Novel approaches to the measurement of arterial blood flow from dynamic digital X-ray images

Abstract

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 out-performed the concentration-distance curve matching algorithm (ORG) and a modification of this algorithm (PA) in all studies.

Changes of Time-Attenuation Curve Blood Flow Parameters in Patients with and without Carotid Stenosis

“…Nevertheless, computer fluid dynamics measures exclusively in vivo flow information in aneurysmal and juxta-aneurysmal areas. 26,27 Its role in stenotic cerebrovascular disease is not clear. The current study results showed that MS and FWHM were only clinically significant in limited ROIs and were complementary to rTmax in describing flows.…”

Analysis of Intra-Aneurysmal Flow for Cerebral Aneurysms with Cerebral Angiography

“…DSA has been used for flow quantification before, and it has been used by others for velocity measurement, [16][17][18] and aneurysmal flow evaluation. [9][10][11] These studies demonstrate that the change of signal does have a potential to assist us in understanding the hemodynamics in arteries and aneurysms.…”

Quantification of Blood Flow from Rotational Angiography

“…Using the velocity of the laminae, the convection of iodine is then determined in 2D representation of the vessel tree, parameterized in terms of length l along and distance r from the vessel centerline [2]. Diffusion is modeled by applying a Gaussian low pass filter.…”

“…Methods based on bolus tracking are known to give unreliable results in the case of pulsatile flow [1,2], and it is not possible to extract a time dependent waveform. Methods based on DICs and on optical flow enable a time-dependent waveform to be extracted.…”

“…Methods based on DICs and on optical flow enable a time-dependent waveform to be extracted. They, however, are sensitive to noise and the flow estimate depends on the distance to the injection site and the time from the start of the injection due to the effects of convective dispersion [2,3]. We propose a model-based flow estimation to overcome these problems by explicitly modeling convective dispersion.…”