The measurement of blood flow from dynamic digital x-ray images using a weighted optical flow algorithm: Validation in a moving-vessel flow phantom (original) (raw)
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Novel approaches to the measurement of arterial blood flow from dynamic digital X-ray images
Medical Imaging, IEEE …, 2005
We have developed two new algorithms for the measurement of blood flow from dynamic X-ray angiographic images. Both algorithms aim to improve on existing techniques. First, a model-based (MB) algorithm is used to constrain the concentration-distance curve matching approach. Second, a weighted optical flow algorithm (OP) is used to improve on point-based optical flow methods by averaging velocity estimates along a vessel with weighting based on the magnitude of the spatial derivative. The OP algorithm was validated using a computer simulation of pulsatile blood flow. Both the OP and the MB algorithms were validated using a physiological blood flow circuit. Dynamic biplane digital X-ray images were acquired following injection of iodine contrast medium into a variety of simulated arterial vessels. The image data were analyzed using our integrated angiographic analysis software SARA to give blood flow waveforms using the MB and OP algorithms. These waveforms were compared to flow measured using an electromagnetic flow meter (EMF). In total 4935 instantaneous measurements of flow were made and compared to the EMF recordings. It was found that the new algorithms showed low measurement bias and narrow limits of agreement and also outperformed the concentration-distance curve matching algorithm (ORG) and a modification of this algorithm (PA) in all studies.
Research and reviews: journal of medical and health sciences, 2017
Detailed blood flow information has been recognized as the key information for diagnosis of vascular diseases, such as vascular stenosis and aneurysms. Optical flow method (OFM) is an emergent technique as a tool to analyze the digital x-ray subtraction angiographic images of blood vessels to obtain the detailed blood flow distribution in vascular systems. A brief review is constructed to discuss the status, applicability, accuracy and future direction of the optical flow technique in the physical study of vascular flow.
Quantification of arterial flow using digital subtraction angiography
Medical Physics, 2012
Purpose: In this paper, a method for the estimation of arterial hemodynamic flow from x-ray video densitometry data is proposed and validated using an in vitro setup. Methods: The method is based on the acquisition of three-dimensional rotational angiography and digital subtraction angiography sequences. A modest contrast injection rate (between 1 and 4 ml/s) leads to a contrast density that is modulated by the cardiac cycle, which can be measured in the x-ray signal. An optical flow based approach is used to estimate the blood flow velocities from the cyclic phases in the x-ray signal. Results: The authors have validated this method in vitro, and present three clinical cases. The in vitro experiments compared the x-ray video densitometry results with the gold standard delivered by a flow meter. Linear correlation analysis and regression fitting showed that the ideal slope of 1 and intercept of 0 were contained within the 95 percentile confidence interval. The results show that a frame rate higher than 50 Hz allows measuring flows in the range of 2 ml/s to 6 ml/s within an accuracy of 5%. Conclusions: The in vitro and clinical results indicate that it is feasible to estimate blood flow in routine interventional procedures. The availability of an x-ray based method for quantitative flow estimation is particularly clinically useful for intra-cranial applications, where other methods, such as ultrasound Doppler, are not available.
Blood flow assessment from optical flow in cineangiography
Computers in Cardiology 1995, 1995
In this paper, we present an optical flow method to infer the bloodflow in arteries by tracking the contrast medium in angiography. In our approach, the velocity field is constrained to be parabolic to take into account this particular property of laminar blood flows. With this method, we get several parameters, both hemodynamic and geometric: the artery radius, the maximum velocity, the blood flow, the centerline position of the artery and other related ones. Tests of the algorithm were conducted on simulated cineangiographic images of straight and stenotic vessels and show errors in the order of 1% for straight vessels up to 10% in short stenosis. Preliminary results with femoral arteries are also very encouraging.
Estimating blood flow velocity in angiographic image data
Medical Imaging 2011: Visualization, Image-Guided Procedures, and Modeling, 2011
We propose a system to estimate blood flow velocity in angiographic image data for patient-specific blood flow simulations. Angiographies are acquired routinely for diagnosis and before treatment of vascular diseases. Projective blood flow is measured in digital subtraction X-ray angiography (2D-DSA) images by tracking contrast agent propagation. Spatial information is added by re-projecting 2D centerline pixels to the reconstructed 3D X-ray rotation angiography (3D-RA) data of the same subject. Ambiguities caused by occluding vessels from the virtual viewpoint of the acquired 2D-DSA image are resolved by a graph-based approach. The blood flow velocity can be used as boundary condition for exact blood flow simulations that can help physicians to understand hemodynamics of the vasculature. Our focus is to analyze cerebral angiographic data. We performed several experiments with phantom and patient data that proved the accuracy and the functionality of our method. We evaluated experimentally the projective flow estimation method and the re-projection method. We measured mean deviations to the ground truth between 11 % and 15.7 % for phantom data. We also showed the ability of our method to produce plausible results with patient-data.
2010
Quantization of red blood cell (RBC) velocity in micro-vessel is one of the techniques for dynamic observation of microvascular mechanisms. The flow measurement of RBC in micro-vessels is still a challenge nowadays. Image processing for velocity measurement using a frame by frame analysis is a common approach. The accuracy of the calculations, which is algorithm dependant, has rarely been examined. In this paper, we evaluated the accuracy of the existing methods, which includes cross correlation method, Hough transform method, and optical flow method, by applying these methods to simulated micro-vessel image sequences. Simulated experiments in various micro-vessels with random RBC motion were applied in the evaluation. The blood flow variation in the same micro-vessels with different RBC densities and velocities was considered in the simulations. The calculation accuracy of different flow patterns and vessel shapes were also examined, respectively. Based on the comparison, the use of an optical flow method, which is superior to a cross-correlation method or a Hough transform method, is proposed for measuring RBC velocity. The study indicated that the optical flow method is suitable for accurately measuring the velocity of the RBCs in small or large micro-vessels.
Model-based blood flow quantification from rotational angiography
Medical Image Analysis, 2008
For assessment of cerebrovascular diseases, it is beneficial to obtain three-dimensional (3D) information on vessel morphology and haemodynamics. Rotational angiography is routinely used to determine the 3D geometry. In this paper, we propose a method to exploit the same acquisition to determine the blood flow waveform and the mean volumetric flow rate in the large cerebral arteries.
Rationale and Objectives. Color velocity imaging-quantitative (CVI-Q) is a new sonographic technique designed to measure volume flow (VF) in blood vessels. We attempted to validate VF measurements with CVI-Q in an in vitro model of the circulation. Methods. We validated CVI-Q in a flow phantom mimicking physiologic conditions by connecting isolated porcine arteries 4-14 mm in diameter to a calibrated perfusion roller pump generating pulsatile flow with porcine blood. Pump flow was varied stepwise from 0 to 1,000 ml/min. CVI-Q VF measurements were performed using a 7.5-MHz linear array transducer. VF results then were compared with pump flow calibration values through linear regression. Results. A good correlation (r 2 = .98-.99, slope = 0.88-1.02) was obtained from 0 to 400-600 ml/min. The degree of correlation depended on vessel diameter, with linearity being maintained over a somewhat larger range in medium-sized vessels. At higher flows, variability increased significantly. Conclusion. VF measurements with CVI-Q are accurate in a physiologic flow range. At supraphysiologic flow rates, as are encountered within arte-riovenous fistulae, CVI-Q may give inaccurate results. Awareness of possible pitfalls and limitations of the technique is important for obtaining accurate and reproducible results.