Treibel Thomas A, Fontana Marianna, Steeden Jennifer A, Nasis Arthur, Yeung Jason, White Steven K, Sivarajan Sri, Punwani Shonit, Pugliese Francesca, Taylor Stuart A, Moon James C, Bandula Steve
Barts Heart Centre, St Bartholomew's Hospital, London, UK; Institute of Cardiovascular Science, University College London, London, UK.
Barts Heart Centre, St Bartholomew's Hospital, London, UK; Institute of Cardiovascular Science, University College London, London, UK.
J Cardiovasc Comput Tomogr. 2017 May-Jun;11(3):221-226. doi: 10.1016/j.jcct.2017.02.006. Epub 2017 Feb 22.
The quantification of extracellular volume fraction (ECV) by Cardiac Computed Tomography (CCT) can identify changes in the myocardial interstitium due to fibrosis or infiltration. Current methodologies require laboratory blood hematocrit (Hct) measurement - which complicates the technique. The attenuation of blood (HU) is known to change with anemia. We hypothesized that the relationship between Hct and HU could be calibrated to rapidly generate a synthetic ECV without formally measuring Hct.
The association between Hct and HU was derived from forty non-contrast thoracic CT scans using regression analysis. Synthetic Hct was then used to calculate synthetic ECV, and in turn compared with ECV using blood Hct in a validation cohort with mild interstitial expansion due to fibrosis (aortic stenosis, n = 28, ECV = 28 ± 4%) and severe interstitial expansion due to amyloidosis (n = 27; ECV = 54 ± 11%, p < 0.001). For histological validation, synthetic ECV was correlated with collagen volume fraction (CVF) in a separate cohort with aortic stenosis (n = 18). All CT scans were performed at 120 kV and 160 mAs.
HU was a good predictor of Hct (R = 0.47; p < 0.01), with the regression model (Hct = [0.51 * HU] + 17.4) describing the association. Synthetic ECV correlated well with conventional ECV (R = 0.96; p < 0.01) with minimal bias and 2SD difference of 5.7%. Synthetic ECV correlated as well as conventional ECV with histological CVF (both R = 0.50, p < 0.01). Finally, we implemented an automatic ECV plug-in for offline analysis.
Synthetic ECV by CCT provides instantaneous quantification of the myocardial extracellular space without the need for blood sampling.
通过心脏计算机断层扫描（CCT）对细胞外容积分数（ECV）进行定量分析，可识别因纤维化或浸润导致的心肌间质变化。目前的方法需要实验室测量血细胞比容（Hct），这使得该技术变得复杂。已知血液的衰减值（HU）会随着贫血而变化。我们假设，可以校准Hct与HU之间的关系，从而无需正式测量Hct就能快速生成合成ECV。
使用回归分析从40例非增强胸部CT扫描中得出Hct与HU之间的关联。然后使用合成Hct计算合成ECV，并将其与验证队列中因纤维化导致轻度间质扩张（主动脉狭窄，n = 28，ECV = 28 ± 4%）和因淀粉样变性导致严重间质扩张（n = 27；ECV = 54 ± 11%，p < 0.001）的患者使用血液Hct计算出的ECV进行比较。为进行组织学验证，在另一个主动脉狭窄队列（n = 18）中，将合成ECV与胶原容积分数（CVF）进行关联分析。所有CT扫描均在120 kV和160 mAs条件下进行。
HU是Hct的良好预测指标（R = 0.47；p < 0.01），回归模型（Hct = [0.51 * HU] + 17.4）描述了两者之间的关联。合成ECV与传统ECV具有良好的相关性（R = 0.96；p < 0.01），偏差极小，2SD差异为5.7%。合成ECV与传统ECV和组织学CVF的相关性相同（两者R = 0.50，p < 0.01）。最后，我们实现了一个用于离线分析的自动ECV插件。
通过CCT获得的合成ECV可即时定量心肌细胞外间隙，无需进行血液采样。
