Search PubMed⌕ Search

Biomedical subjects

K Lackner

Publications and source records attributed to K Lackner.

At least 55 records · Page 3Linked to original sources
PubMed1997

[Localization of puncture needles in MRI: experimental studies on precision using spin-echo sequences at 1.0 T].

PURPOSE: To evaluate accuracy of needle localisation using and signal enhancement on a 1.OT MR imager for various needles for MR-guided biopsy. METHODS: The differences between actual and virtual needle position of needles with different orientations were evaluated in a phantom for spin-echo including turbo-spin-echo sequences. RESULTS: Artifacts depended on the orientation of the needle relative to the field B0, frequency-encoding gradients (Gf) and slice orientation. This resulted in different artifact shapes and sizes for left or right and cranial or caudal biopsy access routes. Applying turbo spin echo sequences feasible for biopsy, the signal void of a 18 G needle (Cook) parallel to Gf reached between 0.3 and. 4.6 mm further into the medium than the real needle tip, depending on needle orientation relative to B0. The diameter of the signal void around the needle varied, the needle shaft was right in the centre of the signal void. With Gf orthogonal to the needle the offset of signal void to needle tip ranged from 2.7 to 3.3 mm, while the actual position of the needle shaft was up to 3.3 mm lateral of the signal void center. While nominal echo times did not influence the size of the artifact in turbo-spin-echo sequences, the artifacts increased with smaller matrix and larger water-fat shift. Material and mass of the needle determined the size of the artifacts as well. CONCLUSION: Localisation accuracy of the needle can be optimised by choosing optimal gradient directions depending on whether needle tip or shaft position should be displayed.

Artifacts↗
PubMed1997

CT and MR imaging in primary cerebral non-Hodgkin's lymphoma.

PURPOSE: To determine the morphological appearance and topographical distribution of primary cerebral non-Hodgkin's lymphoma (NHL). MATERIAL AND METHODS: CT and MR examinations of 68 patients with primary cerebral NHL were analyzed. The NHLs were classified by the Kiel classification and immunohistological data, as centroblastic (25), immunoblastic (24), lymphoblastic (5), Burkitt (1), non-subclassifiable type B (11), and T-cell lymphoma (2). RESULTS: Centroblastic lymphomas tended to predominate in the parietal lobe (56.5%) and the corpus callosum (59.1%) while immunoblastic lymphomas were mainly distributed in the frontal lobe (52.8%). About 2/3 of all NHLs showed a multifocal occurrence. Important for differential diagnosis, ventricular involvement was proved in 83.3% of these cases. In the remaining 26 patients with a solitary lymphoma, a periventricular location could be detected in only 8 cases. Central necroses were frequent in HIV-positive patients (7/11, 63.6%) but rare in the HIV-negative patients (9/57, 15.8%). On T2-weighted SE MR images, 8/11 centroblastic lymphomas gave a signal that was isointense with, or lower than, that of the contralateral white matter, while 8/10 immunoblastic lymphomas gave a higher signal. CONCLUSION: The radiological finding of multifocal brain lesions with ventricular involvement is relatively specific for primary cerebral NHL. However, subclassification on the basis of the CT or MR imaging results is not yet possible.

Adult↗
PubMed1997

Nontraumatic subarachnoid hemorrhage: value of repeat angiography.

PURPOSE: To evaluate the benefits and risks of repeat cerebral angiography in patients with subarachnoid hemorrhage of unknown cause. MATERIALS AND METHODS: Findings from 391 angiographic examinations (323 initial, 68 repeat) were retrospectively reviewed in 323 patients with nontraumatic subarachnoid hemorrhage to determine the cause of bleeding and the frequency of complications with neurologic deficit. RESULTS: At the initial angiographic examination, aneurysms were found in 195 patients (60.4%), and arteriovenous malformations were found in 11 patients (3.4%). Sixty-six patients with negative findings at initial examination underwent repeat cerebral angiography. Three additional aneurysms were detected, all of which could be seen retrospectively on the initial angiogram. In 63 patients, the cause of bleeding remained unexplained. Complications of the 391 angiographic examinations were definitive neurologic deficits in one patient (0.2%) and transient deficits in seven patients (1.8%). CONCLUSION: Repeat angiography is not necessary in patients with subarachnoid hemorrhage if technically good, carefully evaluated digital subtraction angiography was performed initially. Repeat angiography seems to be justified only when the initial examination is technically inadequate, when vasospasm is present, or if further bleeding occurs.

Adolescent↗
PubMed1997

[Diagnostic value of digital projection radiography in comparison with conventional roentgen technique].

Digital projection radiography provides digital data in x-ray examinations, which used to be carried out by examinations screen-film system combinations. The technological basis and clinical performances of digital luminescent radiography (DLR) and digital radiography are reviewed. Digital projection radiography does not allow to reduce selenium exposure significantly, compared to screen-film system combinations. Digital luminescent radiography can be used for the entire spectrum of analogous projection radiography the only exception being extremely subtile structural changes. The clinical experiences with digital selenium radiography achieved so far in chest x-rays are promising and the technique is expected to be increasing used in other anatomic regions as well.

Humans↗
PubMed1996

[Postoperative follow-up in hepatic echinococcosis].

OBJECTIVE: To determine whether the monitoring of patients who have undergone surgical excision of hydatid cysts of the liver is useful. Furthermore, sonographic and computertomographic criteria of recurrent hydatid disease should be described. PATIENTS AND METHODS: Of 84 patients operated on for hepatic hydatid disease 42 (22 men, 20 women; mean age 44 [25-82] years) were examined between 6 months and 15 years post-operatively (median of 6 years) clinically, serologically (complement-fixation reaction, immunohaemagglutination) and by ultrasound. If the latter was positive, computed tomography was also performed. RESULTS: Recurrence of hydatid disease in the liver was diagnosed in three patients and in the peritoneal cavity in one patient. The demonstration of internal septa by solitary or multiple daughter cysts proved to be a reliable imaging criterion. CONCLUSION: Ultrasonography should be performed as a baseline test after surgical removal of hydatid cysts in the liver and specific antibody titres measured. This will make it easier to distinguish a recurrence from postoperative changes.

Adult↗
PubMed1996

Iodixanol vs iopamidol in intravenous DSA of the abdominal aorta and lower extremity arteries: a comparative phase-III trial.

Iodixanol (Visipaque, 320 mgI/ml) was compared with iopamidol (Solutrast, 370 mgI/ml) in a double-blind, randomized, parallel group, intravenous DSA phase-III trial for evaluation of safety and efficacy. A total of 117 patients received iodixanol (n = 60) or iopamidol (n = 57). Diagnostic efficacy was evaluated using categoric and visual analogue scales. Discomfort and adverse events were recorded. A total of 39 patients collected urine up to 72 h after the examination for analysis. Diagnostic efficacy and radiographic density were similar in both groups. Discomfort was milder with iodixanol. The difference between the frequency of adverse events between both groups (iodixanol = 7, iopamidol = 2) was without statistical significance. Creatinine clearance was slightly more affected by iodixanol, whereas the increase in renal excretion of N-acetyl-beta-glucosaminidase (NAG) in the first 24-h collection period after the examination was significantly higher (p < 0.01) with iopamidol. Iodixanol was of equal diagnostic efficacy compared with iopamidol despite its reduced iodine content. Both contrast media are well suited for IV DSA.

Acetylglucosaminidase↗
PubMed1996

Lesions of the corpus callosum in hydrocephalic patients with ventricular drainage--a CT-study.

Patients with ventricular drainage may develop lesions of the corpus callosum. In order to study frequency, pathogenesis and clinical relevance of callosal lesions, 301 routine CT investigations of 79 patients with ventricular drainage were reviewed. Hypodense lesions in the anterior part of the corpus callosum were observed in 7 patients with longstanding hydrocephalus of variable origin, in 2 cases the corpus callosum was slightly swollen. All 7 patients showed signs of forced ventricular drainage. The callosal alterations were clinically inapparent and potentially reversible. Knowledge of these lesions is important to avoid misinterpretation.

Adolescent↗
PubMed1996

Pharmacokinetics of intraarterial mitomycin C in the chemoembolisation treatment of liver metastases.

1. The pharmacokinetics of mitomycin C (MMC) were investigated in 12 colorectal cancer patients with liver metastases undergoing chemoembolisation. Hepatic artery branches were embolized using polyvinylalcohol microspheres (150-250 microns) before applying 20 mg MMC in 4-8 min. 2. Serum MMC concentrations were determined from peripheral venous blood samples by reverse-phase HPLC using ultraviolet detection. Pharmacokinetic parameters were computed assuming an open two-compartment model. 3. Pharmacokinetic parameters were similar to values given in the literature for intravenous (IV) or intraarterial (IA) bolus MMC injections (Tmax = 7.0 min following the beginning of MMC infusion, Vss = 0.57 1/kg, C1 = 8.9 ml/min.kg, T1/2 alpha = 8.3 min, T1/2 beta = 58.6 min). 4. The area under the serum concentration-time-curve (AUC), standardized by the MMC amount injected, was similar to values reported in the literature for IV or IA bolus injections. There is no evidence for reduced systemic MMC exposure following the embolization procedure used.

Antibiotics, Antineoplastic↗
PubMed1996

[A prospective study to assess the need for requested radiological studies].

PURPOSE: What is the percentage of non-indicated examinations in the routine work of a radiologic university clinic? METHODS: From April 1st, 1994, to June 30th, 1994, all examinations carried out in the Radiology Department of the University Hospital of Cologne, Germany, were evaluated prospectively by the radiological medical staff using a questionnaire. The question was whether the examinations were medically indicated or not. Requests for examinations which were not carried out due to lacking indications were excluded from evaluation. The percentage of error was assessed by analysis of random samples assigned to the referring clinicians. RESULTS: 1400 (5.4%) of a total of 25718 examinations were considered by the radiological medical staff as "not indicated". A subsample analysis performed for validation gave an upper margin of a 95% confidence interval of about 13% for this rating. The percentage of non-indicated examinations was higher in conventional x-ray examinations and ultrasonography than in x-ray angiography, computed tomography and magnetic resonance tomography. Examinations during night time and weekend showed a higher percentage of lacking medical indications than examinations during daytime. CONCLUSIONS: Considering a university clinic concerned with educational work, the percentage of radiological examinations carried out without medical indication was tolerable. However, indications must be further improved by intensifying the communication with the referring clinicians and by elaborating a higher standard of radiological and clinical postgraduate training.

Diagnostic Tests, Routine↗
PubMed1996

[The radiological findings in surgically and conservatively treated intracranial arachnoid cysts].

PURPOSE: To determine which appearances on CT or MRI are indications for surgical treatment of intracranial arachnoid cysts. METHOD: The images obtained from 26 patients treated either by surgery or conservatively were compared retrospectively. The features evaluated were the size of the cyst, evidence of a space-occupying lesion, cerebral abnormalities near the cyst and skull deformities. RESULTS: In 6 patients (23%), surgical treatment was indicated because of the presence of obstructive hydrocephalus. The presence of all other radiological findings did not differ significantly between the two analysed groups. 92% of the patients treated surgically benefited from the treatment. Fenestration and shunting produced similar results in respect to reduction in size of the cyst and the clinical and neurological symptoms. CONCLUSION: The only indication for surgery is the presence of obstructive hydrocephalus. The other features were seen equally amongst the patients treated conservatively and the surgical patients and had no influence on the decision to operate.

Adolescent↗
PubMed1996

[The MR tomographic diagnosis of intra- and paraspinal abscesses].

PURPOSE: Analysis of the MRT signals and their extent from intra- and paraspinal abscesses with reference to predisposing factors, their causes and localisation. PATIENTS AND METHODS: The histories and MRT findings in 34 Patients with intra- and paraspinal abscesses were evaluated retrospectively. Most of the patients (24/34) were older than 50 years. A second peak was below 30 years. RESULTS: 27/34 patients had some underlying disease which predisposed to infection, e.g., diabetes mellitus. The most common causal organisms were Staph. aureus (53%) and streptococci (15%). In 23/34 cases (68%), the abscesses were in the thoraco-lumbar or lumbar region, while only 6/34 occurred in the upper two-thirds of the thoracic spine and only 5/34 in the cervical region. In only 8/34 was the abscess confined to two vertebral lengths; in the remaining patients it was much more extensive. Intraspinal abscesses were about twice as large as the vertebral components and 1.5 times greater than paravertebral abscesses. The age of the abscesses could be estimated approximately from the signals. CONCLUSIONS: Contrast enhanced MRT permits detailed analysis of the compartments and exact estimation of the extent of the lesions and permits accurate monitoring of treatment.

Abscess↗
PubMed1996

Angiographic detection of gastrointestinal bleeding. An experimental comparison of conventional screen-film angiography and digital subtraction angiography.

RATIONALE AND OBJECTIVES: The authors experimentally assess and compare the detection limit of gastrointestinal bleeding in digital subtraction angiography (DSA) and conventional screen-film angiography. MATERIALS AND METHODS: Arterial blood flow was simulated using a tube model in which bleeding was imitated by exudation of liquid containing contrast material. Gut peristalsis was imitated using silicone tubes filled with air and liquid. Images were acquired by DSA and conventional screen-film angiography. The iodine concentration was increased in increments from 1 mg I/mL, with and without simulated peristalsis, and with both free and circumscribed extravasation of contrast material. RESULTS: The detection limit for free extravasation in DSA was 1 mg I/mL without peristalsis and 60 mg I/mL with peristalsis. The corresponding figures for circumscribed extravasation were 1 mg I/mL and 34 mg I/mL. The detection limit for free extravasation in screen-film angiography was 172 mg I/mL both with and without simulated peristalsis. Circumscribed extravasation was detected at 9 mg I/mL without peristalsis and 7 mg I/mL with peristalsis. CONCLUSION: Digital subtraction angiography is the more sensitive angiographic technique for detection of gastrointestinal bleeding and is superior to conventional screen-film angiography, provided that it is performed with adequate parasym-pathicolysis and suspended respiration. Only when these requirements cannot be achieved is screen-film angiography advantageous.

Angiography↗
PubMed1996

Recurrent bleeding of angiomyolipomas in tuberous sclerosis.

The diagnostic and therapeutic problems of renal hamartomas are illustrated by a case of recurrence of bleeding angiomyolipomas associated with tuberous sclerosis. Ultrasound and computed tomography provide clear evidence of lipomatous formation while, in rare instances, angiography can demonstrate the existence of multiple vascular tumor compartments. In view of the risk of bleeding, multiple or very large angiomyolipomas should be treated by interventional radiology in the form of superselective tumor embolization or by the most conservative surgery possible.

Adult↗
PubMed1996

Lipoprotein(a)-apheresis in the secondary prevention of coronary heart disease.

Lipoprotein(a) [Lp(a)] is one important cause of atherosclerosis. It consists of one molecule of low density lipoprotein and an additional molecule of apo(a) linked to apoB-100 by a disulfide bridge. Apo(a)s are partially homologous to plasminogen, with one kringle 5 and 10-40 repeats of kringle 4. As there is no drug therapy available, we treated three patients who had suffered from at least one myocardial infarction and had Lp(a) as the only risk factor for atherosclerosis. Since October 1992, 186 immunoadsorption treatments have been carried out weekly with Sepharose-coupled anti-Lp(a)-columns. To achieve a reduction in Lp(a) from 78-250 mg/dL before apheresis to below 25 mg/dL immediately after apheresis, patient plasma volume had to be treated two to three times. Treatments lasted 3-5 h. Immediately reversible side-effects such as flushing and tachycardia during the first treatment were seen in 9% of immunoadsorptions. Non-specific protein loss remained tolerable, if one takes into account that the patients received approximately 1 L of ACDB with heparin as anticoagulant and some of the column-rinsing buffer. One patient's clinical condition and exercise test improved dramatically as did coronary angiography after 2 years. Another patient had no change after 1 year, the third patient showed subjective improvement and has not yet had repeat angiography after 1 year of treatment. We conclude that Lp(a)-apheresis may retard progression of atherosclerosis in patients with selective Lp(a) elevation. Further studies to support this hypothesis are needed.

Adult↗