Radiographic image detector and gain setting method for radiographic image detector

A radiographic image detector for detecting a radiographic image of a subject from radioactive rays having been projected from a radiation source toward the subject and penetrated through the subject, said radiographic image detector comprising:

• a detection panel having pixels arrayed in a two-dimensional matrix in an imaging area exposed to the radioactive rays, each of said pixels accumulating signal charges corresponding to the dosed amount of radioactive rays on each pixel, switching elements turned off to accumulate the signal charges in said pixels or turned on to read out the signal charges from said pixels, and wiring lines conducting electric currents corresponding to the dosed amounts of radioactive rays on said pixels, each of said wiring lines being respectively connected to a line or a column of said pixels;
• a signal processing circuit including a voltage output circuit and an analog-to-digital converter, said voltage output circuit converting the signal charges read out from said pixels to a voltage signal while amplifying the voltage signal, said analog-to-digital converter converting the voltage signal to digital data at an output of said voltage output circuit;
• a dose profile measuring device for measuring a dose profile representative of at least linear distribution of the dosed amounts of radioactive rays within the imaging area, said dose profile measuring device measuring the dose profile by the currents flowing through said wiring lines while said switching elements are off and the signal charges are accumulated in said pixels;
• and
• a gain setting device for determining and setting a gain of amplifying the voltage signal in said voltage output circuit depending on contrast in the dose profile.