From the Department of Radiology and Nuclear Medicine, Maastricht University Medical Center, Maastricht, the Netherlands (M.C.M., T.S., L.S., B.M., T.G.F., J.E.W.); Diagnostic and Interventional Radiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland (T.S., H.A.); Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands (M.C.M., T.S., L.S., B.M., J.E.W.); Bayer AG, Berlin, Germany (M.C.M., G.J., H.P.); and Computed Tomography Division, Siemens Healthineers AG, Forchheim, Germany (R.G., B.S., T.G.F.).
Invest Radiol. 2024 Oct 1;59(10):684-690. doi: 10.1097/RLI.0000000000001078. Epub 2024 May 15.
Photon-counting detector computed tomography (PCD-CT) enables spectral data acquisition of CT angiographies allowing for reconstruction of virtual monoenergetic images (VMIs) in routine practice. Specifically, it has potential to reduce the blooming artifacts associated with densely calcified plaques. However, calcium blooming and iodine attenuation are inversely affected by energy level (keV) of the VMIs, creating a challenge for contrast media (CM) injection protocol optimization. A pragmatic and simple rule for calcium-dependent CM injection protocols is investigated and proposed for VMI-based coronary CT angiography with PCD-CT.
A physiological circulation phantom with coronary vessels including calcified lesions (maximum CT value >700 HU) with a 50% diameter stenosis was injected into at iodine delivery rates (IDRs) of 0.3, 0.5, 0.7, 1.0, 1.5, 2.0, 2.5, and 3.0 g I/s. Images were acquired using a first-generation dual-source PCD-CT and reconstructed at various VMI levels (between 45 and 190 keV). Iodine attenuation in the coronaries was measured at each IDR for each keV, and blooming artifacts from the calcified lesions were assessed including stenosis grading error (as % overestimation vs true lumen). The IDR to achieve 300 HU at each VMI level was then calculated and compared with stenosis grading accuracy to establish a general rule for CM injection protocols.
Plaque blooming artifacts and intraluminal iodine attenuation decreased with increasing keV. Fixed windowing (representing absolute worst case) resulted in stenosis overestimation from 77% ± 4% at 45 keV to 5% ± 2% at 190 keV, whereas optimized windowing resulted in overestimation from 29% ± 3% at 45 keV to 4% ± 1% at 190 keV. The required IDR to achieve 300 HU showed a strong linear correlation to VMI energy ( R2 = 0.98). Comparison of this linear plot versus stenosis grading error and blooming artifact demonstrated that multipliers of 1, 2, and 3 times the reference IDR for theoretical clinical regimes of no, moderate, and severe calcification density, respectively, can be proposed as a general rule.
This study provides a proof-of-concept in an anthropomorphic phantom for a simple pragmatic adaptation of CM injection protocols in coronary CT angiography with PCD-CT. The 1-2-3 rule demonstrates the potential for reducing the effects of calcium blooming artifacts on overall image quality.
光子计数探测器 CT（PCD-CT）能够实现 CT 血管造影术的谱数据采集，从而在常规实践中重建虚拟单能量图像（VMIs）。具体来说，它有可能减少与密集钙化斑块相关的blooming 伪影。然而，钙 blooming 和碘衰减会受到 VMIs 能级（keV）的反向影响，这为对比剂（CM）注射方案的优化带来了挑战。本研究旨在为基于 PCD-CT 的冠状动脉 CT 血管造影术提出一种基于钙依赖性 CM 注射方案的实用且简单的规则。
使用包含钙化病变（最大 CT 值>700 HU）的冠状动脉的生理性循环体模进行注射，碘输送率（IDR）分别为 0.3、0.5、0.7、1.0、1.5、2.0、2.5 和 3.0 g I/s。使用第一代双源 PCD-CT 采集图像，并在各种 VMI 水平（45 至 190 keV 之间）进行重建。在每个 IDR 下，测量每个 keV 下冠状动脉中的碘衰减，并评估钙化病变的 blooming 伪影，包括狭窄分级误差（与真腔相比的高估百分比）。然后计算出在每个 VMI 水平下达到 300 HU 的 IDR，并将其与狭窄分级准确性进行比较，以建立 CM 注射方案的一般规则。
随着 keV 的增加，斑块 blooming 伪影和管腔内碘衰减减少。固定窗宽（代表绝对最坏情况）导致狭窄程度高估，从 45 keV 时的 77%±4%增加到 190 keV 时的 5%±2%，而优化窗宽导致 45 keV 时的高估从 29%±3%降至 190 keV 时的 4%±1%。达到 300 HU 的所需 IDR 与 VMI 能量呈强线性相关（R2=0.98）。将该线性图与狭窄分级误差和 blooming 伪影进行比较表明，可以分别提出参考 IDR 的 1、2 和 3 倍作为无、中度和重度钙化密度的理论临床方案的通用规则。
本研究在人体模型中提供了一个概念验证，为 PCD-CT 冠状动脉 CT 血管造影术中 CM 注射方案的简单实用改编提供了依据。1-2-3 规则表明，有可能减少钙 blooming 伪影对整体图像质量的影响。
