Comparing segmented ASL perfusion of vascular territories using manual versus semiautomated techniques in children with sickle cell anemia

Abstract

Purpose Elevated cerebral blood flow (CBF) in sickle cell anemia (SCA) is an adaptive pathophysiologic response associated with decreased vascular reserve and increased risk for ischemia. We compared manual (M) and semi-automated (SA) vascular territory delineation to facilitate standardized evaluation of CBF in children with SCA. Materials and Methods ASL perfusion values from 21 children were compared for gray matter and white matter (WM) in vascular territories defined by M and SA delineation. SA delineated CBF was compared with clinical and hematologic variables acquired within 4 weeks of the MRI. Results CBF measurements from M (MCA 82 left, 79 right) and SA (MCA 81 left, 81 right) delineated territories were highly correlated (R=0.99, p < .0001). Bland-Altman plots had close-fitting limits of agreement of −1.8 to −3.5 lower limit and 0 to 1.8 upper limit. SA vascular territory delineation was comparable to the expert delineation with a kappa index of 0.62–0.85 and was considerably faster. Median territorial CBF values did not differ by gender or age. WM perfusion in the posterior cerebral artery territories was positively correlated with degree of hemolysis (R=0.58, p=.01 left, 0.73, p<.001 right) and negatively correlated with hemoglobin (R=−0.48, p=.03 left, −0.47, p=.04 right) and hemoglobin F (R=−0.42, p=.09 left, −0.47, p=.049 right). Conclusion We established the validity of the SA method, which in our experience was much faster than the M method for delineation of vascular territories. Associations between CBF and hematologic variables may demonstrate pathophysiologic changes that contribute to clinical variation in CBF.

Cerebral perfusion characteristics show differences in younger versus older children with sickle cell anaemia: Results from a multiple‐inflow‐time arterial spin labelling study

“…29 The degree of anaemia and haemolysis and haemoglobin F levels may also affect haemodynamics in the anterior and posterior circulation differently. 35 As mentioned earlier, BAT is generally longer in the PCA territory, in both SCA patients and controls. It is in this region that the correlation between blood oxygen content remains strongest in the older SCA patients, suggesting that the delayed arrival time of blood in this region necessitates a greater compensatory increase in CBF in blood with lower blood oxygenation, which may be achieved in children with SCA through adaptations including basilar artery dilation.…”

“…The degree of anaemia and haemolysis and haemoglobin F levels may also affect haemodynamics in the anterior and posterior circulation differently . As mentioned earlier, BAT is generally longer in the PCA territory, in both SCA patients and controls.…”

Cerebral hemodynamics and pseudo‐continuous arterial spin labeling considerations in adults with sickle cell anemia

“…Arterial spin labeling (ASL) is a non‐invasive MRI technique for quantitative CBF mapping and has been applied in multiple studies of SCA physiology . Recently, pseudo‐continuous ASL (pCASL), an ASL variant in which inflowing arterial blood water is magnetically labeled using a long (1000–2000 ms) string of short (<1 ms) RF pulses, has emerged as the most popular ASL technique due to its high signal‐to‐noise ratio relative to pulsed ASL and ability to be performed using widely available body coils …”

In Vivo T1 of Blood Measurements in Children with Sickle Cell Disease Improve Cerebral Blood Flow Quantification from Arterial Spin-Labeling MRI

“…6,7 CBF measurements are instrumental in understanding the pathophysiology of impaired perfusion in the occurrence of silent cerebral infarcts in SCD. 4,8,9 Noninvasive CBF measurements can be performed with arterial spin-labeling (ASL) and a quantification model to calculate physiological CBF values. The wide range of CBF values reported in the literature in SCD 1,4,9 emphasizes the need for either more accurate estimates or direct measurements of the often-assumed parameters required for CBF quantification models.…”