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Biomedical subjects

J Fiebach

Publications and source records attributed to J Fiebach.

15 recordsLinked to original sources
PubMed2005

Geometric accuracy of magnetic resonance imaging of the mandibular nerve.

OBJECTIVES: Magnetic resonance imaging (MRI) is not routinely used for dental implant planning. A prerequisite for dental implant planning is the accurate imaging of risk structures like the mandibular nerve. The geometric accuracy of the imaging of the mandibular nerve was investigated. METHODS: Two human cadaver heads were scanned using MRI. Computed tomography (CT) scans of the same heads were used as a benchmark. Using a stereotactic frame, corresponding images of MRI and CT were superimposed and the concordance of the images of the mandibular nerve in MRI with those of the mandibular canal in CT was assessed. RESULTS: The geometric accuracy of the mandibular nerve in MRI was as good as that of the mandibular canal in CT imaging. CONCLUSIONS: MRI of the mandibular nerve is sufficiently accurate for the use of this imaging method in dental implant planning.

Artifacts↗
PubMed2004

[MR volumetry of the trigeminal nerve in patients with unilateral facial pain].

PURPOSE: To assess whether MRI can detect atrophy of the trigeminal nerve in patients with trigeminal neuralgia. MATERIALS AND METHODS: A prospective MRI study was conducted in 39 patients (trigeminal neuralgia, trigeminal neuropathy, or atypical facial pain) and 25 volunteers. Using a coronal orientation (T1 Flash 3D; T2 CISS 3D), regions of interest were delineated in the cisternal part of the trigeminal nerve along the border of the nerve to calculate the volume of the nerve. The volume of the nerve was compared side-by-side in each patient (t-test, p < 0.05) and the volume difference compared between patients and volunteers. RESULTS: The volume of the compromised trigeminal nerve in patients with trigeminal neuralgia was lower than on the contralateral healthy side, with the difference between healthy and compromised side statistically significant (p < 0.05). In all other patients and in all volunteers, no significant difference was found between the volume of the healthy and compromised nerve. The volume difference between the healthy and compromised side in patients with trigeminal neuralgia was significantly higher (p < 0.05) than in all other patients and volunteers. CONCLUSION: Atrophy of the trigeminal nerve caused by a nerve-vessel conflict can be detected by MRI. Only patients with trigeminal neuralgia show this unilateral atrophy. Therefore, it is possible to demonstrate the result of the nerve-vessel conflict and to determine the consequences of such a conflict.

Adult↗
PubMed2003

[Dissection of four cerebral arteries after protracted birth].

A 37-year-old woman suffered from middle cerebral artery infarction secondary to dissection of the left internal carotid artery. Nine days before, a cesarean section had been performed on her after 20 h of unsuccessful labor. Cerebral angiography at admission revealed no further vascular abnormalities. A few days later, however, the patient developed additional dissections of the right internal carotid artery and both vertebral arteries. Pregnancy, childbirth, and a history of rheumatoid arthritis in this patient may have contributed to the dissections; however, due to the unknown etiology of cervical dissections, the pathogenetic contribution of all of these factors is incompletely understood.

Adult↗
PubMed2003

[Bilateral vertebral artery dissection after chiropractic treatment].

A 31-year-old woman suffered a brainstem infarction secondary to chiropractic neck manipulation. A dissection of both vertebral arteries could be demonstrated by MR tomography. This case report should alert therapists to be aware of vertebrobasilar complications after spinal manipulations.

Adult↗
PubMed2003

[Normal and abnormal water diffusion in the brain].

Diffusion magnetic resonance imaging (MRI) has become an important tool in the radiologic diagnosis of diseases of the brain as it measures molecular motion of water that characterizes the microstructure of tissues. Its most important clinical use to date is the early detection of cerebral ischemia by revealing the ischemic injury shortly after vessel occlusion and simultaneously providing therapy-relevant information on the tissue at risk. Furthermore, diffusion MRI is diagnostically promising in other diseases of the brain and is thus increasingly becoming part of routine clinical protocols in the diagnosis of tumors, inflammation, trauma, demyelination, dysmyelination and neurodegeneration. Although abnormalities of diffusion are generally not pathognomonic, diffusion MRI affords information about tissue changes for specific disorders that complements information obtained with standard MR techniques and frequently shows pathology earlier. In addition, diffusion MRI can be applied to plan, guide and follow-up biopsies or resective surgery. Particularly diffusion tensor imaging (DTI), which displays the orientation of white matter fibers, holds promise for improved surgical planning. Moreover, DTI can be used to detect changes in connectivity between functional brain areas. Therefore, DTI is highly relevant not only in advancing the knowledge of white matter diseases but also in stimulating research on normal brain development and brain aging.

Blood-Brain Barrier↗
PubMed2001

Diffusion-weighted imaging of the spine using radial k-space trajectories.

INTRODUCTION: Diffusion-weighted MR imaging (DWI) of the spine requires robust imaging methods, that are insensitive to susceptibility effects caused by the transition from bone to soft tissue and motion artifacts due to breathing, swallowing, and cardiac motion. The purpose of this study was to develop a robust imaging method suitable for DWI of the spine. METHODS AND SUBJECTS: A radial k-space spin echo sequence has been implemented, which is self-navigating because each acquisition line passes through the origin of k-space. Influence of cardiac motion and associated flow of cerebrospinal fluid is minimized by cardiac gating with a finger photoplethysmograph. The sequence has been tested on a 1.5T system. Diffusion-weighted images of six normal volunteers were acquired in the sagittal plane with 4 b values between 50 and 500 s mm(-2). Because of the symmetries of the cord, diffusion measurements in the head-foot (HF) or left-right (LR) directions were sufficient to measure the dominant effects of anisotropy. RESULTS: The apparent diffusion coefficients (ADCs) measured, respectively, in the LR and HF directions were (0.699+/-0.050)x10(-3) and (1.805+/-0.086)x10(-3) mm(2) s(-1) in the spinal cord, (1.588+/-0.082)x10(-3) and (1.528+/-0.052)x10(-3) mm(2) s(-1) in the intervertebral disks, and (0.346+/-0.047)x10(-3) and (0.306+/-0.035)x10(-3) mm(2) s(-1) in the vertebrae of the cervicothoracic spine. CONCLUSION: Diffusion-weighted spin echo sequences with radial trajectories in k-space provide a means of achieving robust, high quality diffusion-weighted imaging and measuring ADCs in the spine. The application of the diffusion-weighting gradients in different directions allows diffusion anisotropy to be measured.

Humans↗
PubMed2001

[Value of MRI in intracerebral and subarachnoid hemorrhage].

Intracranial hemorrhage (ICH) accounts for 15% of all strokes. In hyperacute emergency assessment, CT is the diagnostic standard for differentiating between hyperacute ICH and ischemic stroke. At this stage, MRI is considered to be of little value for the diagnosis of ICH or subarachnoidal hemorrhage (SAH). We review the current literature and characterize the role of MRI in the diagnosis of ICH and SAH as well as hyperacute stroke in general: While MRI is considered superior to CT in the diagnosis of subacute and chronic ICH/SAH, in hyperacute ICH this is still a matter of debate. MRI signal characteristics of ICH depend on hemoglobin degradation. Deoxyhemoglobin is the MRI substrate for demonstration of blood due to its paramagnetic properties causing signal loss on susceptibility weighted images (T2*-WI). Preliminary data, however, suggest that the sensitivity of modern stroke MRI protocols is sufficiently high for hyperacute ICH and SAH and may render additional information with regard to the etiology of ICH or SAH. Further interest is focused on perihemorrhagic pathophysiologic processes, which may help to improve therapeutic decision making in patients with ICH.

Cerebral Hemorrhage↗
PubMed2001

[Thrombolysis in cerebral ischemia. An overview].

Thrombolytic therapy for acute ischemic stroke within the 3-h time window has been approved. In the US, where FDA approval has existed for about 4 years, less than 2% of stroke patients presently receive thrombolytic therapy. This review illustrates all completed trials of intravenous and intra-arterial thrombolytic therapy for carotid artery and vertebrobasilar artery stroke and includes recommendations for therapy, diagnostic procedures and their effect on patient selection, meta-analyses, phase IV trials, and cost efficacy analyses.

Cerebral Infarction↗
PubMed2001

Comparison of CT with diffusion-weighted MRI in patients with hyperacute stroke.

Tissue changes in ischaemic stroke are detectable by diffusion-weighted MRI (DWI) within minutes of the onset of symptoms. However, in daily routine CT is still the preferred imaging modality for patients with acute stroke. Our purpose of this study was to determine how early and reliably ischaemic brain infarcts can be identified by CT and DWI. Three neuroradiologists, blinded to clinical signs but aware that they were dealing with stroke, analysed the CT and DWI of 31 patients with an acute ischaemic stroke. We calculated kappa-values to analyse inter-rater variability. The ratings were compared with follow-up studies showing the extent of the infarct. The combined assessment of all observers gave positive findings in 77.4% of all CT examinations, with kappa = 0.58. Areas of high signal were seen on all DWI studies by all observers (kappa = 1). Estimation of the extent of the infarct based on DWI yeilded kappa = 0.70 and that based on CT kappa = 0.39. DWI was much more reliable than CT in the detection of early ischaemic lesions and we believe that it should be used in acute ischaemic stroke before aggressive therapeutic intervention.

Aged↗
PubMed2001

[Magnetic resonance tomography for planning dental implantation].

PROBLEM: Three-dimensional imaging diagnostics are increasingly recommended before inserting dental implants in high-risk areas and in cases of severe alveolar atrophy. Since patients are exposed to considerable radiation with computed tomography (CT), the possibilities of employing magnetic resonance imaging (MRI) of the jaw as a diagnostic imaging method before inserting dental implants were examined. MATERIAL AND METHOD: Twelve patients and three volunteers were examined by MRI with T1-weighted, fat-suppressed sequences and conventional T1-weighted sequences. The patients wore a diagnostic splint including markers--in the form of capillaries filled with 0.025 x 10(-2) M gadolinium solution (1.5 mm in diameter)--in the planned implant's position and axis. RESULTS: The presentation of relevant anatomic structures and the three-dimensional accuracy of the markers were judged. Metal artefacts were evaluated in vitro. The MRI of the jaw and midface represents the mandibular canal, the maxillary sinus, and other decisive anatomic structures by detailed representation of the connective tissue surrounding the bone. Artefacts of metallic fillings reduce the image quality. CONCLUSION: Obtaining clinical findings and planning before inserting dental implants with the help of MRI can certainly be applied with toothless patients and facilitates three-dimensional planning by representing the exact location and angle of the drill tubes. Local restrictions result from metal extinction artefacts in jaws with teeth and in controls after having inserted titanium implants.

Adolescent↗
PubMed1999

[Spectrum of neurological symptoms in dissections of brain-supplying arteries].

BACKGROUND AND OBJECTIVE: Dissection of extracranial arteries that supply the brain is a common cause of ischemic stroke in youngish persons. Yet this disease, with its warning and early symptoms, is inadequately known among the population as well as doctors. This study was undertaken to demonstrate the incidence, severity and sequelae of this condition, important in both routine general and hospital practice, with particular emphasis on early signs and diagnosis. PATIENTS AND METHODS: The data from 33 patients (20 men, 13 women, average age 42 [21-72] years) who during one year had been treated in the authors' hospital for carotid (n = 23) or vertebral (n = 10) artery dissection were analysed. RESULTS: The admission diagnosis of dissection, based on the history and ultrasound findings was in almost all cases confirmed by magnetic resonance imaging (wall haematoma), magnetic resonance angiograhy, computed tomography-angiography or conventional angiography. Typical warning and early symptoms such as whiplash sensation unilateral pain in the throat, neck and head or Horner's syndrome were elicited in nearly 50% of patients, while known causes such as trauma or connective tissue disease were confirmed in only 27%. Neurological deficits of ischemic infarction, some of them severe, persisted in two-thirds of patients, brain death occurred in one. CONCLUSIONS: Dissection of carotid or vertebral arteries is a statistically and medically relevant cause of stroke in youngish persons that can be diagnosed by attention to typical warning and early symptoms and the performance of noninvasive tests. The often life-threatening sequelae of possible cerebral ischemia can be diagnosed and even averted by early recognition of the cause.

Acute Disease↗
PubMed1999

Iodixanol in cerebral computed tomography: a randomized, double-blind, phase-III, parallel study with iodixanol and iohexol.

Iodixanol is a new nonionic dimer, isotonic with blood at all clinically relevant concentrations. Iodixanol (270 mg I/ml) was compared in a double-blind, randomized, parallel-group, phase-III study to the monomeric nonionic iohexol (300 mg I/ml) for evaluation of safety, tolerability and radiographic efficacy during cerebral CT. One hundred adult patients scheduled to undergo contrast-enhanced cerebral CT were randomly allocated to receive either iodixanol or iohexol. All completed the trial. Safety was evaluated by recording discomfort and other adverse events, tolerance by assessing intensity and incidence of discomfort. Radiographic efficacy was assessed from the diagnostic information and the radiographic density. No serious adverse events occurred. One patient (2 %) in the iodixanol group and one patient (2 %) in the iohexol group experienced a transient reddening at the neck and lower neck-line, respectively. Both contrast agents were well tolerated. One patient (2 %) in the iodixanol group and two patients (4 %) in the iohexol group experienced a sensation of warmth (discomfort) in connection with the injection. No difference between the two contrast media were noted radiographically. This comparison between iodixanol and iohexol showed both contrast media to be safe, well-tolerated and efficacious for use in cerebral CT.

Adult↗
PubMed1999

[MRI with fat suppression in the visualization of wall hematoma in spontaneous dissection of the internal carotid artery].

PURPOSE: Comparison of different MR-examination techniques for the diagnosis of acute spontaneous internal carotid artery dissection. PATIENTS AND METHODS: 13 patients (age range 23-59 years) with symptomatic spontaneous dissection of the internal carotid artery were examined. The MRI protocol contained a transverse spin echo sequence, a time-of-flight MR-angiography and a coronal fat suppressed T1-weighted sequence. The earliest examination was performed three days after symptom onset. Follow-up extended up to 30 months. We compared the three different sequences to find out the one that demonstrated the hematoma best. RESULTS: MR-angiography shows a narrowing of the vessel diameter in early examinations. During the subacute stage methemoglobin can obscure this finding. From the third day on fat suppressed T1-weighted images showed a hyperintense hematoma that strongly contrasted to the surrounding fatty tissue. Fat suppressed images showed a hyperintense hematoma up to 10 months after symptom onset while MRA and spin echo sequences did not. CONCLUSIONS: Fat suppressed T1-weighted images are superior in showing vessel wall hematoma and should thus be used in the standard MR-protocol for spontaneous internal carotid artery dissection.

Adipose Tissue↗