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Fluoroscopy%20Safety

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Title: Fluoroscopy%20Safety


1
Fluoroscopy Safety
  • Robert Metzger, Ph.D.

2
Introduction
  • On September 9th, 1994, the FDA issued an
    advisory for facilities that use fluoroscopy for
    invasive procedures. Recommendations.
  • Appropriate credentials and training for
    physicians performing fluoroscopy
  • Operators be trained and understand system
    operation, and implications of radiation exposure
    for each mode of operation
  • Physicians be educated in assessing risks and
    benefits on a case-by-case basis for patients
  • Patients be counseled regarding the symptoms and
    risks of large radiation exposures
  • Physicians justify and limit use of high dose
    rate modes of operation

3
Who Can Perform Fluoroscopy and Associated
Radiography?
  • Most states have regulations regarding the
    operation of radiation producing equipment and
    these regulations vary from state to state.
  • However, the fact is that many physicians who use
    fluoroscopy have essentially no training in this
    area.
  • In some states, it may be illegal for an
    untrained person to operate an x-ray machine even
    under the direct orders of a physician.

4
What should an operator know?
  • How to operate the machine
  • How to properly position the patient
  • How to minimize the use of radiation
  • How the radiation is distributed in the room
  • How to control the factors that optimize image
    quality (kVp, mA etc.)
  • How to control factors that reduce radiation
    levels (collimation)
  • How to properly use shielding devices and
    personnel monitoring devices

5
What an operator should know
  • Two professionals trained in specific aspects of
    fluoroscopy are the radiological technologist and
    medical physicist
  • Physician is ultimately responsible for assuring
    that the x-rays are safely and properly applied
    and that appropriate radiation protection
    measures are followed
  • Nurses or physician assistants should be trained
    in its safe and proper operation if asked to
    operate x-ray equipment

6
Skin Injuries
  • During the application of x-rays, the patient has
    no sensation of temperature rise in the skin,
    even if the patient is fully conscious and even
    for all but the most massive doses of radiation
  • Chronic exposure to low doses can also result in
    gradual erosion of tissue
  • Small doses from modern equipment might induce
    cancer, but the frequency of induction would be
    too low to detect a direct relationship with
    x-rays

7
Potential Effects in Skin in Fluoroscopy
c.f. Wagner and Archer. Minimizing Risks from
Fluoroscopic X-rays. 1996.
8
Skin Injuries Case Reports
Three weeks post rf cardiac catheter ablation
Ischemic dermal necrosis 5 months post procedure
Exposed to 20 minutes fluoro with elbow 20-25 cm
from focal spot. Note circular pattern coinciding
with x-ray beamport
Suggesting that the 18 Gy threshold was passed
during the procedure
c.f. Koenig TR, et al. Skin Injuries from
Fluoroscopically Guided Procedures Part 1,
Characteristics of Radiation Injury. AJR 2001,
177, pp. 3-11.
9
Skin Injuries Case Reports
Skin Injuries Case Reports
Deep ulceration with exposure of the humerus at
6.5 months post-procedure
Some radiation ulcers never heal completely, but
break down intermittently. Progression of the
ulcer may ensue and can be extensive, exposing
deep tissues such as tendons, muscles or bones.
c.f. Koenig TR, et al. Skin Injuries from
Fluoroscopically Guided Procedures Part 1,
Characteristics of Radiation Injury. AJR 2001,
177, pp. 3-11.
10
Skin Injuries Case Reports
Three transjugular intrahepatic portosystemic
shunt placements within a week
Injuries that are advanced to this stage require
surgical excision and grafting.
Non-healing deep tissue necrotic ulcer with
exposure of deep tissues, including spinous
processes of vertebra at 22 mos.
At 23 months, musculocutaneous skin grafting was
performed. Disfigurement is permanent.
c.f. Koenig TR, et al. Skin Injuries from
Fluoroscopically Guided Procedures Part 1,
Characteristics of Radiation Injury. AJR 2001,
177, pp. 3-11.
11
Radiation Injuries of the Skin
  • Many articles in literature about skin injuries
    (see Koenig manuscript)
  • Some case reports teach us two important lessons
  • Radiation dermatitis is delayed, from weeks to
    years after the exposure
  • Several procedures can result in very high
    cumulative doses to the same area if the skin
  • A conscientious effort should be made to avoid
    prolonged exposure to the same area of the skin
  • Documentation of certain conditions will help
    physicians if future procedures are needed
  • A careful record identifying the location of the
    exposed skin will alert other physicians about
    the need to avoid irradiation of the same area
  • A record of the estimated skin dose is also
    helpful

12
Controlling Image Quality, Dose, and Dose Rate
  • The following ten factors are the principal
    determinants of image quality, radiation dose
    rate and total radiation dose to the patient and
    to personnel during fluoroscopy ? the Ten
    Commandments
  • patient size
  • tube current (mA) and kVp
  • proximity of the x-ray tube to the patient
  • proximity of the II to the patient
  • image magnification
  • x-ray field collimation and use of a grid
  • shielding and position of personnel relative to
    patient and equipment
  • beam-on time

13
Commandment 1 Patient Size
  • Keep in mind that dose rates are greater and dose
    accumulates quicker for larger patients

14
Commandment 2 Tube Current (mA)
  • Keep the tube current as low as possible

15
Commandment 3 Tube Kilovoltage (kVp)
  • Keep the kVp as high as possible to achieve the
    appropriate compromise between image quality and
    low patient dose

16
Commandment 4 Proximity of x-ray tube to patient
  • Keep the x-ray tube at the maximal reasonable
    distance from the patient

17
Commandment 5 Proximity of the Image
Intensifier to the Patient
  • Keep the image intensifier as close to the
    patient as possible
  • To optimize image quality and reduce radiation
    dose
  • Optimize image quality ? distortion of anatomy
    and image blur decreases
  • Radiation Dose decrease ? x-ray intensity
    required to produce a bright image (automatic
    brightness control) decreases

18
Commandment 6 Image Magnification
  • Dont overuse the magnification mode of operation
  • Magnification can be achieved in 2 ways
  • magnification option on the image intensifier
  • geometric magnification

19
(6) Magnification
  • Magnification options of the image intensifier
  • This is achieved by making the x-ray field
    smaller and displaying the smaller field over the
    full viewing area of the monitor
  • The mode of least magnification (largest field)
    usually delivers the lowest dose rate
  • Sometimes the dose rate does not change with
    magnification but frequently, the dose rate
    increases with magnification
  • To optimize overall radiation management, use the
    lowest level of magnification consistent with the
    goals of the procedure and reduce the irradiated
    volume of the patient by employing narrow
    collimation

20
(6) Magnification
  • Geometric Magnification
  • Achieved by increasing the distance between the
    patient and the image intensifier (contrary to
    dose reduction method)
  • Geometric magnification can be used with
    isocentric systems
  • Dose typically increases with the square of the
    magnification
  • i.e., if magnification increases by 2x, dose rate
    goes up by 4x
  • Maximum dose rates in this configuration may
    exceed 10 R/min (legal entrance exposure limit)
  • this is because compliance dose rates are tested
    under conditions of least geometric magnification
    (patient closest to image intensifier)
  • Again, the minimum magnification consistent with
    the goals of the procedure should be used to
    manage radiation properly

21
Commandment 7 the Grid
  • Remove the grid during procedures on small
    patients, thin body parts or when the image
    intensifier cannot be placed close to the patient

22
Commandment 8 X-ray field Collimation
  • Always use tight collimation

23
Commandment 9 Distance Shielding
  • Personnel must wear protective aprons, use
    shielding, monitor their doses, and know how to
    position themselves and the imaging equipment for
    minimum dose

24
(9) Shielding and Distance
  • The principal source of radiation for the patient
    is the x-ray tube

25
(9) Shielding and Distance
  • The principal source of radiation for the
    operator and other personnel is scatter from the
    patient

26
(9) Shielding and Distance
  • One of the most important means by which
    personnel can reduce dose to themselves is by
    using shielding and properly positioning
    themselves relative to the patient and the
    fluoroscopic equipment
  • All personnel who are not positioned behind a
    radiation barrier must wear a lead apron during a
    procedure

27
(9) Shielding and Distance
  • Lead aprons
  • lead equivalency 0.25 mm to 0.50 mm
  • 0.25 mm absorbs gt 90 of scatter
  • 0.35 - 0.50 mm absorbs 95 - 99 of scatter (but
    heavier)
  • Lead aprons should be properly stored on a hanger
    when not in use
  • Aprons should be checked annually for holes,
    cracks or other forms of deterioration

28
(9) Shielding and Distance
  • Aprons do not protect the thyroid gland or the
    eyes.
  • Thyroid shields and leaded glass can be used
  • Leaded glass attenuates 30-70 depending on the
    content of lead in glass
  • Protective gloves of 0.5 mm lead of greater
    should be worn if hands are going to be near the
    primary beam (false sense of protection)

29
Protection of a Physicians Hands
  • Dermal atrophy of the forearm and hands were
    observed in physician who performed fluoroscopy
    for years Convinced some physicians to wear
    special radiation-attenuating surgical gloves or
    hand shields Such devices are not likely to
    protect hands if placed fully into the beam The
    automatic brightness control (ABC) detect the
    reduction in brightness due to the attenuation by
    the gloves and boost the radiation output to
    penetrate the protective gear Protective hand
    gear can be relied on only to protect against
    radiation outside the field of view of the ABC

30
Protection of Physicians Hands
  • To protect hands during fluoroscopy, it is
    recommended
  • Keep hands out of and away from the x-ray field
    when the beam is on unless physician control of
    invasive devices is requires for patient care
    during fluoroscopy
  • Work on the exit-beam side of the patient
    whenever possible
  • x-ray tube should be below table for vertical
    orientations
  • for oblique and lateral projections, stand on the
    side of the patient where the image intensifier
    is located
  • for adult abdomen, exit radiation is only about
    1 the intensity of the entrance radiation
  • extra care must be exercised in situations where
    physician must work on the x-ray tube side of the
    patient

31
Protection of Physicians Hands
  • To protect hands during fluoroscopy, it is
    recommended to
  • wear a ring badge to measure your hand exposure
    monthly
  • ring monitors dose only at the base of the finger
  • dose at the finger tips may be significantly
    higher

c.f. Wagner and Archer. Minimizing Risks from
Fluoroscopic X-rays Supplement 1. 1997.
32
(9) Shielding and Distance
  • All personnel who perform fluoroscopic procedures
    are required to wear a radiation monitoring
    device, usually a film badge
  • Personnel potentially exposed to 10 of the
    occupational annual limit (50 mGy or 5000 mrem)
    need a radiation badge
  • It is recommended that personnel wear their
    badges anteriorly on their collar outside of lead
    apron
  • Badge readings are monitored by the radiation
    safety office (RSO)

33
(9) Distance
  • Radiation Dose to personnel can be significantly
    reduced by increasing their distance from the
    radiation source
  • Inverse-square law the dose rate drops
    significantly as the distance from the source
    increases

34
(9) Distance
Given Exposure Rate at 2 ft
90 mR/hr.
3 ft
2 ft
9 ft2
4 ft2
1 ft
1 ft2
1 ft
2 ft
3 ft
2 ft
4 ft
6 ft
Exposure Rate at 4 ft (90 mR/hr)(2ft/4ft)2
22.5 mR/hr. Exposure Rate at 6 ft (90
mR/hr)(2ft/6ft)2 10 mR/hr.
35
(9) Radiation at 1 Meter From Patient
About 0.1 of patient entrance radiation exposure
reaches 1 meter from patient
1 m
x-ray
100
0.1
The NCRP recommends that personnel stand at least
2 meters from the x-ray tube, whenever possible.
(6 feet 1.82 m)
36
(9) C-Arm Fluoroscopy Shielding
  • With the C-arm oriented vertically, the x-ray
    tube should be located beneath the patient with
    the II above
  • In a lateral or oblique orientation, the x-ray
    tube should be positioned opposite the area where
    the operator and other personnel are working
  • In other words, the operator and II should be
    located on the same side of the patient
  • This orientation takes advantage of the patient
    as a protective shield

37
(9) The Separator Device (or Spacer Cone)
  • The FDA requires that fluoroscopic x-ray machines
    be designed so that the patients skin is at
    least a specified fixed distance from the X-ray
    source
  • The purpose of this regulation is to prevent the
    dangerous situation in which the intense beam
    emerging from the x-ray source is too close to
    the patients skin
  • To provide flexibility for some procedures, the
    FDA permits machines to be designed with
    removable spacers
  • For Dx procedures, the device is to remain
    attached to the x-ray source
  • For modern machines fixed in room, this distance
    is 38 cm
  • For mobile machines, this distance is 30 cm
  • For special surgical procedures the device may
    be removed and the minimum distance can be as
    short as 20 cm (potentially dangerous)

38
(9) The Separator Device (or Spacer Cone)
c.f. Wagner and Archer. Minimizing Risks from
Fluoroscopic X-rays Supplement 1. 1997.
39
Commandment 10 Beam On-Time
  • Keep beam-on time to an absolute minimum! - The
    Golden Rule
  • Control over beam on-time is almost always the
    most important aspect of radiation management It
    is essential practice to disengage fluoroscopic
    exposure when the image on the monitor is not
    being used Absentmindedly leaving the x-rays on
    while viewing other factors associated with the
    procedure, such as direct observation of the
    patient or communication with other personnel in
    the room, must be strictly avoided

40
Fluoroscopic Timer
  • A 5-minute cumulative timer is required on all
    fluoroscopic units to remind the operator audibly
    of each 5-minute time interval and to allow the
    technologist to keep track of the total amount of
    fluoro time for the exam

41
Good Vs. Bad Geometry Patient Dose and the
Position of the Fluoroscope
the Good
the Bad
c.f. Wagner and Archer. Minimizing Risks from
Fluoroscopic X-rays Supplement 1. 1997.
42
Good Vs. Bad Geometry Patient Dose and the
Position of the Fluoroscope
the Ugly
even Uglier
c.f. Wagner and Archer. Minimizing Risks from
Fluoroscopic X-rays Supplement 1. 1997.
43
Good Vs. Bad Geometry Summary
  • Differences in geometry of as little as a few
    centimeters can have a major impact on dose to a
    patients skin

c.f. Wagner and Archer. Minimizing Risks from
Fluoroscopic X-rays Supplement 1. 1997.
44
Good Vs. Bad Geometry Patient Dose and Physician
Height
c.f. Wagner and Archer. Minimizing Risks from
Fluoroscopic X-rays Supplement 1. 1997.
45
Good Vs. Bad Geometry Patient Dose and Physician
Height
30 dose reduction
c.f. Wagner and Archer. Minimizing Risks from
Fluoroscopic X-rays Supplement 1. 1997.
46
Good Vs. Bad Geometry Patient Dose and Invasive
Devices
  • In many invasive procedures, syringes, catheters,
    or other devices may be protruding from the
    patient With the patient prone on the procedure
    table, some distance must be maintained between
    the patient and the image intensifier to provide
    adequate working space In oblique orientations it
    is necessary to move the image intensifier to a
    position that avoids collisions with the patient
    and the invasive devices This may place severe
    constraint on how far the x-ray tube can be
    positioned from the patient For larger patients,
    the port of the x-ray tube may actually come into
    contact with the patients skin Extreme caution
    is advised in these situations to reduce the
    potential of inducing skin burns

47
Good Vs. Bad Geometry Invasive Devices and
Personnel vs. Patient Dose
c.f. Wagner and Archer. Minimizing Risks from
Fluoroscopic X-rays Supplement 1. 1997.
48
Good vs. Bad Geometry Recommendations on
Managing Risks from Geometry
  • Attach the separator cone to the port if at all
    possible
  • Move the x-ray tube away from the skin as far as
    practicable
  • Move the image intensifier as close to the
    patient as possible
  • Keep the beam-on time of the study as short as
    possible
  • If the image contrast is not affected, remove the
    grid
  • Routinely keep hands away from the imaged area
    and outside the housing of the image intensifier
  • Use collimation to control image quality and
    reduce scatter
  • Monitor hand dose
  • Step back from the patient before engaging
    fluoroscopy
  • Use a transparent shield for the head and neck if
    the x-ray tube is above the patient
  • Have assistants use extra shielding or stand well
    back from the patient if tube is above patient

49
Good vs. Bad Geometry Where Do Stand When Using
a C-Arm?
  • When using lateral and oblique projections, the
    scatter radiation and the primary beam are least
    intense on the exit beam side (image intensifier
    side) of the patient
  • For example, in the lateral orientation scatter
    is about 3 to 10x greater on the x-ray tube side
    than on the image intensifier side, depending on
    patient size and section of body irradiated
  • In many situations, it is required that the
    physician work on the x-ray tube side
  • For example, cardiologists work in a bi-plane
    configuration and stand next to the laterally
    projecting x-ray tube located on the right side
    of the patient, left side of cardiologist exposed
  • lead aprons and ceiling suspended radiation
    shields should be used to reduce exposure to the
    head and neck
  • radiation badge should be worn on the left side

50
Cataracts
  • Cataracts are a potential risk for patients
    undergoing high-dose interventional procedures in
    the head
  • The threshold for radiation-induced cataract is
    about 1 Gy
  • To reduce the potential for cataracts
  • for lateral orientation of the tube, the eyes can
    be shielded on the lateral side by using tight
    collimation to shield a large portion of the
    orbit that is closest to the x-ray tube
  • the frontal view should be performed with the
    x-ray tube posterior to the head and the image
    intensifier anterior. This ensures that the eyes
    receive only the much reduced exit beam dose and
    not the much higher entrance dose

http//www.optometry.co.uk/articles/20010406/brown
.pdf
51
Thoracic Fluoroscopy in Women
  • Breast cancer has been induced in women who
    underwent thoracic fluoroscopic evaluation for
    the treatment of tuberculosis
  • These women, for the most part, were positioned
    with their breasts facing the x-ray tube
  • This might occur with todays procedures if the
    x-ray c-arm is oriented for an oblique view
    through the thorax, perhaps to view the spine
  • breast could get exposed to high x-ray
    intensities
  • It may be reasonable to turn the c-arm over so
    that the x-ray tube is above the back of the
    prone patient
  • breast would receive only the reduced exit dose
  • Position the beam so that the breast is not in
    direct line with the x-rays or consider using
    tape or bandages to move some of the breast out
    of the direct x-ray beam

http//www.xray.hmc.psu.edu/rci/ss1/ss1_4.html
52
Dose Reduction by Heavy Filtration
  • Some modern fluoroscopy units now provide options
    for heavy x-ray beam filtration under some
    conditions (e.g., Philips Spectrabeam)
  • this filtration more effectively removes
    non-penetrating, dose-enhancing, low-energy
    x-rays than does conventional filtration
  • this results in reduced patient x-ray exposure
  • this heavy filtration typically consists of thin
    plates of copper inserted at the window of the
    x-ray source
  • To be effective, the tube current must be set
    very high
  • The physician should be aware that the equipment
    has this special feature and know when it is
    engaged so that unnecessary concerns over high
    tube currents can be avoided

53
Other Factors
  • Use modes of operation such as pulsed fluoro (30,
    15, 7.5 and 3.75 pulses per second) which reduce
    dose dramatically over continuous fluoro
    techniques
  • Try to avoid long exposure time to same skin area
  • Dont allow any extraneous body parts in the beam
  • Real-time dose monitoring is now standard on most
    newer fluoroscopic/angio/interventional systems
  • Try to avoid high skin dose modes of operation
    such as cine, high-level control if possible

54
Conclusions
  • Be smart about radiation and use common sense
  • Keep the beam-on time to a minimum
  • Consciously and conscientiously practice ALARA
  • Apply the risk-reducing factors (the Ten
    Commandments) discussed herein for the patients
    safety as well as your own
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