Influence of segmented vessel size due to limited imaging resolution on coronary hyperemic flow prediction from arterial crown volume

Abstract

van Horssen P, van Lier MG, van den Wijngaard JP, VanBavel E, Hoefer IE, Spaan JA, Siebes M. Influence of segmented vessel size due to limited imaging resolution on coronary hyperemic flow prediction from arterial crown volume. Am J Physiol Heart Circ Physiol 310: H839 -H846, 2016. First published January 29, 2016 doi:10.1152/ajpheart.00728.2015.-Computational predictions of the functional stenosis severity from coronary imaging data use an allometric scaling law to derive hyperemic blood flow (Q) from coronary arterial volume (V), Q ϭ ␣V ␤ . Reliable estimates of ␣ and ␤ are essential for meaningful flow estimations. We hypothesize that the relation between Q and V depends on imaging resolution. In five canine hearts, fluorescent microspheres were injected into the left anterior descending coronary artery during maximal hyperemia. The coronary arteries of the excised heart were filled with fluorescent cast material, frozen, and processed with an imaging cryomicrotome to yield a three-dimensional representation of the coronary arterial network. The effect of limited image resolution was simulated by assessing scaling law parameters from the virtual arterial network at 11 truncation levels ranging from 50 to 1,000 m segment radius. Mapped microsphere locations were used to derive the corresponding relative Q using a reference truncation level of 200 m. The scaling law factor ␣ did not change with truncation level, despite considerable intersubject variability. In contrast, the scaling law exponent ␤ decreased from 0.79 to 0.55 with increasing truncation radius and was significantly lower for truncation radii above 500 m vs. 50 m (P Ͻ 0.05). Hyperemic Q was underestimated for vessel truncation above the reference level. In conclusion, flow-crown volume relations confirmed overall power law behavior; however, this relation depends on the terminal vessel radius that can be visualized. The scaling law exponent ␤ should therefore be adapted to the resolution of the imaging modality. FRACTIONAL FLOW RESERVE (FFR) has been shown to be a reliable and a widely accepted method to assess whether a coronary artery stenosis is responsible for myocardial ischemia (11). Conceptually, FFR is defined as the hyperemic flow in a vessel with a stenosis relative to the hypothetical hyperemic flow in the undiseased vessel. In practice, FFR is measured invasively as the ratio between pressure distal to a stenosis and aortic pressure, during adenosine-induced hyperemia. This requires passing of a guide wire with a pressure sensor through the stenosis. Despite the reliability of this method, risks of vessel and plaque rupture, procedure time, and costs have inspired the search for new less-invasive alternatives for assessing FFR (18), based on computational methods applied to arterial models obtained from angiography (27) or CT (6). By using experimentally established form-function relationships, coronary flow can be calculated from image-derived morphological data. These relationships are expressed in terms of allometric scaling laws r...

Influence of image segmentation on one-dimensional fluid dynamics predictions in the mouse pulmonary arteries

“…The variability in the total number of vessels for a given segmented network highlights the variation attributed to segmentation. This would be expected in other networks that exhibit dispersive branching patterns, such as the coronary arteries (10) or cerebral vasculature (31). We employed a generation based ordering scheme to describe the branching structure, where each bifurcation is considered a new generation of blood vessels.…”

“…However, inherent uncertainty is present as most image segmentation software require manual specification of the image intensity thresholds (pre-segmentation parameters) between background and foreground. For example, van Horssen et al [10] showed that variation in image resolution affected the cumulative volume of a cast of the coronary arterial tree after segmentation. Rempfler et al [11] compared segmentation algorithms on retinal images, showing that posterior probability estimates for foreground pixels varied with different segmentation techniques when compared with the true segmentation or so-called ground truth.…”

“…Moreover, a recent study [15] of the coronary vasculature showed that 1D models attain similar haemodynamic predictions as 3D when using appropriate boundary conditions. Recent studies analysed 1D systemic arterial models [10,16] to understand how uncertainty in network structure impacts haemodynamics. Fossan et al [17] devised an optimization strategy to determine the number of vessels needed to match haemodynamic predictions in the coronary arteries, and Huberts et al [13] used polynomial chaos expansion to quantify the sensitivity of flow predictions to variations in vessel radius.…”

“…Moreover, a recent study (15) of the coronary vasculature showed that 1D models attain similar haemodynamic predictions as 3D when using appropriate boundary conditions. Recent studies have analysed 1D systemic arterial models (10,16) to understand how uncertainty in network structure impacts haemodynamics. Fossan et.…”

“Small Blood Vessels: Big Health Problems?”: Scientific Recommendations of the National Institutes of Health Workshop

“…For example, much remains to be understood regarding the causal relationship between coronary microvascular disease and ischemic heart disease. New methods for high‐resolution ex vivo imaging and morphometry of the entire coronary vasculature in pigs, other large mammals,and mice will help fill these gaps. However, technological advances, such as biosensors for understanding intracellular and macro‐scale signaling and mechanics; higher resolution and speed, imaging technologies that can penetrate into deeper layers of tissues in vivo, including intrinsic fluorescence; fate mapping for disease etiology, eg, site for angiogenesis; and new transgenic and conditional animal models are needed to further advance the field.…”