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X-ray Sources
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X-ray Sources

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  • The fingers, of course, are the parts of the body most likely to receive these high exposures. Environmental levels near the machine from scattered radiation can also be quite high, perhaps a few hundred millirems per hour. Maximum occupational exposures for a three-month period would be attained within a few hours at these exposure rates.
  • The protection program for these x-ray units consists of the following elements. These elements are implemented to differing degrees depending upon the system and exposure potential.
  • Designated Responsible Operator - Review responsibilities
    The head of the organizational unit to which the x-ray unit is assigned shall ensure that only those individuals who are qualified to use the x-ray unit and that the unit is maintained in manner that is in compliance with safety requirements specified for such units.
    User Training
    Hazards of exposure to x-rays
    General methods to minimize radiation exposure
    Protective devices incorporated into the x-ray unit
    Proper operating procedure for the x-ray unit
    How to recognize failures of protections systems
    Operating procedures provided should be readily available and include:
    Proper operating sequence
    Description of personnel protective mechanisms and warning devices
    Prohibition of altering or bypassing interlocks on the system
    Engineered Protection Systems
    Failsafe interlocks on all protective barriers of the unit
    Shielding adequate to reduce the exposure rate at 5 cm to 0.24 mR/hr
    A console “power-ON” indicator should be present
    Warning light of size and brightness adequate to warn anyone present
    Labeling of “Caution: This equipment produces x-rays when energized”
    Surveillance Programs
    Log book
    Personnel exposures
  • Accessible areas
    Exposure rates not exceeding 2 mR/hr. For small beams, e.g., less than 1 cm-2, this is approximately equivalent to a limit of 4000 photons/sec. Accessible area is any area outside a barrier or shield routinely occupied by personnel.
    Log book
    Record major changes to the system shielding, enclosures, and configuration.
    A list of authorized operators shall be maintained.
    Results of surveys performed of any modifications or alterations to the systems shielding and enclosures and around any covers that have been removed since the last operation.
    A copy of the operating procedures.
    Routine surveys (at least once per year).
    Results include:
    Date of survey
    Background
    Area surveys
    Results
    Name of individual performing the survey
    Maintain all of the engineered protection systems.
  • The greatest risk of acute accidental exposures occurs in manipulations of a sample to be irradiated by the direct beam in diffraction studies. Exposure rates of the order of 10,000 R/second can exist at the tube housing port. Erythema would be produced after an exposure of only 0.03 seconds, and in 0.1 seconds severe and permanent injury could occur.
    In general, the largest portion of low energy x-rays will be absorbed by the skin or eyes. Depending on the individual sensitivity, doses as low as 500 rem may cause skin reddening and discomfort within a few hours. This effect may be delayed several days. There is always a delay before effects occur at doses less than several thousand rem, but with larger doses the underlying tissue is affected and scar tissue if formed. Doses larger than 4000 rem usually cause some permanent damage and the tissue may not heal at all, necessitating amputation.
    Eyes show similar effects at the does mentioned, with several thousand rem producing enough damage for loss of sight. An exposure of 500 rem can also cause formation of cataracts.
    The most probable delayed effect of x-ray exposure is cancer production in 10-30 years. An increase in tumor probability has been shown for doses above 100 rem.
  • Time
    Minimize the time around the x-ray source. Less time equals less exposure.
    Distance
    Increase the distance. Radiation reduces by 1/(distance)2
    Shielding
    Put appropriate material between you and the source.
  • Devices
    Interlocks must not be bypassed.
    Systems shielding must not be bypassed.
    Warning lights must be operational and used.
    Procedures
    Operating procedures must include sequence of operation.
    Specific procedural precautions to avoid or minimize radiation exposures.
    Limitations on operating parameters and use of the system.
    Radiation survey requirements being performed and recorded.
    If it is not done in writing, it is not done!
    Wear the dosimetry devices provided.
    Complete training at least annually.
  • Failures
    The interlocks are not engaged and the systems still generates x-rays.
    Exposures are observed on dosimetry devices.
    Warning lights are not operational.
    Redness of the skin.
    Unqualified operators using the system.
    Survey instrument records exposures where exposures normally do not occur.
    Key is missing.
    Surveys are not being performed.
    The “power-ON” indicator does not work properly.
  • Survey procedures
    Make operational checks of the survey instrument before and after using it.
    Know the background radiation levels. Check a radiation free area for background levels.
    Survey accessible areas wear the beam or scatter is expected.
    Record the survey results in the log book. If the survey has not been done in writing, then (according to regulators) it has not been done.
    Contact the Responsible User (the researcher with the permit to use the diffraction system) and the Radiation Safety Officer if unusual levels are radiation are observed (higher or lower readings from normal).
    Ensure that the warning lights and “power-ON’ indicator are working properly.
    Wear your dosimeter (film badge). Wear is correctly.
    Ensure non-operators are away from the x-ray systems during operation. If they are not identified on the permit, they are non-operators.
    Limitations
    Survey instruments must be calibrated annually when used for health & safety.
    Survey instruments typically record low results when surveying energies below 25 kVp. Often a correction factor of 3 to 10 is multiplied for more realistic data.
    Batteries die often. Check them before and after using the instrument.
    Dosimetry devices (area monitors) should not be removed from the area.
    Use the safety equipment and devices (interlocks, warning systems, procedures).
  • Dosimetry devices are passive monitor equipment. They provide data as to the exposure after it has occurred.
    Whole body monitors are required. They must be worn between the collar and the waist external of routine clothing.
    Monitors are exchanged monthly. They are NOT free.
    Area monitors are provided for additional information.
    Typical exposure readings have a threshold of 5 to 10 mrem. Below 10 mrem are typically reported as zero. This does not mean that the exposure was zero.
    The greatest risk of acute accidental exposures occurs in manipulations of the sample to be irradiated by the direct beam in diffraction studies. Exposure rates of the order of 10,000 R/sec can exist at the tube housing port. Erythema would be produced after an exposure of only 0.03 seconds and in 0.1 seconds sever and permanent injury could occur. The fingers, of course, are the parts of the body most likely to receive these high exposures.
  • Transcript

    • 1. Copyright of Pickering Enterprises X-Ray Sources Characteristics of X-rays X-ray Safety for Medical Personnel Analytical X-ray Systems Basic x-ray Safety Requirements
    • 2. Copyright of Pickering Enterprises Characteristics of X-rays • Produced when high speed electron is slowed down and/or stopped • External hazard – Time – Distance – Shielding – Engineered controls – Monitoring – Administrative
    • 3. Copyright of Pickering Enterprises What are x-rays? • X-rays are produced when accelerated electrons interact with a target, usually a metal absorber, or with a crystalline structure. This method of x-ray production is known as bremsstrahlung. • The bremsstrahlung produced is proportional to the square of the energy of the accelerated electrons used to produce it, and is also proportional to the atomic number (Z) of the target (absorber).
    • 4. Copyright of Pickering Enterprises
    • 5. Copyright of Pickering Enterprises Ionizing Radiation
    • 6. Copyright of Pickering Enterprises X-RAY AND GAMMA ( ) RAY PROPERTIES Charge: None Mass: None Velocity: 3 x 108 m/s Origin: Rays: Nucleus X Rays: Electron Cloud & Bremsstrahlung
    • 7. Copyright of Pickering Enterprises
    • 8. Copyright of Pickering Enterprises
    • 9. Copyright of Pickering Enterprises
    • 10. Copyright of Pickering Enterprises • Primary Beam •The critical radiation exposure problem with analytical X-ray •Can cause localized acute exposure •Never intentionally place any part of their body in the primary beam •The maximal energy deposition in epithelial tissues •Erythema or reddening of the skin can occur when skin is acutely exposed to 300 R (much less than a second) •Radiation burns may occur from longer exposures. • Scattered Radiation •Some of the radiation is scattered out of the primary beam. •These radiation fields are less intense than the primary beam •They still represent a potential hazard •Scattered radiation fields can be measured by the analytical operators with a survey meter. • Leakage •Some radiation may leak around the rube housing structure. Three Regions of High Exposure Concern
    • 11. Copyright of Pickering Enterprises 1. Primary Beam 2. Scattered Radiation 3. Leakage Rotating Anode Systems: What are the danger areas?
    • 12. Copyright of Pickering Enterprises 1. Primary Beam 2. Scattered Radiation 3. Leakage Sealed Tube Systems: What are the danger areas?
    • 13. Copyright of Pickering Enterprises Sealed Tube/Microfocus Systems: What are the danger areas? 1. Primary Beam 2. Scattered Radiation 3. Leakage
    • 14. Copyright of Pickering Enterprises X-Ray Burns vs. Thermal Burns • Most nerve endings are near the surface of the skin • High energy x-rays penetrate the outer layer of the skin that contains most of the nerve endings so one does not feel an X-Ray burn until the damage has been done • X-rays penetrate to the deeper, basal skin layer, damaging or killing the rapidly dividing germinal cells, that are destined to replace the outer layers
    • 15. Copyright of Pickering Enterprises Exposure Effects • 1000 rad - second degree burns • 2000 rad - intense swelling within a few hours • 3000 rad - completely destroys tissue • 400 rad acute whole body exposure is LD 50/30 • LD 50/30 - lethal to 50% of population within 30 days if not treated
    • 16. Copyright of Pickering Enterprises Hazards of Exposure to X-rays
    • 17. Copyright of Pickering Enterprises Accident Case Study • Case Study - A radiation accident at an industrial accelerator facility Health Physics, Vol. 65, No. 2, August 1992, pp. 131-140. Reproduced by permission. • 3MV potential drop accelerator. 40 rad/s inside victim’s shoes, 1300 rad/s to hands. • 3 days after exposure •Note erythema and swelling •1 month after • Note blistering and erythema • 2 months after
    • 18. Copyright of Pickering Enterprises Bioeffects- X-rays and Skin • Most radiation overexposures from analytical x-ray equipment are to the extremities. • For x-rays of about 5-30 keV, irradiation of the fingers or hands does not result in significant damage to blood-forming tissue. • At high exposures some general somatic effects to the skin can occur. Very high exposures may necessitate skin grafting or amputation of the affected extremity. • Biological effects can be observed at 10 rem in special blood studies. Typically effects are visually observed at 50 to 100 rem.
    • 19. Copyright of Pickering Enterprises Common Cause of Accidents • Rushing to complete a a job – Overriding safety features • Boredom • Fatigue • Illness • Personal Problems • Working on unfamiliar equipment • Complacency (Attitude Accumulation) • 2 people working 1 job • Frustration
    • 20. Copyright of Pickering Enterprises Four Main Causes of Accidents • Poor equipment configuration – Ex. Unused beam ports not covered • Manipulation of equipment when energized – Adjustment of samples or alignment of cameras when x-ray beam is on • Equipment failure – Shutter failure – Warning light failure • Inadequate training or violation of procedure – Incorrect use of equipment – Overriding interlocks
    • 21. Copyright of Pickering Enterprises Common Cause of Accidents • Rushing to complete a ajob – Overriding safety features • Boredom • Fatigue • Illness • Personal Problems • Working on unfamiliar equipment • Complacency (Attitude Accumulation) • 2 people working 1 job
    • 22. Copyright of Pickering Enterprises Preventing Accidents • Know location and/or presence of primary and diffracted beams AT ALL TIMES • Provide and inspect shielding • Do not perform maintenance (without confirming that the tube is not energized) • Perform check of safety devices at least once per month • Survey unit whenever moved or reconfigured. • DON’T PUT YOUR BODY PARTS IN THE BEAM!!
    • 23. Copyright of Pickering Enterprises Exposure Estimates At 5 cm from Tube Port Cu 50 x (40) x (20) 29 = 279 R/sec (7.5)2 74 Mo 50 x (36) x (20) 42 = 363 R/sec (7.5)2 74 Ag 50 x (40) x (20) 47 = 452 R/sec (7.5)2 74 Cu 50 x (50) x (20) 74 = 889 R/sec (7.5)2 74 Exposure Rate: 50 x (kV) x (mA) Z = R/sec (cm)2 74 Characteristic Intensity: Proportional to: (kVp - kVc)1.6
    • 24. Copyright of Pickering Enterprises Radiation Safety Training for X-Ray Diffraction •Designated Responsible Operator •User Training •Operating Procedures/Instructions •Engineered Protection Systems •Surveillance Programs
    • 25. Copyright of Pickering Enterprises Open Beam XRD • Example of an unenclosed (open) x-ray diffractometer (Geology Department). • The open x-ray beam of such an instrument can be extremely hazardous, and it is far preferable to enclose the entire x-ray apparatus.
    • 26. Copyright of Pickering Enterprises XRD (tin/polycarbonate enclosure) • Properly enclosed and interlocked x-ray diffrac- tometer. The enclosure is made of tin-impregnated polycarbonate. – Leaded glass enclosures are also used. • If a panel is opened while the XRD is being used, the interlock should either shut off the x-ray or close the shutter, preventing accidental exposure to personnel.
    • 27. Copyright of Pickering Enterprises AFC8 & Mercury CCD
    • 28. Copyright of Pickering Enterprises AFC7 & Mercury CCD
    • 29. Copyright of Pickering Enterprises RAXIS RAPID
    • 30. Copyright of Pickering Enterprises DMAX RAPID
    • 31. Copyright of Pickering Enterprises MULTIFLEX
    • 32. Copyright of Pickering Enterprises Siemens for powder
    • 33. Copyright of Pickering Enterprises Electron Microscope
    • 34. Copyright of Pickering Enterprises DMAX
    • 35. Copyright of Pickering Enterprises Direct Drive RAXIS/Jupiter
    • 36. Copyright of Pickering Enterprises Belt Drive Rotating Anode AFC6/IV++
    • 37. Copyright of Pickering Enterprises Multiflex
    • 38. Copyright of Pickering Enterprises Safety Devices Analytical units shall have the following safety devices as required by State Regulations. Unused ports shall be secure in a manner which will prevent accidental opening. Open beam units shall have a shutter over the port which cannot be opened unless a collimator or coupling has been connected. Safety interlocks shall not be used to de-activate the X-ray beam except in an emergency or during testing of the interlock system. Warning Devices All units with an open beam configuration shall have an easily identified device located near the radiation source housing and labeled what gives a clear, visible indication of the X-ray generation status (on-off) Safety interlocks shall not be used to de-activate the X-ray beam except in an emergency or during testing of the interlock system.
    • 39. Copyright of Pickering Enterprises Warning Labels A label which bears the following or similar words shall be placed on the X-ray source housing: CAUTION - HIGH INTENSITY X-RAY BEAM A label which bears the following or similar wording shall be placed on the control console of each unit near any switch which energizes the source: CAUTION - RADIATION THIS EQUIPMENT PRODUCES RADIATION WHEN ENERGIZED
    • 40. Copyright of Pickering Enterprises Warning Lights An easily visible warning light labeled with these or similar words “X- RAY ON” shall be placed near any switch that energizes an X-ray source, and shall be illuminated only when the generator is energized, and have fail-safe characteristics. Shutters Each port shall be equipped with a shutter that cannot be opened unless a collimator or a coupling device has been connected to the port.
    • 41. Copyright of Pickering Enterprises Radiation Surveys The Radiation Safety Office will perform a survey annually and following major repairs and/or system modifications. This survey will include inspection of all safety systems and a radiation exposure survey. The results of the survey will be kept on file in the Radiation Safety Office. Users of analytical equipment should also routinely perform radiation surveys. The surveys should include monitoring for stray radiation in the immediate vicinity of the X-ray apparatus.
    • 42. Copyright of Pickering Enterprises When the Operator Should Perform a Radiation Survey 1. Upon installation of your instrument. 2. After any major changes in equipment configuration or minor system maintenance to insure that no unanticipated exposure hazards exist. 3. Following any maintenance requiring the disassembly or removal of local components. 4. During the performance of maintenance and alignment procedures. 5. When visual inspection of the local components in the system reveals an abnormal condition.
    • 43. Copyright of Pickering Enterprises Survey Meter Instrumentation Survey should be performed with a portable Geiger-Mueller survey instrument although the results are not necessarily quantitative. If accurate measurements are desired, the instrument should be calibrated with the source of low energy X-rays. Consideration should also be given to possible monitoring errors due to the cross-sectional area of the monitored radiation beam being smaller than the sensitive area of the survey meter.
    • 44. Copyright of Pickering Enterprises General Precautions Only Trained personnel shall be permitted to operate an analytical unit. Be familiar with the procedure to be carried out. Never expose any part of your body to the primary beam. Turn the X-ray beam OFF before attempting to make any changes to the experimental set-up (except for beam alignment) While the beam is on DO NOT attempt to handle, manipulate or adjust any object (sample, sample holder, collimator, etc.) which is in the direct beam path (except for beam alignment procedures). Examine the system carefully for any system modifications or irregularities. Follow the operating procedures carefully. DO NOT take short cuts! Never leave the energized system unattended in an area where access in not controlled.
    • 45. Copyright of Pickering Enterprises General Precautions Survey the area frequently to evaluate scatter and leakage radiation fields. Never remove auxiliary shielding without authorization from the owner of the analytical equipment or Radiation Safety Officer. Never bypass safety circuits, such as interlocks. Report all unusual occurrences to the owner of the analytical unit for possible corrective actions. Only authorized, trained individuals as specified by the unit’s owner and the Radiation Safety Office may repair, align or make modifications to the X-ray apparatus.
    • 46. Copyright of Pickering Enterprises Designated Responsible Operator • Authorized by the Health Physics Committee • Ensures that only qualified individuals use the equipment • Maintains the equipment in compliance with safety requirements
    • 47. Copyright of Pickering Enterprises Limited Open X-ray Systems • Accessible area have exposure rates not exceeding 2 mR/hr (any area outside of the barrier or shield routinely occupied by personnel). • Maintain a log book of major changes to the system shielding, enclosures, and configurations. • Engineered protection system shall be maintained – Failsafe interlocks on removable protective barriers – Exposure rate below 2 mR/hr at 5 cm form any surface – Key control on the production of x-rays – A console power on indicator (must be operational and used) – Warning light adequate to warn anyone present in the room that x- rays are being produced.
    • 48. Copyright of Pickering Enterprises Exposure Potential • Fingers are at risk. – Significant injuries have occurred with diffraction x-rays. • Large exposures may occur. • Skin and eyes may receive exposures.
    • 49. Copyright of Pickering Enterprises General Methods of Protection • Time • Distance • Shielding
    • 50. Copyright of Pickering Enterprises Protective Devices & Procedures • Devices – Interlocks – Key control – Shielding • Procedures – Operating instructions – Training – Surveys – Exposure monitoring
    • 51. Copyright of Pickering Enterprises How to recognize failures • Interlocks don’t work. • Radiation is observed during surveys. • Unqualified people operating the system. • Redness of the skin, normally to the hand. • Warning light is not operational.
    • 52. Copyright of Pickering Enterprises Survey procedures & limitations • Perform the pre and post operational checks. • Record the results. • Make sure warning lights are working. • Wear your dosimeter. • Instruments record low readings.
    • 53. Copyright of Pickering Enterprises Use of radiation dosimetry • If you don’t use it, it will not provide useful information. • Wear it properly. • Don’t wear another persons film badge. • If you need additional devices, contact the RSO.
    • 54. Copyright of Pickering Enterprises
    • 55. Copyright of Pickering Enterprises X-ray Safety for Medical Personnel • Decrease dose to patient and the operator • Time – Determines total dose • Voltage – Determines penetration • Current – Determines dose rate
    • 56. Copyright of Pickering Enterprises Radiation Exposure from Diagnostic Medical X-ray Examinations in the U.S. (1980) Examination Type Effective Dose Equivalent (mrem) per Examination CT (head and body) 111 Chest 8 Skull 22 Cervical Spine 20 Biliary 189 Lumbar Spine 127 Upper Gastrointestinal 244 Abdomen (kidneys, ureters, bladder) 56 Barium Enema 406 Intravenous Pyelogram 158 Pelvis 44 Hip 83 Extremeties 1 Reference: NCRP Report No. 100, Exposure of the U.S. Population from Diagnostic Medical Radiation (1989).
    • 57. Copyright of Pickering Enterprises
    • 58. Copyright of Pickering Enterprises X-ray Safety for Medical Personnel Filtration removes low-energy x-rays from the primary beam. Collimation limits the beam to a useful area. Compliance testing performed periodically. Registration of sources with regulatory agency.
    • 59. Copyright of Pickering Enterprises Medial X-ray Shielding
    • 60. Copyright of Pickering Enterprises Structural Shielding Design Patient Employee-1 Employee-2 Secondary Barrier Primary Barrier X-ray Tube dsce dpri dsec
    • 61. Copyright of Pickering Enterprises
    • 62. Copyright of Pickering Enterprises

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