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Evaluation of various diagnostic x-ray measuring devices MDCH Radiation Safety Section Don Parry, CHP Evaluation of X-ray Measuring Devices Evaluation Criteria – (Don) Accuracy Reliability Range of Application Durability Ease of Use Cost Evaluation of X-ray Measuring Devices

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evaluation of various diagnostic x ray measuring devices

Evaluation of various diagnostic x-ray measuring devices

MDCH Radiation Safety Section

Don Parry, CHP

evaluation of x ray measuring devices
Evaluation of X-ray Measuring Devices
  • Evaluation Criteria – (Don)
    • Accuracy
    • Reliability
    • Range of Application
    • Durability
    • Ease of Use
    • Cost
evaluation of x ray measuring devices3
Evaluation of X-ray Measuring Devices
  • Evaluation Criteria – (Don’s Bosses)
    • Cost
    • Durability
    • Reliability
    • Range of Application
    • Accuracy
    • Ease of Use
evaluation of x ray measuring devices4
Evaluation of X-ray Measuring Devices
  • Evaluation Criteria – (Don’s Staff)
    • Ease of Use
    • Reliability
    • Range of Application
    • Durability
    • Accuracy
    • Cost
evaluation of x ray measuring devices5
Evaluation of X-ray Measuring Devices
  • Types of Devices
    • Ion Chambers
    • Solid State Detectors
evaluation of x ray measuring devices6
Evaluation of X-ray Measuring Devices

Ion chambers

  • Advantages
    • Flat Energy Response
    • History of Reliability
  • Disadvantages
    • Weight
    • Chambers can be fragile
evaluation of x ray measuring devices7
Evaluation of X-ray Measuring Devices

Solid State Detectors

  • Advantages
    • Small and lightweight
    • Detectors are more robust
  • Disadvantages
    • More energy dependant
    • Generally not as simple to use
evaluation of x ray measuring devices8
Evaluation of X-ray Measuring Devices
  • Application of X-ray Measuring Devices
    • Dental X-ray (~ 50 – 90 kVp)
    • Medical X-ray (~45 – 150 kVp)
    • Mammography (~24 – 35 kVp)
evaluation of x ray measuring devices accuracy
Evaluation of X-ray Measuring Devices - Accuracy
  • Ion Chambers – Medical and Dental
    • Tested at four x-ray “beam codes”
      • M50 (50 kVp ~1.0 mm Al HVL)
      • L80 (80 kVp ~1.8 mm Al HVL)
      • L-100 (100 kVp ~2.8 mm Al HVL)
      • M-100 (100 kVp ~5.0 mm Al HVL)
      • MoMo 25 (25 kVp, Moly target ~0.30 mm Al HVL)
      • MoMo 30 (30 kVp, Moly target ~0.35 mm Al HVL)
evaluation of x ray measuring devices13
Evaluation of X-ray Measuring Devices

Solid State Detectors – Medical and Dental

  • Tested at three x-ray “beam codes”
    • L80 (80 kVp ~1.8 mm Al HVL)
    • L-100 (100 kVp ~2.8 mm Al HVL)
    • M-100 (100 kVp ~5.0 mm Al HVL)
evaluation of x ray measuring devices18
Evaluation of X-ray Measuring Devices
  • Comparison
    • Ion Chambers vs. Solid State Detectors
      • Do not use any detector outside it’s specified energy range
evaluation of x ray measuring devices21
Evaluation of X-ray Measuring Devices
  • Ion Chambers and Solid State Detectors In Mammography
    • Tested at two “beam codes”
      • MoMo 25 (25 kVp, Moly target ~0.30 mm Al HVL)
      • MoMo 30 (30 kVp, Moly target ~0.35 mm Al HVL)
evaluation of x ray measuring devices27
Evaluation of X-ray Measuring Devices
  • Some Mammography Machines now use beams with higher energies
  • NIST currently does not provide calibration standards for these beams
  • Since the energy response is typically flat for ionization chambers, no additional corrections should be needed.
  • Solid state instruments, however, may require appropriate corrections obtained from the instrument manufacturer.
evaluation of x ray measuring devices28
Evaluation of X-ray Measuring Devices
  • Ion Chambers – Reliability
    • Ion chamber calibrations have historically been very stable.
    • Ion chambers can be fragile and require appropriate handling by field staff
evaluation of x ray measuring devices30
Evaluation of X-ray Measuring Devices
  • Solid State Detectors – Reliability
    • While reliability has been good, radiation response has drifted or failed on some sensors
    • Detectors appear more robust and are less often damaged by misuse
evaluation of x ray measuring devices range of applicability
Evaluation of X-ray Measuring Devices - Range of Applicability
  • Field Data IC 1 versus SS 3
evaluation of x ray measuring devices ease of use
Evaluation of X-ray Measuring Devices – Ease of Use
  • IC1- IC3
    • Care needed in connecting probes
  • SS1
    • Set up difficult when used on some machines
  • SS2
    • Detector cable fixed to base
  • SS3
    • Some felt it was not as simple to use
evaluation of x ray measuring devices our conclusions
Evaluation of X-ray Measuring Devices – Our Conclusions
  • Ion chambers exhibit good energy response over a wide range of beam qualities; new chambers are lighter and smaller
  • SSDs can be designed to have acceptable energy responses in the diagnostic x-ray range, but know your instruments limitations
  • Field staff like the small size and light weight of SSD detectors
evaluation of x ray measuring devices our conclusions35
Evaluation of X-ray Measuring Devices – Our Conclusions
  • Send equipment to an accredited calibration lab annually to ensure radiation response remains in specification
  • We use SSD for equipment with known limits on the energy range
  • We use ion chambers for mammography beams and on x-ray beams in which beam qualities can vary significantly from machine to machine.