Pseudo continuous arterial spin labeling quantification in anemic subjects with hyperemic cerebral blood flow

Abstract

Purpose To investigate possible sources of quantification errors in global cerebral blood flow (CBF) measurements by comparing pseudo continuous arterial spin labeling (PCASL) and phase contrast (PC) MRI in anemic, hyperemic subjects. Methods All studies were performed on a Philips 3T Achieva MRI scanner. PC and PCASL CBF examinations were performed in 10 healthy, young adult subjects and 18 young adults with chronic anemia syndromes including sickle cell disease and thalassemia. CBF estimates from single and two compartment ASL kinetic models were compared. Numerical simulation and flow phantom experiments were used to explore the effects of blood velocity and B1+ on CBF quantification and labeling efficiency. Results PCASL CBF underestimated PC in both populations using a single compartment model (30.1±9.2% control, 45.2±17.2% anemia). Agreement substantially improved using a two-compartment model (−8.0 ± 6.0% control, 11.7 ± 12.3% anemia). Four of the anemic subjects exhibited venous outflow of ASL signal, suggestive of cerebrovascular shunt, possibly confounding PC-PCASL comparisons. Additionally, sub-study experiments demonstrated that B1+ was diminished at the labeling plane (82.9 ± 5.1%), resulting in suboptimal labeling efficiency. Correcting labeling efficiency for diminished B1+, PCASL slightly overestimated PC CBF in controls (−15.4 ± 6.8%) and resulted in better matching of CBF estimates in anemic subjects (0.7 ± 10.0% without outflow, 10.5 ± 9.4% with outflow). Conclusions This work demonstrates that a two-compartment model is critical for PCASL quantification in hyperemic subjects. Venous outflow and B1+ under-excitation may also contribute to flow underestimation, but further study of these effects is required.

Unwinding the path from anemia to stroke

“…Such a disconnect between global and local oxygen delivery is commonly observed in arteriovenous malformations, but recent work suggests that functional arteriovenous shunting also occurs in patients with chronic anemia syndromes, including SCD. [6][7][8] Our work using MRI oximetry of sagittal sinus blood also supports the functional shunting hypothesis. We found that children and young adults with SCD (particularly children receiving chronic transfusion therapy) exhibited inappropriately low whole-brain OEF for their degree of anemia and CBF.…”

“…Interestingly, misty and moonlight hypopigmentation mice are both the result of mutations in Dock7 that cause truncations either inside (misty) or downstream (moonlight) of DHR-1. 5,6 Although these animals have been studied for their defects in neurogenesis, misty mice have a bleeding diathesis, which mimics the NBEAL2 2/2 phenotype. 6 Moonlight mice do not have that phenotype.…”

“…5,6 Although these animals have been studied for their defects in neurogenesis, misty mice have a bleeding diathesis, which mimics the NBEAL2 2/2 phenotype. 6 Moonlight mice do not have that phenotype. 5 This convergence of phenotypes supports the physiological relevance of the Nbeal2/ Dock7 interaction; however, it is unclear how this Rac/Cdc42 GEF affects granule biogenesis.…”

Anemia predicts lower white matter volume and cognitive performance in sickle and non‐sickle cell anemia syndrome

“…Lower cerebral vascular reserve predicts white matter hyperintensities cross‐sectionally and longitudinally, presumably through acute‐on‐chronic interruptions in oxygen delivery . Additionally, low extraction reserve has been found in patients with high cerebral blood flow . This is possibly attributed to decreased diffusion time, capillary transit time heterogeneity, and/or artereo‐vascular shunting in capillary beds .…”

Cerebral blood flow and predictors of white matter lesions in adults with Tetralogy of Fallot

“…However, it assumes that longitudinal relaxation rates are identical across tissue types, making it unsuitable for accurate WM CBF estimation [15]. Therefore, we used a modified two compartment kinetic quantification model proposed by Wang et.…”