Method and system for evaluating blood vessel

A system for non-invasively evaluating physiological properties of a section of a blood vessel in a subject, comprising a measuring device and a processing device, wherein:

• the measuring device is configured, non-invasively and without injecting any exogenous agent into the subject, to acquire a first measurement at a first point and a second measurement at a second point, wherein the first point and the second point are along a blood flow direction within the section of the blood vessel, the first measurement comprises a first sequence of images, and the second measurement comprises a second sequence of images, wherein the first sequence of images and the second sequence of images are taken at different time points in one cardiac cycle of the subject, and each of the first sequence of images and the second sequence of images contains at least one of blood velocity information or blood flow information;
• and
• the processing device is configured to generate a first waveform and a second waveform from the first sequence of images and the second sequence of images respectively, and then to calculate a transfer function configured to produce an output waveform given an input waveform, with the first waveform and the second waveform as the input waveform and the output waveform respectively, wherein:
• the transfer function considers a pulsatile nature of the blood flow along the direction thereof, is in a time domain, and is calculated based on an autoregressive moving average (ARMA) model:
• Y
• k
• =
• X
• k
• +
• ∑
• i
• =
• 1
• p
• ⁢
• b
• i
• ⁢
• Y
• k
• -
• i
• +
• ∑
• i
• =
• 1
• q
• ⁢
• a
• i
• ⁢
• X
• k
• -
• i
• ;
• where k is a sample index, Xk are samples of the first measurement, Yk are samples of the second measurement, p is a number of moving average terms, q is a number of autoregressive terms, and ai and bi are coefficients;
• and
• the processing device is further configured to determine the physiological properties of the section of the blood vessel based on the transfer function and parameters p, q, ai, and bi.