In recent years, photon-counting computed tomography (PCD-CT) based on photon-counting detectors (PCDs) has become increasingly utilized in clinical practice. Compared with conventional CT, PCD-CT has the potential to achieve micron-level spatial resolution, lower radiation dose, negligible electronic noise, multi-energy imaging, and material identification, etc. This advancement facilitates the promotion of ultra-low dose scans in clinical scenarios, potentially detecting minimal and hidden lesions, thus significantly improving image quality. However, the current state of the art is limited and issues such as charge sharing, pulse pileup, K-escape and count rate drift remain unresolved. These issues could lead to a decrease in image resolution and energy resolution, while an increasing in image noise and ring artifact and so on. This article systematically reviewed the physical principles of PCD-CT, and outlined the structural differences between PCDs and energy integration detectors (EIDs), and the current challenges in the development of PCD-CT. In addition, the advantages and disadvantages of three detector materials were analysed. Then, the clinical benefits of PCD-CT were presented through the clinical application of PCD-CT in the three diseases with the highest mortality rate in China (cardiovascular disease, tumour and respiratory disease). The overall aim of the article is to comprehensively assist medical professionals in understanding the technological innovations and current technical limitations of PCD-CT, while highlighting the urgent problems that PCD-CT needs to address in the coming years.
近年来，基于光子计数探测器（PCD）的光子计数计算机断层扫描（PCD-CT）已逐步应用于临床实践。相比传统CT，PCD-CT可能会达到微米级空间分辨率、更低的辐射剂量、零电子噪声以及多能量成像和物质识别等，能够促进临床方面超低剂量扫描，并可能发现微小、隐匿性病灶，大幅度提高图像质量。但受限于工艺水平，电荷共享、脉冲堆积、K-电子逃逸和计数率漂移等问题尚未解决，可能会导致图像分辨率和能量分辨率下降，并增加图像噪声和环状伪影等。本文系统阐述了PCD-CT的物理原理、PCD和能量积分探测器（EID）的结构原理差异以及当前PCD-CT发展瓶颈，并分析了三种探测器材料的利弊；然后通过PCD-CT在中国死因占比最高的三种疾病（心血管病、肿瘤、呼吸系统疾病）中的临床应用，具体介绍PCD-CT的临床优势，旨在全面帮助医师理解PCD-CT的技术创新与当前的技术缺陷，并提出未来几年PCD-CT急需解决的问题。.

Photon-counting detectors are a promising new technology for computed tomography (CT) systems. They provide energy-resolved CT data at very high spatial resolution without electronic noise and with improved tissue contrasts. This review article gives an overview of the principles of photon-counting detector CT, of potential clinical benefits and limitations, and of the experience gained so far in pre-clinical installations.