Evaluation of Neonatal Brain Parenchyma Using 2-Dimensional Shear Wave Elastography

Unveiling the potential of ultrasound in brain imaging: Innovations, challenges, and prospects

Within medical imaging, ultrasound serves as a crucial tool, particularly in the realms of brain imaging and disease diagnosis. It offers superior safety, speed, and wider applicability compared to Magnetic Resonance Imaging (MRI) and X-ray Computed Tomography (CT). Nonetheless, conventional transcranial ultrasound applications in adult brain imaging face challenges stemming from the significant acoustic impedance contrast between the skull bone and soft tissues. Recent strides in ultrasound technology encompass a spectrum of advancements spanning tissue structural imaging, blood flow imaging, functional imaging, and image enhancement techniques. Structural imaging methods include traditional transcranial ultrasound techniques and ultrasound elastography. Transcranial ultrasound assesses the structure and function of the skull and brain, while ultrasound elastography evaluates the elasticity of brain tissue. Blood flow imaging includes traditional transcranial Doppler (TCD), ultrafast Doppler (UfD), contrast-enhanced ultrasound (CEUS), and ultrasound localization microscopy (ULM), which can be used to evaluate the velocity, direction, and perfusion of cerebral blood flow. Functional ultrasound imaging (fUS) detects changes in cerebral blood flow to create images of brain activity. Image enhancement techniques include full waveform inversion (FWI) and phase aberration correction techniques, focusing on more accurate localization and analysis of brain structures, achieving more precise and reliable brain imaging results. These methods have been extensively studied in clinical animal models, neonates, and adults, showing significant potential in brain tissue structural imaging, cerebral hemodynamics monitoring, and brain disease diagnosis. They represent current hotspots and focal points of ultrasound medical research. This review provides a comprehensive summary of recent developments in brain imaging technologies and methods, discussing their advantages, limitations, and future trends, offering insights into their prospects.

Role of Brain Elastography in the Neonatal Setting: State of the Art of Ultrasonographic Techniques and Future Perspectives

Magnetic resonance imaging is currently used in the neonatal setting for assessing features of the neonatal brain. However, its utilization is constrained by logistic, technical, or clinical challenges. Brain elastography is a new research technique which enhances the diagnostic capability of traditional imaging, and can be paired with both ultrasonography and magnetic resonance imaging. In particular, brain elastography adds objective and quantitative information to traditional imaging by detecting differences in tissue elasticity/stiffness, which may represent a surrogate marker of the physiologic and pathologic features of the neonatal brain. To date, very limited experience exists about the use of brain elastography specifically in the neonatal setting. The aim of the present review was to describe the most recent information about the feasibility and diagnostic accuracy of brain ultrasound elastography (USE) in neonates, and to provide information about the possible future applications and perspectives of brain elastography.

Transfontanellar shear wave elastography of the neonatal brain for quantitative evaluation of white matter damage

Cerebral white matter damage (WMD) is the most frequent brain lesion observed in infants surviving premature birth. Qualitative B-mode cranial ultrasound (cUS) is widely used to assess brain integrity at bedside. Its limitations include lower discriminatory power to predict long-term outcomes compared to magnetic resonance imaging (MRI). Shear wave elastography (SWE), a promising ultrasound imaging modality, might improve this limitation by detecting quantitative differences in tissue stiffness. The study enrolled 90 neonates (52% female, mean gestational age = 30.1  ± 4.5 weeks), including 78 preterm and 12 term controls. Preterm neonates underwent B-mode and SWE assessments in frontal white matter (WM), parietal WM, and thalami on day of life (DOL) 3, DOL8, DOL21, 40 weeks, and MRI at term equivalent age (TEA). Term infants were assessed on DOL3 only. Our data revealed that brain stiffness increased with gestational age in preterm infants but remained lower at TEA compared to the control group. In the frontal WM, elasticity values were lower in preterm infants with WMD detected on B-mode or MRI at TEA and show a good predictive value at DOL3. Thus, brain stiffness measurement using SWE could be a useful screening method for early identification of preterm infants at high WMD risk.Registration numbers: EudraCT number ID-RCB: 2012-A01530-43, ClinicalTrial.gov number NCT02042716.

Advanced Neuromonitoring Modalities on the Horizon: Detection and Management of Acute Brain Injury in Children

Timely detection and monitoring of acute brain injury in children is essential to mitigate causes of injury and prevent secondary insults. Increasing survival in critically ill children has emphasized the importance of neuroprotective management strategies for long-term quality of life. In emergent and critical care settings, traditional neuroimaging modalities, such as computed tomography and magnetic resonance imaging (MRI), remain frontline diagnostic techniques to detect acute brain injury. Although detection of structural and anatomical abnormalities remains crucial, advanced MRI sequences assessing functional alterations in cerebral physiology provide unique diagnostic utility. Head ultrasound has emerged as a portable neuroimaging modality for point-of-care diagnosis via assessments of anatomical and perfusion abnormalities. Application of electroencephalography and near-infrared spectroscopy provides the opportunity for real-time detection and goal-directed management of neurological abnormalities at the bedside. In this review, we describe recent technological advancements in these neurodiagnostic modalities and elaborate on their current and potential utility in the detection and management of acute brain injury.

Ultrasonography and elastography of the brain and cerebellum of English Bulldog fetuses

The aim of this study was to evaluate B-mode ultrasonography and ARFI elastography of the central nervous system of canine fetuses as complementary methods to predict gestational age, monitor fetal development and establish standards. Ultrasound examinations were performed on 26 English Bulldog bitches at 34, 49 and 60 days of gestation. The circumference (C), area (A) and diameters of the short (D1) and long (D2) axis of the two cerebral hemispheres of the fetuses in cross-section were measured. Fetal cerebellum shape, echotexture, echogenicity, and transverse diameter (TCD) were evaluated in cross-section. Elastography was performed obtaining color elastograms and mean shear wave velocity (SWV m/s) of the fetal brain and cerebellar tissues. Ultrasound variables were correlated with gestational day (GD). Brain masses had a circular to oval shape, hyperechoic echogenicity, and homogeneous echotexture. C and D1 were the more accurate variables to predict gestational day, with the formulas: GD = 19.38 + 2,06∗C (R² = 81%) and GD = 18.93 + 7.45∗D1 (R² = 82%). Cerebellum had a "banana" shape, with hyperechogenic edges, hypoechoic echogenicity, and homogeneous echotexture. The TCD (P = 0.0001) and cerebellar stiffness (P = 0.0006) were greater at 60 days than at 49 days of gestation. The brain mass SWV was correlated positively with GD (P = 0.0001) and showed a gradual increase (P = 0.0001) in the three gestational timepoints evaluated. According to qualitative elastography, both brain mass and cerebellum became more rigid over the course of gestational days. It was possible to verify the development of the brain and cerebellum of canine fetuses during pregnancy by ultrasonographic characteristics and B-mode dimensions, as well as by evaluating the elasticity of these tissues through elastography. These unpublished findings allow a better follow-up of the central nervous system development in the prenatal period and may help in future studies with canine fetuses that present cerebral and cerebellar abnormalities.

Compression Elastography and Shear Wave Ultrasound Elastography for Measurement of Brain Elasticity in Full-Term and Premature Neonates: A Prospective Study

OBJECTIVES

To investigate the brain tissue elasticity in normal term and premature neonates using compression elastography and shear wave elastography.

METHODS

This prospective observational study enrolled term and premature neonates admitted to the Third Affiliated Hospital of Guangzhou Medical University between July 2019 and December 2020.

RESULTS

A total of 106 neonates, including 65 premature neonates and 41 term neonates, were enrolled. The elastic modulus of the frontal white matter in males was significantly lower than in females (11.67 ± 0.98 versus 12.25 ± 1.31, P = .030), but the shear wave velocity of the thalamus in males was significantly lower than in females (1.18 ± 0.13 versus 1.82 ± 0.10, P < .001). There was no significant correlation between real-time body weight and brain tissue elasticity including elastic modulus and shear wave velocity. But, the shear wave velocity of parietal white matter (r = 0.319, P = .014) and thalamus (r = -0.268, P = .040) and the elastic modulus of parietal white matter (r = 0.356, P = .006) were correlated with corrected gestational age.

CONCLUSIONS

Clinicians may consider using elastography to determine brain tissue elasticity in term and preterm neonates.

Brain contrast-enhanced ultrasonography and elastography in infants

Advanced ultrasound techniques, including brain contrast-enhanced ultrasonography and elastography, are increasingly being explored to better understand infant brain health. While conventional brain ultrasonography provides a convenient, noninvasive means of assessing major intracranial pathologies, its value in revealing functional and physiologic insights into the brain lags behind advanced imaging techniques such as magnetic resonance imaging. In this regard, contrast-enhanced ultrasonography provides highly precise functional information on macrovascular and microvascular perfusion, while brain elastography offers information on brain stiffness that may be associated with relevant physiological factors of diagnostic, therapeutic, and/or prognostic utility. This review details the technical background, current understanding and utility, and future directions of these two emerging advanced ultrasound techniques for neonatal brain applications.

Ultrasound elastography in children - nice to have for scientific studies or arrived in clinical routine?

Ultrasound elastography (USE) is a modality that in addition to fundamental B-mode, Doppler, and contrast-enhanced sonography is suitable to make qualitative and quantitative statements about the stiffness of tissues. Introduced more than 20 years ago in adults, USE becomes now a diagnostic tool also in children. The aim of this paper is to describe current available techniques for USE in children. The significance for routine use in children is shown, and further interesting applications are reported.

Real-time shear wave elastography evaluation of the correlation between brain tissue stiffness and body mass index in premature neonates

BACKGROUND

Real-time shear wave elastography (SWE) is non-invasive and reliable for quantitatively evaluate stiffness of tissues and organs. Until now, little researches have applied SWE to evaluate brain tissue of premature neonates. This study sought to compare differences in the average brain tissue elasticity modulus (Emean) values of neonates, and explore the factors affecting these differences.

METHODS

In total, 159 neonates admitted from December 2019 to February 2021 were taken as the study subjects and divided into 2 groups based on their time of birth. Premature neonates, full-term neonates, and neonates with neonatal pneumonia were included in this study. Of the 159 neonates, 76 were premature and 83 were full-term. SWE was used to quantitatively evaluate the Emean of bilateral paraventricular white matter, thalamus, and choroid, and to analyze the relationship between body mass index (BMI) and Emeans in both groups of neonates.

RESULTS

The Emeans of the paraventricular white matter, thalamus, and choroid of the premature neonates were lower than those of the full-term neonates (P<0.001). The BMI of the premature and full-term neonates was positively correlated to the bilateral paraventricular white matter, thalamus, and choroid Emean.

CONCLUSIONS

SWE can be used to quantitatively evaluate the brain tissue stiffness of neonates, and as a reference for neonatal brain-related diseases.

Evaluation of the relationship between placental stiffness measured by shear wave elastography and perinatal outcomes in women with gestational diabetes mellitus

BACKGROUND

Recently, studies on placental elastography in high-risk pregnancies continue to increase. The shear wave technique can contribute to the management of gestational diabetes mellitus (GDM) and improve perinatal outcomes by measuring placental stiffness.Purpose: To evaluate the relationship between placental stiffness measured by shear wave elastography (SWE) and perinatal outcomes in women with GDM.Material and Methods: This prospective cross-sectional study was conducted at our hospital between March and October 2020. The participants were divided into three groups: GDM-A1 group (regulated by dietary modifications); GDM-A2 group (needed pharmacologic treatment); and low-risk pregnancy (LRP) group. Both SWE and shear wave velocity (SWV) were measured in the placenta during pregnancy.

RESULTS

In total, 111 women were included in the study. The mean SWE (kPa) values for the GDM-A1, GDM-A2, and LRP groups were 10.4 (range 3.1-23.3), 13 (range 4.3-29.6), and 8.3 (range 3.2-15.1), respectively. The mean HbA1c and fasting glucose values of diabetes groups showed strongly positive correlation with mean SWE and SWV values (P < 0.001, r=0.875; P < 0.001, r=0.856; P < 0.001, r=0.791; P < 0.001, r=0.740), respectively. The SWE values of central maternal and fetal surfaces of the placenta (P=0.01, r=0.242; P < 0.001, r=0.333) showed a moderately positive correlation with admission to the neonatal intensive care unit.

CONCLUSION

Placental stiffness has increased in the GDM-A2 group when compared to the GDM-A1 and LRP groups. We also observed a strong positive correlation between HbA1c, fasting glucose values, and increased elasticity values in diabetic patients with metabolic dysregulation that may have clinical value.

Diagnostic Accuracy of Longitudinal Evaluation of Central Nervous System Sonoelastography in Preterm and Term Neonates

OBJECTIVES

The objective of this study was to evaluate the brain elasticity of the central nervous system in preterm and term neonates.

METHODS

Seventy-seven healthy preterm and term neonates (mean gestational age [GA], 37.5 weeks; range, 32.6-40.5 weeks) were included in the study. Periventricular and subcortical white matter, cortical gray matter, and ventricle and subdural spaces were examined with strain elastography ratios. Each patient underwent sonography evaluation twice. The mean age at the time of sonographic evaluation was 9 days (range, 4-15 days) for the first evaluation and 37 days (range, 31-47 days) for the second evaluation. The ratios were correlated with GA, birth weight.

RESULTS

The caudate nucleus and cortical gray matter strain ratios were significantly higher than the periventricular and subcortical white matter strain ratios (P < 0.001). There was a positive relationship between GA and periventricular white matter elastographic scores on the two measurements (P = 0.022 and 0.018, respectively). The term neonates have higher strain rations compared with the preterm neonates at the first assessment (P < 0.01). At the evaluation of the area under the curve for the sonographic examination for the receiver operating characteristic curve, the periventricular white matter was 0.742 (95% confidence interval, 0.689-0.790), and it was 0.773 (95% confidence interval, 0.722-0.818) for the subcortical white matter.

CONCLUSIONS

Neonatal brain development, maturation, and myelination can be assessed by strain elastography. These findings should be evaluated with further larger cohorts that could help to prevent neonatal brain damages.

Quantitative Evaluation of Neonatal Brain Elasticity Using Shear Wave Elastography

OBJECTIVES

To demonstrate the feasibility of 2-dimensional brain ultrasound shear wave elastography (SWE) and to define the average elasticity values of the gray and white matter in term neonates.

METHODS

This work was a prospective observational single-center study including 55 healthy term neonates consecutively recruited in the maternity ward between the second and third postnatal days. All were successfully evaluated with a cerebral SWE examination performed with a multifrequency 4-9-MHz transducer. Bilateral sagittal planes of the thalamus and corona radiata were used to measure stiffness using a quantitative SWE method. Several elastograms with 5 to 15 nonoverlapping areas were obtained from the 2 different anatomic locations. The 5 most central measurements were averaged as representative values.

RESULTS

The 55 neonates ranged from 37 to 40 weeks' gestation. The estimated mean velocity values of the thalamus (1.17 m/s; 95% confidence interval, 1.13, 1.22 m/s) and corona radiata (1.60 m/s; 95% confidence interval, 1.57, 1.64 m/s) were statistically different (P < .001). There was no significant influence of laterality, gestational age, cephalic perimeter, sex, length, or type of delivery on the stiffness measurements.

CONCLUSIONS

Brain ultrasound SWE is feasible and allows measurements of neonatal brain elasticity. The elasticity of the thalamus and corona radiata at the frontal white matter in healthy term neonates is different. The knowledge of normal SWE ranges in term neonates allows comparative studies under pathologic conditions.

Differentiation Between Ischemic and Hemorrhagic Strokes - A Pilot Study with Transtemporal Investigation of Brain Parenchyma Elasticity Using Ultrasound Shear Wave Elastography

INTRODUCTION

 Ultrasound shear wave elastography is well established in diagnostics of several parenchymatous organs and is recommended by respective guidelines. So far, research about applications in relevant neurological conditions is missing, especially in adults. Here we aimed to examine the method for the differentiation of ischemic (IS) and hemorrhagic strokes (HS) and cerebral mass effects.

MATERIALS & METHODS

 50 patients with a confirmed diagnosis of HS or IS were enrolled in this prospective study. 2D shear wave elastography was performed on the ipsilateral and the contralateral side with a modified acoustic radiation force impulse (ARFI) technique (ElastPQ mode, Philips). Lesion volumetry was conducted based on computed tomography data for correlation with elastography results.

RESULTS

 Elastography measurements (EM) revealed a highly significant difference between IS and HS with mean values of 1.94 and 5.50 kPa, respectively (p < 0.00 001). Mean values of brain tissue on the non-affected side were almost identical (IS 3.38 (SD = 0.63); HS 3.35 (SD = 0.66); p = 0.91). With a sensitivity of 0.98 and a specificity of 0.99, a cut-off value of 3.52 kPa for discrimination could be calculated. There was a significant correlation of mass effect represented by midline shift and EM values on the contralateral side (Pearson correlation coefficient = 0.68, p < 0.0003).

CONCLUSION

 Ultrasound brain parenchyma elastography seems to be a reliable sonographic method for discriminating between large IS and HS and for detecting and tracking conditions of intracerebral mass effects.

Progress in the Application of Ultrasound Elastography for Brain Diseases

Ultrasound (US) can be used to evaluate the brain structure and nervous system damage. Patients with neurologic symptoms need rapid, noninvasive imaging with high spatial resolution and tissue contrast. Magnetic resonance imaging is currently the most sensitive and specific imaging method for evaluating neuropathologic conditions. This approach does present some challenges, such as the need to transport patients who may be seriously ill to the magnetic resonance imaging suite and the need for patients to remain for a considerable time. Cranial US provides a very valuable imaging method for clinicians, which can make a rapid diagnosis and evaluation without ionizing radiation. The main disadvantage of cranial US is its low sensitivity and specificity for subtle/early lesions. In recent years, with the rapid development of anatomic and functional US technology, the practicability of US diagnosis and intervention has been greatly improved. Ultrasound elastography may have the potential to improve the sensitivity and specificity of various cranial nerve conditions. Ultrasound elastography has received considerable critical attention, and an increasing number of studies have recognized its critical role in evaluating brain diseases. At present, US elastography has been applied to the evaluation of traumatic brain injury, ischemic stroke, intraoperative brain tumors, and hypoxic ischemic encephalopathy. The latest animal experiments and human clinical trial developments in the applications of US elastography for brain diseases are summarized in this review.

Ultrasound Elastography: Review of Techniques, Clinical Application, Technical Limitations, and Safety Considerations in Neonatology

Ultrasound elastography is a relatively new non-invasive diagnostic imaging technology that maps elastic properties and the stiffness of soft tissue. In general, these methods can be classified into strain imaging methods that use internal or external compression stimuli and a shear wave imaging that use ultrasound-generated travelling shear wave stimuli. In this review we describe the basics of ultrasound elastography, discuss differences between various ultrasound elastography techniques, and review advantages, limitations, and the safety of these techniques in clinical practice, especially in neonatology. Furthermore, we review the potential of application of elastography in revealing brain injury and characterizing age dependent differences in preterm and term infants.

Effects of 2D-Shear Wave Elastography on Brain-Derived Neurotrophic Factor (BDNF) in the Brains of Neonatal Mice and Exploration of the Mechanism

BACKGROUND The aim of this study was to explore the effect and duration of 2-dimensional shear wave elastography (2D-SWE) irradiation on the expression of brain-derived neurotrophic factor (BDNF) in the brains of neonatal mice and to preliminarily investigate whether its mechanism is neuronal apoptosis. MATERIAL AND METHODS Neonatal mice (within 48 hours of birth) were subjected to 2D-SWE irradiation of the brain for 10 minutes (group S1), 20 minutes (group S2), and 30 minutes (group S3). The mice were sacrificed immediately after irradiation or 24 hours after irradiation. Brains were collected for real-time polymerase chain reaction (RT-PCR) and western blot experiments to determine the expression of BDNF in each group. TdT-mediated dUTP nick-end labeling (TUNEL) was performed to observe neuronal apoptosis in the brain. RESULTS The results of PCR and western blots from the brains of neonatal mice that were sacrificed immediately after irradiation show that S1, S2, and S3 were significantly different from those in the control group. The PCR and western blot results of brain tissues from neonatal mice sacrificed at 24 hours after irradiation showed that there was no significant difference between the S1, S2, S3, and control groups. The results of TUNEL experiments showed that there was no statistically significant difference in the number of apoptotic neurons between the S1, S2, S3, and control groups. CONCLUSIONS 2D-SWE irradiation of neonatal mice for more than 10 minutes downregulated the expression of BDNF. This effect disappeared within 24 hours after the irradiation, and the 2D-SWE scan seemed not to induce neuronal apoptosis.

Feasibility and reproducibility of shear wave elastography in pediatric cranial ultrasound

BACKGROUND

Head ultrasound (US) is commonly used to evaluate the neonatal brain but may be limited by its lack of sensitivity and specificity. Ultrasound shear wave elastography (SWE) might provide additional information to conventional gray-scale imaging.

OBJECTIVE

To assess whether SWE of brain parenchyma can be (1) successfully performed at a large academic medical center where US technologists perform the majority of examinations and (2) used to detect intracranial pathology.

MATERIALS AND METHODS

Pediatric patients undergoing head ultrasound underwent simultaneous SWE examination. We included normal examinations (n=70) and those with intracranial pathology (n=8) for analysis. We analyzed inter-reader variability and examination success rates and assessed the stiffness of white matter and deep gray nuclei in normal and pathological states across multiple gestational age groups.

RESULTS

Average gestational age of the term, pre-term and extreme pre-term groups were 38.4±1.2 weeks, 29.0±3.7 weeks and 28.3±3.1 weeks, respectively. Overall examination success rate was 79.5%. We observed a decrease in the SWE examination time from the first month (5.9±3.7 min) to the second month (4.1±1.7 min; P=0.01). Forty-one repeat examinations were performed on 14 children by different technologists, with an intraclass correlation coefficient (ICC) of 0.91. Mean stiffness in the periventricular white matter was lower than in the deep gray nuclei in all gestational age groups: term group (1.3 m/s vs. 1.5 m/s, P<0.001), pre-term (1.3 m/s vs. 1.4 m/s P=0.12), and extremely preterm group (1.2 m/s vs. 1.4 m/s, P=0.001). Mean stiffness for the deep gray nuclei differed between the term (1.5±0.3 m/s) and pre-term (1.4±0.2 m/s) groups (P<0.01). No significant differences in white matter stiffness were seen in relation to gestational age. Infants with large intraparenchymal hemorrhage had increased white matter stiffness (1.3±0.1 m/s) and deep gray nuclei stiffness (1.6±0.2 m/s) compared to full-term infants with normal head ultrasounds. These differences approached statistical significance with P=0.09 and P=0.06, respectively.

CONCLUSION

We demonstrated that SWE performed by pediatric sonography technologists is reproducible. We found differences in stiffness between deep gray nuclei and periventricular white matter across multiple age groups.

Feasibility of two-dimensional ultrasound shear wave elastography of human fetal lungs and liver: A pilot study

PURPOSE

The first aim was to evaluate feasibility and reproducibility of 2-dimensional ultrasound (2D) shear wave elastography (SWE) of human fetal lungs and liver between 24 and 34weeks of gestation. The second aim was to model fetal lung-to-liver elastography ratio (LLE ratio) and to assess its variations according to gestational age and maternal administration of corticosteroids.

MATERIAL AND METHODS

2D-SWE examinations were prospectively performed in fetuses of women with an uncomplicated pregnancy (group 1) and fetuses of women with a threatened preterm labor requiring administration of corticosteroids (group 2). Two 2D-SWE examinations were performed at "day 0" and "day 2" in group 1; before and 24hours after a course of corticosteroid in group 2. Three operators performed 2 cycles of 3 measurements on the lung (regions A1, A2, A3) and the liver (regions IV, V, VI). Repeatability and reproducibility of measurements were calculated. The fetal LLE ratio was modeled from the most reproducible regions.

RESULTS

Fifty-five women were enrolled in group 1 and 48 in group 2. For the lung, 8.6% of measurements were considered invalid and 6.9% for the liver. The most reproducible region for the lung was A3 [ICC between 0.70 (95% CI: 0.42-0.85) and 0.78 (95% CI: 0.48-0.90)] and region VI for the liver [ICC between 0.70 (95% CI: 0.40-0.85) and 0.84 (95% CI: 0.60-0.94)]. According to gestational age, a moderate positive linear correlation was found for stiffness values of A3 (R=0.56), V (R=0.46) and VI (R=0.44). LLE ratio values at "day 0" were not different between the two groups but decreased at "day 2" in group 2 (0.2; 95% CI: 0.07-0.34; P<0.001).

CONCLUSION

Quantitative fetal lung and liver stiffness measurements are possible with 2D-SWE with acceptable reproducibility.

The relationship of spleen stiffness value measured by shear wave elastography with age, gender, and spleen size in healthy volunteers

PURPOSE

The aim of this study is to evaluate spleen stiffness values with shear wave elastography (SWE) quantitatively in healthy adults and investigate the relationship of spleen stiffness with age, gender, and spleen size.

METHODS

This study included 65 healthy individuals. Spleen stiffness measurement was obtained with 2 dimensional (2-D) SWE method from the middle portion of spleen and calculated in kilopascals by taking the average of three valid measurements. Longitudinal and transverse spleen sizes were measured. The relationship of spleen stiffness with age, gender, and spleen size was investigated. The association between spleen size and age and gender was also evaluated.

RESULTS

The mean spleen stiffness value was 13.82 ± 2.91 kPa, and the spleen stiffness was not affected by age, gender, or spleen size. Longitudinal spleen size was significantly lower in females than that in males. Moreover, there was a significant negative correlation between longitudinal spleen size and age (r = 0.247, p = 0.048).

CONCLUSION

Spleen stiffness can be quantitatively measured by 2-D SWE, and the spleen stiffness is not affected by age, gender, and spleen size. The values obtained in this study can be used as normal base values in examination of different spleen pathologies.

In vivo time-harmonic ultrasound elastography of the human brain detects acute cerebral stiffness changes induced by intracranial pressure variations

Cerebral stiffness (CS) reflects the biophysical environment in which neurons grow and function. While long-term CS changes can occur in the course of chronic neurological disorders and aging, little is known about acute variations of CS induced by intracranial pressure variations. Current gold standard methods for CS and intracranial pressure such as magnetic resonance elastography and direct pressure recordings are either expensive and slow or invasive. The study objective was to develop a real-time method for in vivo CS measurement and to demonstrate its sensitivity to physiological aging and intracranial pressure variations induced by the Valsalva maneuver in healthy volunteers. We used trans-temporal ultrasound time-harmonic elastography (THE) with external shear-wave stimulation by continuous and superimposed vibrations in the frequency range from 27 to 56 Hz. Multifrequency wave inversion generated maps of shear wave speed (SWS) as a surrogate maker of CS. On average, cerebral SWS was 1.56 ± 0.08 m/s with a tendency to reduce with age (R = -0.76, p < 0.0001) while Valsalva maneuver induced an immediate stiffening of the brain as reflected by a 10.8 ± 2.5% increase (p < 0.0001) in SWS. Our results suggest that CS is tightly linked to intracranial pressure and might be used in the future as non-invasive surrogate marker for intracranial pressure, which otherwise requires invasive measurements.

Characterizing the Neonatal Brain With Ultrasound Elastography

Prematurity is associated with significant neurological injury and impaired neurodevelopment. In neonatology, ultrasonography is frequently used to assess for neurological injury. Ultrasonography allows rapid bedside imaging without radiation. Its limitations include the need for operator experience, lack of quantification, and lower prognostic power when compared with magnetic resonance imaging. Elastography is one of several technical advances used to enhance the diagnostic capability of traditional ultrasound. By detecting differences in tissue stiffness between normal and abnormal tissue, elastography has the potential to add objective and quantitative data to ultrasound imaging. Quantitative values could then be used to help detect injury, correlate outcome to predict prognosis, and guide surgical intervention. Since developmental processes such as myelination and neuropil formation may also influence brain stiffness, elastography may also serve as a unique tool to further delineate developmental differences between preterm and term infants. In this review, we provide a general overview of elastography, its application in neonatal neuroimaging, and possible future directions.