Evaluation of physical performance of a scintillation dosemeter for patient dosimetry in diagnostic radiology.

The physical performance of the patient scintillation dosemeter Skin Dose Monitor (SDM) was evaluated for use in diagnostic radiology. The SDM response was found to be linear, with output air kerma and output air kerma rate having a reproducibility in time lower than +/- 2.4%) (one standard deviation). A calibration protocol taking into account the more significant parameters, such as radiation quality dependence and the relative sensitivity of SDM detectors of the same batch, can be applied so that the maximum overall uncertainty is +/- 18% at the 95% confidence level. The SDM detectors did not show any loss of sensitivity during the 5-month period of evaluation. SDM performance was evaluated against thermoluminescent dosemeters (TLDs) (GR200A) by monitoring chest X-rays in 18 adult patients. The difference in entrance surface dose (ESD) values between the SDM and TLDs was less than 10%, but a lack of accuracy in ESD values of less than 0.3 mGy was observed. The main benefit of the SDM device compared with TLDs is the real-time read-out of dose combined with a better flexibility and rapidity of use for approximately the same cost per measurement. The SDM device is a good candidate for regular measurement of patient doses in diagnostic imaging departments as required under implementation of the European Council Medical Exposure Directive of 30 June 1997.