In this paper, a baseline calibration method for digitally sampling scintillation pulses in positron emission tomography (PET) is investigated. In front-end electronics for PET, power-line fluctuation, dark current, noise disturbances, hum and pulse tail may cause baseline drift, which could lead to the inaccuracy in time, energy and position measurement. We propose a pulse-characterization based baseline calibration restoration algorithm (PCBRA) for digitally sampling scintillation pulses with multi-voltage threshold (MVT) method to correct baseline drift. In this method, a number of threshold-time pairs, digitally sampled from scintillation pulses with preset referenced voltages, are obtained to fit the waveform with a linear curve representing leading edge and an exponential curve representing falling edge, respectively. According to the mathematical model of the falling edge mentioned above, the baseline offset can be obtained and then be subtracted from the waveform to retrieve the pulse without baseline drift. Our preliminary results show that with the application of PCBRA, energy resolution can be obtained accurately, which is close to that obtained with regular-time sampling (RTS) method based baseline calibration.
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