Department of Pediatrics, Maine Medical Center, 22 Bramhall St, Portland, ME, USA.
J Cardiovasc Magn Reson. 2009 Dec 10;11(1):52. doi: 10.1186/1532-429X-11-52.
Flow mapping by cardiovascular magnetic resonance has become the gold standard for non-invasively defining cardiac output (CO), shunt flow and regurgitation. Previous reports have highlighted the presence of inherent errors in flow mapping that are improved with the use of a stationary phantom control. To our knowledge, these studies have only been performed in healthy volunteers.
We analyzed the variation in flow measurements made with and without stationary phantom correction in 31 patients with congenital heart disease. Variation in stroke volume (SV) measurements was seen in all vessels across all patient groups. The variation was largest when analyzing the right ventricular outflow tract (RVOT), with a range of absolute differences in SV from 0.2 to 70 ml and in CO from 0.02 to 4.8 L/min. In patients with repaired Tetrology of Fallot (ToF), the average ratio of pulmonary to systemic blood flow (Qp:Qs) was 1.18 without and 1.02 with phantom correction. Without performing phantom correction, 23% of the repaired ToF patients were classified as having a residual shunt as compared to 0% when flow mapping was performed with phantom correction. Similarly, in patients with known atrial level shunting (ASD/PAPVR) 20% of patients had no shunt when flow mapping was performed without phantom correction as compared to 0% with phantom correction. In patients with bicuspid aortic valves (BAV), the differences in the regurgitant fraction between measuring flow with and without phantom correction ranged from 0 to 30%, while the regurgitant fraction in the RVOT of ToF patients varied by as much as 31%.
The impact of inherent errors in CMR flow mapping should not be underestimated. While the variation across a population may not display a significant trend, for any individual patient it can be quite large. Failure to correct for such variation can lead to clinically significant misinterpretation of flow data. The use of the stationary phantom correction technique appears to improve accuracy both in normal patients as well as those with congenital heart disease.
心血管磁共振的流量测绘已成为无创性定义心输出量（CO）、分流流量和反流的金标准。以前的报告强调了流量测绘中存在固有误差，而使用固定的幻影校正可以改善这些误差。据我们所知，这些研究仅在健康志愿者中进行过。
我们分析了 31 例先天性心脏病患者在使用和不使用固定幻影校正的情况下进行的流量测量的变化。在所有患者群体中，所有血管的SV 测量值均存在差异。当分析右心室流出道（RVOT）时，SV 的差异最大，SV 的绝对值差异范围为 0.2 至 70ml，CO 的绝对值差异范围为 0.02 至 4.8L/min。在修复性法洛四联症（ToF）患者中，无幻影校正时肺血流量与体循环血流量（Qp:Qs）的平均比值为 1.18，有幻影校正时为 1.02。不进行幻影校正时，23%的修复性 ToF 患者被归类为存在残余分流，而进行幻影校正时则为 0%。同样，在已知存在心房水平分流（ASD/PAPVR）的患者中，20%的患者在不进行幻影校正时没有分流，而在进行幻影校正时则为 0%。在二叶式主动脉瓣（BAV）患者中，用和不用幻影校正测量流量时的反流分数差异范围为 0 至 30%，而 ToF 患者 RVOT 的反流分数差异最大可达 31%。
不应低估 CMR 流量测绘中固有误差的影响。虽然人群中的差异可能没有显示出明显的趋势，但对于任何个体患者，差异可能相当大。如果不纠正这种差异，可能会导致对流量数据的临床意义重大的误解。使用固定的幻影校正技术似乎可以提高正常患者和先天性心脏病患者的准确性。
