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U Dorenbeck

Publications and source records attributed to U Dorenbeck.

At least 19 recordsLinked to original sources
PubMed2005

Reliability of atlas-derived coordinates in deep brain stimulation.

BACKGROUND: In deep brain stimulation the way to define and localize the optimal target for the individual patient is still under debate. The objective of our study was to investigate the reliability of atlas derived data by comparing them with direct targeting on MR images. METHOD: We investigated 28 STN targets in 14 volunteers. The stereotactic coordinates of the dorso-lateral subthalamic nucleus (STN), were determined in 5 different ways for both STNs of each individual volunteer: 1. directly, on axial T2WI spin echo slices, 2. directly, on coronal T2WI spin echo slices and after fusion of data sets: 3. indirectly, on an axial atlas plate, 4. indirectly, on a coronal atlas plate, 5. indirectly, 12 mm lateral, 3 mm posterior and 3 mm inferior to mid-AC-PC. FINDINGS: The differences between MRI derived targets on axial vs. coronal slices were not statistically significant. After detection of the atlas derived targets the resulting x-coordinates were found more lateral than after direct detection on both, axial and coronal T2-weighted images (p < 0.001). On axial images y-coordinates were located more anterior (p = 0.240) on atlas derived targets and more posterior when target localizations were compared on coronal slices (p < 0.001). z-Coordinates were more superior after atlas targeting compared to MRI targeting (p < 0.001). Differences up to 6.21 mm occurred. CONCLUSIONS: Despite the limitations concerning image distortions and slice thickness, direct target planning on MRI, regarding our results, is more reliable than targeting solely based on atlas derived data. Only MRI gives us detailed information about the individual configurations of central structures in every single patient. However, targets, which are not detectable on MRI like the nucleus ventralis intermedius have to be planned using stereotactic atlas information. In these cases intra-operative micro-electrode recording might help to better define the target region.

Adult↗
PubMed2005

[Spinal syndrome triggered by a lumbar spinal av malformation. A case report].

We report the case of a 64-year-old male suffering from long-term claudicatio spinalis who underwent surgery in an orthopedic outpatient ward for posterior lumbar interbody fusion and bony decompression due to spinal stenosis. Postoperatively, the clinical symptoms, consisting of difficulties with walking and stocking-like dysesthesia of both lower extremities, did not improve. Due to persistent complaints, spinal MRI was performed which revealed myelomalacia and moreover was indicative of dural arteriovenous (AV) malformation at the L2-3 spinal level, which was verified as a type Ia AV fistula (according to Spetzler) by digital subtraction angiography (DSA). After microsurgical treatment of the AV fistula, clinical symptoms improved and control DSA could demonstrate complete disconnection of the fistula without any signs of recanalization. This case demonstrates that neurological deficits of patients suffering from degenerative spinal disorders can generally be considered as caused by more common spinal disease such as lumbar stenosis. Since vascular malformations may also cause neurological deficits and even mimic symptoms of spinal stenosis, it is important to consider these entities in diagnostic evaluation.

Arteriovenous Malformations↗
PubMed2005

[Diffusion-weighted imaging in the diagnostic evaluation of the hydrocephalus in patients with acute or chronic increase in cerebral pressure].

PURPOSE: To investigate whether diffusion-weighted imaging (DWI) in magnetic resonance imaging (MRI) provides additional information about the periventricular white matter for the assessment of hydrocephalus. MATERIALS AND METHODS: Sixteen MRI examinations (11 with acutely increased cerebral pressure, 5 without symptoms) on 15 patients with hydrocephalus (4 patients with communicating hydrocephalus and 11 patients with obstructive hydrocephalus) were analyzed. One symptomatic patient subsequently became asymptomatic. We investigated the "apparent diffusion coefficient" (ADC) in the subcortical and periventricular white matter. The ADCs of the study patients were compared with those of a healthy control group. RESULTS: Symptomatic patients with hydrocephalus, 6/11 showed periventricular edema and a significantly higher ADC values in the periventricular region than in the subcortical white matter. 5/11 symptomatic patients showed significantly higher ADC values even in the absence of periventricular interstitial edema (both groups contained patients with communicating and obstructive hydrocephalus). All 5 asymptomatic patients with hydrocephalus did not have a significantly higher ADC values in the periventricular region. CONCLUSION: In patients with hydrocephalus and acutely increased cerebral pressure, DWI showed a significantly higher ADC values in the periventricular region even without visible interstitial edema on conventional MRI sequences.

Adolescent↗
PubMed2005

Detection rate and efficiency of lymph node assessment with axial and coronal image reading based on 16 row multislice CT of the neck.

PURPOSE: Multislice CT (MSCT) has the advantage of isotropic volumetric data acquisition which allows high resolution data reconstruction in the axial and coronal plane. We evaluate the accuracy and efficiency of coronal reconstruction compared to axial reconstructions of a routinely performed CT scan exemplary in neck lymph node assessment performed on a 16 row MSCT. MATERIAL AND METHODS: Contrast enhanced neck MSCT of 24 patients with known lymphoma were evaluated prospectively for lymph node assessment. 4 blinded readers evaluated the axial and coronal reconstructions of the same patient. Neck lymph nodes larger than 10 mm were evaluated by their anatomical region (deep jugular chain, submandibular, nuchal). Time for axial and coronal image evaluation was assessed. Detection rate was compared with consensus reading as gold standard. RESULTS: In consensus reading 169 enlarged lymph nodes in the deep jugular chain were found. Detection rate for axial image interpretation was 36.1 % with 54.9 % in coronal reading. Assessing the submandibular lymph nodes (n = 45) axial interpretation revealed 53.9 % with 36.1 % in coronal reading. Evaluation time for axial reading was in all but one reader significantly longer (mean 176 seconds) than in coronal reading (mean 129 seconds). CONCLUSION: Coronal image reading improves the detection rate of cranio-caudal oriented structures. Considering representatively neck lymph nodes in the deep jugular chain the image interpretation time is significantly reduced. Still axial reading remains necessary for assessing axially oriented structures such as the submandibular region in the neck.

Adult↗
PubMed2005

Diffusion-weighted imaging with calculated apparent diffusion coefficient of enhancing extra-axial masses.

BACKGROUND AND PURPOSE: Sometimes intracranial contrast-enhancing tumors like meningiomas, metastases, lymphomas, and schwannomas can mimic each other. It was the aim of the present study to investigate if intracranial contrast-enhancing lesions can be reliably differentiated with the help of diffusion-weighted imaging with calculated apparent diffusion coefficients (ADCs). METHODS: 29 patients (ages ranging from 22 to 82 years, mean age of 58.6 years) were included. Nine meningiomas, 7 metastases, 6 lymphomas, and 7 schwannomas were investigated. The ADC value in the lesions and in the perifocal edema was analyzed. RESULTS: For the lymphomas, the authors measured the lowest ADC values in the contrast-enhancing part (0.59 +/- 0.09 . 10(-3) mm2/sec). The meningiomas showed a mean ADC value of 0.98 +/- 0.18 . 10(-3) mm2/sec. The schwannomas and metastases showed higher ADC values of 1.33 +/- 0.28 . 10(-3) mm2/sec and 1.05 +/- 0.20 . 10(-3) mm2/sec. The authors saw a statistically significant difference between lymphomas, meningiomas, and metastases concerning the ADC values in the contrast-enhancing part. CONCLUSIONS: In spite of a small sample size and partly a wide range of values, the authors found statistically significant differences between meningiomas, metastases, and lymphomas concerning ADC values. Nevertheless, a differentiation of these lesions only with the help of ADC values seems questionable.

Adult↗
PubMed2004

Degenerative diseases of the cervical spine: comparison of a multiecho data image combination sequence with a magnetisation transfer saturation pulse and cervical myelography and CT.

Assessing degenerative disease in the cervical spine remains a challenge. There is much controversy about imaging the cervical spine using MRI. Our aim in this prospective study was to compare a T2*-weighted 2D spoiled gradient-echo multiecho sequence (MEDIC) with a magnetisation transfer saturation pulse with cervical myelography and postmyelographic CT. Using an assessment scale we looked at the vertebral bodies, intervertebral discs, neural foramina, anterior and posterior nerve roots, grey matter, ligamentaflava, oedema in the spinal cord and stenosis of the spinal canal. We also evaluated postmyelography CT and the MEDIC sequence for assessing narrowing of the neural foramina in a cadaver cervical spine. We examined 67 disc levels in 18 patients, showing 18 disc prolapses and 21 osteophytes narrowing the spinal canal or the neural foramina. All MRI studies showed these abnormalities findings equally well. Postmyelography CT was significantly better for showing the bony structures and the anterior and posterior nerve roots. The MEDIC sequence provided excellent demonstration of soft-tissue structures such as the intervertebral disc and ligamentum flavum. No statistical differences between the imaging modalities were found in the assessment of narrowing of the neural foramina or the extent of spinal stenosis. The cadaver measurements showed no overestimation of abnormalities using the MEDIC sequence.

Adult↗
PubMed2004

[Glomus tumors of the head-neck-region].

Glomus tumors of the head and neck are rare tumors of adulthood which arise from paraganglia or glomus cells within the carotid glomus, vagus nerve, middle ear or jugular foramen. The diagnosis of these mostly benign lesions is predominantly done with CT and MRI. DSA can provide important additional information. Besides surgical resection, one therapy option is radiological intervention with tumor embolisation. Because of the typical radiological imaging and the "salt and pepper appearance" in MRI, glomus tumors can be differentiated from other lesions in the head and neck. This review gives a survey of the classification, diagnosis and therapy of paragangliomas with images to demonstrate characteristic features.

Glomus Tumor↗
PubMed2004

[Proximal protection systems using carotid artery stent].

Controversies as to whether or not a protection device should be used in carotid artery stenting exist. Currently three temporary cerebral protection devices are being used. These are devices with distal balloon occlusion or filtration baskets and proximal occlusion devices with flow reversal in the internal carotid artery. This article focuses on flow reversal systems and aims to give some advice as to which patients could benefit from their use.

Angioplasty, Balloon↗
PubMed2004

[Technique and approach to carotid stenting].

Assuming that the ongoing large randomized controlled trials comparing CAS and endarterectomy support the efficacy and safety of CAS, this method will play a major role in patients with carotid stenosis in the near future. Patient selection, establishing standards of treatment, and systematic training of the interventionist are major issues. This article aims to give an overview of current techniques and devices available in CAS.

Angioplasty, Balloon↗
PubMed2004

High-resolution contrast-enhanced magnetic resonance angiography of the carotid arteries using fluoroscopic monitoring of contrast arrival: diagnostic accuracy and interobserver variability.

PURPOSE: To evaluate the diagnostic accuracy of high-resolution contrast-enhanced magnetic resonance angiography (CE-MRA) of the supra-aortic arteries using the CareBolus technique. Digital subtraction angiography was the standard of reference. MATERIAL AND METHODS: Fifty consecutive patients with suspected internal carotid artery stenosis underwent CE-MRA and digital subtraction angiography. CE-MRA was performed on a 1.5-T superconducting scanner with the CareBolus technique. CareBolus combines a nearly real-time 2D-FLASH (fast low angle shot) sequence for fluoroscopic triggering and a high-resolution 3D-FLASH with elliptical centric view order for the angiographic pulse sequence (6.0/2.16 ms [TR/TE], 30 degrees flip angle, 30.98 s acquisition time, 0.88 mm effective (interpolated) partition thickness and a 160 x 512 matrix). Intra-arterial digital subtraction angiography and CE-MRA studies were evaluated independently by four blinded readers. Internal carotid artery stenoses were graded according to the NASCET criteria. RESULTS: CE-MRA had an accuracy of 92.53%, a sensitivity of 95.64%, and a specificity of 90.39% for the identification of carotid artery stenoses > or = 70% (grade 3). Image quality for suppression of stationary tissue and venous contrast was good, but was reduced in five cases due to patient motion. CONCLUSION: The CareBolus technique is a useful non-invasive method for high-resolution imaging of the supra-aortic vessels because of its easy application and high sensitivity and specificity. Limitations can occur in non-compliant patients due to motion artifacts during the measurement time.

Adult↗
PubMed2004

Degenerative diseases of the lumbar spine. Comparison of the multiecho data image combination sequence with magnetization transfer saturation pulse versus lumbar myelography/postmyelographic computed tomography.

PURPOSE: To compare a T2* weighted 2D spoiled gradient echo multiecho sequence (MEDIC) with magnetization transfer saturation pulse versus lumbar myelography and postmyelographic computed tomography (pCT). MATERIAL AND METHODS: 84 disk levels in 27 patients were examined. The vertebral bodies, intervertebral disks, neural foramina, cauda equina, ligamentum flavum, and narrowing of the spinal canal were investigated using an evaluation scale. In addition, the pCT and the MEDIC sequence were evaluated for assessing the narrowing of the neural foramina in a phantom study using a cadaver preparation of the lumbar spine. RESULTS: A total of 28 disk herniations, 11 cases of osteophytes narrowing the spinal canal or the neural foramina, and 7 spinal canal stenoses were detected. The pCT was significantly better in visualizing the cauda equina. The MEDIC sequence was significantly superior in visualizing the extension of the ligamentum flavum. No statistical differences between either image modality were found concerning assessment of the narrowing of the neural foramina and the spinal canal, nor regarding evaluation of the vertebral disk and the vertebral body. Measurements of the phantom study showed that the MEDIC sequence did not overestimate narrowing of the neural foramina. CONCLUSIONS: The T2* MEDIC sequence has proved to be as accurate as pCT in evaluating osteophytes and narrowing of the neural foramina. In doubtful standard magnetic resonance imaging findings, this means that an additional axial T2* MEDIC sequence may be of value in reaching the same accuracy as pCT.

Adult↗
PubMed2003

Image fusion of MR images and real-time ultrasonography: evaluation of fusion accuracy combining two commercial instruments, a neuronavigation system and a ultrasound system.

OBJECTIVE: The aim of our study was to evaluate MRI/Ultrasonography fusion accuracy depending on three ultrasonographic parameters. METHOD: An ultrasonography and MRI compatible model was created, consisting of a plastic box, which contained 3 objects. MRI scans were performed with 128 sagittal slices. The objects were segmented and 3D reconstructions were created. A special ultrasound adapter with 3 reflective markers was fixed to the ultrasound probe. Thus, the probe could be tracked by the navigation system (Vector Vision(2), BrainLab, Heimstetten, Germany) and the segmented shape of the 3D-objects obtained from the MR images were overlaid onto the ultrasound display (Elegra, Siemens, Erlangen, Germany). The dependency of fusion accuracy on different depth of ultrasound display, different distances between probe and objects and different angles between the axis of the ultrasound probe and the centre of the spheres was evaluated. 435 single measurements were performed. FINDINGS: Overall fusion accuracy was 1.08 mm+/-0.61 mm (mean +/- standard deviation) for spheres and 1.6 mm+/-1.1 mm for arrow heads. If the ultrasound probe was directed more tangentially to the surface of the spheres the fusion became increasingly inaccurate (P<0.05). Fusion accuracy decreased the more distant the US probe was held to the object (P<0.05). Different depth of ultrasound display had no significant effect on fusion accuracy. CONCLUSIONS: Highly accurate fusion of MR images and real-time ultrasonography could be achieved. However, careful interpretation of the fused data is necessary, when different angles and distances of the US probe to the object are concerned.

Brain↗
PubMed2003

MRI of the abnormal cervical spinal cord using 2D spoiled gradient echo multiecho sequence (MEDIC) with magnetization transfer saturation pulse. A T2* weighted feasibility study.

OBJECTIVES: The aim of this study was to assess the potential of heavily T2* weighted 2D spoiled gradient echo multiecho sequence MEDIC (multi echo data image combination) with magnetization transfer saturation pulse (MTS) for detecting abnormality of the cervical spinal cord. METHODS: 11 patients, 5 women and 6 men aged from 14 to 79 years (mean age 51.18 years), with traumatic, hemolytic-hemorrhagic or neoplastic diseases of the cervical spinal cord were examined with MRI. In cases with suspected myelopathy, the feasibility of the 2D spoiled gradient echo multiecho sequence MEDIC with MTS was evaluated in comparison with the results of spin echo T1W, spin echo T2W, multi echo (TSE in our case) and spin-echo multi-echo technique with magnetization preparation (turbo inversion recovery--TIR--in our case) sequences. RESULTS: Distortion of the "H" sign was found in all but one case. Hemorrhage was best shown by MEDIC, massive edema was very well visible using MEDIC, TIR and TSE T2W, whereas mild edema was visible with MEDIC only. CONCLUSIONS: Our preliminary experience in 11 patients shows that MEDIC can be used for the diagnosis of cervical spinal cord pathology.

Adolescent↗
PubMed2003

Diffusion-weighted echo-planar MRI of the brain with calculated ADCs: a useful tool in the differential diagnosis of tumor necrosis from abscess?

BACKGROUND AND PURPOSE: It was the aim of this study to evaluate whether brain abscesses could be distinguished reliably from necrotic brain tumors using diffusion-weighted imaging (DWI) with calculated apparent diffusion coefficients (ADCs). METHODS: The authors studied 27 lesions in 26 patients (21 tumors and metastases, 5 pyogenic brain abscesses, and 1 cerebral toxoplasmosis). DWI was obtained with a single-shot echo-planar imaging spin-echo sequence. ADCs were calculated for all images. RESULTS: ADCs (x 10(-3) mm2/s) measured in the necrotic parts of the tumors ranged from 2.94 (glioblastoma) to 1.51 (astrocytoma III). In the inflammatory lesions, ADCs ranged between 0.91 and 3.07 (cerebral toxoplasmosis and pyogenic abscess). The contrast-enhanced parts of the lesions showed ADC values from 0.77 (pyogenic abscess) up to 1.68 (glioblastoma). CONCLUSIONS: DWI with calculated ADC values does not allow the reliable differentiation of enhanced central necrotic intracranial lesions.

Astrocytoma↗
PubMed2002

Tentorial and dural calcification with tertiary hyperparathyroidism: a rare entity in chronic renal failure.

A case of rare calcification of the tentorium cerebelli, the thoracal dura mater of the spine, and the sclera in an adult male patient with tertiary hyperparathyroidism is presented. The often reported feature in the skull is that of a combination of osteopenia and osteosclerosis giving a granular bone texture. Extensive dura calcification with this condition has very rarely been reported. It is the aim of this paper to document the latter in a patient with chronic renal failure and tertiary hyperparathyroidism.

Adenoma↗
PubMed2002

[Evaluation of a new, portable ultrasound system in routine clinical use].

AIM: Evaluation of a new, hand-carried ultrasound system (SonoSite 180) for routine use at a university hospital. METHODS: 101 routine ultrasound examinations were performed as bedside examinations on the wards or in the ultrasound centre by three experienced sonographers. The quality and results of examinations using the SonoSite 180 were evaluated in a standardized questionnaire. RESULTS: in 89 % of the ultrasound examinations, results were at least satisfactory. Even though the examiners felt some uncertainty due to the small screen, especially while performing abdominal scans, small lesions which were located far from the scanner were readily identified. CONCLUSION: Routine ultrasound examinations yield satisfactory results when performed with the new, hand-carried ultrasound system. The low size and weight of this ultrasound system and its good image quality makes it a very usefull tool, especially for examinations of patients at intensive care units and on hospital wards.

Equipment Design↗