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Biomedical subjects

C D Claussen

Publications and source records attributed to C D Claussen.

At least 217 records · Page 12Linked to original sources
PubMed1997

[Mammography and mammary ultrasonography: which examination sequence is preferable?].

PURPOSE: To compare primary mammography diagnosis (ultrasound report available) with primary ultrasound diagnosis (mammography report available). METHODS: 89 preoperative patients with suspicious lesions were included. Mammography and ultrasound of all patients were evaluated by two independent experienced readers under clinical conditions. The reports of the complementary modality were available to both observers. Lesion evaluation was done on a per breast basis, in cases of multiple lesions in respect of the lesion with the greatest risk of malignancy. RESULTS: 39 benign and 59 malignant lesions were found. Primary mammography and primary ultrasound yielded 3 and 8 false positives and 10 and 13 false negatives. Concerning the palpable lesions (n = 59), primary mammography and primary ultrasound had no and 4 false positives and 7 and 8 false negatives, respectively, for the non palpable lesions, the figures were 3 and 4 false positive and 3 and 5 false negatives. CONCLUSIONS: Mammography remains the method of first choice in early detection of breast cancer, whereas breast ultrasound should be performed after and in knowledge of the mammogram, in consideration of the known indications (equivocal palpable lesion and mammographic opacity, dense breast).

Adolescent↗
PubMed1997

[Contrast-enhanced MR cholangiography in percutaneous bile duct drainage].

PURPOSE: To evaluate MR-cholangiography after instillation of contrast media via indwelling biliary tubes. METHODS: In 8 patients with stenoses of the central bile ducts, physiological saline solution and diluted contrast media (Gd-DTPA, 5 mmol/l) were consecutively administered via an indwelling biliary tube. MR cholangiograms were obtained before and after saline injection using a HASTE-sequence and after administration of Gd-DTPA using a T1-weighted gradient echo sequence. RESULTS: Peripheral bile ducts were better visualised in the water-sensitive approach than after Gd-DTPA enhancement. In patients with short-time drainage bile duct definition was poor due to periportal oedema. Visualisation of peripheral bile ducts could be improved by injection of saline solution in these patients. After administration of Gd-DTPA via the biliary tube contrast enhancement of the central bile ducts was achieved in all patients except for one patient on long-term drainage with an indwelling Yamakawa tube. CONCLUSION: T1-weighted visualisation of the central bile ducts can be achieved by means of injection of Gd-DTPA via indwelling biliary tubes.

Adult↗
PubMed1997

[MR tomography studies of myocardial function and perfusion after myocardial infarct].

PURPOSE: With the advent of fast pulse sequences, MR imaging of myocardial function and perfusion in ischaemic heart disease has become possible. Prior studies examined either myocardial perfusion or systolic wall motion. We intended to establish an examination procedure to simultaneously investigate regional myocardial motility and perfusion in patients 7-14 days after myocardial infarction. METHODS: A Turbo-FLASH 2D sequence was optimised to maximise image contrast between normal and malperfused myocardium after Gd-injection using a calculation model basing on the Bloch equation. Calculated values for trigger delay TD, inversion time TI and flip angle alpha were confirmed in a Gd-phantom and healthy volunteers. Subsequently, myocardial motility was studied (cine FLASH 2D sequence) and in slice positions with reduced wall thickening first pass and post contrast studies after 2-10 minutes were performed using the optimised Turbo-FLASH sequence. RESULTS: First pass SI-differences of normal compared to malperfused myocardium vary in relation to TD, TI and alpha in a relevant degree. Reduced myocardial motility was found with a sensitivity of 81% and specificity of 96%. Pathological perfusion patterns were detectable in all of these patients. CONCLUSIONS: A combined examination of motility and perfusion is possible by means of MRI and information about the status of postinfarct myocardium can be obtained.

Adult↗
PubMed1997

[Radiofrequency ablation of the liver in vitro: increasing the efficacy by perfusion probes].

PURPOSE: Percutaneous radiofrequency interstitial thermal ablation is a new method in local tumour therapy. The aim of this study was to define the relations between the variable parameters and local efficacy in vitro and to evaluate optimal parameter combinations for this system. Furthermore, we studied the feasibility of increasing the volume of destroyed tissue using perfusion electrodes. MATERIAL AND METHODS: Thermal lesions were produced with radiofrequency in ex vivo pig livers. In separate experiments the parameters wattage (5-30 watts), exposure time (1-15 minutes) and tip exposure were varied. The resulting areas of tissue necrosis coagulation were measured; in 30 of 90 cases the macroscopic findings were compared to the histological findings. RESULTS: Lesion size correlated with tip exposure, wattage and procedure duration up to 10 minutes. For a tip exposure of 2 cm (3 cm) the maximal lesion volume was 18.8 cm3 (33.2 cm3) at a wattage of 20 watts (30 watts) and a procedure duration of 10 minutes. The maximal cross- (length-) diameter of these lesions was 3 cm (4 cm) for 2 cm tip exposure and 3.6 cm (4.9 cm) for 3 cm tip exposure. CONCLUSION: The parameters wattage, procedure duration and tip exposure affect the size of lesions created with radiofrequency under ex vivo conditions. Perfusion electrodes make it possible to produce larger lesions than described for non-perfused electrodes. The ablation of hepatic neoplasms up to a size of 3 cm seems to be possible with a single electrode.

Animals↗
PubMed1997

Phase-contrast MR angiography for detection of arteriosclerotic renal artery stenosis.

PURPOSE: To compare the accuracy of 3-D phase-contrast (PC) MR imaging with a 2-D time-of-flight (TOF) technique in the detection of arteriosclerotic renal artery stenosis. MATERIAL AND METHODS: Twenty-two patients with 28 angiographically proven renal artery stenoses were examined in a prospective blinded fashion by using 2-D TOF MR angiography (MRA) with venous saturation (FLASH) and 3-D PC MRA. The renal arteries were subdivided into 3 segments and graded for the presence of stenoses on a scale of 0-4 by 3 radiologists in blind. RESULTS: The accuracy of TOF and PC imaging in detecting renal artery stenoses was 65% and 77% respectively. Both 2-D TOF and 3-D PC MRA depicted 84% of the stenoses of the proximal renal artery greater than 50% in diameter. Renal artery stenoses greater than 50% and more than 15 mm in distance from the aorta were detected in 40% of cases with the 2-D TOF sequence and in 76% with the 3-D PC technique (p < 0.05). The rate of false-negative results was 32%. CONCLUSION: PC MRA is better at visualizing stenoses in the middle segment of the renal arteries and supplements conventional TOF techniques with additional information. However, even when the two techniques are combined, the false-negative rate in the MR imaging of stenoses of the renal arteries still needs to be reduced.

Aged↗
PubMed1997

Menstrual cycle and age: influence on parenchymal contrast medium enhancement in MR imaging of the breast.

PURPOSE: To evaluate the influence of menstrual cycle and age on parenchymal contrast medium enhancement in magnetic resonance (MR) imaging of the breast. MATERIALS AND METHODS: Dynamic gadolinium-enhanced fast low-angle shot, three-dimensional breast MR imaging was performed with high temporal and spatial resolution (eight measurements in 10 minutes). Menstrual cycle evaluations and age-influence studies were performed in 44 patients aged 27-55 years with a regular cycle (mean age, 41.5 years) and in 103 patients aged 15-79 years (mean age, 49.3 years), respectively. A region of interest was placed in each quadrant of the breast for evaluation of parenchymal enhancement. Quadrants with complete involution or lesions and patients who received hormonal therapy were excluded [corrected]. Analysis of variance was performed. RESULTS: Parenchymal contrast medium enhancement in cycle days 7-20 (geometric mean enhancement at minutes 1-10 = 0.12-0.47) was significantly lower than that in cycle days 21-6 (geometric mean, 0.17-0.98; P < or = .001). Contrast medium enhancement in patients aged 35-50 years (mean enhancement, 0.17-0.75) was significantly higher than that in patients aged younger than 35 years or older than 50 years (mean enhancement, 0.12-0.40; P < .01). CONCLUSION: Patients showed statistically significantly lower parenchymal enhancement in menstrual cycle days 7-20 than in days 21-6. Patients aged 35-50 years yielded higher parenchymal enhancement than did younger patients and older patients.

Adolescent↗
PubMed1997

MR imaging of the liver with Resovist: safety, efficacy, and pharmacodynamic properties.

PURPOSE: To evaluate the safety, efficacy, and pharmacodynamic properties of a new superparamagnetic parenteral iron oxide contrast agent for magnetic resonance (MR) imaging. MATERIALS AND METHODS: Thirty-six patients with liver lesions received a bolus injection of Resovist (SH U 555 A; Schering, Berlin, Germany) at a dose of 4, 8, or 16 micromol iron per kilogram body weight (micromol Fe/kg). Fast low-angle shot, spin-echo, and turbo gradient spin-echo MR images were obtained before and 10, 40, and 70 minutes after injection. Blood samples were obtained, vital signs were monitored, and adverse events were recorded. Lesion detection was assessed by two independent, blinded readers. RESULTS: No drug-related adverse events occurred. Serum iron and ferritin levels were increased at all dose levels. Partial thromboplastin time increased and factor XI level decreased 4 hours after injection of 16 micromol Fe/kg. Lesion detection and diagnostic confidence were increased in patients who received 4 or 8 micromol Fe/kg, with no further increase with a 16-micromol dose. CONCLUSION: Resovist is safe and effective. The best MR imaging results were obtained 40 minutes after injection of 8 micromol Fe/kg.

Adult↗
PubMed1997

Primary choriocarcinoma of the pulmonary artery mimicking pulmonary embolism.

Due to their rarity, primary tumours of the pulmonary arteries are often incorrectly diagnosed as more common diseases such as pulmonary thromboembolism and are seldom diagnosed during a patient's lifetime. Surgery or potentially curative chemotherapy may therefore be withheld. We report a patient with a primary choriocarcinoma of the left pulmonary artery, which was first suspected on a CT scan. The neoplastic nature of the obstruction of the pulmonary arteries was confirmed by positron emission tomography.

Adult↗
PubMed1997

Do mammography, sonography, and MR mammography have a diagnostic benefit compared with mammography and sonography?

OBJECTIVE: The purpose of our study was to assess the added value of MR mammography, mammography, and sonography compared with mammography and sonography in diagnostic evaluation of the breast. MATERIALS AND METHODS: We evaluated reports of MR mammography, conventional mammography, and sonography of the breast in 89 patients who had been referred for surgical biopsy. The dynamic MR mammography examinations were obtained on a 1.0-T MR imager using a double-breast coil and a three-dimensional axial fast low-angle shot sequence. Each type of study was interpreted by a different observer. All mammograms and sonograms were available to all observers. Without knowledge of biopsy results, observers classified mammograms and sonograms (which we call the standard method) as well as mammograms, sonograms, and MR mammograms (which we call the combined method). Classifications were on a per-breast basis: no disease; probably a benign or malignant lesion; and most likely a benign or malignant lesion. A classification of no disease or most likely a benign or malignant lesion was considered to represent a high confidence of the observer in the diagnosis. RESULTS: Of 98 breasts evaluated with the standard method, observer confidence was high for 44% of all malignant lesions versus 86% with the combined method. The highest specificity (92%) was achieved by interpretation of the standard method (combined method, 64%). The highest sensitivity (95%) was achieved by interpretation of the combined method (standard method, 83%). Overall accuracy was 87% for the standard method and 83% for the combined method. In separate analyses of nonpalpable and palpable lesions, the combined method achieved an accuracy of 74% for nonpalpable lesions and 88% for palpable lesions. The standard method achieved an accuracy of 85% for nonpalpable lesions and 88% for palpable lesions. CONCLUSION: MR mammography as an adjunct to mammography and sonography reveals breast cancer with a higher confidence and sensitivity than do mammography and sonography only. The combined method can be recommended if the greatest possible sensitivity or negative predictive value is wanted. However, the combined method is not useful for screening or workup of suspicious lesions because of its lower specificity and accuracy.

Breast↗
PubMed1996

Treatment of bile duct stones: value of laser lithotripsy delivered via percutaneous endoscopy.

Extraction of stones from the bile ducts via standard endoscopic techniques, a percutaneous transhepatic approach, or a T-tube track can be unsuccessful. We report our preliminary experience with a combination of percutaneous cholangioscopy and dye laser lithotripsy. Flash lamp-excited dye laser (504 nm) lithotripsy delivered by percutaneous cholangioscopy (12 F) was evaluated in 13 patients with stones in the bile ducts. Conventional endoscopic treatment had not been attempted in 4 patients after hepaticojejunostomy and had failed in 3 patients after gastric bypass surgery or gastrectomy, and in 6 patients because of technical difficulties, i.e. due mainly to largeness of stones. In 12 patients a percutaneous transhepatic route was used. In 1 patient the T-tube track was used as access to the bile ducts. Laser lithotripsy resulted in successful fragmentation of stones in 12 patients (92%). The bile ducts cleared spontaneously in 2 patients only. Using additional techniques, i.e. sphincterotomy and stent insertion, the overall combined success rate for duct clearance after laser fragmentation was 100%. Four patients had a retrograde endoscopic sphincterotomy after failed attempts for stone removal at endoscopic retrograde cholangioscopy. Two patients had an antegrade fluoroscopically monitored sphincterotomy. Bleeding complications occurred in 2 patients. This accounted for a high rate (15%) of severe complications. The intrahepatic bleeding in 1 patient was due to an intrahepatic vessel injury by the 13-F sheath. The periampullary bleeding in the other patient occurred after an antegrade papillotomy. Pulsed dye laser lithotripsy proved to be an effective technique in patients with difficult bile duct stones. The main problem of a per cutaneous approach is the complete removal of the fragmented stones, which requires additional procedures in most cases. The percutaneous access is time-consuming and bears a relatively high risk of major bleeding complications. It should therefore be restricted to cases in which conventional endoscopic procedures are impossible or unsuccessful.

Adult↗
PubMed1996

Assessment of the composition of bone marrow prior to and following autologous BMT and PBSCT by magnetic resonance.

Lumbar bone marrow was assessed by means of magnetic resonance (MR) in 23 examinations of eight patients who underwent autologous bone marrow transplantation (ABMT) or peripheral blood stem cell transplantation (PBSCT). Various imaging and spectroscopic techniques were applied for measurements carried out prior to conditioning for ABMT/PBSCT and in the course of reconstitution and correlated with clinical and blood chemistry data in these patients. The signal intensity from lumbar bone marrow was determined in T1-weighted and water- and fat-selective MR images. The distribution of the magnetic field was demonstrated by a field-mapping method. Localized proton spectroscopy was performed from volume elements of 2 ml located in the central region of vertebral bodies in order to evaluate the fraction of the water signals, the transverse relaxation times T2 of the signals from water and lipids, and the line widths of the spectral signals. Regions of bone marrow after inflammatory conditions or intensive irradiation are shown to be not involved in marrow reconstitution. Additional information about marrow composition was obtained by the magnetic field mapping and by the line widths in the spectra. Considerable alterations of the amount of paramagnetic hemosiderin were revealed following transplantation. Patients with low water signal and strong local inhomogeneities of the magnetic field in the marrow prior to transplantation had a delayed hematopoietic reconstitution compared with the patients lacking these MR features.

Adult↗
PubMed1996

Covered stents for prevention of restenosis. Experimental and clinical results with different stent designs.

RATIONALE AND OBJECTIVES: Metallic stents in small vessels go along with a significant risk of restenosis and reocclusion. Different models of stents and covering materials have been purported to prevent intraluminal neointimal proliferation by cover-based closure of the spaces in the wire mesh. METHODS: Tantalum stents covered with polyethylacrylate/polymethylmethacrylate (PEM) were implanted in the infrarenal aorta of six New Zealand white rabbits by aortotomy and compared with eight rabbits treated with uncovered tantalum stents. For deployment, covered and uncovered stents necessitated a 7-French (F) and 5-F sheath, respectively. In addition, nine human patients with arteriosclerotic lesions of the superficial femoral arteries (stenosis > 5 cm or total occlusion) were treated percutaneously with a Dacron-covered nitinol vascular stent via a 9-F sheath. Patients were followed for a mean of 13.5 months, and control angiography was performed after 6 months. RESULTS: Experimental placement of the tantalum Wiktor stent was feasible technically in all cases. Five of six stents covered with PEM were occluded 3 days after placement despite the intravenous use of heparin and aspirin. In the group with uncovered stents, no area of stenosis greater than 10% was observed. There was a neointimal layer of 89 +/- 68 microns around the stent wires. Stent placement was successful in all patients. In four patients, a hyperergic reaction occurred, resulting in noninfectious periarteriitis. This complication was treated successfully with nonsteroidal antiinflammatory drugs. The primary patency was 50%, and the secondary patency (after application of a second covered stent in two patients) was 63%. CONCLUSIONS: The uncovered stent induces little neointimal proliferation around the stent wires. The insertion of stents covered with PEM into the rabbit aorta was accompanied by a strong thrombotic reaction, despite sufficient anticoagulation. Dacron-covered nitinol stents showed a surprisingly high restenosis rate after 9 months of follow-up. Further research concerning the in vivo properties of new covering materials is mandatory before routine vascular clinical application.

Aged↗
PubMed1996

Evaluation of K-space segmented cine sequences for fast functional cardiac imaging.

RATIONALE AND OBJECTIVES: In functional cardiac magnetic resonance imaging, reduction of measuring time is very important for many patients who are not able to rest motionless for long-lasting examinations. In this study, the image quality of sequences with k-space segmented data recording was compared with conventional gradient-echo sequences for cine imaging with flow compensation in applications on patients with normal and reduced ejection fractions. METHODS: Thirty-one subjects (4 volunteers and 27 patients with cardiac diseases) were examined using different techniques for cine imaging of the left and right ventricles. The ejection fraction in the patients was calculated based on images of a conventional two-dimensional gradient-echo technique using a biplane ellipsoid model. The results from k-space segmented methods (3 to 9 Fourier lines per cardiac cycle for each phase image) were compared with the conventional images of the same short-axis view separately for groups of subjects with normal and reduced ejection fraction. The contrast between blood and myocardium at several sites of the heart and the homogeneity of the blood signal in the ventricle were evaluated for several phases of the heart cycle. RESULTS: The segmentation in the acquisition of raw data allows reduction of measuring time to approximately 20% to 40% of the time required for conventional sequences in cine imaging of the heart. In patients with normal or only slightly reduced heart function (ejection fraction > or = 60%) the image quality of k-space segmented sequences was not significantly different from the conventionally recorded images. In contrast, patients with markedly lowered ejection fraction (< 60%) showed degraded results of the k-space segmented sequences compared with the conventional sequence (P < 0.001). The anterolateral border and the right ventricle especially were not sufficiently delineated by the k-space segmented sequences in these patients. CONCLUSION: The k-space segmentation for the reduction of examination time is suitable for measuring heart volumes and functional parameters of patients expected to have a nearly normal ejection fraction, whereas for patients with markedly reduced cardiac function further technical improvements of segmented techniques are necessary.

Adult↗
PubMed1996

Prospective study of the proctographic and functional consequences of transanal endoscopic microsurgery.

A prospective study of clinical, manometric and proctographic results in 36 patients presenting for transanal endoscopic microsurgery was performed. Anorectal manometry showed no difference in maximal squeeze pressure before and 12 months after operation, but resting pressures were lower after surgery (mean(s.e.m.) preoperative 86.1(27.6) mmHg versus postoperative 67.2(23.2) mmHg, P < 0.05). The rectoanal inhibitory reflex was lost in a significant group of patients (reflex present in 34 of 36 patients before operation and in 27 of 36 12 months after operation, P < 0.05). Proctography, manometry and questionnaire showed preserved function of most modalities 12 months after operation such that if objective function was impaired clinical function was adequate.

Adult↗
PubMed1996

Ablation characteristics of arterial vessel walls irradiated with the pulsed dye laser--an analysis of variance.

BACKGROUND AND OBJECTIVE: Since most clinical laser angioplasties require the use of over-the-wire delivery systems, we studied the effects of pulsed dye laser energy (504 nm, 1.4 microseconds on arterial vessel walls in combination with a multifiber catheter system. MATERIAL AND METHODS: Postmortem arterial segments (n = 368) were exposed under blood or saline. Laser pulses (n = 100-800) were transmitted via 9F-multifiber-catheters, at energy densities of 3-16 J/cm2. Ablation characteristics revealed by histologic examination and morphometry were analyzed by multiple analysis of variance. RESULTS: Ablation occurred more frequently in saline compared to blood. Below an energy density of 10 J/cm2 ablation occurred in saline only. Specimens irradiated under blood showed only thermal changes at 10 J/cm2. In saline, 92% of normal, 88% of fibro-fatty and 60% of calcified tissue showed ablation at 13 J/cm2. The average ablation threshold in saline was about 3-4 J/cm2 per pulse for normal tissue, 5 J/cm2 for fatty plaques, and 8-9 J/cm2 for calcified plaques. In blood, the average ablation thresholds did not differ significantly between the different stages of arteriosclerosis (12 J/cm2 for normal tissue, 11 J/cm2 for fatty plaque, and 10 J/cm2 for calcified tissue). Carbonization and vacuolization were seen regularly at energy levels > or = 13.4 J/cm2. CONCLUSIONS: Selective ablation of arteriosclerotic tissue with the pulsed dye laser could not be found. Further investigation is needed before an effective ablation of arteriosclerotic arterial tissue can be expected.

Arteries↗