Comparison of Hough and Fourier transform approach in the study of kinetics of red blood cell aggregates

Abstract

ABSTRACT The kinetics of three-dimensional red blood cell (RBC) aggregates during sedimentation using an optical method was studied. The blood was taken from healthy donors. Sedimentation of RBCs and glutaraldehyde hardened RBCs in autologous plasma and the sedimentation of RBCs in Dextran at haematocrits 5% was investigated. Light intensity in the image plane of the suspension of the cells was recorded. The movement of the aggregates was visualized by means of a spatiotemporal analysis of the light intensity. With the us e of Hough transform and two-di mensional Fourier transform the velocity of the aggregates was estimated. The velocity depends on the sample height and changes with time. Spatiotemporal distributions of the aggregate velocity were determined. A comparison of velocity distributions obtained with the two methods is presented.Keywords: Hough transform, Fourier transfor m, Red blood cell aggregates, blood sedimentation, aggregate velocity 1. INTRODUCTION The red blood cells (RBCs) suspended in plasma adhere to themselves, forming the rouleaux and next the three-dimensional (3D) RBC aggregates. Due to gravity, the 3D RBC aggregates settle, forming the sediment. The RBC aggregation is affected by plasmatic and cellular factors. Some preclusive themselves hypotheses about the aggregate formation were formed [1,2] however no ne of theirs was refuted. Thus, aggregation and sedimentation processes should be further investigated. In clinical practice the measured sedimentation factor is th e Erythrocyte Sedimentation Rate (ESR). The ESR is widely used as a simple and inexpensive test to assess the acute phase response. However, a dependence of height of the boundary between plasma and fraction containing RBCs on time is investigated in more detailed study of the RBC sedimentation. This dependence is usually shown by the sedimentation curve. From this curve the influence of haematocrit and plasma proteins on bloo d sedimentation were analyzed [3,4]. Various approaches, based on the measurements of laser light forward scattered by blood, where adopted in the study of RBC sedimentation [5-11]. From these studies, different stages of the RBC sedimentation process were distinguished and the time dependence of the position of characteristic boundaries was found. However, th e RBC aggregate kinetics is up to now not well determined. Several methods were developed to measure the velocity. The velocity of settling solid particles is usually measured using particle image velocimetry [12-14]. The blood flow ve locity is measured using the laser-Doppler [15] and Doppler ultrasound method [16]. Recently the velo city of the settling 3D RBC aggregates du ring sedimentation using the method based on the Fourier transform [17] and Hough transform were estimated [18]. In this paper we would like to compare two methods utilized to estimate the velocity of 3D RBC aggregates. First method is based on the two-dimensional Fourier transform wh ile the second method is based on the Hough transform. Using both above methods the velocity of the aggregates as a function of time and container height is estimated. Finally, the results from the two methods are compared.