A Course for post-Graduate in Medicine, Biochemistry, Biology, Chemists or other disciplines related to the health. 3) Another one for professionals wishing to up-date their skills; and finally, 4) one for Technicians in Nuclear Medicine and/or Biomedicine.
OBJECTIVES AND COURSES ORGANIZATION 1) Undergraduate level: At the undergraduate level the subject Methodology of Radioisotopes was teached from 1960. We began to teach some elementary notions of radioactivity and measurement techniques included in the Physics syllabus for students of Biochemistry. Consecutive up-dating of the Biochemistry syllabus added Radiochemistry as an optional subject and since 1978 Radioisotope Methodology has been a compulsory subject for biochemistry students, which is given at Radioisotope Laboratory in the first term of each year. Its objective is to provide theoretical and practical knowledge, even though this knowledge does not imply the possibility of obtaining a licence to work with radioactive materials. Since 1975 also Pharmacy students have been taught some very elementary notions of radioactivity in the Physics courses at the same Department and also some notions of Radiopharmacy at the Pharmaceutical Technology Department. Undergraduate students have 84 hours of theory and 56 hours of practical work. In order to estimate the degree of knowledge acquired in the practical work students must take two partial examinations and one final examination. Radioprotection is one of the main topics both in the course and in the exams. The theoretical syllabus include a first part of basic and general concepts and a second part where all the specific application of radioisotopes to the biochemical area are studied, maintaining a continuos up-date of new methodologies. The topics include: basical knowledges of atomic nuclei, radioactive decay mechanismes, interaction of particles and radiation with the matter, instrumentation, biochemical applications of radioisotopes with special emphasis on radioimmunoasay and 125I protein labelling, radioprotection and safe handling of radioisotopes in the laboratory, radioactive wastes management, envirommental criteria, national and international regulations, radiobiology. The objectives of the training in radioprotection at undergraduate level in Biochemistry are: ¾ to give guide lines for the adequate application of radioactive materials and the radioprotection philosophy, with special emphasis on biochemical-clinical practices and on radioisotopic techniques utilized in different research areas. ¾ the planification of professional practices with an adequate training of the personnel. 1
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the optimization of procedures. also we emphasize the aspects related to the specific future activities of the students attending the Course. Students tend either to neglect or to enhance radiological risks associated with the work with radioisotope due to lack of knowledge. In this sense, students are led to acquire adequate criteria by the analysis of different practical situations. Today, one of the most common practices with radioisotopes in Argentina at biochemical level for the diagnosis of different diseases is the labelling of molecules with 125I, and their utilization on different radiometric assays. If we analyze the decay scheme of 125I, we note that more than 95 per cent of the photon emissions are X-rays of approximately 27 KeV, originated as a consequence of orbital electron reaccommodations after electron capture and/or internal conversion. The remaining fraction (5%) corresponds to γ-rays of approximately 35 KeV. Therefore, the principal risk is not the irradiation of workers: if we calculate specifically the Dose Equivalent Rate received by an operator working with 5 mCi (185 MBq) of 125I at a distance of, for example, 20 cm during the labelling of proteins or other molecule: Γ = 0.06 R m2 / h Ci
fλ = 0.96.
d = 20 cm.
Therefore, dH/dt will give 0.072 mSv/h. This basic approach allows to analyze particular situations. For example, if we consider that glass tubes commonly used for radiolabelling have a wall thickness of approximately 1 mm with a µ equal to 3.54 cm-1, then e-µx will be equal to 0.7, Thus, the dH/dt received by the operator will be approximately of 0.05 mSv/h. Taking into account that the duration of the practice is about two hours (including the purification of the labelled compound), and that in this type of laboratories the same biochemist generally performs two labelling per month, the Dose Equivalent, H, is equal to 2,4 mSv per year. Under these conditions, the practice can be considered as radiologically safe (the International Committee on Radioprotection, ICRP, and Argentine Nuclear Regulatory Authority established the limit for workers at 10 Sv per 5 years). For instance, if we shield the working place with ordinary lead bricks 5 cm thick. Since µ is 422 cm-1, eµx will be 10-916 !, which implies a clearly overestimated attenuation factor and, instead, the eventual utilization of these lead bricks could cause accidents with contamination since the manipulation would be very uncomfortable for the operator. 2) Post-graduate Course on Methodology of Radioisotopes: In the case of the Course at post-graduate level, it begun in 1962 and at present 1233 professionals have pass their examinations. Posgraduate attendants have 122 hours of theory and 100 hours of practices. In order to estimate the degree of knowledge acquired the professionals take two partial examinations and one final examination. The syllabus include: Nuclear stability. Binding Energy. Nuclear models. Radioactive decay mechanisms and kinetic equations. Particles and radiation interaction mechanisms. Instrumentation: ionization chamber, proportional counters, Geiger-Müller tubes, mono and bidimensional radiochromatogram analysers, solid and liquid scintillation spectrometry, solid state detectors, radioautography (whole sample, histologic, cellular), absolute activity determination. Detection efficiency. Statistics of radioactivity measurements. Production of radioisotopes and radiopharmaceutical materials. Purity control and criteria. Activation analysis. Biochemical applications of radioisotopes. Radiometry: radioimmuneassay and receptor characterization. Medical applications: image diagnosis and the adequate radiopharmaceutical drugs for each study. Regarding radioprotection the syllabus includes: Definitions, Magnitudes and Units of: Dose, Dose Equivalent, Collective Dose Equivalent, Exposure. Internal and external sources. Shielding. General aspects of radioprotection: justification, optimization and dose limitation. Biological effects of ionizing radiation. Radiobiology. Classification of working areas. Occupational radiological protection. Internal and external contamination. Monitoring. Instruments for radioprotection. Regulation for the transportation of radioactive materials. International and national regulations for the utilization of radioactive material in Argentina. (optional or mandatory). In some aspects the teaching of radioprotection is formative and in others informative, because the approval of the asignature does not habilitate to ask from the Nuclear Regulatory Authority the authorization to work with radioactive material. With respect to the laboratory practical experiments, the profesional presents at the Course attend the following practices: ¾ Instrumentation: ionization chamber, proportional counters, Geiger-Müller tubes, mono and bidimensional radiochromatogram analysers, solid and liquid scintillation spectrometry, detection efficiency, statistics of 2
P-10-144 radioactivity measurements. An special emphasis is given to equipment calibration. Decay schemes analysis. Criteria for detection and radioprotection of different nucleides on basis of the radioactive decay mechanism. ¾ Production of radioisotopes and radiopharmaceutical materials. Purity control and criteria. Labelling of radiopharmaceuticals with 99mTc. . ¾ Labelling of different proteins with 125I. Purity control. ¾ Radioimmunoanalysis. ¾ Receptors: characterization and quantification. ¾ Radioprotection practices include: Internal and external sources. Shielding. General aspects of radioprotection: justification, optimization and dose limitation. Classification of working areas. Occupational radiological protection. Internal and external contamination. Monitoring. Instruments for radioprotection. Radioprotection criteria for work with: 99mTc, 125I, 32P, 59Fe, 51Cr and other nucleides. Differences between contamination and irradiation. Calculus. The objective of the training in radioprotection at post-graduate level consists in: ¾ Acquisition of criteria for the adequate application of the radioprotection philosophy, independently of the previous university training of the graduate students participating in the course, emphasizing the importance of this practice as well as the potential environmental impact that it may have ¾ Planification of professional practices with an adequate training of the personel involved in order to keep the doses as low as it is reasonably possible (ALARA principle), ¾ Calculation of the Absorbed Doses by the perssonel during the practices. ¾ adequation of the procedures taking into account: elements to be utilized, detail of techniques, overcome of eventual difficulties, time required for the practice to be completed, eventually associated radiological risks for patients and workers. ¾ The training in radioprotection aspects is theoretical and practical and very intensive, encompassing: dosimetric magnitudes and units, internal and external dosimetry of 125I, 131I, 201Tl, 99mTc, 60Co and other isotopes, qualification of areas, working conditions, contamination barriers, shielding; justification, optimization and dose limits; radioactive wastes; responsibilities and legal aspects, national and international legislation. The intensity of the training is in accord with that required by each professional in their speciality; In the case of physicians 99mTc is the mostly used radionuclide in Argentina. Its Γ value is 0.08 Rm2/hCi, quite similar to that of 125I. However, in the case of 99mTc, activities of 0.5 to 1 Ci are used which obviously increase the dose due to irradiation. For biochemists, the calculus of Dose is same that for 125I already seen. ¾
3) Post-graduate up-dating Course on Methodology of Radioisotopes. This Course is done from 1992 and update the knowledge in a modular form according to needs of professionals attending. 4) Course for Technicians in Nuclear Medicine: This Course is done from 1997 and emphasize fundamentally the operational aspects of radioprotection at technician level: radioactive columns elution, injection of radioactive drugs to patients, decontamination of areas, procedure with radiactive waste.
RESULTS Results are quite satisfactory: 95% of registered students approved their respective levels; the requirement to pass the examination is the acquisition of criteria according to each professional/technician responsibility. Since the beginning of the Course for undergraduate until 1998, a total of more than 4700 students have passed their examinations. The students demonstrated an unusual interest in the course that led us to increase the number and extension of practical works. In the case of Course for post-graduates, the radioprotection training shown that professionlas acquires criteria for the adequate application of the radioprotection philosophy, calculation of Absorbed doses and adequation of procedures taking into account devices to be utilized, detail of the techniques, time requiered in each practice and eventual associated radiobiological risks. Since the begining of this course until 1999, a total of 1233 professionals have passed their examinations. It should be mentioned that the graduates are chosen not only taking into account their academic profiles but also considering the necessity of their respective working institutions to count with well trained personnel in radioisotope techniques. We receive mainly biochemists, physicians, chemists, biologists, engineers, pharmacists among others. Figure 1 illustrates the number of the professionals along the years. The preponderance of biochemists and physicians is evident. 3
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1200
Total Number
1000
800
Bioch. Phys. Others Total
600
400
200
0
60-64
65-69
70-74
75-79
80-84
85-89
90-94
95-99
Time (years) Figure 1. Total of the attendants at Methodology Radioisotopes Course.
Figure 2 show the increasing trends of the number of professionals physicians as a function of time, with a notorious peak in 1996-1999. It can be observed in the last years that the number of physicians is steadily growing. This is due to the expansion of medical diagnosis with radioisotopic techniques, principally in cardiology. The participating professionals come from principally (88%) Buenos Aires and its surroundings. In the last few years the proportion of graduates from the provinces is increasing. This fact should be due to a growing interest in smaller cities to have, at least, certain minimal radioisotope using health care practices, both in medicine and biochemistry. During these years 10 professionals from different Latin American countries (Perú, Venezuela, Colombia, Brasil and Uruguay) have passed their examinations.
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% PROFESSIONALS / PERIOD 90.0 80.0 70.0 60.0 BIOCHEMISTS PHYSICIANS OTHERS
50.0 40.0 30.0 20.0 10.0 0.0 60-65
66-70
71-75
76-80
81-85
86-90
91-95
96-99
Figure 2. Proportion of attendants at post-graduate Methodology Course
CONCLUSIONS The application of radioisotopes and radiations to professional activities is currently common in modern science and technology. However, these activities must be carried out in the framework of radiological safety and in harmonization with the ecosystem. The four training courses we describe are organized with this purpose in mind and a background of 40 years in teaching activity.
REFERENCES 1. 2. 3. 4. 5. 6.
J.Dutreix, A.Desgrez, B.Bok and C.Chevalier. In: Física y Biofísica: radiaciones. Edit. AC, Madrid (1980). P. Sprawls, Jr. In: Physical Principles of Medical Imaging. Aspen Publishers Inc., Maryland, USA (1987). M.Tubiana, J.Dutrieux and A.Wambersie. In: Introduction to Radiobiology. Taylor & Francis, London, New York, Philadelphia (1990). Annals of the ICRP, Publication 60. Recommendations of the International Commission of Radiological Protection. Ed. H.Smith, Pergamon Press, USA (1991). G. Gordon Steel. In: Basic Clinical Radiobiology.Arnold, London (1997). M.A.Statkiewicz-Sherer, P.J.Visconti and E.R.Ritenour. In: Radiation Protection in Medical Radiography. Mosby Inc. St. Louis, Missouri (1998).
Corresponding author: Prof. R.M.Bergoc, Radioisoropes Laboratory, School of Farmacy and Biochemistry, Junin 956 St.-1113 Buenos Aires, ARGENTINA. Fax: +54 (11) 964 8202; Tel: +54 (11) 964 8277 E-mail:
[email protected]/
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