Abstract A097: Cerebral capillary blood transit time in sickle cell anemia

Background: The overall goal of this work is to apply novel MRI methods of vascular kinetics to test how anemia influences cerebral capillary transit times, with the ultimate goal of improving stroke risk assessments in patients with sickle cell anemia (SCA). More specifically, SCA patients have an increased risk of silent cerebral infarcts and stroke, yet patients often lack traditional stroke risk factors and imaging methods sensitive to ischemic risk are incomplete. Increased cerebral blood flow (CBF) occurs in SCA to compensate for decreased arterial oxygen content, which can lead to rapid capillary transit and reduced time for tissue oxygen delivery, an effect that manifests as dural sinus hyperintensity on arterial spin labeling (ASL) MRI. Here, we quantify blood transit times and shunted venous blood volume in control and SCA participants to test the hypothesis that quantitative arterio-venous transit time is reduced in SCA and warrants further investigation as a biomarker of ischemic risk. Methods: Adults with SCA and age- and race-matched healthy controls provided informed consent and were prospectively scanned using 3-Tesla MRI with a standard anatomical and angiography protocol supplemented with pulsed ASL MRI with 16 post-labeling times (200-3200 ms), which enabled quantification of arterial, tissue, and venous blood arrival times as well as venous shunted blood volume non-invasively in vivo (Figure 1A-C). Each variable was compared between cohorts and related to hemoglobin level with regression within SCA patients (significance: p