Method and system for imaging
The present invention relates to the field of medical imaging in the absence of contrast agents. In one form, the invention relates to the field of imaging vessels, particularly blood vessels such as the pulmonary vasculature and is suitable for use as a technique for detecting pulmonary embolism (PE), such as acute PE. Embodiments of the present invention provide improved image processing techniques having the capability to extract and use image data to overcome the need for contrast agents to distinguish between different types of tissue. Furthermore, it has also been realised that the image data accessed by the improved image processing can be used to identify irregularities in vessels.
1. A method of scanning for vascular irregularities, the method including:
applying a filter to at least one in vivo image acquired in the absence of contrast agent to provide a probability field and a scale field;
performing vessel segmentation on the probability field to extract a segmented vasculature tree from the probability field;
mapping the scale field to the segmented vasculature tree to quantify a geometry of the vasculature tree; and
performing an automated geometric analysis on the geometry to detect irregularities in the vasculature.
2. The method of claim 1 , wherein the step of performing a vessel segmentation includes performing a region growing operation on the probability field.
3. The method of claim 1 , wherein the step of applying a filter to the in vivo image includes applying a shape filter.
4. The method of claim 3 , wherein the shape used in the shape filter is a tube and the shape filter is a multi-scale shape filter.
5. The method of claim 1 , wherein the step of performing an automated geometric analysis includes comparing a first scale at a first position in the segmented vasculature tree to a second scale at a second position in the segmented vasculature tree.
6. The method of claim 1 , wherein the step of performing an automated geometric analysis includes calculating a change in scale along a length of a branch in the segmented vasculature tree.
7. The method of claim 1 , including performing automated geometric analysis throughout an entire segmented vasculature tree.
8. The method of claim 1 , including acquiring a three-dimensional in vivo image in the absence of contrast agent.
9. The method of claim 8 , including acquiring a three-dimensional in vivo image of the lungs.
10. The method of claim 1 , including scanning for an embolism.
11. The method of claim 1 , including scanning for a vascular irregularity in a lung vasculature.
12. The method of claim 1 , including analysing the geometry to classify segments of the vasculature as normal or irregular.
13. A method of scanning for vascular irregularities in at least one in vivo image acquired in the absence of contrast agent, the method including:
applying a filter to the at least one in vivo image to provide a probability field and a scale field;
performing vessel segmentation on the probability field to extract a segmented vasculature tree from the probability field;
mapping the scale field to the segmented vasculature tree to quantify a geometry of the vasculature tree; and
performing an automated geometric analysis on the geometry to detect irregularities in the vasculature,
wherein the at least one in vivo image comprises a time series of lung images, and further comprising:
measuring a motion of a portion of the lung from the time series of lung images; and
comparing the motion of the portion of the lung to the scale of the vasculature in a region of the portion of the lung to obtain a ventilation/perfusion measure.
14. The method of claim 13 , including measuring an expansion of the portion of the lung.
15. The method of claim 13 , including measuring a motion at multiple points in the portion of the lung and averaging the multiple measurements.
16. The method of claim 13 , including measuring the motion of multiple portions of the lung, and performing the comparison at each of the multiple portions.
17. The method of claim 13 , wherein the portion of the lung is defined by a region distal to a selected point in the segmented vasculature.
18. The method of claim 1 , wherein the applying a filter to at least one in vivo image acquired in the absence of contrast agent to provide a probability field and a scale field comprises:
applying a multi-scale filter to the at least one in vivo image to provide multiple probability fields, one for each of a plurality of scales;
creating an overall probability field from the multiple probability fields by performing a voxel-by-voxel comparison on each of the multiple probability fields and selecting the highest probability for each voxel; and
creating a corresponding overall scale field by recording the scale at which the highest probability occurs for each voxel.
19. The method of claim 18 , wherein applying a multi-scale filter comprises one of inverting the at least one in vivo image, or using a filter that effectively inverts the at least one in vivo image.
20. The method of claim 18 , wherein applying a multi-scale filter comprise two stages, including a first coarse scale and a second fine scale.