Anatomically constrained tractography of the fetal brain.

Diffusion-weighted Magnetic Resonance Imaging (dMRI) is increasingly used to study the fetal brain in utero. An important computation enabled by dMRI is streamline tractography, which has unique applications such as tract-specific analysis of the brain white matter and structural connectivity assessment. However, due to the low fetal dMRI data quality and the challenging nature of tractography, existing methods tend to produce highly inaccurate results. They generate many false streamlines while failing to reconstruct the streamlines that constitute the major white matter tracts. In this paper, we advocate for anatomically constrained tractography based on an accurate segmentation of the fetal brain tissue directly in the dMRI space. We develop a deep learning method to compute the segmentation automatically. Experiments on independent test data show that this method can accurately segment the fetal brain tissue and drastically improve the tractography results. It enables the reconstruction of highly curved tracts such as optic radiations. Importantly, our method infers the tissue segmentation and streamline propagation direction from a diffusion tensor fit to the dMRI data, making it applicable to routine fetal dMRI scans. The proposed method can facilitate the study of fetal brain white matter tracts with dMRI.

Prenatal molecular diagnosis of pyruvate dehydrogenase complex deficiency enables rapid initiation of ketogenic diet.

Pyruvate dehydrogenase complex deficiency (PDCD) is a mitochondrial disorder of carbohydrate oxidation characterized by lactic acidosis and central nervous system involvement. Knowledge of the affected metabolic pathways and clinical observations suggest that early initiation of the ketogenic diet may ameliorate the metabolic and neurologic course of the disease. We present a case in which first trimester ultrasound identified structural brain abnormalities prompting a prenatal molecular diagnosis of PDCD. Ketogenic diet, thiamine, and N-acetylcysteine were initiated in the perinatal period with good response, including sustained developmental progress. This case highlights the importance of a robust neurometabolic differential diagnosis for prenatally diagnosed structural anomalies and the use of prenatal molecular testing to facilitate rapid, genetically tailored intervention.

How to Perform Fetal MR Imaging.

This article provides the readers with practical guidance on how to perform fetal MR imaging, including technical considerations such as scanner field strength and use of appropriate radiofrequency receive coils, and summarizes the role, strengths, and limitations of the various MR imaging sequences. The authors review the various factors to consider in scan preparation, including study indication, timing, maternal preparation, and the creation of an institutional fetal imaging protocol. Additional factors that go into scan optimization during acquisition including prioritizing maternal comfort and ways to troubleshoot various artifacts that maybe encountered in fetal imaging are discussed.

Fetal Head and Neck Imaging.

Prenatal MRI plays an essential role in the evaluation of the head and neck. This article overviews technical considerations and both isolated and syndromic anomalies of the fetal calvarium, globes and orbits, ears, maxilla, mandible, and neck.

Imaging Assessment of Fetal Cerebrovascular Anomalies.

Four distinct vascular anomalies can be seen to affect the brain on fetal imaging: vein of Galen malformations, non-galenic arteriovenous pial fistulas, dural sinus malformations, and intracranial venous malformations. These congenital disorders affect the arteries and veins of the developing brain and are rarely seen beyond the neonatal stage. The four fetal cerebrovascular anomalies are associated with quite disparate natural histories and prognoses. MRI plays a pivotal role in the evaluation of fetuses with these conditions due to its ability to definitively establish the diagnosis, to detect subtle parenchymal injuries, to delineate the course of abnormal vessels in detail and to some extent the nature of vascular flow, and to identify ischemic, thrombotic, and hemorrhagic complications. Recently, an investigational transurterine embolization procedure targeted at treating fetuses with vein of Galen malformations who are at high risk for neonatal decompensation has emerged as a promising alternative to expectant management and post-natal embolization, with imaging being used to identify suitable patients for the intervention and in pre-procedural planning. This manuscript reviews the essential imaging and clinical features of these four fetal neurovascular anomalies and underscores the practical aspects related to counseling, prognosis, and the multidisciplinary management of these entities.ABBREVIATIONS: ACVRL1= activin A receptor like type 1; b-SSFP=Balanced Steady State Free precession; DSM= Dural Sinus Malformation; Ephrin B4= Ephrin type-B receptor 4; icVM= Intracranial Venous Malformation; ITGB1= Integrin Subunit Beta 1; NOTCH1= Neurogenic locus notch homolog protein 1; PTPN11= Protein Tyrosine Phosphatase Non-Receptor Type 11; RASA1= RAS P21 Protein Activator 1; SSFSE= Single-shot fast spin echo; VOGM=Vein of Galen Malformation.

ACR Appropriateness Criteria® Orbital Imaging and Vision Loss-Child.

Orbital disorders in children consist of varied pathologies affecting the orbits, orbital contents, visual pathway, and innervation of the extraocular or intraocular muscles. The underlying etiology of these disorders may be traumatic or nontraumatic. Presumed location of the lesion along with the additional findings, such as eye pain, swelling, exophthalmos/enophthalmos, erythema, conjunctival vascular dilatation, intraocular pressure, etc, help in determining if imaging is needed, modality of choice, and extent of coverage (orbits and/or head). Occasionally, clinical signs and symptoms may be nonspecific, and, in these cases, diagnostic imaging studies play a key role in depicting the nature and extent of the injury or disease. In this document, various clinical scenarios are discussed by which a child may present with an orbital or vision abnormality. Imaging studies that might be most appropriate (based on the best available evidence or expert consensus) in these clinical scenarios are also discussed. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

CR Appropriateness Criteria® Orbital imaging and vision loss-child

Orbital disorders in children consist of varied pathologies affecting the orbits, orbital contents, visual pathway, and innervation of the extraocular or intraocular muscles. The underlying etiology of these disorders may be traumatic or nontraumatic. Presumed location of the lesion along with the additional findings, such as eye pain, swelling, exophthalmos/enophthalmos, erythema, conjunctival vascular dilatation, intraocular pressure, etc, help in determining if imaging is needed, modality of choice, and extent of coverage (orbits and/or head). Occasionally, clinical signs and symptoms may be nonspecific, and, in these cases, diagnostic imaging studies play a key role in depicting the nature and extent of the injury or disease. In this document, various clinical scenarios are discussed by which a child may present with an orbital or vision abnormality. Imaging studies that might be most appropriate (based on the best available evidence or expert consensus) in these clinical scenarios are also discussed. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Advances in Fetal Brain Imaging.

Over the last 20 years, there have been remarkable developments in fetal brain MR imaging analysis methods. This article delves into the specifics of structural imaging, diffusion imaging, functional MR imaging, and spectroscopy, highlighting the latest advancements in motion correction, fetal brain development atlases, and the challenges and innovations. Furthermore, this article explores the clinical applications of these advanced imaging techniques in comprehending and diagnosing fetal brain development and abnormalities.

A detailed spatio-temporal atlas of the white matter tracts for the fetal brain.

This study presents the construction of a comprehensive spatiotemporal atlas detailing the development of white matter tracts in the fetal brain using diffusion magnetic resonance imaging (dMRI). Our research leverages data collected from fetal MRI scans conducted between 22 and 37 weeks of gestation, capturing the dynamic changes in the brain's microstructure during this critical period. The atlas includes 60 distinct white matter tracts, including commissural, projection, and association fibers. We employed advanced fetal dMRI processing techniques and tractography to map and characterize the developmental trajectories of these tracts. Our findings reveal that the development of these tracts is characterized by complex patterns of fractional anisotropy (FA) and mean diffusivity (MD), reflecting key neurodevelopmental processes such as axonal growth, involution of the radial-glial scaffolding, and synaptic pruning. This atlas can serve as a useful resource for neuroscience research and clinical practice, improving our understanding of the fetal brain and potentially aiding in the early diagnosis of neurodevelopmental disorders. By detailing the normal progression of white matter tract development, the atlas can be used as a benchmark for identifying deviations that may indicate neurological anomalies or predispositions to disorders.

MR insights into fetal brain development: what is normal and what is not.

Fetal brain development is a complex, rapid, and multi-dimensional process that can be documented with MRI. In the second and third trimesters, there are predictable developmental changes that must be recognized and differentiated from disease. This review delves into the key biological processes that drive fetal brain development, highlights normal developmental anatomy, and provides a framework to identify pathology. We will summarize the development of the cerebral hemispheres, sulci and gyri, extra-axial and ventricular cerebrospinal fluid, and corpus callosum and illustrate the most common abnormal findings in the clinical setting.

Preclinical characterization of macrophage-adhering gadolinium micropatches for MRI contrast after traumatic brain injury in pigs.

The choroid plexus (ChP) of the brain plays a central role in orchestrating the recruitment of peripheral leukocytes into the central nervous system (CNS) through the blood-cerebrospinal fluid (BCSF) barrier in pathological conditions, thus offering a unique niche to diagnose CNS disorders. We explored whether magnetic resonance imaging of the ChP could be optimized for mild traumatic brain injury (mTBI). mTBI induces subtle, yet influential, changes in the brain and is currently severely underdiagnosed. We hypothesized that mTBI induces sufficient alterations in the ChP to cause infiltration of circulating leukocytes through the BCSF barrier and developed macrophage-adhering gadolinium [Gd(III)]-loaded anisotropic micropatches (GLAMs), specifically designed to image infiltrating immune cells. GLAMs are hydrogel-based discoidal microparticles that adhere to macrophages without phagocytosis. We present a fabrication process to prepare GLAMs at scale and demonstrate their loading with Gd(III) at high relaxivities, a key indicator of their effectiveness in enhancing image contrast and clarity in medical imaging. In vitro experiments with primary murine and porcine macrophages demonstrated that GLAMs adhere to macrophages also under shear stress and did not affect macrophage viability or functions. Studies in a porcine mTBI model confirmed that intravenously administered macrophage-adhering GLAMs provide a differential signal in the ChP and lateral ventricles at Gd(III) doses 500- to 1000-fold lower than those used in the current clinical standard Gadavist. Under the same mTBI conditions, Gadavist did not offer a differential signal at clinically used doses. Our results suggest that macrophage-adhering GLAMs could facilitate mTBI diagnosis.

Zero-DeepSub: Zero-shot deep subspace reconstruction for rapid multiparametric quantitative MRI using 3D-QALAS.

PURPOSE: To develop and evaluate methods for (1) reconstructing 3D-quantification using an interleaved Look-Locker acquisition sequence with T2 preparation pulse (3D-QALAS) time-series images using a low-rank subspace method, which enables accurate and rapid T1 and T2 mapping, and (2) improving the fidelity of subspace QALAS by combining scan-specific deep-learning-based reconstruction and subspace modeling. THEORY AND METHODS: A low-rank subspace method for 3D-QALAS (i.e., subspace QALAS) and zero-shot deep-learning subspace method (i.e., Zero-DeepSub) were proposed for rapid and high fidelity T1 and T2 mapping and time-resolved imaging using 3D-QALAS. Using an ISMRM/NIST system phantom, the accuracy and reproducibility of the T1 and T2 maps estimated using the proposed methods were evaluated by comparing them with reference techniques. The reconstruction performance of the proposed subspace QALAS using Zero-DeepSub was evaluated in vivo and compared with conventional QALAS at high reduction factors of up to nine-fold. RESULTS: Phantom experiments showed that subspace QALAS had good linearity with respect to the reference methods while reducing biases and improving precision compared to conventional QALAS, especially for T2 maps. Moreover, in vivo results demonstrated that subspace QALAS had better g-factor maps and could reduce voxel blurring, noise, and artifacts compared to conventional QALAS and showed robust performance at up to nine-fold acceleration with Zero-DeepSub, which enabled whole-brain T1, T2, and PD mapping at 1 mm isotropic resolution within 2 min of scan time. CONCLUSION: The proposed subspace QALAS along with Zero-DeepSub enabled high fidelity and rapid whole-brain multiparametric quantification and time-resolved imaging.

A survey of non-sedate practices when acquiring pediatric magnetic resonance imaging examinations.

BACKGROUND: Improving access to magnetic resonance imaging (MRI) in childhood can be facilitated by making it faster and cheaper and reducing need for sedation or general anesthesia (GA) to mitigate motion. Some children achieve diagnostic quality MRI without GA through the use of non- practices fostering their cooperation and/or alleviating anxiety. Employed before and during MRI, these variably educate, distract, and/or desensitize patients to this environment. OBJECTIVE: To assess current utilization of non-sedate practices in pediatric MRI, including variations in practice and outcomes. MATERIALS AND METHODS: A survey-based study was conducted with 1372 surveys emailed to the Society for Pediatric Radiology members in February 2021, inviting one response per institution. RESULTS: Responses from 50 unique institutions in nine countries revealed 49/50 (98%) sites used ≥ 1 non-sedate practice, 48/50 (96%) sites in infants < 6 months, and 11/50 (22%) for children aged 6 months to 3 years. Non-sedate practices per site averaged 4.5 (range 0-10), feed and swaddle used at 47/49 (96%) sites, and child life specialists at 35/49 (71%). Average success rates were moderate (> 50-75%) across all sites and high (> 75-100%) for 20% of sites, varying with specific techniques. Commonest barriers to use were scheduling conflicts and limited knowledge. CONCLUSION: Non-sedate practice utilization in pediatric MRI was near-universal but widely variable across sites, ages, and locales, with room for broader adoption. Although on average non-sedate practice success rates were similar, the range in use and outcomes suggest a need for standardized implementation guidelines, including patient selection and outcome metrics, to optimize utilization and inform educational initiatives.