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Radiation Safety


RADIATION SAFETY FOR ORTHOPAEDIC SURGEONS

Although it has not been possible to conduct a controlled study to confirm the hypothesis, anecdotal evidence suggests that orthopaedic surgeons are in a high risk category for malignancies with a likely contributor being exposure to ionising radiation during surgical procedures.

The practice of orthopaedic surgery is dependent on the use of ionizing radiation. Therefore, orthopaedic surgeons should be continually aware of the dangers of chronic exposure to X-rays. Despite this, some orthopaedic surgeons continue to act in a cavalier manner when using radiation equipment.

This booklet seeks to raise the awareness of orthopaedic surgeons using ionising radiation to the potential dangers of its use and to provide guidelines for orthopaedic surgeons in the use ionising radiation in the operating theatre.

  1. THE NATURE OF IONISING RADIATION
    1. CHARACTERISTICS OF RADIATION

      Radiation can be divided into two categories:

      * Ionising (Capable of producing ions) such as alpha-rays, beta-rays, gamma-rays & X-rays

      * Non-Ionising such as microwaves, radio waves, ultraviolet, infrared, laser and ultrasound.

      X-Rays are ionising radiation and two types are emitted from an X-ray tube;

      * Bremstrahlung X-rays that are produced when charged particles (eg. electrons) decelerate . These are the main X-rays emerging from an X-ray tube that produce the image.

      * Characteristic X-rays that are produced when an orbital electron in an atom drops to a lower energy state. These usually constitute a small fracture of the X-rays from an X-ray tube.

      X-rays are electromagnetic radiation with the following features:

      * They behave as uncharged particles called photons

      * They are not affected by electric or magnetic fields

      * They travel at the speed of light

      * They travel in straight lines

      A source or X-rays obeys the inverse square law. This law states that the intensity of X-rays (photons per unit area) is inversely proportional to the square of the distance from the X-ray source. This is a very important principle in the protection of both staff and patients, because in practice it means that when the distance from the X-ray source is doubled, the exposure is divided by four and inversely the nearer the higher the exposure by a factor of four.

       

    2. INTERACTIONS OF X-RAYS WITH MATTER

      X-rays interact with matter through excitation and ionisation, depending on the energy transferred to the orbital electron. For excitation to occur, the electron must be given sufficient energy to raise it to a new orbital, whereas for ionisation the electron must be given sufficient energy to overcome its binding energy and thus be liberated from atom.

      The energy of X-rays is expressed in electron volts (eV). An electron volt is the energy that an electron acquires when it jumps across a potential difference of one volt.

      When X-rays interact with matter, they are either absorbed or scattered of pass through the matter to emerge in an attenuated state. (the attenuated X-rays emerging from a patient are converted to light to ultimately produce the X-ray image).

      X-rays are scattered at the entry point on matter and some do not penetrate, but others do penetrate and are scattered within the matter. The scatter levels from the patient emitted during exposure are the main source of radiation doses received by staff during fluoroscopy. Tableside fluoroscopy receives among the highest occupational radiation exposure within the health system. The scatter radiation is highest near its source, the beam entry point on the patient.

      X-rays are attenuated in matter such that their intensity is reduced exponentially as the thickness of the absorber increases. This exponential reduction in intensity, besides depending on the absorber thickness, also depends on the energy of the X-rays and the atomic number and density of the absorber material.

      Half-Value Layer (HVL) is the thickness of the absorber required to reduce the intensity of the original beam by one-half. Again, HVL depends on the X-ray energy and the density and atomic number of the absorber material. In human tissue the HVL is about 3cm.

      • ATTENUATION THROUGH PATIENTS

        The basis of a medical image is the relative attenuation of an X-ray beam due to different tissues, organs and structures. Low photon energies and high atomic number absorbers generate little scatter and produces high contrast in the X-ray image, but at the expense of increased patient dose. At higher photon energies the scattering process is the most common interaction between X-ray and body tissues and is responsible for almost all scattered radiation.

        Radiographic image contrast is less with scattering reactions. The scattered photons detract from the final image and contribute no useful information. Scatter can be reduced by:

        • Decreasing kilovoltage (kVp) of the X-ray unit that determines the range of X-ray energies (keV)

        • Decreasing the thickness of the part examined.

        • Decreasing the field size of the X-ray beam.

      • RADIATION UNITS

        Exposure refers to the X-ray beam and is a measure of the quantity of ionisation, produced in air, by X-ray or gamma radiation per unit mass. It is a property of the beam and is not measuring absorbed energy. The unit is Coulomb per kilogram (C/kg).

        Air Kerma is often used as an alternative to radiation exposure. Kerma is an acronym for Kinetic Energy Released per unit Mass. The unit is Gray (Gy). An air Kerma of 1Gy represents the transfer of 1 Joule of energy from the radiation beam to air and it translates roughly to tissue and hence to skin absorbed dose.

        Absorbed dose is a measure of the amount of energy imparted to matter by ionising radiation per unit mass of irradiated material. The unit is Gray (Gy).

        Equivalent dose is a quantity that takes into account the biological damage caused by different types of radiation. The SI unit is the Sievert (Sv). The sub-unit millisievert (mSv), one thousandth of a Sievert, is used as a rule because of the large size of the Sievert.

        Equivalent Dose = Absorbed Dose x Radiation Weighting Factor.

        Effective dose is a quantity introduced for radiation projection purposes. It correlates better with the overall harmful effects caused by exposure to the various types and distribution of ionising radiation. The SI unit is the Sievert with the millisievert used more often.

        Effective dose = Sum of equivalent dose x Tissue Weighting Factor for all exposed tissues.

        Radiation dose limits. The annual effective dose limit for occupational exposures from whole body irradiation in 20mSv per year averaged over five years with no more than 50 mSv in any one year.

        To prevent all deterministic effects to the individual, the annual dose limit to any single tissue, except the lens of the eyes is 500mSv per year. The limit to the lens is 150 mSv per year.

  2. HAZARDS OF RADIATION

    1. Ionisation effects

      Ionising radiations interact with matter through excitation and ionisation. The ionising process causes biological damage either by direct or indirect action.

      Direct Action - Acting directly by disrupting molecular bonds of sensitive cellular material (DNA or cell membranes)

      Indirect Action - Acting indirectly by first ionising or exiting water molecules which then form oxygen – containing free radicals that are able to disrupt molecular bonds.

      Most of the long term effects of radiation are caused by the indirect action. Organs where cells divide rapidly are generally more sensitive to radiation damage. Most radiation damage is thought to be repaired by cellular mechanisms. Some cells die and a very small fraction remain viable with altered function. The likelihood and the severity of the effect produced depend on various factors such as dose, dose rate, chemical environment, metabolic, rate and others.

    2. Biological effects

      For radiation protection purposes, these effects are divided into two main groups.

      • Somatic effects, or those that occur in the exposed individual. They include both stochastic and deterministic effects.

      • Hereditary effects, or those that occur in the exposed individual’s descendents. These effects are regarded as being stochastic.

      Biological effects of ionising radiation are classified as either stochastic or deterministic.

      Stochastic (probabilistic) effects are those for which there is a probability of an effect occurring in an exposed individual. It is assumed that there is a relationship between dose and the probability of an effect. A threshold is not thought to exist and stochastic effects can not be ruled out at low levels of exposure. This implies that there is no safe dose below which such an effect can not occur. It means that any radiation dose will amplify the cancer risk and that all radiation must be kept to a minimum. Stochastic effects may result when irradiated cells are modified rather than killed. Such effects may not manifest themselves until many years after the radiation exposure.

      The risk factors provide the probability of inducing a fatal malignant disease from the irradiation of tissues such as the red bone marrow (leukemia effect), bone, lungs, thyroid and breasts. The greater the radiation dose received, the greater the individual risk of a radiation induced effect.

      Deterministic effects are those for which the severity of the effect varies with the dose, and for which a threshold may occur. While stochastic effect may occur, deterministic effects always occur above a certain dose level.

      Deterministic effects are specific to particular tissues, for example non-malignant damage to the skin, cataract to the lens of the eye, and gonadal cell damage leading to impaired fertility.

      If the dose is greatly in excess of the threshold dose, the effects will occur in a relatively short period after irradiation. If the dose is not greatly in excess of the threshold dose, many of the resulting effects are of a temporary nature and reversion to normal conditions usually occurs.

    3. Radiation risk in perspective

      It is assumed that the impact of radiation on human health is proportional to the dose of radiation received for both large and small doses. The dose is cumulative over a lifetime.

      Radiation does not produce a unique set of health effects. The effects that can be attributed to low level radiation are also known to be caused by a large number of other agents.

      The most important late effect of radiation is cancer, which is often fatal. The fundamental process by which radiation induces cancer is not fully understood. However, a greater incidence of cancer has been observed in people who had been exposed to high doses of radiation previously. Few persons who have been so exposed actually contract cancer, but each person has the probability of contracting it, and this depends largely on the dose received.

      A large international cohort study substantiates the risk of cancer with low dose radiation.

      Their results show that the excess relative risk for leukemia, excluding the chronic lymphatic form, was 1.93 per Sv and for other cancers 0.97 per Sv. On this basis 1-2% of deaths occurring in 407391 people may have been attributable to radiation. The overall accumulated dose recorded per person was 19.5 mSv. This is a rather low dose. It roughly equates to the accumulated dose to a patient who had a CT lumbar spine, a standard CT chest scan and a bone scan. Dosimeters on the outside of registrars’ thyroid shields have recorded 13mSv over only 3 months. The average annual risk of death from radiation exposure at the rate of 5 mSv per year is 1 in 16 000 and at a rate of 20 mSv per year 1 in 4 000.

      Malignancy may occur even at low doses, but the exact dose-response relationship is not accurately known. The most frequent induced cancers are female breast, thyroid, lung and the alimentary tract. There is an increased probability of a future malignancy in organs that are irradiated especially the breast and bone marrow. If a population of one million is irradiated with 10mSv effective dose, it will cause 200 more cancers.

      These results suggest that low dose radiation may induce cancer and reinforce the need for radiation education and protection protocols.

    4. Sources of radiation

      Natural Background Radiation

      Everyone is exposed to natural background radiation. It forms the highest radiation dose received by most people. The constituents of this natural background are:

      • Cosmic radiation which varies with altitude and latitude.

      • Terrestrial gamma radiation from naturally occurring radioactivity.

      • Inhaled radioactive radon gas from decay chains of uranium & thorium.

      • Radioisotopes ingested in the diet.

      The effective dose from natural sources in areas of average background will be ± 2.8 mSv per year but may be a high as 8 to 20 mSv per year in some areas of the world. An intercontinental return air trip will add an additional dose of 0.12 mSv.

      Medical Radiation

      Although much lower than natural background radiation for the population as a whole, medical radiation rates second as a source of radiation and is by far the greatest artificial source of radiation.

      While we cannot control the natural background radiation people are subjected to, we can influence the amount of radiation from X-ray investigations.

      Comparing the typical effective dose from diagnostic procedures to the equivalent period of natural background radiation may provide some food for thought. An X-ray of the cervical spine is equivalent to 1.6 weeks of natural background radiation; a pelvis X-ray to 3.2 months; a hip X-ray to 5.6 weeks and an examination of the Lumbar spine to 5.6 months.

      The above put us under obligation to order X-ray examinations only if such an examination will clearly benefit the patient.

  3. Radiation use in Orthopaedic Surgery

    Orthopaedic surgeons rely on technology. As modern practitioners of the art, we need every assistance in patient management. Radiation has become an essential part of our diagnostic work-up, surgical intervention and post-operative management. None of us can practice without it.

    The mobile C-arm image intensifier has become a piece of equipment that is used extensively in the operating room these days. To do so responsibly, we need to be aware of operational considerations that need special attention for fluoroscopic procedures. They are the following:

    • Tube Kilovoltage (kVp):

      This determines the penetration power of the X-ray beam. It is normally 70 – 80 kVp but may have to be increased for large or thicker patients. Increase in kVp increases the radiation dose, and an increase from 70 to 80 kVp will increase the dose by 30%.

      This controls the quantity of radiation emitted per second. An increase in the mA will increase the radiation output and patient exposure, but will also enhance the image brightness.

      Both the kVp and the mA have an influence on the quality of the image as well as on the radiation dose. Increasing both will enhance the image but at the cost of a very high radiation dose. Decreasing both will decrease the radiation dose but will also detract from the image obtained. The ideal is to balance the kVp and mA settings in such a way that an acceptable image is obtained with the lowest radiation dose.

      If the image quality on the monitor is poor in a thin patient, it may be corrected by increasing the mA. For thick patients it is preferable to increase the kVp. This however will increase the radiation output and it may then be necessary to reduce the mA.

      Mobile C-arms are equipped with an Automatic Brightness Control (ABC). With the ABC, both the kVp and the mA settings are varied automatically to produce an acceptable image of whichever part of the body is examined. The kVp and mA settings should be such that the image is just adequate for diagnostic purposes. It is preferable to use the ABC whenever possible.

      It is important to realise that unnecessary improvements to the image quality obtained by increasing the patient dose must be avoided. If unusually high settings are required to provide acceptable images, it indicates a malfunction of the equipment which should be checked.

    • Screening time:

      Increasing the screening time will increase the radiation dose. Therefore a minimum screening time should be used. This is done most effectively by intermittent screening using short bursts of radiation.

      • Do not depress the footswitch continually for long periods;

      • Concentrate your attention on the screen before depressing the switch;

      • Use electronic image recording whenever possible. Examination of the image can then be done without continuous screening. This greatly reduces doses to both patients and staff.

    • X-ray Beam direction:

      Ensure that the X-ray tube is oriented correctly with respect to the staff, patient and the part under examination. Position the X-ray tube according to the anatomical landmarks and do not search for the fracture or the part to be examined by screening.

      The X-ray beam must not be used until this has been done.

    • X-ray Beam collimation:

      Signaficant reductions in dose to both the staff and patients can be achieved by the use of collimators controlling the size of the X-ray beam. The minimum field size with adequate visualization of anatomical landmarks should be used. This will improve the image quality by reducing the amount of scattered radiation.

    • Geometry:

      The correct positioning of the C-arm is of utmost importance and should be the responsibility of the surgeon. To do this, we should be aware of the following:

      The C-arm consists of the X-ray tube (source of X-rays) and the image intensifier (image receptor). The X-ray beam emanates from the X-ray tube, penetrates the part examined and the emergent beam is picked up by the image intensifier. On it course from the X-ray tube to the image intensifier, the X-ray beam is attenuated by the removal of X-rays from the beam by the tissues through either absorption or scattering. This means that the level of radiation is highest near the source (X-ray tube) and lowest near the image intensifier (receptor).

      Backscatter with a resultant increase in radiation is also highest on the side of the X-ray source, especially when thicker parts of the body are examined. Thus the safe side for the surgeon is on the side of the image intensifier and the danger side on the side of the X-ray tube.

      Because the X-ray tube is always smaller than the image receptor and because the image receptor needs to be as close to the patient as possible, it is easier to reach the site of the operation with the X-ray tube on the side of the surgeon. Therefore surgeons tend to position the C-arm in such a position. This practice is a concern because it exposes the surgeon to a high dose of radiation which comes from both the X-ray tube and from backscatter.

      Scattered radiation has implications for image quality and safety of operating personnel. Thick parts of the body such as thigh, hip and trunk will produce higher levels of scattered radiation than thin parts such as the hand or the arm.

      When doing a hip fracture the image receptor should be on the lateral side of the patient and as close to the trochanter area as possible, with the X-ray tube on the medial side of the leg and as far away from the hip as possible. This is for the lateral view of the hip. For the AP view the C-arm should be rotated in such a way that the image receptor is above the hip and as close as possible, with the X-ray tube beneath the table and as far away from the patient as possible.

      In spinal surgery the image receptor should be above the patient and as near as possible, with the X-ray tube beneath the table and as far away from the patient as possible for obtaining PA views. For lateral views the C-arm should be rotated in such a way that the image receptor is on the side of the surgeon and close to the patient with the X-ray tube on the opposite side and as far away as possible. The same principles apply for surgery to the limbs such as the lower leg, the elbow and the forearm.

      Because this positioning of the C-arm makes surgery and access to the site of the surgery very difficult and cumbersome, and at times impossible, we tend to take the easy route and position the C-arm to other way round. This practice brings the thyroid and the eyes of the surgeon directly into the field of highest radiation and his/her hands directly into the unattenuated X-ray beam apart from exposing his/her body to a high dose of radiation from backscatter.

      In many instances this “wrong way” of positioning the C-arm is the only practical option. In these circumstances the surgeon needs to be acutely aware of the hazards thereof and must then employ all the other necessary precautions available to minimize the radiation dose. It needs to be repeated that radiation dose is cumulative, and as the above scenarios are encountered very often in the operating room, this practice will result in an unacceptable high radiation dose over the span of a surgical career.

  4. DOSE MONITORING AND PROTECTION FOR SURGEONS

    • RADIATION PROTECTION STANDARDS

      The aim of radiation protection standards is to prevent detrimental deterministic effects and to limit the probability of stochastic effects to levels considered to be acceptable while carrying out necessary activities from which radiation exposure might result. These standards are laid down by the International Commission on Radiological Protection (ICRP).

      The main principles of the IRCP philosophy are:

      * Justification: - no practice shall be adopted unless its introduction produces a positive net benefit.

      * Optimisation: - All exposures shall be kept As Low As Reasonably Achievable, economic and social factors being taken into account (the ALARA Principle)

      * Limitation: - The dose equivalent to individuals shall not exceed recommended limits. Different limits apply to occupational workers (theatre staff) and members of the public (patients).

    • RADIATION DOSE LIMITS

      • In the case of a pregnant woman, a supplementary dose limit to the surface of the abdomen of 2 millisivert for the remainder of the pregnancy, should apply.

      • Any exposure from diagnosis and treatment should not be taken into account.

      • Any exposure attributable to normal background levels of radiation should not be taken into account.

      • Occupational exposure limits are higher than those for members of the public. The reason for this is that the number of occupationally exposed people is small compared to the total population, and therefore is not considered to contribute significantly to the total population radiation dose. The limit is also calculated so that persons receiving the maximum allowed dose will have an occupational risk which is not more than any other occupation.

      The lower limits for the public arise since this group includes children who, whilst undergoing development, are more susceptible to radiation risks. They also have a longer period in which to express a possible induced effect. The limit is based on keeping exposures to the public below natural background radiation levels.

    • RADIATION DOSE RECEIVED IN ORTHOPAEDIC SURGERY

      A study to determine the degree of ionising radiation the orthopaedic surgeon was exposed to while performing fluoroscopy procedures during a two month period, was done by B van der Merwe and FP du Plessis in Bloemfontein.

      Thermo Luminescent Detectors (TLD’s) were placed on the surgeons thyroid, umbilical region under the lead apron and umbilical region on the outside of the lead apron to determine the ionising radiation dose. 48 Patients were included. The orthopaedic procedures included: 17 Hand/wrist; 11 Foot and ankle; 14 Shoulder/Tib/Fib and 6 Femur/Hip procedures.

      Exposure factors and screening time were recorded.

      Result from Dr J van der Merwe

      Patients

      kV

      MA

      Screening (min)

      48

      59

      1.3

      1.7

      kV = kilo Volt mA = Milliampere

      The counts collected by means of the TLD’s were used to calculate the

      values presenting the radiation doses in mSv.

      TLD region

      mSv

      Pelvis

      5.98

      Pelvis under apron

      0.34

      Thyroid

      1.87

      The value of 5-98 mSv at pelvis level indicates that the current expectation of 3mSv per month is realistic. The implication is that the dose limit of 20mSv per year to the body will be exceeded within six months. The radiation exposure limit to the thyroid has the potential of being exceeded within a year.

      The distribution of radiation was highest at the umbilical area outside the lead apron. The allowable 20mSv limit to the body would be exceeded within six months, hand the surgeon not made use of a lead apron.

      The level of exposure to radiation under the lead apron was seventeen times less.

    • RADIATION MONITORING

      As none of our five senses is able to detect the presence of ionising radiation, we are totally dependent on instruments to detect the dose received.

      • Active monitors

      Radiation levels can be monitored using an ion chamber. The ionisations produced in an air filled chamber are collected and used to measure exposure levels. Such a monitor gives an immediate indication as to the presence of radiation.

      • Passive monitors

      A passive monitor is used to record the accumulated or total radiation received. A typical example is the film badge when using personal dose monitoring badges:

      • Wear badges from an accredited supplier.

      • Wear the badge at chest or waist level underneath the lead apron.

      • Wear only badges assigned to you. Do no share badges.

      • Do not store badges in a place where they can be irradiated or otherwise affected.

      A badge does not provide protection against radiation. It measures the dose received and thereby:

      • Establishes that the dose received is within the limits.

      • Verifies that facilities for radiation protection are adequate.

      • Shows that radiation protection techniques are adequate.

    • RADIATION PROTECTION

      The three basic methods for radiation protection are:

        • Time : - Limiting the duration of each exposure

        • Distance : - Increasing the distance from the X-ray source.

        • Shielding : - Using several materials to shield the radiation source and/or the staff and the patient.

      Protection of Staff:

      For optimum radiation protection, radiation from the primary beam scattered and tube leakage X-rays needs to be considered. The basic factors used to reduce personnel exposures are:

      • Maintain maximum distance away from the primary beam and the patient volume being irradiated. Never place any personal body parts in the primary beam.

      • Use protective shielding

      • Keep the screening time to the minimum necessary.

      • If ABC is activated, use the maximum kVp consistent with images of acceptable contrast.

      • Collimate the beam to the minimum entrance field size necessary.

      • Minimize the use of magnification mode in image intensifiers with selectable field sizes.

      • The X-ray tube should be below the table-top.

      • The image receptor should be placed as close to the patient as possible.

      Protection of the patient:

      Actions taken to minimize the dose of the patient will in many cases help to minimize the dose to the staff as well.

      Only necessary procedures should be undertaken.

      The basic consideration used to reduce patient exposure is:

      • Use ABC systems with high kVp, low mA techniques.

      • Keep screening time to the minimum necessary.

      • Electronic image recording including Last Image Hold (LIH) should be used wherever practicable.

      • Minimize the use of magnification mode.

      • Collimate to the minimum entrance field size consistent with adequate visualization of anatomical landmarks.

      • Position the patient as close as possible to the image receptor.

      • When the patient’s thyroid, gonads and eyes are not required to be irradiated, protective shielding should be used if these organs are in the primary beam or near it.

      • Bear in mind that ABC will automatically boost the radiation exposure rate when X-raying large patients or thick body parts.

      Shielding:

      Staff and patient shielding is affected using:

      • Fixed or moveable lead and lead acrylic shields

      • X-ray protection garments

      Fixed or moveable shields:

      Although not to be found in many operating rooms, lead shields and drapes and transparent lead acrylic shields are available on the market.

      The movable ones come in different sizes and are mounted on castors. The fixed ones are suspended from the ceiling on an arm similar to the ones used to the lights.

      Both can be positioned between the X-ray source and the surgeon during screening and moved out of the way when not in use. As such they can greatly reduce the radiation dose to the surgeon and other staff.

      These shields are rather expensive and cost may preclude their availability. They should, however, be made available to and used by surgeons doing high volumes of spinal and trauma surgery.

      X-Ray protection garments:

      There is considerable variation in the garments and equipment available to protect against ionising radiation. Personnel have some choice in the equipment used but the choice must always result in the maximum possible protection on all occasions when ionising radiation is being used.

      Protective aprons/gowns:

      The only acceptable gowns for the operating team are either one piece or two piece wrap around gowns with a lead equivalent of 0.5mm. Open back gowns do not provide adequate protection and are never acceptable. A two piece gown, skirt and bodice are more comfortable to wear as the weight is shared between shoulders and hips. If this type of gown is used, the bodice must overlap the skirt – a bare midriff is never acceptable near an image intensifier.

      Personnel in the theatre who can guarantee to be constantly more than 2 meters from the X-ray beam may safely wear a wrap around gown of 0.3mm lead equivalence.

      The protective lining of lead gowns is thin and fragile and liable to crack with bending and crumpling. Gowns must be hung on hangers when not in use and must not be thrown down or carelessly discarded after use. Gowns contaminated with body fluids must be sponged clean with water and antiseptic solution.

      Gowns must be inspected visually each time before wearing for defects or cracks and any doubtful gown must be sent for detailed inspection. Gowns must be tested regularly in the X-ray department and subjected to testing in an X-ray beam. This should be done annually and more frequently if the gown is in constant use. Ideally the date of the last test should be recorded on the gown.

      Thyroid shields:

      It is difficult to protect the neck with a gown and therefore the neck must be protected with a thyroid shield which is essentially a wrap around collar that overlaps the gown and is held in place with Velcro or tapes. An acceptable lead equivalence is 0.5mm. All personnel in theater should wear thyroid shields regardless of whether they can maintain a distance greater than 2 meters from the X-ray source.

      Eye protection:

      Several variations are available.

      • Lead acrylic glasses or wrap around glasses that double as a surgical splash shield.

      • Prescription lead acrylic glasses

      • Lead acrylic “clip ons” for prescription glasses.

      • Wrap around acrylic glasses over prescription glasses.

      • Head shields with lead acrylic visors.

      The sensitivity of the lens to radiation is felt to be due to the failure of normal cell replacement. The cell damage from low dose radiation consists of cell death and abnormal cell reproduction which produce mutated cells.

      The normal metabolism of the eye cannot remove these mutated radiation damaged cells. This results in premature clouding of the crystalline lens causing reduced vision which can be corrected only when the cataract matures over time and is removed.

      Gloves:

      Lead-impregnated gloves are available in size 6 – 9 and should be used in high-risk procedures such as:

      • Intramedullary nailing and cross screwing.

      • Kirschner wire insertion under image intensification control.

      • Fixation of upper femoral fractures.

  5. HELPFUL HINTS TO MINIMIZE EXPOSURE TO IONISING RADIATION:

    • Inform all theatre staff that ionising radiation is to be used.

    • Always wear a lead gown, use a thyroid shield and lead acrylic spectacles.

    • Wear a radiation monitor.

    • Close the operating room when radiation is in use.

    • Use lead impregnated gloves if available.

    • Maintain the maximum distance from the X-ray beam

    • Do not use the image intensifier as an operating table.

    • Use spot and not continuous exposure.

    • Give a clear warning when the image intensifier is to be used.

    • Consider using only one cross screw for locking stable fractures.

    • Do not hesitate to do a limited open reduction when passage of a guide wire is impossible after two attempts.

    • Do not use continuous screening to demonstrate to all the successful fixation of a fracture.

    • PRACTICAL SCENARIOS

    The diagrams on the following pages depict some practical scenarios often encountered in Orthopaedic Surgery. They can only demonstrate radiation patterns and levels in one plane but the global pattern for each scenario is easy to deduce as is the effect of the introduction of a protective screen.

    They should be studied and can be used as a valuable teaching aid for junior staff.

    Adapted and compiled, with permission, from RADATION SAFETY FOR ORTHOPAEDIC SURGEONS published by the Australian Orthopaedic Association.

    DR DF DU P LOUW