Does the Addition of a "Black Bone" Sequence to a Fast Multisequence Trauma MR Protocol Allow MRI to Replace CT after Traumatic Brain Injury in Children?

MR Cranial Bone Imaging: Evaluation of Both Motion-Corrected and Automated Deep Learning Pseudo-CT Estimated MR Images

BACKGROUND AND PURPOSE

CT imaging exposes patients to ionizing radiation. MR imaging is radiation free but previously has not been able to produce diagnostic-quality images of bone on a timeline suitable for clinical use. We developed automated motion correction and use deep learning to generate pseudo-CT images from MR images. We aim to evaluate whether motion-corrected pseudo-CT produces cranial images that have potential to be acceptable for clinical use.

MATERIALS AND METHODS

Patients younger than age 18 who underwent CT imaging of the head for either trauma or evaluation of cranial suture patency were recruited. Subjects underwent a 5-minute golden-angle stack-of-stars radial volumetric interpolated breath-hold MR image. Motion correction was applied to the MR imaging followed by a deep learning-based method to generate pseudo-CT images. CT and pseudo-CT images were evaluated and, based on indication for imaging, either presence of skull fracture or cranial suture patency was first recorded while viewing the MR imaging-based pseudo-CT and then recorded while viewing the clinical CT.

RESULTS

A total of 12 patients underwent CT and MR imaging to evaluate suture patency, and 60 patients underwent CT and MR imaging for evaluation of head trauma. For cranial suture patency, pseudo-CT had 100% specificity and 100% sensitivity for the identification of suture closure. For identification of skull fractures, pseudo-CT had 100% specificity and 90% sensitivity.

CONCLUSIONS

Our early results show that automated motion-corrected and deep learning-generated pseudo-CT images of the pediatric skull have potential for clinical use and offer a high level of diagnostic accuracy when compared with standard CT scans.

Fast field echo resembling CT using restricted echo-spacing (FRACTURE) MR sequence can provide craniocervical region images comparable to a CT in dogs

Magnetic resonance imaging (MRI) is essential for evaluating cerebellar compression in patients with craniocervical junction abnormalities (CJA). However, it is limited in depicting cortical bone because of its short T2 relaxation times, low proton density, and organized structure. Fast field echo resembling a computed tomography (CT) scan using restricted echo-spacing (FRACTURE) MRI, is a new technique that offers CT-like bone contrast without radiation. This study aimed to assess the feasibility of using FRACTURE MRI for craniocervical junction (CCJ) assessment compared with CT and conventional MRI, potentially reducing the need for multiple scans and radiation exposure, and simplifying procedures in veterinary medicine. CT and MRI of the CCJ were obtained from five healthy beagles. MRI was performed using three-dimensional (3D) T1-weighted, T2-weighted, proton density-weighted (PDW), single echo-FRACTURE (sFRACTURE), and multiple echo-FRACTURE (mFRACTURE) sequences. For qualitative assessment, cortical delineation, trabecular bone visibility, joint space visibility, vertebral canal definition, overall quality, and artifacts were evaluated for each sequence. The geometrical accuracy, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were quantified. Both sFRACTURE and CT images provided significantly higher scores for cortical delineation and trabecular bone visibility than conventional MRI. Joint space visibility and vertebral canal definition were similar to those observed on CT images, regardless of the MR sequence. In the quantitative assessment, the distances measured on T2-weighted images differed significantly from those measured on CT. There were no significant differences between the distances taken using T1-weighted, PD-weighted, sFRACTURE, mFRACTURE and those taken using CT. T1-weighted and sFRACTURE had a higher SNR for trabecular bone than CT. The CNR between the cortical bone and muscle was high on CT and FRACTURE images. However, the CNR between the cortical and trabecular bones was low in mFRACTURE. Similar to CT, FRACTURE sequences showed higher cortical delineation and trabecular bone visibility than T2-weighted, T1-weighted, and PDW CCJ sequences. In particular, sFRACTURE provided a high signal-to-noise ratio (SNR) of the trabecular bone and a high CNR between the cortical bone and muscle and between the cortical and trabecular bones. FRACTURE sequences can complement conventional MR sequences for bone assessment of the CCJ in dogs.

Cranial bone imaging using ultrashort echo-time bone-selective MRI as an alternative to gradient-echo based "black-bone" techniques

OBJECTIVES

CT is the clinical standard for surgical planning of craniofacial abnormalities in pediatric patients. This study evaluated three MRI cranial bone imaging techniques for their strengths and limitations as a radiation-free alternative to CT.

METHODS

Ten healthy adults were scanned at 3 T with three MRI sequences: dual-radiofrequency and dual-echo ultrashort echo time sequence (DURANDE), zero echo time (ZTE), and gradient-echo (GRE). DURANDE bright-bone images were generated by exploiting bone signal intensity dependence on RF pulse duration and echo time, while ZTE bright-bone images were obtained via logarithmic inversion. Three skull segmentations were derived, and the overlap of the binary masks was quantified using dice similarity coefficient. Craniometric distances were measured, and their agreement was quantified.

RESULTS

There was good overlap of the three masks and excellent agreement among craniometric distances. DURANDE and ZTE showed superior air-bone contrast (i.e., sinuses) and soft-tissue suppression compared to GRE.

DISCUSSIONS

ZTE has low levels of acoustic noise, however, ZTE images had lower contrast near facial bones (e.g., zygomatic) and require effective bias-field correction to separate bone from air and soft-tissue. DURANDE utilizes a dual-echo subtraction post-processing approach to yield bone-specific images, but the sequence is not currently manufacturer-supported and requires scanner-specific gradient-delay corrections.

Imaging evaluation of a proposed 3D generative model for MRI to CT translation in the lumbar spine

BACKGROUND CONTEXT

A computed tomography (CT) and magnetic resonance imaging (MRI) are used routinely in the radiologic evaluation and surgical planning of patients with lumbar spine pathology, with the modalities being complimentary. We have developed a deep learning algorithm which can produce 3D lumbar spine CT images from MRI data alone. This has the potential to reduce radiation to the patient as well as burden on the health care system.

PURPOSE

The purpose of this study is to evaluate the accuracy of the synthetic lumbar spine CT images produced using our deep learning model.

STUDY DESIGN

A training set of 400 unpaired CTs and 400 unpaired MRI scans of the lumbar spine was used to train a supervised 3D cycle-Gan model. Evaluators performed a set of clinically relevant measurements on 20 matched synthetic CTs and true CTs. These measurements were then compared to assess the accuracy of the synthetic CTs.

PATIENT SAMPLE

The evaluation data set consisted of 20 patients who had CT and MRI scans performed within a 30-day period of each other. All patient data was deidentified. Notable exclusions included artefact from patient motion, metallic implants or any intervention performed in the 30 day intervening period.

OUTCOME MEASURES

The outcome measured was the mean difference in measurements performed by the group of evaluators between real CT and synthetic CTs in terms of absolute and relative error.

METHODS

Data from the 20 MRI scans was supplied to our deep learning model which produced 20 "synthetic CT" scans. This formed the evaluation data set. Four clinical evaluators consisting of neurosurgeons and radiologists performed a set of 24 clinically relevant measurements on matched synthetic CT and true CTs in 20 patients. A test set of measurements were performed prior to commencing data collection to identify any significant interobserver variation in measurement technique.

RESULTS

The measurements performed in the sagittal plane were all within 10% relative error with the majority within 5% relative error. The pedicle measurements performed in the axial plane were considerably less accurate with a relative error of up to 34%.

CONCLUSIONS

The computer generated synthetic CTs demonstrated a high level of accuracy for the measurements performed in-plane to the original MRIs used for synthesis. The measurements performed on the axial reconstructed images were less accurate, attributable to the images being synthesized from nonvolumetric routine sagittal T1-weighted MRI sequences. It is hypothesized that if axial sequences or volumetric data were input into the algorithm these measurements would have improved accuracy.

Combined rapid sequence MRI protocol and skull radiography as an alternative to head CT in the evaluation of abusive head trauma in children: a pilot study

The aim of our pilot study was to compare the performance of the RS-MRI protocol combined with skull radiography versus CT for the detection of skull fractures, scalp hematomas, and intracranial hemorrhage in patients with abusive head trauma (AHT). Additionally, our study aimed to determine whether the presence of scalp hematoma predicts concurrent skull fracture. We conducted a pilot study through retrospective chart review of 24 patients between ages 0 and 15 months who experienced AHT and who received CT, MRI, and skull radiography between May 2020 and August 2021. Two blinded board certified neuroradiologists reviewed the skull radiographs alongside the rapid trauma MRI. Their impressions were documented and compared with findings derived from CT. Combination imaging detected ten out of the 12 skull fractures noted on CT (sensitivity 83.3%, specificity 100%, p=0.48). RS-MRI detected 15 out of the 16 intracranial hemorrhages detected by CT (sensitivity 93.75%, p >0.9). When scalp hematoma was detected on RS-MRI, nine out of the 12 had associated skull fractures when reviewed by radiologist 1 (sensitivity 75%, specificity 100%, p=0.22), and seven out of the 12 had associated skull fractures when reviewed by radiologist 2 (sensitivity 58%, specificity 92%, p=0.25). In pediatric patients with suspected AHT, we found that RS-MRI combined with skull radiographs was not significantly different than CT for the detection of skull fractures, scalp hematomas, and intracranial hemorrhage. This combination has the potential to replace the use of CT as a screening tool for abusive head trauma, while avoiding the risks of sedation often required for routine MRI.

Machine Learning Analysis of the Anatomical Parameters of the Upper Airway Morphology: A Retrospective Study from Cone-Beam CT Examinations in a French Population

The objective of this study is to assess, using cone-beam CT (CBCT) examinations, the correlation between hard and soft anatomical parameters and their impact on the characteristics of the upper airway using symbolic regression as a machine learning strategy. Methods: On each CBCT, the upper airway was segmented, and 24 anatomical landmarks were positioned to obtain six angles and 19 distances. Some anatomical landmarks were related to soft tissues and others were related to hard tissues. To explore which variables were the most influential to explain the morphology of the upper airway, principal component and symbolic regression analyses were conducted. Results: In total, 60 CBCT were analyzed from subjects with a mean age of 39.5 ± 13.5 years. The intra-observer reproducibility for each variable was between good and excellent. The horizontal soft palate measure mostly contributed to the reduction of the airway volume and minimal section area with a variable importance of around 50%. The tongue and the position of the hyoid bone were also linked to the upper airway morphology. For hard anatomical structures, the anteroposterior position of the mandible and the maxilla had some influence. Conclusions: Although the volume of the airway is not accessible on all CBCT scans performed by dental practitioners, this study demonstrates that a small number of anatomical elements may be markers of the reduction of the upper airway with, potentially, an increased risk of obstructive sleep apnea. This could help the dentist refer the patient to a suitable physician.

Black Bone MRI for Virtual Surgical Planning in Craniomaxillofacial Surgery

Advances in computer-aided design and computer-aided manufacturing software have improved translational applications of virtual surgical planning (VSP) in craniomaxillofacial surgery, allowing for precise and accurate fabrication of cutting guides, stereolithographic models, and custom implants. High-resolution computed tomography (CT) imaging has traditionally been the gold standard imaging modality for VSP in craniomaxillofacial surgery but delivers ionizing radiation. Black bone magnetic resonance imaging (MRI) reduces the risks related to radiation exposure and has comparable functionality when compared with CT for VSP. Our group has studied the accuracy of utilizing black bone MRI in planning and executing several types of craniofacial surgeries, including cranial vault remodeling, maxillary advancement, and mandibular reconstruction using fibular bone. Here, we review clinical applications of black bone MRI pertaining to VSP and three-dimensional (3D)-printed guide creation for craniomaxillofacial surgery. Herein, we review the existing literature and our institutional experience comparing black bone MRI and CT in VSP-generated 3D model creation in cadaveric craniofacial surgeries including cranial vault reconstruction, maxillary advancement, and mandibular reconstruction with fibular free flap. Cadaver studies have demonstrated the ability to perform VSP and execute the procedure based on black bone MRI data and achieve outcomes similar to CT when performed for cranial vault reshaping, maxillary advancement, and mandibular reconstruction with free fibula. Limitations of the technology include increased time and costs of the MRI compared with CT and the possible need for general anesthesia or sedation in the pediatric population. VSP and 3D surgical guide creation can be performed using black bone MRI with comparable accuracy to high-resolution CT scans in a wide variety of craniofacial reconstructions. Successful segmentation, VSP, and 3D printing of accurate guides from black bone MRI demonstrate potential to change the preoperative planning standard of care. Black bone MRI also reduces exposure to ionizing radiation, which is of particular concern for the pediatric population or patients undergoing multiple scans.

Deep-learning synthesized pseudo-CT for MR high-resolution pediatric cranial bone imaging (MR-HiPCB)

PURPOSE

CT is routinely used to detect cranial abnormalities in pediatric patients with head trauma or craniosynostosis. This study aimed to develop a deep learning method to synthesize pseudo-CT (pCT) images for MR high-resolution pediatric cranial bone imaging to eliminating ionizing radiation from CT.

METHODS

3D golden-angle stack-of-stars MRI were obtained from 44 pediatric participants. Two patch-based residual UNets were trained using paired MR and CT patches randomly selected from the whole head (NetWH) or in the vicinity of bone, fractures/sutures, or air (NetBA) to synthesize pCT. A third residual UNet was trained to generate a binary brain mask using only MRI. The pCT images from NetWH (pCTNetWH ) in the brain area and NetBA (pCTNetBA ) in the nonbrain area were combined to generate pCTCom . A manual processing method using inverted MR images was also employed for comparison.

RESULTS

pCTCom (68.01 ± 14.83 HU) had significantly smaller mean absolute errors (MAEs) than pCTNetWH (82.58 ± 16.98 HU, P < 0.0001) and pCTNetBA (91.32 ± 17.2 HU, P < 0.0001) in the whole head. Within cranial bone, the MAE of pCTCom (227.92 ± 46.88 HU) was significantly lower than pCTNetWH (287.85 ± 59.46 HU, P < 0.0001) but similar to pCTNetBA (230.20 ± 46.17 HU). Dice similarity coefficient of the segmented bone was significantly higher in pCTCom (0.90 ± 0.02) than in pCTNetWH (0.86 ± 0.04, P < 0.0001), pCTNetBA (0.88 ± 0.03, P < 0.0001), and inverted MR (0.71 ± 0.09, P < 0.0001). Dice similarity coefficient from pCTCom demonstrated significantly reduced age dependence than inverted MRI. Furthermore, pCTCom provided excellent suture and fracture visibility comparable to CT.

CONCLUSION

MR high-resolution pediatric cranial bone imaging may facilitate the clinical translation of a radiation-free MR cranial bone imaging method for pediatric patients.

Zero-TE MRI: principles and applications in the head and neck

Zero echo-time (ZTE) MRI is a novel imaging technique that utilizes ultrafast readouts to capture signal from short-T2 tissues. Additional sequence advantages include rapid imaging times, silent scanning, and artifact resistance. A robust application of this technology is imaging of cortical bone without the use of ionizing radiation, thus representing a viable alternative to CT for both rapid screening and "one-stop-shop" MRI. Although ZTE is increasingly used in musculoskeletal and body imaging, neuroimaging applications have historically been limited by complex anatomy and pathology. In this article, we review the imaging physics of ZTE including pulse sequence options, practical limitations, and image reconstruction. We then discuss optimization of settings for ZTE bone neuroimaging including acquisition, processing, segmentation, synthetic CT generation, and artifacts. Finally, we examine clinical utility of ZTE in the head and neck with imaging examples including malformations, trauma, tumors, and interventional procedures.

Cranial vault imaging for pediatric head trauma using a radial VIBE MRI sequence

OBJECTIVE

Head trauma is the most common indication for a CT scan. In this pilot study, the authors assess the feasibility of a 5-minute high-resolution 3D golden-angle (GA) stack-of-stars radial volumetric interpolated breath-hold examination (VIBE) MRI sequence (GA-VIBE) to obtain clinically acceptable cranial bone images and identify cranial vault fractures compared to CT.

METHODS

Patients younger than 18 years of age presenting after head trauma were eligible for the study. Three clinicians reviewed and assessed 1) slice-by-slice volumetric CT and inverted MR images, and 2) 3D reconstructions obtained from inverted MR images and the gold standard (CT). For each image set, reviewers noted on 5-point Likert scales whether they recommended that a repeat scan be performed and the presence or absence of cranial vault fractures.

RESULTS

Thirty-one patients completed MRI after a clinical head CT scan was performed. Based on CT imaging, 8 of 31 patients had cranial fractures. Two of 31 patients were sedated as part of their clinical MRI scan. In 30 (97%) of 31 MRI reviews, clinicians agreed (or strongly agreed) that the image quality was acceptable for clinical diagnosis. Overall, comparing MRI to acceptable gold-standard CT, sensitivity and specificity of fracture detection were 100%. Furthermore, there were no discrepancies between CT and MRI in classification of fracture type or location.

CONCLUSIONS

When compared with the gold standard (CT), the volumetric and 3D reconstructed images using the GA-VIBE sequence were able to produce clinically acceptable cranial images with excellent ability to detect cranial vault fractures.

Non-ionizing Imaging for the Emergency Department Assessment of Pediatric Minor Head Trauma

Minor blunt head trauma (MHT) represents a common reason for presentation to the pediatric emergency department (ED). Despite the low incidence of clinically important traumatic brain injuries (ciTBIs) following MHT, many children undergo computed tomography (CT), exposing them to the risk associated with ionizing radiation. The clinical predictions rules developed by the Pediatric Emergency Care Applied Research Network (PECARN) for MHT are validated accurate tools to support decision-making about neuroimaging for these children to safely reduce CT scans. However, a few non-ionizing imaging modalities have the potential to contribute to further decrease CT use. This narrative review provides an overview of the evidence on the available non-ionizing imaging modalities that could be used in the management of children with MHT, including point of care ultrasound (POCUS) of the skull, near-infrared spectroscopy (NIRS) technology and rapid magnetic resonance imaging (MRI). Skull ultrasound has proven an accurate bedside tool to identify the presence and characteristics of skull fractures. Portable handheld NIRS devices seem to be accurate screening tools to identify intracranial hematomas also in pediatric MHT, in selected scenarios. Both imaging modalities may have a role as adjuncts to the PECARN rule to help refine clinicians' decision making for children at high or intermediate PECARN risk of ciTBI. Lastly, rapid MRI is emerging as a feasible and accurate alternative to CT scan both in the ED setting and when repeat imaging is needed. Advantages and downsides of each modality are discussed in detail in the review.

Imaging of Bone in the Head and Neck Region, is There More Than CT?

Purpose of Review

The objective of this review is to document the advances in non-ionising imaging alternatives to CT for the head and neck.

Recent Findings

The main alternative to CT for imaging bone of the head and neck region is MRI, particularly techniques which incorporate gradient echo imaging (Black Bone technique) and ultra-short or zero-echo time imaging. Since these techniques can provide high resolution isometric voxels, they can be used to provide multi-planar reformats and, following post processing, 3D reconstructed images of the craniofacial skeleton. As expected, the greatest advancements in recent years have been focused on enhanced image processing techniques and attempts to address the difficulties encountered at air-bone interfaces.

Summary

This article will review the imaging techniques and recent advancements which are bringing non-ionising alternatives to CT imaging of the bone of the head and neck region into the realm of routine clinical application.

Magnetic Resonance Imaging Versus Computed Tomography for Three-Dimensional Bone Imaging of Musculoskeletal Pathologies: A Review

Magnetic resonance imaging (MRI) is increasingly utilized as a radiation‐free alternative to computed tomography (CT) for the diagnosis and treatment planning of musculoskeletal pathologies. MR imaging of hard tissues such as cortical bone remains challenging due to their low proton density and short transverse relaxation times, rendering bone tissues as nonspecific low signal structures on MR images obtained from most sequences. Developments in MR image acquisition and post‐processing have opened the path for enhanced MR‐based bone visualization aiming to provide a CT‐like contrast and, as such, ease clinical interpretation. The purpose of this review is to provide an overview of studies comparing MR and CT imaging for diagnostic and treatment planning purposes in orthopedic care, with a special focus on selective bone visualization, bone segmentation, and three‐dimensional (3D) modeling. This review discusses conventional gradient‐echo derived techniques as well as dedicated short echo time acquisition techniques and post‐processing techniques, including the generation of synthetic CT, in the context of 3D and specific bone visualization. Based on the reviewed literature, it may be concluded that the recent developments in MRI‐based bone visualization are promising. MRI alone provides valuable information on both bone and soft tissues for a broad range of applications including diagnostics, 3D modeling, and treatment planning in multiple anatomical regions, including the skull, spine, shoulder, pelvis, and long bones.

Ultrashort Echo-Time MR Imaging of the Pediatric Head and Neck

Bone MR imaging techniques use extremely rapid echo times to maximize detection of short-T2 tissues with low water concentrations. The major approaches used in clinical practice are ultrashort echo-time and zero echo-time. Synthetic CT generation is feasible using atlas-based, voxel-based, and deep learning approaches. Major clinical applications in the pediatric head and neck include evaluation for craniosynostosis, sinonasal and jaw imaging, trauma, interventional planning, and postoperative follow-up. In this article, we review the technical background and practical usefulness of bone MR imaging with key imaging examples.

Rapid-sequence MRI for evaluation of pediatric traumatic brain injury: a systematic review

OBJECTIVE

Rapid-sequence MRI (RSMRI) of the brain is a limited-sequence MRI protocol that eliminates ionizing radiation exposure and reduces imaging time. This systematic review sought to examine studies of clinical RSMRI use for pediatric traumatic brain injury (TBI) and to evaluate various RSMRI protocols used, including their reported accuracy as well as clinical and systems-based limitations to implementation.

METHODS

PubMed, EMBASE, and Web of Science databases were searched, and clinical articles reporting the use of a limited brain MRI protocol in the setting of pediatric head trauma were identified.

RESULTS

Of the 1639 articles initially identified and reviewed, 13 studies were included. An additional article that was in press at the time was provided by its authors. The average RSMRI study completion time was variable, spanning from 1 minute to 16 minutes. RSMRI with "blood-sensitive" sequences was more sensitive for detection of hemorrhage compared with head CT (HCT), but less sensitive for detection of skull fractures. Compared with standard MRI, RSMRI had decreased sensitivity for all evidence of trauma.

CONCLUSIONS

Protocols and uses of RSMRI for pediatric TBI were variable among the included studies. While traumatic pathology missed by RSMRI, such as small hemorrhages and linear, nondisplaced skull fractures, was frequently described as clinically insignificant, in some cases these findings may be prognostically and/or forensically significant. Institutions should integrate RSMRI into pediatric TBI management judiciously, relying on clinical context and institutional capabilities.

3D MRI with CT-like bone contrast - An overview of current approaches and practical clinical implementation

CT is the imaging modality of choice for assessment of 3D bony morphology but incurs the penalty of ionizing radiation. Improving the ability of 3D MRI to provide high-resolution images of cortical bone with CT-like bone contrast has been a focus of recent research. The ability of 3D MRI to deliver cortical bone information with similar diagnostic performance to CT would complement assessment of soft tissues and medullary bone from a single MRI examination, simplifying evaluation and obviating radiation exposure from additional CT. This article presents an overview of current 3D MRI approaches for imaging cortical bone with CT-like bone contrast including ultrashort echo time, zero echo time, T1-weighted gradient recalled echo, susceptibility-weighted imaging and deep learning techniques. We also discuss clinical implementation of an optimized stack-of-stars 3D gradient recalled echo pulse sequence (3D-Bone) on commercially available MRI scanners for rendering 3D MRI with CT-like bone contrast in our institutional practice.

Fast field echo resembling a CT using restricted echo-spacing (FRACTURE): a novel MRI technique with superior bone contrast

OBJECTIVE

Computerized tomography (CT) is the modality of choice for imaging bone; however, it utilizes ionizing radiation and suffers from poor soft-tissue contrast. Unlike CT, magnetic resonance imaging (MRI) provides excellent soft-tissue contrast but is limited in its ability to image bone. The objective of this study is to describe a new technical innovation which provides superior cortical and trabecular bone contrast on MRI.

METHODS

FRACTURE (fast field echo resembling a CT using restricted echo-spacing), a 3D gradient echo pulse sequence with restricted echo-spacing combined with an automated post-processing, is described.

RESULTS

Cases demonstrating the application and utility of this technique in diagnostic MRI performed for traumatic, inflammatory, neoplastic, and developmental conditions in pediatric patients are presented.

CONCLUSION

The cortical and trabecular bone contrast generated by FRACTURE yields clinically relevant information for diagnosis and management of a subset of patients in whom it may potentially obviate the need for a preoperative CT scan.

Clinical application of "black bone" imaging in paediatric craniofacial disorders

For decades, CT has been the primary imaging modality for the diagnosis and surveillance of paediatric craniofacial disorders. However, the deleterious effects of ionising radiation in the paediatric population are well established and remain an ongoing concern. This is especially so in the head and neck region, which has relatively poor soft tissue shielding with many radiosensitive organs. The development of "black bone" imaging utilising low flip angles and short echo time (TE) has shown considerable promise in alleviating the use of ionising radiation in many cases of craniofacial disorders. In this review article, we share our experience of utilising "black bone" sequence in children with craniofacial pathologies, ranging from traumatic injuries to craniosynostosis and focal osseous/fibro-osseous lesions such as fibrous dysplasia and Langerhans cell histiocytosis (LCH). A detailed discussion on the technical aspects of "black bone" sequence, including its potential pitfalls and limitations, will also be included.

A review of current imaging techniques used for the detection of occult bony fractures in young children suspected of sustaining non-accidental injury

Non-accidental injuries remain a leading cause of preventable morbidity and mortality in young children. The accurate identification of the full spectrum of injuries in children presenting with suspected abuse is essential to ensure the appropriate protective intervention is taken. The identification of occult bone fractures in this cohort is important as it raises the level of concern about the mechanism of injury and maintaining the child's safety. Radiographic imaging remains the modality of choice for skeletal assessment; however, current studies report concerns regarding the ability of radiographs to detect certain fractures in the acute stage. As such, alternative modalities for the detection of fractures have been proposed. This article reviews the current literature regarding fracture detectability and radiation dose burden of imaging modalities currently used for the assessment of occult bony injury in young children in whom non-accidental injury is suspected.

Utility of a pediatric fast magnetic resonance imaging protocol as surveillance scanning for traumatic brain injury

OBJECTIVE

Traumatic brain injury (TBI) is a prevalent pediatric pathology in the modern emergency department. Computed tomography (CT) is utilized for detection of TBI and can result in cumulatively high radiation exposure. Recently, a fast brain magnetic resonance imaging (fbMRI) protocol has been employed for rapid imaging of hydrocephalus in pediatric patients. The authors investigate the utility of a modified trauma-focused fbMRI (t-fbMRI) protocol as an alternative to surveillance CT in the setting of acute TBI in pediatric patients, thus reducing radiation exposure while improving diagnostic yield.

METHODS

A retrospective review was performed at the authors' institution for all pediatric patients who had undergone t-fbMRI within 72 hours of an initial CT scan, using a 1.5- or 3-T MR scanner for trauma indications. Forty patients met the study inclusion criteria. The authors performed a comparison of findings on the reads of CT and fbMRI, and a board-certified neuroradiologist conducted an independent review of both modalities.

RESULTS

T-fbMRI outperformed CT in specificity, sensitivity, and negative predictive value for all injury pathologies measured, except for skull fractures. T-fbMRI demonstrated a sensitivity of 100% in the detection of extraaxial bleed, intraventricular hemorrhage, and subarachnoid hemorrhage and had a sensitivity of 78% or greater for epidural hematoma, subdural hematoma, and intraparenchymal hemorrhage. T-fbMRI yielded a specificity of 100% for all types of intracranial hemorrhages, with a corresponding negative predictive value that exceeded that for CT.

CONCLUSIONS

In pediatric populations, the t-fbMRI protocol provides a valid alternative to CT in the surveillance of TBI and intracranial hemorrhage. Although not as sensitive in the detection of isolated skull fractures, t-fbMRI can be used to monitor pathologies implicated in TBI patients while minimizing radiation exposure from traditional surveillance imaging.

Geometric and volumetric relationship between human lumbar vertebrae and "Black-bone" MRI-based models

BACKGROUND

This study will examine the differences between human lumbar vertebrae, three-dimensional (3D) scans of these bones, 3D models based on 'Black-bone' magnetic resonance imaging (MRI) scans, and 3D-printed models.

MATERIALS AND METHODS

3D mesh models were created from the "Black-bone" MRI data from two cadaveric human spines, and then 3D printed. Four models were analysed and compared: anatomic bones, 3D-scanned models, MRI models and 3D-printed models.

RESULTS

There was no significant difference between when comparing the average of all measurements between all model types (p = 0.81). The mean dice coefficient was 0.91 (SD 0.016) and the mean Hausdorff distance was 0.37 mm (SD 0.04 mm) when comparing the MRI model to the 3D-scanned model. The mean volumes for the MRI model and the 3D scanned model were 10.42 and 10.04 ml (p = 0.085), respectively.

CONCLUSIONS

The 'Black-bone' MRI could be a valid radiation-free alternative to computed tomography for the 3D printing of lumbar spinal biomodels.

Magnetic Resonance Imaging of the Brain in the Pediatric Emergency Department

Emergent imaging of the brain is often required to diagnose and manage serious and life-threatening conditions for children presenting to the emergency department. In an effort to reduce children's exposure to ionizing radiation, the use of magnetic resonance imaging (MRI) as an alternative to computed tomography (CT) is increasing. In some conditions, an urgent MRI rather than CT is critical for making management decisions. The purpose of this review is to highlight 3 emergency medical conditions-acute stroke, traumatic brain injury, and hydrocephalus-in which timely MRI of the brain is required for diagnosis and management. Another aim will be to guide providers in determining when and what limited MRI sequences of the brain can be used in lieu of CT in these emergency medical conditions.

'Black Bone' magnetic resonance imaging as a novel technique to aid the pre-operative planning of posterior tympanotomy for cochlear implantation

Purpose: 'Black Bone' magnetic resonance imaging (BB MRI) is a novel sequence developed as an alternative to computed tomography (CT) for osseous imaging. We explored its potential utilisation in the pre-operative surgical planning of posterior tympanotomy for cochlear implantation through depiction of the mastoid facial nerve (mFN) canal and the posterior canaliculus of the chorda tympani (ChT), thus defining the facial recess. Methods: Twenty five adult patients were prospectively imaged with a dedicated BB MRI sequence. A consensus qualitative BB MRI 'visibility score' for the confidence of demonstration of the mFN canal and the posterior canaliculus of the ChT was recorded, as well as a 'corresponding score' to determine whether the neural structures on BB MRI corresponded to the paths of the nerves on a previous CT study. Results/discussion: The BB MRI sequence was able to clearly delineate the course of mFN in 100% of cases and that of ChT in 72%, with their courses corresponding to those depicted on CT in almost all cases. Maximum intensity projections with 7 mm slabs provided the optimal simultaneous demonstration of mFN, ChT and round window along the posterior tympanotomy surgical approach. Conclusion: The proposed BB MRI sequence reliably depicts mFN and ChT in the majority of cases, with a performance comparable to that of CT. It is proposed that it will be a useful adjunct to MRI protocols as part of cochlear implant assessment in those centres where CT is not routinely performed.

Automated Segmentation of the Craniofacial Skeleton With "Black Bone" Magnetic Resonance Imaging

Three-dimensional (3D) imaging of the craniofacial skeleton is integral in managing a wide range of bony pathologies. The authors have previously demonstrated the potential of "Black Bone" MRI (BB) as a non-ionizing alternative to CT. However, even in experienced hands 3D rendering of BB datasets can be challenging and time consuming. The objectives of this study were to develop and test a semi- and fully-automated segmentation algorithm for the craniofacial skeleton.Previously acquired adult volunteer (n = 15) BB datasets of the head were utilized. Imaging was initially 3D rendered with our conventional manual technique. An algorithm to remove the outer soft-tissue envelope was developed and 3D rendering completed with the processed datasets (semi-automated). Finally, a fully automated 3D-rendering method was developed and applied to the datasets. All 3D rendering was completed with Fovia High Definition Volume Rendering (Fovia Inc, Palo Alto, CA). Analysis was undertaken of the 3D visual results and the time taken for data processing and interactive manipulation.The mean time for manual segmentation was 12.8 minutes, 3.1 minutes for the semi-automated algorithm, and 0 minutes for the fully automated algorithm. Further fine adjustment was undertaken to enhance the automated segmentation results, taking a mean time of 1.4 minutes.Automated segmentation demonstrates considerable potential, offering significant time saving in the production of 3D BB imaging in adult volunteers. the authors continue to undertake further development of our segmentation algorithms to permit adaption to the pediatric population in whom non-ionizing imaging confers the most potential benefit.

Emergency department implementation of abbreviated magnetic resonance imaging for pediatric traumatic brain injury

Pediatric head injury is a common presenting complaint in the emergency department (ED), often requiring neuroimaging or ED observation for diagnosis. However, the traditional diagnostic neuroimaging modality, head computed tomography (CT), is associated with radiation exposure while prolonged ED observation impacts patient flow and resource utilization. Recent scientific literature supports abbreviated, or focused and shorter, brain magnetic resonance imaging (MRI) as a feasible and accurate diagnostic alternative to CT for traumatic brain injury. However, this is a relatively new application and its use is not widespread. The aims of this review are to describe the science and applications of abbreviated brain MRI and report a model protocol's development and ED implementation in the evaluation of children with head injury for replication in other institutions.

3D pediatric cranial bone imaging using high-resolution MRI for visualizing cranial sutures: a pilot study

OBJECTIVE

There is an unmet need to perform imaging in young children and obtain CT-equivalent cranial bone images without subjecting the patients to radiation. In this study, the authors propose using a high-resolution fast low-angle shot golden-angle 3D stack-of-stars radial volumetric interpolated breath-hold examination (GA-VIBE) MRI sequence that is intrinsically robust to motion and has enhanced bone versus soft-tissue contrast.

METHODS

Patients younger than 11 years of age, who underwent clinical head CT scanning for craniosynostosis or other cranial malformations, were eligible for the study. 3D reconstructed images created from the GA-VIBE MRI sequence and the gold-standard CT scan were randomized and presented to 3 blinded reviewers. For all image sets, each reviewer noted the presence or absence of the 6 primary cranial sutures and recorded on 5-point Likert scales whether they recommended a second scan be performed.

RESULTS

Eleven patients (median age 1.8 years) underwent MRI after clinical head CT scanning was performed. Five of the 11 patients were sedated. Three clinicians reviewed the images, and there were no cases, either with CT scans or MR images, in which a reviewer agreed a repeat scan was required for diagnosis or surgical planning. The reviewers reported clear imaging of the regions of interest on 99% of the CT reviews and 96% of the MRI reviews. With CT as the standard, the sensitivity and specificity of the GA-VIBE MRI sequence to detect suture closure were 97% and 96%, respectively (n = 198 sutures read).

CONCLUSIONS

The 3D reconstructed images using the GA-VIBE sequence in comparison to the CT scans created clinically acceptable cranial images capable of detecting cranial sutures. Future directions include reducing the scan time, improving motion correction, and automating postprocessing for clinical utility.

Cranial Suture Evaluation on Routine Pediatric MRI

PURPOSE

The efficacy of magnetic resonance imaging (MRI) for evaluating sutures has not been well studied. CT with 3-dimensional reformats is currently the preferred modality for imaging the major cranial sutures. The role of MRI is primarily is for evaluating the brain for any concurrent malformations. Our objective was to evaluate the reliability of MRI when compared to CT for evaluation of cranial sutures.

METHODS

A list of 500 consecutive patients who underwent an MRI as well as a CT study was obtained. Studies were done between January 2011 and December 2016. The inclusion criteria required the 2 studies to be performed within 3 months of each other. All MRI studies were reviewed by a pediatric neuroradiologist to determine whether the sagittal, coronal, and lambdoid sutures were patent, fused or could not be assessed with confidence. In cases where a confident determination could not be made, the studies were reviewed with another pediatric neuro-radiologist and a decision made in concurrence. The CT scans were then evaluated in a similar fashion, after the MRI review was completed. The CT and MRI results were then compared to determine the accuracy of the MRI in assessing the sutures.

RESULTS

Mean age of the studied children was 8.54 years. Seventy-two percent of the sagittal sutures were seen. When seen the sagittal suture was correctly identified in 98% of cases as either fused or patent. The lambdoid suture was seen in 94.3% of studies and was correctly designated as patent or fused in 99.6% of that subset of cases. The coronal suture was seen in 66.3% of the cases and when seen was always (100%) correctly designated. The probability of agreement between MRI and CT increased with age. The probability of sutures which were not seen decreased with age. The false negative and positives remained low for all ages.

CONCLUSIONS

MRI is a viable tool for detection of cranial sutures. The 3-dimensional T1 Weighted sequence was particularly useful in suture evaluation. Although the visibility of sutures is inferior to that on a CT scan, if detected, the accuracy scan is fairly accurate in establishing fusion vs patency. It should be a part of routine surveillance on every pediatric neuro MRI study given the neurocognitive implications of incidental sutural synostosis.

Detection of Coalescent Acute Mastoiditis on MRI in Comparison with CT

Purpose

Current imaging standard for acute mastoiditis (AM) is contrast-enhanced computed tomography (CT), revealing inflammation-induced bone destruction, whereas magnetic resonance imaging (MRI) outperforms CT in detecting intracranial infection. Our aim was to compare the diagnostic performance of MRI with CT in detecting coalescent AM and see to which extent MRI alone would suffice to diagnose or rule out this condition.

Methods

The MR images of 32 patients with AM were retrospectively analyzed. Bone destruction was evaluated from T2 turbo spin echo (TSE) and T1 Gd magnetization-prepared rapid acquisition with gradient echo (MPRAGE) images. Intramastoid enhancement and diffusion restriction were evaluated subjectively and intramastoid apparent diffusion coefficient (ADC) values were measured. The MRI findings were compared with contrast-enhanced CT findings of the same patients within 48 h of the MR scan.

Results

Depending on the anatomical subsite, MRI detected definite bone defects with a sensitivity of 100% and a specificity of 54–82%. Exception was the inner cortical table where sensitivity was only 14% and specificity was 76%. Sensitivity for general coalescent mastoiditis remained 100% due to multiple coexisting lesions. The absence of intense enhancement and non-restricted diffusion had a high negative predictive value for coalescent mastoiditis: an intramastoid ADC above 1.2 × 10⁻³ mm²/s excluded coalescent mastoiditis with a negative predictive value of 92%.

Conclusion

The MRI did not miss coalescent mastoiditis but was inferior to CT in direct estimation of bone defects. When enhancement and diffusion characteristics are also considered, MRI enables dividing patients into low, intermediate and high-risk categories with respect to coalescent mastoiditis, where only the intermediate risk group is likely to benefit from additional CT.

Technical Improvements in Head and Neck MR Imaging: At the Cutting Edge

Head and neck MR imaging is technically challenging because of magnetic field inhomogeneity, respiratory and swallowing motion, and necessity of high-resolution imaging to trace key anatomic structures. These challenges have been answered by advances in MR imaging technology, including isovolumetric three-dimensional imaging, robust fat-water separation techniques, and novel deep learning-based reconstruction algorithms. New applications of MR imaging have been advanced and functional imaging has been improved. Improvements in acquisition and reconstruction technique facilitate novel applications of morphologic and functional imaging. This results in opportunities to improve diagnosis, staging, and treatment selection through application of advanced MR imaging techniques.

Zero TE MRI for Craniofacial Bone Imaging

Zero TE MR imaging is a novel technique that achieves a near-zero time interval between radiofrequency excitation and data acquisition, enabling visualization of short-T2 materials such as cortical bone. Zero TE offers a promising radiation-free alternative to CT with rapid, high-resolution, silent, and artifact-resistant imaging, as well as the potential for "pseudoCT" reconstructions. In this report, we will discuss our preliminary experience with zero TE, including technical principles and a clinical case series demonstrating emerging applications in neuroradiology.

Avoiding skull radiographs in infants with suspected inflicted injury who also undergo head CT: "a no-brainer?"

Objectives

To assess whether head CT with 3D reconstruction can replace skull radiographs (SXR) in the imaging investigation of suspected physical abuse (SPA)/abusive head trauma (AHT).

Methods

PACS was interrogated for antemortem skeletal surveys performed for SPA, patients younger than 2 years, SXR and CT performed within 4 days of each other. Paired SXR and CT were independently reviewed. One reviewer analysed CT without and (3 months later) with 3D reconstructions. SXR and CT expert consensus review formed the gold standard. Observer reliability was calculated.

Results

A total of 104 SXR/CT examination pairs were identified, mean age 6.75 months (range 4 days to 2 years); 21 (20%) had skull fractures; two fractures on CT were missed on SXR. There were no fractures on SXR that were not seen on CT. For SXR and CT, respectively: PPV reviewer 1, 95% confidence interval (CI) 48–82% and 85–100%; reviewer 2, 67–98% and 82–100%; and NPV reviewer 1, 95%, CI 88–98% and 96–100%; reviewer 2, 88–97% and 88–98%. Inter- and intra-observer reliability were respectively the following: SXR, excellent (kappa = 0.831) and good (kappa = 0.694); CT, excellent (kappa = 0.831) and perfect (kappa = 1). All results were statistically significant (p < 0.001).

Conclusions

CT has greater diagnostic accuracy than SXR in detecting skull fractures which is increased on concurrent review of 3D reconstructions and should be performed in every case of SPA/AHT. SXR does not add further diagnostic information and can be omitted from the skeletal survey when CT with 3D reconstruction is going to be, or has been, performed.

Key Points

• Head CT with 3D reconstruction is more sensitive and specific for the diagnosis of skull fractures.

• Skull radiographs can be safely omitted from the initial skeletal survey performed for suspected physical abuse when head CT with 3D reconstruction is going to be, or has been, performed.

MRI Findings in Pediatric Abusive Head Trauma: A Review

Trauma is the most common cause of death and significant morbidity in childhood; abusive head trauma (AHT) is a prominent cause of significant morbidity and mortality in children younger than 2 years old. Correctly diagnosing AHT is challenging both clinically and radiologically. The primary diagnostic challenges are that the abused children are usually too young to provide an adequate history, perpetrators are unlikely to provide truthful account of trauma, and clinicians may be biased in their assessment of potentially abused children. The main radiological challenge is that there is no single imaging finding that is independently specific for or diagnostic of AHT. The radiological evaluation should be based on the multiplicity and severity of findings and an inconsistency with the provided mechanism of trauma. While the most common neuroimaging finding in AHT is subdural hemorrhage, other less well-known magnetic resonance imaging (MRI) findings such as the "lollipop sign" or "tadpole sign," parenchymal or cortical lacerations, subpial hemorrhage, cranio-cervical junction injuries including retroclival hematomas, as well as diffuse hypoxic brain injury have been identified and described in the recent literature. While AHT is ultimately a clinical diagnosis combining history, exam, and neuroimaging, familiarity with the typical as well as the less-well known MRI findings will improve recognition of AHT by radiologists.

Feasibility and Accuracy of Fast MRI Versus CT for Traumatic Brain Injury in Young Children

BACKGROUND

Computed tomography (CT) is commonly used for children when there is concern for traumatic brain injury (TBI) and is a significant source of ionizing radiation. Our objective was to determine the feasibility and accuracy of fast MRI (motion-tolerant MRI sequences performed without sedation) in young children.

METHODS

In this prospective cohort study, we attempted fast MRI in children <6 years old who had head CT performed and were seen in the emergency department of a single, level 1 pediatric trauma center. Fast MRI sequences included 3T axial and sagittal T2 single-shot turbo spin echo, axial T1 turbo field echo, axial fluid-attenuated inversion recovery, axial gradient echo, and axial diffusion-weighted single-shot turbo spin echo planar imaging. Feasibility was assessed by completion rate and imaging time. Fast MRI accuracy was measured against CT findings of TBI, including skull fracture, intracranial hemorrhage, or parenchymal injury.

RESULTS

Among 299 participants, fast MRI was available and attempted in 225 (75%) and completed in 223 (99%). Median imaging time was 59 seconds (interquartile range 52-78) for CT and 365 seconds (interquartile range 340-392) for fast MRI. TBI was identified by CT in 111 (50%) participants, including 81 skull fractures, 27 subdural hematomas, 24 subarachnoid hemorrhages, and 35 other injuries. Fast MRI identified TBI in 103 of these (sensitivity 92.8%; 95% confidence interval 86.3-96.8), missing 6 participants with isolated skull fractures and 2 with subarachnoid hemorrhage.

CONCLUSIONS

Fast MRI is feasible and accurate relative to CT in clinically stable children with concern for TBI.

Clinical practice recommendations for the diagnosis and management of X-linked hypophosphataemia

X-linked hypophosphataemia (XLH) is the most common cause of inherited phosphate wasting and is associated with severe complications such as rickets, lower limb deformities, pain, poor mineralization of the teeth and disproportionate short stature in children as well as hyperparathyroidism, osteomalacia, enthesopathies, osteoarthritis and pseudofractures in adults. The characteristics and severity of XLH vary between patients. Because of its rarity, the diagnosis and specific treatment of XLH are frequently delayed, which has a detrimental effect on patient outcomes. In this Evidence-Based Guideline, we recommend that the diagnosis of XLH is based on signs of rickets and/or osteomalacia in association with hypophosphataemia and renal phosphate wasting in the absence of vitamin D or calcium deficiency. Whenever possible, the diagnosis should be confirmed by molecular genetic analysis or measurement of levels of fibroblast growth factor 23 (FGF23) before treatment. Owing to the multisystemic nature of the disease, patients should be seen regularly by multidisciplinary teams organized by a metabolic bone disease expert. In this article, we summarize the current evidence and provide recommendations on features of the disease, including new treatment modalities, to improve knowledge and provide guidance for diagnosis and multidisciplinary care.

Syndromic Craniosynostosis

Management strategies for syndromic craniosynostosis patients require multidisciplinary subspecialty teams to provide optimal care for complex reconstructive approaches. The most common craniosynostosis syndromes include Apert (FGFR2), Crouzon (FGFR2), Muenke (FGFR3), Pfeiffer (FGFR1 and FGFR2), and Saethre-Chotzen (TWIST). Bicoronal craniosynostosis (turribrachycephaly) is most commonly associated with syndromic craniosynostosis. Disease presentation varies from mild sutural involvement to severe pansynostoses, with a spectrum of extracraniofacial dysmorphic manifestations. Understanding the multifaceted syndromic presentations while appreciating the panoply of variable presentations is central to delivering necessary individualized care. Cranial vault remodeling aims to relieve restriction of cranial development and elevated intracranial pressure and restore normal morphology.

Non-invasive three-dimensional bone-vessel image fusion using black bone MRI based on FIESTA-C

AIM

To evaluate the image quality of bone-vessel fused volume-rendering (VR) images reconstructed by three-dimensional "black bone" magnetic resonance imaging (MRI) based on the fast imaging employing steady-state acquisition cycled phases (FIESTA-C) sequence and time-of-flight magnetic resonance angiography (TOF-MRA).

MATERIALS AND METHODS

Seventeen patients were analysed in this retrospective study. All patients underwent both MRI techniques including FIESTA-C and TOF-MRA and computed tomography angiography (CTA). MRI- and CT-based bone-vessel VR images were reconstructed. Visual depictions of frontal and parietal branches from the superficial temporal artery (STA) were independently scored by three experienced radiological technologists using a four-grade system.

RESULTS

In the visual evaluation, the scores of the both right and left frontal branches in MRI-based VR image were significantly larger those at CT (p<0.01, respectively). The scores of both the right and left parietal branches tended to be larger in MRI-based than that in CT-based VR imaging, but were not significantly so (p=0.06, 0.13 respectively). In the interobserver agreement analysis, κ values were all good (range: 0.6-0.76) for STA branch evaluation in MRI-based VR images.

CONCLUSION

MRI bone-vessel fused VR imaging can non-invasively depict STA frontal branches with better visibility compared to the CT-based VR imaging. This technique may be useful for the preoperative evaluation of donor branches for STA-middle cerebral artery bypass surgery.