Broadcast Antennas Radiation exposure

Radio and television broadcast stations transmit their signals via RF electromagnetic waves. Broadcast stations transmit at various RF frequencies, depending on the channel, ranging from about 550 kHz for AM radio up to about 800 MHz for some UHF television stations. Frequencies for FM radio and VHF television lie in between these two extremes. Operating powers can be as little as a few hundred watts for some radio stations or up to millions of watts for certain television stations. Some of these signals can be a significant source of RF energy in the local environment, and the FCC requires that broadcast stations submit evidence of compliance with FCC RF guidelines. 
The amount of RF energy to which the public or workers might be exposed as a result of broadcast antennas depends on several factors, including the type of station, design characteristics of the antenna being used, power transmitted to the antenna, height of the antenna and distance from the antenna. Since energy at some frequencies is absorbed by the human body more readily than energy at other frequencies, the frequency of the transmitted signal as well as its intensity is important.

Public access to broadcasting antennas is normally restricted so individuals cannot be exposed to high-level fields that might exist near antennas. Measurements made by the FCC, EPA, and others have shown that ambient RF radiation levels in inhabited areas near broadcasting facilities are typically well below the exposure levels recommended by current standards and guidelines. Antenna maintenance workers are occasionally required to climb antenna structures for such purposes as painting, repairs, or beacon replacement. Both the EPA and OSHA have reported that in these cases it is possible for a worker to be exposed to high levels of RF energy if work is performed on an active tower or in areas immediately surrounding a radiating antenna. Therefore, precautions must be taken to ensure that maintenance personnel are not exposed to unsafe RF fields.

Portable Radio Systems Radiation exposure

"Land-mobile" communications include a variety of communications systems that require the use of portable and mobile RF transmitting sources. These systems operate in narrow frequency bands between about 30 and 1,000 MHz. Radio systems used by the police and fire departments, radio paging services, and business radio are a few examples of these communications systems. There are essentially three types of RF transmitters associated with land-mobile systems: base-station transmitters, vehicle-mounted transmitters, and handheld transmitters. The antennas used for these various transmitters are adapted for their specific purpose. For example, a base-station antenna must radiate its signal to a relatively large area, and, therefore, its transmitter generally has to use higher power levels than a vehicle-mounted or handheld radio transmitter. Although these base-station antennas usually operate with higher power levels than other types of land-mobile antennas, they are normally inaccessible to the public since they must be mounted at significant heights above ground to provide for adequate signal coverage. Also, many of these antennas transmit only intermittently. For these reasons, such base-station antennas have generally not been of concern with regard to possible hazardous exposure of the public to RF radiation. Studies at rooftop locations have indicated that high-powered paging antennas may increase the potential for exposure to workers or others with access to such sites, for example, maintenance personnel. Transmitting power levels for vehicle-mounted land-mobile antennas are generally less than those used by base-station antennas but higher than those used for handheld units.

Handheld portable radios such as walkie-talkies are low-powered devices used to transmit and receive messages over relatively short distances. Because of the low power levels used, the intermittence of these transmissions, and the fact that these radios are held away from the head, they should not expose users to RF energy in excess of safe limits. Therefore, the FCC does not require routine documentation of compliance with safety limits for push-to-talk two-way radios.

Radar Systems Radiation exposure

Radar systems detect the presence, direction, or range of aircraft, ships, or other moving objects. This is achieved by sending pulses of high-frequency electromagnetic fields (EMF). Radar systems usually operate at radiofrequencies between 300 megahertz (MHz) and 15 gigahertz (GHz). Invented some 60 years ago, radar systems have been widely used for navigation, aviation, national defense, and weather forecasting. People who live or routinely work around radar have expressed concerns about long-term adverse effects of these systems on health, including cancer, reproductive malfunction, cataracts, and adverse effects for children. It is important to distinguish between perceived and real dangers that radar poses and to understand the rationale behind existing international standards and protective measures used today.

The power that radar systems emit varies from a few milliwatts (police traffic-control radar) to many kilowatts (large space tracking radars). However, a number of factors significantly reduce human exposure to RF generated by radar systems, often by a factor of at least 100:

• Radar systems send electromagnetic waves in pulses and not continuously. This makes the average power emitted much lower than the peak pulse power.
• Radars are directional and the RF energy they generate is contained in beams that are very narrow and resemble the beam of a spotlight. RF levels away from the main beam fall off rapidly. In most cases, these levels are thousands of times lower than in the main beam.
• Many radars have antennas which are continuously rotating or varying their elevation by a nodding motion, thus constantly changing the direction of the beam.
• Areas where dangerous human exposure may occur are normally inaccessible to unauthorized personnel.

Symptoms Radiation sickness

The severity of signs and symptoms of radiation sickness depends on how much radiation you've absorbed. How much you absorb depends on the strength of the radiated energy and the distance between you and the source of radiation. Signs and symptoms also are affected by the type of exposure — such as total or partial body and whether contamination is internal or external — and how sensitive to radiation the affected tissue is. For instance, the gastrointestinal system and bone marrow are highly sensitive to radiation.

Absorbed dose and duration of exposure
The absorbed dose of radiation is measured in a unit called a gray (Gy). Diagnostic tests that use radiation, such as an X-ray, result in a small dose of radiation — typically well below 0.1 Gy, focused on a few organs or small amount of tissue.

Signs and symptoms of radiation sickness usually appear when the entire body receives an absorbed dose of at least 1 Gy. Doses greater than 6 Gy to the whole body are generally not treatable and usually lead to death within two days to two weeks, depending on the dose and duration of the exposure.

Initial signs and symptoms
The initial signs and symptoms of treatable radiation sickness are usually nausea and vomiting. The amount of time between exposure and when these symptoms develop is an indicator of how much radiation a person has absorbed.

After the first round of signs and symptoms, a person with radiation sickness may have a brief period with no apparent illness, followed by the onset of new, more serious symptoms.

In general, the greater your radiation exposure, the more rapid and more severe your symptoms will be.

Early symptoms of radiation sickness*
	Mild exposure (1-2 Gy)	Moderate exposure (2-6 Gy)	Severe exposure (6-8 Gy)	Very severe exposure (8-10 Gy or higher)
Nausea and vomiting	Within 6 hours	Within 2 hours	Within 1 hour	Within 10 minutes
Diarrhea	--	Within 8 hours	Within 3 hours	Within 1 hour
Headache	--	Within 24 hours	Within 4 hours	Within 2 hours
Fever	--	Within 3 hours	Within 1 hour	Within 1 hour
Later symptoms of radiation sickness*
Dizziness and disorientation	--	--	Within 1 week	Immediate
Weakness, fatigue	Within 4 weeks	Within 1-4 weeks	Within 1 week	Immediate
Hair loss, bloody vomit and stools, infections, poor wound healing, low blood pressure	--	Within 1-4 weeks	Within 1 week	Immediate

* Adapted from Radiation exposure and contamination. The Merck Manuals: The Merck Manual for Healthcare Professionals.

When to see a doctor
An accident or attack that causes radiation sickness would no doubt cause a lot of attention and public concern. If such an event occurs, monitor radio, television or online reports to learn about emergency instructions for your area.

If you know you've been exposed to radiation, seek emergency medical care.

Treatments and drugs of Radiation Sickness

The treatment goals for radiation sickness are to prevent further radioactive contamination; treat life-threatening injuries, such as from burns and trauma; reduce symptoms; and manage pain.

Decontamination
Decontamination is the removal of as much external radioactive particles as possible. Removing clothing and shoes eliminates about 90 percent of external contamination. Gently washing with water and soap removes additional radiation particles from the skin.

Decontamination prevents further distribution of radioactive materials and lowers the risk of internal contamination from inhalation, ingestion or open wounds.

Treatment for damaged bone marrow
A protein called granulocyte colony-stimulating factor, which promotes the growth of white blood cells, may counter the effect of radiation sickness on bone marrow. Treatment with this protein-based medication, which includes filgrastim (Neupogen) and pegfilgrastim (Neulasta), may increase white blood cell production and help prevent subsequent infections.

If you have severe damage to bone marrow, you may also receive transfusions of red blood cells or blood platelets.

Treatment for internal contamination
Some treatments may reduce damage to internal organs caused by radioactive particles. Medical personnel would use these treatments only if you've been exposed to a specific type of radiation. These treatments include the following:

• Potassium iodide. This is a nonradioactive form of iodine. Because iodine is essential for proper thyroid function, the thyroid becomes a "destination" for iodine in the body. If you have internal contamination with radioactive iodine (radioiodine), your thyroid will absorb radioiodine just as it would other forms of iodine. Treatment with potassium iodide may fill "vacancies" in the thyroid and prevent absorption of radioiodine. The radioiodine is eventually cleared from the body in urine. Potassium iodide isn't a cure-all and is most effective if taken within a day of exposure.
• Prussian blue. This type of dye binds to particles of radioactive elements known as cesium and thallium. The radioactive particles are then excreted in feces. This treatment speeds up the elimination of the radioactive particles and reduces the amount of radiation cells may absorb.
• Diethylenetriamine pentaacetic acid (DTPA). This substance binds to metals. DTPA binds to particles of the radioactive elements plutonium, americium and curium. The radioactive particles pass out of the body in urine, thereby reducing the amount of radiation absorbed.

Supportive treatment
If you have radiation sickness, you may receive additional medications or interventions to treat:

• Bacterial infections
• Headache
• Fever
• Diarrhea
• Nausea and vomiting
• Dehydration
• Burns

End-of-life care
A person who has absorbed large doses of radiation (6 Gy or greater) has little chance of recovery. Depending on the severity of illness, death can occur within two days or two weeks. People with a lethal radiation dose will receive medications to control pain, nausea, vomiting and diarrhea. They may also benefit from psychological or pastoral care.

Tests and diagnosis of Radiation Sickness

When a person has experienced known or probable exposure to a high dose of radiation from an accident or attack, medical personnel take a number of steps to determine the absorbed radiation dose. This information is essential for determining how severe the illness is likely to be, which treatments to use and whether a person is likely to survive.

Information important for determining an absorbed dose includes:

• Known exposure. Details about distance from the source of radiation and duration of exposure can help provide a rough estimate of the severity of radiation sickness.
• Vomiting and other symptoms. The time between radiation exposure and the onset of vomiting is a fairly accurate screening tool to estimate absorbed radiation dose. The shorter the time before the onset of this sign, the higher the dose. The severity and timing of other signs and symptoms may also help medical personnel determine the absorbed dose.
• Blood tests. Frequent blood tests over several days enable medical personnel to look for drops in disease-fighting white blood cells and abnormal changes in the DNA of blood cells. These factors indicate the degree of bone marrow damage, which is determined by the level of an absorbed dose.
• Dosimeter. A device called a dosimeter can measure the absorbed dose of radiation but only if it was exposed to the same radiation event as the affected person.
• Survey meter. A device such as a Geiger counter can be used to survey people to determine the body location of radioactive particles.
• Type of radiation. A part of the larger emergency response to a radioactive accident or attack would include identifying the type of radiation exposure. This information would guide some decisions for treating people with radiation sickness.

Application of the Basic Standards in Radiation Safety

The BSS set out detailed requirements for practices and interventions to protect workers, patients and the general public from radiation exposure. They also recommend procedures for ensuring the safety of sources, for accident prevention, for emergency planning and preparedness and for mitigating the consequences of accidents. Although the majority are of a qualitative nature, the BSS also establish many requirements expressed in terms of restrictions or guidance on the dose that may be incurred by people. The range of doses spreads over four orders of magnitude, from ones that are so minute that they should be exempt from the requirements to doses that are large enough to make intervention almost mandatory.

Organizational requirements

National governments usually have the responsibilities for enforcing radiation safety standards, generally through a system that includes a regulatory authority. In addition, governments usually provide for certain essential services for radiation protection and safety and for interventions that exceed or that complement the capabilities of regulators. The BSS can only be effectively applied when such a national infrastructure is firmly in place. In addition to legislation and regulations, the essential elements are:

A Regulatory Authority. This should be empowered to authorize and inspect, and to enforce the legislation and regulations. It must have sufficient resources, including adequate numbers of trained personnel. There must be arrangements for detecting any build up of radioactive substances in the general environment, for disposing of radioactive waste and preparing for interventions, particularly during emergencies, that could result in exposure of the public.

Education, training and public information. There must be adequate arrangements and resources for these, as well as for the exchange of information among specialists. There must also be appropriate means of informing the public, its representatives and the information media about health and safety concerns.

Facilities and services for radiation protection and safety must be well established at the national level. These include laboratories for personal dosimetry and environmental monitoring, and calibration and intercomparison of radiation measuring equipment; they could also include central registries for radiation dose records and information on equipment reliability.

Management requirements

To ensure radiation safety, the BSS promotes development of:

• A Safety Culture - that encourages a questioning and learning attitude to protection and safety, and discourages complacency.
• Quality Assurance Programmes - that provide, as appropriate, adequate assurances that the specified requirements related to protection and safety are satisfied.
• Control of Human Factors - limiting, as far as practicable, the contribution of human error to accidents and other events that could give rise to exposures. This can be achieved by ensuring that all personnel on whom protection and safety depend are appropriately trained and qualified.
• Qualified experts - made available for providing advice on the observance of the BSS.

Technical requirements

The BSS promotes sound technical planning and implementation through the following:

Security of sources. Radiation sources must be kept secure so as to prevent theft or damage.

Defence in depth. A multilayer system of protection and safety provisions commensurate with the radiation hazards involved is applied to sources, so that a failure at one layer is compensated for or corrected by subsequent layers.

Good engineering practice. This reflects approved codes and standards, and must be supported by reliable management and organization to ensure protection and safety throughout the life of the sources.

Verification of safety. Protection and safety measures for sources must be made in a way that they can be regularly monitored and verified for compliance. In addition, records should be kept of the results of monitoring and verification.

Transport

Additionally, radioactive substances have to be transported in accordance with the IAEA Regulations for the Safe Transport of Radioactive Material and with any applicable international convention.

Under the BSS, interventions apply to the following: Emergencies, where protective action is needed to reduce or avert temporary radiation exposures, including accidents at nuclear installations (for which emergency plans or procedures have been activated). Chronic exposure situations requiring remedial action to reduce or avert long-term radiation exposure. This includes exposure to radon in buildings and exposure to radioactive residues from past events.

        

Exposure resulting from	Basis	Equivalent period of global exposure to average natural background
Nuclear weapons testing	All past tests	2- 3 years
Apparatus and substances used in medicine	One year of pracitce at the current rate	90 days
Severe accidents	Accidents to date	20 days
Nuclear power generation (under normal operating conditions)	Total nuclear generation to date. One year of practice at the current rate	1 day
Occupational activities	One year of occupational activities at the current rate	8 hours

The table presents the UNSCEAR summary of the relative radiological impact from some practices as well as from severe accidents that required intervention. The levels of radiation exposure are expressed as equivalent periods of exposures to natural resources.

Sources of Artificial Radiation

Doses from artificial radiation are, for most of the population, much smaller than those from natural radiation but they still vary considerably. They are in principle fully controllable, unlike natural sources.

Medical. Radiation is used in medicine in two distinct ways: to diagnose disease or injury; and to kill cancerous cells. In the oldest and most common diagnostic use, X rays are passed through the patient to produce an image. The technique is so valuable that millions of X ray examinations are conducted every year. One chest X ray will give 0.1 mSv of radiation dose. For some diseases, diagnostic information can be obtained using gamma rays emitted by radioactive materials introduced into the patient by injection, or by swallowing or by inhalation. This technique is called nuclear medicine. The radioactive material is part of a pharmaceutical chosen so that it preferentially locates in the organ or part of the body being studied. To follow the distribution or flow of the radioactive material a gamma camera is used. It detects the gamma radiation and produces an image, and this indicates whether the tissue is healthy or provides information on the nature and extent of the disease.

Cancerous conditions may be treated through radiotherapy, in which beams of high energy X rays or gamma rays from cobalt-60 or similar sources are used. They are carefully aimed to kill the diseased tissue, often from several different directions to reduce the dose to surrounding healthy tissue. Radioactive substances, either as small amounts of solid material temporarily inserted into tissues or as radioactive solutions, can also be used in treating diseases, delivering high but localised radiation doses.

Medical uses of radiation are by far the largest source of man-made exposure of the public; the global yearly average dose is 0.3 millisieverts.

Environmental Radiation. Radioactive materials are also present in the atmosphere as a result of atomic bomb testing and other activities. They may lead to human exposure by several pathways external irradiation from radioactive materials deposited on the ground; inhalation of airborne radioactivity, and ingestion of radioactive materials in food and water.

Radioactive fall-out from nuclear weapons tests carried out in the atmosphere is the most widespread environmental contaminant but doses to the public have declined from the relatively high values of the early 1960s to very low levels now. The global yearly average dose is 0.006 millisieverts. However, where tests were carried out at ground level or even underground, localised contamination often remains near weapons sites.

Nuclear and other industries, and to a small degree hospitals and universities, discharge radioactive materials to the environment. Nearly all countries regulate industrial discharges and require the more significant to be authorized and monitored. Monitoring of such effluent may be carried out by the government department that authorizes the discharges as well as by the operator.

The nuclear power industry releases small quantities of a wide variety of radioactive materials at each stage in the nuclear fuel cycle. For the public the global yearly average dose is 0.008 millisieverts. The type of radioactive materials, and whether they are liquid, gaseous or particulate depends upon the operation of each process. For instance, nuclear power stations release carbon-14 and sulphur-35, which find their way through food chains to humans. Liquid discharges include radioactive materials that people may ingest through fish and shellfish.

The yearly dose to individuals living close to a power plant is small - usually a fraction of a millisievert; doses to people further away are even smaller. Reprocessing nuclear fuel produces higher doses which vary greatly from plant to plant. For the most exposed members of the public, they can be as high as 0.4 millisieverts, but for most of the population they are very much smaller.

World-wide, there are estimated to be four million workers exposed to artificial radiation as a result of their work, with an average yearly dose of about 1 millisievert. Another five million (mostly in civil aviation) have yearly average doses due to natural radiation of 1.7 millisieverts.

Non-nuclear industries also produce radioactive discharges. They include the processing of ores containing radioactive materials as well as the element for which the ore is processed. Phosphorus ores, for instance, contain radium which can find its way into the effluent. A very different industry, the generation of electricity by coal-fired power stations, results in the release of naturally-occurring radioactive materials from the coal. These are discharged to air and transfer through food chains to the population. However, the radiation doses are always low - 0.001 millisieverts or less.

Accidental releases of radioactive materials. Apart from contamination due to the normal operations of the nuclear industry, radioactivity has been widely dispersed accidentally. The most significant accident was at Chernobyl nuclear power station in the Ukraine, where an explosion caused the release of large amounts of radioactivity over a period of several days. Airborne radioactive material dispersed widely over Europe and even further afield. Contamination at ground level varied considerably, being much heavier where rain washed the radioactivity out of the air. Radiation doses therefore varied significantly from normal. More than 100,000 people were evacuated during the first three weeks following the accident. Whole body doses received from external radiation from the Ukrainian part of the 30-km exclusion zone showed an average value of 15 millisieverts. (source OECD, 1995)

Radiation in Consumer Products. Minute radiation doses are received from the artificial radioactivity in consumer goods such as smoke detectors and luminous watches, and from the natural radioactivity of gas mantles. The global yearly average dose is extremely small (0.0005 millisieverts).

YOUR RESPONSIBILITIES REGARDING DOSE RECORDS

Prior to initial TLD assignment, you must provide a written list to Radiological Control of prior employment involving radiation exposure. Once your dose history at TJNAF begins, you have several important responsibilities regarding your dosimetry and dose records.

Notify Radiological Control personnel prior to and following any radiation dose received at another facility so that dosimetry records can be updated. If you are a radiation worker at another facility, you must inform the RCG when you apply for a TLD. 

Do not take your TJNAF dosimetry to any other facility where you may receive radiation exposure. 

Notify Radiological Control of any medical administration of radiation or radioactive material. (This does not include routine medical and dental x rays.) Do not wear your dosimetry or enter any Radiologically Controlled Areas following such treatment until approved by the RCG. 

Notify the RCG when your work assignment at TJNAF has ended. 

Know the proper dosimetry storage location. Never take your dosimetry home or offsite. Dosimetry must be returned for processing periodically. Personnel who fail to return dosimetry will be restricted from continued radiological work.

Self Reading Pocket Dosimeters - SRPDs

The term Self Reading Pocket Dosimeter applies to any of a variety of devices which can be read by the wearer to determine the dose received. The SRPD is usually used as a supplemental device to aid in dose tracking during activities where elevated doses are possible.

• Pocket Ion Chambers - (PIC) These are small instruments which operate on the electroscope principle. Typically, the range of the PIC is 0-200 mR. This is one of the most common supplemental dosimeters used in Radiation Areas. 
  
• Electronic dosimeters (ED) are sometimes used instead of and in addition to PICs when it is helpful to have he additional capability of dose or dose rate alarm functions. The electronic dosimeter has a broad dose range and is usually very accurate. 
  
• Self-reading neutron dosimetry such as neutron bubble dosimeters may be required for certain work areas. Always consult the applicable Radiation Work Permit (RWP) and Operational Safety Procedure. 
  
• Other supplemental dosimeters may be required when entering High Radiation Areas or other RWP areas.

What happens if a human is exposed to a lot of radiation all at once?

Depending upon the level of exposure, that person will suffer from what is known as Acute Radiation Syndrome. The following is a description of effects versus dose:

• Less than 25,000 millirem, there are no directly observable effects. There are changes in some human cells that can be observed with a microscope at exposures above 10,000 mrem.
• 25,000 to 50,000 millirem, there will be no symptoms, but there might be some changes in the chemistry of the individual's blood.
• 100,000 to 300,000 millirem, some physical changes (such as skin reddening and temporary hair loss) are seen, particularly at the high end of the range.
• 300,000 to 1,000,000 millirem, vomiting is the first symptom, and the human loses his/her ability to produce blood. At the upper end of this range, bone marrow transplants are generally needed and, if medical care is not available, the condition can be fatal within one month of exposure.
• 1,000,000 to 5,000,000 millirem, there will be vomiting, loss of blood production, and failure of the gastrointestinal system. In general, an acute dose of this magnitude is fatal within two weeks.
• Greater than 5,000,000 millirem, central nervous system failure is likely, and death will occur within a period of days.

For comparison purposes, the maximum an individual is allowed to receive from occupational exposure to ionizing radiation is 5,000 millirem in a year.

Use of Radiation Shields to reduce Radiation exposure

Use of radiation shielding is highly effective in intercepting and reducing exposure from scattered radiation (Figure 5-6). The operator can realize radiation exposure reductions of more than 90 percent through the correct use of any of the following shielding options. Shields are most effective when placed as near to the radiation scatter source as possible (i.e., close to patient).

Many fluoroscopy systems contain side-table drapes or similar types of lead shielding. Use of these items can significantly reduce operator exposures. Many operators have had little difficulty incorporating their use, even during procedures requiring multiple re-positioning of the system.

Figure 5-6: Benefit of Hanging Shield

Courtesy of Sorenson, 2000.

Ceiling-mounted lead acrylic face shields should be used whenever these units are available, especially during cardiac procedures. Correct positioning is obtained when the operator can view the patient, especially the beam entrance location, through the shield.

Portable radiation shields can also be employed to reduce exposure. Situations where these can be used include shielding nearby personnel who remain stationary during the procedure.

Use of Personal Protective Equipment to reduce the Radiation exposure

Use of leaded garments substantially reduces radiation exposure by protecting specific body regions. Many fluoroscopy users would exceed regulatory limits should lead aprons not be worn. Operator and nearby staff (within 2 meters) are required to wear lead aprons whenever fluoroscopes are operated at Henry Ford Hospital.  Due to the poor material qualities of Leaded garments, proper storage is essential to protect against damage (Figure 5-6).  Whenever leaded apron are required, they must be supplied and paid for by your employer (Henry Ford Health System)

Figure 5-6: Properly Stored Leaded Garments

Courtesy of Sorenson, 2000.

Courtesy of Sorenson, 2000.

Lead aprons do not stop all the x-rays.  Typically at least a 80% reduction in radiation exposure is obtained by wearing a lead apron (Figure 5-7). It should be noted that the apron's effectiveness is reduced when more penetrating radiation is employed (e.g., the ABC boost's kVp for thick patients). Two piece lead apron systems are recommended for most users since they provide "wrap-around protection" and distribute weight more evenly on the user. Some aprons contain an internal frame that distributes some of the weight from the shoulders onto the hips much like a backpack frame. So called "light" aprons should be scrutinized to ensure that adequate levels of shielding are provided.  State of Michigan law requires the use of 0.5 mm lead equivalent aprons.

Figure 5-7:  Lead Apron Protection Efficiency

Courtesy of Sorenson, 2000.


Note that higher tube voltages sharply reduces the shielding benefits of lead aprons. Higher tube voltages will occur when imaging large patients or thick body portions. Also note that light aprons (0.25 to 0.35 mm Pb) provide less protection compared to the recommended 0.5 mm thickness.

Thyroid shields provide similar levels of protection to the individual’s neck region. Thyroid shield use is required for operators who use fluoroscopy extensively during their practice.

Optically clear lead glasses are available that can reduce the operator's eye exposure by 85-90% (Siefert 1996). However, due to the relatively high threshold for cataract development, leaded glasses are only recommended for personnel with very high fluoroscopy work loads (e.g., busy Radiology and Cardiology Interventionists). Glasses selected should be "wrap-around" in design to protect the eye lens from side angle exposures. Leaded glasses also provide the additional benefit of providing splash protection. Progressive style lenses for bifocal prescriptions are available from a limited number of manufacturers.

The latex leaded gloves provide extremely limited protection. Standard (0.5 mm lead equivalent) leaded gloves provide useful protection to the user’s hands.   However, trade-offs associated with use of 0.5 mm leaded gloves include loss in tactile feel, increased encumbrance and sterility. For these reasons, use of leaded gloves is left to the operator’s discretion. To minimize radiation exposure to the hands, the operator should:

1. Avoid placing his hands in the primary beam at all times;  
2. Place hands only on top of the patient. Hands should never be placed underneath the patient or table top during imaging; 
3. Consider using leaded gloves if hand placement within the X-ray beam is necessary or positioned nearby for extended periods of time.

Tips to reduce the Radiation exposure in Fluroscopy

• Keep beam ON-time to an absolute minimum!
• Always use tight collimation!
• Do not overuse the magnification mode.
• Keep the image intensifier as close to the patient as possible, and the tube as far away from the patient as possible.  
• Keep the kVp as high as possible considering the patient dose versus image quality. 
• Keep tube current (mA) as low as possible. 
• Minimize room lighting to optimize image viewing. 
• Do not overuse the high dose rate. 
• Personnel must wear protective aprons, use shielding, monitor doses and know how to position themselves and the machines for minimum dose. 
• Change projections angle for long procedures to minimize local skin doses.
• Remember that the X-ray output, patient dose, and area scatter levels increase for larger patients.

"Tips to reduce the Radiation exposure in Fluroscopy"

ALARA Philosophy

Regulatory dose limits should be viewed as the maximum tolerable levels. Since stochastic radiation effects, such as carcinogenesis, can not be ruled-out at low levels of exposure, it is prudent to minimize radiation exposure whenever possible. This concept leads to the As-Low-As-Reasonably-Achievable (ALARA) philosophy.

Simply stated, the ALARA philosophy requires that all reasonable measures to reduce radiation exposure be taken. Typically, the operator defines what is reasonable. The principles discussed in this manual are intended to assist the operator in evaluating what constitutes ALARA for his/her fluoroscopy usage.

The Henry Ford Hospital administration is committed to ensuring that radiation exposure to its medical staff and employees is kept ALARA. Full attainment of this goal is not possible without the co-operation of all medical users of radiation devices.

Optimizing X-ray Tube Voltage to reduce the Radiation exposure

Selection of an adequate kVp value will allow sufficient X-ray penetration while reducing the patient’s dose rate. In general, the highest kVp should be used which is consistent with the degree of contrast required (high kVp decreases image contrast). 

Henry Ford Hospital has many resources available (e.g., Staff Radiologists, Medical Physicists) to assist the operator in optimizing the fluoroscopy image while minimizing patient exposure.

Reduce Air Gaps to reduce Radiation exposure

Keeping the I-I as close to patient’s surface as possible significantly reduces patient and operator exposures (Figure \). The I-I will intercept the primary beam earlier and allow less scatter to operator and staff. In addition, The Automatic Brightness Control (ABC) system would not need to compensate for the increased X-ray tube to I-I distance caused by the air gap. The presence of an air gap will always increase patient/operator radiation exposure and decrease image quality.

Figure: Benefit of Reducing the Air Gap (I-I  Close to Patient)

Courtesy of Sorenson, 2000.

Care should be taken whenever the image view angle is changed during the procedure (e.g, changing from an ANT to a steep LAO). The I-I is often moved away from the patient while changing X-ray tube position. Large air gaps can result if the table or I-I height remains unadjusted.

TYPES OF RADIATION

a.  General.  Four major forms of radiation are commonly found emanating from radioactive matter:  alpha, beta, gamma, and X radiation.  The marked differences in the characteristics of these radiations strongly influence their difficulty in detection and consequently, the detection methods used.  

b.  Alpha.  An alpha particle is the heaviest and most highly charged of the common nuclear radiations.  As a result, alpha particles very quickly give up their energy to any medium through which they pass, rapidly coming to equilibrium with, and disappearing in, the medium.  Since nearly all common alpha radioactive contaminants emit particles of about the same energy, 5 MeV, some general statements may be made about the penetration length of alpha radiation.  Generally speaking, a sheet of paper, a thin layer (a few hundredths of a millimeter) of dust, any coating of water or less than 4 cm of air are sufficient to stop alpha radiation.  As a result, alpha radiation is the most difficult to detect.  Moreover, since even traces of such materials are sufficient to stop some of the alpha particles and thus change detector readings, quantitative measurement of alpha radiation is impossible outside of a laboratory environment where special care may be given to sample preparation and detector efficiency.  

c.  Beta.  Beta particles are energetic electrons emitted from the nuclei of many natural and manmade materials.  Being much lighter than alpha particles, beta particles are much more penetrating.  For example, a 500-keV beta particle has a range in air that is orders of magnitude longer than that of the alpha particle from plutonium, even though the latter has 10 times more energy; however, many beta-active elements emit particles with very low energies.  For example, tritium emits a (maximum energy) 18.6-keV beta particle.  At this low an energy, beta particles are less penetrating than common alpha particles, requiring very special techniques for detection.  

d.  Gamma and X Radiation.  Gamma rays are a form of electromagnetic radiation and, as such, are the most penetrating of the four radiations and easiest to detect.  Once emitted, gamma rays differ from X-rays only in their energies, with X-rays usually lying below a few hundred keV.  As a result, X-rays are less penetrating and harder to detect; however, even a 60- keV gamma ray has a typical range of a 100 meters in air and might penetrate a centimeter of aluminum.  In situations in which several kinds of radiations are present, these penetration properties make X-ray and/or gamma-ray detection the technique of choice.  

e.  Radiations from the Common Contaminants.  Table 1., below, lists some of the commonly considered radioactive contaminants and their primary associated radiations.
 

Table 1.  Commonly Considered Radioactive Contaminants and Their Primary Associated Radioactive Emissions

Neutron REM Meter- with Proportional Counter —

 A boron trifluoride or helium-3 proportional counter tube is a gas-filled device that, when a high voltage is applied, creates an electrical pulse when a neutron radiation interacts with the gas in the tube. The absorption of a neutron in the nucleus of boron-10 or helium-3 causes the prompt emission of a helium-4 nucleus or proton respectively. These charged particles can then cause ionization in the gas, which is collected as an electrical pulse, similar to the G-M tube. These neutron-measuring proportional counters require large amounts of hydrogenous material around them to slow the neutron to thermal energies. Other surrounding filters allow an appropriate number of neutrons to be detected and thus provide a flat-energy response with respect to dose equivalent. The design and characteristics of these devices are such that the amount of secondary charge collected is proportional to the degree of primary ions produced by the radiation. Thus, through the use of electronic discriminator circuits, the different types of radiation can be measured separately. For example, gamma radiation up to rather high levels is easily rejected in neutron counters. 

What is Radioactive Contamination?

If radioactive material is not in a sealed source container, it might be spread onto other objects. Contamination occurs when material that contains radioactive atoms is deposited on materials, skin, clothing, or any place where it is not desired. It is important to remember that radiation does not spread or get "on" or "in" people; rather, it is radioactive contamination that can be spread. A person contaminated with radioactive material will receive radiation exposure until the source of radiation (the radioactive material) is removed.

• A person is externally contaminated if radioactive material is on the skin or clothing.
   
• A person is internally contaminated if radioactive material is breathed in, swallowed, or absorbed through wounds.
   
• The environment is contaminated if radioactive material is spread about or is unconfined.

Source:http://hps.org/publicinformation/ate/faqs/radiation.html

How Much Radioactive Material Is Present?

The size or weight of a quantity of material does not indicate how much radioactivity is present. A large quantity of material can contain a very small amount of radioactivity, or a very small amount of material can have a lot of radioactivity.

For example, uranium-238, with a 4.5-billion-year half-life, has only 0.00015 curies of activity per pound, while cobalt-60, with a 5.3-year half-life, has nearly 513,000 curies of activity per pound. This "specific activity," or curies per unit mass, of a radioisotope depends on the unique radioactive half-life and dictates the time it takes for half the radioactive atoms to decay.

In the United States, the amount of radioactivity present is traditionally determined by estimating the number ofcuries (Ci) present. The more curies present, the greater amount of radioactivity and emitted radiation.

Common fractions of the curie are the millicurie (1 mCi = 1/1,000 Ci) and the microcurie (1 μCi = 1/1,000,000 Ci). In terms of transformations per unit time, 1 μCi = 2,220,000 dpm.

The SI system uses the unit of becquerel (Bq) as its unit of radioactivity. One curie is 37 billion Bq. Since the Bq represents such a small amount, one is likely to see a prefix noting a large multiplier used with the Bq as follows:

• 37 GBq = 37 billion Bq = 1 curie
• 1 MBq = 1 million Bq = ~ 27 microcuries
• 1 GBq = 1 billion Bq = ~ 27 millicuries
• 1TBq = 1 trillion Bq = ~ 27 curies

Radiation Exposure from Various Sources

Source	Exposure
External Background Radiation	60 mrem/yr, US Average
Natural K-40 and Other Radioactivity in Body	40 mrem/yr
Air Travel Round Trip (NY-LA)	5 mrem
Chest X-Ray Effective Dose	10 mrem per film
Radon in the Home	200 mrem/yr (variable)
Man-Made (medical x rays, etc.)	60 mrem/yr (average)