Giesler M, Grossmann G, Pfob A, Bajtay D, Goller V, Hombach V
Abteilung Kardiologie, Angiologie, Pneumologie und Nephrologie Medizinische Klinik und Poliklinik, Universitat, Ulm.
Z Kardiol. 1996 Jan;85(1):45-52.
The flow convergence method serves to determine flow across orifices (like valve leaks) by color Doppler. Both the PISA method (proximal isovelocity surface areas) and the PVP method (proximal velocity profile) were developed in vitro at circular orifice plates. Therefore, we studied the influence of a non-circular orifice shape on the color map of the flow convergence. Steady flow across orifices of the following shapes was imaged by color Doppler: Oval (6 x 2 mm), slit (12 x 1.5 mm), three-star (diameter 100, area 30 mm2), circular twin-orifice (two circular orifices diameter 2 mm at 10 mm distance from each other) and oval twin-orifice (two ovals 6 x 2 mm at 10 mm distance). As reference we imaged circular orifices with a similar opening area. The alias method was used to locate discrete velocities within the color map, and the proximal velocity profile along the flow center line was analyzed (mean of 24 subsequent images). The local velocity was plotted (y-axis) against its distance to the orifice (x-axis) providing proximal velocity profile curves. The more the orifice shape differed from circular, the more the proximal velocity profile was shifted downward: The profile proximal to the oval was not different from the reference profile proximal to the circular orifice. The profile proximal to the slit was considerably slowed, and proximal to the three-star was even slightly slower (local velocity -12 %, -23 % and -29 % at 14, 8 and 5 mm distance to the orifice). If the circular reference orifice corresponded to total flow across the twin-orifice, the proximal velocity profile of the latter was also shifted markedly downward (-20 %, -18 % and -23 % at 14, 8 and 5 mm distance to the circular twin-orifice). However, if the reference profile corresponded to flow across only one opening of the twin-orifice, the proximal velocity profile of the latter was shifted considerably upwards (+60 %, +71 % and +50 % at 14, 8, and 5 mm distance). Deviation of the orifice shape from circular leads to lower local velocities within the flow convergence; thus neglecting this orifice shape would result in underestimation of flow by the flow convergence method. However, presence of parallel neighboring flow increases the local velocities; neglecting this effect would lead to corresponding overestimation of flow.
血流会聚法用于通过彩色多普勒确定跨孔口的血流情况（如瓣膜反流）。PISA法（近端等速表面积法）和PVP法（近端速度剖面图法）都是在体外圆形孔板上开发的。因此，我们研究了非圆形孔口形状对血流会聚彩色图的影响。通过彩色多普勒对以下形状孔口的稳定血流进行成像：椭圆形（6×2mm）、狭缝形（12×1.5mm）、三星形（直径100，面积30mm²）、圆形双孔口（两个直径2mm的圆形孔口，相距10mm）和椭圆形双孔口（两个6×2mm的椭圆形，相距10mm）。作为对照，我们对具有相似开口面积的圆形孔口进行成像。采用别名法在彩色图中定位离散速度，并分析沿血流中心线的近端速度剖面图（24幅连续图像的平均值）。将局部速度（纵坐标）相对于其到孔口的距离（横坐标）作图，得到近端速度剖面图曲线。孔口形状与圆形差异越大，近端速度剖面图向下偏移越明显：椭圆形孔口近端的剖面图与圆形孔口近端的对照剖面图无差异。狭缝形孔口近端的血流速度明显减慢，三星形孔口近端的血流速度甚至更慢（在距孔口14、8和5mm处，局部速度分别降低-12%、-23%和-29%）。如果圆形对照孔口对应的是双孔口的总血流，那么双孔口近端的速度剖面图也会明显向下偏移（在距圆形双孔口14、8和5mm处分别为-20%、-18%和-23%）。然而，如果对照剖面图对应的是仅通过双孔口一个开口的血流，那么双孔口近端的速度剖面图会明显向上偏移（在14、8和5mm处分别为+60%、+71%和+50%）。孔口形状偏离圆形会导致血流会聚区内局部速度降低；因此，忽略这种孔口形状会导致血流会聚法低估血流。然而，存在平行的相邻血流会增加局部速度；忽略这种影响会导致相应地高估血流。
