a model for stent graft planning

Abdominal Aortic Aneurysms Abdominal Aortic Aneurysms

Abdominal Abdominal AAortic ortic AAneurysmsneurysms (AAA) (AAA) occur when a occur when a weak section on the wall of aorta expands or weak section on the wall of aorta expands or bulges. The blood pressure in abdominal aorta bulges. The blood pressure in abdominal aorta may cause the weakened part of the aorta to may cause the weakened part of the aorta to bulgebulge like like a a balloon.balloon. If the weakened part is If the weakened part is stretched beyond the safetystretched beyond the safety limits, aorta may limits, aorta may burst or rupture resultingburst or rupture resulting in life-threatening in life-threatening bleedingbleeding. This may lead to shock or even death.. This may lead to shock or even death.

TreatmentTreatment

There are two well-known treatments to cure the There are two well-known treatments to cure the abdominal aortic aneurysms:abdominal aortic aneurysms:

Open (Surgical) Aneurysm RepairOpen (Surgical) Aneurysm Repair Endovascular Aneurysm Repair (EVAR)Endovascular Aneurysm Repair (EVAR)

Nowadays, endovascular aneurysm repair is fairly Nowadays, endovascular aneurysm repair is fairly popular since it is less invasive. This method popular since it is less invasive. This method allows patients to leave hospital sooner and allows patients to leave hospital sooner and recover more quickly. Stent grafts are used recover more quickly. Stent grafts are used during endovascular repair.during endovascular repair.

Stent Graft Selection & RepairStent Graft Selection & Repair

An endovascular stent graft is a deviceAn endovascular stent graft is a device which is which is placed inside the weakened part of the aorta in placed inside the weakened part of the aorta in order to reinforce or strengthen it. The stent order to reinforce or strengthen it. The stent graft is positioned into aorta through long, thin graft is positioned into aorta through long, thin tubes called catheters that are threaded tubes called catheters that are threaded through blood vessels. Expert only makes a through blood vessels. Expert only makes a small incision in groin area to thread the small incision in groin area to thread the catheterscatheters..

An Aortic Aneurysm An Aortic Aneurysm

Stent graft selection is a major difficulty of the Stent graft selection is a major difficulty of the method due to less visual feedback. The stent method due to less visual feedback. The stent must have same dimensions such as length and must have same dimensions such as length and diameter, with the part of aorta where diameter, with the part of aorta where aneurysm occurs. If a small stent is selected, aneurysm occurs. If a small stent is selected, there exists a leakage between stent and aorta there exists a leakage between stent and aorta wall. On the other hand, if it is too large, it will wall. On the other hand, if it is too large, it will be impossible to place the stent. be impossible to place the stent.

Another major difficulty in stent graft repair Another major difficulty in stent graft repair operation is to place the selected stent into operation is to place the selected stent into correct position in aorta. For example, there correct position in aorta. For example, there are two renal vessels that are connected to are two renal vessels that are connected to aorta and aorta and they they supply blood to kidneys. Stent supply blood to kidneys. Stent graft should not block these vessels.graft should not block these vessels.

Stent GraftStent Graft

Medical ImagesMedical Images

To diagnose and treat abdominal aortic aneurysms, CT images are To diagnose and treat abdominal aortic aneurysms, CT images are used. They are stored as DICOM file format. used. They are stored as DICOM file format. DICOMDICOM ( (Digital Imaging Digital Imaging and Communications in Medicineand Communications in Medicine)) is a standard for handling, storing, is a standard for handling, storing, printing, and transmitting information in medical imagingprinting, and transmitting information in medical imaging..

There are different intensity levels in CT images. According to these There are different intensity levels in CT images. According to these differences body organs should be distinguished. To determine the differences body organs should be distinguished. To determine the status of aneurysm nearly 300 CT images are used for a patient. status of aneurysm nearly 300 CT images are used for a patient.

Aorta SegmentationAorta Segmentation

Image segmentation plays a very important role in medical Image segmentation plays a very important role in medical applications by extracting the part of region of interest. There are applications by extracting the part of region of interest. There are different segmentation methods in digital imaging such as different segmentation methods in digital imaging such as thresholding approaches, clustering approaches, and region-growing thresholding approaches, clustering approaches, and region-growing approachesapproaches..

At the moment, we have already implemented aorta segmentation by At the moment, we have already implemented aorta segmentation by using region-growing approach on DICOM data. Region growing is a using region-growing approach on DICOM data. Region growing is a technique for extracting a region of the image that is based on some technique for extracting a region of the image that is based on some predefined criteria. This criteria can be based on intensity predefined criteria. This criteria can be based on intensity information and/or edges in the imageinformation and/or edges in the image..

Aorta segmentation is provided by a Aorta segmentation is provided by a user-interactive feature. User makes user-interactive feature. User makes a single click on the slice where the a single click on the slice where the aorta resides. Aorta data are detected aorta resides. Aorta data are detected in all other slices. in all other slices.

3D Aorta Model & Measurements3D Aorta Model & Measurements

Predication of stent type, size and location are crucial factors for Predication of stent type, size and location are crucial factors for stent graft planning.stent graft planning. Determination of these factors is a time- Determination of these factors is a time-consuming task. Experts should get these values easily in a faster consuming task. Experts should get these values easily in a faster way. We constructed a 3D model of aorta using the data which we way. We constructed a 3D model of aorta using the data which we get from aorta segmentation. Generated model is shown below.get from aorta segmentation. Generated model is shown below.

Future WorkFuture Work

We plan to propose the appropriate stent model according to gathered measurements We plan to propose the appropriate stent model according to gathered measurements using a stent graft database. using a stent graft database. In this database, grafts will be classified according to their In this database, grafts will be classified according to their characteristics.characteristics. Also we plan to model selected stent and apply it to aneurysm virtually. Also we plan to model selected stent and apply it to aneurysm virtually.

The completed model aims to The completed model aims to (1) (1) reduce time-waste in stent selection processreduce time-waste in stent selection process, (2) , (2) propose propose the most appropriate stent for the aneurysmthe most appropriate stent for the aneurysm and (3) see the complications on model and (3) see the complications on model before real surgery.before real surgery.

ReferencesReferences

Pham D. L., Xu C. ,Prince J. L. Current Methods in Medical Image Pham D. L., Xu C. ,Prince J. L. Current Methods in Medical Image Segmentation. Annual Review of Biomedical Engineering, 2000; Segmentation. Annual Review of Biomedical Engineering, 2000; 315-338.315-338.

Haralick R. M., Shapiro L. G. Image segmentation techniques Haralick R. M., Shapiro L. G. Image segmentation techniques Computer Vision, Graphics Image Processing,1985; 29:100-132.Computer Vision, Graphics Image Processing,1985; 29:100-132.

Zhao M., Tian J., Zhu X., Xue J., Cheng Z., Zhao H. The Design and Zhao M., Tian J., Zhu X., Xue J., Cheng Z., Zhao H. The Design and Implementation of a C++ Toolkit for Integrated Medical Image Implementation of a C++ Toolkit for Integrated Medical Image Processing and Analyzing,Procedings.Of SPIE:Medical Processing and Analyzing,Procedings.Of SPIE:Medical Imaging,2004; 5367:39-47Imaging,2004; 5367:39-47

We also implemented user-interactive measurement feature on 3D We also implemented user-interactive measurement feature on 3D aorta model.aorta model. User can click on the model to get the desired values. User can click on the model to get the desired values. Measurements, such as aortic diameter, common iliac diameter, Measurements, such as aortic diameter, common iliac diameter, length from lower renal, plays a key role in during stent selection.length from lower renal, plays a key role in during stent selection.

This tool is capable to do the following steps currently:This tool is capable to do the following steps currently:

Downloading DICOM data from PACSDownloading DICOM data from PACS Loading DICOM FilesLoading DICOM Files User-interactive Aorta SegmenationUser-interactive Aorta Segmenation 3D Reconstruction & Visualization 3D Reconstruction & Visualization User-interactive MeasurementUser-interactive Measurement

There are several tools which segment medical data and visualize There are several tools which segment medical data and visualize them. Our tool combines these features and provides experts them. Our tool combines these features and provides experts faster decision during stent selection process.faster decision during stent selection process.Aorta SegmentationAorta Segmentation

3D Aorta Model3D Aorta Model

CT ImagesCT Images