Tremor Relief and Structural Integrity after MRI-guided Focused US Thalamotomy in Tremor Disorders.

Background MRI-guided focused US thalamotomy of ventral intermediate nucleus of the thalamus is a treatment for tremor disorders. Purpose To evaluate white matter integrity before and after thalamotomy and its correlation with clinical outcome. Materials and Methods Participants with essential tremor (ET) or Parkinson disease (PD) undergoing thalamotomy were prospectively recruited between March 2016 and October 2018. Tremor and quality of life were assessed before, 1 month after, and 6 months after thalamotomy. Participants underwent T1-weighted, T2-weighted fluid-attenuated image recovery, and diffusion-tensor MRI before and 1 day, 7-10 days, 1-3 months, and 6 months or longer after treatment. Diffusivity and fiber tractography measures were calculated. Repeated measures analysis of variance with post hoc paired t test and Skillings-Mack test with post hoc Wilcoxon signed-rank test were used for normally and nonnormally distributed data, respectively, and Bonferroni method corrected for multiple comparisons. Results Twenty-two study participants with ET (mean age, 72 years ± 6 [standard deviation]; 14 men), 17 participants with PD (mean age, 65 years ± 8; 13 men), and a replication set of 17 participants with ET (mean age, 73 years ± 6; 10 men) were evaluated. Long-term damage was found in the ablated core (mean fractional anisotropy [FA] at baseline, 0.41 ± 0.10, and at ≥6 months, 0.23 ± 0.09; P < .001) and thalamus to red nucleus tract (mean number of tracts at baseline, 1663, and at ≥6 months, 1070; P = .003). Negative correlation was observed between motor thalamus FA 1 day after ablation and tremor improvement (ET: R = -0.52 [P = .03]; PD: R = -0.61 [P = .003]). Better tremor relief in ET was associated with lower fractional anisotropy before treatment (R = -0.5; P = .02). Conclusion MRI-guided focused US thalamotomy resulted in short- and long-term white-matter changes. Diffusion-tensor imaging provided evidence for long-term damage in the ablation core and in the thalamus and red nucleus tract, and a correlation between preablation fractional anisotropy in the motor thalamus and clinical outcome. © RSNA, 2020 Online supplemental material is available for this article.

Long-term effects of brief hypoxia due to cardiac arrest: Hippocampal reductions and memory deficits.

OBJECTIVE: To examine the effects of brief hypoxia (<7 min) due to cardiac arrest on the integrity of the brain and performance on memory and executive functions tasks. METHODS: Patients after out-of-hospital cardiac arrest (CA) (n = 9), who were deemed neurologically intact on discharge, were compared to matched patients with myocardial infarction (MI) (n = 9). A battery of clinical and experimental memory and executive functions neuropsychological tests were administered and MRI scans for all patients were collected. Measures of subcortical and cortical volumes and cortical thickness were obtained using FreeSurfer. Manual segmentations of the hippocampus were also performed. APACHE-II scores were calculated based on metrics collected at admission to ICCU for all patients. RESULTS: Significant differences between the two groups were observed on several verbal memory tests. Both hippocampi were significantly reduced (p < 0.05) in the CA patients, relative to MI patients. Hippocampal subfields segmentation showed significantly reduced presubiculum volumes bilaterally. CA patients had on average 10% reduction in volumes bilaterally across hippocampal subfields. No cortical thickness differences survived correction. Significant correlations were observed in the CA group only between the hippocampal volumes and performance on verbal memory tasks, including recollection. Hippocampal volumes and several memory measures (but not other cognitive domains) were strongly correlated with APACHE-II scores on admission in the CA group, but not in the MI group CONCLUSIONS: Chronic patients with cardiac arrest who were discharged from hospital in "good neurological condition" showed an average of 10% reduction in hippocampal volume bilaterally and significant verbal memory deficits relative to matched controls with myocardial infarction, suggesting even brief hypoxic periods suffice to lead to specific hippocampal damage.

Magnetic resonance-guided focused ultrasound thalamotomy for tremor: a report of 30 Parkinson's disease and essential tremor cases.

OBJECTIVE Thalamotomy of the ventral intermediate nucleus (VIM) is effective in alleviating medication-resistant tremor in patients with essential tremor (ET) and Parkinson's disease (PD). MR-guided focused ultrasound (MRgFUS) is an innovative technology that enables noninvasive thalamotomy via thermal ablation. METHODS Patients with severe medication-resistant tremor underwent unilateral VIM thalamotomy using MRgFUS. Effects on tremor were evaluated using the Clinical Rating Scale for Tremor (CRST) in patients with ET and by the motor part of the Unified Parkinson's Disease Rating Scale (UPDRS) in patients with PD and ET-PD (defined as patients with ET who developed PD many years later). Quality of life in ET was measured by the Quality of Life in Essential Tremor (QUEST) questionnaire and in PD by the PD Questionnaire (PDQ-39). RESULTS Thirty patients underwent MRgFUS, including 18 with ET, 9 with PD, and 3 with ET-PD. The mean age of the study population was 68.9 ± 8.3 years (range 46-87 years) with a mean disease duration of 12.1 ± 8.9 years (range 2-30 years). MRgFUS created a lesion at the planned target in all patients, resulting in cessation of tremor in the treated hand immediately following treatment. At 1 month posttreatment, the mean CRST score of the patients with ET decreased from 40.7 ± 11.6 to 9.3 ± 7.1 (p < 0.001) and was 8.2 ± 5.0 six months after treatment (p < 0.001, compared with baseline). Average QUEST scores decreased from 44.8 ± 12.9 to 13.1 ± 13.2 (p < 0.001) and was 12.3 ± 7.2 six months after treatment (p < 0.001). In patients with PD, the mean score of the motor part of the UPDRS decreased from 24.9 ± 8.0 to 16.4 ± 11.1 (p = 0.042) at 1 month and was 13.4 ± 9.2 six months after treatment (p = 0.009, compared with baseline). The mean PDQ-39 score decreased from 38.6 ± 16.8 to 26.1 ± 7.2 (p = 0.036) and was 20.6 ± 8.8 six months after treatment (p = 0.008). During follow-up of 6-24 months (mean 11.5 ± 7.2 months, median 12.0 months), tremor reappeared in 6 of the patients (2 with ET, 2 with PD, and 2 with ET-PD), to a lesser degree than before the procedure in 5. Adverse events that transiently occurred during sonication included headache (n = 11), short-lasting vertigo (n = 14) and dizziness (n = 4), nausea (n = 3), burning scalp sensation (n = 3), vomiting (n = 2) and lip paresthesia (n = 2). Adverse events that lasted after the procedure included gait ataxia (n = 5), unsteady feeling (n = 4), taste disturbances (n = 4), asthenia (n = 4), and hand ataxia (n = 3). No adverse event lasted beyond 3 months. Patients underwent on average 21.0 ± 6.9 sonications (range 14-45 sonications) with an average maximal sonication time of 16.0 ± 3.0 seconds (range 13-24 seconds). The mean maximal energy reached was 12,500 ± 4274 J (range 5850-23,040 J) with a mean maximal temperature of 56.5° ± 2.2°C (range 55°-60°C). CONCLUSIONS MRgFUS VIM thalamotomy to relieve medication-resistant tremor was safe and effective in patients with ET, PD, and ET-PD. Current results emphasize the superior adverse events profile of MRgFUS over other surgical approaches for treating tremor with similar efficacy. Large randomized studies are needed to assess prolonged efficacy and safety.

Joubert Syndrome in French Canadians and Identification of Mutations in CEP104.

Joubert syndrome (JBTS) is a primarily autosomal-recessive disorder characterized by a distinctive mid-hindbrain and cerebellar malformation, oculomotor apraxia, irregular breathing, developmental delay, and ataxia. JBTS is a genetically heterogeneous ciliopathy. We sought to characterize the genetic landscape associated with JBTS in the French Canadian (FC) population. We studied 43 FC JBTS subjects from 35 families by combining targeted and exome sequencing. We identified pathogenic (n = 32 families) or possibly pathogenic (n = 2 families) variants in genes previously associated with JBTS in all of these subjects, except for one. In the latter case, we found a homozygous splice-site mutation (c.735+2T>C) in CEP104. Interestingly, we identified two additional non-FC JBTS subjects with mutations in CEP104; one of these subjects harbors a maternally inherited nonsense mutation (c.496C>T [p.Arg166*]) and a de novo splice-site mutation (c.2572-2A>G), whereas the other bears a homozygous frameshift mutation (c.1328_1329insT [p.Tyr444fs*3]) in CEP104. Previous studies have shown that CEP104 moves from the mother centriole to the tip of the primary cilium during ciliogenesis. Knockdown of CEP104 in retinal pigment epithelial (RPE1) cells resulted in severe defects in ciliogenesis. These observations suggest that CEP104 acts early during cilia formation by regulating the conversion of the mother centriole into the cilia basal body. We conclude that disruption of CEP104 causes JBTS. Our study also reveals that the cause of JBTS has been elucidated in the great majority of our FC subjects (33/35 [94%] families), even though JBTS shows substantial locus and allelic heterogeneity in this population.

MRI Guided Focused Ultrasound Thalamotomy for Moderate-to-Severe Tremor in Parkinson's Disease.

Background. Thalamotomy is effective in alleviating tremor in Parkinson's disease (PD). Methods. Seven PD patients, mean age 59.4 ± 9.8 years (range, 46-74) with a mean disease duration of 5.4 ± 2.8 years (range, 2-10) suffering from severe refractory tremor, underwent ventral intermediate nucleus thalamotomy using MRI guided focused ultrasound (MRgFUS), an innovative technology that enables noninvasive surgery. Results. Tremor stopped in the contralateral upper extremity in all patients immediately following treatment. Total UPDRS decreased from 37.4 ± 12.2 to 18.8 ± 11.1 (p = 0.007) and PDQ-39 decreased from 42.3 ± 16.4 to 21.6 ± 10.8 (p = 0.008) following MRgFUS. These effects were sustained (mean follow-up 7.3 months). Adverse events during MRgFUS included headache (n = 3), dizziness (n = 2), vertigo (n = 4), and lip paresthesia (n = 1) and following MRgFUS were hypogeusia (n = 1), unsteady feeling when walking (n = 1, resolved), and disturbance when walking tandem (n = 1, resolved). Conclusions. Thalamotomy using MRgFUS is safe and effective in PD patients. Large randomized studies are needed to assess prolonged efficacy and safety.

A deep penetrating facial congenital melanocytic tumor with bone involvement and ipsilateral eye blindness.

Bone involvement has been described in tumors with melanocytic differentiation such as melanotic neuroectodermal tumor of infancy, and very rarely in cellular blue nevi and neurocristic cutaneous hamartoma. We present an unusual case of facial congenital melanocytic tumor that involved the underlying bones and maxillary sinus and led to unilateral blindness. A newborn with a large red bluish patch with peripheral brown and black macules overlying marked swelling on the left side of his face was presented. The tumor was shown by magnetic resonance imaging, scintigraphy, and histopathology to invade the underlying bones and maxillary sinus and to compress the left eyeball resulting in blindness. Histopathology, immunohistochemistry, morphometric computerized microscopy, molecular genetic mutation analysis, and fluorescent in situ hybridization studies were more congruent with a melanocytic nevus. An 8.5-year follow-up was uneventful, with spontaneous partial shrinkage of the tumor.

Clinical and imaging findings in patients with neurosyphilis: a study of a cohort and review of the literature.

BACKGROUND: Most patients with neurosyphilis are considered asymptomatic. The diagnosis is challenging and the role of neuroimaging is not yet well established. The present study was conducted to focus on the clinical findings and further characterize the imaging features of the disease, along with a review of the pertinent literature. METHODS: Six male patients with neurosyphilis based on abnormal cerebrospinal fluid findings, five of whom were asymptomatic at presentation, underwent cranial computerized tomography (CT) and magnetic resonance imaging (MRI). They also underwent a complete physical, neurological, and ophthalmological examination, with special attention paid to atherosclerotic vascular risk factors. In addition, all were examined for cardiac involvement using electrocardiography and cardiac ultrasound. RESULTS: The meticulous neurological and ophthalmological examination revealed abnormalities in five patients, most commonly cranial nerve involvement (three patients) and hemiparesis (two patients). The CT and MRI studies revealed abnormalities in five of the six patients, and in all six patients, respectively. The most common findings were brain infarcts, which were demonstrated in four of the six patients. MRI was found to be more sensitive than CT in detecting these brain infarcts, as expected. CONCLUSIONS: Vascular insult was the most common neuroimaging finding in our patients with neurosyphilis, probably due to meningovascular endarteritis. Neurosyphilis should always be considered in young patients with unexplained brain infarcts.

Subependymal mass lesions and peripheral polyneuropathy in adult-onset glutaric aciduria type I.

Glutaric aciduria type I (GA-I) is an autosomal recessive disease caused by a deficiency of the mitochondrial enzyme glutaryl CoA dehydrogenase (GCDH). This metabolic block causes increased urinary concentrations of glutaric and 3-hydroxyglutaric acids. The accumulation and excretion of glutarylcarnitine esters leads to secondary carnitine deficiency. GA-I has an incidence of 1:30,000. The clinical hallmark of GA-I is an acute encephalopathic crisis, with bilateral striatal necrosis presented by severe dystonic dyskinetic disorder. Most patients have their first symptoms during infancy, but some have a less severe form of the disease and some may even remain asymptomatic.

A prospective evaluation of a protocol for magnetic resonance imaging of patients with implanted cardiac devices.

BACKGROUND: Magnetic resonance imaging (MRI) is avoided in most patients with implanted cardiac devices because of safety concerns. OBJECTIVE: To define the safety of a protocol for MRI at the commonly used magnetic strength of 1.5 T in patients with implanted cardiac devices. DESIGN: Prospective nonrandomized trial. (ClinicalTrials.gov registration number: NCT01130896) SETTING: One center in the United States (94% of examinations) and one in Israel. PATIENTS: 438 patients with devices (54% with pacemakers and 46% with defibrillators) who underwent 555 MRI studies. INTERVENTION: Pacing mode was changed to asynchronous for pacemaker-dependent patients and to demand for others. Tachyarrhythmia functions were disabled. Blood pressure, electrocardiography, oximetry, and symptoms were monitored by a nurse with experience in cardiac life support and device programming who had immediate backup from an electrophysiologist. MEASUREMENTS: Activation or inhibition of pacing, symptoms, and device variables. RESULTS: In 3 patients (0.7% [95% CI, 0% to 1.5%]), the device reverted to a transient back-up programming mode without long-term effects. Right ventricular (RV) sensing (median change, 0 mV [interquartile range {IQR}, -0.7 to 0 V]) and atrial and right and left ventricular lead impedances (median change, -2 Ω [IQR, -13 to 0 Ω], -4 Ω [IQR, -16 to 0 Ω], and -11 Ω [IQR, -40 to 0 Ω], respectively) were reduced immediately after MRI. At long-term follow-up (61% of patients), decreased RV sensing (median, 0 mV, [IQR, -1.1 to 0.3 mV]), decreased RV lead impedance (median, -3 Ω, [IQR, -29 to 15 Ω]), increased RV capture threshold (median, 0 V, IQR, [0 to 0.2 Ω]), and decreased battery voltage (median, -0.01 V, IQR, -0.04 to 0 V) were noted. The observed changes did not require device revision or reprogramming. LIMITATIONS: Not all available cardiac devices have been tested. Long-term in-person or telephone follow-up was unavailable in 43 patients (10%), and some data were missing. Those with missing long-term capture threshold data had higher baseline right atrial and right ventricular capture thresholds and were more likely to have undergone thoracic imaging. Defibrillation threshold testing and random assignment to a control group were not performed. CONCLUSION: With appropriate precautions, MRI can be done safely in patients with selected cardiac devices. Because changes in device variables and programming may occur, electrophysiologic monitoring during MRI is essential.

Successful cervical MR scan in a patient several hours after pacemaker implantation.

Recent data showed that patients with electrical implanted devices may under certain conditions be scanned safely by magnetic resonance imaging (MRI). The device must have been in place preferably for at least 4-8 weeks [Correction added after online publication 31-Aug-2009: number of weeks has been updated.] prior to MR imaging to allow healing and pacemaker pocket formation. We report on a patient with quadriplegia and suspected epidural hematoma referred for MR scan a day after he had a pacemaker implantation. The patient was also pacemaker-dependent. After considering the risk/benefit ratio in this patient, it was decided to perform the scan. The pacemaker was reprogrammed. MRI was performed under strict monitoring. A spinal cord contusion at the level of C1-3 was diagnosed. Based on the imaging findings no invasive procedure was done. Device interrogation found no change in sensing or pacing parameters or in the pacemaker's battery. At the end of the scan, the device was reprogrammed back to the initial settings. In this population, each scan should be discussed thoroughly and the risks to benefit ratio should be considered. Given appropriate precautions, in well-experienced imaging centers, MRI may be safely performed in patients with permanent cardiac electronic implantable devices.

Perfusion-CT for early assessment of traumatic cerebral contusions.

INTRODUCTION: To investigate the value of perfusion-CT (PCT) for assessment of traumatic cerebral contusions (TCC) and to compare the abilities of early noncontrast CT and PCT modalities to evaluate tissue viability. METHODS: PCT studies performed in 30 patients suffering from TCC during the acute phase of their illness were retrospectively reviewed. Cerebral blood flow (CBF), volume (CBV) and mean transit time (MTT) were measured in three different areas: the hemorrhagic core of the TCC, the surrounding hypodense area and the perilesional normal-appearing parenchyma. TCC area was measured on CBF-, CBV- and MTT-derived maps and compared with the areas measured using the same slice obtained with CT scans performed on admission, at the time of PCT (follow-up CT) and at 1 week. RESULTS: TCC were characterized by low CBF and CBV values (9.2+/-6.6 ml/100 g per min and 0.9+/-0.7 ml/100 g, respectively) and a significant prolongation of MTT (11.9+/-10.7 s) in the hemorrhagic core whereas PCT parameters were more variable in the hypodense area. The TCC whole area showed a noticeable growth of the lesions during the first week of admission. In comparison with early noncontrast CT, CBV and CBF maps proved to be more congruent with the findings of noncontrast CT scans at 1 week. CONCLUSION: PCT confirmed the results of xenon-CT studies and was shown to allow better evaluation of tissue viability than noncontrast CT. These findings suggest that PCT could be implemented in the future for the early assessment of patients with traumatic brain injury.

Clinical significance of isolated mega cisterna magna.

OBJECTIVE: The prevalence and clinical significance of isolated mega cisterna magna in both fetuses and adults is not yet well defined. It is therefore difficult to provide reliable parental counseling in cases of a fetal sonographic diagnosis of this anomaly. The aim of the present study was to, determine the cognitive profile of adults with isolated mega cisterna magna. METHODS: We reviewed 19,301 consecutive CT/MRI of the brain. Isolated mega cisterna magna was observed in 49 cases. A battery of neuropsychological tests was performed in 18 adults with this anomaly and in 18 controls who had no brain anomaly on CT/MRI. RESULTS: Subjects with isolated mega cisterna magna had a lower performance on memory tasks [RAVLT saving score (0.8 +/- 0.2 vs. 1.02 +/- 0.2, P = 0.003)] and verbal fluency [phonemic fluency (9.4 +/- 4.5 vs. 13.6 +/- 5.3, P = 0.02), semantic fluency (19.8 +/- 5.8 vs. 24.4 +/- 7.5, P = 0.05)]. They did not differ from controls in regard to the Raven similarity tests indicating that this brain anomaly is not associated with impairment of general cognitive abilities. CONCLUSION: Adults with isolated mega cisterna have an overall normal cognitive functioning but may score inferior to controls on some parameters of memory and verbal fluency. Although application of adult cases to the fetuses is not well established, this information might be of value in parental counseling in cases of a fetus with this anomaly.

Cerebral perfusion computerized tomography: influence of reference vessels, regions of interest and interobserver variability.

INTRODUCTION: There are still no standardized guidelines for perfusion computerized tomography (PCT) analysis. METHODS: A total of 61 PCT studies were analyzed using either the anterior cerebral artery (ACA) or the middle cerebral artery (MCA) as the arterial reference, and the superior sagittal sinus (SSS) or the vein of Galen (VG) as the venous reference. The sizes of regions of interest (ROI) were investigated comparing PCT results obtained using a hemispheric ROI combined with vascular pixel elimination with those obtained using five smaller ROIs located over the cortex and basal ganglia. In addition, interobserver variations were explored using a standardized protocol. RESULTS: MCA-based measurements of cerebral blood flow (CBF) and blood volume (CBV) were in accordance with those obtained with the ACA except in 16 patients with ischemic stroke, in whom CBF was overestimated by the ipsilateral MCA. Venous maximal intensity was significantly lower with the VG when compared with the SSS, resulting in overestimation of CBF and CBV. However, in 13.3% of patients the VG ROI yielded higher maximal intensities than the SSS ROI. There was no difference in PCT results between hemispheric ROI and averaged separate ROI when vascular pixel elimination was used. Finally, interobserver variations were as high as 11% for CBF and 12% for CBV. CONCLUSION: The present results suggest that pathological rather than anatomical considerations should dictate the choice of the arterial ROI. For venous ROI, although SSS seems to be adequate in most instances, deep cerebral veins may occasionally generate higher maximal intensities and should therefore be selected. Importantly, significant user-dependency should be taken into account.

Magnetic resonance imaging for patients with permanent pacemakers: initial clinical experience.

BACKGROUND: Magnetic resonance imaging is a diagnostic tool of growing importance. Since its introduction, certain medical implants, e.g., pacemakers, were considered an absolute contraindication, mainly due to the presence of ferromagnetic components and the potential for electromagnetic interference. Patients with such implants were therefore prevented from entering MRI systems and not studied by this modality. These devices are now smaller and have improved electromechanical interference protection. Recently in vitro and in vivo data showed that these devices may be scanned safely by MRI. OBJECTIVES: To report our initial experience with three patients with pacemakers who underwent cerebral MRI studies. METHODS: The study included patients with clear clinical indications for MRI examination and who had implanted devices shown to be safe by in vitro and in vivo animal testing. In each patient the pacemaker was programmed to pacing-off. During the scan, continuous electrocardiographic telemetry, breathing rate, pulse oximetry and symptoms were monitored. Specific absorption rate was limited to 4.0 W/kg for all sequences. Device parameters were assessed before, immediately after MRI, and 1 week later. RESULTS: None of the patients was pacemaker dependent. During the MRI study, no device movement was felt by the patients and no episodes of inappropriate inhibition or rapid activation of pacing were observed. At device interrogation there were no significant differences in device parameters pre-, post-, and 1 week after MRI. Image quality was unremarkable in all imaging sequences used and was not influenced by the presence of the pacemaker. CONCLUSION: Given appropriate precautions, MRI can be safely performed in patients with a selected permanent pacemaker. This may have significant implications for current MRI contraindications.

Segmentation of thin structures in volumetric medical images.

We present a new segmentation method for extracting thin structures embedded in three-dimensional medical images based on modern variational principles. We demonstrate the importance of the edge alignment and homogeneity terms in the segmentation of blood vessels and vascular trees. For that goal, the Chan-Vese minimal variance method is combined with the boundary alignment, and the geodesic active surface models. An efficient numerical scheme is proposed. In order to simultaneously detect a number of different objects in the image, a hierarchal approach is applied.

Role of multisection CT angiography in the evaluation of vertebrobasilar vasospasm in patients with subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: Optimal means for assessing cerebral vasospasm, mainly at the vertebrobasilar system, have not been established. The purpose of this study was to evaluate the role of multisection CT angiography (MCTA) in the detection and quantification of vertebrobasilar vasospasm (VBS) indicated on transcranial Doppler (TCD) imaging in patients with subarachnoid hemorrhage (SAH). METHODS: Forty-three MCTA studies of the vertebrobasilar arteries were performed with a multisection spiral CT scanner in 36 patients with SAH. Parameters used were 1-mm collimation, 0.625Q pitch, 120 kV, and 250 mAs. Contrast material was injected (80-100 mL, 3 mL/s) after a 15-20-second delay. Postprocessing of the vertebrobasilar system was performed by using maximum intensity projection and volume-rendering reconstruction. Vessel diameter was measured at different intracranial locations along the vertebral and basilar arteries perpendicular to their long axis by using curved reformatted multiplanar reformation. TCD imaging of the posterior circulation was performed within 24 hours. RESULTS: MCTA demonstrated narrowed arteries compatible with VBS in 13 patients, consistent with TCD findings. Despite TCD recordings of high flow velocity in three other patients, MCTA did not reveal vasospasm but did show wide arteries feeding arteriovenous malformations in two and normal-sized arteries in one. VBS in two patients was identified on MCTA but overlooked during TCD imaging. Twenty patients had normal findings on both TCD and MCTA studies. CONCLUSION: Cerebral MCTA is recommended as a reliable, rapid, and minimally invasive diagnostic method, one complementary to TCD imaging for assessing VBS in patients with SAH.

Method for rapid MRI needle tracking.

A new method for MRI needle tracking within a given two-dimensional (2D) image slice is presented. The method is based on k-space investigation of the difference image between the current dynamic frame and a reference frame. Using only a few central k-lines of the difference image and a nonlinear optimization procedure, one can resolve the parameters that define the 2D sinc function that best characterizes the needle in k-space. The spatial location and orientation of the needle are determined from these parameters. Rapid needle tracking is obtained by repeated acquisitions of the same set of several central k-lines (as in a "keyhole" protocol) and repeated computation of these parameters. The calculated needle tip is depicted on the reference image by means of a graphic overlay. The procedure was tested in computer simulations and in actual MRI scans (the computations were done offline). It was demonstrated that six k-lines out of 128 usually suffice to locate the needle. The refresh rate of the needle location depends on the time required to sample the subset of k-lines, calculate the current needle location, and refresh the reference image.

Basilar vasospasm diagnosis: investigation of a modified "Lindegaard Index" based on imaging studies and blood velocity measurements of the basilar artery.

BACKGROUND AND PURPOSE: Numerous studies have shown that cerebral vasospasm is one of the leading causes of death and neurological disability after subarachnoid hemorrhage. Most of these studies, however, have focused on anterior circulation vessels. Since the introduction of the transcranial Doppler (TCD), increasing attention has been given to basilar artery (BA) vasospasm, especially in traumatic subarachnoid hemorrhage. As shown for the anterior circulation, however, the significance of elevated flow velocities (FVs) in the posterior vessels may be ambiguous, so vasospasm may not be reliably differentiated from hyperemia. The purpose of the present study was to evaluate the potential additional value of an intracranial/extracranial FV ratio in the posterior circulation to cope with this shortcoming of the TCD in the diagnosis of BA vasospasm. METHODS: FV in the extracranial vertebral artery (VA) was measured in 20 healthy volunteers. Normative values of an intracranial/extracranial VA FV ratio (IVA/EVA) and a BA/extracranial VA FV ratio (BA/EVA) were calculated. Thirty-four patients with subarachnoid hemorrhage were then evaluated with TCD and CT angiography (CTA). The value of the IVA/EVA and BA/EVA ratios in the diagnosis and assessment of vertebrobasilar vasospasm was investigated. RESULTS: The extracranial VA could be insonated in all subjects at depths ranging from 45 to 55 mm. The average FV for the extracranial VA was 26 cm/s. The ratios between intracranial and extracranial VA FVs were 1.6 on both sides, whereas the ratio between the BA FVs and the mean extracranial VA FVs was slightly higher at 1.7. Fourteen patients (41.2%) had CTA evidence of BA vasospasm. Vasospasm was severe in 7 patients, moderate in 1, and mild in the remaining. An FV threshold of 80 cm/s was indicative of BA vasospasm in 92.8% with 3 false-positive results that could be related to vertebrobasilar hyperemia. Comparative analysis between CTA and TCD findings showed that BA/EVA was >2 in all patients with BA vasospasm (100% sensitivity) and < 2 in all but 1 patient without BA vasospasm (95% specificity). Furthermore, the BA/EVA ratio showed a close correlation with BA diameter (r=-0.8139, P<0.0001) and was >3 in all patients with severe vasospasm. CONCLUSIONS: The results of the present study showed that the BA/EVA ratio may contribute to an improved discrimination between BA vasospasm and vertebrobasilar hyperemia and enhance the accuracy and reliability of TCD in the diagnosis of BA vasospasm. Our data further suggest that the BA/EVA ratio may provide an approximation of vasospasm severity and help in identifying patients who are likely to suffer from hemodynamically significant vasospasm.