Dynamically variable filter

A method of analyzing an input radiofrequency signal sensed from an organ of a subject, comprising:

• processing said input radiofrequency signal to provide a processed input signal, wherein said processing comprises determining a phase shift of said input signal relative to an output radiofrequency signal transmitted to the organ;
• filtering said processed signal using a dynamically variable band pass filter adapted in response to a change in a physiological condition of the subject and being characterized by an upper frequency bound which is determined using an iterative process, thereby providing a filtered signal;
• and
• using said filtered signal and said phase shift for calculating at least one of:
• a stroke volume, a cardiac output, a brain intra luminal blood volume and blood flow.

Apparatus for analyzing an input radiofrequency signal sensed from an organ of a subject, comprising:

• an input unit for receiving the input radiofrequency signal;
• a signal processing unit for processing said input radiofrequency signal to provide a processed input signal, said processing unit comprising a phase shift determinator configured for determining a phase shift of said input signal relative to an output radiofrequency signal transmitted to the organ;
• a filtering unit configured for filtering said processed signal using a dynamically variable band pass filter adapted in response to a change in a physiological condition of the subject and being characterized by an upper frequency bound which is determined using an iterative process, to thereby provide a filtered signal;
• and
• a data processor for calculating at least one quantity based on said phase shift, wherein said at least one quantity is selected from the group consisting of a stroke volume, a cardiac output, a brain intra luminal blood volume and blood flow.