Biomedical subjects

G A Krombach

Publications and source records attributed to G A Krombach.

At least 19 recordsLinked to original sources

PubMed2003

Posterior semicircular canal dehiscence: a morphologic cause of vertigo similar to superior semicircular canal dehiscence.

The aim of this study was to assess imaging findings of posterior semicircular dehiscence on computed tomography and to evaluate incidence of posterior and superior semicircular canal dehiscence in patients presenting with vertigo, sensorineuronal hearing loss or in a control group without symptoms related to the inner ear. Computed tomography was performed in 507 patients presenting either with vertigo ( n=128; 23 of these patients suffered also from sensorineuronal hearing loss), other symptoms related to the inner ear, such as hearing loss or tinnitus ( n=183) or symptoms unrelated to the labyrinth ( n=196). All images were reviewed for presence of dehiscence of the bone, overlying the semicircular canals. Twenty-nine patients had superior semicircular canal dehiscence. Of these patients, 83% presented with vertigo, 10% with hearing loss or tinnitus and the remaining 7% with symptoms unrelated to the inner ear. In 23 patients dehiscence of the posterior semicircular canal was encountered. Of these patients, 86% presented with vertigo, 9% with hearing loss or tinnitus and 5% with symptoms unrelated to the inner ear. Defects of the bony overly are found at the posterior semicircular canal, in addition to the recently introduced superior canal dehiscence syndrome. Significant prevalence of vertigo in these patients suggests that posterior semicircular canal dehiscence can cause vertigo, similar to superior semicircular canal dehiscence.

Case-Control Studies↗

PubMed2002

The petromastoid canal on computed tomography.

The objective was to assess visibility and anatomy of the petromastoid canal in high-resolution CT. Computed tomography images of 188 patients were reviewed for delineation of the petromastoid canal. This bony canal connects the mastoid antrum with the cranial cavity and houses the subarcuate artery and vein. The diameter, obtained in the middle portion of the canal, was compared with the diameter of the vestibular and cochlear aqueduct in all patients, and absolute values measured in 20 cases. Collimation was 1 mm in 164 and 2 mm in 24 examinations. Additionally, temporal bone of a cadaver was imaged and microdissected. The petromastoid canal was identified bilaterally in all 164 scans that were obtained with a slice thickness of 1 mm. In 5 of the 24 patients imaged with a collimation of 2 mm, the canal was not visible, most probably due to partial-volume effects. The petromastoid canal had the same diameter as the cochlear aqueduct in 42/44 (right/left), exceeded it in 66/61 and was smaller in 75/78 cases. In comparison to the vestibular aqueduct it had an equal diameter in 38/41 (right/left), exceeded it in 63/61, and was rated as smaller in 82/81 temporal bones. Diameters for the canals were: petromastoid canal 0.51+/-0.04 mm; cochlear aqueduct 0.57+/-0.03; and vestibular aqueduct 0.63+/-0.06 mm. Microdissection of the specimen revealed the entire course of the canal and demonstrated a similar appearance of the structure as in the images. The petromastoid canal can easily be identified on high-resolution, thin-slice CT images. Knowledge of the anatomy of this bony canal prevents misinterpretation as pathological structure, such as fracture line, which might occur if this structure is not known.

Adult↗

PubMed2002

Virtual endoscopy combined with intraoperative neuronavigation for planning of endoscopic surgery in patients with occlusive hydrocephalus and intracranial cysts.

We assessed the clinical value of MR ventriculoscopy (virtual endoscopy, VE) combined with image-guided frameless stereotaxy for endoscopic surgery of occlusive hydrocephalus and intracranial cysts. VE was obtained in 20 patients with hydrocephalus and three with intracranial cysts. All surgical operations were endoscopic. The path of the rigid endoscope to the target point was planned using neuronavigation. VE was carried out along the same trajectory retrospectively in 20 cases and prospectively in three. The results were analysed for demonstration of anatomical landmarks and structures at risk. VE was successful in all patients. Possible obstacles to endoscopic access to the lamina terminalis and the basal cisterns and structures at risk, such as the basilar artery, were clearly shown in relation to the direction of the endoscope. However, the floor of the third ventricle and septum pellucidum were not clearly seen and possible abnormalities could therefore not be appreciated. VE can provide realistic simulation of endoscopic third ventriculostomy and cystostomy. The appropriate trepanation point and trajectory of the endoscope can be assessed with regard to the size of the foramen of Monro and the position of vulnerable structures. This simulated trajectory can be adapted to the field of operation by image-guided neuronavigation. This regime may potentially reduce the risk of damage to intracranial structures.

Adolescent↗

PubMed2002

Error analysis in cranial neuronavigation.

Neuronavigation systems are now an important component of many modern neurosurgical treatment strategies. Their support facilities intraoperative orientation and makes neurosurgical operations more precise and less traumatic. Computer-aided neurosurgery is definitively not a temporary fashionable phenomenon, the concept of neuronavigation is here to stay. This report summarizes a ten-years-long experience and presents an error analysis of 108 failures (12.4 %) in a total of 874 image-guided cranial neurosurgical procedures with an arm-linked (mechanical) system and two different infrared-light emitting (optical) systems. The application of neuronavigation incurs multiple reasons for pitfalls because of the complex man-machine interface. Principally, we have to differentiate two types of errors: "machine made errors" due to soft- or hardware failure and "man made errors" generally, due to inadequate handling of the navigation system. The error analysis demonstrated that the so-called human interface plays the main role causing a high error rate.

Bias↗

PubMed2002

[MR contrast media for cardiovascular imaging].

MR contrast media improve the diagnostic capability of MRI and MRA. They are used in the discrimination of viable and non-viable myocardium, transmural and non-transmural infarction, occlusive and reperfused infarction and for measurement of myocardial perfusion. Currently, clinical studies are almost completely restricted to the use of extracellular non-specific MR contrast media (i. e., Gd-DTPA, Gd-DTPA,-BMA, Gd-BOPTA, Gd-D03A). However, the feasibility of using intravascular, necrosis specific or intracellular MR contrast media or endogeneous substrates as specific MR contrast media in cardiovascular imaging has been demonstrated in experimental and a few clinical studies. Intravascular contrast media (i. e., MS-325 or NC100150 Injection) allow assessment of microvascular integrity and performance of MR angiography. Necrosis specific contrast media (i. e., Gadophrin-2) have been used for sizing the extent of infarcted myocardium while intracellular contrast media (i. e., Mn-DPDP) delineate viable myocardium. Endogenous contrast media (i. e., Deoxyhemoglobin, Na (+) or K (+)) have been tested for detecting the alterations in concentrations of these ions in infarcted myocardium and for perfusion measurements. Furthermore, intravascular MR contrast media may be useful for MRA and MRI guided cardiovascular interventions.

Contrast Media↗

PubMed2002

[Relevance of colour-duplex echography for detection and therapy of recurrences in the follow-up of head and neck cancer].

BACKGROUND: Head and neck malignancies have a high rate of recurrences. Since the prognosis is often limited an early detection and therapy onset is essential for survival. This study surveys the relevance of regular colour-duplex echography examinations in the follow-up for detection and therapy of recurrent head and neck carcinomas. PATIENTS AND METHODS: In a prospective non-randomized study 43 patients were surveyed over a mean observation period of 28 (8-44) months. In addition to clinical and colour-duplex echography (CDS) examinations, computed tomography (CT) and positron-emission-tomography using 18fluorodeoxyglucose (PET) were performed. RESULTS: A recurrence was detected in 17/43 (39.5 %) patients. The median survival was 42 months. CDS was the most reliable procedure for the diagnosis of regional recurrences with an accuracy of 94.2 %. Sensitivity and specificity of CDS for the diagnosis of all recurrences was found to be 80 % and 78,6 % respectively. CT yielded identical results. In PET sensitivity was 82.4 % and specificity was found to be 88.4 %. In clinical examinations including panendoscopy sensitivity was 64.7 % only. In 7/17 recurrences a therapy was performed with curative intention. In 4 cases an early diagnosis by CDS contributed to a successful therapy. CONCLUSION: CDS is the imaging procedure of choice for the routine follow-up of head and neck cancer patients. In order to perform a comprehensive assessment of the head and neck region, for re-staging and to exclude second primary tumours additional (pan)endoscopy is necessary. CDS supports due to a high resolution and reliability an early therapy onset and a minimal invasive therapy. Thus, this procedure can significantly contribute to the successful treatment of recurrences in head and neck cancer.

Adenocarcinoma↗

PubMed2001

Virtual MRI endoscopy: detection of anomalies of the ventricular anatomy and its possible role as a presurgical planning tool for endoscopic third ventriculostomy.

BACKGROUND: Many anatomical anomalies have the potential to impair the efficacy of endoscopic third ventriculostomy (ETV) and increase the surgical morbidity. By virtual magnetic resonance imaging (MRI) endoscopy, the real endoscopic view into the ventricular system can be simulated. It was the objective of the present study to investigate if this simulation is sensitive enough to detect anatomical anomalies of the ventricular system. METHOD: In 18 hydrocephalic patients, first neuronavigationally guided ETV, then virtual MRI endoscopy were performed. This study design allowed for selection of a path for virtual MRI endoscopy, which was identical to that used during surgery, making the real and the virtual view on anatomical structures of the ventricular system highly comparable. It was investigated whether the intra-operatively identified anatomical anomalies could likewise be depicted on virtual MR endoscopic images. FINDINGS: Seven anatomical variants (not enlarged interventricular foramen n=2, atrophic corpus callosum and split fornical bodies n=1, narrow retroclival space n=1, prominent basilar tip n=1, opaque and thick/atypically declining third ventricular floor n=2) were encountered in 5 of the 18 patients during surgery. The five variants of the non-membraneous structures were identified by virtual MRI endoscopy (sensitivity 71%), whereas the anatomical variants of the third ventricular floor were missed. Both the normal as well as the variant third ventricular floor could not be visualised and appeared as a defect. Through this artefact, the anatomy of the major vessels in the interpeduncular cistern could be assessed. INTERPRETATION: The sensitivity of virtual MRI endoscopy for detection of anatomical variants of the ventricular system is low. Its potential usefulness as a presurgical planning tool inspite of this low sensitivity rate is discussed.

Adolescent↗

PubMed2001

US-guided nephrostomy with the aid of a magnetic field-based navigation device in the porcine pelvicaliceal system.

PURPOSE: To assess the technique and feasibility of ultrasound (US)-guided nephrostomy performed with the aid of a magnetic field-based navigation device. MATERIALS AND METHODS: Twelve percutaneous nephrostomy procedures were performed in seven domestic pigs under real-time US guidance employing a navigation system. Two magnetic field sensors registered the actual position of the puncture needle and the US transducer. The actual needle position and the aimed puncture tract were graphically projected into the real-time US images, allowing exact navigation of the needle. After placement of the needle into the renal pelvis, the nephrostomy tube was inserted by means of the Seldinger technique. RESULTS: The puncture procedure was successfully performed in each case. The renal pelvis was punctured in a single attempt in 10 of 12 cases. In two cases, multiple attempts were necessary because bending of the puncture needle led to inaccuracies of the navigation system. With exception of two small perirenal urinomas, no complications were seen. CONCLUSIONS: The magnetic field-based navigation device allows easy and accurate performance of nephrostomy guided solely by US.

Animals↗

PubMed2001

[Magnetic resonance tomography imaging of the inner ear of patients with sensorineural hearing loss or vertigo].

BACKGROUND: Progress in surgical techniques in the temporal bone has lead to the demand of exact delineation of this complex anatomical region for preoperative planning. The aim of this study was to assess the potential of a three-dimensional T2 weighted turbo-spin-echo-sequence to depict anatomical details and pathological changes of the inner ear. METHODS: Twenty-five patients presenting with sensori-neural hearing loss and/or vertigo were included in this study. A T2 weighted turbo-spin-echo-sequence was carried out on a 1.5 T imager, employing a surface coil with a diameter of 8 cm. The scan parameters were set as follows: TR 2000, TE 500, scan matrix 128 x 128, field of view 90 mm, slice thickness 0.66 mm, NSA 4. In addition, 3D maximum-intensity-projections (MIP) were created, using these data as source images. RESULTS: Image quality was excellent in all 25 cases. The 2.5 cochlear windings, modiolus, vestibule with saccule and utricle all three semicircular canals, crus commune and the facial nerve and vestibulocochlear nerve in the inner auditory canal were clearly delineated in all patients. The cochlear aqueduct was seen in 32% (8 cases), while the vestibular aqueduct was delineated in 16% (4 cases) in this series. In MIP, the entire labyrinth was shown in a single view. In 22 patients regular morphology was found, while in three cases pathological changes were detected (an enlarged vestibular aqueduct and saccus in one patient, partial fibrous obliteration of the labyrinth in two patients). CONCLUSIONS: The introduced TSE sequence can be used to delineate the anatomy of the inner ear as well as pathological changes. The technique appears to be useful for preoperative planning.

Adolescent↗

PubMed2001

[Panorama ultrasonography of the abdominal wall for delineation of the anatomy and diagnosis of pathological findings].

PURPOSE: To assess extended field-of-view sonography for delineation of the anatomic structures of the abdominal wall and for the diagnosis of hernia. MATERIAL AND METHODS: In 34 cases (24 probands, 10 patients with abdominal wall defects) extended field-of-view sonography of the abdominal wall was performed with a 7.5 MHz transducer. Dynamic alignment of real-time images allows for depiction of regions of up to 60 cm in a single extended field-of-view image. A standardized axial image was obtained above and below the arcuate line and at the level of the defect, respectively. All images were evaluated by two blinded readers regarding the visibility of the anatomic structures and the delineation and extent of pathological changes. RESULTS: The abdominal wall was delineated with extended field-of-view sonography in all patients with a good image quality. The linea alba, the rectus muscle and the three lateral abdominal muscles, the rectus sheath, the peritoneum, and the subcutaneous fatty tissue were visible. In the patients with abdominal wall defects, the hernial sac with its contents, the extension of the defect, and the surrounding structures were clearly delineated. CONCLUSION: Extended field-of-view sonography allows for easily surveyed and reproducible documentation of the ultrasound examination of the abdominal wall. It is especially useful for the preoperative planning in patients with abdominal wall defects.

Abdominal Muscles↗

PubMed2001

[The influence of motion artifacts conditioned by reconstruction, on the coronary calcium score in multislice spiral CT].

UNLABELLED: The influence of motion artifacts conditioned by reconstruction, on the coronary calcium score in multislice spiral CT. PURPOSE: A major problem of the quantification of coronary calcifications is a high variability of the coronary calcium score between recurrent examinations and different observers. Aim of our study is to evaluate the influence of different RR-intervals on the coronary calcium score utilizing retrospectively gated Multislice Spiral CT (MSCT) data sets. MATERIALS AND METHOD: 50 consecutive patients underwent MSCT examination (Somatom Volume Zoom, Siemens, Forchheim, G) utilizing a standardized scan protocol (4 x 2.5 mm collimation, 3 mm increment, tube current 133 mAs, tube voltage 120 kV). Retrospectively gated image reconstruction was performed every 10 % of the RR interval. Coronary calcification was evaluated by the Agatston score. Coronary risk assessment was performed in all patients with image reconstruction beginning at 80 % of the RR interval. The reconstruction intervals with the least motion artifacts were identified and chosen as reference for a reevaluation of the coronary risk. The results of different reconstruction times were compared. RESULTS: The mean calcium score was 551.6. The calcium score varied between 512.2 (90 %) and 571.7 (70 %), depending on the image reconstruction interval. Compared to the mean calcium score a new classification of the coronary risk was necessary in 7/50 of the patients at 80 % reconstruction interval, and in 2/50 of the patients at 50 % of the RR interval, respectively. CONCLUSION: Movement of the coronary arteries at different image reconstruction intervals has an important influence on the coronary calcium score. Based on our data, we propose image reconstruction at 50 % of the RR interval for evaluation of the coronary calcium score by MSCT.

Adult↗

PubMed2000

Potential of a new laser target system for percutaneous CT-guided nerve blocks: technical note.

A prototype of a laser target device was used for CT-guided nerve blocks in a preliminary series of nine interventions. The system provides guidance from any possible approach. High accuracy of needle insertion was achieved; the average deviation of the planned from the actual angle was 1.4 degrees. The target device is valuable for facilitating minimally invasive therapy and can decrease the time required for the procedure.

Adult↗

PubMed2000

[Initial experiences with a new optical target system (SimpliCT) for CT-guided punctures].

PURPOSE: To evaluate the prototype of a new optical target device for CT-guided punctures and interventions. METHODS: An optical target device for CT-guided punctures was applied in 24 interventions. The system consists of a laser target device mounted on a stand. The biopsy needle is adjusted according the course of a laser beam. The target angle has to be adjusted on the laser unit. The laser carrier can be moved along an 90 degrees-angled rail, allowing punctures from any angle in plane. Furthermore, angulation in the z-plane is possible, supporting interventions with gantry tilt. Size and depth of the target lesions, the planned and the actual angle of the inserted needle, the numbers of corrections of the needle position, and the time required for the puncture were evaluated. The user rated the benefit of the system and the ease of the application. RESULTS: All 24 interventions were carried out successfully. The mean difference between the planned and the actual angle of the needle was 1.3 degrees (SD: 0.7 degree). The system was considered as easy to handle and as a valuable aid. CONCLUSIONS: The laser target device is a simple navigation system which allows accurate positioning of a needle. Requiring an acceptable low preparation time, it easily can be integrated into the procedure.

Adult↗

PubMed2000

[Nuclear magnetic resonance tomography imaging and functional diagnosis of the eustachian auditory tube].

PURPOSE: To develop and evaluate a protocol for the anatomic depiction and functional testing of the auditory tube with the use of MR imaging. METHODS: Eleven volunteers were included into this study. For the morphological assessment, the imaging protocol included axial and coronal T2-weighted turbo-spin echo sequences (TR/TE = 3194/100 ms) and a T1-weighted gradient echo sequence (TR/TE = 42/4.6 ms). For the functional test a dynamic turbo-gradient echo sequence (TFE) with spectral fat suppression (TR/TE = 15/6.2 ms; 4 sec) was obtained using the single slice technique before and during the Valsalva manoeuvre. RESULTS: With multi-slice sequences, the osseous part of the auditory tube, the tubal cartilage (middle and lateral lamina), the ciliated epithelium, Ostmann's adipose body and the levator and tensor veli palatini muscles were delineated in all cases. During the Valsalva test, opening of the auditory tube was demonstrated in 20 of the 22 investigated sides using the dynamic TFE single slice sequence. CONCLUSIONS: The introduced MRI protocol allow visualization of the opening of the auditory tube and provides detailed anatomical information of the nasopharynx. Comprehensive morphological and functional evaluation of the auditory tube becomes possible within a single examination'.

Adult↗

PubMed2000

[Results of pretherapeutic lymph node diagnosis in head and neck tumors. Clinical value of 18-FDG positron emission tomography (PET)].

BACKGROUND: Histological studies demonstrate that there is a high percentage of occult nodal metastasis in head and neck malignomas. Patients with positive lymph nodes have a comparatively worse prognosis. A neck dissection is required in these cases. By demonstrating morphological abnormalities, imaging procedures like ultrasound, computer tomography (CT), and magnetic resonance imaging (MRI) can provide important initial informations about possible malignant alteration of the lymph nodes. Positron emission tomography (PET) allows functional metabolic imaging of a suspected tumor site. The aim of this study was a comparative evaluation of different diagnostic procedures with special emphasis on the value of PET in the pretherapeutic diagnosis of nodal spread in head and neck cancer. PATIENTS AND METHODS: Forty patients (28 male and 12 female) with a suspected malignoma in the head and neck region underwent clinical examination including palpation of the neck sides, ultrasound, CT, and PET to detect a nodal spread of the malignancy. Fifty neck dissections were performed in 28 patients. Lymph node biopsies were performed in the remaining patients. The results of the diagnostic procedures were compared to the histology and the clinical course of the patients. The mean follow-up period was 12.5 months. RESULTS: A nodal metastasis was verified in 35% of all cases. Sensitivity of all imaging procedures including PET was 82%. Palpation had a sensitivity of only 61%. Specificity was 85% for ultrasound, 94% for CT and palpation, and 87% for PET. PET produced false negative results in 13.4% of all cases. Inflammation was detected in these cases. The positive predictive value was marginally better for PET than for ultrasound (77% vs. 75%). It proved to be lower than the values for palpation (86%) and CT (88%). Negative predictive value was 90-91% for all imaging procedures. CONCLUSION: In the primary diagnosis of nodal alterations in the head and neck region, a PET scan has the same diagnostic value as ultrasound or CT. By imaging the metabolism of a suspected nodal metastasis, PET can help to improve the assessment of regions with uncertain anatomic features. To avoid false positive results, acute and chronic inflammatory alterations have to be ruled out before the PET imaging.

Aged↗

PubMed2000

MRI of the inner ear: comparison of axial T2-weighted, three-dimensional turbo spin-echo images, maximum-intensity projections, and volume rendering.

RATIONALE AND OBJECTIVES: To compare the ability of axial T2-weighted, three-dimensional, turbo spin-echo (3D TSE) images, targeted maximum-intensity projections (MIPs), and 3D volume reconstructions to depict anatomic details of the labyrinth. METHODS: In 24 volunteers, 3D TSE images were obtained. MIPs and 3D volume reconstructions were performed from the acquired data. All images were evaluated by three radiologists independently regarding the visualization of the different anatomic structures. RESULTS: In the axial slices, most anatomic details were visible in comparison with observations by the other modalities. The 2.5 windings of the cochlea were best depicted on the MIPs. Volume reconstructions rendered excellent spatial information regarding the vestibule and semicircular canals and were the only technique that demonstrated all three ampullae in all cases. CONCLUSIONS: Axial TSE images, MIPs, and 3D volume reconstructions are complementary modalities that provide different information. Our results suggest that improved diagnostic information can be obtained by applying these volume visualization reconstruction techniques.

Adult↗

PubMed1999

[Magnetic-field-based navigation system for ultrasound-guided interventions].

PURPOSE: To describe a new magnetic field-based navigation system for ultrasound-guided interventional procedures. METHODS: The navigation system supports biopsies either in plane or out of plane. To evaluate the accuracy of the system, targets in four standard silicone phantoms were punctured. Six cystic and six solid lesions were present in every phantom. The success of the puncture was controlled by aspiration of the content of the lesions, which was coloured. Furthermore, liver lesions of different sizes (2-6 mm) and depths (3-6 cm) were produced by injecting a viscous fluid and punctured in three swine carcasses. Functions of the gallbladder and nephrostomies were carried out as well. RESULTS: All 48 targets were successfully punctured using the in plane and out of plane modus in the phantom. In the carcasses all 16 lesions were reached in plane. In the out of plane modus two 6 cm deep lesions were not reached. All other 14 biopsies were successful. Nephrostomy of the not dilated renal pelvis and punction of the gallbladder were successfully carried out. CONCLUSIONS: The described navigation system is a promising tool for fast and safe performance of ultrasound-guided interventional procedures.

Biopsy↗

PubMed1998

Intraoperative localization of functional regions in the sensorimotor cortex by neuronavigation and cortical mapping.

Surgery of lesions within the central region requires exact intraoperative anatomical orientation and knowledge of the position of functional cortical regions to minimize the surgical trauma and to avoid postoperative neurological deficits. We combined somatosensory evoked potential (SSEP) phase reversal and/or cortical electrical stimulation with neuronavigation in 26 patients for localization and visualization of functional cortical areas and their anatomical site in relation to the lesion. After location of the central sulcus by means of SSEP phase reversal, the precentral gyrus was electrically stimulated to detect functional motor regions. Electrode position was documented, and the functional regions were related to the site of the lesion using a specially developed neuronavigation system. In 11 of 15 patients the central fissure was located with SSEP phase reversal. Electrical stimulation yielded motor evoked potentials in 23 of the total 26 patients. The anatomical site of these functional regions and their relation to the lesion were evaluated with the neuronavigation system. The precentral gyrus, central sulcus, and postcentral gyrus could be identified in all 23 cases. The combination of intraoperative electrophysiological mapping and neuronavigation provides safe and reliable localization of the sensorimotor cortex. This technique is a promising tool to minimize the risk of surgically caused sensory and motor deficits.

Adult↗