title: Intravascular ultrasound imaging of blood: the effect of hematocrit and flow on backscatter.
abstract: This study evaluates two key parameters influencing the ultrasonic backscatter from blood--hematocrit and flow rate--at 30 MHz in an in vitro flow system. A range of hematocrits from 0 to 50% was studied at a constant flow rate; various flow rates between stagnation and physiologic levels were studied at a constant hematocrit. The relation between backscatter intensity and hematocrit was a convex function with a maximum between a hematocrit of 10% and 20%. In the flow rate studies, the blood backscatter intensity was a maximum at a flow rate of 0 and rapidly decreased at higher flow rates. These in vitro results suggest that blood backscatter intensity is minimally dependent on hematocrit in the physiologic range. However, a dramatic increase in backscatter intensity occurs with stagnant flow, presumably the result of red blood cell aggregation. Clinically, blood backscatter intensity may provide an index for risk of thrombus formation.
authors.affiliation: Cardiovascular Research Institute, University of California, San Francisco 94143.
authors.forename: E G
authors.initials: EG
authors.lastname: Yamada
authors.forename: P J
authors.initials: PJ
authors.lastname: Fitzgerald
authors.forename: K
authors.initials: K
authors.lastname: Sudhir
authors.forename: V K
authors.initials: VK
authors.lastname: Hargrave
authors.forename: P G
authors.initials: PG
authors.lastname: Yock
mesh_terms: D000818:Animals; D001769:Blood / Q000000981:diagnostic imaging*; D001783:Blood Flow Velocity; D001808:Blood Vessels / Q000000981:diagnostic imaging; D004285:Dogs; D006400:Hematocrit; D014463:Ultrasonography