Infographics / Digital Radiography

Detective Quantum Efficiency (DQE)

A graph of DQE on the vertical axis against spatial frequency on the horizontal axis. A dashed line at DQE equal to 1 marks the ideal detector, which is never reached in practice. Two curves lie below it and both fall as spatial frequency increases: a higher-DQE detector (for example indirect caesium iodide) sits above a lower-DQE detector (for example direct amorphous selenium). A caption notes that for the same image quality a higher-DQE detector needs a lower dose.

Detective quantum efficiency (DQE) versus spatial frequency A graph of DQE on the vertical axis against spatial frequency on the horizontal axis. A dashed line at DQE equal to 1 marks the ideal detector, which is never reached in practice. Two curves lie below it and both fall as spatial frequency increases: a higher-DQE detector (for example indirect caesium iodide) sits above a lower-DQE detector (for example direct amorphous selenium). A caption notes that for the same image quality a higher-DQE detector needs a lower dose. 1.0 0.5 0 1 2 3 4 ideal detector — DQE = 1 (never reached in practice) higher-DQE detector (e.g. indirect CsI) lower-DQE detector (e.g. direct a-Se) both fall as spatial frequency increases detective quantum efficiency, DQE = SNR² out / SNR² in spatial frequency (lp/mm) for the same image quality a higher-DQE detector needs a lower dose (SNR² ∝ DQE × N) note: direct a-Se has higher spatial resolution (MTF) despite its lower DQE
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