Classification of venous thrombosis combining ultrasound elastography and tissue characterization

Deep venous thrombosis (DVT) is the formation of a blood clot in one of the deep veins of the body, usually in the leg. Common treatment methods include medication with anticoagulants or surgical thrombectomy. Since treatment of DVT succeeds only during the first 7-10 days, exact age determination of DVT is of high importance for an appropriate treatment decision. However, the accuracy of available methods including sonography, phlebography, CT and MRT is often not sufficient. It has been reported that about 30% of all DVT are wrongly staged using common diagnostic modalities and therefore lead to inadequate therapeutic efforts. Therefore alternative and more accurate approaches for staging DVT are desired. Blood clots leading to venous thrombosis undergo an organization process with increasing age. It is known that changes in mechanical stiffness, acoustical properties and appearance in B-mode images accompany the organization process. Therefore several alternative diagnostic approaches, including elastography and ultrasonic tissue characterization, have been proposed in the past. In this work, 22 thrombi of defined age were induced in pigs. Ultrasonic measurements were carried out after surgical resection of the thrombosed vessel segments. Spectral and texture parameters as well as strain estimates obtained using elastography were used to classify thrombosed vessel segments in vitro and thus distinguish between thrombi of age ≤ 6 days and age > 6 days. A combination of the best performing parameters was processed by a classification system. Total crossvalidation over specimens was done using Euclidian, Mahalanobis, and maximum-likelihood classifiers. 90% of specimens could be classified correctly using maximum-likelihood classifiers.