Evaluation of various diagnostic x-ray measuring devices

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Evaluation of various diagnostic x-ray measuring
devices

• MDCH Radiation Safety Section
• Don Parry, CHP

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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 (Dons Bosses)
• Cost
• Durability
• Reliability
• Range of Application
• Accuracy
• Ease of Use

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Evaluation of X-ray Measuring Devices

• Evaluation Criteria (Dons 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 its specified
  energy range

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All the solid state detectors showed under
response at low energies
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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)

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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.

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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

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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

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Evaluation of X-ray Measuring Devices - Range of
Applicability

• Field Data IC 1 versus SS 3

Type IC 1 mR SS 3 mR diff
Dental 190.9 197.9 3.7
Podiatrist 7.2 7.3 1.4
Medical 49.8 47.7 -4.2
Mammo 287.2 296.1 3.1
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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

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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

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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.