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Biomedical subjects

T Fleiter

Publications and source records attributed to T Fleiter.

18 recordsLinked to original sources
PubMed2001

Geometric changes in aortic endografts over a 2-year observation period.

PURPOSE: To report geometric changes in bifurcated aortic endografts observed over a 2-year follow-up period. METHODS: Twenty-two patients (21 men; mean age 68 years, range 57-83) with abdominal aortic aneurysms were treated with an endovascular stent-graft. Follow-up examinations included spiral computed tomographic scanning postoperatively and at 3, 6, 9, 12, 18, and 24 months after treatment. Geometric changes were measured using 3-dimensional reconstructed images in anteroposterior (AP) and lateral projections. Locations for the measurements were the proximal neck, the midportion of the endograft, and the graft limbs at the origin of the iliac arteries. RESULTS: Lateral changes predominated, demonstrating maximum angles on the side of the inserted left limb. For the proximal neck, the stent angle changed by a mean -0.71 degrees in the AP and 4.0 degrees in the lateral projection. At the midgraft, changes were -0.56 degrees for AP and 12.5 degrees for lateral. The right limb showed an angle of 6.43 degrees in AP and -0.43 degrees in lateral, whereas the left limb angles changed 1.38 degrees in AP and 11.71 degrees in the lateral plane after 2 years. There was no statistically significance difference in these changes from baseline. CONCLUSIONS: Aortic endografts are exposed to a significant amount of movement after insertion, but the resultant changes are very inhomogeneous, unpredictable, and ongoing even after 2 years. The most vulnerable location seems to be the attachment zone of the modular graft limb. These geometric changes might be one cause for late complications, including leaks and limb dislocations.

Aged↗
PubMed2000

Vertebral body replacement with a bioglass-polyurethane composite in spine metastases--clinical, radiological and biomechanical results.

Metastatic spine lesions frequently require corpectomy in order to achieve decompression of the spinal cord and restoration of spinal stability. A variety of systems have been developed for vertebral body replacement. In patients with prolonged life expectancy due to an improvement of both systemic and local therapy, treatment results can be impaired by a loosening at the implant-bone interface or mechanical failure. Furthermore, early detection of a metastatic recurrence using sensitive imaging modalities like computed tomography (CT) and magnetic resonance imaging (MRI) is possible in these patients without artefact interference. The aim of our pilot study was to evaluate the clinical applicability and results of a new radiolucent system for vertebral body replacement in the lumbar spine. The system consists of bone-integrating biocompatible materials - a polyetherurethane/bioglass composite (PU-C) replacement body and an integrated plate of carbon-fibre reinforced polyetheretherketone (CF-PEEK) - and provides high primary stability with anterior instrumentation alone. In a current prospective study, five patients with metastatic lesions of the lumbar spine were treated by corpectomy and reconstruction using this new system. Good primary stability was achieved in all cases. Follow-up (median 15 months) using CT and MRI revealed progressive osseous integration of the PU-C spacer in four patients surviving more than 6 months. Results obtained from imaging methods were confirmed following autopsy by biomechanical investigation of an explanted device. From these data, it can be concluded that implantation of the new radiolucent system provides sufficient long-term stability for the requirements of selected tumour patients with improved prognosis.

Adult↗
PubMed1999

[Possibilities of virtual gastrointestinal endoscopy].

Beside the technological development of the modalities, secondary image-reconstruction procedures are of increasing interest for diagnostic purposes and preoperative planning. Recently the simulation of endoscopic views--so called virtual endoscopy--has become available for presenting volume datasets. This new technique, usually based on CT and MRT data-sets, leads to new possibilities for examination of gastrointestinal organs and vasculature. Most interest has focussed on colon examinations, depending on a detailed knowledge of the technical procedure of the examination and additional experience of endoscopic techniques of the examiner. The procedures for the different parts of the gastrointestinal tract are explained.

Endoscopes, Gastrointestinal↗
PubMed1998

[High-resolution virtual laryngoscopy based on spiral CT data].

This pilot study investigated the feasibility and clinical value of high-resolution virtual real-time laryngoscopy based on helical CT data sets. Nine patients with laryngeal pathology (three with tumors of the vocal cords, two laryngeal carcinomas, one with invasion of the larynx by thyroid carcinoma and six subglottic stenoses) underwent examination by helical CT at a collimation of 1 mm. Following acquisition, the images were processed at a workstation with standard visualization software, such that virtual endoscopy (VE) in real time was possible. The images were then compared with the findings of conventional endoscopy. Because of swallowing artifacts, reconstruction failed in 2 of 12 patients. None of the carcinomas of the vocal cords was recognized at VE or in the cross-sectional CT images. VE provided the correct diagnosis in 8 of 12 cases (laryngeal tumors, subglottic stenoses). Virtual laryngoscopy is capable of simulating the visual findings of endoscopy in cases of laryngeal tumors and subglottic stenoses. Small tumors of the vocal cords are not adequately visualized. The major problem affecting results is motion artifacts resulting from involuntary swallowing.

Aged↗
PubMed1998

Coarctations of descending and abdominal aorta: long-term results of surgical therapy.

PURPOSE: Nonarteriosclerotic and nonarteritic descending and abdominal aortic coarctation (DAAC) is a rare disease with a great variety of morphologic findings. The additional affliction of renal and other splanchnic arteries often affords complex corrective procedures. We report on our single-center long-term experiences with operative treatment of this malformation. METHODS: Over a period of 21 years, 15 patients (10 female and 5 male patients; age range, 8 to 57 years) were operated on for DAAC. Six patients had additional stenoses of eight renal arteries, and three had splanchnic arterial obstructions. At 4 to 25 years after the operation, all surviving patients underwent a clinical and a spiral computed tomography examination. RESULTS: There was one intraoperative death due to exsanguination after the rupture of a poststenotic aneurysm of the infrarenal aorta. Fourteen patients were discharged free of symptoms. During follow-up, four repeated operations were necessary for renal arterial bypass stenoses or aneurysms. One late death occurred as the result of an unrelated disease. CONCLUSIONS: Complete operative correction of DAAC usually can be accomplished as a single-stage procedure with low morbidity and mortality rates. The reconstruction of all renal arteries is essential to cure hypertension. Consequent follow-up is recommended for detection of late postoperative complications.

Adolescent↗
PubMed1998

Comparison of virtual and fiberoptic bronchoscopy.

Preoperative diagnostic procedures in the treatment of non-small-cell lung carcinoma (NSCLC) include fiberbronchoscopy (FBS) and CT scanning of the thorax and abdomen. The introduction of double-detector helical computed tomography has led to improved image resolution which allows three-dimensional reconstruction of the bronchial tree. A special computer simulation provides a virtual endoscopic view into the inner surface of the bronchial system. In order to determine whether the so-called virtual bronchoscopy (VBS) accurately reflects the anatomic situation of the bronchial tree, neoplastic lesion, and postoperative control of sleeve resections, we performed a virtual bronchoscopy in 24 patients with NSCLC and in 6 patients following sleeve resections and compared the results with the findings of fiberoptic bronchoscopy. An anatomic computer simulation of the bronchial tree was created in 100% of the investigated patients. Central tumor stenosis or occlusion was visualized by VBS as well as by FBS. In peripheral tumorous lesions VBS revealed the correct diagnosis in only 75%. VBS, however, enables viewing beyond the stenosis. FBS remains the gold standard in the endoscopic diagnostic procedures, showing not only airway patency but also mucosal changes in the vicinity of the tumorous lesion. VBS, however, gives further information about the poststenotic area in occlusive main bronchus stenosis. Furthermore, adequate control investigation of airway patency in patients following sleeve resections or stent implantation can be performed by VBS.

Bronchoscopy↗
PubMed1997

[A new method in the determination of individual delay time in bolus application in spiral CT].

Helical-CT examinations, particularly CT angiography, require precise timing between the examination procedure and the individual dynamics of contrast medium distribution in the arteriovenous system of the patient. The necessary delay between contrast medium injection and onset of has usually been either estimated or determined by means of an additional helical CT examination. The present paper introduces a new technique which allows bolus analysis without an additional scan. Prior to a CT angiography with 10 patients, two techniques for bolus analysis (BA) were compared. Prior to diagnostic contrast medium enhanced examination, a native (BA I) and a dynamic (BA II) examination were performed. Ten seconds prior to the start of each examination, a 10 ml test bolus was applied with an injection flow rate of 3 ml/s. Both examinations lasted for 30 s. During BA I, increase in attenuation in the aorta was compared at different sites, during BA II consistently at the same site. Comparison of the individual peak times yielded a coefficient of correlation of r = 0.926. The median value for BA I was 18.4 +/- 5.4 s and 19.2 +/- 4.5 s for BA II. The difference between measurement of peak time was 1.2 +/- 1.16 s. This modified technique for bolus analysis during the primary native scan of the upper abdominal organs permits calculation of the required individual delay time between contrast medium application and scan start: no additional examination is required and the method can be performed with any helical CT unit.

Adult↗
PubMed1997

Comparison of real-time virtual and fiberoptic bronchoscopy in patients with bronchial carcinoma: opportunities and limitations.

OBJECTIVE: Both helical CT and fiberoptic bronchoscopy are used in the staging of pulmonary tumors for therapeutic decision making. The improved resolution offered by helical CT has led to the clinical use of three-dimensional reconstruction techniques such as virtual bronchoscopy. We tested this new simulated endoscopic view of inner organ surfaces and compared it with corresponding fiberoptic examinations of the tracheobronchial system. SUBJECTS AND METHODS: Twenty patients with malignancies of the lung and mediastinum were examined with both virtual bronchoscopy and fiberoptic bronchoscopy. Both examinations were reviewed by radiologists and surgeons familiar with fiberoptic bronchoscopy. Virtual bronchoscopy was calculated and reconstructed from the cross-sectional images on a separate workstation. Stenoses and tumor infiltration were classified from the fiberoptic examination. These results were compared with the virtual bronchoscopy findings. RESULTS: Virtual bronchoscopy of diagnostic quality was achieved in 19 of 20 patients. High-grade stenoses were revealed equally well with virtual and fiberoptic techniques. Virtual bronchoscopy offered the advantage of being able to visualize areas beyond even high-grade stenoses. However, on virtual bronchoscopy discrete infiltration or extraluminal impression was not visible in five patients. In another patient, strong heart pulsation produced motion artifacts that prevented evaluation of the reconstruction. CONCLUSION: Virtual bronchoscopy represents a new noninvasive method for evaluating helical CT findings. In comparison with fiberoptic bronchoscopy, virtual bronchoscopy offers the advantage of being able to visualize areas beyond even high-grade stenoses. In addition to the limited view of fiberoptic bronchoscopy, extraluminal causes of lumen compressions can be analyzed in the cross-sectional images and evaluated together with the virtual representation. However, it was not possible to detect small infiltrations with virtual bronchoscopy. This new representation of helical CT data might be helpful for postoperative follow-up examinations, such as after stent implantation, and can be carried out without additional risk to the patient. Radiologists do need special fiberoptic bronchoscopy knowledge and experience with three-dimensional-reconstructions to differentiate between real stenoses and artificial stenoses that might be caused by pulsation artifacts.

Artifacts↗
PubMed1997

[Atypical aortic coarctations in type I neurofibromatosis].

From 1971 through 1996, 16 patients were operated on for atypical aortic coarctation. Three of them (two women, 18 and 27 years old, one boy, 13 years old) had typical signs of neurofibromatosis type I (NF1). All had renovascular hypertension due to suprarenal and/or interrenal aortic stenosis. Two had additional bilateral renal artery stenoses, one with a poststenotic aneurysm. In all patients a thoraco-abdominal aorto-aortic bypass was implanted. The renal artery stenoses were bridged by two aorto-renal, a prothesio-renal, and a spleno-renal bypass. Only one kidney had to be explanted 13 years after revascularization for a recurring hilar aneurysm after ex-situ reconstruction was found to be impossible. At their last follow-up examination (at 16, 14, and 9 years) all patients were normotensive without medication and had normal serum-creatinine measurements. Angiography or spiral-CT done in all patients showed normal function of all bypasses. In literature we found another 27 patients with neurofibromatosis operated on for atypical aortic coarctation. In these young and otherwise healthy patients, even complex reconstructions can be performed with a low rate of complications and excellent long-term results. Surgical therapy of all relevant stenoses (at best in a single procedure) is necessary for complete relief of renovascular hypertension. Consequent follow-up is advised for the detection of possible late complications, especially after exclusion of aneurysms.

Adolescent↗
PubMed1996

[Virtual cystoscopy based on spiral CT data].

Simulation of three-dimensional cystoscopy based on helical CT scan data in real-time in patients with tumours of the urinary bladder. In three patients with histologically confirmed carcinoma of the urinary bladder, a helical CT scan with double detector technology was carried out preoperatively. A native scan was first performed, followed by an examination in the early contrast medium enhanced phase. After adequate contrasting of the urinary bladder (30 minutes latency), further images were acquired. These data were transferred to a separate graphic computer workstation and reconstructed. The results were then compared with the cystoscopic and pathohistological findings. All tumours of the urinary bladder identified at fiberoptic cystoscopy were also visualised by virtual cystoscopy. The best reconstruction results were obtained from data acquired after the 30-minute latency period. Virtual cystoscopy represents an interesting option in helical CT scanning, which is able to visualise polypoid tumours of the urinary bladder. Its clinical relevance, however, must be demonstrated in studies with a larger number of patients examined.

Aged↗
PubMed1994

Pulmonary nodules in spiral volumetric and single slice computed tomography.

Single slice acquisition of conventional CT and volume scanning of spiral volumetric CT are compared in terms of detection and assessment of pulmonary nodules. Spiral CT is supposed to be superior to conventional CT in detecting all lung nodules by scanning the complete lung volume, while conventional CT may miss nodules due to inconsistent levels of inspiration for single slices. Different technical procedures of spiral CT may change the imaging of nodules and other findings. Fifty-two patients with known or suspected lung nodules were examined by conventional CT and spiral CT. Number and size of lung nodules and imaging of other pulmonary findings were registered independently by two radiologists. Spiral CT showed 15 lung nodules not seen on conventional CT, and missed one nodule. Spiral CT imaging of nodules was superior in some cases (characterisation of benign nodules) because complete scanning provided more information than conventional CT. It was worse in some cases (small nodules, fibrosis, small pleural effusion) due to the greater partial volume effect and less mAs. Technically improved spiral CT with longer scanning facilities and a 180-degree algorithm may be able to replace conventional CT for this indication.

Humans↗
PubMed1994

[Evacuation proctography: physiological variability and clinical relevance of the anorectal angle and the position of the pelvic floor].

Evacuation proctography is an important imaging method for the investigation of abnormalities of defecation. For this procedure, the most commonly carried out measurements are the ano-rectal angle and the position of the pelvic floor. The given mean values and the physiologically acceptable deviations vary just as much as the perceived clinical value of these measurements. 173 evacuation proctograms were evaluated in a prospective study; the subjective abnormalities were correlated with clinical findings. No significant correlation between the measurements from the proctograms and the clinical findings could be determined. The clinical relevance of these measurements is, therefore, uncertain.

Adult↗
PubMed1993

[Dynamic 3D imaging of peripheral vessels using color-coded Doppler ultrasound].

3-D reconstructions are established as post-processive methods in CT and MRI. However, these methods permit assessment of morphological findings only. To uncover functional relations on the basis of ultrasound would also be of paramount interest. For this purpose a specific method was developed for the acquisition and time-coded 3-D reconstruction in the diagnosis of peripheral vessels, in particular of the extracranial carotid artery. An imaging device (Acuson 128 XP) with a 7.5 MHz probe, a PC-controlled stepping motor and an imaging system (Kontron Mipron) was used. Data acquisition was performed scan-by-scan in a transverse plane with a slice thickness of 1 mm along the vessel. In every slice position multiple ECG-trigger delays during the cardiac cycle were used. Data were transferred to the imaging system via videosignal. In preliminary clinical application this dynamic 3-D reconstruction method yielded good spatial resolution of the complex physiological flow phenomena in the carotid bifurcation.

Blood Flow Velocity↗
PubMed1992

[Portal computed tomography. Methodology and indications].

CT arterioportography (CTAP) requires intra-arterial contrast material via the superior mesenteric (splenic) artery. Malignant hepatic tumors are characterized by arterial vascularization and only minimal portal blood supply. Portal contrast therefore reveals small tumors with a high sensitivity of 68-87%. Sensitivity is higher in metastatic tumors than in hepatocellular carcinomas. CTAP is the method of choice for evaluation of the number, size and location of hepatic tumors prior to surgical intervention. If the findings are unclear, additional magnetic resonance imaging and sonography during the operation are useful.

Contrast Media↗