Validation of diffuse correlation spectroscopy against 15O-water PET for regional cerebral blood flow measurement in neonatal piglets

Diffuse correlation spectroscopy (DCS) can non-invasively and continuously asses regional cerebral blood flow (rCBF) at the cot-side by measuring a blood flow index (BFI) in non-traditional units of cm²/s. We have validated DCS against positron emission tomography using ¹⁵O-labeled water (¹⁵O-water PET) in a piglet model allowing us to derive a conversion formula for BFI to rCBF in conventional units (ml/100g/min). Neonatal piglets were continuously monitored by the BabyLux device integrating DCS and time resolved near infrared spectroscopy (TRS) while acquiring ¹⁵O-water PET scans at baseline, after injection of acetazolamide and during induced hypoxic episodes. BFI by DCS was highly correlated with rCBF (R = 0.94, p < 0.001) by PET. A scaling factor of 0.89 (limits of agreement for individual measurement: 0.56, 1.39)×10⁹× (ml/100g/min)/(cm²/s) was used to derive baseline rCBF from baseline BFI measurements of another group of piglets and of healthy newborn infants showing an agreement with expected values. These results pave the way towards non-invasive, cot-side absolute CBF measurements by DCS on neonates.     

Tissue hypoxaemia causes oedema, inflammation and fibrosis in porcine bronchial transsection

Abstract Objectives. Bronchial artery revascularization in lung transplantation is disputed. This study examined the physiological consequences of porcine bronchial transsection and reanastomosis with and without bronchial artery blood supply with relation to lung transplantation. Design. Translational, controlled animal study. Twelve pigs were operated through a left lateral thoracotomy. The left bronchus was transsected and reanastomosed. In the control group (n =?6), the bronchial arteries were preserved and in the study group (n =?6) they were severed. Bronchial mucosa blood flow (BMBF) was measured with laser-Doppler velocimetry and bronchial mucosa haemoglobin saturation and concentration with diffuse reflectance spectrophotometry. Measurements were made preoperatively, postoperatively and after 1 week. Results. In the study group, left postoperative BMBF was significantly lower than preoperatively (115 vs. 210 PU/s, p =?0.0001) and lower than in the control group (115 vs. 205 PU/s, p =?0.002). Repeated measurement ANOVA showed a significant treatment effect depending on time (p =?0.0034). The left mucosal haemoglobin saturation in the study group was significantly reduced postoperatively, 92% versus 61%, with a treatment effect depending on time (p =?0.0080). The reduction in left/right ratio of the mucosal haemoglobin concentration 1 week postoperatively in the study group was insignificant. Conclusion. Bronchial transsection and reanastomosis without bronchial artery blood supply was followed by significant decrease in mucosal blood flow and saturation postoperatively, and also in tissue haemoglobin concentration at section, and provides a physiologic explanation of histological changes.     

Early identification and intervention in cerebral palsy

Infants with possible cerebral palsy (CP) are commonly assumed to benefit from early diagnosis and early intervention, but substantial evidence for this is lacking. There is no consensus in the literature on a definition of ‘early’, but this review focuses on interventions initiated within the first 6 months after term age. We cover basic neuroscience, arguing for a beneficial effect of early intervention, and discuss why clinical research to support this convincingly is lacking. We argue that infants offered early intervention in future clinical studies must be identified carefully, and that the intervention should be focused on infants showing early signs of CP to determine an effect of treatment. Such signs may be efficiently detected by a combination of neuroimaging and the General Movements Assessment. We propose a research agenda directed at large‐scale identification of infants showing early signs of CP and testing of high‐intensity, early interventions.     

Positron emission tomography/magnetic resonance hybrid scanner imaging of cerebral blood flow using 15O-water positron emission tomography and arterial spin labeling magnetic resonance imaging in newborn piglets

Abnormality in cerebral blood flow (CBF) distribution can lead to hypoxic–ischemic cerebral damage in newborn infants. The aim of the study was to investigate minimally invasive approaches to measure CBF by comparing simultaneous ¹⁵O-water positron emission tomography (PET) and single TI pulsed arterial spin labeling (ASL) magnetic resonance imaging (MR) on a hybrid PET/MR in seven newborn piglets. Positron emission tomography was performed with IV injections of 20 MBq and 100 MBq ¹⁵O-water to confirm CBF reliability at low activity. Cerebral blood flow was quantified using a one-tissue-compartment-model using two input functions: an arterial input function (AIF) or an image-derived input function (IDIF). The mean global CBF (95% CI) PET-AIF, PET-IDIF, and ASL at baseline were 27 (23; 32), 34 (31; 37), and 27 (22; 32) mL/100 g per minute, respectively. At acetazolamide stimulus, PET-AIF, PET-IDIF, and ASL were 64 (55; 74), 76 (70; 83) and 79 (67; 92) mL/100 g per minute, respectively. At baseline, differences between PET-AIF, PET-IDIF, and ASL were 22% (P<0.0001) and −0.7% (P=0.9). At acetazolamide, differences between PET-AIF, PET-IDIF, and ASL were 19% (P=0.001) and 24% (P=0.0003). In conclusion, PET-IDIF overestimated CBF. Injected activity of 20 MBq ¹⁵O-water had acceptable concordance with 100 MBq, without compromising image quality. Single TI ASL was questionable for regional CBF measurements. Global ASL CBF and PET CBF were congruent during baseline but not during hyperperfusion.