Patent ID: 7377691

Claim:
A radiographic apparatus for obtaining radiographic images, comprising: radiation emitting means for emitting radiation toward an object under examination; a flat panel X-ray detector as a radiation detection means for detecting the radiation emitted toward the object under examination from said radiation emitting means and transmitted through the object under examination, the flat panel X-ray detector having numerous radiation detecting elements formed of a semiconductor and arranged longitudinally and transversely on a radiation detecting surface; signal sampling means for taking radiation detection signals from the radiation detection means at fixed sampling time intervals; and time lag removing means for determining lag-free radiation detection signals by subtracting a radiation detection signal for a lag-behind part from the respective radiation detection signals by a recursive computation, on an assumption that, of said radiation detection signals taken by said signal sampling means at fixed sampling time intervals, the radiation detection signal for a lag-behind part left unread from said radiation detection means within the fixed sampling time intervals, to be read at a next reading time and added to a radiation detection signal actually read at the next reading time, is due to an impulse response formed of one exponential function or a plurality of exponential functions with different attenuation time constants; wherein said time lac removing means is arranged to perform the recursive computation for removing the lag-behind part from each of the radiation detection signals, based on the following equations A-C: X k =Y k −Σ n=1 n {α n ·[1−exp( T n )]·exp( T n )· S nk } A T n =−Δt/τ n B S nk =X k−1 +exp( T n )· S n(k−1) C where Δt: the sampling time interval; k: a subscript representing a k-th point of time in a sampling time series; Y k : an X-ray detection signal taken at the k-th sampling time; X k : a lag-free X-ray detection signal with a lag-behind part removed from the signal Y k ; X k−1 : a signal X k taken at a preceding point of time; S n(k−1) : an S n at a preceding point of time; exp: an exponential function; N: the number of exponential function with different time constants forming the impulse response; n: a subscript representing one of the exponential functions forming the impulse response; α n : intensity of exponential function n; and τ n : an attenuation time constant of exponential function n; and wherein said radiographic images being derived from said lag-free radiation detection signals obtained by said time lag removing means.