Local control and overall survival for adjuvant stereotactic radiosurgery in patients with residual or recurrent disease.

Prior studies of post-operative stereotactic radiosurgery (SRS) have not distinguished between Adjuvant SRS (ARS) versus Adjuvant SRS to residual/recurrent disease (ARD). In this study, we defined ARS and ARD and investigated local control (LC), overall survival (OS), distant development of brain metastases (DBF), and leptomeningeal disease (LMD). We retrospectively identified BM patients who received surgical resection and SRS for BM from an IRB approved database between Jan 2009-Aug 2015. Patients were stratified into two groups: ARS and ARD. LC was determined by follow-up MRI studies and OS was measured from the date of surgery. LC and OS were assessed using the Kaplan-Meier method. 70 cavities underwent surgical resection of BM and received SRS to the post-operative bed. 41 cavities were classified as ARS and 29 as ARD. There was no significant difference in 12-month LC between the ARS and ARD group (71.4 vs. 80.8%, respectively; p = 0.135) from the time point of SRS. The overall 1-year survival for ARS and ARD was 79.9 and 86.1%, respectively (p = 0.339). Mean time to progression was 6.45 and 8.0 months and median follow-up was 10 and 15 months for ARS and ARD, respectively. 11.8% of ARS patients and 15.4% of ARD patients developed LMD, p = 0.72. 29.4% of ARS and 48.0% of ARD patients developed DBF, p = 0.145. Our findings suggest that observation after surgical resection, with subsequent treatment with SRS after the development of local failure, may not compromise treatment efficacy. If validated, this would spare patients who do not recur post-surgically from additional treatment.

Automated Segmentation of Head Computed Tomography Images Using FSL.

OBJECTIVE: The aim of this study was to investigate the use of one magnetic resonance image-processing tool, FSL, in its ability to perform automated segmentation of computed tomographic images of the brain. METHODS: Head computed tomography (CT) images were brain extracted and segmented using the FSL tools BET and FAST, respectively. The products of segmentation were analyzed by histogram. The impact of image intensity inhomogeneity correction was investigated using simulated bias fields, 14 routine head CT scans, and selected illustrative clinical cases. RESULTS: FSL FAST performs direct segmentation of head CT images, permitting quantitation of gray and white matter densities and volumes, achieving a more complete segmentation than masking methods. "Bias field correction" reduced the covariance of image signal intensities of the total brain and gray matter images (P < 0.01). Correction is larger when the effects of beam hardening and radiation scatter are larger, resulting in improved segmentation. CONCLUSIONS: FSL FAST enables direct segmentation of head CT images.

Evaluation of neonatal brain myelination using the T1- and T2-weighted MRI ratio.

PURPOSE: To validate the T1- and T2-weighted (T1w/T2w) MRI ratio technique in evaluating myelin in the neonatal brain. MATERIALS AND METHODS: T1w and T2w MR images of 10 term neonates with normal-appearing brain parenchyma were obtained from a single 1.5 Tesla MRI and retrospectively analyzed. T1w/T2w ratio images were created with a postprocessing pipeline and qualitatively compared with standard clinical sequences (T1w, T2w, and apparent diffusion coefficient [ADC]). Quantitative assessment was also performed to assess the ratio technique in detecting areas of known myelination (e.g., posterior limb of the internal capsule) and very low myelination (e.g., optic radiations) using linear regression analysis and the Michelson Contrast equation, a measure of luminance contrast intensity. RESULTS: The ratio image provided qualitative improvements in the ability to visualize regional variation in myelin content of neonates. Linear regression analysis demonstrated a significant inverse relationship between the ratio intensity values and ADC values in the posterior limb of the internal capsule and the optic radiations (R2 = 0.96 and P < 0.001). The Michelson Contrast equation showed that contrast differences between these two regions for the ratio images were 1.6 times higher than T1w, 2.6 times higher than T2w, and 1.8 times higher than ADC (all P < 0.001). Finally, the ratio improved visualization of the corticospinal tract, one of the earliest myelinated pathways. CONCLUSION: The T1w/T2w ratio accentuates contrast between myelinated and less myelinated structures and may enhance our diagnostic ability to detect myelination patterns in the neonatal brain. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage2 J. MAGN. RESON. IMAGING 2017;46:690-696.

Fluoroscopically Guided Lumbar Puncture.

OBJECTIVE: The objective of this article is to detail the indications, techniques, risks, and benefits of fluoroscopically guided lumbar puncture (LP). CONCLUSION: Familiarity with the details of fluoroscopically guided LP can aid in the work flow, increase the success rate, and minimize the complications of the procedure.

Spinal diffusion tensor imaging: a comprehensive review with emphasis on spinal cord anatomy and clinical applications.

Magnetic resonance imaging technology allows for in vivo visualization of fiber tracts of the central nervous system using diffusion-weighted imaging sequences and data processing referred to as "diffusion tensor imaging" and "diffusion tensor tractography." While protocols for high-fidelity diffusion tensor imaging of the brain are well established, the spinal cord has proven a more difficult target for diffusion tensor methods. Here, we review the current literature on spinal diffusion tensor imaging and tractography with special emphasis on neuroanatomical correlations and clinical applications.

Axial diffusivity of the corona radiata correlated with ventricular size in adult hydrocephalus.

OBJECTIVE: Hydrocephalus causes changes in the diffusion-tensor properties of periventricular white matter. Understanding the nature of these changes may aid in the diagnosis and treatment planning of this relatively common neurologic condition. Because ventricular size is a common measure of the severity of hydrocephalus, we hypothesized that a quantitative correlation could be made between the ventricular size and diffusion-tensor changes in the periventricular corona radiata. In this article, we investigated this relationship in adult patients with hydrocephalus and in healthy adult subjects. MATERIALS AND METHODS: Diffusion-tensor imaging metrics of the corona radiata were correlated with ventricular size in 14 adult patients with acute hydrocephalus, 16 patients with long-standing hydrocephalus, and 48 consecutive healthy adult subjects. Regression analysis was performed to investigate the relationship between ventricular size and the diffusion-tensor metrics of the corona radiata. Subject age was analyzed as a covariable. RESULTS: There is a linear correlation between fractional anisotropy of the corona radiata and ventricular size in acute hydrocephalus (r = 0.784, p < 0.001), with positive correlation with axial diffusivity (r = 0.636, p = 0.014) and negative correlation with radial diffusivity (r = 0.668, p = 0.009). In healthy subjects, axial diffusion in the periventricular corona radiata is more strongly correlated with ventricular size than with patient age (r = 0.466, p < 0.001, compared with r = 0.058, p = 0.269). CONCLUSION: Axial diffusivity of the corona radiata is linearly correlated with ventricular size in healthy adults and in patients with hydrocephalus. Radial diffusivity of the corona radiata decreases linearly with ventricular size in acute hydrocephalus but is not significantly correlated with ventricular size in healthy subjects or in patients with long-standing hydrocephalus.

Correlation of apparent diffusion coefficient with Ki-67 proliferation index in grading meningioma.

OBJECTIVE: A noninvasive method to predict aggressiveness of high-grade meningiomas would be desirable because it would help anticipate tumor recurrence and improve tumor management and the treatment outcomes. The Ki-67 protein is a marker of tumor proliferation, and apparent diffusion coefficient (ADC) is related to tumor cellularity. Therefore, we sought to determine whether there is a statistically significant correlation between ADC and Ki-67 values in meningiomas and whether ADC values can differentiate various meningioma subtypes. MATERIALS AND METHODS: MRI examinations and histopathology of 68 surgically treated meningiomas were retrospectively reviewed. Mean ADC values were derived from diffusion imaging. Correlation coefficients were calculated for mean ADC and Ki-67 proliferation index values using linear regression. An independent unpaired Student t test was used to compare the ADC and Ki-67 proliferation index values from low-grade and more aggressive meningiomas. RESULTS: A statistically significant inverse correlation was found between ADC and Ki-67 proliferation index for low-grade and aggressive meningiomas (r(2) = -0.33, p = 0.0039). ADC values (± SD) of low-grade meningiomas (0.84 ± 0.14 × 10(-3) mm(2)/s) and aggressive (atypical or anaplastic) meningiomas (0.75 ± 0.03 × 10(-3) mm(2)/s) were significantly different (p = 0.0495). Using an ADC cutoff value of 0.70 × 10(-3) mm(2)/s, the sensitivity for diagnosing aggressive meningiomas was 29%, specificity was 94%, positive predictive value was 67%, and negative predictive value was 75%. CONCLUSION: ADC values correlate inversely with Ki-67 proliferation index and help differentiate low-grade from aggressive meningiomas.

Apparent diffusion coefficient histogram analysis of neonatal hypoxic-ischemic encephalopathy.

BACKGROUND: Diffusion-weighted imaging is a valuable tool in the assessment of the neonatal brain, and changes in diffusion are seen in normal development as well as in pathological states such as hypoxic-ischemic encephalopathy (HIE). Various methods of quantitative assessment of diffusion values have been reported. Global ischemic injury occurring during the time of rapid developmental changes in brain myelination can complicate the imaging diagnosis of neonatal HIE. OBJECTIVE: To compare a quantitative method of histographic analysis of brain apparent coefficient (ADC) maps to the qualitative interpretation of routine brain MR imaging studies. We correlate changes in diffusion values with gestational age in radiographically normal neonates, and we investigate the sensitivity of the method as a quantitative measure of hypoxic-ischemic encephalopathy. MATERIALS AND METHODS: We reviewed all brain MRI studies from the neonatal intensive care unit (NICU) at our university medical center over a 4-year period to identify cases that were radiographically normal (23 cases) and those with diffuse, global hypoxic-ischemic encephalopathy (12 cases). We histographically displayed ADC values of a single brain slice at the level of the basal ganglia and correlated peak (s-sDav) and lowest histogram values (s-sDlowest) with gestational age. RESULTS: Normative s-sDav values correlated significantly with gestational age and declined linearly through the neonatal period (r (2) = 0.477, P < 0.01). Six of 12 cases of known HIE demonstrated significantly lower s-sDav and s-sDlowest ADC values than were reflected in the normative distribution; several cases of HIE fell within a 95% confidence interval for normative studies, and one case demonstrated higher-than-normal s-sDav. CONCLUSION: Single-slice histographic display of ADC values is a rapid and clinically feasible method of quantitative analysis of diffusion. In this study normative values derived from consecutive neonates without radiographic evidence of ischemic injury are correlated with gestational age, declining linearly throughout the perinatal period. This method does identify cases of HIE, though the overall sensitivity of the method is low.

Diffusion-tensor imaging of small nerve bundles: cranial nerves, peripheral nerves, distal spinal cord, and lumbar nerve roots--clinical applications.

OBJECTIVE: The purpose of this article is to review recent advances in diffusion-tensor imaging (DTI) and tractography of the cranial and peripheral nerves. CONCLUSION: Advances in MR data acquisition and postprocessing methods are permitting high-resolution DTI of the cranial and peripheral nerves in the clinical setting. DTI offers information beyond routine clinical MRI, and DTI findings have implications for the diagnosis and treatment of nerve disease.

Improved image quality and detection of small cerebral infarctions with diffusion-tensor trace imaging.

OBJECTIVE: The purpose of this study was to test a hypothesis that routinely performed diffusion-tensor trace imaging is of sufficient image quality and sensitivity for infarct detection to safely and routinely replace standard diffusion-weighted imaging (DWI) in the clinical setting. MATERIALS AND METHODS: Both routine DWI and 15-direction diffusion-tensor imaging (DTI) with parallel acquisition technique were obtained on all brain MRI studies from a single 1.5-T MRI scanner at a tertiary care referral center over a 1-year period, permitting direct comparison of the two different diffusion studies on the same patients (2537 studies, 365 infarct-positive studies). A subset of images was assessed for image quality and quantitatively for ability to detect brain infarctions. The total set of positive studies was reviewed qualitatively for ability to detect small cerebral infarctions. RESULTS: Fifteen-direction isotropic DWI (DTI trace images) with parallel acquisition technique resulted in consistently higher image quality with less distortion and higher image detail than routine DWI. Small infarcts were better seen, and in 12 cases, infarcts could only be seen on 15-direction isotropic diffusion-weighted images. The additional scanning time required for 15-direction isotropic DWI did not result in significantly increased motion-related reduction in image quality compared with standard DWI. CONCLUSION: Diffusion-tensor trace images obtained with parallel acquisition technique are of improved image quality and improved sensitivity for detection of small cerebral infarctions relative to standard DWI. If such DTI data are acquired, routine DWI can be omitted.

Diffusion-tensor imaging derived metrics of the corpus callosum in children with neurofibromatosis type I.

OBJECTIVE: MR morphometric studies have suggested that structural brain abnormalities including corpus callosum enlargement may, in part, explain cognitive deficits in children with neurofibromatosis type 1 (NF-1). Diffusion tensor imaging (DTI) metrics of the corpus callosum in adults with NF-1 have recently been reported, but such studies in children with NF-1 are needed. The purpose of this study was to quantify the DTI metrics at 3 T of different regions of the corpus callosum in children with NF-1. SUBJECTS AND METHODS: DTI metrics from seven consecutively identified patients with NF-1 (6 boys and 1 girl; age range, 3-17 years; average age, 7.0 years) were compared with 11 age- and sex-matched control subjects (10 boys and one girl; age range, 3-17 years; average age, 7.1 years) at 3 T. Fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity were calculated in different sections of the corpus callosum as well as whole-brain mean diffusivity. RESULTS: Comparing children with NF-1 to control subjects, there were statistically significant decreases in fractional anisotropy in the genu, anterior body, and isthmus of the corpus callosum and significant increases in radial diffusivity in the genu and anterior body. Whole-brain mean diffusivity histograms revealed significant increases in whole-brain mean diffusivity in children with NF-1. CONCLUSION: Children with NF-1 have abnormal DTI metrics, particularly in the genu, and elevated whole-brain mean diffusivity. NF-1-related microstructural abnormalities of the corpus callosum are detectable in childhood and likely persist through myelination maturation.

Magnetic resonance diffusion tensor imaging (MRDTI) of the optic nerve and optic radiations at 3T in children with neurofibromatosis type I (NF-1).

BACKGROUND: Optic pathway glioma (OPG) is a characteristic hallmark of neurofibromatosis type I (NF-I). OBJECTIVE: To evaluate the feasibility of magnetic resonance diffusion tensor imaging (MRDTI) at 3T to detect abnormalities of the optic nerves and optic radiations in children with NF-I. MATERIALS AND METHODS: 3-T MRDTI was prospectively performed in 9 children with NF-I (7 boys, 2 girls, average age 7.8 years, range 3-17 years) and 44 controls (25 boys, 19 girls, average age 8.1 years, range 3-17 years). Fractional anisotropy (FA) and mean diffusivity were determined by region-of-interest analysis for the optic nerves and radiations. Statistical analysis compared controls to NF-I patients. RESULTS: Two NF-I patients had bilateral optic nerve gliomas, three had chiasmatic gliomas and four had unidentified neurofibromatosis objects (UNOs) along the optic nerve pathways. All NF-I patients had statistically significant decreases in FA and elevations in mean diffusivity in the optic nerves and radiations compared to age-matched controls. CONCLUSION: MRDTI can evaluate the optic pathways in children with NF-I. Statistically significant abnormalities were detected in the diffusion tensor metrics of the optic nerves and radiations in children with NF-I compared to age-matched controls.

MR imaging of acute cervical spinal ligamentous and soft tissue trauma.

The increasing availability of magnetic resonance imaging (MRI) and the high sensitivity of MRI for soft tissue injury are resulting in the increased use of MRI for the evaluation of acute trauma. As cervical spine injury can have a devastating consequence, MRI is being more commonly used to evaluate cervical spine injury in the acute setting, necessitating emergent interpretation by the on-call radiologist. Unless one is formally trained in a trauma center, the MRI findings of soft tissue and ligamentous cervical spine injury may not be fully appreciated. The goal of this pictorial review is to familiarize the reader with some of the more common soft tissue, vascular, and ligamentous injuries seen on MRI of the cervical spine in the emergent setting.

The effects of the skull on CT imaging of the brain: a skull and brain phantom study.

OBJECTIVE: To investigate the effects of beam hardening by the skull on the measured radiodensity of the brain. To test a hypothesis that these effects of beam hardening are decreased using a monochromatic energy source. METHODS: Selected clinical cases were reviewed in illustration. An anthropomorphic skull and brain phantom was created and scanned in a clinical CT scanner with skull, without skull, and with hemicraniectomy. The effects of beam hardening were illustrated by scanning the phantom with mono- and poly-chromatic X-ray sources. RESULTS: In clinical cases, the HU values of the brain were consistently lower when the X-ray beam traversed the skull than when it did not. An anthropomorphic skull-and-brain phantom further demonstrated these effects, which were evident with a polychromatic energy source and absent with a virtual monochromatic energy source. CONCLUSIONS: Beam hardening by the skull lowers the measured HU values of the brain. The effects, which can impact quantitative imaging, may be mitigated by a virtual monochromatic energy source. ADVANCES IN KNOWLEDGE: Beam hardening by the skull lowers the measured radiodensity of the brain. The effects may be mitigated by a virtual monochromatic energy source.

Magnetic resonance diffusion tensor imaging and tractography of the lower spinal cord: application to diastematomyelia and tethered cord.

OBJECTIVES: To investigate the feasibility of routine clinical DTI of the lower spinal cord using high-field-strength MRI and parallel imaging, and to evaluate the utility of diffusion tensor imaging and tractography as tools for study of lower cord pathology. METHODS: Three patients with diastematomyelia, one patient with tethered cord, and six normal volunteers underwent MR imaging of the lower spine at 3 T. A 15-channel spine coil and parallel imaging were used with a six-direction single-shot echo-planar gradient echo technique. RESULTS: In normal volunteers, tractography delineated the conus and cauda equina. Tractography software permitted assessment of fractional anisotropy of the distal cord and nerve roots. In cases of tethered cord, tractography correlated with anatomical imaging. Tractography also correlated with the anatomical pathological findings in cases of diastematomyelia. CONCLUSIONS: The methods described enable routine DTI and tractography of the lower spinal cord at 3 T. Compared with conventional imaging, tractography offers additional information that may prove useful in the characterization and surgical planning for congenital lesions involving the lower spinal cord.

Magnetic resonance diffusion tensor imaging (MRDTI) and tractography in children with septo-optic dysplasia.

BACKGROUND: Septo-optic dysplasia (SOD) refers to a heterogeneous group of midline brain developmental anomalies, with optic nerve hypoplasia (ONH) being one of the morphologic correlates of the condition. Traditionally, ONH has been diagnosed on fundoscopic exam. Conventional MRI is used in cases of suspected ONH to identify associated brain abnormalities and to compare findings to the fundoscopic exam. Advances in magnetic resonance diffusion tensor imaging (MRDTI) permit in vivo, noninvasive, quantitative characterization of the entire visual pathway at 3.0 T. OBJECTIVE: To investigate the feasibility of MRDTI at 3.0 T in children with SOD to evaluate the entire visual pathway. MATERIALS AND METHODS: MRDTI at 3T was performed in two children with SOD and seven age-matched controls. Manual region-of-interest analysis was used to evaluate the tensor metrics of the optic nerves. Deterministic tractography was used to evaluate the tensor metrics of the optic radiations. RESULTS: The SOD patients demonstrated a significant decrease in anisotropy and increase in mean diffusivity of the optic nerves and radiations compared to the control subjects. CONCLUSION: This study demonstrates the feasibility of MRDTI to evaluate the entire visual pathway in children, and it demonstrates pre- and post-chiasmatic diffusion tensor abnormalities in SOD patients.

The misinterpretation rates of radiology residents on emergent neuroradiology magnetic resonance (MR) angiogram studies: correlation with level of residency training.

The purpose of this study was to determine the discrepancy rates of radiology residents interpreting emergent neck and Circle of Willis magnetic resonance angiography (MRA) studies and to detect any adverse clinical outcomes. Three hundred seventeen MRA studies given preliminary reading by radiology residents were retrospectively reviewed over a 2-year period. Discrepancies were classified as either false negatives (failure to diagnose abnormalities) or false positives (misinterpreting normal scans as abnormal). The overall discrepancy rate was 12.1% for Circle of Willis MRA and 7.9% for neck MRA. Fourth-year residents had the lowest discrepancy rates (7.7%), but this was not statistically significant. The most common misses were stenosis greater than 70% (n = 9) and aneurysm (n = 12). No adverse clinical outcome was detected mainly due to rapid turnaround time for final reporting.

Serial follow-up MRI of indeterminate cystic lesions of the pineal region: experience at a rural tertiary care referral center.

OBJECTIVE: The purpose of this study was to retrospectively assess the outcomes of temporal MRI follow-up of indeterminate cystic lesions of the pineal region. MATERIALS AND METHODS: Cases of indeterminate pineal lesions were identified by a computerized search of radiology reports at our institution from 1998 to 2007. Twenty-six indeterminate pineal lesions, one each in 26 patients (six males and 20 females), were followed in the current study. Cases were included in the study if the radiology report detailed an incidentally noted but indeterminate or worrisome cystic lesion of the pineal region and if temporal follow-up MRI was recommended by the interpreting neuroradiologist. For a case to be included in our data set, a follow-up MRI study must have been obtained at least 6 months after the initial study. RESULTS: Follow-up imaging ranged from 7 months to 8 years. Lesions ranged in description and appearance from "probable benign cyst" with typical cystic imaging features to "pineal mass" with features of solid enhancement. We found that, within the limitations of the technique, there were no significant changes in the size or character of any indeterminate pineal region lesion followed at our institution over the time interval of 1998-2007. CONCLUSION: In our study, all pineal lesions found incidentally and for which follow-up imaging had been recommended were stable over time. These data suggest that neoplastic lesions of the pineal region either are too rare or grow too slowly to be identified by traditional temporal imaging follow-up. With increasing interest in optimal allocation of health care resources, our findings suggest that incidentally identified pineal region cystic lesions, both typical and atypical, can be followed clinically.

Diffusion tensor imaging and tractography of Rasmussen encephalitis.

A 5-year-old girl presented with intractable seizures and nonfocal hemispheric slowing on EEG. Blood, urine, and CSF laboratory values were all normal. MR imaging of the brain demonstrated diffuse volume loss of the entire left hemisphere. Clinical and imaging findings were consistent with the diagnosis of Rasmussen encephalitis. Diffusion tensor imaging demonstrated increased ADC values and decreased fractional anisotropy (FA) of the affected (left) hemisphere. Tractography data showed decreased numbers of lines drawn in the affected hemisphere, with fewer lines drawn at higher FA thresholds, relative to the contralateral hemisphere, or to normal age-matched controls. Diffusion tensor imaging offers an adjunct MR imaging modality in diagnosis and monitoring of this rare condition.

Magnetic resonance diffusion tensor imaging of the optic nerves to guide treatment of pediatric suprasellar tumors.

BACKGROUND/AIMS: As a preoperative planning tool, conventional magnetic resonance (MR) imaging may have limited value in differentiating tumors from white matter tracts. MR diffusion tensor imaging (MRDTI) has become a useful tool for evaluating white matter tracts in relation to surrounding structures and has been used in surgical planning for brain tumors involving white matter. We investigated the use of DTI of the optic nerves in surgical planning for pediatric suprasellar tumors. METHODS: We present findings in 10 pediatric control patients and 2 cases of pediatric suprasellar tumors in which a routine 6-direction DTI of the brain was performed at 3 T. Postprocessing permitted the study of the diffusion tensor parameters, as well as the tractography, of the optic nerves. RESULTS: The control patients demonstrated the optimization of the technique and permitted the quantitation of fractional anisotropy and apparent diffusion coefficient values. The tumor cases demonstrated the utility of optic nerve DTI to differentiate between optic nerves and suprasellar/chiasmatic brain tumors. CONCLUSIONS: A routine 6-direction DTI of the pediatric brain at 3 T permits a detailed DTI study of the optic nerves. Optic nerve tractography can be used to aid in the evaluation and treatment of pediatric brain tumors in the area of the optic chiasm.