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Purpose: The accuracy of Ir-192 source positions and dwell times has a direct impact on the safe delivery of HDR brachytherapy treatment.Verification of actual dose delivery to the target volume and normal tissue requires information on the actual source movement during the treatment.We studied a dual-pinhole imaging system for independent in vivo monitoring and dose verification of HDR brachytherapy treatment.Methods: The system consists of a plate of terbium-doped gadolinium oxysulfide(Gd2O2S:Tb)scintillator and a CCD camera capable of capturing scintillator emission images at 17 frames per second.A dual-pinhole collimator made of lead plate was used to provide three-dimensional information about the source positions.The dwell time was measured by counting the number of scintillation emission images.A 341.9 GBq Ir-192 source was placed in a water phantom at a depth of 10 cm to simulate clinical conditions.The images of the source were acquired with a source-to-scintillator distance of 20 cm.The source positions and dwell times measured with the imaging system were compared to the predefined positions and times.Results: Images of the source at a series of eight sequential dwell positions separated by a step size of 10 mm with a dwell time of 10 s could be clearly identified and discerned on the scintillator.The differences between the measured and predefined dwell positions and measurements of the dwell time were 1.4±0.2 mm and-0.6±0.3 s,respectively.Conclusions: We demonstrated that a dual-pinhole imaging system can provide clear scintillation images for verification of dwell positions and dwell times of the HDR-source.The imaging system has a potential to track the in vivo Ir-192 source in real time and to be a useful tool for quality assurance in HDR brachytherapy under clinical use.