|Alessandra Griffa||Master project|
|Politecnico di Torino, Italy||October 2007|
The objective of this work is the study and the characterization of blood perfusion signals during post-occlusion reactive hyperemia tests, acquired by a laser Doppler imaging system. Laser Doppler imaging (LDI) is a non invasive method enabling the monitoring of microvascular blood flow. Even though LDI measurements are non-absolute, the enormous interest in microvascular perfusion has led to many clinical works and a number of studies related to the technique. Specifically, this technique finds applications in diabetology.
We would like to achieve a quantitative description of the signals and assess a set of parameters that result representative of the signals and show a discriminating power between healthy and diabetic subjects. Then our idea is that of characterizing the perfusion signals by a linear model, which particularly should deal with post-occlusive hyperaemic peak variability, in terms of both height and temporal amplitude. We propose a five piecewise regressors linear model, which correlates with an electrical analogue. By the analysis of the available signals and exploiting the designed model, we identify a set of parameters representative of the signals and we propose them has good candidates for healthy and diabetic groups clustering. The model allows us evaluating parameters values with a minor dependency on the noise in the recordings.
Moreover, a short spatial analysis of perfusion maps is performed. We find substantial differences between the nail area and the finger area and we conclude that, with the objective of comparing post-occlusion signals from healthy and diabetic subjects, the investigated area should exclude the nail. Finally, a brief frequency analysis of perfusion signals is performed: the physiological fluctuating components (heartbeat, breathing, vasomotion and neurogenic activities) has been identified.