Geometric modeling of the carotid bifurcation in humans: Implications in ultrasonic doppler and radiologic investigations

Abstract

A geometric representation of the carotid bifurcation is presented with data obtained from biplane angiograms of normal branches and branches exhibiting less than 5% vessel diameter reduction. Three features are identified that are of importance in the interpretation of ultrasonic Doppler velocity information and in the design of engineering flow models for evaluation of carotid branch hemodynamics: the variability of the bifurcation angles, the degree of tortuosity, and the nonplanar nature of the branches. In addition, data collected demonstrate the potential usefulness of the common carotid artery as a reference diameter in evaluating stenosis of the carotid bulb.

Variation in the Carotid Bifurcation Geometry of Young Versus Older Adults

“…Unpaired t tests did reveal that our mean diameter and area ratios were significantly higher (PϽ0.0001); however, this may be attributed to the relatively limited axial coverage of our black blood MRI protocol. To demonstrate this, we computed diameter and area ratios from a detailed survey of carotid bifurcation diameters 20 and found that ratios derived from proximal sites roughly corresponding to ours were similarly higher than those derived from distal sites more closely matching those defined for the ECST study This effect of the choice of measurement site may also be seen in the broader comparison of our data with those of the ECST study and postmortem measurements of Goubergrits et al 16,17 presented in Figure 4: our measurements were deliberately made at locations comparable to those used in the latter studies, and it can be seen that their diameter and area ratios are comparable to those of our older group. F tests …”

Three-Dimensional Geometry of the Human Carotid Artery

“…Bifurcation angle in our model is smaller than most previously reported angles. In particular, using centerlines Thomas et al [13] reported the angle of bifurcation of 61.5 deg 6 4.1 deg, Forster et al [6] reported 56 deg 6 13 deg, Bharadvaj et al [31] reported 55 deg, and DeSyo et al [9] reported 40.5 deg 6 17.1 deg. All these studies, with the exception of DeSyo [9], were performed on disease-free arteries.…”

“…However, there is no uniform agreement as to how to choose these directions. Previous studies have used tangents to the arterial centerlines, tangents to the vessel walls, and linear least square fits of centerline points in proximity of the bifurcation [6][7][8][9]12,13,31,32]. Three-dimensional studies have primarily used angles between the directional vectors of the branching arterial axes [23].…”

“…Previous investigators have quantitatively assessed in vivo carotid artery tortuosity from planar images [6,32]. However, actual vessel tortuosity will inevitably be misrepresented by two-dimensional analysis due to projection errors, …”

“…Most existing data on carotid artery geometry [6][7][8][9][10]32] are derived from planar analysis of conventional angiograms, maximum intensity projections from magnetic resonance (MR) angiography and views of vascular casts. All of these methods inevitably incur projection errors or discrepancies introduced by postmortem preparation [11].…”