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Biomedical subjects

M Langer

Publications and source records attributed to M Langer.

At least 217 records · Page 12Linked to original sources
PubMed1994

[A comparison of positive and negative enteral contrast media for the magnetic resonance tomography of the abdomen].

Following oral administration of a buffered gadopentetate-dimeglumine solution (Magnevist enteral, 1 mmol/l, 6-17 ml/kg) T1-, proton-density- and T2-weighted spin-echo images of abdominal and retroperitoneal lesions were acquired (0.5 T). Gadopentetate is a signal-enhancing, positive MR contrast agent, intraluminal air served as a model of a signal-free, negative agent. In 21 patients contrast/noise ratios of gadopentetate and air versus lesions and fat were compared quantitatively (t-test). In T1- and T2-weighted images contrast/noise ratios of gadopentetate versus lesions were significantly higher than those of air. In proton-density images there was no significant difference. In T1- and proton-density images contrast/noise ratios of air versus abdominal fat were significantly higher than those of gadopentetate, in T2-weighted images gadopentetate had a significantly higher contrast/noise ratio than air. Signal-enhancing positive contrast agents seem advantageous over signal-free negative enteral MR contrast agents.

Abdomen↗
PubMed1994

[Radiologic differential diagnosis of inflammatory round pulmonary infiltrates in immunocompromised patients. A prospective study using CT and MRT].

In a prospective study we examined the diagnostic ranking of CT and MR in 52 immunocompromised patients with nodular pulmonary lesions and clinical suspicion of invasive pulmonary aspergillosis (IPA). For early diagnosis of IPA (clinical symptoms having existed for less than 10 days) the CT halo sign proved highly sensitive and specific. MRT showed at this time a comparatively high sensitivity but only low specificity that could not be improved upon after Gd-DTPA. At a later stage of the aspergillosis infection (clinical symptoms manifested for more than 10 days) MR identified aspergillus-specific lesions with on-target characteristics (marked enhancement of margins after Gd-DTPA) or the so-called "reverse" target phenomenon (T2-weighted sequences). Such lesions were never seen in the early stage of the disease in patients with nodular pulmonary lesions of different aetiology (pseudomonal or staphylococcal pneumonia).

Adult↗
PubMed1994

Invasive pulmonary aspergillosis. MRI, CT, and plain radiographic findings and their contribution for early diagnosis.

A prospective study was conducted in 38 patients with nodular lesions on plain chest radiographs and the clinical suspicion of invasive pulmonary aspergillosis (IPA) to assess the diagnostic accuracy of magnetic resonance imaging (MRI) and computed tomography (CT). For early diagnosis of IPA (clinical signs and symptoms < 10 days), CT scans with demonstration of the halo sign had a high sensitivity (16/22) and specificity (8/8). Magnetic resonance imaging performed at the same time revealed a relatively higher sensitivity (22/22), but a very poor specificity (0/8). Gadolinium-diethylene-triamine-pentaacetic acid (Gd-DTPA) enhanced images did not improve specificity. In the later course of infection (clinical signs and symptoms > 10 days), MRIs showed typical nodular target-like lesions with Gd-DTPA enhancement of the rim area that was not seen in the early course of the disease or in patients with Pseudomonas or staphylococcal infection. In conclusion, MRI findings are not as characteristic as the CT halo sign in diagnosing IPA in the early course of the disease, but the MRI target sign with Gd-DTPA enhancement of the rim area and the "reverse target" on T2-weighted images are strongly suggestive of IPA at a later stage of the disease.

Aspergillosis↗
PubMed1994

[Optimizing intravenous bolus contrast medium injection in cervical CT diagnosis].

PURPOSE: A prospective, comparative study of 60 patients for optimizing contrast medium (CM) administration for spiral CT of the neck. METHODS: Prior to the investigation, the patients were randomly assigned to three groups (n = 20 each): a) conventional CT technique, interscan duration 10 s, CM volume 150 ml of Ultravist 300 (30 ml at a flow rate of 1.5 ml/s, the remaining 120 ml as maintenance dosage of 0.5 ml/s); b) so-called dynamic CT technique, interscan duration 5 s, CM volume 100 ml (200 ml at a flow rate of 2 ml/s and 80 ml with a flow rate of 0.5 ml/s); c) spiral CT technique, total investigation time to store the crude data was 30 s, a CM dosage of 50 ml at a flow rate of 2 ml/s (30 ml) in the first phase and 0.7 ml/s (20 ml) in the second phase was studied. RESULTS: The current evaluation of the CM time-density course, image quality, diagnostic efficiency, and investigation time showed that a good to very good contrast medium enhancement of the neck vessels was achieved in all groups so that pathological findings were well differentiated. CONCLUSIONS: The CM volume could be reduced to a third of the original used amount without loss of diagnostic security by use of the spiral CT technique.

Adolescent↗
PubMed1994

[Hemodynamics, liver function and clinical follow-up after TIPS].

In 126 patients with liver cirrhosis treated electively with transjugular intrahepatic portosystemic stent shunt (TIPS) to prevent variceal rebleeding, the portosystemic pressure gradient decreased by 60%. In spite of this incomplete effect the risk for variceal rebleeding was still under 20% after 2 years. Only 1 patient died of variceal rebleeding. Shunt insufficiency occurred in 50%, mainly during the first year, but shunt function was restored in nearly all cases by radiologic intervention, i.e., redilatation or implantation of an additional stent. During the follow-up of 16 +/- 9 months, 21 patients (17%) died, one-third of them from progressive liver failure aggravated in 4 cases by severe drinking. De novo hepatic encephalopathy was observed in 10%, especially in older patients and patients with impaired liver function before TIPS. In such patients it is recommended that the shunt be dilated to 0.8 cm at most, and the TIPS procedure can be combined with transjugular embolization of the varices. The advantages of TIPS over both endoscopic sclerotherapy and drug treatment must be clarified in randomized studies, which have already been initiated in several centers.

Catheterization↗
PubMed1994

[Early changes in the hip joint following epiphysiolysis of the femoral head. Results of an MRT study].

With the aim of detecting patients at risk of developing coxarthritis, 34 patients were investigated prospectively by MRI 6-14 years after epiphysiolysis for slipped capital femoral head. In particular, cartilage changes were analysed by gradient-echo sequences. In 40% of the hip joints investigated cartilaginous lesions were present, detectable as irregularity and flattening of contour and more rarely as changes in signal intensity. In contrast, only 18% of the radiographs available revealed any pathology. When pelvic X-rays are normal or reveal slight sclerosis, cartilaginous lesions on MRI are considered early signs of coxarthrosis. This combination was seen especially often in patients with a primarily high angle of dislocation and in those who needed treatment by reposition or osteotomy. Only in 8 of the 17 hip joints showing sclerosis on conventional radiograms, sclerosis was also diagnosed by MRI, possibly because of partial volume and susceptibility effects at high field strength. Even with limited spatial resolution, cartilage examination is warranted in young patients in whom early osteoarthritis can be expected.

Adult↗
PubMed1994

[Quality criteria of digital subtraction angiography of the trunk of the body].

The presently valid quality criteria of digital subtraction angiography in the body trunk area are described. The indications for intravenous and intraarterial examinations are explained; these are closely connected with the respective demands. The problem levels are analysed and update technical and methodical solutions are offered.

Angiography, Digital Subtraction↗
PubMed1994

[3-D CT for the demonstration of findings in compound skull injuries].

Conventional radiographs, axial CT with multiplanar 2-D and 3-D-CT reformations were obtained in 20 patients presenting with craniofacial injuries, to evaluate the capabilities of 3-D-CT. The image quality was assessed by two readers. Sagittal and oblique components as well as comminuted fractures could be detected by 3-D-CT reconstructions similarly to axial CT with 2-D reformations. Displacements over 2 mm were confidently documented by 3-D-CT images. 3-D-CT reconstructions allow an improved demonstration of rotational components of fractured fragments. 3-D-CT images are not as accurate as 2-D-CT in the primary detection of fractures in the relevant anatomic regions. Among 3-D-CT reconstructions, the lateral and partly the facial regions are adequately visualised.

Adolescent↗
PubMed1993

The reliability of optimization under dose-volume limits.

PURPOSE: An optimization algorithm improves the distribution of dose among discrete points in tissues, but tolerance depends on the distribution of dose across a continuous volume. This report asks whether an exact algorithm can be completed when enough points are taken to accurately model a dose-volume constraint. METHODS AND MATERIALS: Trials were performed using a 3-dimensional model of conformal therapy of lung cancer. Trials were repeated with different limits placed on the fraction of lung which could receive > 20 Gy. Bounds were placed on cord dose and target dose inhomogeneity. A mixed integer algorithm was used to find a feasible set of beam weights which would maximize tumor dose. Tests of feasibility and optimality are introduced to check the solution accuracy. RESULTS: Solutions were optimal for points used to model tissues. An accuracy of 3-4% in a volume condition could be obtained with models of 450-600 points. The error improved to 2% with 800 points to model the lung. Solution times increased six-fold at this level of accuracy. CONCLUSION: The mixed integer method can find optimum weights which respect dose-volume conditions in usually acceptable times. If constraints are violated by an excessive amount, the optimization model should be rerun with more points.

Algorithms↗
PubMed1993

Incidence and risk factors of pneumonia acquired in intensive care units. Results from a multicenter prospective study on 996 patients. European Cooperative Group on Nosocomial Pneumonia.

OBJECTIVE: To estimate the incidence of pneumonia acquired in the intensive care unit (ICU), and to define risk factors for developing such an event. DESIGN: European prospective survey, in which all patients admitted to the participating ICU from January, 17 to 23, 1990, were followed until ICU discharge. SETTING: 107 general ICUs from 18 countries. PATIENTS: Of 1078 admitted to the ICUs, 996 patients without pneumonia at admission were studied. MEASUREMENTS: Pneumonia was diagnosed by the staff physician on the basis of clinical, radiological and microbiological criteria, secondly validated by an expert committee who reviewed all the forms and even recontacted ICU physicians. Crude incidence and time to occurrence of pneumonia were estimated, then both used as end-points for prognosis analysis. RESULTS: 89 pneumoniae were observed: crude incidence was estimated at 8.9% 7-day and 14-day pneumonia rates at 15.8% and 23.4%, respectively. The risk of developing pneumonia increased when either coma, trauma, respiratory support, Apache II > 16 and/or imparied air-way reflexes were present at ICU admission. To predict time to occurrence of pneumonia, only two variables remained significant: the presence of impaired airway reflexes at admission and the use of mechanical ventilation during ICU course. CONCLUSIONS: The role of the injury to the respiratory system-with the subsequent need for respiratory support--appears central in determining the risk to acquire pneumonia in ICU. In the future, the predictive value of severity scores during ICU course should be otherwise assessed.

Adult↗
PubMed1993

Extracorporeal lipid elimination for treatment of gestational hyperlipidemic pancreatitis.

Gestational hyperlipidemia complicated by pancreatitis during the 24th week of gestation has been successfully managed by long-term extracorporeal elimination of triglyceride-rich lipoproteins. Three modes of treatment (plasma exchange, immunospecific apheresis, and a combination of both treatments) were compared for efficacy as therapy for metabolic derangements, altered blood rheology, and the loss of immunoglobulins. Treatments were performed by means of a peripheral venovenous approach. A combination plasma exchange/apheresis technique was highly effective; the loss of immunoglobulins remained acceptable. Clinical symptoms of pancreatitis subsided within 24 hours of the first treatment. A relapse during the 32nd week of gestation necessitated treatments more frequently than once a week. At the 36th week of gestation, after confirming lung maturity as indicated by a lecithin-sphingomyelin ratio of > 2.0, a cesarean section was performed. A healthy boy was delivered (2470 g; Apgar score, 9/10). This is the first report to show that long-term extracorporeal elimination of lipoproteins is a highly effective treatment of hyperlipidemic gestational pancreatitis.

Adult↗
PubMed1993

[CT contrast administration of iodine, gadolinium and ytterbium. In-vitro studies and animal experiments].

The absorption of the elements iodine, gadolinium and ytterbium in various dilutions was studied in relation to CT. Regression analysis and specific CT density measurements showed that absorption decreases from gadolinium to ytterbium and iodine. These results were confirmed by experiments using ten dogs. Boli of 0.5 molar gadolinium used for angio-CT without table movement showed the largest increase in density in the aorta and liver with an average of 190HU and 21HU respectively compared with iodine which gave 157HU and 12HU respectively. The animal experimental studies suggest that gadolinium and ytterbium are suitable contrast media for dynamic CT investigations.

Absorption↗
PubMed1993

Percutaneous recanalization of iliac artery occlusions: results of a prospective study.

PURPOSE: To evaluate the long-term results of recanalization of occluded iliac arteries with local low-dose thrombolysis, angioplasty, and, if necessary, stent implantation. MATERIALS AND METHODS: Forty-seven patients with acute or chronic occlusions of the common or external iliac artery, or both, underwent local low-dose thrombolysis (n = 47), percutaneous transluminal angioplasty (PTA) (with balloon dilation [n = 43] and rotational angioplasty [n = 30] in the patients in whom a retrograde recanalization was performed), and, if needed, intravascular stent placement (n = 18). Follow-up lasted 3-53 (mean, 21) months. RESULTS: The primary recanalization rate was 98% (46 of 47). The mean ankle-brachial index increased from 0.33 to 0.81 within 14 days after treatment and was 0.76 at the most recent follow-up. Two early (< 14 days) and two late reocclusions (after 24 and 30 months) occurred; one restenosis detected with duplex sonography and angiography was observed after 19 months. CONCLUSION: This therapy represents a true alternative to vascular surgery and a first-line treatment for acute or chronically occluded iliac arteries.

Adult↗
PubMed1993

Effect of local low-dose thrombolysis on clinical outcome in acute embolic renal artery occlusion.

PURPOSE: To determine the utility of local thrombolysis in treatment of acute embolic renal artery occlusion. MATERIALS AND METHODS: Fourteen patients with acute embolic renal artery occlusion treated with local low-dose thrombolysis were studied. Diagnosis was made with renal scintigraphy and selective renal arteriography. RESULTS: Thrombolysis was successful in 13 of 14 patients. During 1-72 months of follow-up (mean, 27.1 months), renal function did not improve on the side of complete renal artery occlusion, whereas stabilization of renal function at the pretherapy level was seen in patients with incomplete obstruction of the renal artery or complete obstruction at the level of segmental branches. In none of the patients did renal function return to normal. CONCLUSION: In acute embolic renal artery occlusion, thrombolytic therapy does not restore renal function and is therefore not indicated once the ischemic tolerance of the kidney (approximately 90 minutes) has been exceeded.

Acute Kidney Injury↗