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 Evaluation Criteria – (Don’s Bosses)  Cost  Durability  Reliability  Range of Application  Accuracy  Ease of Use

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 Devices Types of Devices  Ion Chambers  Solid State Detectors

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 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 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 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 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 Devices Comparison  Ion Chambers vs. Solid State Detectors Do not use any detector outside it’s specified energy range

All the solid state detectors showed under response at low energies

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 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 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 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 Field Data IC 1 versus SS 3 Type IC 1 mR SS 3 mR % diff Dental % Podiatrist % Medical % Mammo %

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 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 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.