Imaging of pediatric calvarial and skull base tumors: A COG Diagnostic Imaging Committee/SPR Oncology Committee/ASPNR White Paper.

A standardized imaging protocol for pediatric oncology patients is essential for accurate and efficient imaging, while simultaneously promoting collaborative understanding of pathologies and radiologic assessment of treatment response. The objective of this article is to provide standardized pediatric imaging guidelines and parameters for evaluation of tumors of the pediatric orbit, calvarium, skull base, and temporal bone. This article was drafted based on current scientific literature as well as consensus opinions of imaging experts in collaboration with the Children's Oncology Group Diagnostic Imaging Committee, Society of Pediatric Radiology Oncology Committee, and American Society of Pediatric Neuroradiology.

Patterns and Implications of Intracranial Arterial Remodeling in Stroke Patients.

BACKGROUND AND PURPOSE: Preliminary studies suggest that intracranial arteries are capable of accommodating plaque formation by remodeling. We sought to study the ability and extent of intracranial arteries to remodel using 3-dimensional high-resolution black blood magnetic resonance imaging and investigate its relation to ischemic events. METHODS: Forty-two patients with cerebrovascular ischemic events underwent 3-dimensional time-of-flight magnetic resonance angiography and contrast-enhanced black blood magnetic resonance imaging examinations at 3 T for intracranial atherosclerotic disease. Each plaque was classified by location (eg, posterior versus anterior circulation) and its likelihood to have caused a stroke identified on magnetic resonance imaging (culprit, indeterminate, or nonculprit). Lumen area, outer wall area, and wall area were measured at the lesion and reference sites. Plaque burden was calculated as wall area divided by outer wall area. The arterial remodeling ratio (RR) was calculated as outer wall area at the lesion site divided by outer wall area at the reference site after adjusting for vessel tapering. Arterial remodeling was categorized as positive if RR>1.05, intermediate if 0.95≤RR≤1.05, and negative if RR<0.95. RESULTS: One hundred and thirty-seven plaques were identified in 42 patients (37% [50] posterior and 63% [87] anterior). Compared with anterior circulation plaques, posterior circulation plaques had a larger plaque burden (77.7±15.7 versus 69.0±14.0; P=0.008), higher RR (1.14±0.38 versus 0.95±0.32; P=0.002), and more often exhibited positive remodeling (54.0% versus29.9%; P=0.011). Positive remodeling was marginally associated with downstream stroke presence when adjusted for plaque burden (odds ratio 1.34, 95% confidence interval: 0.99-1.81). CONCLUSIONS: Intracranial arteries remodel in response to plaque formation, and posterior circulation arteries have a greater capacity for positive remodeling and, consequently, may more likely elude angiographic detection. Arterial remodeling may provide insight into stroke risk.

Presurgical brain mapping of the language network in patients with brain tumors using resting-state fMRI: Comparison with task fMRI.

PURPOSE: To compare language networks derived from resting-state fMRI (rs-fMRI) with task-fMRI in patients with brain tumors and investigate variables that affect rs-fMRI vs task-fMRI concordance. MATERIALS AND METHODS: Independent component analysis (ICA) of rs-fMRI was performed with 20, 30, 40, and 50 target components (ICA20 to ICA50) and language networks identified for patients presenting for presurgical fMRI mapping between 1/1/2009 and 7/1/2015. 49 patients were analyzed fulfilling criteria for presence of brain tumors, no prior brain surgery, and adequate task-fMRI performance. Rs-vs-task-fMRI concordance was measured using Dice coefficients across varying fMRI thresholds before and after noise removal. Multi-thresholded Dice coefficient volume under the surface (DiceVUS) and maximum Dice coefficient (MaxDice) were calculated. One-way Analysis of Variance (ANOVA) was performed to determine significance of DiceVUS and MaxDice between the four ICA order groups. Age, Sex, Handedness, Tumor Side, Tumor Size, WHO Grade, number of scrubbed volumes, image intensity root mean square (iRMS), and mean framewise displacement (FD) were used as predictors for VUS in a linear regression. RESULTS: Artificial elevation of rs-fMRI vs task-fMRI concordance is seen at low thresholds due to noise. Noise-removed group-mean DiceVUS and MaxDice improved as ICA order increased, however ANOVA demonstrated no statistically significant difference between the four groups. Linear regression demonstrated an association between iRMS and DiceVUS for ICA30-50, and iRMS and MaxDice for ICA50. CONCLUSION: Overall there is moderate group level rs-vs-task fMRI language network concordance, however substantial subject-level variability exists; iRMS may be used to determine reliability of rs-fMRI derived language networks.

MR Imaging Measures of Intracranial Atherosclerosis in a Population-based Study.

Purpose To implement a magnetic resonance (MR) imaging protocol to measure intracranial atherosclerotic disease (ICAD) in a population-based multicenter study and report examination and reader reliability of these MR imaging measurements and descriptive statistics representative of the general population. Materials and Methods This prospective study was approved by the institutional review boards and compliant with HIPAA. Atherosclerosis Risk in Communities (ARIC) study participants (n = 1980) underwent brain MR imaging from 2011 to 2013 at four ARIC sites. Imaging included three-dimensional black-blood MR imaging and time-of-flight MR angiography. One hundred two participants returned for repeat MR imaging to estimate examination and reader variability. Plaque presence according to vessel segment was recorded. Quantitative measurements included lumen size and degree of stenosis, wall and/or plaque thickness, area and volume, and normalized wall index for each vessel segment. Reliability was assessed with percentage agreement, κ statistics, and intraclass correlation coefficients. Results Of the 1980 participants, 1755 (mean age, 77.6 years; 1026 women [59%]; 1234 white [70%]) completed examinations with adequate to excellent image quality. The weighted ICAD prevalence was 34.4% (637 of 1755 participants) and was higher in men than women (38.5% [302 of 729 participants] vs 31.7% [335 of 1026 participants], respectively; P = .012) and in African Americans compared with whites (41.1% [215 of 518 participants] vs 32.4% [422 of 1234 participants], respectively; P = .002). Percentage agreement of plaque identification per participant was 87.0% (interreader estimate), 89.2% (intrareader estimate), and 89.9% (examination estimate). Examination and reader reliability ranged from fair to good (κ, 0.50-0.78) for plaque presence and from good to excellent (intraclass correlation coefficient, 0.69-0.99) for quantitative vessel wall measurements. Conclusion Vessel wall MR imaging is a reliable tool for identifying and measuring ICAD and provided insight into ICAD distribution across a U.S. community-based population. (©) RSNA, 2016 Online supplemental material is available for this article.

Diffusion tensor imaging of deep gray matter in children treated for brain malignancies.

PURPOSE: Previous DTI studies reported microstructural changes in white matter of patients receiving treatment for brain malignancies. The primary aim of this prospective pilot longitudinal study was to examine if DTI can detect microstructural changes in deep gray matter (as evaluated by the apparent diffusion coefficient, ADC) between pediatric patients treated with cranial radiation therapy and typically developing healthy children. The relationship between ADC and neurobehavioral performance was also examined. METHODS: ADC was measured at 1.5 T in the caudate, putamen, globus pallidus, thalamus, and hippocampus in nine patients (mean age 11.8 years) and nine age-matched healthy controls. The study was designed with four visits: baseline, 6-month, 15-month, and 27-month follow-ups. RESULTS: Patients had 24 % higher overall mean ADC in the hippocampus compared with controls (p = 0.003). Post hoc analyses revealed significantly elevated ADC at baseline (p = 0.003) and at the 27-month follow-up (p = 0.006). Nevertheless, patients performed normally on a verbal memory test considered to be a hippocampus-related function. Relative to controls, patients' performance on the tests of the visual-spatial working memory decreased over time (group by visit, p = 0.036). Both patients and controls showed a decline in motor speed with increasing ADC in the globus pallidus and putamen. CONCLUSIONS: Childhood brain malignancies and their treatment may affect gray matter microstructure as measured by water diffusion. Significant findings in the hippocampus but not other regions suggest that differences in tissue sensitivity to disease- and treatment-related injury among gray matter regions may exist. ADC in basal ganglia may be associated with motor performance.

Determining the in vivo transverse relaxation time of GABA in the human brain at 7T.

PURPOSE: To measure in vivo transverse relaxation times (T2 ) of gamma-aminobutyric acid (GABA) at 7T using the experimental spectral-editing method. MATERIALS AND METHODS: Experiments were performed at 7T in a 10 mM GABA phantom to determine the intrinsic TE-dependence of the edited signal. Then the same method was applied with editing-based suppression of coedited macromolecular signals to five healthy volunteers to determine T2 of GABA in vivo. RESULTS: From in vivo data acquired at multiple echo times, the in vivo GABA T2 relaxation time was estimated to be 63 ± 19 msec. CONCLUSION: We present a measurement of the T2 of edited GABA signal at 7T by first using phantom measurements to determine the echo time-dependence of edited signal. The method is purely experimental and does not rely on prior knowledge of coupling constants or simulation of realistic experiments. J. Magn. Reson. Imaging 2013;38:1224-1229. © 2013 Wiley Periodicals, Inc.

Accuracy of head ultrasound for the detection of intracranial hemorrhage in preterm neonates: comparison with brain MRI and susceptibility-weighted imaging.

OBJECTIVES: To evaluate the sensitivity and specificity of head ultrasound (HUS) in the detection of intracranial hemorrhage in premature neonates compared with brain MRI using susceptibility-weighted imaging (SWI). MATERIAL AND METHODS: Ultrasound (US) and MRI scans of the brain using SWI in premature neonates were retrospectively evaluated for grade I-III germinal matrix hemorrhage (GMH), periventricular hemorrhagic infarction (PVHI), intra-axial hemorrhage other than PVHI, extra-axial hemorrhage in each cerebral hemisphere and cerebellar hemorrhage in each cerebellar hemisphere. The impact of these hemorrhagic findings on short-term clinical management was also reviewed. RESULTS: Twelve neonates (mean age: 9.8 days; range: 3-23 days) with a mean gestational age of 32.8 weeks (range: 29.6-35.4 weeks) were included in the study. HUS had high sensitivity (100%) and specificity (93.3%) in detecting grade III GMH using SWI as a reference, but poor sensitivity (0%) in the detection of intraventricular hemorrhage with normal-sized ventricles (grade II GMH). US was not sensitive in detecting either small cerebellar or extra-axial hemorrhage. CONCLUSION: HUS was highly sensitive and specific in the evaluation of grade III GMH, whereas SWI was superior to HUS in detecting small intra-axial or extra-axial hemorrhage, and had no impact on short-term management. Given the low cost, lack of radiation and advantages of bedside evaluation, HUS should continue to be the first line of imaging for brain injury in the evaluation of premature neonates with suspected intracranial hemorrhage. However, the usefulness of SWI for predicting long-term neurological outcomes has yet to be determined.

Arterial spin labeling clinical applications for brain tumors and tumor treatment complications: A comprehensive case-based review.

Arterial spin labeling (ASL) is a noninvasive neuroimaging technique that allows for quantifying cerebral blood flow without intravenous contrast. Various neurovascular disorders and tumors have cerebral blood flow alterations. Identifying these perfusion changes through ASL can aid in the diagnosis, especially in entities with normal structural imaging. In addition, complications of tumor treatment and tumor progression can also be monitored using ASL. In this case-based review, we demonstrate the clinical applications of ASL in diagnosing and monitoring brain tumors and treatment complications.

Clinical application of brain perfusion imaging in detecting stroke mimics: A review.

Stroke mimics constitute a significant proportion of patients with suspected acute ischemic stroke. These conditions may resemble acute ischemic stroke and demonstrate abnormalities on perfusion imaging sequences. The most common stroke mimics include seizure/epilepsy, migraine with aura, brain tumors, functional disorders, infectious encephalopathies, Wernicke's encephalopathy, and metabolic abnormalities. Brain perfusion imaging techniques, particularly computed tomography perfusion and magnetic resonance perfusion, are being widely used in routine clinical practice for treatment selection in patients presenting with large vessel occlusion. At the same time, the utilization of these imaging modalities enables the opportunity to better diagnose patients with stroke mimics in a time-sensitive setting, leading to appropriate management, decision-making, and resource allocation. In this review, we describe patterns of perfusion abnormalities that could discriminate patients with stroke mimics from those with acute ischemic stroke and provide specific case examples to illustrate these perfusion abnormalities. In addition, we discuss the challenges associated with interpretation of perfusion images in stroke-related pathologies. In general, perfusion imaging can provide additional information in some cases-when used in combination with conventional magnetic resonance imaging and computed tomography-and might help in detecting stroke mimics among patients who present with acute onset focal neurological symptoms.

Clinical applications of arterial spin labeling of the intracranial compartment in vascular anomalies-A case-based review.

Arterial spin labeling (ASL) is a magnetic resonance perfusion technique that allows for quantification of cerebral blood flow (CBF) without the use of contrast or radiation. Several applications of ASL have been described in diagnosis of strokes and stroke mimics, intracranial tumors, and other conditions. Various vascular anomalies exhibit specific CBF patterns that correlate with different signal intensities on ASL. In this case-based review, we demonstrate the utility of ASL in diagnosis and surveillance of vascular anomalies in the intracranial compartment.

Computed tomography perfusion stroke mimics on RAPID commercial software: A case-based review.

Acute ischemic stroke (AIS) is a leading cause of morbidity worldwide and can present with nonspecific symptoms, making diagnosis difficult. Many neurologic diseases present similarly to stroke; stroke mimics account for up to half of all hospital admissions for stroke. Stroke therapies carry risk, so accurate diagnosis of AIS is crucial for prompt treatment and prevention of adverse outcomes for patients with stroke mimics. Computed tomography (CT) perfusion techniques have been used to distinguish between nonviable tissue and penumbra. RAPID is an operator-independent, automated CT perfusion imaging software that can aid clinicians in diagnosing strokes quickly and accurately. In this case-based review, we demonstrate the applications of RAPID in differentiating between strokes and stroke mimics.

Measuring T2 in vivo with J-difference editing: application to GABA at 3 Tesla.

PURPOSE: To develop an experimental approach for determining in vivo transverse relaxation rates (T(2)) of metabolites that are detected by spectral editing without using simulations, and to demonstrate this approach to measure the T(2) of γ-aminobutyric acid (GABA). MATERIALS AND METHODS: The proposed method first determines the TE-dependence of the edited signals using measurements in a pure phantom solution (10 mM γ-aminobutyric acid; GABA); the phantom T(2) is also determined. Once the editing echo time (TE)-modulation pattern is known, it can then be used to determine T(2) in vivo. The method was applied to measure GABA T(2) in the occipital lobe of five healthy adult subjects at 3T, using a J-difference editing method. Unwanted macromolecular contributions to the GABA signal were also measured. RESULTS: The in vivo T(2) of edited GABA signal was 88 ± 12 ms; this preliminary result is somewhat shorter than other metabolite T(2) values in the literature at this field strength. CONCLUSION: Spectral editing methods are now widely used to detect low concentration metabolites, such as GABA, but to date no edited acquisition methods have been proposed for the measurement of transverse relaxation times (T(2)). The method described has been successfully applied to measuring the T(2) of GABA.

Inner ear anomalies seen on CT images in people with Down syndrome.

BACKGROUND: Although dysplasia of inner ear structures in Down syndrome has been reported in several histopathological studies, the imaging findings have not been widely studied. OBJECTIVE: To evaluate the prevalence and clinical significance of inner ear anomalies detected on CT images in patients with Down syndrome. MATERIALS AND METHODS: The temporal bone CT images of patients with Down syndrome were assessed for inner ear anomalies; clinical notes and audiograms were reviewed for hearing loss. Logistic regression models were employed to identify which CT findings were associated with sensorineural hearing loss (SNHL). RESULTS: Inner ear anomalies were observed in 74.5% (38/51) of patients. Malformed bone islands of lateral semicircular canal (LSCC), narrow internal auditory canals (IACs), cochlear nerve canal stenoses, semicircular canal dehiscence (SCCD), and enlarged vestibular aqueducts were detected in 52.5% (53/101), 24.5% (25/102), 21.4% (21/98), 8.8% (9/102) and 2% (2/101) of patients' ears, respectively. IAC stenosis had the highest odds ratio (OR = 5.37, 95% CI: 1.0-28.9, P = 0.05) for SNHL. CONCLUSION: Inner ear anomalies occurred in 74.5% of our population, with malformed (<3 mm) bone island of LSCC being the most common (52.5%) anomaly. Narrow IAC was seen in 24.5% of patients with Down syndrome and in 57.1% of ears with SNHL. High-resolution CT is a valuable for assessing the cause of hearing loss in people with Down syndrome.

Cervical ribs: identification on MRI and clinical relevance.

To determine the prevalence of cervical ribs on cervical spine MRI and clinical relevance, we reviewed 2500 studies for cervical ribs and compression of neurovascular structures and compared to CT, when available. Brachial plexus or subclavian artery contact by cervical rib was identified on MRI and/or CT in 12 cases with diagnosis of thoracic outlet syndrome in one. Cervical ribs were identified on 1.2% (25/2083) of examinations, lower than on CT (2%), but MRI may offer equivalent anatomic explanation for patient symptoms.