1. Using a Newly Developed Live 3D Color Doppler Ultrasound System
ABSTRACT
Background: Accurate noninvasive quantification of stroke volume is clinically important. Laminar flow stroke volume (SV) quantification in the ascending aorta or pulmonary trunk provides a measure of cardiac output. Comparing flows across different valves can also compute shunt and regurgitation fraction. Quantification of 3D color Doppler laminar flow volumes has been studied before using reconstructive color Doppler data, but this was cumbersome to acquire. Our study evaluated newly developed color Doppler mapping with Live 3D (Philips 7500) to test the adequacy of velocity, spatial and temporal resolution for computing SV. Methods: Five rubber tubes (diameter = 3.0, 2.25, 2.0, 1.9, 1.7 cm) were connected to a pulsatile pump and a water tank, 5 different SV (20, 30, 40, 50 or 60 ml/beat) were studied at pump rates of bpm in a phantom model. Nyquist limit was set to cm/sec, frame rate ranged from 13-23/sec. ECG triggered 4D color Doppler data was acquired with a 2-4 MHz probe. Digital scanline data for 3D volume with Doppler velocity assignments was exported and analyzed offline by MatLab custom software. A graduated cylinder and a stopwatch were used for the reference SV data. Results: Close correlations were found between 3D calculated SV and reference data for all tubes (r = 0.94, y = 1.25x , p <0.0001). Conclusions: The Live 3D color Doppler method could provide a new method for clinical evaluation and quantification of flow volumes and could be used for regurgitant fraction calculation.
- 2.98, p < (Figure 4). Also, very good agreement between the 3D SV calculation and reference data was obtained using the Bland-Altman method (Figure 5). Overestimation of the reference data was found especially at higher SVs.
Figure 4. Linear regression between 3D and reference SV.
Figure 5. Bland-Altman agreement.
CONCLUSIONS
The real time live 3D color Doppler method we used provides an efficient and accurate method for quantification of laminar flow volumes. The method could also be used for other flow computation by computing flow through defective valves such as regurgitant fraction calculation by comparing transvalvular flows through normal and defomed valves to each other. Additional studies validating the accuracy of this method by our lab in small animals and in patients have been completed recently.
DISCLOSURES
No relationship to disclose
Xiaokui Li Muhammad Ashraf
Ron Sakaguchi John C Mitchell
Aarti Hejmadi Bhat James Pemberton
Employee of Philips Medical Systems
Karl Thiele
Occasional consultant to Philips Medical Systems
David J Sahn
BACKGROUND
Accurate, noninvasive measurement of blood flow in the inflow and outflow tracts of the heart and great arteries continues to be an important clinical parameter in the assessment of cardiac function, shunt flows in congenital cardiac defects and regurgitation in the presence of valvular disease. Noninvasive methods for the quantification of blood flow include magnetic resonance imaging (MRI), and combinations of M-mode, two-dimensional (2D) echocardiography, and spectral Doppler flow. MRI methods have been used for quantifying flow across semilunar and atrioventricular valves and do not have the inherent angle dependency, window restrictions or attenuation limitations that exist for Doppler ultrasound. However, long acquisition times, lack of portability and mostly the high cost of cardiac MRI deters routine clinical use.
Since Doppler flow imaging is inherently angle dependent and velocity profiles vary both in three-dimensional (3D) space and in time, conventional Doppler spectral methods often do not reliably quantify volume flow. The automated digital color Doppler based automatic cardiac output measurement (ACM) method for measuring cardiac output (Toshiba) is based on flow data obtained parallel to the flow and within a single 2D plane and an assumption of axial or hemi-axial symmetrical flow, which limited its accuracy. We have previously reported reconstructed 3D color Doppler laminar flow methods developed to eliminate the problem that encountered by 2D methods. However, most of the 3D reconstruction methods were time consuming and need complicated offline reconstruction before stroke volume (SV) calculation.
AIMS
The aim of our present study was to evaluate
accuracy and reliability of the new live 3D digital
color technique for measuring laminar flow.
METHODS
Five different rubber tubes (diameter = 3.0, 2.25, 2.0, 1.9, 1.7 cm) were connected to a pulsatile pump with inlet and outlet in same water tank (Figure 1). Five different SVs (20, 30, 40, 50 or 60 ml/beat) were studied at pump rates of bpm in a phantom model. The Nyquist limit was adjusted from 43 to 100 cm/sec according to different depth and frame rate ranged from 13-23/sec.
Figure 1. Flow Phantom
ECG triggered four-dimensional (4D) color Doppler data was acquired with a 2-4 MHz probe. Imaging was performed parallel to the flow direction through a thin (0.5 mm), soft rubber tube segment that connects the thicker tubes to eliminate the shadowing generated by the thick wall. A graduated cylinder and a stopwatch were used for the reference SV data. The 3D volume was obtained immediately after acquisition over 7 triggered cardiac cycle which allowed instant
An In Vitro Study of the Accuracy of Computing Laminar Flow Stroke Volumes
Using a Newly Developed Live 3D Color Doppler Ultrasound System
Xiaokui Li, Muhammad Ashraf, Karl Thiele, Ron Sakaguchi, John C. Mitchell, Aarti Hejimadi Bhat, James Pemberton, David J. Sahn
Oregon Health & Science University, Portland, OR; Philips Ultrasound, Andover, MA
viewing of the tube structure and color flow in any
desired cutting plane (Figure 2). DICOM/scanline data for 3D volume with Doppler velocity assignments was exported and analyzed offline using MatLab custom software, which does not need to be traced frame by frame (Figure 3) as with previous 3D methods.
Figure 2. Color 3D view at different cutting planes.
Figure 3. Matlab custom calculation of laminar flow volume from 3D color Doppler data.
RESULTS
SV results through the tube at different pump settings were analyzed together and correlated with reference data which had excellent correlation between 3D calculated SV and reference data: r = 0.94, y = 1.25x
Thick
Rubber Tube
Thin tube
Pulsatile
Pump
Water Tank
y = 1.25x
r = 0.94
P < 30 60 90 20 40 80
Reference SV (ml/beat)
MatLab Calculated 3D SV
(ml/beat)
-40
-20
Mean of 3D and reference SV (ml/beat)
Difference between 3D and
reference SV (ml/beat)
Mean
+ 2SD
- 2SD