Method and apparatus for ultrahigh sensitive optical microangiography
Embodiments herein provide an ultrahigh sensitive optical microangiography (OMAG) system that provides high sensitivity to slow flow information, such as that found in blood flow in capillaries, while also providing a relatively low data acquisition time. The system performs a plurality of fast scans (i.e., B-scans) on a fast scan axis, where each fast scan includes a plurality of A-scans. At the same time, the system performs a slow scan (i.e., C-scan), on a slow scan axis, where the slow scan includes the plurality of fast scans. A detector receives the spectral interference signal from the sample to produce a three dimensional (3D) data set. An imaging algorithm is then applied to the 3D data set in the slow scan axis to produce at least one image of the sample. In some embodiments, the imaging algorithm may separate flow information from structural information of the sample.
1. A method of imaging, comprising:
scanning a sample with a probe beam from a light source, the scanning including:
performing a plurality of fast scans (B-scans) on a fast scan axis, each fast scan comprising a plurality of A-scans;
performing one or more slow scans (C-scans), contemporaneously with the fast scans, on a slow scan axis, the slow scan axis being orthogonal to the fast scan axis, and each slow scan comprising a plurality of fast scans;
detecting one or more spectral interference signals from the sample during the scanning to generate a three dimensional (3D) data set, wherein the 3D data set is represented by the complex function I(x i , y j , z k ); and
applying an imaging algorithm to the 3D data set along the slow scan axis to produce at least one image of the sample, wherein the imaging algorithm includes a differential operation of adjacent fast scans along the slow scan axis, the differential operation comprising I′(x i ,y j ,z k )=|I(x i ,y j ,z k )−I(x i ,y j ,z k )| for integer values of j from one to a number, M, of fast scans in a slow scan.
2. The method of claim 1 , wherein the fast scans are driven by a first triangular waveform and the slow scans are driven by a second triangular waveform, the first triangular waveform having a higher frequency than the second triangular waveform.
3. The method of claim 1 , wherein the slow scans are driven by a stepped waveform having a plurality of steps, and a plurality of fast scans are performed at each step of the stepped waveform.
4. The method of claim 1 , wherein the imaging algorithm is configured to operate along the slow scan axis to separate a moving component of the sample from a structural component of the sample.
5. The method of claim 1 , wherein the magnitude portion of the 3D data set is represented by the scalar function A(x i ,y j ,z k ), where I(x i ,y j ,z k )=A(x i ,y j ,z k )exp(iφ), and the differential operation comprises I′(x i ,y j ,z k )=|A(x i ,y j ,z k )−A(x i ,y j-1 ,z k )| for integer values of j from one to a number, M, of fast scans in a slow scan.
6. The method of claim 4 , wherein the imaging algorithm comprises high pass filtering along the slow scan axis in the 3D data set.
7. The method of claim 1 , wherein age of the sample comprises an image of a blood vessel network.
8. The method of claim 1 , wherein the method is applied in vivo.
9. A system for in vivo imaging, comprising:
an optical micro-angiography (OMAG) apparatus; and
one or more processors coupled to the OMAG apparatus and adapted to cause the OMAG apparatus to:
scan a sample with a probe beam from a light source;
perform a plurality of fast scans (B-scans) on a fast scan axis, each fast scan comprising a plurality of A-scans;
perform one or more slow scans (C-scans), contemporaneously with the fast scans, on a slow scan axis, the slow scan axis being orthogonal to the fast scan axis, and each slow scan comprising a plurality of fast scans;
detect one or more spectral interference signals from the sample during the scanning to generate a three dimensional (3D) data set, wherein the 3D data set is represented by the complex function I(x i , y j , z k );and
apply an imaging algorithm to the 3D data set along the slow scan axis to produce an image of the sample, wherein the imaging algorithm includes a differential operation of adjacent fast scans along the slow scan axis, the differential operation comprising I′(x i ,y j ,z k )=|I(x i ,y j ,z k )−I(x i ,y j-1 ,z k )| for integer values off from one to a number, M, of fast scans in a slow scan.
10. The system of claim 9 , wherein the OMAG apparatus includes an x-scanner to perform the plurality of fast scans and a y-scanner to perform the one or more slow scans, and the x-scanner is driven by a fast scan signal, and the y-scanner is driven by a slow scan signal.
11. The system of claim 10 , wherein the fast scan signal comprises a first triangular waveform and slow scan signal comprises a second triangular waveform, the first triangular waveform having a higher frequency than the second triangular waveform.
12. The system of claim 10 , wherein the slow scan signal comprises a stepped waveform having a plurality of steps, and the fast scan signal is configured to cause the x-scanner to perform a plurality of fast scans during each step of the stepped waveform.
13. The system of claim 9 , wherein the imaging algorithm is configured to operate along the slow scan axis to separate a moving component of the sample from a structural component of the sample.
14. The system of claim 9 , wherein the magnitude portion of the 3D data set is represented by the scalar function A(x i ,y j ,z k ), where I(x i ,y j ,z k )=A(x i ,y j ,z k )exp(iφ)and the differential operation comprises I′(x i ,y j ,z k )=|A(x i ,y j ,z k )−A(x i ,y j-1 ,z k )| for integer values of j from one to a number, M, of fast scans in a slow scan.
15. The system of claim 13 , wherein the imaging algorithm comprises high pass filtering along the slow scan axis in the 3D data set.
16. The system of claim 9 , wherein the image of the sample comprises an image of a blood vessel network.
17. The system of claim 9 , wherein the OMAG apparatus is a Fourier domain optical coherence tomography (FD-OCT) apparatus.