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Biomedical subjects

K Lackner

Publications and source records attributed to K Lackner.

At least 73 records · Page 4Linked to original sources
PubMed1999

[MR-compatible and conventional marker wires in breast diagnosis--experimental studies on their dislocatability and artifact size in MRT].

PURPOSE: Localization of non-palpable suspicious breast lesions with tumor localization wires is commonly used before surgical excision. Dislocation of the wire is possible. The possibility of dislocation for different types of tumor localization wires was examined experimentally. METHODS: 22 different tumor localization wires were inserted into the subcutaneous fat-tissue of a pig. The wire tip was recorded under fluoroscopy. Traction was applied to the wire using a spring-balance. The artifact size of MR-compatible wires was examined in a 1.0 Tesla MR imager. RESULTS: The localization wires with an X-configuration and long hook could not be dislocated by a force up to the maximum of 12 Newton. The retractable localization wires were easily dislocated at traction forces of 1 Newton. Other wires with only one hook could withstand a traction from 2 up to 7 Newton. The wires with a Z-configuration and wires with short hooks showed a highly variable rate of resistance. The artifact size of localization systems was between 10.1 and 11.0 mm for gradient-echo sequences and between 6.7 and 7.1 mm for spin-echo sequences. CONCLUSION: Tumor localization wires with an X-configuration and long hooks were best anchored in the tissue. The advantage of repositioning retractable wires is confined by the high risk of accidental dislocation. No reliable fixation in the tissue could be achieved using wires with a Z-configuration and wires with short hooks. MR-compatible wires were comparable to non-MR-compatible wires concerning the rate of resistance. The size of the artifacts of MR-compatible systems showed no relevant differences.

Adipose Tissue↗
PubMed1999

Spiral CT angiography of the abdominal aorta. Comparison of iodixanol and ioversol.

RATIONALE AND OBJECTIVES: Enhancement characteristics of a nonionic, dimeric, isotonic contrast medium (iodixanol [Visipaque]) were compared with a nonionic, monomeric contrast medium (ioversol [Optiray]) of the same iodine concentration in spiral computed tomography angiography (CTA) of the abdominal aorta. METHODS: Spiral CTA was performed in 78 patients referred for suspected renal artery stenosis (n = 35) and abdominal aortic aneurysm (n = 43). A test bolus was used to time the scan delay, and all patients were injected with 150 ml contrast medium (320 mgI/ml) of either iodixanol (n = 40) or ioversol (n = 38). Contrast enhancement was measured in the aorta, renal arteries, and renal parenchyma. RESULTS: All mean aortic enhancement was slightly higher with iodixanol than ioversol, measured at three different levels (celiac trunk 315 Hounsfield units [HU] versus 300 HU, renal arteries 325 HU versus 312 HU, aortic bifurcation 276 HU versus 266 HU). However, none of them were statistically significant (e.g., P = 0.26 at the celiac trunk level). Similar results were observed in renal artery and parenchyma enhancements. CONCLUSIONS: Iodixanol and ioversol had similar enhancement characteristics in the early arterial phase. Both substances were well tolerated and seem to be well suited for spiral CTA.

Adult↗
PubMed1999

Positron emission tomography using 18F-fluorodeoxyglucose in advanced stages of malignant melanoma: a comparison of ultrasonographic and radiological methods of diagnosis.

The diagnostic and therapeutic impact and the cost-effectiveness of positron emission tomography (PET) using 18F-fluorodeoxyglucose (FDG) will depend on the role for which the tests are used. In 68 patients with advanced malignant melanoma, original sets of FDG-PET images from various institutes were compared with findings obtained by ultrasonography, conventional radiology, computed tomography (CT) and magnetic resonance imaging. In 22 patients, all examinations were undertaken within 2 weeks and strategies of staging were analysed. In 46 patients, only some of these examinations were performed within this time period, and comparison of methods was restricted to the examined organs. The occurrence of metastasis, without specifying the number of foci, was detected by either conventional staging with CT or by PET in 20 of 22 patients. None of these patients were up- or down-staged by FDG-PET compared with CT staging. In the 68 patients as a whole, FDG-PET detected fewer pulmonary and hepatic metastases and fewer cerebral foci, but more lymph node and bone metastases than conventional radiology or CT. For the detection of lymph node or skeletal metastases, false-positive FDG-PET findings were taken into account when compared with follow-up data. In advanced melanoma, FDG-PET did not influence the pattern of subsequent diagnostic testing. Thus, indications for FDG-PET include pre-metastatic melanoma, localized lymph node metastases and monitoring of the response to treatment.

Adolescent↗
PubMed1999

[The lymph node staging of malignant testicular germ-cell tumors].

Imaging procedures are important in the initial staging and subsequent management of testicular germ cell tumors on account of the differing stage-dependent options for therapy. While the diagnosis of advanced tumors gives no cause for controversial discussion the situation in the clinical stage 1 of germ cell tumors is more ambiguous. The lymph node status is only assessed correctly in about 70% of the patients using the currently available methods since metastases in normally large lymph nodes are not detected on slice images. Although most clinical experience has been gained with computed tomography (CT), magnetic resonance imaging (MRI) offers an equally efficient diagnostic procedure. The significance of positron emission tomography with 18-fluorodeoxyglucose (FDG-PET) appears to be limited on account of the absence of accumulation in lymph node metastases of the differentiating teratoma. Sonography and lymphography have not proved to be useful for retroperitoneal lymph node diagnosis. The present review presents and discusses the current value of the available imaging procedures for staging and follow-up of malignant testicular germ cell tumors in relation to modern therapy regimens.

Adolescent↗
PubMed1998

Somatosensory evoked potentials: a simple neurophysiological monitoring technique in supra-aortal balloon test occlusions.

The aim of this study was to evaluate somatosensory evoked potentials (SEP) as a simple neurophysiological monitoring method in supra-aortal balloon test occlusions (BTO). The 13 patients examined had carcinoma of the larynx (n = 6), nasopharyngeal malignancy (n = 3), sphenoid meningioma (n = 2), mycotic aneurysm (n = 1), and a tumor of the carotid body (n = 1). Transfemoral balloon occlusion of the internal carotid artery was maintained for 30 min and monitored both clinically and by SEP. None of the 13 patients showed neurological deficits or pathological changes in the SEP. No thromboembolic complications occurred during BTO. In 11 cases the cervical vessels could be spared or reconstructed during surgery. No neurological symptoms occurred during the clinical follow-up. One patient died the day after BTO due to cardiac arrest. Neurophysiological monitoring of preoperative BTO using SEP is a technically simple method. A similar method has been shown to have a high sensitivity and reliability in carotid surgery.

Adolescent↗
PubMed1998

Influence of the hepatobiliary contrast agent mangafodipir trisodium (MN-DPDP) on the imaging properties of abdominal organs.

To assess the influence of Mangafodipir Trisodium on the imaging properties of abdominal organs when using T1-weighted gradient-echo (GE) and T2-weighted turbo spin-echo (TSE) sequences, thirty patients with focal lesions in the liver were examined at a field strength of 1.5 T before and after intravenous administration of Mangafodipir Trisodium (dose: 5 micromol/kg of body weight). Administration of Mangafodipir Trisodium led to a significant increase in the signal intensity of the liver tissue (p < 0.001), the spleen (p < 0.01), the pancreas (p < 0.001), and the kidneys (p < 0.001) in the T1-weighted GE sequence, while there was no relevant enhancement in fatty tissue and the musculature. In the T2-weighted turbo spin-echo sequence, there was no relevant change in the signal following administration of a contrast agent. The contrast-to-noise ratio (C/N) between the lesions and the liver tissue increased significantly in the post-contrast T1-weighted GE sequence (p < 0.001), while there was no change in the contrast-to-noise ratio in the post-contrast T2-weighted turbo spin-echo sequence. The contrast-to-noise ratio of the plain T2-weighted TSE sequence was significantly higher than that in the post-contrast T1-weighted GE sequence (p < 0.001). Although Mangafodipir Trisodium was primarily developed as a hepatobiliary contrast agent for demonstration and differentiation of liver lesions, it also affects the signal levels in the pancreas, spleen, and kidneys in the T1-weighted image. Awareness of this effect on the extrahepatic tissue makes it easier to interpret pathological findings in magnetic resonance imaging (MRI) of the abdomen.

Abdomen↗
PubMed1998

[Digital selenium radiography: a comparison of the picture quality of thoracic images in normal and reduced image formats based on the structural anatomical details].

PURPOSE: Is there a loss of information when using selenium radiographic images displayed with reduced image format compared to full format? METHOD: Digital selenium radiographic chest images in two planes were obtained in 35 patients for medical reasons. The digital data sets of each patient were separately displayed in full format on two different films and were printed in reduced format on one film. The format was reduced to 61% of the full format using an acquisition matrix of 2166 x 2488 pixels, an image display matrix of 4000 x 5000 pixels and a film format of 43 x 49 cm. All images were anonymously evaluated by four independent readers using a questionnaire concerning anatomic structures. RESULTS: Format reduction did not result in a loss of information in diagnostically relevant anatomic details. CONCLUSIONS: Displaying digital selenium radiographic data sets of thoracic view in two planes on one film presumably does not lead to a loss of diagnostic information. This procedure may help to reduce film costs.

Adult↗
PubMed1998

[Direct-current treatment of chemically induced mammary carcinoma in an animal model: MR volumetric assessment of the effect of the therapy].

PURPOSE: To investigate the effect of direct current treatment (DCT) on the growth of mammary carcinomas in rats by MR-volumetry. METHODS: Chemically induced mammary adenocarcinomas in a control group (n = 17) were compared with treated tumours (18 C/cm3 in group A: n = 7 or 36 C/cm3 in group B: n = 12). 31 untreated tumours were situated near a treated tumour (group C). Experiments were carried out using one positive electrode in the tumour centre and three negative electrodes in the periphery. The tumour volume was measured by MRI before, and 1, 3, 6, 9 and 12 weeks after treatment. RESULTS: 12 weeks after DCT, the mean tumour volume in group A (164% +/- 158%, p < 0.05) and group B (13% +/- 24%, p < 0.001) was significantly reduced compared to the control group (434% +/- 230, Mann-Whitney U-Test). Complete tumour regression occurred in 42% of tumours in group B and was not achieved in group A, C and control group. Tumour growth in group C was decreased compared to the control group. CONCLUSIONS: The effectiveness of DCT was found to depend on the applied dosage -36 C/cm3 was more effective than 18 C/cm3. The effect of DCT is not limited to the area between the electrodes.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1998

[Correlation of MRI and histopathological findings in inflammatory skin diseases].

PURPOSE: Can spatial and contrast resolution be achieved with currently available MR devices for the successful assessment of inflammatory diseases of the skin? METHOD: High resolution MRI was performed in 20 patients with non-malignant diseases of the dermis and subcutis. The skin biopsies subsequent to the MR examinations were indicated for clinical reasons. The MR examinations were done in the location of later performed skin biopsies using a 1.0 Tesla system (Gyroscan T10 NT, Philips, Best, the Netherlands) and a surface coil of 7.5 cm inner diameter. Conventional spin-echo (SE-Sequenz)- and gradient-echo (GRE)-sequences were optimised to obtain maximum spatial resolution with a sufficient signal-to-noise ratio within a tolerable examination time. MR visualisation of histopathology was assessed by four readers using a questionnaire. RESULTS: In 15 of 20 cases, high resolution MRI allowed a correct classification of the visualised dermal and subcutaneous patterns, in accordance with the histological work-up of the corresponding specimen. Due to the still only suboptimal spatial and contrast resolution the structure of the epidermis could not be assessed adequately. Determination of contrast enhancement or non-enhancement after administration of intravenous contrast agent provided information on the degree of tissue perfusion in 19 patients, which complemented the morphological assessment. CONCLUSION: High resolution MRI allows to identify non-invasively histological main patterns of inflammatory skin diseases. However, final diagnosis often depends on higher microscopic resolution and special staining.

Adolescent↗
PubMed1998

[Endorectal MRI and ultrasonography in rectal tumors: correlation with histological staging].

PURPOSE: To compare the accuracy of high resolution endorectal magnetic resonance imaging (EMRI) and endorectal ultrasound (EUS) in the preoperative diagnostic of rectal tumours. PATIENTS AND METHODS: Twenty-one patients with known rectal tumours underwent MR imaging with an endorectal surface coil and EUS. Transversal EMR images were obtained using fast T2-weighted sequences and pre- and postcontrast T1-weighted images. EUS was performed using a 7.0 MHz transducer. Results of both methods were compared with specimens from the resected tumours. RESULTS: Rectal wall layers were reliably demonstrated with both methods in all patients. EMRI and EUS determined the depth of rectal wall invasion. EMRI and EUS agreed with pathologic findings in 16/21 cases, respectively. In one case each, both methods understaged one tumour. EMRI overstaged an adenoma as a T2-tumour. In three and four patients, respectively, no staging was possible due to technical problems. CONCLUSION: EMRI and EUS show comparable results in the preoperative T-staging of rectal tumours. Both techniques are not suitable for differentiating benign from malignant lymph nodes accurately. While EMRI is expensive and technically demanding, it allows an objective documentation of pathological findings which is less dependent on the examiner. Two important clinical conclusions can be drawn from the good results of T-staging: Adenomas and T1-tumours can be treated by local excision. In patients with advanced tumours (T3/T4) a neoadjuvant therapy can be initiated.

Adenoma↗
PubMed1998

High-resolution MR imaging of the cutis and subcutis. Histological correlation.

OBJECTIVE: To determine whether the spatial resolution that can be achieved with currently available MR devices is adequate for the evaluation of skin disease. MATERIAL AND METHODS: We correlated high-resolution MR images of the skin with dermatohistopathology in 26 patients. The examinations were carried out on a 1.0 T imager using a commercially available surface coil (ID 7.5 cm) and optimized SE and GE sequences. Image quality was assessed by four readers on a questionnaire. RESULTS: The visualization of the dermis, subcutaneous tissue, and muscle fascia allowed a pattern analysis that gave findings identical to those at dermatohistopathology. It was possible to distinguish septal from lobular panniculitis, and lipatrophia from sclerodermia. Images with contrast media infusion were useful in the differential diagnosis. CONCLUSION: High-resolution MR imaging may narrow down the differential diagnosis of various skin diseases and may help to reduce the number of skin biopsies on certain indications.

Adolescent↗
PubMed1998

Detection of focal hepatic lesions: effects of superparamagnetic iron oxide (AMI-25) on magnetic resonance imaging of the liver using T2-weighted fast spin-echo sequences and gradient-and-spin-echo sequences at 1.0 tesla.

RATIONALE AND OBJECTIVES: The authors evaluate the value of two fast spin-echo sequences (FSE) with different T2-weighting (repetition time [TR]/echo time [TE] = 2000/90 mseconds and TR/TE = 2000/40 mseconds) and combined gradient-and-spin-echo sequences (TR/TE = 2000/90 mseconds) for contrast-enhanced liver imaging with superparamagnetic iron oxide (AMI-25). METHODS: Forty-seven patients with focal liver lesions underwent magnetic resonance imaging at 1.0 tesla. AMI-25 was administered intravenously at a dose of 15 micromol iron/kg. RESULTS: Administration of AMI-25 resulted in a significant increase of lesion/liver contrast-to-noise ratio (C/N) for all T2-weighted sequences (P < 0.001). On the precontrast images, the FSE sequence with a TE of 90 mseconds had the highest C/N (16.0 +/- 4.5) whereas the best postcontrast C/N (27.9 +/- 7.6) was obtained with the mild T2-weighted FSE sequence with a TE of 40 mseconds. CONCLUSIONS: Fast spin-echo sequences are valuable sequences for imaging of the liver at 1.0 tesla. For AMI-25-enhanced magnetic resonance imaging, a mild T2-weighted FSE sequence is recommended.

Adult↗
PubMed1998

Proton MR spectroscopy in infants with cerebral energy deficiency due to hypoxia and metabolic disorders.

PURPOSE: To investigate the similarities and differences of cellular energy deficiencies due to asphyxia and to impaired oxidative phosphorylation caused by enzyme deficiencies using localized 1H-MR spectroscopy of the brain. MATERIAL AND METHODS: In 35 neonates and infants with a postconceptional age of 36.4-153 weeks, 1H-MR spectra were obtained from the basal ganglia. Of the 35 children, 14 served as a control group, 12 suffered from hypoxic-ischemic disease (HIE), and 9 had congenital enzymatic disorders. RESULTS: Eleven of the 12 children with HIE showed low N-acetyl aspartate (NAA) to trimethylamine (TMA) ratios, indicating neuronal damage. Lactate (Lac) to TMA ratios correlated with the HIE grade. Children with congenital disorders of energy metabolism had NAA/TMA ratios ranging from severely decreased to normal, but 7 of the 9 had high Lac signals, even in brains with normal NAA/TMA. CONCLUSION: High Lac/TMA even with normal NAA/TMA in children with enzyme deficiencies, in contrast to Lac/TMA that correlates with clinical grade and low NAA/TMA in asphyxic children, hints at different mechanisms of cell damage in the two disease groups.

Aspartic Acid↗
PubMed1998

[Interventional palliative therapy].

From diagnostic procedures interventional radiology has developed a large number of therapeutic methods that have found a place in the treatment of palliative care patients. Minimal invasiveness and high efficiency characterise the implantation of metallic stents in the treatment of malignant biliary or esophageal obstruction and vena cava compression syndrome. Transcatheter arterial embolisation, chemoembolisation and chemoinfusion for palliative treatment of inoperable liver malignomas are performed at many centers. A specific concept and an accepted spectrum of indications have to be better defined by prospective trials. Therapeutic decisions in this patient group have to based on the individual case. The interventional radiologists is increasingly involved in the interdisciplinary decision making process.

Bile Duct Neoplasms↗
PubMed1997

Connective tissue reactions in subdural haematomas: imaging with contrast-enhancement MRI.

The sensitivity of contrast enhanced magnetic resonance imaging (MRI) in the detection of connective tissue reactions accompanying the maturation of subdural haematomas (SDH) was studied. An outer enhancing layer between the SDH and the tabula interna of the vault was shown in 16 out of 17 cases. In early SDH this outer enhancing layer presumably is due to vascular congestion and/or increased vascular permeability. A thickening of the outer enhancing layer and/or an inner enhancing layer between the haematoma and the subarachnoid space was visible in 9 patients and represented a haematoma capsule formed by proliferating granulation tissue. In 5 SDH septations were found, 3 SDH consisted almost completely of enhancing granulation tissue. Thus, contrast enhanced MRI delivers additional information about the structure of SDH, which are useful for determining the extent of surgical treatment especially in chronic SDH.

Adolescent↗