Quantitative tissue echogenicity of the neonatal brain assessed by ultrasound imaging

Ultrasound Diagnosis and Near-Infrared Spectroscopy in the Study of Encephalopathy in Neonates Born under Asphyxia: Narrative Review

Brain injury resulting from adverse events during pregnancy and delivery is the leading cause of neonatal morbidity and disability. Surviving neonates often suffer long-term motor, sensory, and cognitive impairments. Birth asphyxia is among the most common causes of neonatal encephalopathy. The integration of ultrasound, including Doppler ultrasound, and near-infrared spectroscopy (NIRS) offers a promising approach to understanding the pathology and diagnosis of encephalopathy in this special patient population. Ultrasound diagnosis can be very helpful for the assessment of structural abnormalities associated with neonatal encephalopathy such as alterations in brain structures (intraventricular hemorrhage, infarcts, hydrocephalus, white matter injury) and evaluation of morphologic changes. Doppler sonography is the most valuable method as it provides information about blood flow patterns and outcome prediction. NIRS provides valuable insight into the functional aspects of brain activity by measuring tissue oxygenation and blood flow. The combination of ultrasonography and NIRS may produce complementary information on structural and functional aspects of the brain. This review summarizes the current state of research, discusses advantages and limitations, and explores future directions to improve applicability and efficacy.

Quantitative ultrasonographic examination of cerebral white matter by pixel brightness intensity as marker of middle-term neurodevelopment: a prospective observational study

Non-cystic white matter (WM) injury has become prevalent among preterm newborns and is associated with long-term neurodevelopmental impairment. Magnetic resonance is the gold-standard for diagnosis; however, cranial ultrasound (CUS) is more easily available but limited by subjective interpretation of images. To overcome this problem, we enrolled in a prospective observational study, patients with gestational age at birth < 32 weeks with normal CUS scans or grade 1 WM injury. Patients underwent CUS examinations at 0-7 days of life (T0), 14-35 days of life (T1), 370/7-416/7 weeks' postmenstrual age (T2), and 420/7-520/7 weeks' postmenstrual age (T3). The echogenicity of parieto-occipital periventricular WM relative to that of homolateral choroid plexus (RECP) was calculated on parasagittal scans by means of pixel brightness intensity and its relationship with Bayley-III assessment at 12 months' corrected age was evaluated. We demonstrated that: (1) Left RECP values at T1 negatively correlated with cognitive composite scores; (2) Right RECP values at T2 and T3 negatively correlated with language composite scores; (3) Left RECP values at T1 and T2 negatively correlated with motor composite scores. Thus, this technique may be used as screening method to early identify patients at risk of neurodevelopmental issues and promptly initiate preventive and therapeutic interventions.

Quantitative Evaluation of Brain Echogenicity in Hypoxic-Ischemic Encephalopathy in Term Neonates Compared with Controls

Purpose Neurosonography evaluation of neonatal hypoxic-ischemic encephalopathy (HIE) is mainly qualitative. We aimed to quantitatively compare the echogenicity of several brain regions in patients with HIE to healthy controls. Materials and Methods 20 term neonates with clinical/MRI evidence of HIE and 20 term healthy neonates were evaluated. Seven brain regions were assessed [frontal, parietal, occipital, and perirolandic white matter (WM), caudate nucleus head, lentiform nucleus, and thalamus]. The echogenicity of the calvarial bones (bone) and the choroid plexus (CP) was used for ratio calculation. Differences in the ratios were determined between neonates with HIE and controls. Results Ratios were significantly higher for HIE neonates in each region (p<0.05). The differences were greatest for the perirolandic WM, with CP and bone ratios being 0.23 and 0.22 greater, respectively, for the HIE compared to the healthy neonates (p<0.001). The perirolandic WM had a high AUC, at 0.980 for both the CP and bone ratios. The intra-observer reliability for all ratios was high, with the caudate to bone ratio being the lowest at 0.832 and the anterior WM to CP ratio being the highest at 0.992. Conclusion When coupled with internal controls, quantitative neurosonography represents a potential tool to identify early neonatal HIE changes. Larger cohort studies could reveal whether a quantitative approach can discern between degrees of severity of HIE. Future neurosonography protocols should be tailored to evaluate the perirolandic region, which requires posterior coronal scanning.

Early Prediction of Periventricular Leukomalacia Using Quantitative Texture Analysis of Serial Cranial Ultrasound Scans in Very Preterm Infants

We compared texture parameters of serial cranial ultrasound (cUS) images of periventricular leukomalacia (PVL) and normal periventricular echogenicity (PVE) in very preterm infants and evaluated the early predictive values of texture analysis (TA) for PVL. Ten individuals with PVL and 10 control individuals with PVE assessed with an initial cUS within 1 wk of birth and follow-up cUS at 2-3 and 4-6 wk of life were included. TA was performed on the region of interest of PVE at the parieto-occipital area on serial cUS. Opposite changes in variance were obtained between the first two cUS sessions in both groups (p = 0.017 in PVL and p = 0.005 in PVE). The variance-to-mean ratio (VMR) between the second and first cUS sessions differed (p = 0.016) and reliably stratified the groups (area under the receiver operating characteristic curve: 0.820, 95% confidence interval: 0.587-1.000, sensitivity: 100%, specificity: 60%). TA of serial cUS helps to predict PVL within 3 wk of life.

Objective image analysis of real-time three-dimensional intraoperative ultrasound for intrinsic brain tumour surgery

Background

There is growing evidence that maximal surgical resection of primary intrinsic brain tumours is beneficial, both by improving progression free and overall survival and also by facilitating postoperative chemotherapy and radiotherapy. Hence, there has been an increase in the popularity of real-time intraoperative imaging in brain tumour surgery. The complex theatre arrangements, prohibitive cost and prolonged theatre time of intraoperative MRI have restricted its application. By comparison, intraoperative three-dimensional ultrasound (i3DUS) is user friendly, cost-effective and portable and adds little to surgical time. However, operator-dependent image quality and image interpretation remain limiting factors to the wider application of this technique. The aim of this study was to explore objective i3DUS image analysis and its potential therapeutic role in brain tumour surgery.

Methods

A prospective, observational study was undertaken (approved by the local Research and Ethics Committee prior to recruitment). Biopsies were taken from the solid, necrotic, periphery and brain/tumour interface of intrinsic primary brain tumours. Digital i3DUS images were analysed to extract quantitative parameters from these regions of interest (ROI) in the i3DUS images. These were then correlated with the histology of the relevant specimens. The histopathologist was blinded to the imaging findings.

Results

Ninety-seven patients (62 males; mean 54 years) with varying gliomas (84 high grade) were included. Two hundred and ninety regions of interest were analysed. Mean pixel brightness (MPB) and standard deviation (SD) were correlated with histological features. Close correlations were noted between MPB and cellularity, and SD and intrinsic cellular diversity.

Conclusions

MPB and SD are objective measures reflecting the sensitivity of i3DUS in detecting the presence and extent of intrinsic brain tumours. They indirectly suggest heterogeneity, cellularity and invasiveness, providing information of the nature of the tumour, and also reflect the sensitivity of intraoperative US to detect the presence of residual intrinsic brain tumours. Development of this paradigm will enhance i3DUS use as an adjunct in brain tumour surgery. Optimizing its intraoperative application will impact surgical resection and, hence, patient outcome.

Early diagnosis and outcome prediction of neonatal hypoxic-ischemic encephalopathy with color Doppler ultrasound

PURPOSE

To describe the ultrasound presentation of the brain and cerebral hemodynamics in neonates with hypoxic-ischemic encephalopathy (HIE) by comparison with control subjects.

MATERIAL AND METHODS

During June 2012 to April 2013, full term neonates who had clinical evidence of HIE were enrolled. Healthy newborns without HIE were used as a control group. Cerebral parenchyma, size of lateral ventricles and hemodynamic parameters of cerebral arteries were studied using two-dimensional duplex and color Doppler ultrasound. Neonates with moderate and severe HIE were followed-up with ultrasound for at least 3 months.

RESULTS

A total of 158 consecutive neonates (82 boys and 76 girls), including 54 with mild HIE, 60 with moderate HIE and 44 with severe HIE were included. One hundred and twenty healthy newborns were randomly selected as a control group. Abnormal ultrasound findings of brain parenchyma were found in 25/54 (46.3%) neonates with mild HIE whereas they were found in 58/60 (96.7%) neonates with moderate HIE and 44/44 (100%) neonates with severe HIE. Almost all neonates with severe HIE had decreased cerebral artery blood flow velocity and increased resistance index of cerebral arteries. Of the 104 neonates with moderate or severe HIE, follow-up ultrasound examination revealed cystic parenchymal lesions in 12/104 (11.5%), progressive ventricular dilatation and brain atrophy in 12/104 (11.5%), mild ventricular dilatation in 15/104 (14.4%) and leukoencephalomalacia in 2/104 (1.9%) neonates.

CONCLUSION

Ultrasound features such as the size of lateral ventricles, altered brain parenchymal echogenicity and cerebral blood flow parameters are useful for the early diagnosis of HIE and help predict outcome.

Relative Echogenicity of Tendons and Ligaments of the Palmar Metacarpal Region in Foals from Birth to 4 Months of Age: A Longitudinal Study

The objective of this study was to evaluate relative echogenicity of superficial and deep digital flexor tendons, the accessory ligament of the deep digital flexor tendon and interosseous muscle of the metacarpal region in foals ages 1 week to 4 months; and assess the association between echogenicity and sex or side/laterality. Seven Standardbred trotter foals were examined. Right and left metacarpal regions (palmar surface) were ultrasonographically investigated, and four regions of interest were assessed. A significant increase in echogenicity was seen in superficial and deep digital flexor tendons, accessory ligament of deep digital flexor tendon, and interosseous muscle during growth from 1 week to 4 months of age. Echogenicity of examined tendons and ligaments was not influenced by gender nor laterality. Reference values for tendon and ligament echogenicity could function as a tool to discriminate between physiological and abnormal conditions such as congenital contractural conditions.

Quantitative analysis of cranial ultrasonographic periventricular echogenicity in relation to early neuromotor development in preterm infants

BACKGROUND

Periventricular white matter (WM) hyperechoic flares that do not evolve into cystic lesion(s) are frequently encountered on cranial ultrasonography (CUS) of preterm infants. Subjective interpretation of its presence, however, is challenging and its association with maturation and neurodevelopment remains undefined.

OBJECTIVES

To determine the relationship between quantitative WM echogenicity and postnatal and postmenstrual ages and the relationship between quantitative WM echogenicity and neuromotor development at term equivalent.

METHODS

We measured the mean pixel brightness intensity at the frontoparietal and parieto-occipital WM, choroid plexus and calvarium bone on sequential neonatal CUS scans of preterm infants born at <34 weeks gestation. The relative echogenicity (RE) was derived by dividing the mean WM echogenicity to that of the choroid plexus (RE(CP)) or bone (RE(BN)). The Lacey Assessment of the Preterm Infant was administered before discharge.

RESULTS

58 preterm infants (the mean gestational age 30.6±2.3 weeks and the mean birth weight 1211.9±224.7 g) were included. The RE(CP) of the frontoparietal WM decreased significantly with advancing postnatal and postmenstrual ages (r=-0.4, p<0.0001). The RE(BN) values of the frontoparietal and parieto-occipital WM during intermediate and late predischarge CUS studies, respectively, were significantly associated with neuromotor status at term (p<0.05). The RE(CP) and RE(BN) measured during the first week of life were not associated with neuromotor status at term.

CONCLUSIONS

Quantitative measurements of the periventricular WM echogenicity are feasible in neonatal CUSs of premature infants and may reflect microstructural developmental changes. An optimal echogenicity quantification technique and its correlation with long-term outcome remain to be determined.

Quantitative Sonographic Texture Analysis in Preterm Neonates With White Matter Injury: Correlation of Texture Features With White Matter Injury Severity

OBJECTIVES

To analyze the texture features on cranial sonography in preterm neonates with white matter injury quantitatively and to correlate these features with magnetic resonance imaging (MRI).

METHODS

The study included 33 preterm neonates treated in our neonatal intensive care unit who underwent serial cranial sonography and brain MRI near term. Patients were subdivided into 3 groups according to the presence and severity of white matter injury as revealed by MRI: normal (group 1; n = 20), mild (group 2; n = 5), and severe (group 3; n = 8). The periventricular echogenicity on sonography was evaluated quantitatively with second-order gray-level statistics (gray-level co-occurrence matrix [GLCM] method). Four GLCM texture features representing homogeneity were extracted in 12 directions: (1) angular second moment (ASM), (2) inverse differential moment (IDM), (3) contrast, and (4) entropy.

RESULTS

Thirty of 48 features showed a statistically significant difference between groups 1 and 3 (ASM in 9 directions, IDM in 6 directions, contrast in 3 directions, and entropy in all 12 directions). There were no significant differences observed between groups 1 and 2 or groups 2 and 3. The mean contrast and entropy values were generally lower in group 1 than group 3, whereas the mean ASM and IDM values were higher in group 1.

CONCLUSIONS

Severe white matter injury could be identified by using GLCM texture analysis, whereas mild white matter injury observed on MRI could not be evaluated by GLCM analysis. Quantitative texture analysis using the GLCM may serve as a complementary tool for quantitative assessment of periventricular echogenicity.

White-gray matter echogenicity ratio and resistive index: sonographic bedside markers of cerebral hypoxic-ischemic injury/edema?

OBJECTIVE

Head ultrasonography (HUS) is a reliable and easy to perform bedside imaging technique that can give valuable information about degree of brain injury/edema after perinatal asphyxia in term neonates. The goals of our study were to determine whether semiquantitative markers such as standardized white matter/gray matter (WM/GM) echogenicity ratio and resistive index (RI) value measured by HUS differs between asphyxiated term neonates and healthy controls.

STUDY DESIGN

Thirty-one carefully selected term neonates who suffered from perinatal hypoxic-ischemic encephalopathy (HIE) were included in the study. The ratio of the WM/GM echogenicity of the cingulate gyrus was calculated. In addition, the RI value was measured in the anterior cerebral artery. US scalars were compared with 11 healthy neonates.

RESULT

WM/GM ratio is significantly increased and RI value significantly decreased in asphyxiated term neonates compared with healthy subjects.

CONCLUSION

WM/GM ratio and RI value allows discriminating between asphyxiated neonates and healthy subjects. These US scalars may serve as valuable, easy to acquire semiquantitative bedside markers of brain HIE, when magnetic resonance imaging is unavailable or cannot be performed in the acute setting.