A self-checking fiber optic dosimeter for monitoring common errors in brachytherapy applications

Scintillation dosimetry with optical fiber readout [fiber optic dosimetry (FOD)] requires accurate measurement of light intensity. It is therefore vulnerable to loss of calibration if any changes occur in the efficiency of the optical pathway between the scintillator and the light detector. The authors show in this article that common types of errors that arise during clinical use for brachytherapy applications can be quantified using a light emitting diode to stimulate the scintillator, the so-called LED-FOD method, in an integrated and easy-to-use control unit that incorporates a compact peripheral component interconnect extension for instrumentation. Common sources of error include bending and mechanical compression of the fiber optic components and changes in the temperature of the scintillator. The authors show that the method can detect all the common errors studied in this work and that different types of errors can result in different correlations between the LED stimulated signal and the brachytherapy source signal. For a single-type error the LED-FOD can be used easily for system diagnosis and validation with the possibility to correct the dosimeter reading if the correlation between the LED stimulated signal and the brachytherapy source signal can be defined. For more complex errors, resulting from two or more errors occurring simultaneously, the LED-FOD method can also allow the clinician to make a judgment on the reliability of the dosimeter reading. This self-checking method can enhance the clinical robustness of the FOD for achieving accurate dose control.