Evaluation of diffusion measurements reveals radial diffusivity indicative of microstructural damage following acute, mild traumatic brain injury.

PURPOSE: Mild TBI, characterized by microstructural damage, often undetectable on conventional imaging techniques, is a pervasive condition that disturbs brain function and can potentially result in long-term deficits. Deciphering the underlying microstructural damage in mild TBI is crucial for establishing a reliable diagnosis and enabling effective therapeutics. Efforts to capture this damage have been extensive, but results have been inconsistent and incomplete. METHODS: To that effect, we set out to examine the shape of the diffusion tensor in mild TBI during the acute phase of injury. We inspected diffusivity and geometric measurements describing the diffusion tensor's shape and compared mild TBI (N = 34, 20.4-66.6 yo) measurements with those from healthy control (N = 42, 20.7-67.2 yo) participants using voxelwise tract-based spatial statistics. Subsequently, to explore associations between the diffusion measurements in mild TBI, we performed nonparametric statistics and machine learning techniques. RESULTS: Overall, mild TBI displayed a diffuse increase in Dλ2, Dλ3, Dradial, Dmean, and Cspherical, with a diffuse decrease in Afractional, Amode, and Clinear, in addition to no change in Daxial or Cplanar. Most notably, our results provide evidence for Dradial as a potential biomarker for microstructural damage, specifically its main component Dλ2, based on their performance in discriminating between mild TBI and control groups. Afractional was also found to be important for discriminating between groups. CONCLUSION: Our results revealed the importance of a diffusion measurement often overlooked, Dradial, in assessing TBI and suggest differentiating diffusion measurements has the potential utility to detect variations in the underlying pathophysiology after injury.

tbiExtractor: A framework for extracting traumatic brain injury common data elements from radiology reports.

BACKGROUND: The manual extraction of valuable data from electronic medical records is cumbersome, error-prone, and inconsistent. By automating extraction in conjunction with standardized terminology, the quality and consistency of data utilized for research and clinical purposes would be substantially improved. Here, we set out to develop and validate a framework to extract pertinent clinical conditions for traumatic brain injury (TBI) from computed tomography (CT) reports. METHODS: We developed tbiExtractor, which extends pyConTextNLP, a regular expression algorithm using negation detection and contextual features, to create a framework for extracting TBI common data elements from radiology reports. The algorithm inputs radiology reports and outputs a structured summary containing 27 clinical findings with their respective annotations. Development and validation of the algorithm was completed using two physician annotators as the gold standard. RESULTS: tbiExtractor displayed high sensitivity (0.92-0.94) and specificity (0.99) when compared to the gold standard. The algorithm also demonstrated a high equivalence (94.6%) with the annotators. A majority of clinical findings (85%) had minimal errors (F1 Score ≥ 0.80). When compared to annotators, tbiExtractor extracted information in significantly less time (0.3 sec vs 1.7 min per report). CONCLUSION: tbiExtractor is a validated algorithm for extraction of TBI common data elements from radiology reports. This automation reduces the time spent to extract structured data and improves the consistency of data extracted. Lastly, tbiExtractor can be used to stratify subjects into groups based on visible damage by partitioning the annotations of the pertinent clinical conditions on a radiology report.

Septo-optic Dysplasia : Assessment of Associated Findings with Special Attention to the Olfactory Sulci and Tracts.

PURPOSE: Septo-optic dysplasia is a congenital disorder consisting of optic nerve hypoplasia and absent septum pellucidum. While associated anomalies have been described, olfactory sulcus and bulb-tract hypoplasia have been scantily reported and was the focus of this study. METHODS: The picture archival and communications system and radiology information system (PACS-RIS) was searched over 15 years for patients with suspected septo-optic dysplasia (n = 41) and cerebral magnetic resonance imaging (MRI). Included patients had coronal (≤3 mm), axial (≤4 mm), and sagittal (≤4 mm) imaging reviewed by two staff neuroradiologists by consensus. Both olfactory sulcus and bulb-tract hypoplasia were ascribed a grade of 0 (normal) to 3 (complete hypoplasia). Other associated congenital anomalies were recorded, if present. Incidence of anomalies were compared to age-matched and gender-matched control patients. RESULTS: Out of 41 septo-optic dysplasia patients 33 were included (mean age = 120.7 months), with 8 excluded due to isolated septum pellucidum absence (n = 5), isolated bilateral optic hypoplasia (n = 2), or inadequate imaging (n = 1). An olfactory sulcus was hypoplastic on one or both sides in 14/33 (42.4%). Olfactory bulb hypoplasia was noted in one or both tracts in 15/33 (45.4%). A significant correlation was found between degree of olfactory sulcal and bulb-tract hypoplasia (ρ = 0.528, p = 0.0009). Other anomalies were: anterior falx dysplasia (n = 16, 48.5%), incomplete hippocampal inversion (n = 14, 42.4%), polymicrogyria (n = 11, 33.3%), callosal complete or partial agenesis (n = 10, 30.3%), schizencephaly (n = 8, 24.2%), ectopic posterior pituitary (n = 6, 18.2%), and nodular heterotopia (n = 4, 12.1%). Of the age-matched control patients 10/33 (30.3%) had at least mild anterior falx hypoplasia, and 1 control patient was noted to have unilateral incomplete hippocampal inversion (IHI); none of the age-matched control patients had olfactory sulcus or bulb-tract hypoplasia. CONCLUSION: Olfactory sulcus and bulb-tract hypoplasia are fairly common in septo-optic dysplasia and can be discordant between sides. Of the other associated anomalies, anterior falx dysplasia seems to be the most common.

Preliminary experience with intravenous gadoxetate disodium as a craniospinal MR contrast agent.

INTRODUCTION: Gadoxetate disodium is a gadolinium-based contrast agent (GBCA) typically used for body imaging, as about 50% of its excretion is via the liver. Its use for craniospinal MRI has not been reported. MATERIALS AND METHODS: Over a 3 years period, 31 adults underwent postcontrast MRI using gadoxetate disodium, each of whom had a relative contraindication to a GBCA, but a GBCA was deemed necessary by the clinical service to direct therapy. Postcontrast T1WI included either gradient-echo (GET1WI, n=12) or spin-echo (SET1WI, n=13) imaging. The contraindication in 29 patients was stage 3-5 chronic kidney disease (CKD) or acute kidney injury (AKI); the other two had normal kidney function, but a history of a reaction to another GBCA (vomiting in one and hypersensitivity in the other). Over a 3 years period, in those patients in whom a GBCA was both deemed necessary and had an estimated GFR (eGFR) of <40 ml/min/1.73 m(2) (i.e., stage 3-5 CKD), both informed consent and nephrology consultation was obtained. A 10 ml dose was given for cranial (n=23), spinal (n=9), and neck/face MRI (n=3), as well as craniocervical MRA (n=6). Three neuroradiologists separately evaluated for normal enhancement in 11 structures. The contrast enhancing percentage (CE%) was measured in 3 structures, and in enhancing lesions, if present. RESULTS: The pre-MRI eGFR was not significantly different from that at 30-90 days (p=0.522) in the 23 patients with an available eGFR at >90 days post-MRI; no patients developed acute kidney injury post-MRI, nor nephrogenic systemic fibrosis. Of the 11 intracranial structures scored, the superior sagittal sinus, pituitary stalk, and atrial choroid plexus enhanced in all 23 patients who underwent brain MRI, with CE%'s of 171.0%, 73.0%, and 69.8%, respectively. The number of patients with enhancing lesions were 3/23 brain MRI's, 8/9 spinal MRI's, 3/3 neck MRI's, and 2/6 craniocervical MRA/MRV's. In 9 spinal MRI's, the basivertebral plexus CE% was 213.7%; in the 7 with spondylodiscitis, the CE% measured 125.8% in enhancing epidural tissue, with a contrast-to-noise ratio (CNR) of 98.0%. CONCLUSION: This preliminary report describes the use of gadoxetate disodium as an alternative GBCA for craniospinal MRI and MRA in the renally impaired, but its efficacy in this regard must be further evaluated prospectively.

Comparison of CT perfusion summary maps to early diffusion-weighted images in suspected acute middle cerebral artery stroke.

OBJECTIVES: To assess the accuracy and reliability of one vendor's (Vital Images, Toshiba Medical, Minnetonka, MN) automated CT perfusion (CTP) summary maps in identification and volume estimation of infarcted tissue in patients with acute middle cerebral artery (MCA) distribution infarcts. SUBJECTS AND METHODS: From 1085 CTP examinations over 5.5 years, 43 diffusion-weighted imaging (DWI)-positive patients were included who underwent both CTP and DWI <12 h after symptom onset, with another 43 age-matched patients as controls (DWI-negative). Automated delay-corrected postprocessing software (DC-SVD) generated both infarct "core only" and "core+penumbra" CTP summary maps. Three reviewers independently tabulated Alberta Stroke Program Early CT scores (ASPECTS) of both CTP summary maps and coregistered DWI. RESULTS: Of 86 included patients, 36 had DWI infarct volumes ≤70 ml, 7 had volumes >70 ml, and 43 were negative; the automated CTP "core only" map correctly classified each as >70 ml or ≤70 ml, while the "core+penumbra" map misclassified 4 as >70 ml. There were strong correlations between DWI volume with both summary map-based volumes: "core only" (r=0.93), and "core+penumbra" (r=0.77) (both p<0.0001). Agreement between ASPECTS scores of infarct core on DWI with summary maps was 0.65-0.74 for "core only" map, and 0.61-0.65 for "core+penumbra" (both p<0.0001). Using DWI-based ASPECTS scores as the standard, the accuracy of the CTP-based maps were 79.1-86.0% for the "core only" map, and 83.7-88.4% for "core+penumbra." CONCLUSION: Automated CTP summary maps appear to be relatively accurate in both the detection of acute MCA distribution infarcts, and the discrimination of volumes using a 70 ml threshold.

RADPEER peer review: relevance, use, concerns, challenges, and direction forward.

RADPEER is a product developed by the ACR that aims to assist radiologists with quality assessment and improvement through peer review. The program opened in 2002, was initially offered to physician groups in 2003, developed an electronic version in 2005 (eRADPEER), revised the scoring system in 2009, and first surveyed the RADPEER membership in 2010. In 2012, a survey was sent to 16,000 ACR member radiologists, both users and nonusers of RADPEER, with the goal of understanding how to make RADPEER more relevant to its members. A total of 31 questions were used, some of which were repeated from the 2010 survey. The ACR's RADPEER committee has published 3 papers on the program since its inception. In this report, the authors summarize the survey results and suggest future opportunities for making RADPEER more useful to its membership.

Screening and detection of blunt vertebral artery injury in patients with upper cervical fractures: the role of cervical CT and CT angiography.

OBJECTIVE: To evaluate the clinical utility of nonenhanced CT (NECT)-based screening criteria and CTA in detection of blunt vertebral artery injury (BVAI) in trauma patients with C1 and/or C2 fractures. METHODS: We retrospectively reviewed the clinical records of all blunt trauma patients with C1 and/or C2 fractures between 8/2006 and 9/2011. Cervical CTA was prompted by cervical fractures involving/adjacent to a transverse foramen, and/or subluxation on NECT. Two neuroradiologists independently reviewed the CTA studies, and graded the BVAI. RESULTS: 210 patients were included; of these, 124 underwent CTA (21/124 with digital subtraction angiography, DSA), and 2 underwent DSA only. Overall, 30/126 suffered BVAI. Among 21 patients who underwent both CTA and DSA, there was 1 false negative and 1 false positive (both grade 1). There was strong interobserver agreement regarding CTA-based BVAI detection (kappa=0.93, p<0.001) and grading (kappa=0.90, p<0001). Only 3/30 BVAI patients suffered a posterior circulation stroke; none of the patients who had a negative CTA or were not selected for CTA, based on NECT screening criteria, suffered symptomatic stroke. While C1/C2 comminuted fracture was more common in patients with high grade BVAI (p=0.039), simultaneous C3-C7 comminuted fracture increased the overall BVAI risk (p=0.011). CONCLUSION: CTA reliably detects symptomatic BVAI in patients with upper cervical fractures. Utilization of NECT-based screening criteria such as transverse foraminal involvement or subluxation may be adequate in deciding whether to perform CTA, as no patients who were not selected for CTA suffered a symptomatic stroke. However, CTA may miss lower grade, asymptomatic BVAI.

Central-variant posterior reversible encephalopathy syndrome: brainstem or basal ganglia involvement lacking cortical or subcortical cerebral edema.

OBJECTIVE: Although posterior reversible encephalopathy syndrome (PRES) typically involves cortical or subcortical edema of the cerebrum, only individual cases have been described of a variant involving the central brainstem and basal ganglia and lacking cortical and subcortical edema. We evaluated FLAIR and T2-weighted images of 124 patients with confirmed PRES to determine the incidence of this uncommon variant, which we refer to as the "central variant"; to determine which structures are involved in this variant; and to determine the associated causes. CONCLUSION: We found that five of the 124 patients (4%) with PRES had MR findings consistent with the central variant-that is, either brainstem or basal ganglia involvement and a lack of cortical or subcortical edema of the cerebrum. The thalami were involved in all five PRES patients with MR findings consistent with the central variant, but there was variable involvement of the posterior limb of the internal capsule (4/5), cerebellum (3/5), and periventricular white matter (3/5); in each patient, there was improvement both clinically and on MRI. The causes of PRES in these five patients were hypertension (n=2), cyclosporine (n=2), and eclampsia (n=1). The incidence of the central variant may be increasing because of an improving awareness of the diverse imaging patterns of PRES.

Effects of intensive glucose lowering on brain structure and function in people with type 2 diabetes (ACCORD MIND): a randomised open-label substudy.

BACKGROUND: People with type 2 diabetes are at risk of cognitive impairment and brain atrophy. We aimed to compare the effects on cognitive function and brain volume of intensive versus standard glycaemic control. METHODS: The Memory in Diabetes (MIND) study was done in 52 clinical sites in North America as part of Action to Control Cardiovascular Risk in Diabetes (ACCORD), a double two-by-two factorial parallel group randomised trial. Participants (aged 55-80 years) with type 2 diabetes, high glycated haemoglobin A(1c) (HbA(1c)) concentrations (>7·5%; >58 mmol/mol), and a high risk of cardiovascular events were randomly assigned to receive intensive glycaemic control targeting HbA(1c) to less than 6·0% (42 mmol/mol) or a standard strategy targeting HbA(1c) to 7·0-7·9% (53-63 mmol/mol). Randomisation was via a centralised web-based system and treatment allocation was not masked from clinic staff or participants. We assessed our cognitive primary outcome, the Digit Symbol Substitution Test (DSST) score, at baseline and at 20 and 40 months. We assessed total brain volume (TBV), our primary brain structure outcome, with MRI at baseline and 40 months in a subset of participants. We included all participants with follow-up data in our primary analyses. In February, 2008, raised mortality risk led to the end of the intensive treatment and transition of those participants to standard treatment. We tested our cognitive function hypotheses with a mixed-effects model that incorporated information from both the 20 and 40 month outcome measures. We tested our MRI hypotheses with an ANCOVA model that included intracranial volume and factors used to stratify randomisation. This study is registered with ClinicalTrials.gov, number NCT00182910. FINDINGS: We consecutively enrolled 2977 patients (mean age 62·5 years; SD 5·8) who had been randomly assigned to treatment groups in the ACCORD study. Our primary cognitive analysis was of patients with a 20-month or 40-month DSST score: 1378 assigned to receive intensive treatment and 1416 assigned to receive standard treatment. Of the 614 patients with a baseline MRI, we included 230 assigned to receive intensive treatment and 273 assigned to receive standard treatment in our primary MRI analysis at 40 months. There was no significant treatment difference in mean 40-month DSST score (difference in mean 0·32, 95% CI -0·28 to 0·91; p=0·2997). The intensive-treatment group had a greater mean TBV than the standard-treatment group (4·62, 2·0 to 7·3; p=0·0007). INTERPRETATION: Although significant differences in TBV favoured the intensive treatment, cognitive outcomes were not different. Combined with the non-significant effects on other ACCORD outcomes, and increased mortality in participants in the intensive treatment group, our findings do not support the use of intensive therapy to reduce the adverse effects of diabetes on the brain in patients with similar characteristics to those of our participants. FUNDING: US National Institute on Aging and US National Heart, Lung, and Blood Institute.

Intraoperative magnetic resonance imaging.

Neurosurgeons have become reliant on image-guidance to perform safe and successful surgery both time-efficiently and cost-effectively. Neuronavigation typically involves either rigid (frame-based) or skull-mounted (frameless) stereotactic guidance derived from computed tomography (CT) or magnetic resonance imaging (MRI) that is obtained days or immediately before the planned surgical procedure. These systems do not accommodate for brain shift that is unavoidable once the cranium is opened and cerebrospinal fluid is lost. Intraoperative MRI (ioMRI) systems ranging in strength from 0.12 to 3 Tesla (T) have been developed in part because they afford neurosurgeons the opportunity to accommodate for brain shift during surgery. Other distinct advantages of ioMRI include the excellent soft tissue discrimination, the ability to view the surgical site in three dimensions, and the ability to "see" tumor beyond the surface visualization of the surgeon's eye, either with or without a surgical microscope. The enhanced ability to view the tumor being biopsied or resected allows the surgeon to choose a safe surgical corridor that avoids critical structures, maximizes the extent of the tumor resection, and confirms that an intraoperative hemorrhage has not resulted from surgery. Although all ioMRI systems allow for basic T1- and T2-weighted imaging, only high-field (>1.5 T) MRI systems are capable of MR spectroscopy (MRS), MR angiography (MRA), MR venography (MRV), diffusion-weighted imaging (DWI), and brain activation studies. By identifying vascular structures with MRA and MRV, it may be possible to prevent their inadvertent injury during surgery. Biopsying those areas of elevated phosphocholine on MRS may improve the diagnostic yield for brain biopsy. Mapping out eloquent brain function may influence the surgical path to a tumor being resected or biopsied. The optimal field strength for an ioMRI-guided surgical system and the best configuration for that system are as yet undecided.

Reperfusion phenomenon masking acute and subacute infarcts at dynamic perfusion CT: confirmation by fusion of CT and diffusion-weighted MR images.

OBJECTIVE: The purpose of this study was to evaluate cerebral blood flow, cerebral blood volume, mean transit time, time to peak, and delay in a selected sample of patients with visually normal or increased cerebral blood volume to facilitate detection of a postischemic CT perfusion hyperperfusion-reperfusion phenomenon that may mask subacute and acute infarcts. MATERIALS AND METHODS: Ten patients were included who had visually normal or elevated cerebral blood volume in infarcts larger than 1.5 cm confirmed on diffusion-weighted MR images within 48 hours of perfusion CT. The cases were selected from 371 perfusion CT studies of stroke patients (99 associated with positive diffusion-weighted imaging findings) reviewed over 2.5 years on a 64-MDCT scanner. The perfusion CT images were fused to the diffusion-weighted images for measurement of cerebral blood volume, cerebral blood flow, mean transit time, time to peak, and delay in each infarct versus the contralateral hemisphere. Two neuroradiologists reviewed the images in consensus. RESULTS: The mean time between symptom onset and perfusion CT was 3.9 days. Infarcts were in the middle cerebral artery (n = 7) and posterior cerebral artery (n = 3) distributions. Significant differences versus the contralateral finding were found in cerebral blood volume (p = 0.016; mean increase, 30.0%), mean transit time (p = 0.007; mean increase, 38.1%), time to peak (p = 0.005; mean increase, 17.7%), and delay (p = 0.030; mean increase, 124.9%). The difference in cerebral blood flow (p = 0.785; mean increase, 1.8%) was not statistically significant. Infarcts became enhanced on the dynamic perfusion CT images of eight of 10 patients and on the contrast-enhanced T1-weighted MR images of six of nine patients. CONCLUSION: Visual inspection of cerebral blood volume and cerebral blood flow maps alone is insufficient in the evaluation of infarcts. Mean transit time, time to peak, and delay maps also should be reviewed with dynamic source images to prevent misinterpretation of findings as false-negative. This phenomenon is unlikely to occur hyperacutely (< 8 hours after onset).

Three-tesla high-field applications.

The authors believe that 3-T intraoperative MRI (iMRI) is likely to become the standard of care for a wide range of neurosurgical procedures. Although 3-T high-field image acquisition does pose challenges, the advantages of this field strength, such as superior visualization of soft tissue and clear delineation of any residual tumor tissue, are clearly optimized using this equipment. Additionally, the use of 3-T high-field scanning offers functional options, such as brain activation studies and complex vascular imaging, that are unavailable with low- and midfield iMRI systems. The authors believe that the cost and effort necessary to acquire and establish a 3-T high-field iMRI program represent the natural progression for image-guided neurosurgery.

Functional magnetic resonance imaging-guided brain tumor resection.

OBJECTIVES: We evaluated the safety and efficacy of using functional magnetic resonance imaging (fMRI) brain activation data obtained at both 1.5 and 3 T to guide brain tumor resections using 1.5-T intraoperative MRI (ioMRI) guidance. MATERIALS AND METHODS: From January 1997 to March 2006, fMRI was performed on 29 patients before attempted brain tumor resection. Functional MRI was used to identify and coregister areas of brain activation for motor (n = 18), speech (n = 6), motor and speech (n = 4), and short-term memory and speech (n = 1) with respect to the tumor using a 1.5-T and two 3-T MRI scanners. Surgical resection was accomplished using 2 different 1.5-T ioMRI systems. The appropriate MRI scan sequences were obtained during surgery to determine and maximize the extent of the surgical resection depending on the tumor type. RESULTS: Of 29 patients, 20 (69%) had radiographically complete fMRI-guided tumor resections and 2 (7%) had successful MRI-guided brain biopsy because of the proximity of their astrocytomas to the eloquent cortex. The tumors were oligodendrogliomas (n = 16), astrocytomas (n = 4), meningiomas (n = 3), glioblastomas multiforme (n = 2), a pleomorphic astrocytoma (n = 1), and a dysembryoplastic neuroepithelial tumor (n = 1). The preoperative fMRI data were accurate in all cases. After tumor resection, 7 patients (26%) had transient neurologic deficits that resolved completely within 1 month of the surgical procedure in all cases. No adverse events associated with ferromagnetic instrumentation occurred. CONCLUSIONS: Functional MRI was accurate for localizing areas of eloquent neurologic function before ioMRI-guided brain tumor resection.

The surgical management of infections involving the cerebrum.

OBJECTIVE: Infection involving the cerebrum is a true neurosurgical emergency that requires rapid diagnosis and appropriate surgical and medical intervention to achieve good clinical outcome. METHODS: Because of the potential for devastating neurological sequelae, it is imperative that neurosurgeons be involved in the diagnosis and management of these serious conditions once an infection is suspected. With the advent of computed tomography and magnetic resonance imaging, it is now possible to detect an infectious process early in its course and follow the response to therapy. Although significantly more effective than in the past, antimicrobial therapy alone is insufficient to eradicate most intracranial infections, especially in the presence of compression or displacement of the cerebrum. Surgery remains an essential part of the management of intracranial infection because of its ability to provide immediate relief from pressure on neural structures and thereby result in clinical improvement. RESULTS: The most common infections affecting the brain, namely, cranial epidural abscess, subdural empyema, brain abscess, viral infection, tuberculosis, and neurocysticercosis, can each be associated with significant mass effect on the cerebrum that is greatly reduced through surgery. This relief, in combination with newer antimicrobial agents that have an improved ability to cross the blood brain barrier, has led to a reduction in the infection-related morbidity and mortality rates associated with intracranial infections. CONCLUSION: Combining advanced imaging and surgical techniques in the form of intraoperative magnetic resonance image-guided neurosurgery may further enhance clinical outcomes in these once uniformly fatal diseases.

Minimally invasive precision brain access using prospective stereotaxy and a trajectory guide.

PURPOSE: To evaluate the capabilities of MR-guided "prospective stereotaxy" methods for accessing brain structures for biopsy or electrode implantation. MATERIALS AND METHODS: MR-guided biopsy and deep brain stimulator (DBS) electrode implantations were performed with a trajectory guide and real-time MR guidance. Imaging methods were used to plan the selected path through the brain, appropriately orient the trajectory guide, and monitor the device insertion to assure technical success and screen for hemorrhage. Assessments of technical success rate, targeting accuracy, and complications associated with this technique were performed. RESULTS: A total of 187 biopsy procedures were performed with guidance via prospective stereotaxy methods. All brain biopsies were diagnostic and two patients sustained superficial wound infections that were treated successfully with antibiotics. One patient died postoperatively of a myocardial infarction despite preoperative medical clearance. A total of 42 DBS electrode insertions were performed in patients with Parkinson's disease or dystonia. The difference between planned and actual electrode position averaged 1.2 mm +/- 0.7 mm on the first pass and only a single brain penetration was required in 90% of electrode insertions. Complications included a single asymptomatic hemorrhage and two early infections, with the latter addressed by an adjustment to sterile practice. CONCLUSION: Prospective stereotaxy, in combination with a trajectory guide, has been proven capable of efficiently and accurately targeting structures throughout the brain.

Left ventricular diverticulosis: demonstration on cardiac CT.

Cardiac computed tomography scanning is rapidly emerging as the noninvasive modality of choice for assessment of coronary artery disease. Secondary to the exquisite resolution of the modality, left ventricular diverticula can be well demonstrated. Left ventricular diverticula are rare, and in the past, the terms diverticula and aneurysm have been used interchangeably. The differentiation of diverticula and aneurysm is crucial for appropriate management. To the best of our knowledge, this is the first report of left ventricular diverticula seen on cardiac computed tomography examination.

Intraoperative MR-guided neurosurgery.

For more than a decade neurosurgeons have become increasingly dependent on image guidance to perform safe, efficient, and cost-effective surgery. Neuronavigation is frame-based or frameless and requires obtaining computed tomography or magnetic resonance imaging (MRI) scans several days or immediately before surgery. Unfortunately, these systems do not allow the neurosurgeon to adjust for the brain shift that occurs once the cranium is open. This technical inability has led to the development of intraoperative MRI (ioMRI) systems ranging from 0.12-3.0T in strength. The advantages of ioMRI are the excellent soft tissue discrimination and the ability to view the operative site in three dimensions. Enhanced visualization of the intracranial lesion enables the neurosurgeon to choose a safe surgical trajectory that avoids critical structures, to maximize the extent of the tumor resection, and to exclude an intraoperative hemorrhage. All ioMRI systems provide basic T1- and T2-weighted imaging capabilities but high-field (1.5T) systems can also perform MR spectroscopy (MRS), MR venography (MRV), MR angiography (MRA), brain activation studies, chemical shift imaging, and diffusion-weighted imaging. Identifying vascular structures by MRA or MRV may prevent injury during surgery. Demonstrating elevated phosphocholine within a tumor may improve the diagnostic yield of brain biopsy. Mapping out neurologic function may influence the surgical approach to a tumor. The optimal strength for MR-guided neurosurgery is currently under investigation.

Unilateral hypoxic-ischemic injury in young children from abusive head trauma, lacking craniocervical vascular dissection or cord injury.

BACKGROUND: Abusive head trauma (AHT) in young children usually has a severe outcome when associated with hypoxic-ischemic encephalopathy (HIE), which is best characterized by MRI in the acute or subacute phase utilizing diffusion-weighted imaging (DWI). HIE in this setting has been hypothesized to result from stretching of the spinal cord, brainstem, or vasculature. OBJECTIVE: To provide clinical correlation in patients with unilateral HIE and to postulate a mechanism in the setting of suspected AHT. MATERIALS AND METHODS: IRB approval was obtained. Over a 5-year period, the medical records and images were reviewed of the 53 children < or = 3 years of age who presented with acute head trauma according to the hospital registry. The children were subselected in order to determine how many suffered either HIE or AHT, and to detect those with unilateral HIE. RESULTS: In 11 of the 53 children, the etiology of the head trauma was highly suspicious for abuse. In 38 the head trauma was accidental and in 4 the trauma was of unknown etiology and at the time of this report was unresolved legally. Of the 53, 4 suffered HIE confirmed by CT or MRI. In three of these four with HIE the trauma was considered highly suspicious for AHT. Two of these three were the only patients with unilateral HIE, and both (7 months and 14 months of age) presented with early subacute phase HIE seen on DW MRI (range 4-7 days) and are described in detail with clinical correlation. The third child with AHT and HIE had bilateral findings. In the fourth patient the HIE was bilateral and was considered accidental. The work-up for both patients with unilateral HIE included head CT, craniocervical MRI, and craniocervical MR angiography (MRA). In both, there was mostly unilateral, deep white matter restricted diffusion, with subdural hematomas that were small compared to the extent of hypoxic-ischemic insult, and no skull fracture. Craniocervical MRA and axial thin-section fat-saturation images were negative for dissection, brainstem, or cord injury. Legal authorities obtained a confession of inflicted injury in one and a partial confession in the second (which did not fit the extent of injury). Five other children with HIE (based on DWI) were found during this period who had not suffered head trauma; all were bilateral insults. CONCLUSION: HIE associated with AHT might present with largely unilateral white matter injury on DWI following extensive cortical infarction. We propose that unilateral HIE in a young child might be a sign of AHT and might result from cervical vascular compression, whether from kinking during hyperflexion/hyperextension or from direct strangulation.