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Radiation Safety

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Title: Radiation Safety


1
Radiation Safety
  • Michael Shortsleeve, MD
  • Thomas Osborne, MD

MAH
2
Radiation Safetyoutline
  • 1. Background radiation to the general public
  • 2. X ray production and terms
  • 3. X ray interaction
  • 4. The Fluoroscopy machine
  • -And specific related exposure concerns
  • 5. Radiation Biology
  • 6. Tips to decrease patient and operator
    exposure

3
-U.S. Nuclear Regulatory Commission
Michael Shortsleeve, MD Thomas Osborne, MD
4
BackgroundX-ray Production
  • An electrically heated filament within the X-ray
    tube generates electrons
  • Electrons are then accelerated from the filament
    to hit a tungsten target
  • This is done with a high voltage potential in the
    tube

antonine-education.co.uk
Michael Shortsleeve, MD Thomas Osborne, MD
5
BackgroundX-ray Production
  • The quantity of electron flow, is the current
  • Described in units of milliamperes (mA)
  • The maximum kinetic energy of the accelerated
    electrons
  • Is defined in terms of kilovolts peak potential
    (kVp)

Energy kVp Amount ma
Michael Shortsleeve, MD Thomas Osborne, MD
6
BackgroundX-ray Production
  • Higher mA values more electrons more X-rays
  • The relationship is directly proportional
  • Increasing kVp an increase in the energy of
    the X-ray
  • However, this relationship is not directly
    proportional
  • The total number of X-rays produced at a set kVp
    depends directly on the product of the mA and
    exposure time and is described in terms of mA-s

Energy kVp Amount ma Total xrays mAs
Michael Shortsleeve, MD Thomas Osborne, MD
7
BackgroundDescription of Radiation Exposure Terms
  • X-ray machine output is described in terms of
    Entrance Skin Exposure (ESE) "table-top dose."
  • Amount of radiation delivered to the skin
  • Units of ESE are Roentgens per minute (R/min)

Wilhelm Conrad Röentgen
Michael Shortsleeve, MD Thomas Osborne, MD
8
BackgroundDescription of Radiation Exposure Terms
  • Patient radiation exposure is described in terms
    of radiation dose
  • Radiation dose is
  • The energy imparted per unit mass of tissue
  • And has the units of Rad
  • Rad is an acronym for Radiation Absorbed Dose
  • Immediate biological effects are described in
    terms of Rad

Michael Shortsleeve, MD Thomas Osborne, MD
9
BackgroundDescription of Radiation Exposure Terms
  • Occupational radiation exposure is also described
    in terms of radiation dose
  • However, the unit used is called the Rem
  • Roentgen Equivalent Man
  • Rems are synonymous with risk of latent Health
    effects
  • Dose equivalent was developed in an effort to
    incorporate biology into the physics of radiation
    exposure
  • For discussion 1 Rad 1 Rem

1 rem 1,000 mrem
1 chest X-ray about 6 mrem 1 CAT Scan about
110 mrem
Michael Shortsleeve, MD Thomas Osborne, MD
10
X ray interaction
  • X-rays have several fates
  • No interaction X-ray passes completely through
    tissue
  • To the image recording device
  • Complete absorption X-ray energy is completely
    absorbed
  • No imaging information results
  • Partial absorption with scatter Scattering
    involves a partial transfer of energy to tissue,
    a different trajectory
  • Degrade image quality
  • Primary source of radiation exposure to operator
    and staff

Michael Shortsleeve, MD Thomas Osborne, MD
11
X ray interaction
  • Probability of radiation interaction is a
    function of
  • Tissue electron density
  • Tissue thickness
  • X-ray energy (kVp)
  • Dense material attenuates more
  • Bone, barium, iodine
  • The differential rate of attenuation provides the
    contrast necessary to form an image

Michael Shortsleeve, MD Thomas Osborne, MD
12
X ray interaction Exposure
  • The primary beam X-rays travel in straight but
    divergent directions as they exit the X-ray
    machine
  • The degree of divergence increases with distance
    away from the X-ray origin (tungsten target)

1 chest X-ray about 6 mrem 1 CAT Scan about
110 mrem
Michael Shortsleeve, MD Thomas Osborne, MD
13
X ray interaction Exposure
  • Consequently, the number of X-rays traveling
    through a unit area decreases with increasing
    distance
  • Therefore, radiation exposure decreases with
    increasing distance
  • Exposure is directly proportional to the of
    X-rays/unit area
  • The inverse square law

1 chest X-ray about 6 mrem 1 CAT Scan about
110 mrem
Michael Shortsleeve, MD Thomas Osborne, MD
14
ExposureThe Inverse Square Law
  • XA the radiation exposure rate at distance DA
  • XB the radiation exposure rate at distance DB
  • Therefore doubling the distance from a radiation
    source decreases radiation exposure by a fourth

1 chest X-ray about 6 mrem 1 CAT Scan about
110 mrem
Michael Shortsleeve, MD Thomas Osborne, MD
15
ExampleThe Inverse Square Law
  • An operator normally stands 1 meter away
  • If the exposure rate at this point is 15 mrem/min
  • And if the total time is 2 min ( 30 mrem)
  • What is the reduction at 1.2 meters away?

1 chest X-ray about 6 mrem 1 CAT Scan about
110 mrem
Michael Shortsleeve, MD Thomas Osborne, MD
16
ExampleThe Inverse Square Law
  • An operator normally stands 1 meter away.
  • The exposure rate at this point is 15 mrem/min
  • Total time is 2 min. ( 30 mrem)
  • What is the reduction at 1.2 meters away?

A 31 percent reduction in radiation exposure is
achieved in this example.
1 chest X-ray about 6 mrem 1 CAT Scan about
110 mrem
Michael Shortsleeve, MD Thomas Osborne, MD
17
Fluoroscopy
  • X-ray tube (under table)
  • X-rays, captured by an Image Intensifier (above
    table)
  • Which converts the X-ray energy into light.
  • Light output is then distributed to a
    closed-circuit video
  • Output can also be distributed to a spot film or
    cine.
  • Although the output must be greater
  • 10 20 x greater with cine
  • Last Image Hold option

Saint Lukes Health System Fluoroscopy Users
Manual
Michael Shortsleeve, MD Thomas Osborne, MD
18
FluoroscopyScatter
  • Radiation is scattered in all directions
  • However, radiation levels are significantly lower
    above the table than below because of tissue
    attenuation in the forward direction

Michael Shortsleeve, MD Thomas Osborne, MD
19
FluoroscopyScatter
  • The scatter radiation profile tilts with the
    X-ray tube
  • Less exposure on the II side of the table when
    oblique angles are being imaged
  • tissue attenuation

Michael Shortsleeve, MD Thomas Osborne, MD
20
Fluoroscopy Field Size and Collimators
  • Larger field more tissue irradiated
  • Larger field increased scatter radiation
  • Some of this scatter will degrade the resulting
    image
  • Some of this extra scatter will enter you
  • Therefore, cone down the image

Michael Shortsleeve, MD Thomas Osborne, MD
21
Fluoroscopy Automatic Brightness Control (ABC)
  • ABC mode was developed to provide a consistent
    image quality during dynamic imaging
  • With ABC, output is adjusted automatically to
    bring the brightness to a constant, proper level
  • Ex when there is too much dark, the mA, kVp, or
    both, increase
  • The ABC compensates brightness loss caused by
    decreased xray reception by generating more
    X-rays
  • Therefore, a bigger patient or more dense
    material more exposure

Michael Shortsleeve, MD Thomas Osborne, MD
22
Fluoroscopy Magnification Modes
  • Magnification by electronically manipulating a
    smaller radiation II input area over the same II
    output area
  • The ABC system compensates for the lower output
    brightness by increasing radiation production and
    subsequent exposure to patient and staff

(Field-Of-View) ESE (R/min) Increase
Factor Normal (9 inch) 1.2 1.0 Mag 1 (6
inch) 2.9 2.4 Mag 2 (4.5 inch) 5.2 4.3
Michael Shortsleeve, MD Thomas Osborne, MD
Saint Lukes Health System Fluoroscopy Users
Manual
23
Fluoroscopy Magnification Modes
Michael Shortsleeve, MD Thomas Osborne, MD
Saint Lukes Health System Fluoroscopy Users
Manual
24
Radiation BiologyStochastic Effects
  • Carcinogenesis
  • A non-threshold linear response to the
    dose-effect relationship
  • 1 rem to 1 million persons would result in an
    increase in cancer deaths from 190,000 to 190,400
  • increase of 0.2

National Council on Radiation Protection and
Measurements. Recommendations on limits for
exposure to ionizing radiation, NCRP Report No.
91, Bethesda, MD,1987.
Michael Shortsleeve, MD Thomas Osborne, MD
25
Radiation BiologyDeterministic Effects
  • Effects that appear only above a threshold dose
  • The threshold may vary from person to person
  • The severity of these effects increases with
    increasing dose above the threshold
  • Most of these deterministic effects are seen
    within days or weeks after the exposure, but
    cataracts may appear a few years after exposure

Michael Shortsleeve, MD Thomas Osborne, MD
26
Radiation BiologyDeterministic Effects
Effect Threshold Hours of Fluoro Hours of
Cine effect (rad) 5 R/min 30
R/min Transient Erythema 200 0.7 0.1 24
hr Epilation 300 1 0.2 3 wk Erythema 600 2
0.3 10 day Pericarditis 800 2.7 0.4 gt10
wk Dermal Necrosis 1800 6 1 gt10 wk
Saint Lukes Health System Fluoroscopy Users
Manual
Michael Shortsleeve, MD Thomas Osborne, MD
27
Symptomatic Skin Reactions
  • Two case reports
  • Unfortunately, many more in the literature

Michael Shortsleeve, MD Thomas Osborne, MD
28
Symptomatic Skin Reactions
Case Report 1
  • On March 29, 1990, a 40-year-old male underwent
    coronary angiography, coronary angioplasty
  • And a second angiography procedure (due to
    complications) followed by a coronary artery
    by-pass graft.
  • Total fluoroscopy time estimated to be gt 120 min

Thomas B. Shope, Ph.DScientific Exhibit 060PH at
the 81st Scientific Asssembly and Annual Meeting
of the Society of North America, November 26 -
December 1, 1995. Radiology Vol. 197(P)
Supplement, P449
Michael Shortsleeve, MD Thomas Osborne, MD
29
Symptomatic Skin Reactions
Case Report 1
  • 7 w following the procedures

Thomas B. Shope, Ph.DScientific Exhibit 060PH at
the 81st Scientific Asssembly and Annual Meeting
of the Society of North America, November 26 -
December 1, 1995. Radiology Vol. 197(P)
Supplement, P449
Michael Shortsleeve, MD Thomas Osborne, MD
30
Symptomatic Skin Reactions
Case Report 1
  • 21 M following the procedures

Thomas B. Shope, Ph.DScientific Exhibit 060PH at
the 81st Scientific Asssembly and Annual Meeting
of the Society of North America, November 26 -
December 1, 1995. Radiology Vol. 197(P)
Supplement, P449
Michael Shortsleeve, MD Thomas Osborne, MD
31
Symptomatic Skin Reactions
Case Report 1
  • Following skin grafting procedure

Thomas B. Shope, Ph.DScientific Exhibit 060PH at
the 81st Scientific Asssembly and Annual Meeting
of the Society of North America, November 26 -
December 1, 1995. Radiology Vol. 197(P)
Supplement, P449
Michael Shortsleeve, MD Thomas Osborne, MD
32
Symptomatic Skin Reactions
Case Report 2
  • Pt had a 20 min cardiac catheter ablation
  • Prior to the procedure the separator cones were
    removed so that the fluoroscopic c-arms could be
    easily rotated around the patient
  • The separator cone is a spacer attached to the
    tube housing designed to keep the patient at a
    reasonable distance from the x-ray source
  • This is done specifically to avoid the high
    skin-dose rates that can be encountered near the
    tube port

Benjamin R. Archer Louis K. Wagner Protecting
patients by training physicians in fluoroscopic
radiation management, Journal of Applied Clinical
Medical Physics, Vol.1, No.,1, Winter, 2000.
Michael Shortsleeve, MD Thomas Osborne, MD
33
Symptomatic Skin Reactions
Case Report 2
  • During the procedure, the right arm moved into
    the field
  • However, personnel were not aware of this change
    because sterile covers were draped over the
    patient

Benjamin R. Archer Louis K. Wagner Protecting
patients by training physicians in fluoroscopic
radiation management, Journal of Applied Clinical
Medical Physics, Vol.1, No.,1, Winter, 2000.
Michael Shortsleeve, MD Thomas Osborne, MD
34
Symptomatic Skin Reactions
Case Report 2
  • 3 w s/p the procedure
  • Bright erythema

Benjamin R. Archer Louis K. Wagner Protecting
patients by training physicians in fluoroscopic
radiation management, Journal of Applied Clinical
Medical Physics, Vol.1, No.,1, Winter, 2000.
Michael Shortsleeve, MD Thomas Osborne, MD
35
Symptomatic Skin Reactions
Case Report 2
  • 3 w s/p the procedure
  • Bright erythema
  • 5 m s/p procedure
  • A large ulcer the size of the collimated x-ray
    port

Benjamin R. Archer Louis K. Wagner Protecting
patients by training physicians in fluoroscopic
radiation management, Journal of Applied Clinical
Medical Physics, Vol.1, No.,1, Winter, 2000.
Michael Shortsleeve, MD Thomas Osborne, MD
36
Symptomatic Skin Reactions
Case Report 2
  • 3 w s/p the procedure
  • Bright erythema
  • 5 m s/p procedure
  • A large ulcer the size of the collimated x-ray
    port
  • 8 m, s/p procedure
  • Debridement

Benjamin R. Archer Louis K. Wagner Protecting
patients by training physicians in fluoroscopic
radiation management, Journal of Applied Clinical
Medical Physics, Vol.1, No.,1, Winter, 2000.
Michael Shortsleeve, MD Thomas Osborne, MD
37
Symptomatic Skin Reactions
Case Report 2
  • 3 w s/p the procedure
  • Bright erythema
  • 5 m s/p procedure
  • A large ulcer the size of the collimated x-ray
    port.
  • 8 m, s/p procedure
  • Debridement and a surgical flap

Benjamin R. Archer Louis K. Wagner Protecting
patients by training physicians in fluoroscopic
radiation management, Journal of Applied Clinical
Medical Physics, Vol.1, No.,1, Winter, 2000.
Michael Shortsleeve, MD Thomas Osborne, MD
38
How to decrease overall exposure
  • ALARA concept
  • i.e. As Low As Reasonably Achievable

Michael Shortsleeve, MD Thomas Osborne, MD
39
Decrease patient exposure
  • Caution modifying equipment
  • Decrease fluoro time
  • Last image hold
  • Pulsed fluoro
  • Decrease II patient gap
  • Cone down image (lead shutters)
  • Avoid mag views
  • Avoid cine run

Michael Shortsleeve, MD Thomas Osborne, MD
40
Decrease personnel exposure
  • Decrease patient exposure
  • Increase distance
  • Avoid x-ray tube side of table
  • Shield
  • Lead Aprons, gloves, glasses
  • Fluoro on!

Michael Shortsleeve, MD Thomas Osborne, MD
41
Decrease complications
  • History of prior radiation therapy
  • 10 day rule for women of childbearing age

Michael Shortsleeve, MD Thomas Osborne, MD
42
Conclusion
The risk of adverse radiation effects originating
from a medically necessary procedure is almost
always offset by the benefit received by the
patient However, inadequate training can produce
patient and staff doses that lead to serious
consequences
43
ConclusionIn this talk we covered
  • 1. Background radiation to the general public
  • 2. X ray production and terms
  • 3. X ray interaction
  • 4. The Fluoroscopy machine
  • -And specific related exposure concerns
  • 5. Radiation Biology
  • 6. Tips to decrease patient and operator
    exposure

44
Radiation SafetyThe End
Thank You
Michael Shortsleeve, MD Thomas Osborne, MD
45
Decrease personnel exposure
Decrease patient exposure
  • Caution modifying equipment
  • Decrease fluoro time
  • Last image hold
  • Pulsed fluoro
  • Decrease II patient gap
  • Cone down image (lead shutters)
  • Avoid mag views
  • Avoid cine run
  • Decrease patient exposure
  • Increase distance
  • Avoid x-ray tube side of table
  • Shield
  • Lead Aprons, gloves, glasses
  • Fluoro on!

Michael Shortsleeve, MD Thomas Osborne, MD
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