Zero-dimensional organic-inorganic metal halides have shown various applications in X-ray detection. However, the mechanism of energy distribution (direct and indirect detection interactions) needs further clarification, and real application reliability (pulsed X-ray and 3D imaging) requires further study. Herein, we designed and synthesized a representative MHs, TBACuI <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (TBA <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> : tetrabutylammonium cation). Experimental and theoretical analyses demonstrate that the energy of luminescent excitons and conducting carriers will not be readily interconverted. Also, the X-ray specific response was achieved, and high sensitivity (>45000 μCGy <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ), low shot noise (1.68×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> nAHz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1/2</sup> ), and superior stability (long time and high energy irradiation or immersion in water) were obtained. Importantly, the device has a high cutoff frequency (>140 Hz) for pulsed X-rays, meeting the needs of medical dynamic imaging (10 Hz). Additionally, the demonstration of 3D reconstruction imaging with direct detectors was achieved.