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R Bachmann

Publications and source records attributed to R Bachmann.

At least 37 records · Page 2Linked to original sources
PubMed2000

A new type of artificial urinary calculi: in vitro study by spiral CT.

RATIONALE AND OBJECTIVES: Artificial urinary calculi similar to natural stones have long been sought in urologic research. In an experimental study, the authors assessed the CT characteristics of a new type of artificially produced urinary calculus [BON(N)-STONE]. METHODS: Six different types of urinary calculi (uric acid, struvite, cystine, calcium oxalate, brushite, and apatite) were produced by a coating technique in which several layers of a suspension of pure substance were applied around a core and dried. A total of 60 stones (10 per group) were studied by spiral CT at two energy levels (100 and 120 kV, 250 mA) with 1-mm slice thickness. RESULTS: All calculi showed a small hyperdense core surrounded by a homogeneous matrix and a slightly hyperdense outer rim. From the least to the most dense, the stone types were uric acid, struvite, cystine, calcium oxalate, brushite, and apatite. Absolute CT values at 100 and 120 kV could differentiate between all groups of stones at a significance level of P < 0.001 or better. Attenuation values were in a comparable range to reported values for natural stones, with the exception of uric acid and struvite, which were notably lower. CONCLUSION: These artificially produced urinary calculi showed properties similar to those of natural stones. Thus, this seems to be a promising stone model for further investigations.

Humans↗
PubMed2000

Detection of thrombosis in the portal venous system: comparison of contrast-enhanced MR angiography with intraarterial digital subtraction angiography.

PURPOSE: To determine whether intraarterial digital subtraction angiography (DSA) can be replaced by contrast material-enhanced magnetic resonance (MR) angiography in the assessment of patency or thrombosis of the portal venous system in patients with portal hypertension. MATERIALS AND METHODS: Thirty-six patients with portal hypertension underwent contrast-enhanced MR angiography and intraarterial DSA for assessment of the portal venous system. The images were evaluated for vessel patency or thrombosis of the portal, splenic, or superior mesenteric vein. RESULTS: Of the 101 vessels evaluated, 42 were thrombosed. Overall sensitivity, specificity, and accuracy for the detection of thrombosis were 100%, 98%, and 99%, respectively, for MR angiography and 91%, 100%, and 96%, respectively, for DSA; differences between the imaging methods were not statistically significant. Only in four patients with six vessels (6%) were there discordant findings between MR angiography and DSA. CONCLUSION: Noninvasive contrast-enhanced MR angiography has the potential to replace intraarterial DSA as the standard method to assess the whole portal venous system.

Adolescent↗
PubMed1999

Severity of symptoms and demyelination in MOG-induced EAE depends on TNFR1.

The individual role of tumor necrosis factor receptor 1 (TNFR1) and TNFR2 signaling in experimental autoimmune encephalomeylitis (EAE) was investigated using mice lacking TNFR1 (TNFR1-/-), TNFR2 (TNFR2-/-) as well as double receptor (TNFR1/2-/-) and double ligand (TNF/LT alpha-/-) knockout mice. In wild-type (wt) mice immunized with myelin oligodendrocyte glycoprotein (MOG) peptide 35-55 the clinical course is characterized by an acute disease onset with peak disease scores and a consecutive chronic phase lasting up to 60 days. Compared to control mice, TNF/LT alpha-deficient mice showed a significant delay in disease onset and a remarkable reduction in demyelination which was, however, associated with increased inflammation. In TNFR1-/- and TNFR1/2-/- mice, the disease course was comparable to TNF/LT alpha-deficient mice but rather monophasic and less severe at late time points. Likewise only minimal spinal cord demyelination became apparent. In contrast, the course of EAE in TNFR2-/- mice was severe and associated with remarkable demyelination. Taken together these findings define TNFR1 as crucial mediator in MOG-induced EAE and suggest a protective role for TNFR2 signaling in the clinical course of EAE.

Animals↗
PubMed1999

Enhanced tumor detection in the presence of liver cirrhosis: experimental study on the diagnostic value of a superparamagnetic iron oxide MR imaging contrast agent (NSR 0430).

The purpose of this study was to determine the diagnostic value of the superparamagnetic iron oxide NSR 0430 for the detection of focal liver lesions in the presence of advanced cirrhosis. Cirrhosis and growth of cholangiofibromas were induced in 22 rats by administration of thioacetamide. Sixteen non-cirrhotic animals served as controls. T1 and T2 relaxation times of liver and tumor tissue of 12 animals were measured spectroscopically. In 10 animals in vivo MRI was performed before and 1 hour after contrast administration, and then the tumor-to-liver contrast-to-noise ratio (CNR) was calculated. All specimens were evaluated histologically. After contrast administration, T1 and T2 values of liver tissue showed a significant decrease of 18% (P = 0.01) and 31% (P = 0.009), respectively, whereas relaxation times of tumor tissue did not change. On precontrast turbo spin-echo images, 40 tumors could be identified; after contrast administration, 95 lesions were visible. CNR increased significantly after contrast administration by 297% at a TE of 50 msec and by 254% at a TE of 90 msec. In conclusion, our in vitro and in vivo results demonstrate that administration of NSR 0430 substantially improves liver-to-tumor CNR and lesion detection on T2-weighted magnetic resonance images even in the presence of severe cirrhosis.

Animals↗
PubMed1999

Impairment of TNF-receptor-1 signaling but not fas signaling diminishes T-cell apoptosis in myelin oligodendrocyte glycoprotein peptide-induced chronic demyelinating autoimmune encephalomyelitis in mice.

T-cell apoptosis in inflammatory demyelinating lesions of chronic myelin oligodendrocyte glycoprotein peptide35-55 induced autoimmune encephalomyelitis was studied in several different gene knockout mice as well as their wild-type counterparts. The gene deletions included tumor necrosis factor (TNF) alpha, lymphotoxin, TNF receptor 1 or 2, Fas-L, inducible nitric oxide synthase, perforin, and interleukin1beta-converting enzyme. Impairment of the TNF receptor 1 pathway led to a 50% reduction of T-cell apoptosis in the central nervous system lesions, whereas the other genetic deletions showed no significant effect. Our study thus identified the TNF receptor 1 signaling pathway as one mechanism responsible for the removal of T lymphocytes from inflammatory demyelinating lesions of the central nervous system.

Animals↗
PubMed1999

[The MRT of focal liver lesions: the value of gadolinium-enhanced dynamic studies of the whole organ with a fast 3D-turbo-gradient echo sequence].

PURPOSE: To determine the value of a dynamic Gd-enhanced ultrafast T1-weighted 3D-turbo-gradient-echo sequence (3D-TFE) in the detection and characterization of focal liver lesions. MATERIALS AND METHODS: 51 patients with 124 focal liver lesions (35 hemangiomas, 30 HCC, 24 metastases, 22 cysts, 5 FNH/adenoma, 8 other lesions) were examined using a 1.5 T system. The dynamic 3D-TFE sequence, achieving 40 slices with a thickness of 4.5 mm in a 17-s breath-hold, was compared with a fat-suppressed T2-weighted fast-spin-echo sequence (TSE SPIR), unenhanced and Gd-enhanced T1-weighted spin-echo sequences (SE), and a T1-weighted gradient-echo sequence (FFE). RESULTS: On 3D-TFE images more lesions (107/124) were identified than on T1-weighted SE (101/124) and T1-weighted FFE images (106/124), but less compared to T2-weighted TSE SPIR images (115/124). The 3D-TFE-sequence provided additional information in 65/107 (61%) detected lesions by delineating the dynamic enhancement pattern, most valuable in patients with HCCs in 90%. CONCLUSIONS: On dynamic 3D-TFE images more lesions could be depicted than on conventional T1-weighted SE and T1-weighted FFE images. Visualization of the dynamic enhancement pattern provided additional information for tumor characterization in 61% of the detected lesions on the 3D-TFE images.

Artifacts↗
PubMed1999

Evaluation of different models of experimentally induced liver cirrhosis for MRI research with correlation to histopathologic findings.

RATIONALE AND OBJECTIVES: Three models of experimentally induced liver cirrhosis were evaluated for MRI research on chronic liver disease. The influence of different histopathologic changes in liver fibrosis and cirrhosis on relaxation times and signal intensities was studied in vitro and in vivo. METHODS: Liver fibrosis and cirrhosis in rats was induced by oral or subcutaneous administration of carbon tetrachloride (CCl4) or by thioacetamide (TAA) in drinking water. On histology, the degree of liver fibrosis and cirrhosis, fatty infiltration, iron accumulation, and inflammatory changes were measured semiquantitatively. The amount of connective tissue was quantitatively determined by morphometry. The results were correlated with T1 and T2 relaxation times and signal intensities of the liver studied in vitro by relaxometry and in vivo by MRI. RESULTS: In both groups with CCl4 administration, histology revealed different degrees of liver fibrosis and cirrhosis. Subcutaneous injection of CCl4 also resulted in increased fatty infiltration. On the contrary, TAA produced complete liver cirrhosis in all animals. Overall, there was a good correlation between the liver T2 relaxation time and the amount of connective tissue in liver fibrosis and cirrhosis. However, the degree of liver fibrosis and cirrhosis was also strongly correlated with the degree of inflammatory changes. In the group with CCl4 administration, there was a good correlation between the fatty infiltration and the T1 relaxation time, as well as with the liver signal intensity on the T1-weighted gradient echo sequence. An increased iron accumulation was also correlated with the degree of liver fibrosis/cirrhosis; however, there was no significant influence of the iron on relaxation times or signal intensities. CONCLUSIONS: The TAA model is easier to perform and more reliable in liver cirrhosis induction than the CCl4 models. Although there is a positive correlation between the T2 relaxation times and the degree of liver fibrosis/cirrhosis, this probably results from the associated inflammatory changes and is not caused by the increased amount of connective tissue.

Animals↗
PubMed1999

[The pathological/MR tomographic correlation and differential diagnosis of malignant kidney tumors].

PURPOSE: Evaluation of malignancy criteria in MRT of kidney tumors in correlation with the histopathological findings. MATERIALS AND METHODS: 41 patients with suspected malignant kidney tumors were examined using a T1 SE sequence (TR/TE 300/10 ms) before and after i.v. administration of 0.1 mmol/kg Gd-DTPA and a T2 SE sequence (TR/TE 5500/150 ms). The results were correlated with the pathological findings. RESULTS: 38 malignant tumors were found: 29 renal cell carcinomas (RCC), 13 with solid growth, 11 with tubulopapillary growth, and three with mixed growth forms, one cystic RCC, and one chromophobic RCC, in addition, 6 urothelial carcinomas and three other malignomas. Typical MRT criteria for RCC were an inhomogeneity of the tumor with regions of slightly increased signal intensity on the T1-weighted image (59%) and regions with reduced signal intensity on the T2-weighted image (96%) as compared with renal parenchyma; these were due to histomorphological hemorrhage and hemosiderin deposits, respectively. A further criterion for RCC was a hypointense pseudocapsule in the T2 TSE sequence in 79% of the cases. CONCLUSIONS: The low-signal nature of RCC in the T2-weighted image correlates with hemorrhage and hemosiderin deposits. The detection of a pseudocapsule is useful in the differential diagnosis of solid tumors in the kidney.

Carcinoma, Renal Cell↗
PubMed1998

Diagnostic value of a superparamagnetic iron oxide in MR imaging of chronic liver disease in an animal model.

OBJECTIVE: The enhancement characteristics and the diagnostic value of a cell-specific superparamagnetic contrast agent (NSR 0430) in different degrees of liver fibrosis and cirrhosis were experimentally studied in an animal model. MATERIALS AND METHODS: Chronic liver damage was induced in rats either by oral administration of carbon tetrachloride (CCl4) for 15 weeks (n = 37) or by oral administration of thioacetamide (TAA) in drinking water for 24-26 weeks (n = 48). Twenty-six animals served as control subjects. T1 and T2 relaxation times for the liver and the spleen were measured in vitro with a spectrometer at 40 MHz. In vivo MR imaging at 1.5 T also was performed using T2-weighted turbo spin-echo sequences before and 1 hr after administration of NSR 0430. All data were correlated with the histologic degree of liver fibrosis and cirrhosis and the amount of connective tissue in the liver, which was measured morphometrically. RESULT: CCl4 produced liver fibrosis in most of the animals, and TAA predominantly caused liver cirrhosis. NSR 0430 caused a T2 relaxation time decrease in the control animals by 49%; in the CCl4 group with light and moderate liver fibrosis, by 25%; in the CCl4 group with severe liver fibrosis or cirrhosis, by 16%; and in the TAA group with cirrhosis, by 30%. On the T2-weighted turbo spin-echo sequences, liver signal-to-noise ratios (SNRs) decreased after contrast agent administration in the control animals by 81% and 79%, depending on the TE parameter. In the CCl4 group, liver SNRs decreased by 96% and 61% in animals with light or moderate fibrosis and by 44% and 55% in animals with severe fibrosis or cirrhosis, depending on the TE parameter. In the TAA group, liver SNR decreased by 61% and 67%, depending on the TE parameter. CONCLUSION: Enhancement of the superparamagnetic contrast agent NSR 0430 is decreased in the presence of liver fibrosis and cirrhosis in an animal model. However, the reduced enhancement is not directly related to the degree of chronic liver damage, which limits the diagnostic value of superparamagnetic contrast agents in the assessment of chronic liver disease.

Animals↗
PubMed1998

[Diagnosis and therapy of Budd-Chiari syndrome].

PURPOSE: Budd-Chiari syndrome is a fairly uncommon disease in Europe. This often leads to its late diagnosis. The syndrome is characterised by portal hypertension and splanchnic congestion due to obstruction of hepatic venous outflow. This paper describes the treatment of three patients with Budd-Chiari syndrome by interventional therapeutic techniques and discusses alternative treatment modalities. PATIENTS AND METHODS: The first patient presented with veno-occlusive disease and was treated by the placement of a transjugular intrahepatic portosystemic stent-shunt. The second patient showed an occlusion of the major hepatic veins. After percutaneous recanalisation, a stent was placed in the right hepatic vein which remained patient. The third patient had a membranous obstruction of the right hepatic vein which was treated by percutaneous balloon dilatation. RESULTS: In all patients the clinical symptoms resolved completely after treatment and no complications were encountered. CONCLUSIONS: The authors conclude that interventional therapeutic techniques offer a wide variety of possibilities for the treatment of patients with Budd-Chiari syndrome and are safe, effective and relatively inexpensive. However, further studies are required to assess the long-term results and survival rates of these patients.

Adult↗
PubMed1997

Dipyridamole scintigraphy and intravascular ultrasound after successful coronary intervention.

UNLABELLED: Despite angiographically successful interventions, perfusion defects are not uncommonly observed in postinterventional perfusion scintigrams. The aim of this study was to test the hypothesis that perfusion defects after coronary intervention are associated with a significant residual stenosis in the treated vessel segment detectable by intravascular ultrasound but not by angiography. METHODS: Forty consecutive patients with angiographically successful coronary interventions were prospectively studied by intravascular ultrasound immediately after the intervention. Within 48 hr after the intervention all patients had myocardial scintigraphy using 99mTc-methoxyisobutyl-isonitrile SPECT after dipyridamole stress. Myocardial perfusion defects in the scintigram were assigned to a segmental left ventricular model and compared to the perfusion territory of the treated vessel estimated from the coronary angiogram. RESULTS: Twenty of 40 patients had reversible myocardial perfusion defects. Mean ultrasound area stenosis was 50% in these patients and 33% in patients without perfusion defects (p < 0.002); ultrasound percent plaque area was 75% versus 63% (p < 0.0001), respectively. The best concordance between residual area stenosis and perfusion defects was found for an ultrasound area stenosis > or = 40%. CONCLUSION: Patients with stress-induced myocardial perfusion defects immediately after successful coronary intervention show high-grade residual stenoses that are more pronounced in patients with perfusion defects than in patients with normal postinterventional scintigrams. In addition, vessels serving myocardial regions with perfusion defects showed a significantly higher plaque burden indicating diffuse atherosclerotic changes in the vessel. The evaluation of the postprocedural result by intravascular ultrasound contributes to a better understanding of the discrepancy between the angiographic finding of a widely patent vessel but scintigraphic evidence of impaired perfusion.

Adult↗
PubMed1993

Pattern of recurrence in rectal carcinoma: implications for the design of (future) studies on adjuvant therapy.

255 patients who underwent potentially curative surgical treatment for rectal carcinoma at the Cantonal Hospital Aarau from 1981 to 1989 have been followed up and the results analysed for overall survival and the timing and occurrence of local and distant recurrence in relation to the initial tumor stage. The patients had received standard surgical treatment for rectal carcinoma with the exception of 28 patients who had been randomized to the treatment arm of SAKK protocol 40/81 and were given perioperative adjuvant portal chemotherapy. 10 patients with large fixed tumors had preoperative radiation therapy. In UICC stage I most patients were cured by surgery alone, local recurrence as rare, and distant metastases appear in about 10% of pT2. cases. In stage II about one fifth of the patients developed a recurrence with one third of them having only local recurrence, and two thirds having either combined local and distant recurrence or distant recurrence alone. The small subgroup of pT4 pN0 had a very poor prognosis with early occurrence of distant metastases. In stage III the actuarial five-year survival was 25%, 60% of stage III cases had pN1 nodal disease. No patient with pN2-3 disease was alive after five years follow-up. The overall risk of distant metastases in stage III was 64%. Local recurrence rate was highly dependent on the pT-stage.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗
PubMed1992

[Temporomandibular myoarthropathy syndrome--a frequent cause of facial pain].

The temporo-mandibular joint syndrome (syn.: myofascial pain syndrome) is a frequent cause of facial pain. Originally, occlusal disturbances were thought to be of primary etiopathogenetic importance. However, the significance of psychological factors has been recognized during the past few years. Therefore, the treatment of patients with myofascial pain syndrome not only concerns dentists, but also general practitioners. In this report, the clinical examination, differential diagnosis and the therapeutic concept are described in order to increase interdisciplinary understanding of the temporo-mandibular joint syndrome. Additionally, the authors present their own experiences using local anesthesia therapeutically in 34 patients with myofascial pain syndrome. The symptoms remained unchanged in eight patients (24%), clinical improvement was seen in 17 patients (50%) and nine patients (26%) were free of disease after treatment.

Adolescent↗
PubMed1992

Regurgitant flow in cardiac valve prostheses: diagnostic value of gradient echo nuclear magnetic resonance imaging in reference to transesophageal two-dimensional color Doppler echocardiography.

Gradient echo nuclear magnetic resonance (NMR) imaging and transesophageal two-dimensional color Doppler echocardiography are flow-sensitive techniques that have been used in the diagnosis and grading of valvular regurgitation. To define the diagnostic value of gradient echo NMR imaging in the detection of regurgitant flow in cardiac valve prostheses and the differentiation of physiologic leakage flow from pathologic transvalvular or paravalvular leakage flow, 47 patients with 55 valve prostheses were examined. Color Doppler transesophageal echocardiography was used for comparison. Surgical confirmation of findings was obtained in 11 patients with 13 valve prostheses. Gradient echo NMR imaging showed regurgitant flow in 37 of 43 valves with a jet seen on transesophageal echocardiography and it detected physiologic leakage flow in 4 additional valves. There was 96% agreement between the two methods in distinguishing between physiologic and pathologic leakage flow. The methods differed on jet origin of pathologic leakage flow in six prostheses. The degree of regurgitation was graded by both NMR imaging and transesophageal echocardiography, according to the area of the regurgitant jet visualized; gradings were identical for 75% of valve prostheses. Quantification of jet length and area showed a good correlation between the two methods (r = 0.85 and r = 0.91, respectively). Gradient echo NMR imaging is a useful noninvasive technique for the detection, localization and estimation of regurgitant flow in cardiac valve prostheses. However, because transesophageal echocardiography is less time-consuming and less expensive, gradient echo NMR imaging is unlikely to displace transesophageal echocardiography and should be used only in the occasional patient who cannot be adequately imaged by echocardiography.

Coronary Circulation↗
PubMed1992

[The pattern of recurrence of T3 rectum cancer].

Rectal carcinoma is one of the most common tumors of the GI-tract. At the time of initial treatment the majority of our patients had a stage T3 tumor. In order to contribute to the development of new guidelines for adjuvant therapies we analysed the patterns of recurrence in the patients operated with curative intention in our institution between 1981 and 1989. The pattern of recurrence shows that every fifth patient could benefit of a local measure to reduce local recurrence and that every second patient with positive nodal histopathology could benefit of a systemic adjuvant chemotherapy.

Adenocarcinoma↗
PubMed1991

[Magnetic resonance tomography in patients with a heart valve prosthesis].

Artificial valve prostheses are often regarded as a contraindication for magnetic resonance imaging (MRI), although preliminary in vitro studies suggested, that patients with these metallic implants might safely undergo MR examination. This study reports on the experience with a group of 89 patients with 100 heart valve prostheses who were examined by spin-echo MR and gradient-echo MR. MR examination was performed in all patients without complications. The spin-echo sequence showed advantages in the depiction of anatomical structures like paravalvular abscesses. Anatomical structures adjacent to the artificial valve were clearly visible and the metal components of the valves showed no or only small artifacts. Artifacts were accentuated when using gradient-echo sequences. Gradient-echo sequences provided valuable information regarding the presence of valvular insufficiency. Physiological valvular regurgitation was easy to differentiate from pathological paravalvular or transvalvular regurgitation. These results demonstrate that patients with artificial valve prostheses can be imaged by MR without risk and that prosthesis-induced artifacts do no interfere with image interpretation.

Abscess↗
PubMed1991

Custom-made resin-bonded attachments supporting a removable partial denture using the spark erosion technique: a case report.

A removable partial denture supported by resin-bonded precision attachments was constructed for a patient with intraoral symptoms of a cleidocranial dysostosis. Because of the anatomic situation, the youth, and the preprosthetic orthodontic treatment of the patient, a conventional prosthetic solution seemed inappropriate. Custom-made attachments were constructed with the spark erosion technique. They were fixed to the abutment teeth with resin-bonded retainers. The combination of the resin-bonding technique with the modern technology of spark erosion thus allowed a conservative approach to the oral rehabilitation of a young patient.

Adolescent↗