Estimation of Blood Flow Velocity in Coronary Arteries Based on the Movement of Radiopaque Agent

INTRODUCTION
Atherosclerosis of coronary arteries (CAs) is the
most common cause of coronary heart disease
(CHD).

 The formation of cholesterol plaques on the
vessel walls forms a narrowing (stenosis) of the CA,
which hinders an adequate blood supply to the myocardium
and inevitably leads to decreased efficiency of
the work of the heart.

The correct assessment of the
location, specific geometry, degree, and hemodynamic
significance of stenosis determines the choice
of tactics for treating patients: surgical (myocardial
revascularization) or non-surgical (using medication)
[1].

The search for adequate criteria for the effective
treatment of coronary heart disease is an urgent task of
modern cardiology [2].


One of the most common methods for characterizing
the morphology of heart arteries is radiopaque
angiography (in other words, coronarography).

 A dose
of a contrast agent that is safe for human health is
brought directly to the mouth of the coronary bed and
is visualized by X-ray examination over several
mechanical cycles of the heart. The results of angiographic
examination (static images and/or video records) enable, first of all, the determination of the
area of CA lesion and in some cases its degree as a ratio
of the vessel diameter before the affected area to the
vessel diameter in the zone of stenosis.


Additional and important information on the significance
of stenosis for myocardial perfusion can be
obtained from the dynamics of blood flow through an
artery.

 Thus, a number of publications [3–8] have
described approaches for estimating coronary blood
flow velocity from video records obtained during the
examination of patients by computed tomography
(CT), magnetic resonance tomography (MRT), or
two-sided coronary angiography. In particular, the
study [8] considers a method for estimation of coronary
blood flow based on the combined processing of
video records made when performing coronary angiography
and CT.

The considered approaches have not become
widely used in clinical practice, primarily due to the
limited prevalence of expensive CT and MRT techniques,
as well as the significant labor and time costs
required for the procedures and processing of the
results.

 The current paper discusses methodological
techniques aimed at increasing the diagnostic value of
the routine angiographic examination of patients,
which is widely used in clinical practice. Algorithms
for digital processing of heart video images are presented, which enable the quantitative characterization
of hemodynamics in the coronary bed by determining
the velocity of spread of the contrast agent front in the
arteries.

The proposed approach technologically includes
several stages and procedures: (1) improving the quality
of video images, (2) determining the geometry of
the CA, (3) recording the boundaries of the contrast
agent, (4) tracking the movement of the boundaries of
the contrast agent, and (5) calculating coronary
blood-flow velocity. It is important to note that the
algorithms presented in the study take account of the
errors caused by the movement of the arteries due to
the mechanical activity of the heart.