the radiation which is produced by the x-ray tube and is directed to the patient, .... thick lead apron absorbs 66% of the scattered radiation. If a 0.5mm thick lead ...
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EEXOT Τόµος 63, (1):41-46, 2012
Practical Rules for Occupational Radiation Exposure Protection in Orthopaedic Surgery
HATZIS C.1 BRILAKIS A.E.2, EFSTATHOPOULOS N.3 1
Technologos Radiology, Radiology, Radiology Department, General Hospital “Asklepion” Voula Eidikefomenos Second Orthopaedic Clinic, University of Athens 3 Anaplirotis Professor II Orthopaedic Clinic, University of Athens 2
ABSTRACT The use of intraoperative fluoroscopy has been increased the last few years, rendering the use of C-ARM as a precious tool for the orthopedic surgeon. Since his residency years, the orthopaedic surgeon realize the value of fluoroscopy, while during complex operations extended use of radiation is required. This data, combined with the known biological effects of radiation, create legitimate queries for the occupational radiation exposure to the orthopaedic surgeon. Moreover, sometimes the surgeon should face the perceptions of the remainder personnel of the operating room during an operation. These perceptions, in certain cases, touch upon the limits of exaggeration. This article is based on the study of the literature and has two objectives. On one side, it tries to underline the basic knowledge that an orthopaedic surgeon should have concerning the ionizing radiation, while on the other hand it pinpoints certain practical rules that an orthopaedic surgeon should apply in order to operate with safety, minimizing the danger from the use of radiation.
INTRODUCTION The use of fluoroscopy during orthopedic operations 1 has been increased during the last few years . The modern Μαιling address: Emmanuel Brilakis Aristophanes 18, 18533 Piraeus Mobile: +30 6973717069 E-mail: Emmanuel.Brilakis @ gmail.com
minimal invasive techniques, as well as the application of intramedullary nails, require the use of radiation for imaging, rendering fluoroscopy an essential tool for the orthopedic surgeon. However, the use of radiation is accompanied with objective risks. Since his early residency years, the orthopaedic surgeon realizes the value of fluoroscopy. He should be sufficiently informed in order to be able to use it with safety, without misimpressions or even “radiation 2 fear” . These could be eliminated with the application of fundamental principles of Radioprotection. This term encompass the rules and the processes which target to the protection of the employee, the general public and 3 the environment from ionizing radiation . The aim of this article is to pinpoint the essential practical knowledge concerning the use of radiation during orthopedic surgeries and to help for the safer use of fluoroscopy.
RADIATION TYPES X-rays are part of the electromagnetic spectrum, characterized by small wavelength and high frequency. X-radiation is divided into the primary beam, which is the radiation which is produced by the x-ray tube and is directed to the patient, the scattered or secondary radiation, which results from the interaction of primary beam with patient’s body and the leakage radiation, which is leaked by the x-ray tube and is negligible concerning the 4, 5, 6 . Primary beam is responsible for scattered radiation the imaging, while scattered radiation for the biological effect. This is the radiation from which the surgeon and the personnel of operating room should be protected (Figure
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Figure 1. X-radiation types.
Figure 2. C-ARM device.
Figure 3. Proper C-ARM positioning. X-ray tube should be placed under the operating table.
Figure 4. When X-ray tube is placed over the operating table, surgeon exposure is tenfolded.
1). Its energy is smaller compared to primary beam’s energy. Scattered radiation is propagated to every direction but with no isotropic manner, as far as primary energy beam values of 60Kvp to 90Kvp are concerned, which are usu4 ally used for imaging in hip, femur, tibia, shoulder, elbow . Secondary radiation is increased in proportion to the size of the field and the thickness of the anatomical subject, while it is decreased as long as the distance between the surgeon and the patient is increased. In one meter distance the intensity of the scattered radiation is 1.000 1,7 times smaller than the respective of primary beam . The “inverse square” law is referred to the radiation which is produced by spot source (primary radiation) and no to the
scattered radiation. Nevertheless, in two and three meters distance from the scattering point (patient skin) the results are similar, since the intensity of the radiation is reduced 8 4 times and 10 time respectively .
MEASUREMENT UNITS When a radiation beam interacts with certain material, changes of its energy are observed. Specifically, a part of beam’s energy is absorbed by the human tissues and phenomena like ionizations, excitations or other phys5 iochemical and biological phenomena take part inside them . Absorbed dose (D) determines the sum of energy that is absorbed in specific quantity of material. Gray (Gy) is the
43 Α. ΧΑΤΖΗΣ και συν. ΠΡΑΚΤΙΚΗ ΕΦΑΡΜΟΓΗ ΚΑΝΟΝΩΝ ΑΚΤΙΝΟΠΡΟΣΤΑΣΙΑΣ ΣΤΑ ΟΡΘΟΠΕ∆ΙΚΑ ΧΕΙΡΟΥΡΓΕΙΑ
Figure 5. Image intensifier should be placed as near to the patient as reasonable achievable.
Figure 6. When the image intensifier – patient distance is increased, surgeon exposure is duplicated.
Figure 7. Isoexposure profile of scattered radiation during fluoroscopy (lateral view). The safer position for the surgeon is by the side or behind of image intensifier, where surgeon exposure is decreased by 97%.
Figure 8. Isoexposure profile of scattered radiation during fluoroscopy (lateral view). Surgeons should avoid standing by the side of the tube, because his exposure is multiplied.
unit of measurement in the international system of units (SI), honorary to the American Physicist; which represent the deposition of energy equal to 1Joule in 1Kg of matter (1Gy=1J/Kg). Dose equivalent (HR) concerns biological systems and focuses especially on human exposure. For the same amount of dose equivalent but for different type of
radiation (x-rays, γ-rays, neutrons etc) the biological effect is different. Thus, equivalent dose is the dose absorbed, corrected by the weighing factor for specific radiation type (WR), which depends on the type and the quality of the radiation used (HR=WR x D). It is measured in Sievert (Sv), honorary to the Swedish Physicist Rolf Sievert. The value
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Table 1. Percentage attenuation of radiation for different primary beam’s energy values and for different 7 protective apron thicknesses. Energy that is used more often marked with bold letters Lead apron thickness
Lead apron weight
Percentage radiation attenuation
(mm)
(Kg)
Energy
Energy
Energy
50KVp
75KVp
100KVp
0.25
1.4 – 4.5
97%
66%
51%
0.5
2.7 – 6.8
99.9%
88%
75%
1
5.4 – 11.3
99.9%
99%
94%
Table 2. Practical application of radioprotection PRACTICAL RADIOPROTECTION Use as low as reasonable achievable fluoroscopy time Use pulsatile and not continuous fluoroscopy Use high resolution fluoroscopy only if necessary Last image hold Proper use of protective equipment Face to the tube during fluoroscopy Maintain as high as reasonable achievable distance from the patient Lateral views: Stand next to image intensifier Be familiar with the geometric properties of the scattered radiation The image intensifier should be as near to the patient as reasonable achievable Image zoom only if necessary
of this factor for X-rays is 1. Human tissues are radiation sensitive; each one of them is characterized by a weighting factor for the specific tissue (WT). Effective dose (E) is the sum of the equivalent dose which a tissue or an organ receives, multiplied by the specific weighting factor for this tissue or organ (E=SWT x HR) and is measured also in Sv. Effective dose expresses the magnitude of the damage that radiation causes to the DNA of specific tissue by giving rise to mutations or cellular death. The weighed factor for genitals is 0.20, for bone marrow, intestine, lungs and stomach is 0.12, for the bladder, breast, liver, esophagus and thyroid gland is 0.05 and for the bones and the skin 5,9 is 0.01 respectively .
RADIATION EXPOSURE TO THE ORTHOPAEDIC SURGICAL TEAM An experimental study of Mehlman and DiPasquale calculated the dose which is accepted by each person which
RESULTS IN Dose decreasing Dose decreasing (x4) Dose increasing (x2) Fewer views Dose decreasing Proper positioning Dose decreasing Proper positioning Better positioning Dose decreasing Dose increasing (x2)
is found inside the operation room during fluoroscopy used for orthopedic operations. They used a pelvic phantom for the fluoroscopic target and they measured the radiation exposure for the surgeon, his assistant, the scrub nurse and the anesthesiologist. The torso of the surgeon, found in distance 30cm, is exposed to 0.2mSv/min, his hands to 0.29mSv/min and his eyes to 0.1mSv/min. The corresponding value for a surgeon assistant who was found in double distance (60cm) is 0.06mSv/min, 0.1mSv/min and 0.06mSv/ min respectively. The exposure of scrub nurse’s hands was measured to 0.02mSv/min while was null as far as her torso (distance: 1meter) and her eyes were concerned. Null exposure was also measured for the anesthesiologist (distance: 1.5meter) in all of his/her body (torso, hands, 10 eyes) . The aforementioned values were experimentally measured and referred to exposure without the use of protective equipment. It is obvious that the surgeon is mostly exposed to the radiation, while the body part which 11 is mainly exposed is his hands . In extension of this study and according to the superior occupational exposure limits
45 Α. ΧΑΤΖΗΣ και συν. ΠΡΑΚΤΙΚΗ ΕΦΑΡΜΟΓΗ ΚΑΝΟΝΩΝ ΑΚΤΙΝΟΠΡΟΣΤΑΣΙΑΣ ΣΤΑ ΟΡΘΟΠΕ∆ΙΚΑ ΧΕΙΡΟΥΡΓΕΙΑ
Table 3. Guidelines for proper dosimeter use PROPER DOSIMETER USE qTorso dosimeter is placed over the lead apron qDosimeters which are placed under the lead apron are grey and specially marked on the sending lists qDosimeter is placed with the code number facing ahead (not from the side of the body) qThe month of valid use is written on the back side of the dosimeter, in order to be easily checked qDosimeters should not be covered qIn cases of emergency, personal dosimeter can be dispatched for measurement ( contact with ΕΕΑΕ) qPastilles of dosimeter are very sensitive. Should not be touched or be placed in warm or luminous environment qDosimeter should be protected from mechanical damage qDosimeter is personal. Every employee should put on his own, according sending lists qDosimeters are changed monthly. Dosimeters used 3 months ago cannot be measured.
posed by the International Commission on Radiological Protection (ICRP), which are 20mSv per year for the torso and 500mSv per year for the hands, Singer made logical calculations. He reported that each orthopedic surgeon can participate into 200 procedures of intramedullary nailing each year until reaching the limit of exposure concerning his torso, or 333 procedures if the limit of the hands exposure is taken into account, provided that protective 1 equipment is used .
PROTECTIVE EQUIPMENT The correct use of protective equipment routinely has great importance. The protective aprons that are usually used are manufactured of Lead (Pb) as thick as 0.25mm and 0.5mm or of equivalent thickness Xenolite, a lighter ecological material. These aprons cover the body from the neck to the knees (Table 1). For the usual energy range that is used in the fluoroscopic orthopedic procedures, a 0.25mm thick lead apron absorbs 66% of the scattered radiation. If a 0.5mm thick lead apron is used, the corresponding 7 percentage reaches 88% . Thyroid gland shields as thick as 1,3,12 0.5mm reduce the scattered radiation up to 80% . Thyroid gland is a very sensitive tissue. Therefore, the use of lead apron without thyroid gland cover is incorrect since is non protective. Special radio-protective glasses, that are seldom 1,3,12 . used, can absorb 85% to 90% of the scattered radiation It should be highlighted that eyes are the unique body part that have threshold dose (0.5Gy). Higher dose exposure 13 may cause cataract . Considering the aforementioned data, we realize that the use of protective equipment is not enough in order to offer absolute protection from the scattered radiation, for the usual used energy range. Orthopedic surgeons should have an energetic role as far as their protection is concerned. The following rules should be applied routinely in order to maximize his protection. The use of wheeled screens should be encouraged. A 1mm thick wheeled screen can absorb photons up to 150Kvp.
The combined use of this equipment with a lead apron is 6,7 capable to nullify the scattered radiation (over 99%) .
C – ARM POSITIONING C-ARM (Figure 2) is a portable diagnostic device for imaging using radiation-X during operations. It is constituted by the arm and the portable imaging station. The arm which is C-shaped contains the x-ray tube on one side and the image intensifier on the other side. X-rays tube has a stationery anode for longer durability and a collimator, which limits the beam in the field of image intensifier. Image intensifier contains a compact and rotating camera and a mesh from carbon fibers for scattered radiation reduction. The arm can be moved, angled and rotated in various directions (at length, at height, or panoramic). The portable imaging station is usually constituted by two monitors, one for live fluoroscopy and one for holding the last image.
Anteroposterior or posteroanterior views (face) During these views, C-ARM should be placed in such a way that the tube would be always under the operation table (Figure 3). The major amount of scattered radiation is produced on the level where the beam interacts with patient skin. When the tube is over the operation table (Figure 4) the dose that the surgeon receives is dramati1,7,8 cally increased (by ten times) . Nevertheless if the tube is placed over the operation table, protective curtains should be used. Image intensifier should be as near to the patient as possible (Figure 5). Height increasing results in multiplica14,15 tion of the dose that surgeon accepts (Figure 6) . On the contrary height reduction, when combined with a backward step of the surgeon and the proper use of the 7,8 protective equipment practically “nullify” his exposure . Lateral views (profile) Studying the isoexposure profile (Figure 7), the saf-
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est place for the surgeon during fluoroscopy, is by the 7,8 side or behind of image intensifier . Sometimes it is not practical for the surgeon to take this position, due to patient positioning or other reasons. However he should avoid standing by the side of x-rays tube (Figure 8), a fault that is often observed.
DOSIMETRY According to the Greek Regulation for Protection from Radiation (official journal of the Hellenic republic 216/B/6.3.2001) and the European Directive (96/29), the annual dose limit for occupational whole-body radiation exposure is 20mSv/year or 100mSv for five consecutive years. However, in this case the effective dose should not exceed 50mSv for each year. The equivalent dose limit for the lens 16 is 150mSv per year and for the hands is 500mSv per year . According to the Legislation, dosimetry is obligatory for workers which are expected to be occupationally exposed on dose higher than 6mSv annually (type A workers). If the fundamentals of radiation protection are applied, the dose that the surgeon would receive annually is lower than 2mSv on average. This value for the remainder personnel of operating room is expected to be lower than 0.5mSv 7 per year , meaning that dosimetry is not required. Since 2000, thermoluminescence dosimeters (TLD) are used replacing the film type dosimeters. They are based on the phenomenon of thermoluminescence and are provided by the Dosimetry Department of Greek Atomic Energy Commission (ΕΕΑΕ). The lower dose which they are able 17 to detect is 0.01mSv . Table 3 reports guidelines as far as the correct use of dosimeter is concerned.
CONCLUSIONS The latest years, the use of intraoperative fluoroscopy in orthopaedics has been increased, resulted in increased radiation exposure of orthopedic surgeons. Therefore, precautions should be taken for minimizing this exposure aiming to the biggest protection against the biological effect of ionizing radiation. The routine application of practical rules during orthopaedic procedures is the key to this direction. In Table 2 a list such rules are reported. They are practically applicable and they don’t influence the quality of imaging or the operative outcome. On the contrary, if the surgeon ignores them, he exposes himself to unprovoqued risk. In conclusion, the continuous effort that orthopaedic surgeons make for improving their technique should be combined with proper and safer use of radiation.
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2005; 13(1):69-76. 2. Khan F, Ul-Abadin Z, Rauf S, Javed A. Awareness and attitudes amongst basic surgical trainees regarding radiation in orthopaedic trauma surgery. Biomed Imaging Interv J. 2010; 6(3):e25. 3. Oikonomidis S. Occupational Radiation Protection and Interventional Radiological. Greek Committee of Atomic Energy, available in: http://www.eeae.gr/gr/docs/edu/_ aktinoprostasia.pdf. 4. Koutroubis G. Radiation Phisics 1. Department of Radiologic Technologists. Athens: OEDB. 1989. 5. Koutroubis G. Radiation Protection. 1st edition. Athens: Lihnos publications. 2000. 6. Zamanis K, Katsifarakis D, Tampaki E. Principles of Radiologic Technology. Β΄ Class of ΤΕΕ. Athens: OEDB. 2001. 7. Bushong SC. Radiologic Science for Technologists. Physics Biology and Protection. 9th Edition. St. Louis, Missouri: Mosby Elsevier. 2008. 8. Dowd SB, Tilson ER. Practical Radiation Protection & Applied Radiobiology. 2nd edition. Philadelphia. Saunders. 1999. 9. Uzoigwe CE, Middleton RG. Occupational radiation exposure and pregnancy in orthopaedics. J Bone Joint Surg (Br) 2012; 94(1):23-27. 10. Mehlman CT, DiPasquale TG. Radiation exposure to the orthopaedic surgical team during fluoroscopy: “How far away is far enough?” J Orthop Trauma 1997; 11:392-398. 11. Back DL, Hilton AI, Briggs TW, Scott J, Burns M, Warren P. Radiation protection for your hands. Injury 2005; 36(12):1416-1420. 12. B. Schueler. Personel Protection During Fluoroscopic Procedures. American Association of Physicists in Medicine, Annual Meeting 2003, available in: http://www.aapm.org/ meetings/03AM/pdf/9790-14134.pdf. 13. International Commission Of Radiological Protection (ICRP). Statement on Tissue Reactions. Last update: April 21st of 2011, available in: http://www.icrp.org/page.asp?id=123. 14. International Commission Of Radiological Protection (ICRP). Radiological Protection in fluoroscopically guided procedures performed outside the imaging department. Last update: May 18th of 2011, available in: http://www.icrp.org/docs/ Radiological%20protection%20in%20fluoroscopically%20 guided%20procedures%20performed%20outside%20 the%20imaging%20depa.pdf. 15. Giordano B. Grauer J. Miller C. Morgan T. Rechtine II G. Radiation Exposure Issues in Orthopaedics. J Bone Joint Surg (Am) 2011; 93:e69(1 – 10). 16. National printing-house – Official Journal of Hellenic Republic (F.E.K.). FEK 216B, 6-3-2001. 17. Greek Atomic Energy Commission (ΕΕΑΕ) - Department of Occupatinal Dosimetry, available in: http://www.eeae.gr/gr/ index.php?menu=1&fvar=html/dosi/_dosi.
