Image analysis – Applications – Biomedical applications
Reexamination Certificate
1998-02-23
2002-03-26
Au, Amelia M. (Department: 2623)
Image analysis
Applications
Biomedical applications
C382S131000, C382S154000, C382S294000
Reexamination Certificate
active
06363163
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to temporal analysis of medical images and, in particular, to the analysis of computed tomographic images using automated temporal subtraction.
2. Discussion of the Background
The application of a temporal subtraction technique to radiographic images such as chest images can significantly enhance some subtle interval changes existing in sequentially obtained images which might be missed by radiologists. These interval changes may be very important in enabling radiologists to detect some diseases, such as early lung cancer, or to assess the effects of treatment on known lesions. Difazio et al., in Digital chest radiography: Effect of temporal subtraction images on detection accuracy, Radiology, 202:447-452 (1997) reported that the use of the temporal subtraction technique for sequential chest images can significantly increase radiologists' diagnostic accuracy in identifying interval changes.
When radiologists interpret a thoracic computed tomography (CT) scan of a patient, they commonly view it side by side with the most recent previous scan of the same patient. Such comparison readings also help radiologists to identify interval changes or to assess the effects of treatment on known lesions between two consecutive thoracic CT examinations. However, it is difficult and time-consuming for radiologists to compare current and previous (temporally sequential) thoracic CT scans to identify new findings or to assess the effects of treatments on known lesions, because this requires a systematic visual search and correlation of a large number of images (sections) in both current and previous scans. Generally, more than 25 section images were reconstructed from a thoracic CT scan with a section thickness of 10 mm. The number of section images may be much higher when a high-resolution scan (section thickness of 3 mm) is required.
Viewing several images can be difficult because of variations in the images. For example, the positioning of the patient may be different at the various times the images are produced. Patient breathing and cardiac pulsation can also produce variances in the images. It is important to be able to register images to detect interval changes where corresponding features in the images can be subtracted from each other.
The techniques for temporal subtraction, such as described in U.S. Pat. No. 5,319,549, have only been applied to two-dimensional imaging. These techniques register and subtract two-dimensional images, such as chest radiographs.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide improved automated temporal subtraction of images.
A second object of the invention is to enhance interval changes in images.
A further object of the present invention to perform automated temporal subtraction for three-dimensional scanning.
Another object of the present invention is to perform automated temporal subtraction using matching images in the direction of scanning.
A still further objection of the invention is to three-dimensionally match two images and two-dimensionally match corresponding sections of the two images.
These and other objects of the invention are achieved by a method, system and computer program product for detecting interval change in images. In the method according to the invention, first and second three-dimensional images of a subject are obtained. The first and second images are typically current and previous images of a subject. The first and second images are matched. The first image is non-linearly warped to produce a warped image and the warped image is subtracted from the second image. The subtraction can produce and/or enhance interval changes in the first and second images.
A portion of the first image may be selected using an anatomic feature in the first image. A portion of the second image may be selected using the same anatomic feature. Relative areas of the anatomic feature in the first and second images may be determined. The portions of the first and second images may be selected using the relative areas determined in the first and second images, respectively.
Determining the relative areas may be done by threshholding the first and second images to obtain corresponding regions in the first and second images. An area of each of these regions is determined and the relative areas are then determined as a ratio of an area of these regions to remaining areas in the images.
The matching of the images may be done by comparing the first and second relative areas. The matching may also be done by determining a first relationship of the area of the anatomic feature in the first and second images. Averages of the relationships of the areas can then be determined and sections of the first and second images corresponding to the averages can be selected.
It is also possible to select one section in the first image and a number of sections adjacent to that section. These sections are compared to one section selected in the second image. One of the sections selected in the first image is then matched to the section in the second image. Remaining sections in the first image may then be matched in a one-to-one manner to remaining sections and the second image.
Cross-correlation may be used in matching the images. The matching may also consist of initially matching the first image to the second image and then locally matching the first image to the second image. The initial matching may consist of determining whether the first image is rotated and correcting the rotation, and determining vertical and horizontal shifts of the first image relative to the second image. Cross-correlation may use the vertical and horizontal shifts in matching the first and second images.
The local matching may consist of selecting regions of interest in the first and second images and determining horizontal and vertical shifts of regions of interest in the first image relative to regions of interest in the second image. The horizontal and vertical shifts may then be curve-fitted and the used in a warping process to warp the first image. The warped image may be subtracted from the second image to produce a subtracted image.
The method may also include analyzing the registration of the subtracted images. If the registration is inadequate, the image data may be retrieved and the current image may be reconstructed at a different reconstruction starting point. The analysis of the registration may be performed using histogram analysis.
The method may be advantageously applied to computed tomography (CT) scanning. In this case, the three-dimensional matching consists of matching the current and previous scans while the two-dimensional matching consists of matching the corresponding sections of the current and previous CT scans.
The invention may also be implemented in the form of a computer program product comprising a computer storage medium and a computer program code mechanism embedded in the computer storage medium. Code devices are then configured to implement various steps in detecting interval change.
These objects are also achieved by an interval change detecting system having at least one of a three-dimensional image storage device and a three-dimensional image acquisition device. A scanning direction image matching device is connected to one of the acquisition device and storage device. The system may also include a two-dimensional image matching device and a relative area determination circuit. Invention may further include a local matching circuit, a warping circuit and a cross correlation circuit. It is also possible that the system contains a registration analysis circuit which may consist of a histogram analysis circuit, an image data retrieval circuit and an image data reconstruction circuit.
REFERENCES:
patent: 5319549 (1994-06-01), Katsuragawa et al.
patent: 5359513 (1994-10-01), Kano et al.
patent: 5633951 (1997-05-01), Moshfeghi
patent: 5787899 (1998-08-01), Edwards et al.
patent: 5839440 (1998-11-01), Liou et al.
patent: 5881124 (1999-03-01)
Doi Kunio
Xu Xin-Wei
Arch Development Corporation
Au Amelia M.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Wu Jingge
LandOfFree
Method and system for the automated temporal subtraction of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and system for the automated temporal subtraction of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and system for the automated temporal subtraction of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2835806