title: Effect of mechanical convection on the partitioning of an anionic iodinated contrast agent in intact patellar cartilage.
abstract: To determine if mechanical convection accelerates partitioning of an anionic contrast agent into cartilage while maintaining its ability to reflect the glycosaminoglycan (GAG) content in contrast-enhanced computed tomography (CECT) of cartilage. Bovine patellae (N = 4) were immersed in iothalamate and serially imaged over 24 h of passive diffusion at 34°C. Following saline washing for 14 h, each patella was serially imaged over 2.5 h of mechanical convection by cyclic compressive loading (120N, 1 Hz) while immersed in iothalamate at 34°C. After similar saline washing, each patella was sectioned into 15 blocks (n = 60) and contrast concentration per time point as well as GAG content were determined for each cartilage block. Mechanical convection produced 70.6%, 34.4%, and 16.4% higher contrast concentration at 30, 60, and 90 min, respectively, compared to passive diffusion (p < 0.001) and boosted initial contrast flux 330%. The correlation between contrast concentration and GAG content was significant at all time points and correlation coefficients improved with time, reaching R(2)  = 0.60 after 180 min of passive diffusion and 22.5 min of mechanical convection. Mechanical convection significantly accelerated partitioning of a contrast agent into healthy cartilage while maintaining strong correlations with GAG content, providing an evidence-based rationale for adopting walking regimens in CECT imaging protocols.
authors: Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, 02215.
authors: Vahid
authors: V
authors: Entezari
authors: Prashant N
authors: PN
authors: Bansal
authors: Rachel C
authors: RC
authors: Stewart
authors: Benjamin A
authors: BA
authors: Lakin
authors: Mark W
authors: MW
authors: Grinstaff
authors: Brian D
authors: BD
authors: Snyder
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000737:chemistry / Q000000981:diagnostic imaging* / Q000502:physiology; D002417:Cattle; D003287:Contrast Media; D004058:Diffusion; D006025:Glycosaminoglycans / Q000032:analysis*; D007483:Iothalamic Acid; D009068:Movement; D010329:Patella / Q000000981:diagnostic imaging* / Q000502:physiology; D014057:Tomography, X-Ray Computed
chemical_list: D003287:Contrast Media; D006025:Glycosaminoglycans; D007483:Iothalamic Acid
keywords: articular cartilage; contrast agent; contrast enhanced computed tomography; diffusion; mechanical convection