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Biomedical subjects

B Wallner

Publications and source records attributed to B Wallner.

At least 55 records · Page 3Linked to original sources
PubMed1991

MR imaging of liver metastases at 1.5 T: similar contrast discrimination with T1- and T2-weighted pulse sequences.

The authors evaluated soft-tissue contrast on spin-echo (SE) proton density-weighted, SE T2-weighted, SE short-echo-time (TE) T1-weighted, and gradient-echo (GRE) images of 34 patients with known hepatic tumors who underwent high-field-strength (1.5-T) magnetic resonance imaging. For solid liver tumors, the difference in the mean lesion-liver contrast-to-noise ratios (C/Ns) with T1- (GRE and SE) and T2-weighted pulse sequences was not statistically significant (P greater than .05). For nonsolid liver tumors, the T2-weighted images provided significantly greater (P less than .05) mean lesion-liver C/N than T1-weighted GRE images. Mean liver signal-to-noise ratio was significantly greater on T1-weighted GRE (P less than .0001) and T1-weighted SE (P less than .05) images than on T2- and proton density-weighted images. Qualitative analysis of T1-weighted (SE and GRE) images and proton density- plus T2-weighted images showed that lesion conspicuity was similar in 25 of 32 patients (78%). The results suggest that liver tumor imaging at high field strength can be performed with short-TE T1-weighted (SE or GRE) or conventional T2-weighted pulse sequences.

Humans↗
PubMed1991

[Imaging of thoracic and abdominal aortic aneurysms using MR angiography].

Five patients with suspected dissecting aneurysm of the thoracic aorta and nine patients with fusiform aneurysm of the abdominal aorta underwent time-of-flight (TOF) MR angiography. MR angiography revealed dissecting aneurysms in four patients and a dilated ascending aorta without evidence of dissection in one patient. These findings correlated well with angiography, computed tomography and surgical findings. Proximal and distal extension as well as the relationship to vessels originating from the aortic arch was assessed correctly in all cases. There was a good correlation between MR angiography, CT, and angiography in the patients with abdominal aortic aneurysms. The status of the renal arteries was shown in all patients with MR angiography, but the inferior mesenteric artery was not regularly demonstrated. MR angiography is a promising method for non-invasive assessment of thoracic and abdominal aortic aneurysms.

Aortic Dissection↗
PubMed1990

Extracranial carotid arteries: evaluation with "black blood" MR angiography.

The authors evaluated the accuracy of "black blood" magnetic resonance (MR) angiography for depicting disease involving the extracranial carotid arteries. Two- and three-dimensional flow-compensated gradient-echo sequences were employed to create "bright blood" images. A thin-section spin-echo sequence with flow presaturation allowed the creation of black blood images. Projection angiograms were made from bright and black blood images with application of a maximum- or minimum-intensity projection algorithm, respectively. These methods were used in 13 healthy volunteers and 17 patients, and a prospective blinded comparison of MR angiography and conventional angiography was performed. Normal carotid arteries were well shown with both bright and black blood methods; in patients, both methods were sensitive for detecting carotid disease. However, bright blood angiography exaggerated the severity of carotid lesions in 13 of 33 arteries, mostly in severe disease; this problem was not encountered with black blood angiography. The authors conclude that bright blood angiography is a sensitive method for screening carotid disease; when a significant abnormality is found, black blood angiography should be performed for more precise delineation of the lesion.

Adult↗
PubMed1990

Segmented turboFLASH: method for breath-hold MR imaging of the liver with flexible contrast.

A method called segmented turboFLASH imaging allows high-resolution, multisection, short-inversion-time (TI) inversion-recovery (STIR), T1- or T2-weighted magnetic resonance (MR) studies of the liver to be completed within a breath-hold interval. The method was applied in a phantom and in 19 patients with hepatic lesions. Sequence comparisons were performed among segmented turboFLASH, single-shot turboFLASH, T1-weighted gradient-echo with ultrashort echo time, and T2-weighted spin-echo (SE) techniques. Signal from fat and liver could be nulled with the segmented turboFLASH method, with TIs of 10 and 300 msec, respectively; signal from these tissues could not be eliminated with the single-shot approach. Signal-difference-to-noise ratios and contrast for the best segmented sequences were comparable with those of the best T2-weighted SE and T1-weighted gradient-echo techniques. It is concluded that it is feasible to obtain breath-hold images with arbitrary tissue contrast by means of segmented turboFLASH imaging. The method may prove helpful for the detection and characterization of hepatic lesions and will likely have applications to other anatomic regions such as the chest and pelvis.

Adenoma, Bile Duct↗
PubMed1990

Bright pleural effusion and ascites on gradient-echo MR images: a potential source of confusion in vascular MR studies.

Motion of fluids other than blood can cause flow-related signal enhancement on MR images, including MR angiograms. In order to study this problem, the appearance of ascites (20 patients) and pleural effusions (five patients) was assessed on MR images made during suspended respiration with flow-compensated gradient-echo sequences as well as T1- and T2-weighted sequences. Signal intensities of vessels, fluid collections, and muscle were measured and vessel/muscle and vessel/fluid contrast were calculated. Fluid motion was measured with a bolus tracking technique that tags a selected volume of fluid with an RF presaturation. Fluid collections had a bright signal in four of five patients with pleural effusion and in 15 of 20 patients with ascites. The average contrast ratio between bright components of the fluid collections and vessels was only 0.03 +/- 0.09. Bright fluid collections were seen on MR angiograms and could obscure blood vessels. Bolus tracking measurements of ascites revealed multidirectional flow, suggesting that its bright signal is related to motion that continues during suspended respiration. Fluid collections appeared dark on T1-weighted images in all patients, indicating that a short T1 relaxation time was not a cause of the high signal intensity. The results indicate that, despite breath-holding, ascites and pleural effusions can show bright signal intensity on gradient-echo images. Awareness of this phenomenon will avoid confusion between moving fluid collections and flowing blood and identify a source of image degradation on both gradient-echo and T2-weighted spin-echo MR acquisitions.

Ascites↗
PubMed1990

[Colorectal invagination in adults following removal of a sigmoid polyp].

A unusual case of colorectal intussusception after transanal surgery of a polyp of the sigmoid colon is presented. Clinical Signs consisted of transanal bleeding and mucous diarrhoe. The diagnosis was established after an enema with water-soluble contrast media and computed tomography of the pelvis. The radiological appearance was similar to that of intussusception at other sites of the large bowel: The enema showed a sharply outlined filling defect whereas CT demonstrated a target-like intraluminal mass.

Colonic Diseases↗
PubMed1990

[The role of bedside thoracic imaging in monitoring surgical intensive care patients].

In this study the value of ward chest radiographs in differential diagnosis and follow-up of pulmonary disturbances was investigated in 105 patients of a surgical intensive-care unit. The course in time of roentgenologically visible infiltrates was a valid criteria in differential diagnosis, whereas appearance and localisation seemed to be of poor value. In follow-up studies we found a correlation between roentgenological and functional changes in 50% of the patients. In addition, we found a delayed change in chest radiographs in 23% of the cases with a worsening of the pulmonary function; in the remaining radiographs we found other explanations. In case of improvement, discrepancies were seen in 21% of the radiographs.

Contusions↗
PubMed1990

[Differential diagnosis and follow-up of pulmonary disorders by bedside thoracic imaging of intensive care patients].

In this study chest radiographs of 105 patients from an intensive care unit are reviewed to investigate the value in differential diagnosis and control of the course of pulmonary dysfunction. The most helpful criterion in differential diagnosis was the time course of the visible infiltrate on the chest film. Contusion of the lung and aspiration pneumonia showed a steady decrease after an initial maximum, pneumonia and ARDS developed within several days to a maximal infiltration. A rise in extravascular lung water presents with various quickly changing patterns. Pleural effusion, appearance and localisation of the infiltrate are of less value in differential diagnosis. The connection to clinical and anamnestic features is important. There was a good correlation between time course of the radiological visible infiltrate and the intensity of artificial respiration.

Contusions↗
PubMed1989

[Duplex sonography in postoperative monitoring of pancreatic transplants--initial experiences].

Duplex ultrasound has gained importance in postoperative monitoring of renal transplants; however, there is no published data on its value in pancreatic transplants. The present study reports on simultaneous pancreatic and renal transplantation of two patients submitted to Duplex scan and conventional ultrasound. During intervals without clinical evidence of complications continuous systolic/diastolic flow was observed. In one case of acute pancreatic rejection Duplex sonography delineated significant reduction of diastolic flow paralleling morphological changes in US. Therefore, relevance of clinical exploration and diagnostic US may be increased by supplementary use of duplex ultrasound.

Blood Flow Velocity↗
PubMed1989

[Venous occlusions distant to the shunt as malfunction factors during hemodialysis].

On 78 patients with dysfunction of haemodialysis vascular access (predominantly poor flow) systematic radiographic evaluation was performed. In all cases arteriography was carried out, followed by venous angiography in patients exhibiting occlusion of the arteriovenous fistula or the graft, respectively. In 11 cases (14%) occlusion or significant stenosis of far proximal venous vessels (axillary and/or subclavian vein) could be detected. It is suggested that consecutive deterioration of central venous runoff may induce or aggravate malfunctioning of the shunt and, moreover, may contribute to recurrent thrombosis of arteriovenous fistulae or grafts.

Arm↗
PubMed1989

[MRT and CT of diaphragmatic lipomas].

The radiological appearance of 6 posterior epidiaphragmatic fatty tissue masses in MRI and CT is reported. The differential diagnostic considerations of lipoma, herniation or dystopia and the value of imaging techniques are discussed.

Aged↗
PubMed1989

[Intra-arterial DSA of the hand arteries in the diagnosis of inflammatory connective tissue diseases].

Seventy-five patients with suspected rheumatic diseases underwent intraarterial DSA of the hand arteries. In 81% of the patients we were able to establish the diagnosis of vasculitis according to angiographic criteria. Neither clinical nor chemical or immunological features allowed the diagnosis of an inflammatory disease of joint and perivascular tissue at this time. However, histological examination and immunofluorescence microscopy confirmed the angiographic findings and showed signs of an immune complex vasculitis. A strong predictor for an abnormal angiogram of the hand arteries is the presence of Sicca's and Raynaud's Syndrome in addition to rheumatoid joint pain.

Adult↗
PubMed1989

Arterial perfusion abnormalities of the liver after hepatic arterial infusion chemotherapy and their correlation with changes in the metastases: evaluation with CT and angiography.

We studied the progress of hepatic arterial perfusion abnormalities in 50 patients receiving long-term arterial infusion chemotherapy for palliative treatment of liver metastases from colorectal cancers and correlated the findings with changes in the metastases. Intraarterially and IV enhanced CT scans and digital subtraction angiograms of the liver were made in all patients before chemotherapy and at 3-month intervals during chemotherapy for 1 year. Before the chemotherapy, all patients had normal hepatic arterial perfusion. Arterial perfusion abnormalities were detected in 30 patients (60%) after 6 months of chemotherapy and in 41 patients (82%) after chemotherapy for 1 year. After 6 months of chemotherapy, 36% of the regressive and 39% of the progressive metastases were located in areas with arterial perfusion abnormalities. After 1 year of chemotherapy, 54% of the regressive and 60% of the progressive metastases were situated in portions of the liver with perfusion abnormalities. Hepatic arterial perfusion abnormalities were found to be progressive during intraarterial infusion chemotherapy. No relationship between arterial perfusion abnormalities and tumor response to chemotherapy could be detected.

Antineoplastic Agents↗