VESCL: an open source 2D vessel contouring library.

PURPOSE: VESCL (pronounced 'vessel') is a novel vessel contouring library for computer-assisted 2D vessel contouring and segmentation. VESCL facilitates manual vessel segmentation in 2D medical images to generate gold-standard datasets for training, testing, and validating automatic vessel segmentation. METHODS: VESCL is an open-source C++ library designed for easy integration into medical image processing systems. VESCL provides an intuitive interface for drawing variable-width parametric curves along vessels in 2D images. It includes highly optimized localized filtering to automatically fit drawn curves to the nearest vessel centerline and automatically determine the varying vessel width along each curve. To support a variety of segmentation paradigms, VESCL can export multiple segmentation representations including binary segmentations, occupancy maps, and distance fields. RESULTS: VESCL provides sub-pixel resolution for vessel centerlines and vessel widths. It is optimized to segment small vessels with single- or sub-pixel widths that are visible to the human eye but hard to segment automatically via conventional filters. When tested on neurovascular digital subtraction angiography (DSA), VESCL's intuitive hand-drawn input with automatic curve fitting increased the speed of fully manual segmentation by 22× over conventional methods and by 3× over the best publicly available computer-assisted manual segmentation method. Accuracy was shown to be within the range of inter-operator variability of gold standard manually segmented data from a publicly available dataset of neurovascular DSA images as measured using Dice scores. Preliminary tests showed similar improvements for segmenting DSA of coronary arteries and RGB images of retinal arteries. CONCLUSION: VESCL is an open-source C++ library for contouring vessels in 2D images which can be used to reduce the tedious, labor-intensive process of manually generating gold-standard segmentations for training, testing, and comparing automatic segmentation methods.

Enhancement of semantic integration reasoning by tRNS.

The right hemisphere is involved with the integrative processes necessary to achieve global coherence during reasoning and discourse processing. Specifically, the right temporal lobe has been proven to facilitate the processing of distant associate relationships, such as generating novel ideas. Previous studies showed a specific swing of alpha and gamma oscillatory activity over the right parieto-occipital lobe and the right anterior temporal lobe respectively, when people solve semantic problems with a specific strategy, i.e., insight problem-solving. In this study, we investigated the specificity of the right parietal and temporal lobes for semantic integration using transcranial Random Noise Stimulation (tRNS). We administered a set of pure semantics (i.e., Compound Remote Associates [CRA]) and visuo-semantic problems (i.e., Rebus Puzzles) to a sample of 31 healthy volunteers. Behavioral results showed that tRNS stimulation over the right temporal lobe enhances CRA accuracy (+12%), while stimulation on the right parietal lobe causes a decrease of response time on the same task (-2,100 ms). No effects were detected for Rebus Puzzles. Our findings corroborate the involvement of the right temporal and parietal lobes when solving purely semantic problems but not when they involve visuo-semantic material, also providing causal evidence for their postulated different roles in the semantic integration process and promoting tRNS as a candidate tool to boost verbal reasoning in humans.

Preliminary Results Comparing Thin Plate Splines with Finite Element Methods for Modeling Brain Deformation during Neurosurgery using Intraoperative Ultrasound.

Brain shift compensation attempts to model the deformation of the brain which occurs during the surgical removal of brain tumors to enable mapping of presurgical image data into patient coordinates during surgery and thus improve the accuracy and utility of neuro-navigation. We present preliminary results from clinical tumor resections that compare two methods for modeling brain deformation, a simple thin plate spline method that interpolates displacements and a more complex finite element method (FEM) that models physical and geometric constraints of the brain and its material properties. Both methods are driven by the same set of displacements at locations surrounding the tumor. These displacements were derived from sets of corresponding matched features that were automatically detected using the SIFT-Rank algorithm. The deformation accuracy was tested using a set of manually identified landmarks. The FEM method requires significantly more preprocessing than the spline method but both methods can be used to model deformations in the operating room in reasonable time frames. Our preliminary results indicate that the FEM deformation model significantly out-performs the spline-based approach for predicting the deformation of manual landmarks. While both methods compensate for brain shift, this work suggests that models that incorporate biophysics and geometric constraints may be more accurate.

Pneumatically driven finger movement: a novel passive functional MR imaging technique for presurgical motor and sensory mapping.

Two of the most common reasons for failure to obtain adequate preoperative functional data are inadequate task performance and excessive head motion. With an MR imaging-compatible pneumatically driven manipulandum, passive motor tasks elicited reproducible contralateral activation in the M1 and S1 in 10 healthy controls and 6 patients. The SMA was localized in all healthy controls and in 5 of 6 patients. Head motion was reduced in passive tasks compared with active tasks.

Material-specific lateralization in the medial temporal lobe and prefrontal cortex during memory encoding.

Numerous observations in patients with unilateral lesions of the medial temporal lobe (MTL) and the prefrontal cortex indicate that memory processes are lateralized according to content. Left-sided lesions interfere with verbal memory processes, whereas right-sided lesions interfere with visuospatial (non-verbal) memory processes. However, functional imaging studies have resulted in contradictory data, some studies showing lateralization in the prefrontal cortex determined by stage of processing (encoding versus retrieval) and others suggesting that lateralization is dependent on the type of material. Few studies have examined this issue in the MTL. In order to test the hypothesis that the lateralization of encoding processes in the MTL and frontal regions is dependent on the verbalizability of the material, we performed behavioural and functional imaging studies. We demonstrated differing verbalizabilities of three classes of non-verbal stimuli (scenes > faces > abstract patterns) using a dual-task verbal interference behavioural paradigm. A functional neuroimaging study of encoding was carried out using these three types of stimuli, plus words. During whole-brain functional MRI at 1.5 T, eight normal right-handed adults were presented with alternating blocks of novel and repeated stimuli under intentional memory encoding conditions. Verbal encoding resulted in left-lateralized activation of the inferior prefrontal cortex and the MTL. Pattern encoding activated the right inferior prefrontal cortex and the right MTL. Scenes and faces resulted in approximately symmetrical activation in both regions. The data indicate that the lateralization of encoding processes is determined by the verbalizability of stimuli.

Differential responses in the fusiform region to same-race and other-race faces.

Many studies have shown that people remember faces of their own race better than faces of other races. We investigated the neural substrates of same-race memory superiority using functional MRI (fMRI). European-American (EA) and African-American (AA) males underwent fMRI while they viewed photographs of AA males, EA males and objects under intentional encoding conditions. Recognition memory was superior for same-race versus other-race faces. Individually defined areas in the fusiform region that responded preferentially to faces had greater response to same-race versus other-race faces. Across both groups, memory differences between same-race and other-race faces correlated with activation in left fusiform cortex and right parahippocampal and hippocampal areas. These results suggest that differential activation in fusiform regions contributes to same-race memory superiority.

Fractionated stereotactic radiosurgery and preservation of hearing in patients with vestibular schwannoma: a preliminary report.

OBJECTIVE: Microsurgery and stereotactic radiosurgery (SRS) for vestibular schwannomas are associated with a relatively high incidence of sensorineural hearing loss. A prospective trial of fractionated SRS was undertaken in an attempt to preserve hearing and minimize incidental cranial nerve injury. METHODS: Thirty-three patients with vestibular schwannomas were treated with 2100 cGy in three fractions during a 24-hour period using conventional frame-based linear accelerator radiosurgery. The median tumor diameter was 20 mm (range, 7-42 mm). Baseline and follow-up evaluations included audiometry and contrast-enhanced magnetic resonance imaging. End points were tumor progression, preservation of serviceable hearing, and treatment-related complications. RESULTS: Thirty-one patients (32 tumors) were assessable for tumor progression and treatment-related complications and 21 patients for preservation of serviceable hearing, with a median follow-up interval of 2 years (range, 0.5-4.0 yr). Tumor regression or stabilization was documented in 30 patients (97%) and tumor progression in 1 (3%). The patient with tumor progression remains asymptomatic and has not required surgical intervention. Five patients (16%) developed trigeminal nerve injury at a median of 6 months (range, 4-12 mo) after SRS; two of these patients had preexisting trigeminal neuropathy. One patient (3%) developed facial nerve injury (House-Brackmann Class 3) 7 months after SRS. Preservation of useful hearing (Gardner-Robertson Class 1-2) was 77% at 2 years. All patients with pretreatment Gardner-Robertson Class 1 to 2 hearing maintained serviceable (Class 1-3) hearing as of their last follow-up examination. CONCLUSION: Three-fraction SRS with a conventional stereotactic frame is feasible and well tolerated in the treatment of acoustic neuroma. This study demonstrates a high rate of hearing preservation and few treatment-related complications among a relatively high-risk patient cohort (tumors >15 mm or neurofibromatosis Type 2). Longer follow-up will be required to assess the durability of tumor control.

Direct and combined revascularization in pediatric moyamoya disease.

OBJECTIVE: Surgical revascularization of moyamoya disease can improve neurological outcomes, compared with the natural history of the disease or the results of medical treatment. Controversy exists regarding whether direct or indirect revascularization yields better outcomes. This study involves a single-center experience with direct anastomosis and is the first North American series using direct revascularization for pediatric patients with moyamoya disease. METHODS: Twelve patients (age range, 5-17 yr; mean age, 10.2 yr) underwent direct revascularization of 21 hemispheres. Two patients had experienced failure of previous indirect revascularization procedures, with continued clinical deterioration. Superficial temporal artery-middle cerebral artery anastomosis was performed in 19 hemispheres (with concurrent encephaloduroarteriosynangiosis in 6). Middle meningeal artery-middle cerebral artery anastomosis and omental transposition were each performed in one hemisphere. Follow-up periods ranged from 12 to 65 months (mean, 35 mo), and monitoring included neurological examinations, angiography, magnetic resonance imaging, and cerebral blood flow studies. RESULTS: The neurological conditions of all patients were stable or improved after surgery. None of the patients developed new strokes, and no new ischemic lesions were seen in magnetic resonance imaging scans. All grafts evaluated by follow-up angiography were patent. Postoperative cerebral blood flow studies showed significantly improved blood flow (54.4 versus 42.5 ml/100 g/min; P = 0.017, n = 4) and hemodynamic reserve (70.3 versus 43.9 ml/100 g/min; P = 0.009, n = 4), compared with preoperative studies. CONCLUSION: Surgical revascularization by direct anastomosis in pediatric patients is technically feasible, is well tolerated, and can improve the progressive natural history, the angiographic appearance, and the cerebral blood flow abnormalities associated with the disease. Direct revascularization has the advantage of providing immediate and high-flow revascularization and is particularly useful for patients who have experienced failure of previous indirect revascularization procedures.

Trigeminal neuralgia resulting from infarction of the root entry zone of the trigeminal nerve: case report.

UNLABELLED: OBJECTIVE AND CLINICAL IMPORTANCE: We present a case of trigeminal neuralgia resulting from infarction of the root entry zone of the trigeminal nerve. This is the first reported case of an unusual cause of trigeminal neuralgia. CLINICAL PRESENTATION: A 71-year-old man presented with severe lancinating pain in the left V1 and V2 distributions. Magnetic resonance imaging of the brain demonstrated a small wedge-shaped infarct at the root entry zone of the left trigeminal nerve in the pons. INTERVENTION: Medical management with carbamazepine was initially successful, but the patient later developed refractory pain and was unable to tolerate side effects of the medication. The patient underwent subsequent percutaneous glycerol rhizotomy, which resulted in complete resolution of his pain. CONCLUSION: Infarction of the root entry zone may produce typical symptoms of trigeminal neuralgia similar to a multiple sclerosis plaque at the root entry zone. Treatment of trigeminal neuralgia must consider the underlying cause. Glycerol rhizotomy may provide relief of pain for patients in whom there is no evidence of vascular compression.

Detection of carotid stenosis. From NASCET results to clinical practice.

BACKGROUND AND PURPOSE: Results from large multicenter studies have shown that carotid endarterectomy, performed with low perioperative morbidity and mortality, is beneficial for patients with symptomatic carotid stenosis > or = 70% as calculated according to strict angiographic criteria. To apply these results in clinical practice, individual institutions should determine whether locally implemented duplex ultrasonography adequately identifies patients with > or = 70% stenosis and whether the degree of stenosis reported by local angiographers correlates with strict angiographic measurements. METHODS: We compared estimates of carotid stenosis obtained by duplex ultrasonography and the radiologists' reports from conventional cerebral angiography with each other and with results obtained using North American Symptomatic Carotid Endarterectomy Trial (NASCET) criteria. RESULTS: One hundred seventy-one vessels were available for review. In 155 (91%) of the cases, the reports from the ultrasound and angiogram were in agreement with regard to whether the stenosis was > or = 70% or < 70%. In 11 of the 16 cases where there was a disparity between the studies, the ultrasound was in closer agreement with measurements obtained using NASCET criteria. Nine of the angiography reports overestimated the degree of stenosis compared with NASCET measurements; twice angiography underestimated the stenosis. Twice the ultrasound underestimated the stenosis, and three times it overestimated the stenosis. CONCLUSIONS: Duplex ultrasonography was highly sensitive for detecting significant carotid stenosis at our institution; however, angiography reports often graded the degree of stenosis to be more severe than measurements obtained using NASCET criteria. Institutions that evaluate patients for carotid endarterectomy should investigate the correlation between their ultrasound and angiographic studies so that the results of carotid endarterectomy trials can be accurately applied.

Low yield of clinically significant transesophageal echocardiographic findings in patients with lacunar stroke.

Transesophageal echocardiography (TEE) is a sensitive technique for the detection of cardioembolic sources of stroke in patients with cryptogenic stroke. However, the yield of clinically significant TEE-detected abnormalities in other stroke subtypes such as lacunar stroke is unknown. We prospectively followed 145 consecutive stroke patients, including 26 patients with typical lacunar syndromes, to determine the relative risk of recurrent brain ischemia associated with TEE findings. The yield of TEE in patients with lacunar stroke syndromes was extremely low, except for a very high rate of atrial septal aneurysm (ASA). Although ASA was associated with a high risk of recurrent stroke or transient ischemic attack in patients with nonlacunar stroke, ASA was not associated with stroke recurrence in patients with lacunar stroke (p = 0.02, Cox's proportional hazard regression model). We conclude that TEE is unlikely to provide clinically relevant information in patients with typical lacunar syndromes.

Transesophageal echocardiography and carotid ultrasound in patients with cerebral ischemia: prevalence of findings and recurrent stroke risk.

OBJECTIVES: This study was conducted to determine the yield of transesophageal echocardiographic findings in a consecutive series of patients with stroke and transient ischemic attack, with and without carotid stenosis, and to estimate the recurrent stroke risk associated with specific echocardiographic findings. BACKGROUND: Transesophageal echocardiography has a high yield for identification of potential sources of cardiac embolism in patients with cerebral ischemia; however, the clinical significance of the most commonly detected abnormalities is uncertain. METHODS: We evaluated 145 consecutively admitted patients with stroke or transient ischemic attack with both transesophageal echocardiography and carotid ultrasound. Patients were followed up prospectively for a mean duration of 18 months to document the rate of recurrent cerebral ischemia. RESULTS: Transesophageal echocardiography detected at least one potential cardiac source of embolism in 45% of the patients. Atrial septal aneurysm and interatrial shunt were detected more frequently in patients who did not have a significant carotid stenosis that could account for their ischemic event. During follow-up, a higher rate of recurrent stroke or transient ischemic attack occurred in patients with positive transesophageal echocardiographic findings, particularly atrial septal aneurysm, interatrial shunt and left atrial thrombus. CONCLUSIONS: These data support recent studies that suggest that atrial septal aneurysm and interatrial shunts may be a significant source of cardioembolic stroke. Further studies are needed to clarify the optimal management of patients with these abnormalities.

Failure of high-dose heparin to prevent recurrent cardioembolic strokes in a pregnant patient with a mechanical heart valve.

A 27-year-old woman with a mechanical heart valve suffered multiple thromboembolic events while pregnant despite anticoagulation with high-dose heparin. Warfarin, the anti-coagulant of choice for patients with prosthetic heart valves, is teratogenic and can cause hemorrhagic complications at delivery. Heparin reduces thromboembolic complications, but is of uncertain efficacy. We discuss alternatives for the prevention of thromboembolic complications in pregnant women with mechanical heart valves.