Measurement of thrombus resolution using three-dimensional ultrasound assessment of deep vein thrombosis volume

Current imaging techniques are limited in their ability to quantify thrombus burden, progression, resolution, and organization over time in patients with acute deep vein thrombosis (DVT). These assessments are critical measures of therapeutic success when thrombolytic or thrombectomy treatment protocols are utilized for DVT. We evaluated the reliability of a new, commercially available method of acquiring and analyzing three-dimensional (3D) ultrasound images of DVTs that measures thrombus volume and echogenicity. We studied 25 consecutive hospital in-patients (18 male, seven female; age range, 37-87 years) with a first episode of acute DVT. Treatment decisions were not influenced by the study protocol. Scanning was performed independently by two sonographers, then the first sonographer repeated the scan. A combination of routine imaging in grayscale, color-flow, and power-Doppler modes (2D transducer) along with volumetric imaging (3D transducer) was performed. Patients underwent imaging at baseline and on one or more follow-up days 7, 14, 21 and 30. Image-processing software loaded on the ultrasound machine was used to obtain thrombus volume and echogenicity measurements. Thrombus volume was reliably determined by our protocol. The median volume of thrombus at baseline was 0.4 cm 3. Mean inter- and intraobserver differences in volume measurements were 0.006 ± 0.26 cm 3 and −0.12 ± 0.29 cm 3 (mean ± standard deviation). Thrombus resolved over time at a rate of −0.042 ± 0.01 cm 3 /day ( P  <.003). The median echogenicity of thrombus at baseline expressed as the grayscale median value was 59. There was a trend for thrombus organization (measured as echogenicity) to increase with time, +0.36 ± 0.23 grayscale median units/day ( P  <.13). Adjustment for the use of anticoagulation, gender of subject, or location of DVT in the upper vs lower extremity did not alter the relationship between time and volume or time and echogenicity. We describe a 3D imaging protocol that reliably measures thrombus volume and echogenicity over time. The method is convenient and can be utilized in routine clinical practice. Acute DVT was associated with a reduction in thrombus size and trend for increased echogenicity over 1 month. This protocol will be of increasing value as our appreciation for the deleterious effects of residual thrombus after DVT increases and our utilization of aggressive thrombus removal treatments for acute DVT increases.