Li Ke, Liu Xinming, Jacobsen Megan C, Rong John, Jensen Corey T, Tamm Eric P, Dong Frank
Department of Imaging Physics, UT MD Anderson Cancer Center, Houston, Texas, USA.
Department of Interventional Radiology, UT MD Anderson Cancer Center, Houston, Texas, USA.
Med Phys. 2025 Oct;52(10):e70045. doi: 10.1002/mp.70045.
Clinical users have a critical need to routinely assess the performance of photon-counting detectors (PCDs) in PCD-CT scanners. Such assessments provide insights into detector characteristics, support protocol optimization, and inform decisions on future scanner acquisitions. Historically, this has been challenging due to limited access to raw detector data, which restricts direct evaluation of PCD performance.
To evaluate the zero-frequency detective quantum efficiency ( ) and detector deadtime of PCDs from an end-user perspective using reconstructed DICOM images.
Detector performance was evaluated on two Siemens NAEOTOM Alpha PCD-CT scanners and one Siemens SOMATOM Force energy-integrating detector CT (EID-CT) scanner. Air-only scans were performed in service mode across a range of tube potentials (70-140 kV) and tube currents (4-1200 mA). DICOM images were reconstructed on the scanner using a linear algorithm with a soft-tissue kernel (Br44). The noise power spectrum (NPS) of the images was used to estimate the mean detector output counts. Mean input photon numbers were estimated based on beam quality and exposure measurements. For the PCD-CT systems, tube current-sweep experiments were used to generate image variance-mA curves, from which detector deadtime was estimated using a previously validated parametric model.
The EID and PCD demonstrated comparable values (EID: 72%-74%; PCD: 72%-77%). showed no significant dependence on tube potential. The estimated PCD deadtime ranged from 5.3 to 7.0 ns. Detector performance was consistent across both PCD-CT systems. Additionally, the ultra-high-resolution (UHR) and standard acquisition modes exhibited equivalent deadtime.
The of the PCD-CT and EID-CT detectors are comparable, with performance primarily limited by geometric efficiency rather than sensor absorption efficiency. Under clinically relevant conditions, pileup-induced count losses in the evaluated PCD-CT scanners are minimal and appear to be effectively corrected by the manufacturer.
临床用户迫切需要定期评估光子计数探测器（PCD）在PCD-CT扫描仪中的性能。此类评估有助于深入了解探测器特性、支持协议优化，并为未来扫描仪采购决策提供依据。从历史上看，由于获取原始探测器数据的机会有限，这一过程颇具挑战性，因为这限制了对PCD性能的直接评估。
从终端用户的角度，使用重建的DICOM图像评估PCD的零频率探测量子效率（ ）和探测器死时间。
在两台西门子NAEOTOM Alpha PCD-CT扫描仪和一台西门子SOMATOM Force能量积分探测器CT（EID-CT）扫描仪上评估探测器性能。在服务模式下，在一系列管电压（70-140 kV）和管电流（4-1200 mA）范围内进行仅空气扫描。使用具有软组织内核（Br44）的线性算法在扫描仪上重建DICOM图像。图像的噪声功率谱（NPS）用于估计探测器的平均输出计数。基于光束质量和曝光测量估计平均输入光子数。对于PCD-CT系统，使用管电流扫描实验生成图像方差-mA曲线，使用先前验证的参数模型从中估计探测器死时间。
EID和PCD表现出相当的 值（EID：72%-74%；PCD：72%-77%）。 对管电压没有显著依赖性。估计的PCD死时间范围为5.3至7.0 ns。两台PCD-CT系统的探测器性能一致。此外，超高分辨率（UHR）和标准采集模式表现出相同的死时间。
PCD-CT和EID-CT探测器的 相当，性能主要受几何效率而非传感器吸收效率的限制。在临床相关条件下，评估的PCD-CT扫描仪中堆积引起的计数损失最小，并且制造商似乎有效地进行了校正。
