A computed tomography (CT) imaging apparatus includes a radiation source configured to emit X-rays； a plurality of photon-counting detectors configured to detect X-rays emitted by the radiation source and generate a photon counting signal based on the detected X-rays； and processing circuitry to obtain a kV-waveform used by the radiation source to generate the X-rays during a scan of an object, and adjust at least one energy threshold dividing the photon counting signal into a plurality of spectra bins in accordance with the obtained kV-waveform.
