RESUMO
A video red blood cell velocimeter was implemented with four photometric windows in such a fashion that the upstream and downstream signals are the difference between spatially separated window pairs. The performance of this system was compared with that of a conventional dual window photometric video velocimeter. Tests were made with artificial patterns of red blood cells that simulated long trains of contiguous cells, or large plasma gaps. It was found that the four window system produces a correlogram that is better suited for delay to maximum cross-correlation detection. Similarly, when the responses of the two methods were compared in terms of ability to detect changes of velocity, the time constant for a test step velocity change was found to be 1.2 +/- 0.7 sec for the four window system vs 2.3 +/- 0.6 sec for the two window system. It is concluded that this modification of the capillary red blood cell velocimetry methodology is better suited for detecting the spontaneous flow variations due to vasomotion.
Assuntos
Capilares/fisiologia , Eritrócitos/fisiologia , Velocidade do Fluxo Sanguíneo , Microcirculação , Fotometria , Reologia , Gravação em VídeoRESUMO
An automated technique was developed for the measurement of capillary hematocrit in vivo. The method is based on the photometric detection of the passage of the red blood cells (RBC) through video photometric windows. Red blood cell flux is derived from the primary measurement of opacity and velocity, as opposed to frequency of cell passage and cell transit time. Consequently the technique is less prone to errors caused by the detection of joined cells. Tests in muscle capillaries, compared with hand count frame-by-frame analysis shows that the difference in measured flux is of the order of 16%. Fluctuations due to vasomotion are easily recorded by this approach.
Assuntos
Velocidade do Fluxo Sanguíneo , Eritrócitos/fisiologia , Hematócrito/instrumentação , Animais , Músculos/irrigação sanguínea , Fotometria/instrumentação , Coelhos , ReologiaRESUMO
A video amplifier is described for the purpose of enhancing the contrast of televised scene features. The system operates by amplifying the video signals bracketed by selectable gray levels, in such a fashion that the features of interest take up the whole dynamic range of the video display. The system operates and can be used directly in conjunction with on line video processors such as automated microvessel diameter measuring systems and video blood cell velocimeters.
Assuntos
Amplificadores Eletrônicos , Microscopia/instrumentação , Gravação em Vídeo/instrumentação , Animais , Cricetinae , Microscopia/métodos , Pele/citologia , Gravação em Vídeo/métodosRESUMO
A spatial filter capillary red blood cell velocimeter was implemented in video format by means of a linear array of video photometric windows whose number could be varied from two to eight. Two windows of the same video linear window array were used to measure velocity by means of the conventional cross-correlation method. The two methods, spatial filtering and cross-correlation, were compared by means of a computer-controlled video test pattern generator designed to simulate red blood cell flow of variable hematocrit and velocity. It was found that at normal microvascular hematocrits, both methods provide essentially identical data. At low hematocrit, if the simulated red blood cell distribution is such that a cell is always present within the array, spatial filtering data processing provides a more stable measurement than does cross-correlation; however, under the same conditions spatial filtering yields measurement directly related to flux (red blood cells per unit time) rather than to velocity.
