Euler André, Zadory Matthias, Breiding Philipe Sebastian, Sartoretti Thomas, Ghafoor Soleen, Froehlich Johannes Malta, Donati Olivio Fabrizio
From the Institute of Diagnostic and Interventional Radiology, University Hospital of Zurich, University of Zurich.
Kluslab Research, Zurich, Switzerland.
Invest Radiol. 2021 Dec 1;56(12):791-798. doi: 10.1097/RLI.0000000000000790.
The aims of this study were to assess if kidney tissue surrogates (KTSs) are superior to distilled water-iodine solutions in the emulation of energy-dependent computed tomography (CT) attenuation characteristics of renal parenchyma and to estimate attenuation thresholds for definite lesion enhancement for low-kV single-energy and low-keV dual-energy virtual monoenergetic imaging.
A water-filled phantom (diameter, 30 cm) with multiple vials was imaged on a dual-source dual-energy CT (DS-DE) and a single-source split-filter dual-energy CT (SF-DE), both in single-energy mode at 80, 100, 120, 140 kVp and in dual-energy mode at 80/Sn150, 90/Sn150, and 100/Sn150 kVp for DS-DE and AuSn120 kVp for SF-DE. Single-energy images, linear-blended dual-energy images, and virtual monoenergetic imaging at energy levels from 40 to 190 keV were reconstructed. First, attenuation characteristics of KTS in solid and liquid consistencies were compared. Second, solid KTSs were developed to match the CT attenuation of unenhanced renal parenchyma at 120 kVp as retrospectively measured in 100 patients. Third, CT attenuation of KTS-iodine and water-iodine solutions at 8 different iodine concentrations (0-10 mg I/mL) were compared as a function of tube voltage and of keV level using multiple linear regression models. Energy-dependent attenuation thresholds for definite lesion enhancement were calculated.
Unenhanced renal parenchyma at 120 kVp measured on average 30 HU on both scanners in the patient cohort. Solid KTS with a water content of 80% emulated the attenuation of unenhanced renal parenchyma (30 HU) more accurately compared with water-iodine solutions (0 HU). Attenuation difference between KTS-iodine and water-iodine solutions converged with increasing iodine concentration and decreasing x-ray energy due to beam-hardening effects. A slight attenuation difference of approximately 2 HU was found between the 2 CT scanners. Attenuation thresholds for definite lesion enhancement were dependent on tube voltage and keV level and ranged from 16.6 to 33.2 HU and 3.2 to 68.3 HU for single-energy and dual-energy CT scan modes for DS-DE and from 16.1 to 34.3 HU and 3.3 to 92.2 HU for SF-DE.
Kidney tissue surrogates more accurately emulate the energy-dependent CT attenuation characteristics of renal parenchyma for multienergy CT compared with conventional water-iodine approaches. Energy-dependent thresholds for definite lesion enhancement could facilitate lesion characterization when imaging at different energies than the traditional 120 kVp.
本研究的目的是评估肾脏组织替代物（KTS）在模拟肾实质的能量依赖性计算机断层扫描（CT）衰减特征方面是否优于蒸馏水碘溶液，并估计低千伏单能量和低keV双能量虚拟单能量成像中明确病变强化的衰减阈值。
在双源双能量CT（DS-DE）和单源分体滤过双能量CT（SF-DE）上对一个装有多个小瓶的直径30 cm的水模进行成像，两种CT均在80、100、120、140 kVp的单能量模式下以及在80/Sn150、90/Sn150和100/Sn150 kVp（DS-DE）以及AuSn120 kVp（SF-DE）的双能量模式下进行。重建单能量图像、线性混合双能量图像以及能量范围从40到190 keV的虚拟单能量成像。首先，比较固体和液体状态下KTS的衰减特征。其次，开发固体KTS以匹配100例患者回顾性测量的120 kVp时未增强肾实质的CT衰减。第三，使用多元线性回归模型比较8种不同碘浓度（0 - 10 mg I/mL）下KTS - 碘溶液和水 - 碘溶液的CT衰减与管电压和keV水平的关系。计算明确病变强化的能量依赖性衰减阈值。
在患者队列中，两台扫描仪上120 kVp时未增强肾实质的平均测量值均为30 HU。与水 - 碘溶液（0 HU）相比，含水量80%的固体KTS更准确地模拟了未增强肾实质的衰减（30 HU）。由于束硬化效应，KTS - 碘溶液和水 - 碘溶液之间的衰减差异随着碘浓度的增加和X射线能量的降低而趋于一致。两台CT扫描仪之间发现约2 HU的轻微衰减差异。明确病变强化的衰减阈值取决于管电压和keV水平，DS - DE的单能量和双能量CT扫描模式下分别为16.6至33.2 HU和3.2至68.3 HU，SF - DE的分别为16.1至34.3 HU和3.3至92.2 HU。
与传统的水 - 碘方法相比，肾脏组织替代物在多能量CT中更准确地模拟了肾实质的能量依赖性CT衰减特征。明确病变强化依赖于能量且具有一定阈值，这有助于在不同于传统120 kVp的能量下成像时对病变进行特征描述。
