Pourmorteza Amir, Choux Arnaud Richard, Holmes Thomas Wesley, Schoepf U Joseph, van Assen Marly, De Cecco Carlo, Emrich Tilman, Varga-Szemes Akos
Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA, USA.
Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta, GA, USA.
Eur Radiol Exp. 2025 Mar 19;9(1):31. doi: 10.1186/s41747-024-00530-5.
Beam hardening (BH) artifacts negatively influence computed tomography (CT) measurements, especially when due to dense materials or materials with high effective atomic numbers. Photon-counting detectors (PCD) are more susceptible to BH due to equal weighting of photons regardless of their energies. The problem is further confounded by the use of contrast agents (CAs) with K-edge in the diagnostic CT energy range. We quantified the BH effect of different materials comparing energy-integrating detector (EID)-CT and PCD-CT.
Pairs of test tubes were filled with dense CA (iodine-, gadolinium-, and bismuth-based) and placed inside a water phantom. The phantoms were scanned on EID- and PCD-CT systems, at all available tube voltages for the PCD scanner. Images were reconstructed with standard water BH correction but without any iodine/bone BH corrections. Virtual monoenergetic images (VMI) were calculated from PCD-CT data.
PCD-CT had higher CT numbers in all x-ray spectra for all CAs (p < 0.001) and produced larger cupping artifacts in all test cases (p < 0.001). Bismuth-based CA artifacts were 3- to 5-fold smaller than those of iodine- or gadolinium-based CA. PCD-CT-based VMI completely removed iodine BH artifacts. Iodine BH artifacts decreased with increasing tube voltage. However, gadolinium-based BH artifacts had a different trend increasing at 120 kVp.
EID had fewer BH artifacts compared to PCD at x-ray tube voltages of 120 kVp and higher. The inherent spectral information of PCDs can be used to eliminate BH artifacts. Special care is needed to correct BH artifacts for gadolinium- and bismuth-based CAs.
With the increasing availability of clinical photon-counting CT systems offering the possibility of dual contrast imaging capabilities, addressing and comprehending the BH artifacts attributed to old and novel CT CAs grows in research and ultimately clinical relevance.
EID-CT provides fewer BH artifacts compared to PCD-CT at x-ray tube voltages of 120 kVp and higher. K-edge CAs, such as those based on gadolinium, further confound BH artifacts. The inherent spectral information of photon counting detector CT can be used to effectively eliminate BH artifacts.
线束硬化（BH）伪影会对计算机断层扫描（CT）测量产生负面影响，尤其是当伪影由致密材料或有效原子序数较高的材料引起时。光子计数探测器（PCD）由于对光子能量进行同等加权，因此更容易受到BH的影响。在诊断CT能量范围内使用具有K边的造影剂（CA）会使这个问题更加复杂。我们比较了能量积分探测器（EID）-CT和PCD-CT中不同材料的BH效应。
将成对的试管装满致密的CA（基于碘、钆和铋），并放置在水模体中。在EID-CT系统和PCD-CT系统上对模体进行扫描，扫描电压为PCD扫描仪所有可用的管电压。图像采用标准的水BH校正进行重建，但不进行任何碘/骨BH校正。根据PCD-CT数据计算虚拟单能图像（VMI）。
在所有X射线光谱中，对于所有CA，PCD-CT的CT值均较高（p < 0.001），并且在所有测试案例中均产生了更大的杯状伪影（p < 0.001）。基于铋的CA伪影比基于碘或钆的CA伪影小3至5倍。基于PCD-CT的VMI完全消除了碘BH伪影。碘BH伪影随管电压升高而降低。然而，基于钆的BH伪影在120 kVp时呈现出不同的上升趋势。
在120 kVp及更高的X射线管电压下，与PCD相比，EID的BH伪影更少。PCD的固有光谱信息可用于消除BH伪影。对于基于钆和铋的CA，需要特别注意校正BH伪影。
随着临床光子计数CT系统的日益普及，其具备双对比成像能力，解决和理解归因于新旧CT CA的BH伪影在研究中以及最终在临床中的相关性日益增加。
在120 kVp及更高的X射线管电压下，与PCD-CT相比，EID-CT产生的BH伪影更少。基于钆等的K边CA会进一步加剧BH伪影。光子计数探测器CT的固有光谱信息可用于有效消除BH伪影。
