Three-dimensional (3D) ultrasound--a useful imaging technique in the assessment of neonatal brain

Pediatric encephalic ultrasonography: the essentials

Nowadays, cranial ultrasonography (US) of the newborn represents the first imaging method in brain damage study and its possible outcomes. This exam is performed using the natural fontanelles, especially the anterior one. It is fast, non-invasive and does not produce any side effect. Ultrasonographic examination is usually performed in cases of prematurity, especially in children with birth weight less than 1500 g, because important informations about the possible presence of pathologies such as cerebral hemorrhage and hypoxic-ischemic encephalopathy are given. This approach can be useful also in the study of pre- and post-natal infections, for example, type II Herpes Simplex virus or Cytomegalovirus infections, or pointing out vascular malformations such as vein of Galen aneurysm. Although less important than methods such as computed tomography (CT) and magnetic resonance imaging (MRI) in the evaluation of trauma and tumors, ultrasound can provide useful informations or be used in first instance in the suspicion of a brain mass.

Time efficiency and diagnostic agreement of 2-D versus 3-D ultrasound acquisition of the neonatal brain

The purpose of this study was to compare acquisition time efficiency and diagnostic agreement of neonatal brain ultrasound (US) scans obtained with a 3-D volume US acquisition protocol and the conventional 2-D acquisition protocol. Ninety-one consecutive premature neonatal brain ultrasound scans were prospectively performed on 59 neonates with the conventional 2-D acquisition protocol. Immediately after the 2-D study, a coronal 3-D ultrasound volume was acquired and later reconstructed into axial and sagittal planes. All 59 neonates were imaged in the neonatal intensive care unit to rule out intracranial hemorrhage. Total time for 2-D and 3-D acquisition protocols was recorded, and a two-tailed t-test was used to determine if study durations differed significantly. One pediatric neuroradiologist reviewed the reformatted 3-D images, tomographic ultrasound images. Results were compared with the clinical interpretation of the 2-D conventional study. The mean scanning time for the 2-D US acquisition protocol was 10.56 min (standard deviation [SD] = 7.11), and that for the 3-D volume US acquisition protocol was 1.48 min (SD = 0.59) (p ≤ 0.001). Inter-observer agreement revealed k values of 0.84 for hydrocephalus, 0.80 for germinal matrix hemorrhage/intraventricular hemorrhage, 0.74 for periventricular leukomalacia and 0.91 for subdural collection, hence near-perfect to substantial agreement between imaging protocols. There was a significant decrease in acquisition time for the 3-D volume ultrasound acquisition protocol compared with the conventional 2-D US protocol (p = <0.001), without compromising the diagnostic quality compared with a conventional 2-D US imaging protocol.

Editorial review: pediatric 3D ultrasound

Three-dimensional ultrasound is an established diagnostic imaging technique in many specialties. However, in neonates, infants and children three-dimensional ultrasound still is underutilized, partially due to time constraints for post-processing and restricted availability, of devices as well as dedicated pediatric transducers. Also reimbursement issues still need to be addressed. This editorial review presents more or less established pediatric three-dimensional ultrasound applications with proven diagnostic benefit as well as potential future applications of three-dimensional/four-dimensional ultrasound in infants and children, aiming at enhancing research and promoting practical use of three-dimensional ultrasound in relevant pediatric conditions. Particularly, applications in neonatal neurosonography, ultrasound of the urogenital tract as well as some other small part and miscellaneous queries are highlighted. Additional other potential and future indications are discussed briefly, also mentioning restrictions and potential future developments. In summary, three-dimensional ultrasound holds some potential to widen sonographic diagnostic capabilities throughout childhood and hopefully will be increasingly investigated and introduced into clinical practice provided respective equipment and pediatric three-dimensional/four-dimensional ultrasound transducers become available.

Presurgical language mapping in children with epilepsy: clinical usefulness of functional magnetic resonance imaging for the planning of cortical stimulation

PURPOSE

Presurgical language mapping in dominant hemisphere epilepsy to evaluate the risk of postoperative deficit is particularly difficult in children. Extraoperative invasive cortical stimulation can show some areas critical to language, but not all of them, due to scarce sampling, poor cooperation, cortical immaturity, or network reorganization, whereas functional magnetic resonance imaging (fMRI) displays entire networks involved in, but not necessarily critical to, language. In a homogeneous series of children with epilepsy, we compared the contributions of language fMRI and depth electrode stimulations to optimize language mapping.

METHODS

Eight children (7.5-15.5 years) with left frontal or temporal epilepsy underwent language fMRI and language stimulation with depth electrodes as part of their comprehensive presurgical workup. fMRI data collected during sentence generation were analyzed using statistical parametric mapping (SPM2) (false discovery rate [FDR] p < 0.05). Bipolar stimulations were performed during language production tasks. By coregistering fMRI and postimplantation computed tomography (CT) images, we were able to directly compare the cortical areas identified by both investigations.

KEY FINDINGS

fMRI during sentence generation robustly showed activation in the whole perisylvian regions with little reorganization (left hemisphere dominant in 7). Of the 184 electrode contacts tested for language, only 8 were positive (language disruption) in three of the seven patients with periictal language impairment and left language dominance. All of the positive contacts colocalized with an fMRI activated cluster, that is, fMRI did not miss any region critical to language (sensitivity = 100%). However, 54 of the 176 negative contacts were within activated clusters (low specificity).

SIGNIFICANCE

In children with epilepsy, the sensitivity of fMRI during sentence generation allows for the detection of all critical regions displayed by cortical stimulation within the large perisylvian language network, but with a low specificity. It is, therefore, useful to optimize the placement of intracranial electrodes when language mapping is necessary. Systematic planning of the electrode placement according to language fMRI maps should increase the yield of extraoperative cortical stimulation, which appears rather low in children when compared to adults.

Potential role of 3DUS in infants and children

The objective of this review is to discuss basic technical aspects as well as potential pediatric applications of three-dimensional ultrasound (3DUS). Different 3DUS-techniques are already commercially available. Most commonly, a transducer-integrated motor drives a scan-head to acquire a volumetric dataset, which is then reconstructed and viewed using various post-processing techniques. It has been proved feasible to apply 3DUS with pediatric transducers in typical pediatric investigations. Based on our own experiences and on review of the literature, 3DUS can be successfully used in infants and children for brain, spine, cardiac, urinary tract (particularly assessment of hydronephrosis, and virtual cystoscopy), and female genital (e.g., for assessment of uterine malformations) US, and for various other applications, particularly in small parts. Power Doppler data can be integrated, allowing 3DUS-angiography. Thus, 3DUS promises to become a useful adjunct for imaging children, particularly as it enhances ultrasound by offering additional, previously inaccessible planes, rendering options and surface assessments. 3DUS should be increasingly exploited, thus hopefully helping reduce the need for more invasive or burdening (e.g., ionizing radiation) investigations in children.

Three-dimensional ultrasound imaging

This review is about the development of three-dimensional (3D) ultrasonic medical imaging, how it works, and where its future lies. It assumes knowledge of two-dimensional (2D) ultrasound, which is covered elsewhere in this issue. The three main ways in which 3D ultrasound may be acquired are described: the mechanically swept 3D probe, the 2D transducer array that can acquire intrinsically 3D data, and the freehand 3D ultrasound. This provides an appreciation of the constraints implicit in each of these approaches together with their strengths and weaknesses. Then some of the techniques that are used for processing the 3D data and the way this can lead to information of clinical value are discussed. A table is provided to show the range of clinical applications reported in the literature. Finally, the discussion relating to the technology and its clinical applications to explain why 3D ultrasound has been relatively slow to be adopted in routine clinics is drawn together and the issues that will govern its development in the future explored.

Continuity between Fetal and Neonatal Neurobehavior

As the development of the brain is unique and continuing process throughout the gestation and after birth, it is expected that there is also continuity of fetal and neonatal movements which are the best functional indicator of developmental processes of the brain. Understanding the relation between fetal and infant behavior and developmental processes of the brain in different periods of gestation may make achievable the distinction between normal and abnormal brain development. Epidemiological studies revealed that many neurologically impaired infants belong to low risk population, which means that they seemed to be developmentally normal as fetuses and as infants, while later childhood neurological disability was diagnosed. Which methods of neurological assessment are available for that purpose? Prenatally we have not many possibilities for neurological assessment, while postnatally the repertoire of diagnostic possibilities is increasing. Among the postnatally available methods for neurological assessment, the most important are: clinical neurological assessment, neuroimaging methods, assessment of general movements (GMs) and combinations. Postnatal neurological assessment is probably easier to perform than prenatal, by using a simple and suitable for everyday work screening clinical test with good reliability, specificity and sensitivity.

There is a possibility for the early and simple neurological assessment of the term and preterm newborns with the aim to detect associated risks and anticipate long-term outcome of the infant, and to establish a possible causative link between pregnancy course and neurodevelopmental outcome. The evaluation of infant's developmental optimality should be assessed in order to investigate whether the infant is neurologically normal or damaged. Neurological assessment at term by Amiel-Tison (ATNAT) is taking into account neurological maturation exploring so called lower subcortical system developing earlier from the reticular formation, vestibular nuclei and tectum, and upper cortical system developing from the corticospinal pathways.

Conventional acquisition neuroimaging techniques together with modern diffusion neuroimaging techniques can identify typical patterns of brain injury, even in the early course of the disease. However, even though highly suggestive, these patterns cannot be considered as pathognomonic. Nevertheless neuroimaging methods alone are not sufficient to predict the neurological outcome in neonates from highrisk population.

Prechtl stated that spontaneous motility, as the expression of spontaneous neural activity, is a marker of brain proper or disturbed function. The observation of unstimulated fetus or infant which is the result of spontaneous behavior without sensory stimulation is the best method to assess its central nervous system capacity. All endogenously generated movement patterns from un-stimulated central nervous system could be observed as early as from the 7-8 weeks of postmenstrual age, with developing a reach repertoire of movements within the next two or three weeks, continuing to be present for 5 to 6 months postnatally. This remarkable fact of the continuity of endogenously generated activity from prenatal to postnatal life is the great opportunity to find out those high-risk fetuses and infants in whom development of neurological impairment is emerging. The most important among those movements are GMs involving the whole body in a variable sequence of arm, leg, neck and trunk movements, with gradual beginning and the end. They wax and wane in intensity, force and speed being fluent and elegant with the impression of complexity and variability. Assessment of GMs in high-risk newborns has significantly higher predictive value for later neurological development than neurological examination. Kurjak and co-workers conducted a study by 4D ultrasound and confirmed earlier findings made by 2D ultrasonography, that there is behavioral pattern continuity from prenatal to postnatal life. Assessment of neonatal behavior is a better method for early detection of cerebral palsy than neurological examination alone.

Are we approaching the era when there will be applicable neurological test for fetus and assessment of neonate will be just the continuation? This is still not easy question to answer, because even postnatally there are several neurological methods of evaluation, while in utero we are dealing with more complicated situation and less mature brain. Could neonatal assessment of neurologically impaired fetuses bring some new insights into their prenatal neurological status is still unclear and to be investigated. New scoring system for prenatal neurological assessment of the fetus proposed by Kurjak et al will give some new possibilities to detect fetuses at high neurological risk, although it is obvious that dynamic and complicated process of functional CNS development is not easy to investigate.

The aim of this review is to present continuity of the functional central nervous system assessment from prenatal to postnatal life.

How useful is 3D and 4D ultrasound in perinatal medicine?

AIM

The purpose of this paper is to review and analyze the published literature on the use of three-dimensional (3DUS) and four-dimensional (4DUS) ultrasound in perinatal medicine.

METHODS

We systematically searched Medline through PubMED (January 2000-January 2006), including EMBASE/Excerpta Medica database as well as the Cochrane Database of Systematic Reviews. The search terms used to identify clinical application of 3DUS and 4DUS studies in perinatal medicine were technical development, special features, and recommendation for fetal imaging, research on 3DUS or 4DUS, and the usage of invasive 3DUS or 4DUS procedures. The reference bibliographies of relevant books were also manually searched for supplementary citations. Inclusion criteria were as follows: (1) studies related to the use of 3DUS or 4DUS in perinatal medicine; (2) full text were available in English; (3) publication format of original scientific articles, case reports, editorials or literature reviews and chapters in the books.

RESULTS

Five hundred and seventy-five articles were identified, and among those, 438 were relevant to this review.

CONCLUSIONS

3DUS and 4DUS provided additional information for the diagnosis of facial anomalies, evaluation of neural tube defects, and skeletal malformations. Additional research is needed to determine the clinical utility of 3DUS and 4DUS for the diagnosis of congenital heart disease, central nervous system (CNS) anomalies and detection of fetal neurodevelopmental impairment assessed by abnormal behavior in high-risk fetuses.

The role of different imaging modalities: is MRI a conditio sine qua non for ETV?

OBJECTIVE

To describe the different imaging modalities used for the diagnosis and classification of hydrocephalus, their role in defining the optimal treatment of hydrocephalus and to define the optimal preoperative diagnostics for endoscopic third ventriculocisternostomy (ETV).

METHODS

An overview on available imaging modalities for hydrocephalus will be given and their pros and cons discussed. In addition, different aspects of the treatment of hydrocephalus by shunts and by ETV will be highlighted.

DISCUSSION

The role of the technical aspects of performing an ETV, the role of the surgeon's philosophy, the role of the urgency of the procedure, and the role of informed consent on the requirements for the imaging of the hydrocephalus will be discussed.

CONCLUSION

The authors conclude that MRI is a conditio sine qua non for ETV in elective surgical cases.

Dynamic motion analysis of fetuses with central nervous system disorders by cine magnetic resonance imaging using fast imaging employing steady-state acquisition and parallel imaging: a preliminary result

OBJECT

The authors present a novel cine magnetic resonance (MR) imaging, two-dimensional (2D) fast imaging employing steady-state acquisition (FIESTA) technique with parallel imaging. It achieves temporal resolution at less than half a second as well as high spatial resolution cine imaging free of motion artifacts for evaluating the dynamic motion of fetuses in utero. The information obtained is used to predict postnatal outcome.

METHODS

Twenty-five fetuses with anomalies were studied. Ultrasonography demonstrated severe abnormalities in five of the fetuses; the other 20 fetuses constituted a control group. The cine fetal MR imaging demonstrated fetal head, neck, trunk, extremity, and finger as well as swallowing motions. Imaging findings were evaluated and compared in fetuses with major central nervous system (CNS) anomalies in five cases and minor CNS, non-CNS, or no anomalies in 20 cases. Normal motility was observed in the latter group. For fetuses in the former group, those with abnormal motility failed to survive after delivery, whereas those with normal motility survived with functioning preserved. The power deposition of radiofrequency, presented as specific absorption rate (SAR), was calculated. The SAR of FIESTA was approximately 13 times lower than that of conventional MR imaging of fetuses obtained using single-shot fast spin echo sequences.

CONCLUSIONS

The following conclusions are drawn: 1) Fetal motion is no longer a limitation for prenatal imaging after the implementation of parallel imaging with 2D FIESTA, 2) Cine MR imaging illustrates fetal motion in utero with high clinical reliability, 3) For cases involving major CNS anomalies, cine MR imaging provides information on extremity motility in fetuses and serves as a prognostic indicator of postnatal outcome, and 4) The cine MR used to observe fetal activity is technically 2D and conceptually three-dimensional. It provides four-dimensional information for making proper and timely obstetrical and/or postnatal management decisions.

Three-dimensional ultrasonography of hydrocephalus

We examined two infants with hydrocephalus using three-dimensional (3-D) ultrasonography. One infant had congenital hydrocephalus with a ventriculoperitoneal shunt. On 2-D ultrasonography, the shunt tube was shown only as "a point." However, on 3-D ultrasonography, we could easily see the three-dimensional position of the shunt tube, which was situated in the lateral ventricle. The other patient had hydrocephalus associated with an arachnoid cyst. We could understand the complex shape of the cyst and distinguish it from the third ventricle using 3-D ultrasonography. Thus, 3-D ultrasonography imaging is more useful than 2-D ultrasonography imaging in evaluating hydrocephalus.

Hydronephrotic kidney: pediatric three-dimensional US for relative renal size assessment--initial experience

PURPOSE

To prospectively evaluate accuracy of three-dimensional (3D) ultrasonography (US) for assessment of relative renal size in infants and children with hydronephrosis.

MATERIALS AND METHODS

Informed consent was obtained from parents and also from children who were older than 8 years. Study was approved by ethics committee. Two-dimensional (2D) US, 3D US, and scintigraphy were performed in 40 patients with hydronephrosis (age range, neonate to 16 years; seven girls, 33 boys) without acute renal disease. Twenty patients also underwent magnetic resonance (MR) urography. US and MR urography were performed by one experienced pediatric radiologist; 3D US and MR urographic volume calculations were performed by specifically trained radiologists. Three-dimensional US was performed with integrated 3D volume probes or external system based on electromagnetic positioning devices. At 2D US, kidney volume was calculated with application of ellipsoid equation. At MR urography and 3D US, real renal parenchymal volume was calculated with subtraction of dilated collecting system. Split renal function was assessed with static renal scintigraphy. Three-dimensional US results were graded with respect to image quality and compared with results of 2D US, scintigraphy, and MR urography by using mean difference percentage and standard deviation of the difference. All investigations were performed with blinding. Inter- and intraobserver variability were calculated with coefficient of variation.

RESULTS

In 76 of 80 kidneys, 3D US image of diagnostic quality was obtained. Three-dimensional US volume measurements compared well with MR urographic measurements (mean difference, -2.5% +/- 7.8 [standard deviation] vs 25.8% +/- 32.2 for 2D US) and with scintigraphically assessed split renal function (mean difference, 1.2% +/- 9.2 vs 15.9% +/- 43.8 for 2D US). Intra- and interobserver variability were +/-6.4% and +/-9.9%, respectively.

CONCLUSION

Initial experience with renal 3D US indicates that it is an accurate method for assessment of renal parenchymal volume and relative renal size, provided there is no acute renal disease.

Three-dimensional ultrasonography of monkey brain

Three-dimensional (3D) ultrasonography is new technology based on automatic volume acquisition of ultrasound images, and computer-aided image reconstruction. In the present study, we used a commercially available 3D ultrasonographic instrument for electrophysiological and neuroanatomical experiments in the macaque monkey. 3D reconstruction for multiplanar analysis and surface rendering were useful to observe the microelectrode or microinjection pipette in the cerebral cortex or deep brain structure. The present results indicate that the 3D ultrasonography for monkey brain is a more powerful tool for experiments in vivo than conventional two-dimensional (2D) ultrasonography.

[Advances in pediatric sonography]

Advances in the field of ultrasound technology and ultrasound contrast media over the past few years have also brought major improvements to pediatric sonography. Accordingly, contrast-enhanced voiding urosonography has become a valuable alternative in the diagnosis of vesicoureteral reflux. It is possible to achieve significant reduction in radiation exposure replacing the conventional radiologic methods used for reflux diagnosis with contrast-enhanced ultrasound. Through the introduction of harmonic imaging, an ultrasound scanning modality with high spatial and contrast resolution has become available. The modality was initially propagated as one to be applied in difficult-to-scan adults. However, initial experiences in pediatric applications are demonstrating the significant improvement it can bring in the ultrasound image quality, for example, in intestinal ultrasound. A further development is three-dimensional [3D] imaging using ultrasound. 3D-ultrasound not only offers an improvement in diagnosis but also in the acceptance of ultrasound in interdisciplinary work and teaching. The first applications of 3D-ultrasound in pediatrics are focusing on brain ultrasound and volume measurement of the kidneys.