Multi-site study of diffusion metric variability: effects of site, vendor, field strength, and echo time on regions-of-interest and histogram-bin analyses.

It is now common for magnetic-resonance-imaging (MRI) based multi-site trials to include diffusion-weighted imaging (DWI) as part of the protocol. It is also common for these sites to possess MR scanners of different manufacturers, different software and hardware, and different software licenses. These differences mean that scanners may not be able to acquire data with the same number of gradient amplitude values and number of available gradient directions. Variability can also occur in achievable b-values and minimum echo times. The challenge of a multi-site study then, is to create a common protocol by understanding and then minimizing the effects of scanner variability and identifying reliable and accurate diffusion metrics. This study describes the effect of site, scanner vendor, field strength, and TE on two diffusion metrics: the first moment of the diffusion tensor field (mean diffusivity, MD), and the fractional anisotropy (FA) using two common analyses (region-of-interest and mean-bin value of whole brain histograms). The goal of the study was to identify sources of variability in diffusion-sensitized imaging and their influence on commonly reported metrics. The results demonstrate that the site, vendor, field strength, and echo time all contribute to variability in FA and MD, though to different extent. We conclude that characterization of the variability of DTI metrics due to site, vendor, field strength, and echo time is a worthwhile step in the construction of multi-center trials.

Multi-site Study of Diffusion Metric Variability: Characterizing the Effects of Site, Vendor, Field Strength, and Echo Time using the Histogram Distance.

MRI-based multi-site trials now routinely include some form of diffusion-weighted imaging (DWI) in their protocol. These studies can include data originating from scanners built by different vendors, each with their own set of unique protocol restrictions, including restrictions on the number of available gradient directions, whether an externally-generated list of gradient directions can be used, and restrictions on the echo time (TE). One challenge of multi-site studies is to create a common imaging protocol that will result in a reliable and accurate set of diffusion metrics. The present study describes the effect of site, scanner vendor, field strength, and TE on two common metrics: the first moment of the diffusion tensor field (mean diffusivity, MD), and the fractional anisotropy (FA). We have shown in earlier work that ROI metrics and the mean of MD and FA histograms are not sufficiently sensitive for use in site characterization. Here we use the distance between whole brain histograms of FA and MD to investigate within- and between-site effects. We concluded that the variability of DTI metrics due to site, vendor, field strength, and echo time could influence the results in multi-center trials and that histogram distance is sensitive metrics for each of these variables.

Spectrum of Clinical and Associated MR Imaging Findings in Children with Olfactory Anomalies.

BACKGROUND AND PURPOSE: The olfactory apparatus, consisting of the bulb and tract, is readily identifiable on MR imaging. Anomalous development of the olfactory apparatus may be the harbinger of anomalies of the secondary olfactory cortex and associated structures. We report a large single-site series of associated MR imaging findings in patients with olfactory anomalies. MATERIALS AND METHODS: A retrospective search of radiologic reports (2010 through 2014) was performed by using the keyword "olfactory"; MR imaging studies were reviewed for olfactory anomalies and intracranial and skull base malformations. Medical records were reviewed for clinical symptoms, neuroendocrine dysfunction, syndromic associations, and genetics. RESULTS: We identified 41 patients with olfactory anomalies (range, 0.03-18 years of age; M/F ratio, 19:22); olfactory anomalies were bilateral in 31 of 41 patients (76%) and absent olfactory bulbs and olfactory tracts were found in 56 of 82 (68%). Developmental delay was found in 24 (59%), and seizures, in 14 (34%). Pituitary dysfunction was present in 14 (34%), 8 had panhypopituitarism, and 2 had isolated hypogonadotropic hypogonadism. CNS anomalies, seen in 95% of patients, included hippocampal dysplasia in 26, cortical malformations in 15, malformed corpus callosum in 10, and optic pathway hypoplasia in 12. Infratentorial anomalies were seen in 15 (37%) patients and included an abnormal brain stem in 9 and an abnormal cerebellum in 3. Four patients had an abnormal membranous labyrinth. Genetic testing was performed in 23 (56%) and findings were abnormal in 11 (48%). CONCLUSIONS: Olfactory anomalies should prompt careful screening of the brain, skull base, and the pituitary gland for additional anomalies. Genetic testing should be considered.

Neurodevelopmental outcomes after hypothermia therapy in the era of Bayley-III.

OBJECTIVE: Bayley-III scales are currently used to evaluate outcomes of term infants following hypothermia therapy, while all before reported outcomes in this population have used Bayley-II. Our objectives were to determine the incidence of abnormal neurodevelopmental outcomes using Bayley III and the predictive value of Magnetic resonance imaging (MRI) in infants who received systemic hypothermia. STUDY DESIGN: We conducted a prospective cohort study of inborn infants who underwent hypothermia for moderate/severe neonatal encephalopathy from October 2005-November 2011. RESULT: Eighty newborns underwent hypothermia (incidence of 1/1000). Of the survivors, 89% had Bayley-III performed around 24 months of age. An abnormal outcome using Bayley-III <85 occurred in 50%, while Bayley III <70 occurred in 13%. MRI predicted Bayley III<85 with sensitivity of 73%, specificity of 84%, positive-predictive value of 84% and negative-predictive value of 74%. CONCLUSION: A Bayley-III 85 cutoff identifies a disability rate of 50%, and MRI was predictive of abnormal outcomes. Findings can be useful for counseling of families and planning of future studies using Bayley III.

Diffusion imaging of the congenitally thickened corpus callosum.

This report presents 4 subjects with congenital segmental callosal thickening, an uncommon malformation studied with MR imaging and DTI. Medical records were reviewed for genetic testing and neurodevelopmental status. Three subjects had profound developmental delay; 3 had seizures. MR imaging showed segmental thickening of the rostral and/or midcallosal body. Associated anomalies included polymicrogyria in 1 patient and optic hypoplasia in 1. DTI showed that the segmental thickening was due to anomalous longitudinal supracallosal fibers visually separable from the paired cingulum in 3 patients; in 1 patient, the cingulum was poorly formed. Genetic testing was negative for Fragile X syndrome. Microarray DNA analysis showed 3 copy losses (2q27.3, 3p21.31, 7q21.11) and 1 copy gain (8p11.23) in 1 patient, while testing in the other subject was negative for losses or gains. Potential explanations for the anomalous fibers include heterotopic cingulum, an enlarged indusium griseum, and aberrant callosal fibers.

Subependymoma of the cerebellopontine angle and prepontine cistern in a 15-year-old adolescent boy.

SUMMARY: A case of cerebellopontine angle and prepontine cistern subependymoma in a 15-year-old adolescent boy is presented with a review of the literature. Apparent diffusion coefficient values for subependymoma are reported. Differential considerations for the unusual location of this rare tumor are discussed.

Sphenoid sinus craniopharyngioma simulating mucocele.

We present a case of extracranial craniopharyngioma simulating a sphenoid sinus mucocele in a 12-year-old female who presented with progressive subacute left-sided visual disturbance. Although infrasellar craniopharyngioma is a rare entity, the presence of foci of calcification within the lesion is a useful finding for diagnosis.

Midface anomalies in children.

A variety of congenital midface anomalies occur in children. High-resolution computed tomography (CT) and magnetic resonance (MR) imaging have proved helpful in determining the nature and extent of dysplasia, thereby facilitating treatment planning. A classification system has been developed that groups these anomalies into four categories based on embryogenesis and anatomic location. These categories comprise anomalies that are related to the nasal cavity, nasofrontal region, nasolacrimal apparatus, and craniofacial syndromes. CT is the imaging modality of choice in children with possible choanal atresia, pyriform aperture stenosis, or anomalies of the nasolacrimal duct (eg, nasolacrimal duct stenosis, dacryocystoceles). MR imaging is the modality of choice in patients with congenital midface masses (eg, dermoid and epidermoid cysts, nasal gliomas, encephaloceles) and craniofacial syndromes (eg, Apert syndrome, Crouzon syndrome, Treacher Collins syndrome). In many cases, however, both CT and MR imaging are required to adequately evaluate midface anomalies. Familiarity with the characteristic imaging features of these anomalies along with knowledge of midface embryogenesis and normal developmental anatomy is essential to prevent misinterpretation of anatomic variations that may simulate disease.

The use of early postoperative MR in detecting residual juvenile cerebellar pilocytic astrocytoma.

PURPOSE: We compared visibility of residual juvenile cerebellar pilocytic astrocytomas (JPAs) on early postoperative and follow-up MR studies to determine whether early postoperative MR imaging has a valid role as a baseline study. METHODS: We reviewed the MR images of 21 consecutive children who had undergone resection of cerebellar JPA. The diagnosis of residual tumor was made on the basis of nodular enhancement that corresponded to enhancing tumor on the preoperative MR studies and/or nonenhancing nodular T2 signal that corresponded to nonenhancing tumor. Because no patient received chemotherapy or radiation therapy, abnormal T2 signal or enhancement on the early postoperative study that resolved on the follow-up study was presumed to be due to peritumoral edema and/or surgical manipulation. Nodular T2 signal and/or enhancement in the tumor bed not seen on the initial postoperative MR study but present on the subsequent MR study and unchanged on serial follow-up MR studies was presumed to represent residual tumor rather than tumor that had recurred. RESULTS: Compared with follow-up studies, the initial postoperative MR images were true-positive for residual tumor in six patients, false-positive in five, equivocal for residual tumor in four, true-negative in five, and false-negative in one. Residual tumor did not consistently enhance, and peritumoral edema and changes resulting from surgical manipulation tended to mask or simulate residual tumor. CONCLUSION: Early postoperative MR imaging is not accurate in differentiating residual JPA from postoperative changes, and the role of early postoperative MR imaging as a baseline study for comparison with further studies is questionable.

Contrast venography in young haemophiliacs with implantable central venous access devices.

To assess the risk of deep vein thrombosis in haemophiliacs with long-term central venous catheters, we studied haemophiliacs followed at our centre with implantable venous access devices (ports) in place for > 6 months. Medical records were reviewed for a history of catheter-related complications. Each patient was examined for physical stigmata of thrombosis. Patency of the vessels was evaluated by contrast venography. Of 21 males with ports, 19 had factor VIII deficiency and two factor IX deficiency. Nineteen ports were evaluable (i.e. were in place for > 6 months). Seventeen patients have their original ports in place; two ports were replaced for mechanical dysfunction (1) and recurrent infection (1). Difficulty withdrawing or infusing occurred with three ports, two of which were cleared with urokinase. Physical examination was normal on all 19 patients. Venograms were performed in 13 of 19 patients. Parents of the remaining six patients refused venography because of the need for peripheral venipuncture. One patient had a small nonocclusive thrombus on the same side as his functioning catheter, and another had minimal narrowing of the subclavian vein at the site of a prior catheter. The overall prevalence of clinically relevant upper venous system thrombosis identifiable by contrast venography was zero (95% CI, 0-23%). We conclude that haemophiliacs do not have as high a risk of thrombosis as other populations of patients with central venous catheters. The theoretical risk of thrombosis should not preclude use of central venous catheters in patients with haemophilia.

The use of inferior vena cava filters in pediatric patients for pulmonary embolus prophylaxis.

PURPOSE: To report our experience with inferior vena cava (IVC) filters in pediatric patients. METHODS: Over a 19-month period, eight low-profile percutaneously introducible IVC filters were placed in four male and four female patients aged 6-16 years (mean 11 years). Indications were contraindication to heparin in six patients, anticoagulation failure in one, and idiopathic infrarenal IVC thrombosis in one. Six of the eight devices placed were titanium Greenfield filters. One LGM and one Bird's Nest filter were also placed. Two of the filters were introduced via the right internal jugular vein by cutdown, and the remainder were placed percutaneously via the right internal jugular vein or the right common femoral vein. Patients received follow-up abdominal radiographs from 2 to 13 months after IVC filter placement. RESULTS: All filters were inserted successfully without complication. Three of the patients died during the follow-up period: two due to underlying brain tumors at 2 and 12 months and a third at 6 weeks due to progressive idiopathic renal vein and IVC thrombosis. The remaining five patients were all alive and well at follow-up without evidence of IVC thrombosis, pulmonary emboli, or filter migration. CONCLUSION: IVC filter placement using available devices for percutaneous delivery is technically feasible, safe, and effective in children.

Percutaneous transhepatic endoscopic electrohydraulic lithotripsy of biliary tract calculi after orthotopic liver transplantation.

The development of biliary tract calculi after orthotopic liver transplantation presents a unique clinical problem. Previously described techniques for removing biliary stones by shock wave lithotripsy, litholytic therapy with oral bile acids, and endoscopic mechanical extraction may be ineffective or contraindicated in liver transplant patients. For this reason, percutaneous transhepatic electrohydraulic lithotripsy (EHL) was performed using an 11 French flexible ureteroscope in two pediatric patients who developed biliary tract calculi following orthotopic liver transplant. There were no complications and postoperative follow-up over 4 years has been uneventful. To our knowledge, these represent the first reported cases of percutaneous transhepatic endoscopic EHL to fragment biliary tract stones in a transplanted liver, which for us has been a safe and effective therapeutic option.

Relapse of precursor B-cell acute lymphoblastic leukemia as an isolated central nervous system mass lesion 9 years after initial diagnosis.

Seven years after completion of chemotherapy for acute lymphoblastic leukemia, diagnosed at the age of 5 years, a black female presented with signs of increased intracranial pressure. Neuroimaging showed a large enhancing extra-axial occipital tumor mass. The resection specimen showed morphologic, cytogenetic, and immunophenotypic features consistent with relapse of the primary leukemia. Bone marrow examination was negative for malignancy. The long duration of complete remission followed by the formation of a mass in the central nervous system are highly unusual features of recurrent acute lymphoblastic leukemia.

Perflubron as a gastrointestinal MR imaging contrast agent in the pediatric population.

OBJECTIVE: To evaluate the safety and efficacy of orally administered perflubron for bowel recognition on MR imaging in a pediatric population. MATERIALS AND METHODS: A multicenter trial evaluated 39 pediatric subjects before and after ingestion of perflubron with T1-, proton-density, and T2-weighted sequences through the abdomen and/or pelvis. Post-contrast images were compared with pre-contrast images. Safety was evaluated through assessment of adverse events, clinical laboratory parameters, and vital signs. RESULTS: With regard to efficacy analysis, improvement in the percent of bowel darkened was observed for 85 % of the subjects on T1-weighted images and for 95 % of the subjects on proton-density and T2-weighted images. For images of the abdominal region, the percent of bowel darkened was improved for 90-92 % of the subjects across pulse sequences. Improvement rates for the images of the pelvic region ranged from 71 % to 100 %. For at least 75 % of the subjects, proton-density and T2-weighted images of the body and tail of the pancreas, left lobe of the liver, mesenteric fat, and pathological tissue were improved relative to predosing images. Twenty-three percent of the subjects experienced some adverse effects, most of which were minor and related to the digestive system. Clinical laboratory and vital sign evaluations revealed no trends associated with the administration of perflubron. CONCLUSION: Perflubron is a relatively safe and effective gastrointestinal MR contrast agent in the pediatric population.

Crossed cerebellar atrophy in children: a neurologic sequela of extreme prematurity.

Unilateral atrophy of a cerebellar hemisphere occurring as a sequela of ischemic or destructive injury of the contralateral cerebral hemisphere is uncommon in children. We reviewed our experience with this phenomenon and found an unexpected association with extreme prematurity and a complicated perinatal course with a poor subsequent neurologic outcome. We retrospectively identified eight children, aged 8 months to 13 years, in whom cerebellar atrophy associated with cerebral injury was diagnosed on MR or CT, and reviewed their past medical history, neurologic findings, and neuroimaging studies. Seven patients were born extremely premature, EGA 25-28 weeks, and had severe perinatal intracranial hemorrhage. Neurologic problems include severe developmental delay in seven, spastic paresis in six, and seizures in five. Neuroimaging showed severe unilateral holohemispheric atrophy in four, bilateral asymmetric holohemispheric atrophy in two, and left temporoparietal atrophy in one. Cerebellar atrophy was unilateral in five and bilateral but asymmetric in two. Gliosis of the atrophic cerebellum occurred in one patient. Sequential neuroimaging in one patient showed evolution of crossed cerebellar atrophy at 8 months of age. The final patient, a term infant, had an idiopathic perinatal left cerebral infarct. In our experience, crossed cerebellar atrophy was an uncommon manifestation of extreme prematurity complicated by severe intracranial hemorrhage and/or ischemic necrosis of white matter. The cerebellar atrophy is most often a secondary degenerative phenomenon rather than a result of direct cerebellar injury.

Subcutaneous catheter calcification in ventriculoperitoneal shunts.

In three male patients with long-standing Silastic ventriculoperitoneal shunts, a sleeve of dystrophic calcification surrounding the catheter at the thoracic inlet developed, visible on plain radiographs. Such calcification indicates degeneration and tethering of the shunt catheter. It was associated with shunt disconnection in two patients.

Comparison of gadolinium-enhanced MR and thallium-201 single photon emission computed tomography in pediatric brain tumors.

Despite its usefulness in adults with cerebral gliomas, indications for thallium-201 single-photon emission computed tomography (SPECT) in pediatric brain tumor patients are not well defined. We prospectively compared thallium SPECT with gadolinium-enhanced MR (Gd-MR) to determine if thallium SPECT provides clinically useful information that cannot be derived from Gd-MR. We studied 24 pediatric brain tumor patients, 7 at presentation and 17 during therapy. MR imaging included T2 and pre- and postgadolinium T1 images. Thallium SPECT was done within 48 h of MR imaging; thallium indices were calculated for 12 of 14 lesions which showed thallium uptake. Surgery and/or clinical follow-up are available in all patients. The tumors included pilocytic astrocytoma (7), medulloblastoma (5), brainstem glioma or glioblastoma (4), germinoma (3), optic glioma (2), mixed glioma (1), primitive neuroectodermal tumor (1), and choroid plexus carcinoma (1). Among the primary tumors, compared to MR, thallium SPECT was false-negative for tumor in 1 patient and true-positive in 6 patients. Among the patients studied while on therapy, compared to MR, thallium SPECT was true-negative for tumor in 7, true-positive in 5, false-negative in 3, and false-positive in 2. In both groups of patients, thallium SPECT underestimated tumor burden as nonenhancing regions of the tumors were not thallium-avid. Thallium indices did not correlate with histologic grade, biologic aggressiveness, or tumor type. We were unable to establish indications for the use of thallium SPECT in this setting as there was little clinically useful information derived from thallium SPECT that was not provided by Gd-MR.

Neonatal stroke: clinical characteristics and cerebral blood flow velocity measurements.

The clinical courses of 8 term infants with focal cerebral infarction or neonatal stroke were studied to determine whether such infants can be identified by current markers of perinatal distress, and whether changes in cerebral blood flow velocity (CBFV) occur during the acute phase of the disease. CBFV was measured from the middle cerebral artery (MCA) and anterior cerebral artery (ACA) utilizing duplex Doppler. Seven of the 8 patients required no resuscitation in the delivery room; 1 infant required brief bag and mask ventilation. No infant had evidence of severe fetal acidemia (i.e., cord pH < 7). All 8 infants were initially admitted to the newborn nursery. Infants were identified on the basis of abnormal clinical findings observed during the first 48 hours: seizures (n = 6) and hypotonia and apnea (n = 2). Serum electrolytes, calcium, magnesium, and glucose levels were normal, and the sepsis evaluation including a spinal tap was sterile in all patients. Neuroimaging revealed nonhemorrhagic left focal MCA infarction (n = 6) and right focal MCA infarction (n = 2). Duplex Doppler demonstrated transient ipsilateral decreases in CBFV as compared to the contralateral unaffected side at clinical presentation in 4 infants. In 2 of these infants the decrease in CBFV involved both the MCA and ACA, and in 2 infants, only the MCA vessels. These side-to-side differences were not present at subsequent CBFV measurements. The data indicate that infants who develop neonatal stroke cannot be distinguished from infants who do not develop the lesion by current markers of perinatal distress.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of early MR in the evaluation of the term infant with seizures.

PURPOSE: To define the role of MR in evaluating term neonates with seizures the most common clinical manifestation of cerebral injury in neonates. METHODS: Fifteen term infants with seizures underwent MR imaging. The presence and pattern of MR findings were compared with clinical markers of perinatal distress, cause of cerebral injury, and short-term neurologic outcome. RESULTS: Seizures were caused by hypoxic-ischemic encephalopathy in three patients, bacterial meningitis in three, and prenatal cocaine exposure in one. Nine patients had no identifiable risk factors. By MR, five patients had focal ischemic injury of the cerebral hemispheres and/or basal ganglia and brain stem. Six patients had diffuse cerebral edema: of these, five had basal ganglia edema; one had brain stem edema. One patient had superior sagittal sinus thrombosis with venous infarcts. Three patients had normal MR studies. There was no correlation between markers of perinatal distress, risk factors for seizures, and presence or pattern of MR findings. There was some correlation between MR findings of diffuse cerebral injury and neurologic outcome, and between MR findings of basal ganglia and brain stem abnormalities and neurologic outcome; these findings correlated with spasticity and hemiplegia at 6 to 24 months follow-up. CONCLUSION: The presence or pattern of MR findings does not appear to correlate with with clinical signs of perinatal distress or presumed causes of perinatal cerebral injury. Further investigation is needed to identify prospectively neonates with seizures who are at risk for significant neurologic morbidity.