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Biomedical subjects

G Wendt

Publications and source records attributed to G Wendt.

At least 19 recordsLinked to original sources
PubMed2001

Effect of focal and nonfocal cerebral lesions on functional connectivity studied with MR imaging.

BACKGROUND AND PURPOSE: Functional connectivity MR (fcMR) imaging is used to map regions of brain with synchronous, regional, slow fluctuations in cerebral blood flow. We tested the hypothesis that focal cerebral lesions do not eradicate expected functional connectivity. METHODS: Functional MR (fMR) and fcMR maps were acquired for 12 patients with focal cerebral tumors, cysts, arteriovenous malformations, or in one case, agenesis of the corpus callosum. Task activation secondary to text listening, finger tapping, and word generation was mapped by use of fMR imaging. Functional connectivity was measured by selecting "seed" voxels in brain regions showing activation (based on the fMR data) and cross correlating with every other voxel (based on data acquired while the subject performed no task). Concurrence of the fMR and fcMR maps was measured by comparing the location and number of voxels selected by both methods. RESULTS: Technically adequate fMR and fcMR maps were obtained for all patients. In patients with focal lesions, the fMR and fcMR maps correlated closely. The fcMR map generated for the patient with agenesis of the corpus callosum failed to reveal functional connectivity between blood flow in the left and right sensorimotor cortices and in the frontal lobe language regions. Nonetheless, synchrony between blood flow in the auditory cortices was preserved. On average, there was 40% concurrence between all fMR and fcMR maps. CONCLUSION: Patterns of functional connectivity remain intact in patients with focal cerebral lesions. Disruption of major neuronal networks, such as agenesis of the corpus callosum, may diminish the normal functional connectivity patterns. Therefore, functional connectivity in such patients cannot be fully demonstrated with fcMR imaging.

Agenesis of Corpus Callosum↗
PubMed2000

Implementing a Java-based image and report distribution system in a non-picture archiving and communication system environment.

The benefits and pitfalls of implementing a Java-based system to distribute results and images to referring physicians are addressed. The basic requirements for and barriers to implementing this system in a non-picture archiving and communication system (PACS) environment will also be discussed. The majority of radiology information systems (RIS) and hospital information systems (HIS) currently only distribute the text data for radiology examinations. This is generally adequate for low-acuity exams in a relatively healthy patient; however, many clinicians prefer to review images so they can correlate the reported findings with the image data, as well as review the exam themselves. A web-based solution eliminates the need for specialized review software and/or hardware at each review site. In addition, there is no need for support personnel to travel to each site to set up and upgrade software.

Data Display↗
PubMed2000

Active hair growth (anagen) is associated with angiogenesis.

After the completion of skin development, angiogenesis, i.e., the growth of new capillaries from pre-existing blood vessels, is held to occur in the skin only under pathologic conditions. It has long been noted, however, that hair follicle cycling is associated with prominent changes in skin perfusion, that the epithelial hair bulbs of anagen follicles display angiogenic properties, and that the follicular dermal papilla can produce angiogenic factors. Despite these suggestive observations, no formal proof is as yet available for the concept that angiogenesis is a physiologic event that occurs all over the mature mammalian integument whenever hair follicles switch from resting (telogen) to active growth (anagen). This study uses quantitative histomorphometry and double-immunohistologic detection techniques for the demarcation of proliferating endothelial cells, to show that synchronized hair follicle cycling in adolescent C57BL/6 mice is associated with substantial angiogenesis, and that inhibiting angiogenesis in vivo by the intraperitoneal application of a fumagillin derivative retards experimentally induced anagen development in these mice. Thus, angiogenesis is a physiologic event in normal postnatal murine skin, apparently is dictated by the hair follicle, and appears to be required for normal anagen development. Anagen-associated angiogenesis offers an attractive model for identifying the physiologic controls of cutaneous angiogenesis, and an interesting system for screening the effects of potential antiangiogenic drugs in vivo.

Animals↗
PubMed1999

Pneumonectomy in cystic fibrosis.

A 17-year-old boy and a 12-year-old girl with cystic fibrosis (forced expiratory volume in 1 sec, 36% and 14% of predicted values, respectively) developed severe right-sided lung infections with abscess formations and complete atelectases unresponsive to medical therapy. In both patients, unilateral emergency pneumonectomy resulted in rapid clinical improvement. Despite her severe underlying lung disease, the girl experienced a remarkable increase in quality of life; 2 years after surgery, she died from respiratory failure. The male patient has now survived for 4 years, and lung transplantation still remains a therapeutic option for him. We believe that pneumonectomy is a valuable rescue therapy for patients with cystic fibrosis and intractable unilateral lung infections who are at high risk of dying while waiting for lung transplantation.

Adolescent↗
PubMed1999

The clinical applications of functional MR imaging.

Functional MR imaging, similar to positron-emission tomography, shows the regions in which cerebral blood flow changes as neurons are active in the performance of cognitive tasks. Blood flow increases (activation) exceed that needed to supply oxygen for the increased metabolic needs for the increased neuronal activity. Therefore, in regions with activation, the deoxyhemoglobin concentration in the capillary blood decreases below levels found in the brain where neurons are not active.

Auditory Cortex↗
PubMed1998

Basic concepts of functional arteriovenous MR imaging malformations.

This article reviews the technical features of functional MR imaging. Examples are presented demonstrating how MR imaging may be used to identify primary cortical regions adjacent to AVMs. Preliminary results suggest that cortical functions may undergo translocation when the AVM involves eloquent cortex. This finding underscores the importance of cortical mapping prior to surgical excision.

Brain Mapping↗
PubMed1998

Basic concepts of functional magnetic resonance imaging and arteriovenous malformations

Cortical mapping is an important adjunct to the workup of patients with arteriovenous malformation (AVMs) near eloquent cortical regions. Task activation imaging can be performed that clearly identifies primary cortical regions. Although current methods require considerable postprocessing, advances in hardware and software will likely make functional MR imaging a routing examination before surgical resection of AVMs in the near future.

Journal Article↗
PubMed1997

Bifurcated stent-graft for abdominal aortic aneurysm.

The purpose of this study was to examine bifurcated stent-graft implantation for abdominal aortic aneurysm. Fifty-seven patients were treated and followed with serial computed tomography scans for up to 3 years. Patients were allocated to three groups (first 20, second 20, last 17) according to when the repair was performed. Successful treatment is defined as exclusion of the aneurysm from the circulation, based on contrast computed tomography. Success rates in the three groups were 55%, 70% and 100%. Perigraft leak (endoleak) was present on initial assessment in 4/20, 2/20 and 1/17. Two of these aneurysms ruptured early in the postoperative period. Thereafter, leaks were sought and treated aggressively. Kinking and thrombosis occurred in six of the first 20 patients, but did not occur in any of the last 37 patients, in whom the graft limbs were routinely stent-supported throughout. Infrarenal implantation in very a short neck (< 10 mm), or a thrombus-lined neck was associated with proximal stent migration. In conclusion, changes in patient selection and technique have led to a steady rise in the short-term success rate of the stent-grafted implantation.

Aneurysm, Ruptured↗
PubMed1997

Direct invasion of the renal vein by metastatic testicular cancer.

We report a case of metastatic seminoma with direct invasion of the left renal vein. A tumor thrombus was found in the renal vein while the vena cava thrombosis proved to be a noncancerous blood clot developing as an extension of the tumor thrombus. Primary chemotherapy could not be completed because of thrombotic growth requiring surgical intervention. Although surgical specimens were free of viable tumor and two cycles of adjuvant chemotherapy were applied, the tumor relapsed in the area of renal vein invasion.

Adult↗
PubMed1997

European experience with a system for bifurcated stent-graft insertion.

PURPOSE: To test an endovascular aneurysm exclusion system in the presence of a wide range of challenging anatomic features. METHODS: Bifurcated endovascular stent-grafts were inserted in 52 patients and followed with serial computed tomography for up to 3 years. The device underwent several modifications during this time, the most significant of which represent the difference between the homemade (n = 42) and industry-made (n = 10) versions. RESULTS: The initial procedural success rate was 92% in the homemade group and 100% in the industry-made group. In the 3 years of follow-up, the long-term success rate was 64% in the homemade group and 90% in the industry-made group. The primary reasons for failure in the homemade group were graft thrombosis due to kinking early in the series and proximal stent migration later in our experience. All cases of migration occurred when the neck was < 15 mm in length, the neck was lined with thrombus, or the stent was implanted > 15 mm from the renal arteries. Kinking was subsequently overcome by implanting Wallstents throughout the graft limbs. The sole failure in the industry-made group was a case in which collateral perfusion reached the aneurysm through patent lumbar arteries. CONCLUSIONS: The fruits of this experience are a better technique, a better device, and, most importantly, a better understanding of the system's limits, as reflected in the current selection criteria.

Angiography↗
PubMed1997

[Ambulatory sports in asthma improves physical fitness and reduces asthma-induced hospital stay].

Physical training is a well established method in the rehabilitation of patients with chronic obstructive pulmonary disease. In adult asthmatics its efficacy has been shown by intensive training programmes lasting for 2-12 weeks. No data exist on the effect of long-term physical training once a week. 31 patients (f = 24, m = 7; mean age 55 +/- 2 years; mean FEV1.0 82 +/- 4% pred.) participated in a physical training programme for at least 2 years. (8 patients had mild, 12 moderate and 11 severe asthma according to the International Consensus Report of 1993 [13]). Training time was 1 hour per week. The physical training programme consisted of breathing techniques like pursed-lip breathing and diaphragmatic exercise, progressive muscle relaxation, circuits and endurance training. According to the health insurance records 9 patients had been hospitalised for their disease two years prior to the study for a total number of 218 in-hospital days. During the 2 years of the study 2 patients had been hospitalised for a total number of 29 days (p < 0.001). A comparison group of 10 patients who did not participate in the rehabilitation programme had been hospitalised for their disease two years prior to and during the study period for a total number of 236 and 201 in-hospital days (p > 0.2). In a subgroup of 9 patients bicycle exercise testing was performed once a month and work load at a submaximal heart-rate (200-age) was recorded. During the two years mean work rate improved from 48 watts to 83 watts for 15 minutes (p < 0.01). We conclude from our findings that long-term physical training of adult patients with asthma in an outpatient setting once a week is effective in reducing hospitalisation days as well as in increasing cardiorespiratory fitness.

Adult↗
PubMed1996

Clinical experience with a bifurcated endovascular graft for abdominal aortic aneurysm repair.

PURPOSE: The purpose of this study was to test a transfemoral system of bifurcated endovascular graft insertion for aortic aneurysm repair. METHODS: Bifurcated endovascular grafts were inserted through bilateral femoral artery cutdowns in 41 patients. The results were assessed by completion angiography and follow-up computed tomography. RESULTS: The second half of the study included more aneurysms 6 cm or larger (p < 0.05) and more instances of short proximal neck (p < 0.05), proximal neck angulation (p < 0.05), and iliac angulation (p < 0.05). Despite the increasingly challenging anatomy, the results were better in the second half of the study as illustrated by the lower overall combined morbidity/mortality rate (15% vs 50%) and higher overall success rate (85% versus 65%). The mortality rate for the series as a whole was 7.5%. Mean follow-up was 18.8 months for the first 20 patients and 10.9 months for the second 20. The commonest complication in the first half of the study was graft thrombosis (n = 5). This complication was absent from the second half of the study because of routine adjunctive stenting. Two patients died of complications of endovascular repair. In both cases aneurysm rupture on the third postoperative day was associated with coagulopathy and angiographic signs of perigraft leak. CONCLUSION: Aneurysm exclusion with a bifurcated endovascular graft was feasible in a wide range of patients, but when the aneurysm was not entirely excluded from the circulation, the risk of rupture persisted.

Aorta, Abdominal↗
PubMed1996

[Secondary stabilization of aortic bifurcation Chuter endoprostheses by implantation of self-expanding metal stents].

The use of conventional graft fabric for the bifurcated Chuter endovascular graft may result in a kink instability since crimping has been removed. Especially in elongated arteries that are frequently found with aortic aneurysms this may cause stenosis of the kinked graft and subsequent thrombosis. Bilateral stabilisation of the graft limbs along its total length proved sufficient to stabilise the graft thus preventing secondary thrombosis.

Angiography, Digital Subtraction↗
PubMed1996

Aortic and iliac stenoses: follow-up results of stent placement after insufficient balloon angioplasty in 118 cases.

PURPOSE: To demonstrate follow-up results of stent placement in aortic and iliac stenoses. MATERIALS AND METHODS: A total of 109 patients with 118 aortoiliac stenoses underwent placement of self-expanding stents. Mean length of the stenotic segments was 3 cm +/- 2 (standard deviation). Mean ankle-arm index at rest was 0.58 +/- 0.2. A total of 101 patients were followed up angiographically or clinically. RESULTS: A mean of 1.2 stents +/- 0.5 were inserted per case. Clinical stage improved in 112 cases; it improved two or more stages in 89 cases. Mean ankle-arm index improved to 0.92 +/- 0.17. Total and major complication rates were 6.8% and 3.4%, respectively. Subacute occlusion occurred in four patients. Late stent obstruction occurred after a mean of 27 months (range, 16-48 months) in 10 cases. Primary patency was 95% after 1 year and 88% after 2 years; 4-year patency was 82%. Secondary patency was 96% after 1 year and 93% after 2 years. Three- and 4-year secondary patency were both 91%. CONCLUSION: Placement of self-expanding stents in iliac stenoses is technically safe and offers sufficient follow-up patency.

Angiography, Digital Subtraction↗