A system comprising: a pulsed radiation source ; and a radiation detector (100; 8020), the radiation detector comprising: a plurality of pixels (150; 8022), wherein each pixel is configured to detect radiation emitted from the pulsed radiation source; a device configured to detect an intensity of the radiation from the pulsed radiation source as a function of time, wherein the device is located closer to the pulsed radiation source than the pixels; and a controller ; wherein the pulsed radiation source is configured to emit radiation during a plurality of ON periods and configured not to emit radiation during a plurality of OFF periods ; wherein the controller is configured to determine that the pulsed radiation source is at one of the ON periods or at one of the OFF periods based on the intensity of the radiation detected by the device; wherein the controller is configured to cause the pixels to integrate signals with determination that the radiation source is at one of the ON periods; and wherein the controller is configured to cause the pixels not to integrate signals with determination that the radiation source is at one of the OFF periods. a pulsed radiation source ; and a radiation detector (100; 8020), the radiation detector comprising: a plurality of pixels (150; 8022), wherein each pixel is configured to detect radiation emitted from the pulsed radiation source; a device configured to detect an intensity of the radiation from the pulsed radiation source as a function of time, wherein the device is located closer to the pulsed radiation source than the pixels; and a controller ; wherein the pulsed radiation source is configured to emit radiation during a plurality of ON periods and configured not to emit radiation during a plurality of OFF periods ; wherein the controller is configured to determine that the pulsed radiation source is at one of the ON periods or at one of the OFF periods based on the intensity of the radiation detected by the device; wherein the controller is configured to cause the pixels to integrate signals with determination that the radiation source is at one of the ON periods; and wherein the controller is configured to cause the pixels not to integrate signals with determination that the radiation source is at one of the OFF periods. a plurality of pixels (150; 8022), wherein each pixel is configured to detect radiation emitted from the pulsed radiation source; a device configured to detect an intensity of the radiation from the pulsed radiation source as a function of time, wherein the device is located closer to the pulsed radiation source than the pixels; and a controller ; wherein the pulsed radiation source is configured to emit radiation during a plurality of ON periods and configured not to emit radiation during a plurality of OFF periods ; wherein the controller is configured to determine that the pulsed radiation source is at one of the ON periods or at one of the OFF periods based on the intensity of the radiation detected by the device; wherein the controller is configured to cause the pixels to integrate signals with determination that the radiation source is at one of the ON periods; and wherein the controller is configured to cause the pixels not to integrate signals with determination that the radiation source is at one of the OFF periods. <EOS>