| 摘要 |
PURPOSE:To correct the offset generated according to the incident quantity of gamma ray in a circuit for A/D converting the signal from the photomultiplier of a scintillation camera, and provide a stable image which is never changed by the quantity of the incident gamma ray. CONSTITUTION:An A/D converting circuit is formed of an A/D converter 14 for converting the signal outputted from a preamplifier 5 into a digital signal; a latch 16 for holding the lowest value of the output of the A/D converter 14; a comparator 15 for comparing the lowest value held by the latch 16 with the output value of the A/D converter 14 to renew the lowest value held by the latch 16; and a subtracter 17 for subtracting the lowest value from the output value of the A/D converter 14, so that the standard level of the input signal is regularly conformed to the lowest value.
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