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Radiation and Catheterization Lab Safety


Title: Radiation and Catheterization Lab Safety Author: Cardiology Last modified by: PBarrows Created Date: 7/1/2004 8:16:35 PM Document presentation format – PowerPoint PPT presentation

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Title: Radiation and Catheterization Lab Safety

Radiation and Catheterization Lab Safety
  • Joan E. Homan, M.D.
  • Cardiology Fellow

Catheterization Lab Safety Objectives
  • Definitions
  • Basic science
  • Safety

Radiation - Terms
  • Dose
  • Exposure and exposure rate
  • Absolute dose
  • Dose equivalent

Radiation - Terms
  • Exposure
  • the amount of ionizing radiation a person is
    exposed to
  • expressed as roentgens (R)
  • Can be directly measured and is expressed as
    R/minute or milli-R/hour

Radiation - Terms
  • Absorbed Dose
  • The amount of energy deposited in tissue, (the
    amount of radiation needed to transfer a certain
    amount of energy (1 joule/kg)).
  • Expressed as gray (Gy) or rad (1 gray 100 rad)
  • Absorbed dose varies with type of tissue
  • i.e. bone 5.0 soft tissue 0.95

Radiation - Terms
  • Dose Equivalent
  • The absorbed dose multiplied a quality factor
    allowing for different tissue sensitivities
  • Expressed as sievert (Sv) or rem (1 sievert 100
  • Used to account for different biological effects
    of radiation
  • Rad, rem and roentgen have approximate numerical
    equivalence in the x-ray energy range used in the
    cardiac catheterization lab.

  • Production
  • Current is applied to a filament
  • Electrons are released and accelerated towards a
    target by a high-voltage electrical potential
  • X-rays are produced when
  • Electrons collide and are completely stopped by
    the target (characteristic x-rays)
  • Electrons are rapidly decelerated after striking
    the target (braking x-rays)

X-Ray Tube Assembly
  • transmitted radiation

Absorbed radiation
Target (ie patient)
Scattered radiaion
High voltage lead
Image Acquisition
  • Fluoroscopy type of x-ray examination used for
    dynamic imaging
  • Image intensifiers - amplify the brightness of
    the image to improve visibility
  • X-rays transmitted through patient, enter the
    input phosphor which emits light that is then
    converted to electrical energy
  • The electrical energy is amplified and converted
    back into light at the output phosphor
  • Output phosphor of the image intensifier is
    coupled to a television pickup tube which
    converts the light pattern into an electrical
    signal which forms the image on the monitor

TV Monitor
Video camera
Video Recorder
Image intensifier
Fluoroscopy Imaging System
X-ray tube
(No Transcript)
Cine Angiography
  • Light exiting the output phosphor is divided,
    diverting part of the beam to TV monitor and the
    rest to the cine camera lens refocuses light
    onto cine film
  • Standard cameras use 35mm film at frame rates of
    15-60frames/sec (15-30fps for angiography and
    60fps for ventriculography)

Environmental Radiation Exposure (mrem/year)
  • Natural Background
  • Cosmic rays 30-70
  • External terrestrial 10-100
  • Internal 10-20
  • Radon 200
  • Medical sources
  • X-rays 39
  • Radiopharmaceuticals 14
  • Man-made Sources
  • Fallout 3
  • Nuclear industry lt1
  • Consumer products 3-4
  • Airline travel 0.6
  • Total 360

Radiation Dose and Dynamics
  • Limit of 10 R/minute
  • Patient radiation dose dependent on several
  • X-ray tube factors
  • Image intensifier factors
  • Distance factors
  • Patient factors

X-ray tube factors
  • Operator independent
  • kVp voltage across the x-ray tube, the energy
    that accelerates the electrons
  • Intensity of x-rays and image brightness directly
    related to the current passing through the
  • Increasing the kVp produces higher energy x-rays
    which have greater penetrating power for larger
  • Optimal setting for adults 70-80kVp
  • Copper or aluminum filters placed between x-ray
    tube and patient to absorb low energy x-rays that
    are inadequate for imaging purposes

Image quality
  • Automatic brightness control automatically
    adjusted to maintain brightness
  • Collimation
  • restrict the size of the x-ray field
  • Field Size and Magnification
  • Field size decreases with magnification,
    therefore, the local patient radiation dose must
    increase to compensate for the loss of brightness
  • Low magnification (9-11 inch)
  • Intermediate magnification(6-7 inch)
  • High magnification (4-5 inch)

Image intensifier factors
  • Skin exposure
  • 1-2R/min in 9 inch mode
  • 2-5R/min for smaller magnification modes
  • For 10 minutes of fluoroscopy, patients skin
    exposure is 10-50R (10-50rads)

Image Intensifier Magnification Modes
Same area
Output phosphor
Input Phosphor
9 inch field
6.5 inch field
  • Skin radiation increases with decreasing distance
  • Table height (height of operator) affects patient
  • Standard is to maintain 18 between x-ray tube
    and patient
  • Image intensifier should be as close to patient
    as possible

Exposure factors
  • Prolonged or repeated cine runs
  • Longer fluoroscopy times
  • Higher frame rates
  • All increase radiation exposure to the patient

Patient Factors
  • Age
  • Health of patient
  • Skin site

Recommended Dose Limits for Occupational Exposure
to Ionizing Radiation
  • Effective Dose Limits - Occupational
  • Annual 5000 millirem
  • Cummulative 1000 millirem x age
  • Annual Dose Limits for Tissues Occupational
  • Lens of eye 15,000 millirem
  • Skin, hands, feet 50,000 millirem
  • Embryo fetus, total 500 millirem
  • Embryo fetus, monthly 50 millirem
  • Annual Public Exposure Nonoccupational
  • Annual effective dose 100-500 millirem
  • Lens of the eye 1500 millirem
  • Skin, hands, feet 5000 millirem

Radiation Biology
  • Radiation Injury
  • Damage and repair
  • Somatic effects
  • Effects on developing embryo and fetus

Damage and Repair
  • Injury produced by large amounts of energy
    transferred to individual molecules
  • Causes ejection of electrons
  • Initiates physical and chemical effects on
    tissues especially DNA
  • Failure of repair mechanism leads to
  • Cell death or
  • Mutation

Radiation Damage and Repair
  • Effects to tissue depend on
  • Amount of energy imparted
  • Location and extent of region of body exposed
  • Time interval over which energy is imparted

Radiation Biology
  • Deterministic effects those in which the number
    of cells lost in an organ or tissue is so great
    that there is a loss of tissue function
  • IE skin erythema and ulceration
  • Stochastic effects occur if an irradiated cell
    is modified rather than killed and then goes on
    to reproduce
  • Do not appear to have a threshold and the
    probability of the effect occurring is related to
    the radiation dose

Somatic Effects
  • Observed early (days to weeks)
  • Early effects develop in proliferating cell
    systems (most radiosensitive skin, ocular lens,
    testes, intestines, esophagus)
  • OR
  • Observed late (months to years)
  • Carcinogenesis is the most important delayed
    somatic effect
  • Delayed effects often seen in nerves, muscles and
    other radioresistant tissues

Groups at Increased Risk
  • Five groups of patients known to have genetic or
    chromosomal defects and an increased sensitivity
    to various types of ionizing radiation
  • Xeroderma pigmentosum
  • Ataxia-telangiectasia
  • Fanconis anemia
  • Bloom Syndrome
  • Cockaynes syndrome

Direct Radiation Effects
  • Determined by dose
  • Bone marrow depression with whole body radiation
    gt 500 rad
  • Skin erythema occurs if a single dose of 6 8 Gy
    (600-800 rad) is given, and it is not identified
    until 1-2 days after irradiation
  • The higher the irradiation dose, the more quickly
    the erythema may be identified

Skin Erythema
  • Characterized by a blue or mauve discoloration of
    the skin
  • Increases during the first week
  • Usually fades during the second week
  • May return 2-3 weeks after the initial insult and
    last for 20-30 days
  • Acute doses in excess of 8 Gy will produce
    exudative and erosive changes in the skin
  • Penetrating doses in excess of 20 Gy there is
    usually a nonhealing ulceration

Skin Edema
  • May appear in a few hours or a few weeks
  • The higher the dose, the shorter the period for

Skin Injury by Type
  • Type I injury damage limited to the epidermis
    and dermis without much damage to the
    subcutaneous tissues
  • Initial erythema
  • A 3-wk latency period
  • A secondary erythema followed by
  • An exudative epidermatitis and recovery in 3-6

Skin Injury by Type
  • Type II Injury
  • A vascular endothelitis
  • At least 6-8 months post exposure the acute
    reactions are renewed with necrosis and
    ulceration usually requiring surgery
  • A result of damage below the basal layer of the

Type III Injury
  • Necrosis within a few weeks of the acute exposure

Radiation Safety and Protection
  • Lab specific
  • Constructed with 1.5mm of lead or equivalent
    shielding to protect individuals in the control
    room and adjacent areas

Radiation Safety and Protection
  • Personal protection
  • Time
  • Distance
  • Shielding

Radiation Safety and Protection
  • Time
  • Radiation dose is proportional to exposure
  • Distance
  • Radiation dose is inversely proportional to the
    square root of the distance from the patient (or

Radiation Safety
  • Shielding
  • Lead is the most common material used
  • A lead apron with an equivalent of 0.5mm of lead
    in front panel is mandatory
  • Lead in the back panel provides additional
  • Thyroid shield (0.5mm equivalence) is recommended
    to shield the sternum, upper breast and thyroid

Radiation Safety
  • Shielding continued
  • Leaded eyeglasses with the side shields reduce
    the exposure to the eyes and may improve visual
  • Recommended for staff with collar-badge doses
    approaching 15rem per year and for
    interventionalists in training

Radiation Safety
  • Shielding continued
  • Hands receive the highest radiation dose, but are
    relatively insensitive to radiation
  • Supplemental lead shielding to reduce exposure to
    scatter is available in the form of table mounted
    lead drapes, ceiling mounted lead acrylic shields
    and rolling lead acrylic shields

Personnel Dosimetry
  • Interventionalists commonly assigned 2 radiation
  • One on collar
  • Second underneath lead apron
  • Lead apron reduces the radiation dose at the
    waist to 10 of dose at collar at 75kVp.
  • Effective dose equivalent best estimated by
    averaging the 2 dosimeters
  • Mean dose equivalent per procedure 4 /- 2
    millirem, highest doses were delivered to
    physicians in training (5 rem per year)

Radiation Safety
  • Women of child-bearing age should receive a
    pregnancy test prior to procedure
  • Current regulations restrict radiation dose to
    the embryo and fetus to 500millirem for the
    entire gestation and a monthly dose lt 50 millirem
  • Pregnancy does not exclude working in the cardiac
    catheterization lab
  • Highest danger of fetal abnormalities is in the
    first trimester
  • Maturity lead aprons provide an additional 1mm of
    lead equivalence
  • Use of properly fitting wrap-around apron
    provides same protection to the fetus
  • Fetal radiation badge should be worn on the
    abdomen under the apron to record monthly fetal

The End
  • Braunwald, et al. Heart Disease, A textbook of
    Cardiovascular Medicine, 6th Edition, WB Saunders
    Company, 2001.
  • Mettler,FA, Upton, AC. Medical Effects of
    Ionizing Radiation, 2nd Edition, WB Saunders
    Company, 1995.
  • Mettler, FA, Voelz, GL. Current Concepts Major
    Radiation Exposure What to Expect and How to
    Respond. NEJM 2002 346(20)1554-1561.
  • Safian, RD Freed, MS. The Manual of
    Interventional Cardiology, 3rd Edition,
    Physicians Press, 2001.
  • Shapiro, J. Radiation Protection, A Guide for
    Scientists, Regulators and Physicians, 4th
    Edition, Harvard University Press, 2002
  • Wilde, P Pitcher, EM Slack, K. Radiation
    hazards for the patient in cardiological
    procedures. Heart 2001 85(2) 127-130
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