Patent Application
20070297659
The following detailed description of specific embodiments of the present invention can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:
In the following detailed description of the embodiments, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration, and not by way of limitation, specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and that logical, mechanical and electrical changes may be made without departing from the spirit and scope of the present invention.
With CT Lung CAD and CT Colon CAD, segmentation occurs after initial regions of interest are detected, but before features are calculated. The detector finds the regions of interest. After detection, segmentation occurs by taking those regions of interest and refining their boundaries. The segmentation first operates in two dimensions by segmenting the region of interest on each CT slice. As a second step, objects detected on adjacent CT slices are combined to form three-dimensional objects. Accurate segmentations allow for accurate features leading to good classification of suspicious features.
Referring initially to
All of the formed objects are placed into a list in step 210. Then, all of the CT slices in the objects in the list will be examined successively for potential splitting, starting with the first CT slice in the first object in the list. As the objects are split, the newly formed split-off objects will be added to the end of the list.
Splitting automatically occurs when an object has a slice with a single two-dimensional object that overlaps multiple objects on an adjacent CT slice. With this in mind, each object is examined in step 220 to determine if the object starts with a CT slice containing a single object or CT slice containing multiple objects. If the object starts with one or more CT slices with multiple two-dimensional objects on the CT slice, those CT slices are split from the original object and moved to the end of the object list in step 230. Processing of the object resumes in step 240.
In step 240, features and measurements are calculated using the two-dimensional segmentations on adjacent CT slices containing a single object. In this embodiment, only one feature is used. That feature is the measure of the mutual overlap of the two-dimensional segmentations on the adjacent CT slices. These computed features are used by a decision rule of classifier in step 250 to make a determination as to whether each pair of CT slices constitutes parts of the same object. If the two-dimensional segmentations on adjacent CT slices are determined to be parts of different objects, those two-dimensional segmentations are split apart and placed at the end of the object list.
The splitting determination occurs in step 260. For this embodiment, the decision rule may have a simple threshold of about 0.4 on the mutual overlap feature. If the mutual overlap of the two-dimensional segmentations is greater than 0.4, the objects on the adjacent slices are assumed to be from the same object. Again, slices that contain multiple two-dimensional objects are automatically split. When the objects are split in step 270, the split-off object is placed at the end of the object list and the next object is retrieved from the list in step 300.
When the split occurs, or after all of the CT slices of the current object have been examined (steps 280 and 290 loop over all of the CT slices), the analysis moves to the next object in the list (steps 300 and 310). When all objects have been examined, the splitting process is complete. The output, step 320, is a list or labeled mask of three-dimensional segmentations. Therefore, some objects that would have been previously joined incorrectly using simple connectiveness will no longer be considered the same object.
It is noted that terms like “preferably,” “commonly,” and “typically” are not utilized herein to limit the scope of the claimed invention or to imply that certain features are critical, essential, or even important to the structure or function of the claimed invention. Rather, these terms are merely intended to highlight alternative or additional features that may or may not be utilized in a particular embodiment of the present invention.
Having described the invention in detail and by reference to specific embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims. More specifically, although some aspects of the present invention are identified herein as preferred or particularly advantageous, it is contemplated that the present invention is not necessarily limited to these preferred aspects of the invention.
