A new correlation-based fuzzy logic clustering algorithm for fMRI

Fuzzy logic clustering algorithms are a new class of processing strategies for functional MRI (fMRI). In this study, the ability of such methods to detect brain activation on application of a stimulus task is demonstrated. An optimization of the selected algorithm with regard to different parameters is proposed. These parameters include (a) those defining the pre-processing procedure of the data set; (b) the definition of the distance between two time courses, considered as p-dimensional vectors, where p is the number of sequential images in the fMRI data set; and (c) the number of clusters to be considered. Based on the assumption that such a clustering algorithm should cluster the pixel time courses according to their similarity and not their proximity (in terms of distance), cross-correlation-based distances are defined. A clear mathematical description of the algorithm is proposed, and its convergence is proven when similarity measures are used instead of conventional Euclidean distance. The differences between the membership function given by the algorithm and the probability are clearly exposed. The algorithm was tested on artificial data sets, as well as on data sets from six volunteers undergoing stimulation of the primary visual cortex. The fMRI maps provided by the fuzzy logic algorithm are compared to those achieved by the well established cross-correlation technique.

Improvement of cerebral oxygenation patterns and metabolic validation of superselective intraarterial infusion of papaverine for the treatment of cerebral vasospasm

OBJECT

The purpose of the present study was to assess cerebral oxygenation patterns and brain lactate concentration changes before, during, and after intraarterial infusion of papaverine with or without balloon angioplasty in patients with symptomatic vasospasm.

METHODS

A total of 23 vascular territories were successfully treated in 10 patients. In three patients balloon angioplasty was performed before the papaverine infusion. Continuous monitoring of jugular bulb vein oxygen saturation with a fiberoptic catheter and blood sampling allowed the assessment of the cerebral arteriovenous oxygen and lactate differences. A significant and rapid improvement in jugular bulb oxygen saturation was observed in all cases, with critical values reflecting an improvement in cerebral oxygenation after endovascular treatment of vasospasm (p = 0.005). Lactate concentration in the jugular bulb normalized within 4 hours in all patients who had evidence of brain lactic acidosis before superselective intraarterial infusion of papaverine. Recurrence of abnormal metabolic and oxygenation patterns were observed in one case in which an optimal hypertension and hypervolemic therapy could not be achieved after the procedure.

CONCLUSIONS

Improvement in cerebral oxygenation as well as prevention of cerebral lactic acidosis can be successfully achieved after intraarterial infusion of papaverine. Normalization of the oxygen supply after endovascular treatment has to be supported by optimal and well-monitored hypertension and hypervolemic hemodilution.

Selective amobarbital test for the determination of language function in patients with epilepsy with frontal and posterior temporal brain lesions

PURPOSE

Selective amobarbital tests with selective temporary inactivation of the left frontal operculum and/or the left parietotemporal cortex were performed in 5 patients with left-hemispheric epileptogenic lesions in or adjacent to classical Broca's and/or Wernicke's area. The aim was to assess language functions in these brain regions before surgery, to tailor the surgery according to the individual functional importance of these brain regions, and to predict postoperative outcome.

METHODS

Amobarbital was injected by transfemoral selective catheterization of the arteries supplying the target areas. Along with neuropsychological and neurological testing during the amobarbital procedure, EEG recordings were performed in all patients, and [99mTc]HMPAO-single photon emission computed tomography (SPECT) in 2 patients.

RESULTS

After the amobarbital injection into the left frontal opercular region, there was no recognizable language dysfunction in 3 patients. In these 3 patients, the lesions in or adjacent to the frontal operculum were completely resected without postoperative language impairment. In the remaining 2 patients, temporary language impairment after the amobarbital injection into the left frontoopercular and Wernicke's region, respectively, suggested language functions in these areas. Surgery was restricted to the left mesiotemporal lobe in 1 patient. In the other patient, the tumor infiltrating the frontal operculum was restrictively resected. Postoperatively, the first patient had no language impairment, but the latter had transient global aphasia, from which she recovered.

CONCLUSIONS

Selective temporary amobarbital inactivation of brain regions that may be associated with language has clearly indicated the presence or absence of language functions in these regions. The test contributed substantially to planning of the surgical approach in each patient. The predictive value of the amobarbital test was demonstrated by the postoperative outcome.

Tributary venosinus occlusion and septic cavernous sinus thrombosis: CT and MR findings

PURPOSE

In autopsy reports of patients who died of septic cavernous sinus thrombosis, tributary venosinus occlusion has been a common finding related to intracranial inflammatory complications. The purpose of this article is to illustrate the MR and CT appearance of septic cavernous sinus thrombosis and tributary venous occlusion.

METHODS

Over a period of 7 years, eight patients with septic cavernous sinus thrombosis were examined by contrast-enhanced thin-section CT. The CT scans of these eight patients and those of 30 healthy control subjects were assessed independently and subjectively by two blinded readers to ascertain the presence, size, and density of areas of nonopacification within the cavernous sinus and the presence of filling defects and dilation of tributary veins and venous sinuses. In six subjects, MR images supplemented by a contrast-enhanced spoiled gradient-recalled acquisition in the steady state (SPGR) sequence were assessed with respect to the presence of filling defects, expansion, and signal abnormalities within the cavernous sinus and tributary veins and sinuses. The MR and CT findings were compared.

RESULTS

The CT studies of the eight patients were consistently differentiated from those of the control subjects by the two readers. Contrast-enhanced CT findings in patients included areas of nonopacification that were present within the cavernous sinus bilaterally in six cases and unilaterally in two. The size of the filling defects exceeded 7 mm in 76% of thrombosed cavernous sinuses compared with 9% of control subjects. The mean density of filling defects in patients differed significantly from those in control subjects. Comparison of the MR and CT findings in six cases showed the contrast-enhanced SPGR sequence to be equivalent to CT with respect to delineation of filling defects.

CONCLUSION

Contrast-enhanced high-resolution CT findings indicate that venosinus thrombosis associated with septic cavernous sinus thrombosis is not restricted to the superior ophthalmic vein and is more common than previously assumed. A contrast-enhanced SPGR MR sequence may be used as a reliable alternative to establish the diagnosis of cavernous sinus and tributary venosinus thrombosis.

T2-weighted three-dimensional fast spin-echo MR in inflammatory peripheral facial nerve palsy

PURPOSE

Our objective was to identify histologically and intraoperatively verified focal nerve thickening of the distal intrameatal segment on three-dimensional fast spin-echo (FSE) T2-weighted MR images as a new diagnostic criterion in patients with inflammatory peripheral facial nerve palsy.

METHODS

Twenty-two patients with clinically diagnosed unilateral (n = 20) or bilateral (n = 2) inflammatory peripheral facial nerve palsy were examined on a 1.5-T MR imager using noncontrast and contrast-enhanced T1-weighted SE sequences and 3-D T2-weighted FSE sequences with secondary reformations. Abnormal contrast enhancement and possible focal nerve thickening of the distal intrameatal segment, labyrinthine nerve segment, and geniculate ganglion region were analyzed prospectively.

RESULTS

In all patients, the T1-weighted postcontrast SE images showed characteristic smooth, linear, abnormally intense contrast enhancement of the distal intrameatal segment, indicating peripheral inflammatory nerve palsy. In 23 nerves (96%) a focal bulbous nerve thickening of the distal intrameatal segment was observed on 3-D T2-weighted FSE images. In 100% of patients with peripheral inflammatory facial nerve palsy, postcontrast T1-weighted SE images showed a smooth, linear, and abnormally intense contrast enhancement of the distal intrameatal segment; reformatted very thin 3-D T2-weighted FSE images showed a focal bulbous nerve thickening of the distal intrameatal segment in 96% of patients. These findings corresponded to intraoperative and histologic findings.

CONCLUSION

Three-dimensional T2-weighted FSE sequences are fast and cheap compared with T1-weighted postcontrast images, but secondary reformations are time-consuming and require exact anatomic knowledge for careful analysis of the different nerve segments.

Cerebral metabolic changes (18F-FDG PET) during selective anterior temporal lobe amobarbital test

Cerebral glucose utilisation using 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) was measured in 4 patients with temporal lobe epilepsy during a selective anterior temporal lobe (TL) amobarbital test (ATLAT) and compared with their baseline values. 18F-FDG was injected intravenously immediately after administration of amobarbital into the anterior choroidal artery (acha) in the case of the superselective ATLAT and into the territories of acha, posterior communicating artery, and ophthalmic artery in the case of the ATLAT using the temporary balloon occlusion technique. A decrease in glucose uptake as a result of amobarbital application was observed in ipsilateral temporolateral (4 patients), ipsilateral temporomesial (2 patients) and bilateral frontolateral (1 patient) cortices. All patients showed decreased glucose uptake in contralateral temporolateral regions. Cerebellar diaschisis was observed in 2 patients. In conclusion, although aimed at selective inactivation of the mesiobasal TL structures, the ATLAT does not result in exclusive selective glucose hypometabolism of these structures. Relatively widespread ipsilateral and contralateral effects were observed suggesting local and remote metabolic deafferentation. No association was observed between the glucose uptake, clinical or memory performance.

Target definition and trajectory optimization for interactive MR-guided biopsies of brain tumors in an open configuration MRI system

We present an imaging strategy for planning and guiding brain biopsies in an open configuration MR system. Preprocedure imaging was performed in a 1.5-T MR system and was designed to provide, in a clinically efficient manner, high resolution anatomical and functional/physiologic information for precise definition and tissue characterization of the target, aiming at optimization of the biopsy trajectory for planning a safe and accurate procedure. The interventions were performed in a .5-T open bore magnet, and imaging was optimized to provide the imaging quality and temporal resolution necessary for performing the procedure interactively in near real time. Brain biopsies of 21 patients were performed in a 10-month period. Segmentation and surface rendering analysis of the lesions and vascular structures and dynamic MR perfusion and cortical activation studies provided an efficient and comprehensive way to appreciate the relationship of the target to surrounding vital structures, improved tissue characterization and definition of the tumor margins, and demonstrated the location of essential cortex, allowing appropriate placement of the burr hole and choice of optimal trajectory. Interactive protocols provided good visualization of the target and the interventional devices and offered the operator real-time feedback and control of the procedure. No complications were encountered. Advanced methods of image acquisition and processing for accurate planning of interventional brain procedures and interactive imaging with MR guidance render feasible the performance of safe and accurate neurointerventional procedures.

[False aneurysm in Behçet's syndrome]

HISTORY AND CLINICAL FINDINGS

A 32-year-old man developed acute right-sided sore throat, a thick voice and epistaxis. 13 years previously he had erythema nodosum, 12 and 10 year ago deep vein thrombosis. On admission he had Horner's syndrome, bulging of the gums and swelling of the paratracheal space. He had been on anticoagulation therapy with phenprocoumon since the leg vein thrombosis.

INVESTIGATIONS

Computed tomography demonstrated a false aneurysm of the right internal carotid artery. 9 months later a right radial artery aneurysm occurred, which was treated surgically. An arterial cannula had previously been placed at this site for pressure monitoring. 2 months later a false aneurysm of the right femoral artery was diagnosed: it had previously been used for an intravascular intervention. As embolization to the popliteal artery occurred after sonographically controlled compression had failed and reduction of anticoagulation treatment, this aneurysm, too, was treated surgically.

DIAGNOSIS, TREATMENT AND COURSE

Because of the tendency to aneurysm formation after arterial puncture and the history of venous thromboses the diagnosis of Behçet's syndrome was considered, confirmed by subsequently elucidated history of recurrent oral aphthous ulcers and folliculitis. There were no other manifestations of the syndrome. Immunosuppressive treatment was instituted after another two aneurysm recurrences were noted in the right common femoral artery.

CONCLUSIONS

This case illustrates that the diagnosis of Behçet's syndrome may be made more difficult if its manifestation is primarily vascular with minimal mucocutaneous involvement. It should be considered in the differential diagnosis of recurrent arterial aneurysms in a young person.

Mandibular osteomyelitis: evaluation and staging in 18 patients, using magnetic resonance imaging, computed tomography and conventional radiographs

Over a period of 3 years, 18 patients with mandibular osteomyelitis were prospectively investigated by conventional radiograph, computed tomography (CT) and in 6 cases by magnetic resonance imaging (MRI). The diagnosis was based on histology in 17 patients operated upon.

The anterior and posterior selective temporal lobe amobarbital tests: angiographic, clinical, electroencephalographic, PET, SPECT findings, and memory performance

The techniques, results, and problems of three types of selective temporal lobe (TL) amobarbital procedures (balloon technique with temporary occlusion of the internal carotid artery distal to the origin of the anterior choroidal artery (acha) [n = 19]; selective anterior catheterization of the acha [n = 20]; and selective catheterization of the peduncular P2-segment of the posterior cerebral artery [n = 5]) are described in a group of 40 patients with medically refractory complex partial seizures of mesial TL origin. Selective amobarbital tests were carried out before surgery to predict the memory deficit after an intended selective amygdalohippocampectomy. The effects of selective anaesthetization of TL were correlated with clinical data, pattern and duration of amobarbital induced EEG changes, and performance on verbal and nonverbal memory tasks measured during the test. In 4 patients the effect of selective amobarbital injection on regional and global metabolism was studied with 18F-FDG-PET, with the PET tracer being injected intravenously immediately after amobarbital. More recently in 2 patients the vascular territory perfused by amobarbital in the acha test was studied with SPECT using 99m Tc ECD injected immediately prior to the amobarbital into the acha. Whereas the PET studies showed a rather widespread and bilateral amobarbital-induced decrease of metabolism, the SPECT studies confirmed the selective distribution of the tracer in the vascular territory of the acha, i.e., in amygdala and hippocampus. The comparison of selective TL amobarbital test performance with postoperative neuropsychological performance showed that the predictive value of this test is rather good for the postoperative verbal memory but underestimates postoperative nonverbal ("figural") memory performance.

MR differentiation of adamantinous and squamous-papillary craniopharyngiomas

PURPOSE

To determine MR criteria for differentiating adamantinous from squamous-papillary craniopharyngiomas.

METHODS

The MR imaging features of 42 histologically proved craniopharyngiomas (25 adamantinous, 15 squamous-papillary, and two mixed subtypes) were examined with multiplanar T2-weighted and noncontrast and contrast-enhanced T1-weighted imaging. Differences in the mR features of both subtypes were evaluated retrospectively.

RESULTS

The adamantinous craniopharyngioma is a mixed solid-cystic or mainly cystic lobulated suprasellar or intrasellar/suprasellar tumor occurring in children and adults, typically with large nonenhancing hyperintense cysts on T1-weighted images. The squamous-papillary craniopharyngioma is a predominantly solid or mixed solid-cystic suprasellar tumor occurring in adults, appearing as a hypointense cyst on noncontrast T1-weighted images. Calcifications and recurrent tumors are more often observed in adamantinous tumors but can be seen in squamous-papillary tumors as well. Statistically significant parameters useful for differentiating the two tumor subtypes are the encasement of vessels, the lobulated shape, and the presence of hyperintense cysts in adamantinous tumors, and the round shape, the presence of hypointense cysts, and the predominantly solid appearance in squamous-papillary tumors.

CONCLUSION

Craniopharyngiomas can be divided into two clinically, histologically different subtypes, which suggests a different pathogenesis of these two types of tumor.

Contrast-enhanced MR of the facial nerve in patients with posttraumatic peripheral facial nerve palsy

PURPOSE

To estimate the value of noncontrast and contrast-enhanced T1-weighted MR imaging in detecting the underlying mechanisms of injury and regeneration in immediate- or delayed-onset posttraumatic peripheral facial nerve palsy.

METHODS

Twenty-four patients with posttraumatic peripheral facial nerve palsy were examined on a 1.5-T MR imaging unit with precontrast and postcontrast T1-weighted spin-echo and gradient-echo sequences.

RESULTS

Abnormal enhancement of the distal intrameatal nerve segment was visible in 92% of the patients up to 2 years after their initial trauma. A hematoma within the geniculate ganglion was seen in 33% of the patients with a longitudinal fracture. The greater superficial petrosal nerve (in 32% of patients) and the geniculate ganglion (in 48% of patients) were thick and intensely enhancing. Hematoma within the cochlea/vestibule or enhancement of the cochlea/vestibule and the vestibulocochlear (eighth) nerve was observed in transverse fractures.

CONCLUSION

MR images can show long-lasting abnormal nerve enhancement, especially in the distal intrameatal nerve segment, related to the long-lasting breakdown of the blood/peripheral nerve barrier associated with nerve degeneration and regeneration after traumatic stretching of the greater superficial petrosal nerve. Additionally, intraoperatively observed perineural and intraneural scar formation leads to thickening and intense enhancement of the affected nerve segments on MR images. A hematoma in the region of the geniculate ganglion can be seen in some but not all patients. Associated damage of the inner ear structures in patients with transverse fractures is also visible on MR images.

[Inflammatory diseases of the spinal cord and spinal nerve roots in the MRI]

PURPOSE

To evaluate characteristic and reliable MRI patterns of different inflammatory lesions of the spinal cord and the nerve roots in immunologically compromised and immunologically competent patients in order to be able to establish a correct diagnosis based on MRI findings.

MATERIAL AND METHODS

The MRI examinations of 52 patients (27 men, 25 women, mean age 38.5 years, range 14-75 years) with proven inflammatory lesions (39 patients) or tumorous/postactinic lesions of the spinal cord (6 patients) and vascular malformations of the spinal cord (7 patients) were retrospectively analyzed. All examinations were performed on a 1.5 T MR unit, using bi- or triplanar T1-w pre- and postcontrast as well as T2-w SE sequences. Additionally, a review of the common medical literature concerning inflammatory lesions of the spinal cord was included.

RESULTS

Clinical and radiological examinations allow a subdivision of inflammations of the spinal cord and the nerve roots into (meningoradiculo) myelitis and meningoradiculo (myelitis) in immunologically suppressed or competent patients. The MRI patterns of these two inflammatory subtypes vary: meningoradiculitis presents with an enhancement of the nerve roots and the leptomeninges; myelitis itself is characterized by single or multiple, diffuse or multifocal, with or without nodular, patchy or diffusely enhancing intramedullary lesions, with or without thickening of the cord and leptomeningeal inflammation. This differentiation helps to determine the underlying etiology in some of the patients. The immunologically suppressed patient suffers from viral infections (especially herpes simplex, varicella-zoster virus, cytomegalovirus), bacterinal infections (tuberculosis), but rarely from parasitic infections. The immunologically competent patient suffers from bacterial (borreliosis), but rarely viral infections, sarcoidosis and demyelinating diseases. Idiopathic myelitis is also common.

CONCLUSIONS

Secondary ischemic and demyelinating processes result in a complex morphology of inflammatory lesions on MRI, and therefore the whole spectrum of demyelinating, ischemic and inflammatory lesions has to be included in the differential diagnosis. Even tumors may imitate inflammatory myelitis and radiculitis. Most commonly, meningoradiculitis can be separated from myelitis. A reliable diagnosis of a specific inflammatory lesion is difficult and is mostly achieved in patients with multiple sclerosis and in patients with HIV-associated cytomegalovirus infection.

[Inflammatory facial paralysis in MRI. An overview]

In inflammatory peripheral facial nerve palsy pathologically intense, linear and smooth enhancement of the distal intrameatal nerve segment can always be observed on T1-w- SE- MR sequences. The other nerve segments often present with a pathological enhancement as well. On T2-w- SE sequences, a thickening of the distal intrameatal nerve segment can be observed. The pathological enhancement persists over weeks and months; even in patients with complete clinical recovery, a persistent enhancement of the distal intrameatal nerve segment can be demonstrated. No correlation can be established between the intensity of the enhancement, the clinical condition and the electrophysiological data on electroneurography. The persistent enhancement of the different nerve segments is due to a long-lasting breakdown of the blood-peripheral nerve-barrier related to the process of degeneration and regeneration of the facial nerve in inflammatory palsy.

The role of angiography in the evaluation of cerebral vascular malformations

Although magnetic resonance imaging has become the modality of choice for the diagnostic evaluation of cerebral vascular malformations, cerebral angiography remains indispensable for the evaluation of cerebral arteriovenous malformations. Super-selective angiography allows detailed endovascular exploration of the various vascular elements composing cerebral arteriovenous malformations and is essential in elucidating their angioarchitecture and for treatment planning. Clinicoangioarchitectural correlations further our understanding of the natural history of cerebral arteriovenous malformations.

Intensity of MR contrast enhancement does not correspond to clinical and electroneurographic findings in acute inflammatory facial nerve palsy

PURPOSE

To determine the value of MR contrast enhancement in predicting the course of acute inflammatory facial nerve palsy and in selecting patients for surgical decompression.

METHODS

Six patients with an acute inflammatory incomplete or complete peripheral facial nerve palsy (five idiopathic and one herpetic in origin) had repeated MR imaging studies with and without contrast enhancement, electroneurography, and clinical examinations to establish a connection between the intensity of contrast enhancement on MR images, the clinical condition, and the electrophysiological data. The examinations were performed every second day starting on the first day of admission until clinical recovery was proved by clinical deblockage (spontaneous clinical improvement). The last examination was performed 3 months after the onset of the facial nerve palsy.

RESULTS

An abnormal, very intense contrast enhancement of the facial nerve was always present in the distal intrameatal and proximal tympanic segments and in the geniculate ganglion. The labyrinthine segment exhibited a mild to moderate enhancement, and the distal tympanic and mastoid segments showed a moderate to intense enhancement. The intensity of contrast enhancement did not correspond to the severity, duration, or course of the facial nerve palsy, and the electroneurographic data had no predictive value in indicating the severity of the inflammatory process. Three months after clinical recovery, a persistent and more or less unchanged or even slightly more intense contrast enhancement was observed.

CONCLUSION

The long-lasting intense contrast enhancement seen in the facial nerve segments of patients who have acute peripheral inflammatory facial nerve palsy is explained by a two-phase breakdown of the blood-nerve barrier.

CT assessment of orbital volume in late post-traumatic enophthalmos

The potential of CT to facilitate preoperative planning of reconstructive maxillofacial surgery by orbital volume quantification was analysed in 11 patients with traumatic enophthalmos as a late sequela of zygomatic fractures. We carried out biplanar CT examination of the orbits, and calculated total orbital and fat volumes for the healthy and enophthalmic sides. Displacement of the orbital floor and lateral wall was present in 11 and 7 cases respectively. Indentation of the medial wall was noted in 9 cases. Quantitative evaluation of the orbital cavity revealed a significant increase (P < 0.0188) in total volume on the enophthalmic side, the difference between the two sides ranging from 9.2% to 36.4%, mean 17.9%. The degree of enophthalmos, measured radiologically as 2.5-5 mm, correlated with the increase in orbital cavity volume (P = 0.000076). Enophthalmos was 2.5-3 mm in 7 cases (63.6%) and 3.5-5 mm in 4 (36.4%). This corresponded with a mean increase in orbital volume of 3.4 ml (12.3%) and 7.1 ml (27.8%) respectively. Fat atrophy was not an aetiological factor in the production of post-traumatic enophthalmos.