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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 l.jpg

Evaluation of various diagnostic x-ray measuring devices

MDCH Radiation Safety Section

Don Parry, CHP


Evaluation of x ray measuring devices l.jpg
Evaluation of X-ray Measuring Devices

  • Evaluation Criteria – (Don)

    • Accuracy

    • Reliability

    • Range of Application

    • Durability

    • Ease of Use

    • Cost


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Evaluation of X-ray Measuring Devices

  • Evaluation Criteria – (Don’s Bosses)

    • Cost

    • Durability

    • Reliability

    • Range of Application

    • Accuracy

    • Ease of Use


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Evaluation of X-ray Measuring Devices

  • Evaluation Criteria – (Don’s Staff)

    • Ease of Use

    • Reliability

    • Range of Application

    • Durability

    • Accuracy

    • Cost


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Evaluation of X-ray Measuring Devices

  • Types of Devices

    • Ion Chambers

    • Solid State Detectors


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Evaluation of X-ray Measuring Devices

Ion chambers

  • Advantages

    • Flat Energy Response

    • History of Reliability

  • Disadvantages

    • Weight

    • Chambers can be fragile


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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


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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)


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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)


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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)


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Evaluation of X-ray Measuring Devices

  • Comparison

    • Ion Chambers vs. Solid State Detectors

      • Do not use any detector outside it’s specified energy range



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Evaluation of X-ray Measuring Devices energies

  • 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)


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Evaluation of X-ray Measuring Devices energies

  • 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.


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Evaluation of X-ray Measuring Devices energies

  • Ion Chambers – Reliability

    • Ion chamber calibrations have historically been very stable.

    • Ion chambers can be fragile and require appropriate handling by field staff


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Evaluation of X-ray Measuring Devices energies

  • 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


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Evaluation of X-ray Measuring Devices - energiesRange of Applicability

  • Field Data IC 1 versus SS 3


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Evaluation of X-ray Measuring Devices – Ease of Use energies

  • 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


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Evaluation of X-ray Measuring Devices – Our Conclusions energies

  • 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


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Evaluation of X-ray Measuring Devices – Our Conclusions energies

  • 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.


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