Method for multi-frequency imaging and composite image display using high-bandwidth transducer outputs

1. A method for imaging a patient volume, the method comprising:

directing a first signal at a first frequency into the patient volume;

directing a second signal at a second frequency into the patient volume;

receiving a first response signal associated with the first signal from the patient volume to generate a first image;

receiving a second response signal associated with the second signal from the patient volume to generate a second image;

separating the first image into at least a first section corresponding to a first depth region of the patient volume and a second section corresponding to a second depth region of the patient volume, the first and second sections separated by a first border line;

separating the second image into at least a third section corresponding to the first depth region of the patient volume and a fourth section corresponding to the second depth region of the patient volume, the third and fourth sections separated by a second border line; and

combining the first section of the first image and the fourth section of the second image to form a composite image including only sections of the first image and the second image that do not occupy a same depth in the composite image,

wherein, at the first depth region, the first section of the first image comprises a higher resolution than the third section of the second image, and wherein, at the second depth region, the fourth section of the second image comprises a higher resolution than the second section of the first image.

2. The method of claim 1 wherein the directing the first and second signals into the patient volume comprises selecting the second frequency at a lower frequency than the first frequency, and wherein directing the first signal into the patient volume comprises generating an ultrasound signal at the first frequency; and

directing the second signal into the patient volume comprises generating an ultrasound signal at the second frequency.

3. The method of claim 2 wherein the first section of the first image is associated with a shallow portion of the patient volume, and wherein the fourth section of the second image is associated with a deep portion of the patient volume.

4. The method of claim 2 wherein combining the first section with the fourth section includes filtering out a blood speckle signal from the composite image.

5. The method of claim 1 wherein the first response signal is a harmonic combination of a plurality of frequencies in the first signal.

6. The method of claim 1 wherein the second signal is a harmonic of the first frequency of the first signal.

7. The method of claim 1 wherein the separating the first image into at least the first section and the second section comprises selecting the first section from the first image on a first side of the first border line, and wherein the separating the second image into at least the third section and the fourth section comprises selecting the fourth section from the second image on a second side of the second border line.

8. The method of claim 7 further comprising forming a boundary between the first section of the first image and the fourth section of the second image by selecting points close to the first border line and the second border line.

9. The method of claim 8 wherein forming the boundary comprises interpolating data in the first image and the second image.

10. The method of claim 9 wherein the interpolating data comprises interpolating data across A-scan lines and digitized radio frequency (RF) samples.

11. The method of claim 9 further comprising increasing an interpolation resolution for data close to the boundary.

12. The method of claim 9 wherein the interpolating data comprises interpolating data along a circumference in a cross section of the patient volume.

13. The method of claim 12 wherein the interpolating data comprises interpolating data along a radius of the circumference.

14. The method of claim 7 wherein the first section and the fourth section include high resolution image regions of a lumen and a lumen boundary within the patient volume.

15. The method of claim 14 ,

wherein the first section includes the lumen boundary,

wherein the fourth section includes the lumen, and

wherein the combining includes forming the composite image having the lumen and the lumen boundary.

16. The method of claim 15 , wherein the fourth section includes blood within the lumen.

17. The method of claim 1 wherein separating the first section and second section in the first image and separating the third section and fourth section in the second image comprises obtaining resolution values from the first image and the second image.

18. The method of claim 1 wherein separating the first section and second section in the first image and separating the third section and fourth-section in the second image comprises obtaining brightness and contrast values from the first image and the second image.

19. The method of claim 1 wherein the patient volume includes an interior wall of a blood vessel.

20. The method of claim 1 wherein the patient volume includes a volume behind an outer tissue layer.

21. The method of claim 1 , wherein the composite image comprises a vessel boundary and blood within the vessel boundary.

22. The method of claim 1 , wherein at least the separating and the combining are performed by a patient interface module (PIM) communicatively interposed between a control system and an intravascular device comprising at least one intravascular ultrasound (IVUS) transducer.