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Image Gently, Pause and Pulse: Practice of ALARA in Pediatric Fluoroscopy

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Title: Image Gently, Pause and Pulse: Practice of ALARA in Pediatric Fluoroscopy


1
Image Gently, Pause and Pulse Practice of ALARA
in Pediatric Fluoroscopy
  • Sue C. Kaste, DO1, 2
  • Marta Hernanz-Schulman, MD3
  • Ishtiaq H. Bercha, M.Sc. 4
  • 1 St. Jude Childrens Research Hospital
  • 2 University of Tennessee Health Science Center
  • 3 Monroe Carell Jr. Childrens Hospital at
    Vanderbilt
  • 4 The Childrens Hospital, Aurora, Colorado.

2
ALARA
  • As Low As Reasonably Achievable
  • General principle guiding radiation exposure
  • Keep exposure to radiation dose as low as is
    possible for each procedure, while obtaining
    needed clinical information
  • Image Optimization

3
Primary Learning Objective
  • Review pediatric fluoroscopic procedures
  • understand the source of radiation
  • understand methods to reduce radiation
  • effect on image quality

4
Other Learning Objectives
  • Fluoroscopy radiation units.
  • Scope of pediatric fluoroscopic procedures
  • Methods available for dose reduction
  • clinical settings to apply dose reduction

5
Fluoroscopy Radiation Units
Basic Radiation Quantities
  • Exposure Exposure Rate
  • Air Kerma Air Kerma Rate

6
Fluoroscopy Radiation Units
Radiation Measurement Quantities
  • Incident Air Kerma Rate
  • Entrance Surface Air Kerma Rate

7
Fluoroscopy Radiation Units
Risk Related Quantities
  • Absorbed dose
  • Equivalent Dose
  • Effective dose

8
Basic Radiation Quantities
  • Exposure expresses intensity of x-ray energy
    per unit mass of air.
  • Units Coulomb per kilogram (C/kg).
  • Commonly used units are Roentgen or milli
    Roentgen, expressed as R or mR, respectively.
  • 1 R 2.58 x 10-4 C/kg
  • Exposure rate identifies x-ray intensity per unit
    time. Commonly used units are R/min or mR/min.

9
Basic Radiation Quantities
  • Air Kerma (K) sum of initial kinetic energies
    of all charged particles generated by uncharged
    particles such as x-ray photons released per unit
    mass of air.
  • Unit Joule per kilogram, Commonly referred to
    as Gray/milli Gray (Gy or mGy).
  • 1 Roentgen of exposure ? 8.7 mGy air kerma
  • Air Kerma Rate quantifies air kerma per unit time
    and is written as, dK/dt, that is, incremental
    kerma per unit increment of time.

10
Measurement Quantities
  • Incident Air Kerma (Ka,i) is the air kerma from
    the incident beam along the central x-ray beam
    axis at the skin entrance plane.
  • Only the primary beam is considered and the
    effect of back scattered radiation is excluded.
  • Unit Joule per kilogram, Commonly referred to
    as Gray/milli Gray (Gy or mGy).
  • Incident Air Kerma Rate quantifies air kerma per
    unit time. It is usually measured as mGy/min.

11
Measurement Quantities
  • Entrance Surface Air Kerma (Ka,e)
  • It is the air kerma from the incident beam along
    the central x-ray beam axis at the point where
    radiation enters the patient and the effect of
    back scattered radiation is included.
  • Given as Ka,e Ka,i x B
  • B Back Scatter Factor.
  • Unit Joule per kilogram, Commonly referred to
    as Gray milli Gray (Gy or mGy).
  • Incident Air Kerma Rate quantifies air kerma per
    unit time.

12
Risk Related Quantities
  • Absorbed dose energy deposited per unit mass of
    a material, in our case, within tissue.
  • Initially measured as rads
  • Current unit based on Systeme Internationale (SI
    unit)
  • SI Unit of Absorbed Dose Gray
  • 1Gray (Gy) 100 rad
  • 1rad 10 mGy

13
Risk Related Quantities
  • Dose Equivalent accounts for biological effect
    of type of radiation
  • For example, difference in biological effect
    between
  • ?, ? and ? radiation
  • Radiation Weighting factor (wR) scaling factor
    used
  • ?, Xray wR 1
  • ? (wR) 20
  • SI Unit is Sievert
  • 1 Sievert (Sv) 100 rem
  • 1 rem 10 mSv

14
Risk Related Quantities
  • Effective dose accounts for radio-sensitivity
    of specific organs
  • Includes
  • A tissue weighting factor (wT) for each sensitive
    organ
  • Each tissue included in the clinical examination
    (HT)
  • Effective dose ?wT x HT, (?) summed over all
    exposed organs.
  • SI Unit is Sievert
  • 1 Sievert (Sv) 100 rem
  • 1 rem 10 mSv

15
Background Radiation Exposure
Non-Medical Radiation Source Radiation Dose Estimate Equivalent Amount Background Radiation
Natural background radiation 3 mSv 3mSv/year
Airline passenger (cross-country) 0.04 mSv 4 days
estimate at sea level in US
16
Medical Radiation Exposures
Medical Radiation Source Radiation Dose Estimate Equivalent Amount Background Radiation
Chest x-ray 0.1 mSv 10 days
Urinary tract fluoroscopy (VCUG)
Continuous Mode 0.45 0.59 mSv 2 months
Optimized fluoroscope 0.05 0.07 mSv 1 week
Ward et al Radiology 20082491002
17
Practical Methods to Reduce Radiation Dose to
Fluoroscopy Staff Patients
18
Staff Protection
19
Reduce Radiation Dose Staff
  • Staff dose is due to scattered radiation
  • Scattered radiation is directly proportional to
  • Patient Dose

20
Staff Protection
  • Well fitted lead apron (knees)
  • Leaded glasses (with sides)
  • Thyroid shield
  • Lead gloves

21
Staff protection Hands
  • Keep hands out of the beam
  • Collimate

22
Staff protection Shields
  • Lead shield on tower
  • Do not turn your back to Xray beam if wearing
    front apron only

23
In summary Have we.
  • left our hands in the beam?
  • sacrificed personal safety for expediency?
  • turned our unshielded backs to the X-ray
    source?
  • unnecessarily prolonged exposure?
  • pushed away a protective barrier?

24
Patient Protection
25
Patient Protection
  • Radiation dose is optimized when we use
  • Least amount of radiation
  • That delivers clinically adequate image quality

26
Patient Positioning
  • Proper patient positioning
  • Make use of Inverse square law!
  • Maximize distance between x-ray tube patient
  • Minimize distance between patient Image
    Intensifier

27
Control Fluoroscopic Exposures
  • Choose pulsed fluoroscopy
  • Choose as short a pulse width as possible
  • Typically 5 10 msec pulse width

28
Control Fluoroscopic Exposures
  • Continuous fluoroscopy
  • 30 pulses per second
  • 33 msec pulse width

29
Control Fluoroscopic Exposures
  • Increase filtration to reduce patient radiation
    dose
  • Balanced by need for shorter pulse widths to
    freeze motion
  • Interposition of Aluminum and variable thickness
    of Copper
  • Removes low energy radiation that does not reach
    the image intensifier
  • scattered within the patient
  • adds radiation dose
  • does not contribute to image

30
Control Fluoroscopic Exposures
  • Remove anti-scatter grid whenever possible
  • Removes scattered radiation
  • Increased radiation dose
  • Not necessary in small patients
  • Avoid unnecessary magnification

31
Control Fluoroscopic Exposures
  • Collimate to area of interest
  • No need to radiate tissue that is not clinically
    pertinent

32
Control Fluoroscopic Exposures
  • Use last image hold
  • Whenever you need to inspect the anatomy, and do
    not need to observe motion or changes with time
  • Use Fluoroscopy Store (FS)
  • this method is ideal to convey and record
    motion, such as peristalsis, or show viscus
    distensibility, as in esophagram
  • when you need information without excessive
    detail

Exposure
Fluoro-grab
33
Control Number of Images
  • Choose appropriate, patient-specific technique
  • Limit acquisition to what is essential for
    diagnosis and documentation
  • PAUSE Plan study ahead
  • PAUSE- think frames / second
  • PAUSE think magnification
  • PAUSE think Last Image Hold
  • PAUSE think Image Grab

34
Control Fluoroscopic Use
  • Use fluoroscopic examination when there is a
    clear medical benefit.
  • Use alternative imaging methods whenever possible
  • US
  • MRI

35
Special Pediatric Considerations
  • Pediatric patient management more critical
  • Increased radio-sensitivity, small size,
    longevity.
  • Pediatric size
  • Smaller patient leads to less scattered radiation
  • There is an increased need for magnification

36
Institutional Strategies to Optimize Radiation
Exposure Fluoroscopy
37
To Start
  • An in-house diagnostic medical physicist in
    pediatric hospitals is optimal.
  • The physicist must have proper training and
    background in Medical Physics, such as CAMPEP
    accredited graduate and residency programs.
  • Proper training is key

38
To Start
  • An Image Management committee, comprised of
    radiologists, technologists, administrators and
    medical physicists, under the direction of the
    department Chair, can be very helpful.
  • Responsible for optimizing radiation procedures.
  • Oversee the departmental QA/QC program.
  • Meet criteria for accreditation, e.g. ACR

39
To Start
  • Oversee purchase of capital equipment and
    periodic hardware and software upgrades.
  • Staff training on state of the art technologies.
  • Technologists, radiologists
  • Equipment, safety, physics, radiation biology
  • Compliance with applicable state and federal
    regulations.

40
Dosimetry Records
  • Manage fluoroscopy parameters
  • e.g., pulsed fluoroscopy, pulse rate, removable
    grid
  • Record information related to patient radiation
    dose as displayed by the equipment
  • Cumulative Dose Area Product.
  • Cumulative Air kerma/Skin Dose.

41
Summary
  • PAUSE to properly plan and prepare for study
  • Activate dose saving features of equipment
  • No image exposures unless necessary
  • Download image grab instead
  • PULSE at lowest possible rate

42
References
  • -Gelfand, D.W., D.J. Ott, and Y.M. Chen,
    Decreasing numbers of gastrointestinal studies
    report of data from 69 radiologic practices.
  • AJR Am J Roentgenol, 1987. 148(6) p. 1133-6.
  • -Margulis, A.R., The present status and the
    future of gastrointestinal radiology. Abdom
    Imaging, 1994. 19(4) p. 291-2.
  • -Page, M. and H. Jeffery, The role of
    gastro-oesophageal reflux in the aetiology of
    SIDS. Early Hum Dev, 2000. 59(2) p. 127-49.
  • -Strauss KJ, Kaste SC. The ALARA (as low as
    reasonably achievable) concept in pediatric
    interventional and fluoroscopic imaging
  • striving to keep radiation doses as low as
    possible during fluoroscopy of pediatric
    patientsa white paper executive summary.
  • Radiology 2006 240(3)621-622.
  • -Ward VL, Strauss KJ, Barnewolt CE, Zurakowski D,
    Venkatakrishnan V, Fahey FH, Lebowitz RL, Taylor
    GA. Pediatric radiation
  • exposure reduction and effective dose reduction
    during voiding cystourethrography. Radiology
    2008 2491002-1009.
  • -Hall, E. and J. Amato, Radiobiology for the
    Radiologist. 2005 Williams Wilkins.
  • -Lederman, H.M., et al., Dose reduction
    fluoroscopy in pediatrics. Pediatr Radiol, 2002.
    32(12) p. 844-8.
  • -Ward, V., et al., Radiation exposure reduction
    during voiding cystourethrography in a pediatric
    porcine model of vesicoureteral reflux.
  • Radiology, 2005. 235.
  • -Boland, G.W.L., et al., Dose Reduction in
    Gastrointestinal and Genitourinary Fluoroscopy
    Use of Grid-Controlled Pulsed Fluoroscopy.
  • Am. J. Roentgenol., 2000. 175(5) p. 1453-1457.
  • -Brown, P.H., et al., A multihospital survey of
    radiation exposure and image quality in pediatric
    fluoroscopy. Pediatr Radiol, 2000. 30(4)
  • p. 236-42.
  • -Strauss KJ. Pediatric interventional
    radiography equipment safety considerations.
    Pediatr Radiol (2006) 36 (Suppl 2)126-135.
  • -Hernanz-Schulman M, Emmons M, Price R.
    Radiation dose reduction and image quality
    considerations in pediatric patients.
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