A system (100, 200) for monitoring one or more conditions of a subject's body, the system comprising a control unit comprising: an input port configured to receive input data comprising image data corresponding to defocused images in the form of a sequence of speckle patterns generated by a portion of the subject's body in response to coherent illumination during a certain time period, and data indicative of a waveform of at least one external temporally periodic stimulation applied to said portion of the subject's body during said time period of defocused imaging; a memory utility configured to store one or more predetermined models, the model comprising data indicative of a relation between one or more measurable parameters and one or more conditions of the subject's body; and a processor utility configured and operable to process the image data utilizing the data indicative of the waveform of said at least one external temporally periodic stimulation, said processing comprising: determining a spatial correlation function characterized by a correlation peak between successive speckle patterns in the sequence, and determining a time varying spatial correlation function indicative of a change of the speckle pattern over time, the time varying spatial correlation function being determined as a time-varying function of at least one feature of the correlation peak comprising a temporal chart of a change in a position of the correlation peak, and determining a spectrum of said temporal chart, and identifying in said spectrum an amplitude value at a stimulation frequency of said external stimulation; selecting at least one parameter of the time-varying spatial correlation function including said amplitude value at the stimulation frequency of said external stimulation, and applying to said at least one parameter one or more of the models to determine one or more corresponding body conditions; and generating output data indicative of said one or more corresponding body conditions. an input port configured to receive input data comprising image data corresponding to defocused images in the form of a sequence of speckle patterns generated by a portion of the subject's body in response to coherent illumination during a certain time period, and data indicative of a waveform of at least one external temporally periodic stimulation applied to said portion of the subject's body during said time period of defocused imaging; a memory utility configured to store one or more predetermined models, the model comprising data indicative of a relation between one or more measurable parameters and one or more conditions of the subject's body; and a processor utility configured and operable to process the image data utilizing the data indicative of the waveform of said at least one external temporally periodic stimulation, said processing comprising: determining a spatial correlation function characterized by a correlation peak between successive speckle patterns in the sequence, and determining a time varying spatial correlation function indicative of a change of the speckle pattern over time, the time varying spatial correlation function being determined as a time-varying function of at least one feature of the correlation peak comprising a temporal chart of a change in a position of the correlation peak, and determining a spectrum of said temporal chart, and identifying in said spectrum an amplitude value at a stimulation frequency of said external stimulation; selecting at least one parameter of the time-varying spatial correlation function including said amplitude value at the stimulation frequency of said external stimulation, and applying to said at least one parameter one or more of the models to determine one or more corresponding body conditions; and generating output data indicative of said one or more corresponding body conditions. determining a spatial correlation function characterized by a correlation peak between successive speckle patterns in the sequence, and determining a time varying spatial correlation function indicative of a change of the speckle pattern over time, the time varying spatial correlation function being determined as a time-varying function of at least one feature of the correlation peak comprising a temporal chart of a change in a position of the correlation peak, and determining a spectrum of said temporal chart, and identifying in said spectrum an amplitude value at a stimulation frequency of said external stimulation; selecting at least one parameter of the time-varying spatial correlation function including said amplitude value at the stimulation frequency of said external stimulation, and applying to said at least one parameter one or more of the models to determine one or more corresponding body conditions; and generating output data indicative of said one or more corresponding body conditions.