Volumetric brain analysis in neurosurgery: Part 2. Brain and CSF volumes discriminate neurocognitive outcomes in hydrocephalus

Endoscopic third ventriculostomy (ETV) or ventriculoperitoneal shunt (VPS) for paediatric hydrocephalus due to primary aqueductal stenosis

PURPOSE

The purpose of this study was to compare outcomes of endoscopic third ventriculostomy (ETV) and ventriculoperitoneal shunt (VPS) in children with symptomatic triventricular hydrocephalus due to primary aqueductal stenosis.

METHOD

This is a retrospective analytical study. Patients who underwent either ETV or VPS as the first procedure for hydrocephalus due to primary aqueductal stenosis were included in the study.

RESULT

A total of 89 children were included in the study for analysis. The mean age was 8.4 years. Forty-four (49.4%) had their first surgery as ETV and 45 (50.6%) had their first surgery as VPS. Overall, 34 (38.2%) patients required a second surgery (either ETV or VPS) for persistent or recurrent hydrocephalus. The mean follow-up duration was 832.9 days. The overall complication rate was 13.5%. The mean timing of the second surgery after index surgery was 601.35 days. Factors associated with a second surgery were the presence of complications, high protein in cerebrospinal fluid, the relative change of frontal-occipital horn ratio (FOHR) and Evans' index. The survival of the first surgery was superior in ETV (751.55 days) compared to VPS (454.49 days), p = 0.013. The relative change of fronto-occipital horn index ratio (FOIR) was high in the VPS (mean 7.28%) group compared to the ETV (mean 4.40%), p = 0.001 group.

CONCLUSION

Overall procedural survival was better after ETV than VPS for hydrocephalus due to aqueductal stenosis. VPS causes more reduction in linear indices of ventricles as compared to ETV, however, is not associated with the success or complication of the procedure.

A spatio-temporal atlas of the developing fetal brain with spina bifida aperta

Background: Spina bifida aperta (SBA) is a birth defect associated with severe anatomical changes in the developing fetal brain. Brain magnetic resonance imaging (MRI) atlases are popular tools for studying neuropathology in the brain anatomy, but previous fetal brain MRI atlases have focused on the normal fetal brain. We aimed to develop a spatio-temporal fetal brain MRI atlas for SBA. Methods: We developed a semi-automatic computational method to compute the first spatio-temporal fetal brain MRI atlas for SBA. We used 90 MRIs of fetuses with SBA with gestational ages ranging from 21 to 35 weeks. Isotropic and motion-free 3D reconstructed MRIs were obtained for all the examinations. We propose a protocol for the annotation of anatomical landmarks in brain 3D MRI of fetuses with SBA with the aim of making spatial alignment of abnormal fetal brain MRIs more robust. In addition, we propose a weighted generalized Procrustes method based on the anatomical landmarks for the initialization of the atlas. The proposed weighted generalized Procrustes can handle temporal regularization and missing annotations. After initialization, the atlas is refined iteratively using non-linear image registration based on the image intensity and the anatomical land-marks. A semi-automatic method is used to obtain a parcellation of our fetal brain atlas into eight tissue types: white matter, ventricular system, cerebellum, extra-axial cerebrospinal fluid, cortical gray matter, deep gray matter, brainstem, and corpus callosum. Results: An intra-rater variability analysis suggests that the seven anatomical land-marks are sufficiently reliable. We find that the proposed atlas outperforms a normal fetal brain atlas for the automatic segmentation of brain 3D MRI of fetuses with SBA. Conclusions: We make publicly available a spatio-temporal fetal brain MRI atlas for SBA, available here:  https://doi.org/10.7303/syn25887675. This atlas can support future research on automatic segmentation methods for brain 3D MRI of fetuses with SBA.

Elevated cerebrospinal fluid iron and ferritin associated with early severe ventriculomegaly in preterm posthemorrhagic hydrocephalus

OBJECTIVE

Posthemorrhagic hydrocephalus (PHH) following preterm intraventricular hemorrhage (IVH) is among the most severe sequelae of extreme prematurity and a significant contributor to preterm morbidity and mortality. The authors have previously shown hemoglobin and ferritin to be elevated in the lumbar puncture cerebrospinal fluid (CSF) of neonates with PHH. Herein, they evaluated CSF from serial ventricular taps to determine whether neonates with PHH following severe initial ventriculomegaly had higher initial levels and prolonged clearance of CSF hemoglobin and hemoglobin degradation products compared to those in neonates with PHH following moderate initial ventriculomegaly.

METHODS

In this observational cohort study, CSF samples were obtained from serial ventricular taps in premature neonates with severe IVH and subsequent PHH. CSF hemoglobin, ferritin, total iron, total bilirubin, and total protein were quantified using ELISA. Ventriculomegaly on cranial imaging was assessed using the frontal occipital horn ratio (FOHR) and was categorized as severe (FOHR > 0.6) or moderate (FOHR ≤ 0.6).

RESULTS

Ventricular tap CSF hemoglobin (mean) and ferritin (initial and mean) were higher in neonates with severe versus moderate initial ventriculomegaly. CSF hemoglobin, ferritin, total iron, total bilirubin, and total protein decreased in a nonlinear fashion over the weeks following severe IVH. Significantly higher levels of CSF ferritin and total iron were observed in the early weeks following IVH in neonates with severe initial ventriculomegaly than in those with initial moderate ventriculomegaly.

CONCLUSIONS

Among preterm neonates with PHH following severe IVH, elevated CSF hemoglobin, ferritin, and iron were associated with more severe early ventricular enlargement (FOHR > 0.6 vs ≤ 0.6 at first ventricular tap).

Preoperative risk and postoperative outcome from subdural fluid collections in African infants with postinfectious hydrocephalus

OBJECTIVE

This study investigated the incidence of postoperative subdural collections in a cohort of African infants with postinfectious hydrocephalus. The authors sought to identify preoperative factors associated with increased risk of development of subdural collections and to characterize associations between subdural collections and postoperative outcomes.

METHODS

The study was a post hoc analysis of a randomized controlled trial at a single center in Mbale, Uganda, involving infants (age < 180 days) with postinfectious hydrocephalus randomized to receive either an endoscopic third ventriculostomy plus choroid plexus cauterization or a ventriculoperitoneal shunt. Patients underwent assessment with the Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III; sometimes referred to as BSID-III) and CT scans preoperatively and then at 6, 12, and 24 months postoperatively. Volumes of brain, CSF, and subdural fluid were calculated, and z-scores from the median were determined from normative curves for CSF accumulation and brain growth. Linear and logistic regression models were used to characterize the association between preoperative CSF volume and the postoperative presence and size of subdural collection 6 and 12 months after surgery. Linear regression and smoothing spline ANOVA were used to describe the relationship between subdural fluid volume and cognitive scores. Causal mediation analysis distinguished between the direct and indirect effects of the presence of a subdural collection on cognitive scores.

RESULTS

Subdural collections were more common in shunt-treated patients and those with larger preoperative CSF volumes. Subdural fluid volumes were linearly related to preoperative CSF volumes. In terms of outcomes, the Bayley-III cognitive score was linearly related to subdural fluid volume. The distribution of cognitive scores was significantly different for patients with and those without subdural collections from 11 to 24 months of age. The presence of a subdural collection was associated with lower cognitive scores and smaller brain volume 12 months after surgery. Causal mediation analysis demonstrated evidence supporting both a direct (76%) and indirect (24%) effect (through brain volume) of subdural collections on cognitive scores.

CONCLUSIONS

Larger preoperative CSF volume and shunt surgery were found to be risk factors for postoperative subdural collection. The size and presence of a subdural collection were negatively associated with cognitive outcomes and brain volume 12 months after surgery. These results have suggested that preoperative CSF volumes could be used for risk stratification for treatment decision-making and that future clinical trials of alternative shunt technologies to reduce overdrainage should be considered.

Impact of ventricle size on neuropsychological outcomes in treated pediatric hydrocephalus: an HCRN prospective cohort study

OBJECTIVE

In pediatric hydrocephalus, shunts tend to result in smaller postoperative ventricles compared with those following an endoscopic third ventriculostomy (ETV). The impact of the final treated ventricle size on neuropsychological and quality-of-life outcomes is currently undetermined. Therefore, the authors sought to ascertain whether treated ventricle size is associated with neurocognitive and academic outcomes postoperatively.

METHODS

This prospective cohort study included children aged 5 years and older at the first diagnosis of hydrocephalus at 8 Hydrocephalus Clinical Research Network sites from 2011 to 2015. The treated ventricle size, as measured by the frontal and occipital horn ratio (FOR), was compared with 25 neuropsychological tests 6 months postoperatively after adjusting for age, hydrocephalus etiology, and treatment type (ETV vs shunt). Pre- and posttreatment grade point average (GPA), quality-of-life measures (Hydrocephalus Outcome Questionnaire [HOQ]), and a truncated preoperative neuropsychological battery were also compared with the FOR.

RESULTS

Overall, 60 children were included with a mean age of 10.8 years; 17% had ≥ 1 comorbidity. Etiologies for hydrocephalus were midbrain lesions (37%), aqueductal stenosis (22%), posterior fossa tumors (13%), and supratentorial tumors (12%). ETV (78%) was more commonly used than shunting (22%). Of the 25 neuropsychological tests, including full-scale IQ (q = 0.77), 23 tests showed no univariable association with postoperative ventricle size. Verbal learning delayed recall (p = 0.006, q = 0.118) and visual spatial judgment (p = 0.006, q = 0.118) were negatively associated with larger ventricles and remained significant after multivariate adjustment for age, etiology, and procedure type. However, neither delayed verbal learning (p = 0.40) nor visual spatial judgment (p = 0.22) was associated with ventricle size change with surgery. No associations were found between postoperative ventricle size and either GPA or the HOQ.

CONCLUSIONS

Minimal associations were found between the treated ventricle size and neuropsychological, academic, or quality-of-life outcomes for pediatric patients in this comprehensive, multicenter study that encompassed heterogeneous hydrocephalus etiologies.

A novel model of acquired hydrocephalus for evaluation of neurosurgical treatments

Background

Many animal models have been used to study the pathophysiology of hydrocephalus; most of these have been rodent models whose lissencephalic cerebral cortex may not respond to ventriculomegaly in the same way as gyrencephalic species and whose size is not amenable to evaluation of clinically relevant neurosurgical treatments. Fewer models of hydrocephalus in gyrencephalic species have been used; thus, we have expanded upon a porcine model of hydrocephalus in juvenile pigs and used it to explore surgical treatment methods.

Methods

Acquired hydrocephalus was induced in 33–41-day old pigs by percutaneous intracisternal injections of kaolin (n = 17). Controls consisted of sham saline-injected (n = 6) and intact (n = 4) animals. Magnetic resonance imaging (MRI) was employed to evaluate ventriculomegaly at 11–42 days post-kaolin and to plan the surgical implantation of ventriculoperitoneal shunts at 14–38-days post-kaolin. Behavioral and neurological status were assessed.

Results

Bilateral ventriculomegaly occurred post-induction in all regions of the cerebral ventricles, with prominent CSF flow voids in the third ventricle, foramina of Monro, and cerebral aqueduct. Kaolin deposits formed a solid cast in the basal cisterns but the cisterna magna was patent. In 17 untreated hydrocephalic animals. Mean total ventricular volume was 8898 ± 5917 SD mm³ at 11–43 days of age, which was significantly larger than the baseline values of 2251 ± 194 SD mm³ for 6 sham controls aged 45–55 days, (p < 0.001). Past the post-induction recovery period, untreated pigs were asymptomatic despite exhibiting mild-moderate ventriculomegaly. Three out of 4 shunted animals showed a reduction in ventricular volume after 20–30 days of treatment, however some developed ataxia and lethargy, from putative shunt malfunction.

Conclusions

Kaolin induction of acquired hydrocephalus in juvenile pigs produced an in vivo model that is highly translational, allowing systematic studies of the pathophysiology and clinical treatment of hydrocephalus.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12987-021-00281-0.

Hydrocephalus in Low and Middle-Income Countries - Progress and Challenges

Hydrocephalus remains one of the most commonly treated neurosurgical conditions worldwide. Caring for patients with hydrocephalus requires infrastructure and political support and initiative; these are often difficult to obtain in low- and middle-income countries (LMICs). Some innovations that have arisen in LMICs have traveled up the financial gradient to high-income countries, such as the combination of endoscopic third ventriculostomy with choroid plexus coagulation to manage hydrocephalus. The development of neuro-endoscopy has played a major role in managing hydrocephalus worldwide; however, LMICs still face specific challenges, such as limited access to shunt hardware, a disproportionately high incidence of post-infectious hydrocephalus, unique microbiological spectra, and often poor access to follow-up care and neuroimaging. This has received increased attention since the Lancet Commission on Global Surgery. The goal of improving access to quality neurosurgical care through various initiatives in LMICs will be discussed in this manuscript. The need for neurosurgeons continues to grow in LMICs, where better access to neurosurgical care, adequate neurosurgical training and political support, and patient education are needed to improve the quality of life for patients with common neurosurgical conditions. Despite these challenges, treating hydrocephalus remains a worthwhile endeavor for many patients.

Endoscopic third ventriculostomy and choroid plexus cauterization (ETV/CPC) for hydrocephalus of infancy: a technical review

In the twenty-first century, choroid plexus cauterization (CPC) in combination with endoscopic third ventriculostomy (ETV) has emerged as an effective treatment for some infants with hydrocephalus, leading to the favourable condition of 'shunt independence'. Herein we provide a narrative technical review considering the indications, procedural aspects, morbidity and its avoidance, postoperative care and follow-up. The CP has been the target of hydrocephalus treatment for more than a century. Early eminent neurosurgeons including Dandy, Putnam and Scarff performed CPC achieving generally poor results, and so the procedure fell out of favour. In recent years, the addition of CPC to ETV was one of the reasons greater ETV success rates were observed in Africa, compared to developed nations, and its popularity worldwide has since increased. Initial results indicate that when ETV/CPC is performed successfully, shunt independence is more likely than when ETV is undertaken alone. CPC is commonly performed using a flexible endoscope via septostomy and aims to maximally cauterize the CP. Success is more likely in infants aged >1 month, those with hydrocephalus secondary to myelomeningocele and aqueductal obstruction and those with >90% cauterized CP. Failure is more likely in those with post-haemorrhagic hydrocephalus of prematurity (PHHP), particularly those <1 month of corrected age and those with prepontine scarring. High-quality evidence comparing the efficacy of ETV/CPC with shunting is emerging, with data from ongoing and future trials offering additional promise to enhance our understanding of the true utility of ETV/CPC.

Multi-omic analysis elucidates the genetic basis of hydrocephalus

We conducted PrediXcan analysis of hydrocephalus risk in ten neurological tissues and whole blood. Decreased expression of MAEL in the brain was significantly associated (Bonferroni-adjusted p < 0.05) with hydrocephalus. PrediXcan analysis of brain imaging and genomics data in the independent UK Biobank (N = 8,428) revealed that MAEL expression in the frontal cortex is associated with white matter and total brain volumes. Among the top differentially expressed genes in brain, we observed a significant enrichment for gene-level associations with these structural phenotypes, suggesting an effect on disease risk through regulation of brain structure and integrity. We found additional support for these genes through analysis of the choroid plexus transcriptome of a murine model of hydrocephalus. Finally, differential protein expression analysis in patient cerebrospinal fluid recapitulated disease-associated expression changes in neurological tissues, but not in whole blood. Our findings provide convergent evidence highlighting the importance of tissue-specific pathways and mechanisms in the pathophysiology of hydrocephalus.

Hale et al. present an integrated omics approach to characterize the genetic basis of hydrocephalus. They reveal tissue-specific genetic associations and enrichment of genes associated with human brain structure phenotypes. Validation of hydrocephalus-associated genes in mouse choroid plexus and human cerebrospinal fluid supports polygenic contributions to hydrocephalus risk.

Semantic segmentation of cerebrospinal fluid and brain volume with a convolutional neural network in pediatric hydrocephalus-transfer learning from existing algorithms

Background

For the segmentation of medical imaging data, a multitude of precise but very specific algorithms exist. In previous studies, we investigated the possibility of segmenting MRI data to determine cerebrospinal fluid and brain volume using a classical machine learning algorithm. It demonstrated good clinical usability and a very accurate correlation of the volumes to the single area determination in a reproducible axial layer. This study aims to investigate whether these established segmentation algorithms can be transferred to new, more generalizable deep learning algorithms employing an extended transfer learning procedure and whether medically meaningful segmentation is possible.

Methods

Ninety-five routinely performed true FISP MRI sequences were retrospectively analyzed in 43 patients with pediatric hydrocephalus. Using a freely available and clinically established segmentation algorithm based on a hidden Markov random field model, four classes of segmentation (brain, cerebrospinal fluid (CSF), background, and tissue) were generated. Fifty-nine randomly selected data sets (10,432 slices) were used as a training data set. Images were augmented for contrast, brightness, and random left/right and X/Y translation. A convolutional neural network (CNN) for semantic image segmentation composed of an encoder and corresponding decoder subnetwork was set up. The network was pre-initialized with layers and weights from a pre-trained VGG 16 model. Following the network was trained with the labeled image data set. A validation data set of 18 scans (3289 slices) was used to monitor the performance as the deep CNN trained. The classification results were tested on 18 randomly allocated labeled data sets (3319 slices) and on a T2-weighted BrainWeb data set with known ground truth.

Results

The segmentation of clinical test data provided reliable results (global accuracy 0.90, Dice coefficient 0.86), while the CNN segmentation of data from the BrainWeb data set showed comparable results (global accuracy 0.89, Dice coefficient 0.84). The segmentation of the BrainWeb data set with the classical FAST algorithm produced consistent findings (global accuracy 0.90, Dice coefficient 0.87). Likewise, the area development of brain and CSF in the long-term clinical course of three patients was presented.

Conclusion

Using the presented methods, we showed that conventional segmentation algorithms can be transferred to new advances in deep learning with comparable accuracy, generating a large number of training data sets with relatively little effort. A clinically meaningful segmentation possibility was demonstrated.

The impact of cerebral anomalies on cognitive outcome in patients with spina bifida: A systematic review

BACKGROUND

Spina bifida is the most common congenital birth defect affecting the central nervous system. Given the frequent association of cerebral anomalies, spina bifida is not a single developmental abnormality of the central nervous system. Patients with spina bifida typically perform below average on cognitive tasks. It has been hypothesized that associated cerebral anomalies as well negatively affect cognition in spina bifida patients.

OBJECTIVE

This study aims to review the impact of cerebral anomalies on cognitive outcome in patients with spina bifida.

METHODS

A systematic search of multiple databases, including Pubmed, Embase, Web of Science and The Cochrane Central Register of Controlled Trials, was performed. All relevant primary research articles were included. All included articles were methodologically evaluated using a critical appraisal checklist.

RESULTS

In total 27 articles were included in this systematic review. A significant impact of different cerebral anomalies on cognition was found. More specifically, hydrocephalus, Chiari malformation type II and anomalies of the corpus callosum, central executive network, default mode network, cortical thickness and gyrification, fornix, grey matter volume and total brain volume were found to have a significant impact on cognitive outcome. The presence of a CSF shunt was also negatively associated with cognition. The results on Chiari malformation type II decompression and CSF shunt complications are inconsistent.

CONCLUSION

Associated cerebral anomalies have a significant impact on cognitive outcome in patients with spina bifida. The interrelatedness of the different cerebral anomalies makes it difficult to distinguish their individual impact on cognition.

Cranial and ventricular size following shunting or endoscopic third ventriculostomy (ETV) in infants with aqueductal stenosis: further insights from the International Infant Hydrocephalus Study (IIHS)

PURPOSE

The craniometrics of head circumference (HC) and ventricular size are part of the clinical assessment of infants with hydrocephalus and are often utilized in conjunction with other clinical and radiological parameters to determine the success of treatment. We aimed to assess the effect of endoscopic third ventriculostomy (ETV) and shunting on craniometric measurements during the follow-up of a cohort of infants with symptomatic triventricular hydrocephalus secondary to aqueductal stenosis.

METHODS

We performed a post hoc analysis of data from the International Infant Hydrocephalus Study (IIHS)-a prospective, multicenter study of infants (< 24 months old) with hydrocephalus from aqueductal stenosis who were treated with either an ETV or shunt. During various stages of a 5-year follow-up period, the following craniometrics were measured: HC, HC centile, HC z-score, and frontal-occipital horn ratio (FOR). Data were compared in an analysis of covariance, adjusting for baseline variables including age at surgery and sex.

RESULTS

Of 158 enrolled patients, 115 underwent an ETV, while 43 received a shunt. Both procedures led to improvements in the mean HC centile position and z-score, a trend which continued until the 5-year assessment point. A similar trend was noted for FOR which was measured at 12 months and 3 years following initial treatment. Although the values were consistently higher for ETV compared with shunt, the differences in HC value, centile, and z-score were not significant. ETV was associated with a significantly higher FOR compared with shunting at 12 months (0.52 vs 0.44; p = 0.002) and 3 years (0.46 vs 0.38; p = 0.03) of follow-up.

CONCLUSION

ETV and shunting led to improvements in HC centile, z-score, and FOR measurements during long-term follow-up of infants with hydrocephalus secondary to aqueductal stenosis. Head size did not significantly differ between the treatment groups during follow-up, however ventricle size was greater in those undergoing ETV when measured at 1 and 3 years following treatment.

Planar single plane area determination is a viable substitute for total volumetry of CSF and brain in childhood hydrocephalus

BACKGROUND

In the treatment of childhood hydrocephalus, 3D volumetry seems to have many advantages over classical planar index measurements for dedicated monitoring of changes in cerebrospinal fluid and brain volume. Nevertheless, this method requires extensive technical effort and access to the complete three-dimensional data set. Against this background, we evaluated the possibility of planar area determination in a single plane and the correlation to volumetry.

METHODS

138 routinely performed true FISP MRI sequences (1 mm isovoxel) were analyzed retrospectively in 68 patients with pediatric hydrocephalus. After preprocessing, the 3D-data sets were skull stripped to estimate the inner skull volume. A 2-class segmentation into different tissue types (brain matter and CSF) was performed, and the volumes of CSF (VCSF) and brain matter (VBrain) were calculated. A plane at the level of the foramina of Monro was manually identified in the ac-pc oriented data. In this plane, the areas of brain (ABrain) and CSF (ACSF) in cm² were calculated and used for further correlation analysis.

RESULTS

Mean VCSF was 340 ± 145 cm³ and VBrain 1173 ± 254 cm³. In the selected plane, ACSF was 26 ± 14 cm², and ABrain was 107 ± 25 cm². There was a very strong positive correlation between both ACSF and VCSF (r = 0.895) and between ABrain and VBrain (r = 0.846). The prediction equations for VBrain and VCSF were highly significant.

CONCLUSION

Planar area determination of brain and CSF correlates excellently with both VCSF and VBrain. Thus, areas can serve as a surrogate marker for total brain and CSF volumes for a quantitated objective tracking of changes during treatment of childhood hydrocephalus.

The CURE Protocol: evaluation and external validation of a new public health strategy for treating paediatric hydrocephalus in low-resource settings

Introduction

Managing paediatric hydrocephalus with shunt placement is especially risky in resource-limited settings due to risks of infection and delayed life-threatening shunt obstruction. This study evaluated a new evidence-based treatment algorithm to reduce shunt-dependence in this context.

Methods

A prospective cohort design was used. The CURE Protocol employs preoperative and intraoperative data to choose between endoscopic treatment and shunt placement. Data were prospectively collected for 730 children in Uganda (managed by local neurosurgeons highly experienced in the protocol) and, for external validation, 96 children in Nigeria (managed by a local neurosurgeon trained in the protocol).

Results

The age distribution was similar between Uganda and Nigeria, but there were more cases of postinfectious hydrocephalus in Uganda (64.2% vs 26.0%, p<0.001). Initial treatment of hydrocephalus was similar at both centres and included either a shunt at first operation or endoscopic management without a shunt. The Nigerian cohort had a higher failure rate for endoscopic cases (adjusted HR 2.5 (95% CI 1.6 to 4.0), p<0.001), but not for shunt cases (adjusted HR 1.3 (0.5 to 3.0), p=0.6). Despite the difference in endoscopic failure rates, a similar proportion of the entire cohort was successfully treated without need for shunt at 6 months (55.2% in Nigeria vs 53.4% in Uganda, p=0.74).

Conclusion

Use of the CURE Protocol in two centres with different populations and surgeon experience yielded similar 6-month results, with over half of all children remaining shunt-free. Where feasible, this could represent a better public health strategy in low-resource settings than primary shunt placement.

Automatic volumetry of cerebrospinal fluid and brain volume in severe paediatric hydrocephalus, implementation and clinical course after intervention

BACKGROUND

In childhood hydrocephalus, both the amount of cerebrospinal fluid and the brain volume are relevant for the prognosis of the development and for therapy monitoring. Since classical planar measurements of ventricular size are subject to strong limitations, imprecise and neglect brain volume, 3D volumetry is most desirable. We used and evaluated the robust segmentation algorithms of the freely available FSL-toolbox in paediatric hydrocephalus patients before and after specific therapy.

METHODS

Retrospectively 76 pre- and postoperative high-resolution T2-weighted MRI sequences (true FISP, 1 mm isovoxel) were analyzed in 38 patients with paediatric hydrocephalus (mean 4.4 ± 5.1 years) who underwent surgical treatment (ventriculo-peritoneal (VP) shunt n = 22, endoscopic third ventriculostomy (ETV) n = 16). After preprocessing, the 3D-datasets were skull stripped to estimate the inner skull surface. Following, a 2 class segmentation into different tissue types (brain matter and CSF) was performed. The volumes of CSF and brain were calculated.

RESULTS

The method could be implemented in an automated fashion in all 76 MRIs. In the VP shunt cohort, the amount of CSF (p < 0.001) decreased. Consecutively brain volume increased significantly (p < 0.001). Following ETV, CSF volume (p = 0.019) decreased significantly (p = 0.012) although the reduction was less pronounced than after shunt implantation. Brain volume expanded (p = 0.02).

CONCLUSION

A reliable automated segmentation of CSF and brain could be performed with the implemented algorithm. The method was able to track changes after therapy and detected significant differences in CSF and brain volumes after shunting and after ETV.

Fetal surgery for spina bifida

The two-hit hypothesis of neural injury in the wake of open neural tube defects suggests an opportunity for preservation of function and potential reversibility of early morphological changes in the fetus diagnosed with myelomeningocele. The Management of Myelomeningocele Study (MOMS) demonstrated reduced need for shunting and improved neurological function in patients treated in utero relative to postnatally, thereby offering level 1 evidence supporting fetal repair. Subsequent studies have offered additional information about urological, orthopedic, radiological, and maternal factors surrounding fetal repair. The quest for robust long-term neurocognitive and motor function data is underway and poised to shape the future of fetal repair. In addition, technical innovations such as fetoscopic surgery aim to minimize maternal morbidity while conferring the beneficial effects observed with open intrauterine intervention.

International Infant Hydrocephalus Study (IIHS): 5-year health outcome results of a prospective, multicenter comparison of endoscopic third ventriculostomy (ETV) and shunt for infant hydrocephalus

INTRODUCTION

One of the most important unanswered questions in pediatric hydrocephalus is determining whether treatment with endoscopic third ventriculostomy (ETV) versus shunt results in improved health status and quality of life (QOL). To answer this, the International Infant Hydrocephalus Study (IIHS) was started in 2005 as a prospective, multicenter study to compare ETV and shunt in infants (< 24 months old) with symptomatic triventricular hydrocephalus from aqueductal stenosis. Herein, we present the 5-year primary outcome results.

METHODS

IIHS utilized a prospective comprehensive cohort design, in which patients received ETV or shunt, based on either randomization or parental preference. For this analysis, we pooled the randomized arm and the parental preference arm, analyzing them together. At 5 years of age, children were assessed with the Health Utilities Index Mark 2 (HUI-2) (primary outcome) and the Hydrocephalus Outcome Questionnaire (HOQ), a measure of QOL. Results were compared in an analysis of covariance, adjusting for baseline variables including age at surgery and baseline development status.

RESULTS

From a total of 158 patients who met eligibility criteria, complete 5-year outcomes were available on 78 (19 treated initially with shunt, 61 treated initially with ETV), assessed at a mean age of 62.1 months (SD 6.3). The mean 5-year HUI-2 utility score was 0.90 (SD 0.19) for ETV and 0.94 (SD 0.10) for shunt (p = 0.21). The mean 5-year HOQ overall score was 0.81 (SD 0.15) for ETV and 0.85 (SD 0.12) for shunt (p = 0.42). Similarly, there were no significant differences noted between 5-year HOQ subscores (cognitive, social-emotional, physical) or developmental measures at 1, 2, and 3 years.

CONCLUSIONS

This is the first prospective direct comparison of long-term outcomes of ETV and shunt for infant hydrocephalus. These results suggest that overall health status and quality of life in this cohort of infants treated for aqueductal stenosis are high, with no significant difference between those treated initially with ETV or shunt.

TRIAL REGISTRATION

NCT00652470.

Neurosurgery in East Africa: Innovations

In the last 10 years, considerable work has been done to promote and improve neurosurgical care in East Africa with the development of national training programs, expansion of hospitals and creation of new institutions, and the foundation of epidemiologic and cost-effectiveness research. Many of the results have been accomplished through collaboration with partners from abroad. This article is the third in a series of articles that seek to provide readers with an understanding of the development of neurosurgery in East Africa (Foundations), the challenges that arise in providing neurosurgical care in developing countries (Challenges), and an overview of traditional and novel approaches to overcoming these challenges to improve healthcare in the region (Innovations). In this article, we describe the ongoing programs active in East Africa and their current priorities, and we outline lessons learned and what is required to create self-sustained neurosurgical service.

Normative human brain volume growth

OBJECTIVE While there is a long history of interest in measuring brain growth, as of yet there is no definitive model for normative human brain volume growth. The goal of this study was to analyze a variety of candidate models for such growth and select the model that provides the most statistically applicable fit. The authors sought to optimize clinically applicable growth charts that would facilitate improved treatment and predictive management for conditions such as hydrocephalus. METHODS The Weibull, two-term power law, West ontogenic, and Gompertz models were chosen as potential models. Normative brain volume data were compiled from the NIH MRI repository, and the data were fit using a nonlinear least squares regression algorithm. Appropriate statistical measures were analyzed for each model, and the best model was characterized with prediction bound curves to provide percentile estimates for clinical use. RESULTS Each model curve fit and the corresponding statistics were presented and analyzed. The Weibull fit had the best statistical results for both males and females, while the two-term power law generated the worst scores. The statistical measures and goodness of fit parameters for each model were provided to assure reproducibility. CONCLUSIONS The authors identified the Weibull model as the most effective growth curve fit for both males and females. Clinically usable growth charts were developed and provided to facilitate further clinical study of brain volume growth in conditions such as hydrocephalus. The authors note that the homogenous population from which the normative MRI data were compiled limits the study. Gaining a better understanding of the dynamics that underlie childhood brain growth would yield more predictive growth curves and improved neurosurgical management of hydrocephalus.

Automatically measuring brain ventricular volume within PACS using artificial intelligence

The picture archiving and communications system (PACS) is currently the standard platform to manage medical images but lacks analytical capabilities. Staying within PACS, the authors have developed an automatic method to retrieve the medical data and access it at a voxel level, decrypted and uncompressed that allows analytical capabilities while not perturbing the system’s daily operation. Additionally, the strategy is secure and vendor independent. Cerebral ventricular volume is important for the diagnosis and treatment of many neurological disorders. A significant change in ventricular volume is readily recognized, but subtle changes, especially over longer periods of time, may be difficult to discern. Clinical imaging protocols and parameters are often varied making it difficult to use a general solution with standard segmentation techniques. Presented is a segmentation strategy based on an algorithm that uses four features extracted from the medical images to create a statistical estimator capable of determining ventricular volume. When compared with manual segmentations, the correlation was 94% and holds promise for even better accuracy by incorporating the unlimited data available. The volume of any segmentable structure can be accurately determined utilizing the machine learning strategy presented and runs fully automatically within the PACS.

Comparing neurodevelopmental outcomes at 30 months by presence of hydrocephalus and shunt status among children enrolled in the MOMS trial

PURPOSE

To evaluate for differences in neurodevelopmental outcomes at 30 months of age for children enrolled in the Management of Myelomeningocele Study (MOMS) based on the presence of hydrocephalus and cerebral shunts.

METHODS

Children with no hydrocephalus (N= 27), children with shunted hydrocephalus (N= 108), and children with unshunted hydrocephalus (N= 36) were compared at 30 months of age on the Bayley II Mental and Psychomotor Indices, the Peabody Developmental Motor Scales-2 and the Preschool Language Scale, 4th edition. Generalized linear models were used to adjust for factors significantly different between the groups at baseline. Additional analyses were conducted to evaluate the impact of the severity of hydrocephalus.

RESULTS

In unadjusted comparisons, statistically significant differences were noted between the three groups on the Peabody Gross Motor Quotient and thus the Total Motor Quotient. After adjustment, no statistically significant differences were identified. In subanalyses, children with more severe hydrocephalus fared worse on the Peabody Fine Motor Quotient (median 88 versus 94, p= 0.005), the Total Motor Quotient (median 70 versus 73, p= 0.02) and both Preschool Language Scale subtests (auditory comprehension: median 93 versus 104, p= 0.02 and expressive communication: median 95 versus 104.5, p= 0.01) and thus the total score (median 92 versus 105, p= 0.004). These results remained significant in the multivariable adjusted model.

CONCLUSION

No neurodevelopmental differences were noted with children enrolled in MOMS across the three hydrocephalus/shunt groups, although severity of hydrocephalus was associated with poorer outcomes.

Endoscopic Treatment versus Shunting for Infant Hydrocephalus in Uganda

BACKGROUND

Postinfectious hydrocephalus in infants is a major health problem in sub-Saharan Africa. The conventional treatment is ventriculoperitoneal shunting, but surgeons are usually not immediately available to revise shunts when they fail. Endoscopic third ventriculostomy with choroid plexus cauterization (ETV-CPC) is an alternative treatment that is less subject to late failure but is also less likely than shunting to result in a reduction in ventricular size that might facilitate better brain growth and cognitive outcomes.

METHODS

We conducted a randomized trial to evaluate cognitive outcomes after ETV-CPC versus ventriculoperitoneal shunting in Ugandan infants with postinfectious hydrocephalus. The primary outcome was the Bayley Scales of Infant Development, Third Edition (BSID-3), cognitive scaled score 12 months after surgery (scores range from 1 to 19, with higher scores indicating better performance). The secondary outcomes were BSID-3 motor and language scores, treatment failure (defined as treatment-related death or the need for repeat surgery), and brain volume measured on computed tomography.

RESULTS

A total of 100 infants were enrolled; 51 were randomly assigned to undergo ETV-CPC, and 49 were assigned to undergo ventriculoperitoneal shunting. The median BSID-3 cognitive scores at 12 months did not differ significantly between the treatment groups (a score of 4 for ETV-CPC and 2 for ventriculoperitoneal shunting; Hodges-Lehmann estimated difference, 0; 95% confidence interval [CI], -2 to 0; P=0.35). There was no significant difference between the ETV-CPC group and the ventriculoperitoneal-shunt group in BSID-3 motor or language scores, rates of treatment failure (35% and 24%, respectively; hazard ratio, 0.7; 95% CI, 0.3 to 1.5; P=0.24), or brain volume (z score, -2.4 and -2.1, respectively; estimated difference, 0.3; 95% CI, -0.3 to 1.0; P=0.12).

CONCLUSIONS

This single-center study involving Ugandan infants with postinfectious hydrocephalus showed no significant difference between endoscopic ETV-CPC and ventriculoperitoneal shunting with regard to cognitive outcomes at 12 months. (Funded by the National Institutes of Health; ClinicalTrials.gov number, NCT01936272 .).

Learning Based Segmentation of CT Brain Images: Application to Postoperative Hydrocephalic Scans

OBJECTIVE

Hydrocephalus is a medical condition in which there is an abnormal accumulation of cerebrospinal fluid (CSF) in the brain. Segmentation of brain imagery into brain tissue and CSF [before and after surgery, i.e., preoperative (pre-op) versus postoperative (post-op)] plays a crucial role in evaluating surgical treatment. Segmentation of pre-op images is often a relatively straightforward problem and has been well researched. However, segmenting post-op computational tomographic (CT) scans becomes more challenging due to distorted anatomy and subdural hematoma collections pressing on the brain. Most intensity- and feature-based segmentation methods fail to separate subdurals from brain and CSF as subdural geometry varies greatly across different patients and their intensity varies with time. We combat this problem by a learning approach that treats segmentation as supervised classification at the pixel level, i.e., a training set of CT scans with labeled pixel identities is employed.

METHODS

Our contributions include: 1) a dictionary learning framework that learns class (segment) specific dictionaries that can efficiently represent test samples from the same class while poorly represent corresponding samples from other classes; 2) quantification of associated computation and memory footprint; and 3) a customized training and test procedure for segmenting post-op hydrocephalic CT images.

RESULTS

Experiments performed on infant CT brain images acquired from the CURE Children's Hospital of Uganda reveal the success of our method against the state-of-the-art alternatives. We also demonstrate that the proposed algorithm is computationally less burdensome and exhibits a graceful degradation against a number of training samples, enhancing its deployment potential.

Cerebrospinal fluid volume does not have etiological role in the incidence of positional skull deformities

BACKGROUND

Positional skull deformities (PSD) are becoming a daily health concern for craniofacial surgeons. Several reports have indicated that cerebrospinal fluid (CSF) space increases on computed tomography (CT) scans of infants suffering from PSD, suggesting a potential causal link. Here, we describe a semi-automatic method to estimate total brain and CSF volumes quantitatively. We tested the potential correlation between total CSF volume and the occurrence of PSD.

METHODS

A single-center retrospective study was carried out using 79 CT scans of PSD and 60 CT scans of control subjects. The endocranium was segmented automatically using a three-dimensional deformable surface model, and the brain was segmented using a semi-automatic threshold-based method. Total CSF volume was estimated based on the difference between endocranial and brain volumes.

RESULTS

Automatic segmentation of the endocranium was possible in 75 CT scans. Semi-automatic brain and CSF volume evaluations were performed in 40 CT scans of infants with PSD (18 = occipital plagiocephaly, 11 = fronto-occipital plagiocephaly, and 11 = posterior brachycephaly) and in six control CT scans. Endocranial and total CSF volumes were not significantly different between patients with PSD and controls. The occipital plagiocephaly group had an enlarged brain volume compared with that in patients in the other groups.

CONCLUSIONS

Total CSF volume did not change in infants with PSD, and the results do not support a role for volume changes in CSF in the etiology of PSD. Macrocephaly in patients with occipital plagiocephaly may be a specific etiological factor compared with that in other PSDs.

An improved finite element modeling of the cerebrospinal fluid layer in the head impact analysis

The finite element (FE) method has been widely used to investigate the mechanism of traumatic brain injuries (TBIs), because it is technically difficult to quantify the responses of the brain tissues to the impact in experiments. One of technical challenges to build a FE model of a human head is the modeling of the cerebrospinal fluid (CSF) of the brain. In the current study, we propose to use membrane elements to construct the CSF layer. Using the proposed approach, we demonstrate that a head model can be built by using existing meshes available in commercial databases, without using any advanced meshing software tool, and with the sole use of native functions of the FE package Abaqus. The calculated time histories of the intracranial pressures at frontal, posterior fossa, parietal, and occipital positions agree well with the experimental data and the simulations in the literature, indicating that the physical effects of the CSF layer have been accounted for in the proposed modeling approach. The proposed modeling approach would be useful for bioengineers to solve practical problems.

Hydrocephalus in children

Imaging of hydrocephalus in utero, in infants and children is critically dependent on an understanding of the pathophysiology and treatment options for this condition in this age spectrum. For this reason, this chapter deals not only with the imaging modalities used to study hydrocephalus and how they are applied but also reviews key aspects of the pathophysiology and treatment of hydrocephalus in children. Imaging techniques to establish the diagnosis of chronic hydrocephalus fall into two categories: (1) tracer-type techniques that require an injection and observation of the transit of an injected substance through the ventricular system or subarachnoid space and (2) cross-sectional imaging, which allows for direct visualization of a point of obstruction within the ventricular system or subarachnoid space. For cross-sectional imaging, both magnetic resonance imaging (MRI) and computed tomography can be used, but MRI is usually preferred. Nomenclature has obscured the description of imaging findings in hydrocephalus. We suggest that most hydrocephalus is obstructive and propose to designate ventriculomegaly, the condition in which the ventricles are large on imaging, but there is no true obstruction to the outflow of cerebrospinal fluid.

Role of radiological parameters in predicting overall shunt outcome after ventriculoperitoneal shunt insertion in pediatric patients with obstructive hydrocephalus

OBJECTIVE

Despite significant advances in the medical field and shunt technology, shunt malfunction remains a nightmare of pediatric neurosurgeons. In this setting, the ability to preoperatively predict the probability of shunt malfunction is quite compelling. The authors have compared the preoperative radiological findings in obstructive hydrocephalus and the subsequent clinical course of the patient to determine any association with overall shunt outcome.

METHODS

This retrospective study included all pediatric patients (age < 18 years) who had undergone ventriculoperitoneal shunt insertion for obstructive hydrocephalus. Linear measurements were taken from pre- and postoperative CT or MRI studies to calculate different indices and ratios including Evans' index, frontal horn index (FHI), occipital horn index (OHI), frontooccipital horn ratio (FOHR), and frontooccipital horn index ratio (FOIR). Other morphological features such as bi- or triventriculomegaly, right-left ventricular symmetry, and periventricular lucency (PVL) were also noted. The primary clinical outcomes that were reviewed included the need for shunt revision, time interval to first shunt revision, frequency of shunt revisions, and revision-free survival.

RESULTS

A total of 121 patients were eligible for the analysis. Nearly half of the patients (47.9%) required shunt revision. The presence of PVL was associated with lower revision rates than those in others (39.4% vs 58.2%, p = 0.03). None of the preoperative radiological indices or ratios showed any correlation with shunt revision. Nearly half of the patients with shunt revision required early revision (< 90 days of primary surgery). The reduction in the FOHR was high in patients who required early shunt revision (20.16% in patients with early shunt revision vs 6.4% in patients with late shunt revision, p = 0.009). Nearly half of the patients (48.3%) requiring shunt revision ultimately needed more than one revision procedure. Greater occipital horn dilation on preoperative images was associated with a lower frequency of shunt revision, as dictated by a high OHI and a low FOIR in patients with a single shunt revision as compared with those in patients who required multiple shunt revisions (p = 0.029 and 0.009, respectively). The mean follow-up was 49.9 months. Age was a significant factor affecting shunt revision–free survival. Patients younger than 6 months of age had significantly less revision-free survival than the patients older than 6 months (median survival of 10.1 vs 94.1 months, p = 0.004).

CONCLUSIONS

Preoperative radiological linear indices and ratios do not predict the likelihood of subsequent shunt malfunction. However, patients who required early shunt revision tended to have greater reductions in ventricular volumes on postoperative images. Therefore a greater reduction in ventricular volume is not actually desirable, and a ventricular volume high enough to reduce intracranial pressure is instead to be aimed at for long-term shunt compliance.

Efficacy and safety of endoscopic third ventriculostomy and choroid plexus cauterization for infantile hydrocephalus: a systematic review and meta-analysis

PURPOSE

Endoscopic third ventriculostomy/choroid plexus cauterization (ETV/CPC) has gained popularity in its treatment of infantile hydrocephalus over the past decade. In this manuscript, we perform a systematic review and meta-analysis to determine the efficacy and safety of ETV/CPC, and to compare the procedural outcomes between North American and sub-Saharan African cohorts.

METHODS

Systematic review was performed using four electronic databases and bibliographies of relevant articles, with no language or date restrictions. Cohort studies of participants undergoing ETV/CPC that reported outcome were included using MOOSE guidelines. The outcome was time to repeat CSF diversion or death. Forest plots were created for pooled mean and its 95 % CI of outcome and morbidity.

RESULTS

Of 78 citations, 11 retrospective reviews (with 524 total participants) were eligible. Efficacy was achieved in 63 % participants at follow-up periods between 6 months and 8 years. Adverse events and mortality was reported in 3.7 and 0.4 % of participants, respectively. Publication bias was detected with respect to efficacy and morbidity of the procedure. A large discrepancy in success was identified between ETV/CPC in six studies from sub-Saharan Africa (71 %), compared to three studies from North America (49 %).

CONCLUSIONS

The reported success of ETV/CPC for infantile hydrocephalus is higher in sub-Saharan Africa than developed nations. Large long-term prospective multi-center observational studies addressing patient-important outcomes are required to further evaluate the efficacy and safety of this re-emerging procedure.

Ventricular volume and neurocognitive outcome after endoscopic third ventriculostomy: is shunting a better option? A review

BACKGROUND

Shunts are generally associated with a smaller post-treatment ventricular size in comparison to endoscopic third ventriculostomy (ETV).

METHODS

To determine whether such a difference in ventricular size has neurocognitive implications, we reviewed the current literature pertaining to the (1) neurocognitive sequelae of hydrocephalus, (2) neurocognitive outcome after ETV, (3) extent of reversal of neurocognitive changes associated with hydrocephalus after shunting, and (4) data on correlation between post-treatment ventricular volume and neurocognitive outcome after ETV.

RESULTS

Collectively, the results of the available studies should call into question the correlation between the residual postoperative ventricular volume and neurocognitive outcome.

CONCLUSION

The available literature is so far in support of ETV as a valid and effective treatment modality in hydrocephalic patients. No sufficient evidence is available to justify resorting to shunting on the premise that it is associated with a better neurocognitive outcome.

Hydrocephalus in aqueductal stenosis--a retrospective outcome analysis and proposal of subtype classification

Treatment of aqueductal stenosis (AQS) has undergone several paradigm shifts during the past decades. Currently, endoscopic ventriculostomy (ETV) is recommended as treatment of choice. Several authors have addressed the issue of variable ETV success rates depending on age and pathogenetic factors. However, success rates have usually been defined as "ETV non-failure." The aim of the study was a retrospective analysis of radiological and neurological treatment response after ETV or VP-shunting (VPS) in age-dependent subtypes of AQS.

PATIENTS AND METHODS

Eighty patients (median age 12.0 years, range 0-79 years) have been treated for MRI-proven aqueductal stenosis. Neurological treatment success was defined by neurological improvement and, in childhood, head circumference. Radiological response was measured as Evan's index in follow-up MRI. Initial signs and symptoms, type of surgery, and complications were analyzed.

RESULTS

Four types of AQS have been defined with distinct age ranges and symptomatology: congenital type I (n = 24), chronic progressive (tectal tumor-like) type II (n = 23), acute type III (n = 10), and adult chronic (normal-pressure hydrocephalus-like) type IV (n = 23). Retrospective analysis of neurological and radiological outcome suggested that congenital type I (<1 years of age) may be more successfully treated with VPS than with ETV (81 vs. 50 %). Treatment of chronic juvenile type II (age 2-15) by ETV 19 % compared to 57 % after VP-shunt, but similar neurological improvement (>80 %). There has been no influence of persistent ventriculomegaly in type II after ETV in contrast to VPS therapy for neurological outcome. Adult acute type III (age > 15 years) responded excellent to ETV. Chronic type IV (iNPH-like) patients (age > 21) responded neurologically in 70 % after ETV and VPS, but radiological response was low (5 %).

CONCLUSION

AQS can be divided into four distinct age groups and types in regards of clinical course and symptomatology. Depending on the AQS type, ETV cannot be unequivocally recommended. Congenital type I AQS may have a better neurological outcome with VP-shunt whereas acute type III offers excellent ETV results. Chronic progressive type II still requires prospective investigation of long-term ETV outcome, especially when ventriculomegaly persists. Late chronic type IV seems to result in similar outcome after VP-shunt and ETV.

Hydrocephalus in children

Hydrocephalus is a common disorder of cerebral spinal fluid (CSF) physiology resulting in abnormal expansion of the cerebral ventricles. Infants commonly present with progressive macrocephaly whereas children older than 2 years generally present with signs and symptoms of intracranial hypertension. The classic understanding of hydrocephalus as the result of obstruction to bulk flow of CSF is evolving to models that incorporate dysfunctional cerebral pulsations, brain compliance, and newly characterised water-transport mechanisms. Hydrocephalus has many causes. Congenital hydrocephalus, most commonly involving aqueduct stenosis, has been linked to genes that regulate brain growth and development. Hydrocephalus can also be acquired, mostly from pathological processes that affect ventricular outflow, subarachnoid space function, or cerebral venous compliance. Treatment options include shunt and endoscopic approaches, which should be individualised to the child. The long-term outcome for children that have received treatment for hydrocephalus varies. Advances in brain imaging, technology, and understanding of the pathophysiology should ultimately lead to improved treatment of the disorder.

Design of a mobile, homogeneous, and efficient electromagnet with a large field of view for neonatal low-field MRI

OBJECTIVE

In this work, a prototype of an effective electromagnet with a field-of-view (FoV) of 140 mm for neonatal head imaging is presented. The efficient implementation succeeded by exploiting the use of steel plates as a housing system. We achieved a compromise between large sample volumes, high homogeneity, high B0 field, low power consumption, light weight, simple fabrication, and conserved mobility without the necessity of a dedicated water cooling system.

MATERIALS AND METHODS

The entire magnetic resonance imaging (MRI) system (electromagnet, gradient system, transmit/receive coil, control system) is introduced and its unique features discussed. Furthermore, simulations using a numerical optimization algorithm for magnet and gradient system are presented.

RESULTS

Functionality and quality of this low-field scanner operating at 23 mT (generated with 500 W) is illustrated using spin-echo imaging (in-plane resolution 1.6 mm × 1.6 mm, slice thickness 5 mm, and signal-to-noise ratio (SNR) of 23 with a acquisition time of 29 min). B0 field-mapping measurements are presented to characterize the homogeneity of the magnet, and the B0 field limitations of 80 mT of the system are fully discussed.

CONCLUSION

The cryogen-free system presented here demonstrates that this electromagnet with a ferromagnetic housing can be optimized for MRI with an enhanced and homogeneous magnetic field. It offers an alternative to prepolarized MRI designs in both readout field strength and power use. There are multiple indications for the clinical medical application of such low-field devices.

Pre-Adult MRI of Brain Cancer and Neurological Injury: Multivariate Analyses

Brain cancer and neurological injuries, such as stroke, are life-threatening conditions for which further research is needed to overcome the many challenges associated with providing optimal patient care. Multivariate analysis (MVA) is a class of pattern recognition technique involving the processing of data that contains multiple measurements per sample. MVA can be used to address a wide variety of neuroimaging challenges, including identifying variables associated with patient outcomes; understanding an injury's etiology, development, and progression; creating diagnostic tests; assisting in treatment monitoring; and more. Compared to adults, imaging of the developing brain has attracted less attention from MVA researchers, however, remarkable MVA growth has occurred in recent years. This paper presents the results of a systematic review of the literature focusing on MVA technologies applied to brain injury and cancer in neurological fetal, neonatal, and pediatric magnetic resonance imaging (MRI). With a wide variety of MRI modalities providing physiologically meaningful biomarkers and new biomarker measurements constantly under development, MVA techniques hold enormous potential toward combining available measurements toward improving basic research and the creation of technologies that contribute to improving patient care.

Multivariate analyses applied to fetal, neonatal and pediatric MRI of neurodevelopmental disorders

Multivariate analysis (MVA) is a class of statistical and pattern recognition methods that involve the processing of data that contains multiple measurements per sample. MVA can be used to address a wide variety of medical neuroimaging-related challenges including identifying variables associated with a measure of clinical importance (i.e. patient outcome), creating diagnostic tests, assisting in characterizing developmental disorders, understanding disease etiology, development and progression, assisting in treatment monitoring and much more. Compared to adults, imaging of developing immature brains has attracted less attention from MVA researchers. However, remarkable MVA research growth has occurred in recent years. This paper presents the results of a systematic review of the literature focusing on MVA technologies applied to neurodevelopmental disorders in fetal, neonatal and pediatric magnetic resonance imaging (MRI) of the brain. The goal of this manuscript is to provide a concise review of the state of the scientific literature on studies employing brain MRI and MVA in a pre-adult population. Neurological developmental disorders addressed in the MVA research contained in this review include autism spectrum disorder, attention deficit hyperactivity disorder, epilepsy, schizophrenia and more. While the results of this review demonstrate considerable interest from the scientific community in applications of MVA technologies in pediatric/neonatal/fetal brain MRI, the field is still young and considerable research growth remains ahead of us.

Validated automatic brain extraction of head CT images

BACKGROUND

X-ray computed tomography (CT) imaging of the brain is commonly used in diagnostic settings. Although CT scans are primarily used in clinical practice, they are increasingly used in research. A fundamental processing step in brain imaging research is brain extraction - the process of separating the brain tissue from all other tissues. Methods for brain extraction have either been 1) validated but not fully automated, or 2) fully automated and informally proposed, but never formally validated.

AIM

To systematically analyze and validate the performance of FSL's brain extraction tool (BET) on head CT images of patients with intracranial hemorrhage. This was done by comparing the manual gold standard with the results of several versions of automatic brain extraction and by estimating the reliability of automated segmentation of longitudinal scans. The effects of the choice of BET parameters and data smoothing is studied and reported.

METHODS

All images were thresholded using a 0-100 Hounsfield unit (HU) range. In one variant of the pipeline, data were smoothed using a 3-dimensional Gaussian kernel (σ=1mm(3)) and re-thresholded to 0-100HU; in the other, data were not smoothed. BET was applied using 1 of 3 fractional intensity (FI) thresholds: 0.01, 0.1, or 0.35 and any holes in the brain mask were filled. For validation against a manual segmentation, 36 images from patients with intracranial hemorrhage were selected from 19 different centers from the MISTIE (Minimally Invasive Surgery plus recombinant-tissue plasminogen activator for Intracerebral Evacuation) stroke trial. Intracranial masks of the brain were manually created by one expert CT reader. The resulting brain tissue masks were quantitatively compared to the manual segmentations using sensitivity, specificity, accuracy, and the Dice Similarity Index (DSI). Brain extraction performance across smoothing and FI thresholds was compared using the Wilcoxon signed-rank test. The intracranial volume (ICV) of each scan was estimated by multiplying the number of voxels in the brain mask by the dimensions of each voxel for that scan. From this, we calculated the ICV ratio comparing manual and automated segmentation: ICVautomated/ICVmanual. To estimate the performance in a large number of scans, brain masks were generated from the 6 BET pipelines for 1095 longitudinal scans from 129 patients. Failure rates were estimated from visual inspection. ICV of each scan was estimated and an intraclass correlation (ICC) was estimated using a one-way ANOVA.

RESULTS

Smoothing images improves brain extraction results using BET for all measures except specificity (all p<0.01, uncorrected), irrespective of the FI threshold. Using an FI of 0.01 or 0.1 performed better than 0.35. Thus, all reported results refer only to smoothed data using an FI of 0.01 or 0.1. Using an FI of 0.01 had a higher median sensitivity (0.9901) than an FI of 0.1 (0.9884, median difference: 0.0014, p<0.001), accuracy (0.9971 vs. 0.9971; median difference: 0.0001, p<0.001), and DSI (0.9895 vs. 0.9894; median difference: 0.0004, p<0.001) and lower specificity (0.9981 vs. 0.9982; median difference: -0.0001, p<0.001). These measures are all very high indicating that a range of FI values may produce visually indistinguishable brain extractions. Using smoothed data and an FI of 0.01, the mean (SD) ICV ratio was 1.002 (0.008); the mean being close to 1 indicates the ICV estimates are similar for automated and manual segmentation. In the 1095 longitudinal scans, this pipeline had a low failure rate (5.2%) and the ICC estimate was high (0.929, 95% CI: 0.91, 0.945) for successfully extracted brains.

CONCLUSION

BET performs well at brain extraction on thresholded, 1mm(3) smoothed CT images with an FI of 0.01 or 0.1. Smoothing before applying BET is an important step not previously discussed in the literature. Analysis code is provided.