42 - Feasibility of Contrast-Enhanced and Super-Resolution Ultrasound of the Neonatal Brain: The SERENE Brain Study

Publication Number: 1035.42

Anoop Ramana, Imperial College Healthcare NHS Trust, London, England, United Kingdom; Jingwen Zhu, Imperial College London, London, England, United Kingdom; Dax J. Daantos, University of Leicester, London, England, United Kingdom; Ksenija Acimovic, Imperial College London NHS Trust, London, England, United Kingdom; Kalyan Mitra, Imperial College Healthcare NHS Trust, London, England, United Kingdom; Meng-Xing Tang, Imperial College London, London, England, United Kingdom; Jayanta Banerjee, Imperial College London, London, England, United Kingdom

Background: Brain injury remains a major cause of neonatal morbidity and mortality, yet bedside assessment of cerebral microcirculation is limited. Conventional cranial ultrasound provides structural detail with low resolution and only indirect Doppler-based indices of perfusion, whilst MRI remains logistically challenging in critically ill infants. Contrast-Enhanced Ultrasound (CEUS) offers a safe, dynamic, real-time evaluation of tissue perfusion. Ultrasound localisation microscopy (ULM) is a novel technique of Super-Resolution Ultrasound (SRUS) and utilises CEUS to enable visualisation at the capillary scale, far-beyond the diffraction limit of traditional imaging. The central grey-nuclei (CGN) and cortical regions represent distinct microvascular territories in the developing brain, differing in vascular density and autoregulatory capacity, and are key sites of neonatal brain injury.

Objective: To examine the feasibility of CEUS and SRUS imaging of the neonatal brain to evaluate cerebral perfusion and microvascular dynamics.

Design/Methods: Infants admitted to a tertiary neonatal intensive care with an indwelling intravenous cannula were consecutively recruited after informed parental consent from February - August 2025. Infants deemed critically unwell were excluded. A single bedside cranial CEUS was performed using a clinical ultrasound system after an intravenous bolus of microbubble contrast. Time-intensity curves (TIC) were analysed to derive regional perfusion parameters in the CGN and cortical regions. SRUS processing reconstructed microvascular maps and capillary transit time (CTT) estimated.

Results: A total 20 infants (9 female, 11 male) were recruited and had a single CEUS at median age of 2 days (range 1-53 days). 16 infants (7 female, 9 male) were included in CEUS analysis. Cranial abnormalities on B-mode US were noted in 25% (4/16) infants. CEUS was well-tolerated with no adverse events and no significant variation (>15%) in vital signs. TIC analysis showed distinct perfusion kinetics between cortical and CGN regions (p < 0.05). Novel SRUS processing successfully visualised sub-millimetre vasculature and yielded CTT estimates.

Conclusion(s): CEUS and SRUS techniques enable safe, bedside assessment of the neonatal cerebral microvasculature. Integration of CEUS-derived perfusion parameters with SRUS-based capillary transit analysis provides new insight into cerebral microcirculatory development and injury. Larger, longitudinal studies are planned by our group to establish normative data and determine prognostic utility in neonatal brain injury.

Figure 1. Overview of the Serene Brain Study
A. Overview of the SERENE Brain Study. B. Schema of a cranial ultrasound workflow including CEUS, Time infusion/intensity curve analysis (TIC) using perfusion markers (Mgrad: Max gradient, MGT: Max gradient time, Grad: Mean gradient (to the peak), ArT: Arrival time, TtoP: Time to peak, PI: Peak intensity, TWH: Time width at half maximum, TWR: Time width ratio, AUC: Area under the curve, WiAUC: Wash in area under the curve, WoAUC: Wash out are under the curve), CEUS, multi-parametric imaging and SRUS. C. Left: B-mode scan of a female infant born 29+3 weeks gestation (1443g) performed on day 4 of life. Centre: Microbubble (MB) density map demonstrating microvascular differences between Right sided Papile Grade IV GMH-IVH and HPI and Left sided Grade III GMH-IVH with rim enhancement of ventricle and periventricular vessel engorgement. Right: Direction map with corresponding colour code depicting Left sided flow direction in peri-ventricular vessels. D. Left: Right cortical and periventricular white matter region of interest (green) with individual microbubbles selected for "Capillary transit time" CTT analysis; right: single microbubble trajectories going through the capillary bed.

Table 1. Baseline demographic data and clinical characteristics
Baseline demographic and clinical characteristics of enrolled neonates included in the SERENE Brain feasibility cohort. 4 scans were used to optimise imaging protocol thus were not included in the final analysis as images were not standardised. Values are median (range) for continuous variables and n (%) for categorical variables. IVH = Intraventricular haemorrhage.

Figure 2. Quantitative CEUS perfusion metrics
Quantitative CEUS perfusion metrics derived from time-intensity curve analysis in the central-grey nuclei (CGN) and cortical regions of the neonatal brain. Parameters were grouped according to contrast phase: A: inflow dynamics or arterial inflow (Mgrad - dB/sec, MGT - sec, Grad - dB/sec, TTP - sec), B: peak phase or indicative capillary perfusion (PI - dB, TWH - sec, TWR), and C: outflow or venous drainage (AUC*, WiAUC, WoAUC). *AUC is indicative of the total perfusion over time (inflow + outflow). CGN regions demonstrated significantly steeper gradients and greater AUC values, suggesting higher perfusion efficiency and vascular reactivity compared with cortical regions. Whiskers indicate interquartile ranges; asterisks denote parameters with significant regional differences (p < 0.05). Abbreviations: Mgrad: Max gradient, MGT: Max gradient time, Grad: Mean gradient (to the peak), ArT: Arrival time, TtoP: Time to peak, PI: Peak intensity, TWH: Time width at half maximum, TWR: Time width ratio, AUC: Area under the curve, WiAUC: Wash in area under the curve, WoAUC: Wash out are under the curve)