Flow quantification in valvular heart disease based on the integral of backscattered acoustic power using Doppler ultrasound

Echokardiographische Flussquantifizierung zur Schweregradbestimmung von Klappeninsuffizienzen

“…Als neue Methode, die sich noch in der Erprobung befindet, erlaubt die PVI-Methode erstmals eine direkte Quantifizierung des Regurgitationsflusses im Klappenleck [8,9]. Die Bezeichnung PVI steht für das "PowerVelocity Integral", welches der Messung zugrunde liegt.…”

Automated flow quantification in valvular heart disease based on backscattered Doppler power analysis: implementation on matrix-array ultrasound imaging systems

“…Backscattered power from non-moving or stagnant blood within the sample volume but outside the flow CSA is eliminated by high-pass filtering and does not contribute to the power in the Doppler spectrum from rapidly moving blood [16]. Because this principle holds only for laminar-like flow and not for turbulent jets, where for a given flow rate, backscattered power is nonlinearly increased by turbulent eddies [20,21] and fluid entrainment into the jet [15], we applied the Doppler power principle at the proximal VC (Fig.…”

“…Standard spectral Doppler display, in fact, is a three-dimensional graph, where the x-axis corresponds to time, the y-axis corresponds to frequency (and also velocity through the Doppler equation), and each pixel intensity value corresponds to the backscattered power at a particular frequency with signal intensity or backscattered power known to be proportional to the area of flow [1]. To overcome this limitation of spectral Doppler analysis, we recently demonstrated a novel approach based on the Doppler Power principle [14] using backscattered acoustic power from the spectral Doppler signal to provide the area information we need [16]: Since backscattered power (P) is linearly proportional to the number of scatterers for a given hematocrit [20,21], backscattered power in the Doppler spectrum of flow through a thin disk-like sample volume of fixed height is linearly proportional to the sonified blood volume of moving scatterers and, therefore, will be linearly proportional to the CSA of flow as long as the area is encompassed by the beam [14,22], or:…”

“…Because this principle holds only for laminar-like flow and not for turbulent jets, where for a given flow rate, backscattered power is nonlinearly increased by turbulent eddies [20,21] and fluid entrainment into the jet [15], we applied the Doppler power principle at the proximal VC (Fig. 1) where flow is laminar prior to entrainment [16,17]. At the VC of a regurgitant jet, identified by a narrow, high-velocity spectrum corresponding to laminar flow (Fig.…”

“…Existing ultrasound techniques based on Doppler methods, however, have been unsatisfactory due to invalid hemodynamic assumptions and indirect estimations, mainly because they cannot measure regurgitant flow directly at the lesion, which requires the product of flow velocity and EROA [8][9][10][11][12][13]. Building upon the basic research done by Hottinger et al [14], we recently showed that since backscattered Doppler power reflects number of scatterers, the integral of Doppler power times velocity (PVI) at the vena contracta (VC) of a regurgitant jet [15] is proportional to volume flow rate [16,17]. That analysis, however, was limited by a beam area which was too narrow as a result of standard phased-array transducer design and the need for time-consuming off-line data analysis and manual tracing of the Doppler spectrum.…”