  The Multi-voltage Threshold (MVT) method, which samples the signal by certain
reference voltages, has been well developed as being adopted in pre-clinical
and clinical digital positron emission tomography(PET) system. To improve its
energy measurement performance, we propose a Peak Picking MVT(PP-MVT) Digitizer
in this paper. Firstly, a sampled Peak Point(the highest point in pulse
signal), which carries the values of amplitude feature voltage and amplitude
arriving time, is added to traditional MVT with a simple peak sampling circuit.
Secondly, an amplitude deviation statistical analysis, which compares the
energy deviation of various reconstruction models, is used to select adaptive
reconstruction models for signal pulses with different amplitudes. After
processing 30,000 randomly-chosen pulses sampled by the oscilloscope with a
22Na point source, our method achieves an energy resolution of 17.50% within a
450-650 KeV energy window, which is 2.44% better than the result of traditional
MVT with same thresholds; and we get a count number at 15225 in the same energy
window while the result of MVT is at 14678. When the PP-MVT involves less
thresholds than traditional MVT, the advantages of better energy resolution and
larger count number can still be maintained, which shows the robustness and the
flexibility of PP-MVT Digitizer. This improved method indicates that adding
feature peak information could improve the performance on signal sampling and
reconstruction, which canbe proved by the better performance in energy
determination in radiation measurement.

Signal Processing