To study the effect of heterogeneity in different parts of acute and chronic deep venous thrombus on the ultrasound shear wave elasticity value.

Fifteen Japanese rabbits were used to create an inferior vena cava (IVC) thrombus model via IVC ligation. Young′s modulus of the thrombus head, body and tail were measured using ultrasonic shear wave elasticity technique on the fifth day (acute phase) and 14^th day (chronic phase) of thrombus formation. Pathological sections were obtained from the IVC thrombus in five rabbits at the two points of time mentioned above. Pair t-test and one-way analysis of variance (ANOVA) were used to compare the data between groups.

On the fifth day, Young′s modulus values of the thrombus head, body and tail were (5.73±0.47)kPa, (7.82±0.63)kPa and (4.76±0.45)kPa respectively. ANOVA showed significant difference among three parts (F=134.468, P<0.01). The value of the thrombus body was significantly higher than that of the head and tail (both P<0.01), and the value of the head was significantly higher than that of the tail (P<0.01). On the 14th day, Young′s modulus values of the thrombus head, body and tail were (12.46±2.59)kPa, (15.08±2.71)kPa and (10.03±2.02)kPa, respectively. ANOVA analysis also showed significant difference among three parts (F=10.539, P<0.01). The value of the thrombus body was significantly higher than that of the tail (P<0.01), and also higher than that of the head, although the difference was not significant (P>0.05). There was no significant difference between the head and tail (P>0.05). Young′s modulus values of the thrombus head, body and tail in the chronic phase were significantly higher than those in the acute phase (t=-7.456, -7.989 and -8.159, respectively, all P<0.01). Pathological results showed that there was significant difference in thrombus structure and composition among different parts of the thrombus and among the thrombi in different individuals at corresponding points of time following thrombus formation.

There is significant heterogeneity among different parts of the same thrombus and among different thrombi at corresponding points of time after thrombus formation. Continual monitoring of the thrombus with ultrasound elasticity imaging may help to improve the accuracy of thrombosis staging.