Biomedical subjects

Wilbur C K Wong

Publications and source records attributed to Wilbur C K Wong.

4 recordsLinked to original sources

PubMed2006

Does endoluminal coil embolization cause distension of intracranial aneurysms?

INTRODUCTION: The aim of the present study was to determine whether intracranial aneurysms are distended after coil embolization and to evaluate the distensibility of ruptured aneurysms treated with endovascular coiling. METHODS: This was a prospective study of 20 consecutive patients with 22 aneurysms, who presented with a ruptured cerebral aneurysm and were treated with endovascular coiling of the aneurysm in a single institution. A diagnostic digital subtraction angiography (DSA) and a three-dimensional radiographic angiography (3DRA) were performed with bi-plane angiography equipment (Philips V5000) immediately before and after the embolization procedure to detect volume enlargement of the aneurysm after embolization, and the extent of the enlargement. A simulation study with steel spheres was carried out to study the possible error of over-estimation of the postembolization volume due to the beam-hardening artifact. RESULTS: There was no procedure-related rupture of the aneurysms. The percentage by volume of solid coil within the coil mass ranged from 15.78% to 82.01% in the present series. All aneurysms showed distension which ranged from 0.09% to 34.23%. The distensibility of the aneurysms was 34.23%. Error due to the beam-hardening artifact was negligible. CONCLUSION: Endoluminal packing of intracranial saccular aneurysms with embolization coils could cause a certain degree of distension in aneurysms treated with coil embolization, with the degree of distension up to 34.2%. Intracranial aneurysms were able to tolerate a certain degree of endoluminal distension without a risk of immediate rupture, even those that had ruptured recently.

Aneurysm, Ruptured↗

PubMed2006

Augmented vessels for quantitative analysis of vascular abnormalities and endovascular treatment planning.

Endovascular treatment plays an important role in the minimally invasive treatment of patients with vascular diseases, a major cause of morbidity and mortality worldwide. Given a segmentation of an angiography, quantitative analysis of abnormal structures can aid radiologists in choosing appropriate treatments and apparatuses. However, effective quantitation is only attainable if the abnormalities are identified from the vasculature. To achieve this, a novel method is developed, which works on the simpler shape of normal vessels to identify different vascular abnormalities (viz. stenotic atherosclerotic plaque, and saccular and fusiform aneurysmal lumens) in an indirect fashion, instead of directly manipulating the complex-shaped abnormalities. The proposed method has been tested on three synthetic and 17 clinical data sets. Comparisons with two related works are also conducted. Experimental results show that our method can produce satisfactory identification of the abnormalities and approximations of the ideal post-treatment vessel lumens. In addition, it can help increase the repeatability of the measurement of clinical parameters significantly.

Algorithms↗

PubMed2005

Bayesian image segmentation using local iso-intensity structural orientation.

Image segmentation is a fundamental problem in early computer vision. In segmentation of flat shaded, nontextured objects in real-world images, objects are usually assumed to be piecewise homogeneous. This assumption, however, is not always valid with images such as medical images. As a result, any techniques based on this assumption may produce less-than-satisfactory image segmentation. In this work, we relax the piecewise homogeneous assumption. By assuming that the intensity nonuniformity is smooth in the imaged objects, a novel algorithm that exploits the coherence in the intensity profile to segment objects is proposed. The algorithm uses a novel smoothness prior to improve the quality of image segmentation. The formulation of the prior is based on the coherence of the local structural orientation in the image. The segmentation process is performed in a Bayesian framework. Local structural orientation estimation is obtained with an orientation tensor. Comparisons between the conventional Hessian matrix and the orientation tensor have been conducted. The experimental results on the synthetic images and the real-world images have indicated that our novel segmentation algorithm produces better segmentations than both the global thresholding with the maximum likelihood estimation and the algorithm with the multilevel logistic MRF model.

Algorithms↗

PubMed2005

Statistical cerebrovascular segmentation in three-dimensional rotational angiography based on maximum intensity projections.

Segmentation of three-dimensional rotational angiography (3D-RA) can provide quantitative 3D morphological information of vasculature. The expectation maximization-(EM-) based segmentation techniques have been widely used in the medical image processing community, because of the implementation simplicity, and computational efficiency of the approach. In a brain 3D-RA, vascular regions usually occupy a very small proportion (around 1%) inside an entire image volume. This severe imbalance between the intensity distributions of vessels and background can lead to inaccurate statistical modeling in the EM-based segmentation methods, and thus adversely affect the segmentation quality for 3D-RA. In this paper we present a new method for the extraction of vasculature in 3D-RA images. The new method is fully automatic and computationally efficient. As compared with the original 3D-RA volume, there is a larger proportion (around 20%) of vessels in its corresponding maximum intensity projection (MIP) image. The proposed method exploits this property to increase the accuracy of statistical modeling with the EM algorithm. The algorithm takes an iterative approach to compiling the 3D vascular segmentation progressively with the segmentation of MIP images along the three principal axes, and use a winner-takes-all strategy to combine the results obtained along individual axes. Experimental results on 12 3D-RA clinical datasets indicate that the segmentations obtained by the new method exhibit a high degree of agreement to the ground truth segmentations and are comparable to those produced by the manual optimal global thresholding method.

Algorithms↗