Multi-modal imaging of blood flow

1. A computer-implemented method for measuring at least one of blood flow or volume in a subject, the method comprising:

receiving functional magnetic resonance imaging (fMRI) data that provides information on at least one of volume or oxygenation of blood at one or more locations in a body over a first predetermined length of time;

receiving spectroscopic measurement data representing at least one of blood concentration or oxygenation at a first portion of the body over a second predetermined length of time;

deriving, from the fMRI data corresponding to a second portion of the body, a time varying data set representing changes in at least one of blood oxygenation or volume at a second portion of the body over the first predetermined length of time;

determining a time delay and a value of a similarity metric corresponding to a part of the spectroscopic imaging data that most closely matches the time varying data set, the time delay representing a difference between a first time in which blood flows from a third portion in the body to the first portion and a second time in which blood flows to the second portion from the third portion, and the value of the similarity metric representing an amount of blood at the second portion; and

determining, based on the time delay and the value of the similarity metric, an estimate of a characteristic of at least one of blood flow or blood volume in the second portion at a given time.

2. The method of claim 1 , wherein the fMRI data is acquired from a plurality of fMRI scans performed over the first predetermined time period and at a predetermined frequency.

3. The method of claim 1 , wherein the second predetermined length of time includes, and is longer than, the first predetermined length of time.

4. The method of claim 1 , further comprising filtering, using a digital or analog filter, the time-varying spectroscopic measurement data to reduce noise.

5. The method of claim 1 , wherein determining the time delay further comprises:

dividing the spectroscopic measurement data into a plurality of segments, each segment corresponding to a particular time shift;

identifying a segment from the plurality of segments that matches the time varying data set derived from the fMRI data from the second portion of the body; and

estimating the time delay based on the particular time shift of the identified segment.

6. The method of claim 5 , further comprising cross-correlating each segment of the plurality of segments with the time varying data set derived from the fMRI data from the second portion of the body, wherein a peak cross-correlation amplitude represents the value of the similarity metric.

7. The method of claim 5 , further comprising performing multiple linear model fits using the plurality of segments.

8. The method of claim 5 , wherein a first segment from the plurality of segments partially overlaps a second segment from the plurality of segments.

9. The method of claim 1 , further comprising rendering, on a display, the estimated characteristic.

10. The method of claim 1 , wherein the estimated characteristic is at least one of an amount of blood and speed of blood flow.

11. The method of claim 1 , wherein the first portion of the body at least partially overlaps the second portion of the body.

12. A computer-readable medium storing a computer program for measuring at least one of blood flow or volume, the computer program comprising instructions for causing a computer system to:

receive functional data that provides information on at least one of volume or oxygenation of blood at one or more locations in a body over a first predetermined length of time;

receive near-infrared spectroscopic (NIRS) measurement data representing at least one of blood concentration or oxygenation at a first portion of the body over a second predetermined length of time;

derive, from the functional data corresponding to a second portion of the body, a time varying data set representing changes in at least one of blood oxygenation or volume at a second portion of the body over the first predetermined length of time;

determine a time delay and a value of a similarity metric corresponding to a part of the NIRS measurement data that most closely matches the time varying data set, the time delay representing a difference between a first time in which blood flows from a third portion in the body to the first portion and a second time in which blood flows to the second portion from the third portion, and the value of the similarity metric representing an amount of blood at the second portion; and

determine, based on the time delay and the value of the similarity metric, an estimate of a characteristic of at least one of blood flow or blood volume in the second portion at a given time.

13. The computer readable medium of claim 12 wherein the computer system is further caused to:

divide the NIRS measurement into a plurality of segments, each segment corresponding to a particular time shift;

identify a segment from the plurality of segments that matches the time varying data set derived from the functional data from the second portion of the body; and

estimate the time delay based on the particular time shift of the identified segment.

14. The method of claim 12 , further comprising cross-correlating each segment of the plurality of segments with the time varying data set derived from the functional data from the second portion of the body, wherein a peak cross-correlation amplitude represents the value of the similarity metric.