Prediction of motion artifacts caused by translation in handheld laser speckle contrast imaging

Abstract

. Significance In handheld laser speckle contrast imaging (LSCI), motion artifacts (MA) are inevitable. Suppression of MA leads to a valid and objective assessment of tissue perfusion in a wide range of medical applications including dermatology and burns. Our study shines light on the sources of these artifacts, which have not yet been explored. We propose a model based on optical Doppler effect to predict speckle contrast drop as an indication of MA. Aim We aim to theoretically model MA when an LSCI system measuring on static scattering media is subject to translational displacements. We validate the model using both simulation and experiments. This is the crucial first step toward creating robustness against MA. Approach Our model calculates optical Doppler shifts in order to predict intensity correlation function and contrast of the time-integrated intensity as functions of applied speed based on illumination and detection wavevectors. To validate the theoretical predictions, computer simulation of the dynamic speckles has been carried out. Then experiments are performed by both high-speed and low-framerate imaging. The employed samples for the experiments are a highly scattering matte surface and a Delrin plate of finite scattering level in which volume scattering occurs. Results An agreement has been found between theoretical prediction, simulation, and experimental results of both intensity correlation functions and speckle contrast. Coefficients in the proposed model have been linked to the physical parameters according to the experimental setups. Conclusions The proposed model provides a quantitative description of the influence of the types of illumination and media in the creation of MA. The accurate prediction of MA caused by translation based on Doppler shifts makes our model suitable to study the influence of rotation. Also the model can be extended for the case of dynamic media, such as live tissue.

Wide dynamic range measurement of blood flow in vivo using laser speckle contrast imaging

“…Irregular motion artifacts from the heart beating and ventilator do significantly affect the measurement accuracy of the myocardial blood flow rate in our LSCI method. Chizari et al 17 proposed a model based on the optical Doppler effect to predict SC drop as an indication of motion artifacts. However, the main focus of our paper is the WDR measurable by LSCI, with the possibility of its application to myocardial perfusion imaging in vivo.…”

“…In addition, a handheld LSCI device was developed, bringing convenience for both patients and clinical staff. [15][16][17][18] However, unlike the arteries in the retina, skin, and cerebral cortex, 19,20 the coronary artery is much larger, and its blood flow is much faster and pulsatile because the heart works as a pump, performing the alternating activities of contraction and relaxation to provide energy for the blood circulation. 21,22 Thus, an LSCI technique that meets the requirements for myocardial perfusion measurements that can measure the blood flow rate over a wide dynamic range (WDR) is a fundamental issue.…”