Abstract 440: Non-Invasive Quantification of Rat Vasculature Biomechanical Properties Under a Cardiovascular Challenge: Implications in Atherosclerosis Progression

Introduction: Measurements of cyclic strain give insight into vessel wall properties, offer a better understanding of the pathogenesis of atherosclerosis, and can be used in quantifying loss of vessel compliance. Using dobutamine stimulation to increase heart rate and cardiac output provides a clinically relevant means to begin to understand alterations in cyclic strain during a vascular challenge which mimics some aspects of exercise. Similar work has been completed in murine models, but translating these methods to a species that is an order of magnitude larger allows for a better understanding of how these results could allometrically scale to the human condition. We hypothesize that using a pharmacological cardiovascular stimulant will cause cyclic strain shifts that vary between species. Materials and Methods: Cyclic strain was non-invasively quantified using MRI. Young rats and mice were anesthetized using isoflurane and imaged at 7T. 2D and 3D gradient echo data were used to plan ECG-gated acquisitions that included 12 CINE frames across the cardiac cycle, in the infrarenal aorta pre- and post- dobutamine infusion. Vessel strain was quantified in each CINE frame. Results: Baseline strain in rats was 17% and 16%, for males and females respectively (A, C). In mice, baseline strain was 22% in males and 18% in females (B, D). After infusion of dobutamine, strain in rats increased to 26% in males and 27% in females, while in mice strain increased to 36% in males and 32% in females. Conclusions: In conclusion, there are evident variations in cyclic strain under a cardiovascular challenge between species. With this insight, a clearer understanding of the biomechanical forces experienced by the vasculature in different species may lead to improved extrapolation from mouse to human in understanding the effects of atherosclerosis on vessel compliance and developing therapeutic approaches.

Radiation dose reduction during neurointerventional procedures by modification of default settings on biplane angiography equipment

BackgroundNeurointerventional procedures represent a significant source of ionizing radiation. We sought to assess the effect during neurointerventional procedures of varying default rates of radiation dose in fluoroscopy (F) and image acquisition (IA) modes, and frame rates during cine acquisition (CINE) on total X-ray dose, acquisition exposures, fluoroscopy time, and complications.MethodsWe retrospectively reviewed procedures performed with two radiation dose and CINE settings: a factory setting dose cohort (30 patients, F 45 nGy/pulse, IA 3.6 μGy/pulse, factory CINE frame rate) and a reduced dose cohort (30 patients, F 32 nGy/pulse, IA 1.2 μGy/pulse, with a decreased CINE frame rate). Total radiation dose, dose area product, number of acquisition exposures, fluoroscopy time, and complications were compared between the groups. Means comparisons (t tests) were employed to evaluate differences in the outcome variables between the two groups. p Value <0.05 was considered significant.ResultsThe reduced dose cohort had a significant reduction in mean radiation dose (factory, 3650 mGy; reduced, 1650 mGy; p=0.005) and dose area product (factory, 34 700 μGy×m2; reduced, 15 000 μGy×m2; p=0.02). There were no significant differences between cohorts in acquisition exposure (p=0.73), fluoroscopy time (p=0.45), or complications.ConclusionsSignificant reductions in radiation dose delivered by neurointerventional procedures can be achieved through simple modifications of default radiation dose in F and IA and frame rate during CINE without an increase in procedural complexity (fluoroscopy time) or rate of complications.