Making sense of scattering: Seeing microstructure through shear waves.

The physics of shear waves traveling through matter carries fundamental insights into its structure, for instance, quantifying stiffness for disease characterization. However, the origin of shear wave attenuation in tissue is currently not properly understood. Attenuation is caused by two phenomena: absorption due to energy dissipation and scattering on structures such as vessels fundamentally tied to the material's microstructure. Here, we present a scattering theory in conjunction with magnetic resonance imaging, which enables the unraveling of a material's innate constitutive and scattering characteristics. By overcoming a three-order-of-magnitude scale difference between wavelength and average intervessel distance, we provide noninvasively a macroscopic measure of vascular architecture. The validity of the theory is demonstrated through simulations, phantoms, in vivo mice, and human experiments and compared against histology as gold standard. Our approach expands the field of imaging by using the dispersion properties of shear waves as macroscopic observable proxies for deciphering the underlying ultrastructures.

The Safety and Effectiveness of Hepatic Transarterial Embolic Locoregional Therapy in Patients with Contraindications to Hepatectomy after Portal Vein Embolization.

The safety and effectiveness of hepatic transarterial embolic locoregional therapy (LRT) was assessed, including transarterial chemoembolization (TACE) and transarterial radioembolization (TARE), in patients who underwent portal vein embolization (PVE) before major hepatectomy in whom surgery was then contraindicated. Adverse events (AEs) were graded according to the Society of Interventional Radiology classification of AEs. Tumor response was assessed based on the Response Evaluation Criteria In Solid Tumors 1.1. Overall survival (OS) and progression-free survival (PFS) were estimated. Fifteen patients underwent 37 transarterial LRTs (25 TACEs, 11 TAREs, and 1 bland embolization), most (73%) with hepatocellular carcinoma. Eleven AEs occurred in 7 patients, including 2 Grade 3/5 (severe) and 2 Grade 4/5 (life-threatening) events. The best response was partial response in 4 (27%) and stable disease in 10 (66%) patients. The median OS and PFS were 42 (95% CI, 35-49 months) and 33 months (95% CI, 24-42 months), respectively. In conclusion, hepatic transarterial LRT can be considered as a therapeutic option in patients with contraindicated liver surgery after PVE.