Noninvasive Measurements of Regional Cerebral Perfusion in Preterm and Term Neonates by Magnetic Resonance Arterial Spin Labeling

Abstract

Magnetic resonance arterial spin labeling (ASL) at 3 Tesla has been investigated as a quantitative technique for measuring regional cerebral perfusion (RCP) in newborn infants. RCP values were measured in 49 healthy neonates: 32 preterm infants born before 34 wk of gestation and 17 term-born neonates. Examinations were performed on unsedated infants at postmenstrual age of 39 -40 wk in both groups. Due to motion, reliable data were obtained from 23 preterm and 6 term infants. Perfusion in the basal ganglia (39 and 30 mL/100 g/min for preterm and term neonates, respectively) was significantly higher (p Ͻ 0.0001) than in cortical gray matter (19 and 16 mL/100 g/min) and white matter (15 and 10 mL/100 g/min), both in preterm neonates at term-equivalent age and in term neonates. Perfusion was significantly higher (p ϭ 0.01) in the preterm group than in the term infants, indicating that RCP may be influenced by developmental and postnatal ages. This study demonstrates, for the first time, that noninvasive ASL at 3T may be used to measure RCP in healthy unsedated preterm and term neonates. ASL is, therefore, a viable tool that will allow serial studies of RCP in high-risk neonates. H igh-risk neonates, either infants born prematurely or asphyxiated infants born at term, have a vulnerable cerebral circulation (1). Impaired autoregulation of the CBF and thus cerebral perfusion contributes to some extent to the development of brain damage in those infants (2-4). Other mechanisms, as inflammation-mediated perfusion disturbances might also be implicated in brain damage development (5), however, this point has not yet been demonstrated.Studies of the cerebral circulation have previously been performed using different invasive methods as xenon clearance (1,6), positron emission tomography (PET) (7,8), and SPECT (9). Noninvasive approaches for estimating global CBF, e.g. Doppler ultrasonography and NIRS (10) have been used achieving only a limited use (11). NIRS as a cot-side method for measuring CBF was described in the late 1980s (12) but has not yet become a routine application, probably because methodological limitations are a problem in quantitative NIRS perfusion measurements. However, quantitative measurements of CBF in neonates have recently been performed with sonographic flowmetry of carotid and vertebral arteries (13)(14)(15)(16). From these studies, it is known that global CBF increases with PMA; however, quantitative regional brain perfusion data and the influence of postnatal age beyond the first 2 wk of life (16) are not yet available on healthy neonates.In recent years, a noninvasive magnetic resonance (MR) method for accurately measuring regional brain perfusion has been developed (17). MR-Atrial spin labeling (ASL) is a completely noninvasive MR technique that enables accurate maps of RCP to be acquired in a few minutes. As this MR method is noninvasive and safe, even in very young infants, the measurements may be repeated, e.g. for monitoring changes in perfusion or response to treatment.The basic...

Phase-Contrast Magnetic Resonance Angiography Measurements of Global Cerebral Blood Flow in the Neonate

“…This means that mean CBF in this study can be estimated to ϳ20 mL/100 g/min. This is a bit higher than existing estimates using extracranial Doppler, Xenon, and arterial spin labeling MRI (ASL) (8,12,19).…”

“…Ionizing radiation is involved in these techniques or they are invasive or need special requirements, which limit their use. Arterial spinlabeled perfusion MRI (8) and sophisticated NIRS techniques such as optical diffuse correlation spectroscopy are developed at this moment to evaluate neonatal CBF (9); however, improvements are necessary before these devices can reliably be used. It may be clear that the above-mentioned methods are not (yet) available for clinical use in the vulnerable and unstable (preterm) neonate.…”

Brain Perfusion Imaging in Neonates: An Overview

“…Miranda et al 71 were the first to show the feasibility of pulsed ASL at 1.5T in 29 unsedated healthy preterm infants at term-equivalent age and in term neonates. Other studies in healthy children show that ASL appears sensitive to regional and age-related differences in CBF in preterm, term neonates, and infants at 3 months 72 and from 3 to 5 months of age.…”

Evaluation of perinatal arterial ischemic stroke using noninvasive arterial spin labeling perfusion MRI

“…In addition, low brain perfusion in neonates increases this issue. A previous ASL MRI study (8) in neonates also demonstrated low perfusion values, 16.6 ml/100 g/min in term-born infants imaged at term age. These values were slightly higher than ours.…”

“…Furthermore, a relation between perfusion in the affected hemisphere and outcome has been shown (5). Although noninvasive ASL perfusion imaging seems to be a promising tool in the neonatal population, experience is still limited (6)(7)(8)(9)(10)(11), and only one study has described the use of ASL MRI in the evaluation of PAIS (10). In this study, it was shown that ASL MRI could demonstrate areas of hypo-and hyperperfusion in patients with PAIS.…”