X-ray computed tomography (CT) is a useful modality to observe tumors. In hospitals, X-rays are measured as electric current with using current-sensitive preamplifiers (PAs). The current-sensitive PA converts electric current induced in a detector by the X-rays into voltage. A dark current, which is a noise of a detector, is also converted to voltage and gives bad influence on the measured voltage signal. For avoiding the effect of the detector noise, many X-rays are necessary for a proper CT measurement.
We developed a low-noise current-sensitive PA called VIEC, with using a charge-sensitive PA without a feedback resistance. This charge-sensitive PA requires an active reset of a feedback capacitance when it is fully charged. With this charge-sensitive PA, the electric current induced by X-rays can be estimated by measuring the time period between two resets.
We reported that the VIEC is 750 times sensitive to electric current than the conventional current-sensitive PA. In this paper, we compare the CT images obtained by the conventional current-sensitive PA and by the VIEC.