Cath Lab Radiation Safety Cath Lab Radiation

							  Cath Lab:
Radiation Safety
Mireya Canate, SSG, USA, CVT, CS, EMT-B
                 OBJECTIVE

               • Brief understanding of x-rays

• All members of cardiac lab support teams are required to be
   educated about hazards and exposure to ionizing radiation
               History Lesson
• 1895 - Wilhelm Roentgen
  discovered X-rays
• 1896 - First cases of somatic
  damage caused by ionizing
  radiation reported
• 1904 - Clarence Dally
  becomes first American
  radiation fatality
• 1910 - Cancer deaths
  among Physicians
  attributable to X-ray reported
              Radiation Terms
• Stochastic – all or none effect from radiation (ie;
  cancers, genetic effects)
  DNA INJURY

• Nonstochastic (Deterministic) – effect is dosed
  dependant (ie; eyes, marrow, gonads, skin).
  Cell Death



REMEMBER
ALARA!
           Properties of X-rays
• Travel at the speed of
  light
• Travel in a straight line
• Cannot be focused or
  refracted
• Ionizing radiation
• Can be scattered
• Expose photographic film
• Cause certain materials
  to fluoresce
• State laws control
  administration
        Quick ABC’s Of X-ray
           Rotating
                        Heat
            Anode

Power

                               Electrons

                               Cathode
                      X-Rays
Image Intensifier
          Protective housing
Composed of cast steel lined with lead
• Window that allows X-ray beam to exit
• Function
  – Keeps X-radiation contained
  – Inhibits “leakage”
  – Isolates the high voltages
  – Assists in cooling the tube
• Leakage is not permitted to exceed
  100mR/hr at 1 meter at max kVp and mA
          X-Ray Beam--Two Properties

•Quantity = mA (milliamperage)
  mAs directly effects
  Radiographic density
  Patient dose / patient exposure
  Heat unit build-up

•Quality = kV (kilovoltage)
  kV effects
  Quality of the x-ray beam (penetrating ability)
  Radiographic contrast
        Primary & Remnant Beam
•   Primary- the X-ray beam that exits the tube and strikes the patient
•   X-rays can pass through, be absorbed, attenuated or scatter in the patient
•   Remnant- the X-ray beam that exits the Patient and strikes the Image
    Intensifier
        Differential absorption
• Different tissue densities and thickness' absorb
  X-radiation in different levels
• Denser tissues or thicker tissues absorb more
  radiation
• The different levels of radiation exiting the body
  produce the gray scale in the radiograph
  Hardening of the X-ray beam
• Aluminum filters remove low energy X-rays from
  beam
• Reduces scatter and patient/staff exposure
             Density & Contrast
• Density
  – Degree of blackening
  – Darker the film, higher the density
• Contrast
  – Differences in densities between two adjacent parts of
    a radiograph
  – High contrast images are mostly black and white
  – Low contrast images are mostly grays with few blacks
    and whites
             Digital Imaging
                           1   0 .75 0.5     0.25
• Break the image into     .75 0 .75 0.5
                           0
                                             0.25
                                                  
  small pixels              .5 0 .5 0.5
                            0                 0.25
                                                 
• Assign a number to       .25 0 .25 0 .25
                           0                  0.25
  each shade of white,
  grey and black or
  color
                               
                               1   0   1   0
                               
                               0   1   0   0
                                           
                               
                               1   0   1   0
                                           
                               
                               0   0   0   0
                 Digital Imaging

22 23 10 20 14
25 3 8 5 17
15 6 1 2 11
12 9 4 7 21
18 19 13 24 16
Source-Image
Distance
       Monitoring Devices

• Film badge
• Thermoluminsecent
  dosimeter (TLD)
• Pocket ionization
  chamber
              Film Badges
• plastic holder containing film that measures
  “hard” and “soft” radiation
• not the most accurate +/- 20% error
• most economical while still providing acceptable
  accuracy
• measures accumulated dose for one month
      Dose Equivalent Limits
• maximum dose of ionizing radiation that an
individual may accumulate over a long period of
time or in a single exposure and which carries a
negligible risk of significant bodily or genetic
damage
• Occupational exposure
  -limits given for annual and cumulative
exposure
        Dose Equivalent Limits
 Maximum dose for occupational exposure
• Annual: 5 REM (5,000mREM)
• Cumulative: 1 REM x current age
• Skin, hands,feet tolerate more exposure-
     50 REM annual
•Pregnant: 500mrem for total pregnancy
    Tissues Sensitive to Dose
• Gonads
• Thyroid
• Bone marrow
  – Sternum
  – Pelvis
  – Long bones
• Eyes
• Blood forming organs
  – spleen
    Three Principals of Radiation
             Protection
 Time: reduce the amount of time you are
near the patient’s head during fluoro or
cine.
 Distance: Put as much distance between
you and the tube as possible (Inverse
Square Law).
Shielding: Wear your lead aprons and
wear them correctly.
HONU, North Beach,
    Oahu, HI
        Factor #1:
Patient Size - Larger patient

              • Personnel doses
                increase due to:
                 – higher kV & mA
                 – more patient scatter
                 – longer beam on time
             Factor #2:
 Proximity of X-Ray Tube to Patient

Move Tube Away from the patient
  – Reduces patient skin dose rate due to lower
    intensity X-Rays & reduces chance of skin
    burn

  – Area of skin irradiation increases & Dose Area
    Product (DAP) remains constant
              Factor #3:
Proximity of the Image Intensifier (II)
        or Flat Panel Detector
 • Must be as close as possible to the patient to
   reduce radiation dose and increase image
   clarity
                  Factor #4:
            Image Magnification
• Magnification increases
  dose rate to the
  patient’s skin
• Use least magnification
  consistent with the goal
  of the procedure
• Use narrowest
  collimation to reduce
  scatter
Factor #5: Collimation
       • Collimate down to area of
         interest:
         – improves image quality
           (reduced scatter)
         – reduces patient cancer risk
           (less Dose Area Product)
         – reduces dose to personnel
           in the room (reduced
           scatter)
          Factor #6:
         Beam on Time

Control over beam-on time
is almost always the most
important aspect of
radiation management
          Factor #7:
More about Distance and Shielding
                       • Inverse
                         square law -
                         R=1/D2
                       • Distance helps
                         reduce
                         exposures
                         significantly

                       • Note effect of
                         equipment as
                         shield
                   Distance effect

Use the inverse square law to your advantage and
whenever possible move away from the x-ray source
as far as safety allows.

    Distance
   from Beam       1 step 2 steps 3 steps 4 steps
     Relative
   Exposure Rate    100     25      11       6
     Patient Exposure:
It’s All About Penetration
   Where Does Scatter Come From?
      Stray Radiation Sources

X-Ray tube leakage
 Scatter from patient
and objects exposed to
primary beam
Note: Patient does not uniformly emit
scatter radiation. Some of the scatter
radiation is absorbed or reduced in
intensity by passing through the patient.
        Scatter Distribution & You

Scatter intensity is
highest on the entrance
side of the patient.

  primary beam most intense on
entrance side
  forward scatter is heavily
attenuated
Stray Radiation: Horizontal
         Profile
Stray Radiation: Vertical Profile
       Stray Radiation: Lateral Profile
             Tube by Operator
Scatter at
 100cm




                                  Distance from
                                  Table Center
                                       (cm)




 Distance from
Central Ray (cm)
        Stray Radiation: Lateral Profile
           Tube Opposite Operator
Scatter at
 100cm



                                   Distance from
                                   Table Center
                                        (cm)




 Distance from
Central Ray (cm)
Effects of Different Projections
   LAO                   RAO
            Higher Eye       Lower Eye
             exposure        exposure
Exposure by Patient Size: Average




                                         Distance from the floor (cm)
        Distance from Central Ray (cm)
Exposure by Patient Size: Large




                                        Distance from the floor (cm)
       Distance from Central Ray (cm)
Exposure by Patient Size: X-Large




                                       Distance from the floor (cm)
      Distance from Central Ray (cm)
     Lower The Image Intensifier

                                   ♥Reduces patient
                                   exposure
                                   ♥Reduces staff
                                   exposure
                                   ♥Improves image
                                   quality




 More noise      Best Practice:
from scatter   Enhanced Exposure
            Image Intensifier Positioning




Scatter Rate   9.9          6.5             3.6
(mGy/hr):
        Table Height Reduces Exposure




Scatter Rate 7.3      6.1         4.3
(mGy/hr):
How Table Shielding Reduces Scatter

                          Without Table Shield




      With Table Shield
Proper Use of Shield
      Reduces
     chances for
     cataracts by
     reducing
     exposure to eyes
      Reduces
     exposure to
     hands & arms
      Reduces
     exposure to chest
     and thyroid
         Protective Clothing
• Well tailored apron
• Thyroid collar
• Eye protection
               Lead Aprons
• need to cover sternum to knees
• minimum .5mm lead
equivalency
• wrap around preferable,
  limitations of a front only apron
• need to be taken care of
properly
• fluoroed periodically to ensure
integrity
   Lead Aprons: Do You Wear
        Yours Correctly?
     Proper Fit is Critical

♥If 2 layers are needed to
meet 0.5 mm lead-equivalent
requirement, make sure
overlap is sufficient

♥Arm holes should not be too
wide

♥Neck line should not fall too
low

♥Film badges worn outside
lead apron
                                 Lead Apron Effectiveness
                                                                        99%     94%
                                100%
X-Ray Shielding Effectiveness
                                                         88%
                                                                  75%
                                80%
                                       66%
                                               51%
                                 60%


                                40%



                                20%


                                 0%
                                        0.25                0.5               1.0


                                             Apron Thickness (mm Pb)
         Lead Thyroid Collars

• worn to cover thyroid
• minimum .5mm lead
equivalency
• need to be taken care of
properly
• fluoroed periodically to ensure
integrity
           Lead Apron Care
♥Always hang up your
 lead after use
♥Do not bunch it up or
 throw to the ground
♥Lead aprons should be
 checked annually for
 cracks
♥Do not leave your film
 badge on your lead
                    Lead Glasses
• worn to protect eyes
• side shields provide increased
protection
• minimum .6mm lead equivalency
• regular glass lens provide 1/4
radiation protection of lead lens
• plastic lens provide no radiation
protection
• wear lead glasses or goggles over
prescription glasses if possible
     Comparing Risk Factors
   Risk Factor         Days of Life Lost
     Smoking                2,370
Overweight by 20%            830
   All Accidents             435
Average Alcohol Use          130
1 rem/y for 30 years          30
Natural Background            8
     Radiation
              Natural Radiation
               ~300 mrem/year


Cosmic rays          Air (radon)
 28 mrem
                                   200 mrem




                               Food
                              40 mrem
 Ground
 28 mrem
Manufactured sources of radiation
contribute an average of 60 mrem/year


cigarette smoking - 1300 mrem   round trip US by air
                                   5 mrem per trip




   medical - 53 mrem            smoke detectors
                                   0.0001 mrem

building materials - 3.6 mrem    fallout < 1 mrem
        Miscellaneous Facts
 Average Background        0.1 rem/year
      Radiation

    Interventional      0.004 to 0.016 rem
     Cardiologist            Per case
                            5 rem/year
Occupational Exposure       Total Body
         Max
                         0.05 rem/month or
 Fetal Exposure Max     <0.5 rem/pregnancy
            ALARA Concept
• “As Low As Reasonably Achievable”
• Follows along the Physician credo of “First
  Do No Harm”
• Refers to our responsibility to the patients
  we treat to limit their exposure to the lowest
  possible dose.
• Radiation injury by either stochastic effects
  (DNA injury) or non-stochastic effects
  (cellular injury) occur at some level to every
  patient.
40y/o Male
PTCA / Stent
Extremely difficult
case, torturous
anatomy
Fluoro Time =
153min.


  6-8 weeks
  Post
  procedure
16-21
weeks
                   Summary
• Time, Distance &      • Mobile Shield
  Shielding             • Table Lead
• Image Intensifier     • Minimize time at
• Table Height            Patients head
• Magnification         • Wear your lead
• Minimize Fluoro and     aprons correctly
  Cine use              • Wear your film
• Use protective eye      badge outside apron
  wear and gloves if      at chest level
  available
Does your facility perform daily quality
     improvement procedures?




Fluoroscopic test tool developed for SCAI in 2000 (www.scai.org)
                     References

• Cardiac Catheterization Handbook, Kern
• Dave Droll
• Grossman’s Cardiac Catheterization, Angiography and
  Intervention
• SCA&I