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