Biomedical subjects

S Duda

Publications and source records attributed to S Duda.

At least 19 recordsLinked to original sources

PubMed2000

MR imaging in the presence of vascular stents: A systematic assessment of artifacts for various stent orientations, sequence types, and field strengths.

A systematic evaluation of the potential quality of magnetic resonance images recorded in the presence of metallic stents was performed on a low-field open imager operating at 0.2 T and on a high-field closed unit operating at 1.0 T. Eight different stent types were examined by two-dimensional gradient-echo sequences with echo times of 4 and 10 msec and by a fast spin-echo technique. In addition, a three-dimensional gradient-echo sequence was applied with an echo time of 2.4 msec. A set of sequence and slice parameters was used on both scanners. Thus, artifacts due to susceptibility effects depending on the magnetic field strength could be distinguished from radiofrequency shielding effects in the lumen of the stents (independent of the field strength). Nine different orthogonal orientations of the stent axis and the image (in terms of slice, read, and phase-encoding direction) were tested, and the artifacts (extension of signal void and visibility of the lumen) were compared. The optimal strategy for visualization of vascular and perivascular regions outside the stents was fast spin-echo imaging with the stent axis and read direction parallel to the static field. Susceptibility-induced signal void in gradient-echo images was minimal using the three-dimensional approach. Increased transmitter amplitudes above usual values provided clearly improved insight in the lumen using gradient-echo sequences.

Alloys↗

PubMed1999

Renal MR angiography at 1.0 T: three-dimensional (3D) phase-contrast techniques versus gadolinium-enhanced 3D fast low-angle shot breath-hold imaging.

OBJECTIVE: The purpose of this study was to evaluate the diagnostic usefulness of three different MR angiographic techniques at 1.0 T. SUBJECTS AND METHODS: In 22 patients with renal artery stenosis confirmed at intraarterial catheter angiography, we also performed unenhanced and gadolinium-enhanced three-dimensional phase-contrast MR angiography and gadolinium-enhanced single breath-hold three-dimensional fast low-angle shot MR angiography. We determined circulation time to optimize signal acquisition in gadolinium-enhanced breath-hold MR angiography after bolus injection of contrast material. RESULTS: Sensitivity, defined as the detection of a hemodynamically significant stenosis (>50% luminal narrowing), was 85% for enhanced phase-contrast MR angiography, 91% for gadolinium-enhanced MR angiography, and 95% for unenhanced phase-contrast MR angiography. The combination of unenhanced phase-contrast MR angiography and gadolinium-enhanced MR angiography yielded 100% sensitivity for hilar artery stenoses. There were 13 false-positive findings with unenhanced phase-contrast MR angiography, 10 with enhanced phase-contrast MR angiography, and four with gadolinium-enhanced MR angiography (specificity: 38%, 52%, and 79%, respectively). Accessory renal arteries were not seen on unenhanced or enhanced phase-contrast MR angiography (0/8 patients) but were detected with gadolinium-enhanced MR angiography in five of the eight patients. Interobserver agreement (kappa = .62) was best with gadolinium-enhanced MR angiography. The quality of the images was unsatisfactory for adequate evaluation of segmental renal arteries with all three MR angiographic techniques. CONCLUSION: A combination of unenhanced phase-contrast MR angiography and gadolinium-enhanced MR angiography at 1.0 T proved useful as a screening protocol for renal artery stenosis.

Adult↗

PubMed1999

[Pneumothorax in cigarette smokers].

From 1.01.1992 to 31.12.1998 ill prisoners were treated because of so called spontaneous pneumothorax. Their age was between 24 to 57, which was 33 in average. All of them were males and heavy smokers. In one case of the coat pneumothorax the treatment was limited only to the breathing exercises, to ten other patients an under-water-seal drainage was applied, in the next case with pneumothorax and clear symptoms of bronchial fistula, the lung expansion was obtained no sooner than after the usage of a suction drainage. The risk of recurrence of the illness was limited by injection of 40% glucose solution through the drain to the pleural cavity to increase adhesions.

Adult↗

PubMed1998

[Color duplex ultrasound of the finger arteries. An alternative to angiography?].

By means of modern color-coded duplex sonography (CCDS) even very small vessels can be visualized. Maximum resolution nowadays is about 0.5 mm diameter of the vessel. We compared the use of CCDS and angiography in studying of acral perfusion. Besides morphologic criteria, hemodynamic criteria were recorded. Arteries in healthy fingers appear as long and straight vessels with a clearly defined border. The physiological maximal blood flow velocity exceeded 20 cm/s. CCDS revealed tortuosity of finger arteries as typical finding in thrombangiitis obliterans. Segmental stenosis can either be identified morphologically or quantified by measurement of the flow velocity with poststenotic maximal systolic velocities of less than 20 cm/s or by the acceleration of the blood flow within the stenosis, as proven by angiographic examinations. CCDS is suitable for evaluation of acral perfusion in patients suffering from secondary Raynaud's syndrome. Apart from diagnosis of disturbed acral circulation, other possible applications of CCDS are in in the surgical field, for example replantations in hand or finger surgery.

Adult↗

PubMed1997

Perspectives of coronary excimer laser angioplasty: multiplexing, saline flushing, and acoustic ablation control.

BACKGROUND AND OBJECTIVE: Bubble formation, pressure wave generation, and cavitations constitute major factors influencing the outcome of clinical Excimer laser angioplasty. Thus, the rationale of this study was to determine the extent of pressure waves occurring during excimer laser ablation and to discuss possibilities that allow a less traumatic plaque removal in the coronary circulation. STUDY DESIGN/MATERIALS AND METHODS: Conventional and experimental Xenon-Chlorid-Excimer lasers emitting light at a wave-length of 308 nm and a pulse duration of 115 ns were used for testing of signals. Whereas the conventional excimer laser light source transmits light through all fibers of a 1.7 mm laser catheter simultaneously, the prototype excimer laser divides the laser beam into several areas of uniform energy fluence by scanning the beam from one section to the other using the intermission between two laser discharges. Hydrophones consisting of piezoelectric films detected the acoustic signals, which were obtained on normal arterial wall and atherosclerotic plaque. RESULTS: Multiplexing decreases maximum pressures for both normal arterial wall and calcified plaque significantly, whereas pressure rise time remains comparable. During ablation of pure blood, a linear increase of peak pressures of 1 MPa at 10 mJ/mm2 to 7.5 MPa at 50 mJ/mm2 is found. Contrast media intensifies the extent of pressure wave formation. At 20 mJ/mm2, 60% contrast media added to blood results in an increase of maximum pressures from 1.5 MPa up to 5 MPa. Dilution with saline solution is effective; however, high concentrations of > 90% are required to achieve a significant pressure wave reduction. CONCLUSION: Peak pressures of several thousand kPa occur during excimer laser ablation of contrast media, blood, calcified plaque, and normal arterial wall in a decreasing order. Multiplexing and saline flushing are capable of reducing the intensity of the generated acoustic signals during tissue ablation. It has to be taken into consideration, however, that high concentrations of saline solution are necessary to achieve a significant reduction of peak pressures.

Acoustics↗

PubMed1997

Multiplex PCR for simultaneous detection of the most frequent T cell receptor-delta gene rearrangements in childhood ALL.

A rapid and simple multiplex polymerase chain reaction (PCR) is described that is capable of identifying the six most frequent rearrangements of the T cell receptor (TCR)-delta gene segments in childhood acute lymphoblastic leukemia (ALL). The PCR products amplified in a single reaction are of different size for each TCR-delta gene rearrangement. Therefore, they are readily and unambiguously distinguished after agarose gel electrophoresis and assigned to a specific V-D-J gene rearrangement. There is no need for labor-intensive and time-consuming Southern blot hybridization or nested PCR. To evaluate the multiplex assay we chose 45 DNA samples of childhood ALL analyzed beforehand for TCR-delta gene rearrangements by Southern blot and single PCR of which 30 showed TCR-delta gene rearrangements. The multiplex PCR results corresponded to the Southern blot and single PCR analyses. The described multiplex PCR enables the detection of clonal markers in about 50% of patients in order to monitor minimal residual disease (MRD) in prospective studies with a high turnover of samples.

Blotting, Southern↗

PubMed1996

[The popliteal artery entrapment syndrome in an older patient. Its diagnosis after unsuccessful laser-assisted percutaneous transluminal angioplasty].

HISTORY AND FINDINGS: A 52-year-old patient complained of progressively increasing pain in his left leg when walking. The pain-free walking distance was 50-100 m. He was smoking about 20 cigarettes daily. No pulses were palpable in the left leg below the inguinal fossa. Recapillarisation time was normal in both legs and there were no trophic changes. INVESTIGATIONS: The Doppler perfusion pressure values were up to 40 mm Hg less in the left than the right leg. Ankle oscillography record showed a definite stenosis curve on the left. Digital subtraction angiography of the left leg showed a short occlusion of the popliteal artery with many collaterals and atypical medical deviation of the artery. The findings were interpreted as indicating peripheral arterial vascular disease. TREATMENT AND COURSE: Laser-assisted percutaneous transluminal angioplasty with balloon dilatation merely achieved a narrow lumen which again closed on plantar flexion of the left foot. The reversible occlusion suggested popliteal artery entrapment. At operation the popliteal artery coursed atypically over the dorsal medial aspect of the medial head of the gastrocnemius muscle. The arterial segment in the stenotic area was replaced by an autologous venous graft and the gastrocnemius muscle fixed laterally. The patients no longer experienced any impairment on walking and repeat angiography showed unimpeded flow through the graft even on plantar flexion. CONCLUSION: Popliteal artery entrapment is rare in the elderly and may be overlooked without provocation test and complete visualisation of the leg and pelvic arteries.

Angiography, Digital Subtraction↗

PubMed1996

[Hypothenar hammer syndrome as a rare cause of Raynaud syndrome].

A 25-year-old carpenter with severe localised Raynaud syndrome of the lateral three fingers of his right hand is described. The patient reported digital ischaemia caused by cold or vibration, and especially when both were present simultaneously. He was initially diagnosed with thrombangitis obliterans, but failed to respond to intravenous prostaglandin therapy, pentoxifyllin or aspirin. Diagnostic procedures performed in our hospital, especially angiography, confirmed our suspicion of hypothenar hammer syndrome. Radiological examination revealed severe anatomical and functional changes of the distal ulnar artery and, digital arteries of the affected digits. The differential diagnosis of Raynaud syndrome should include the hypothenar hammer syndrome as a possible cause. Early diagnosis and prevention of hand trauma is the only possible way to stop progression of this disease, which leads to invalidity.

Adult↗

PubMed1996

[Foreign bodies in the digestive tract].

In the past two years time 128 patients-prisoners, who had swallowed foreign bodies, have been observed. Six anchors and crosses, which had been stuck in the esophagus, were immediately and successfully removed endoscopically. Long rods and crosses (60 cases) situated mostly in the stomach or descending part of the duodenum were operated without any complications. A few weeks delay of operation caused the covered perforation of the alimentary tract wall nearly 20% of cases and one of which died. Ingested small foreign bodies (less than 10 cm in length) are harmless, pass spontaneously through the gastrointestinal tract and don't need any surgical intervention. In a few cases those small foreign bodies perforated the guts, covered outside the digestive tract without any complaints.

Digestive System↗

PubMed1995

[Inadvertant suture fixation of a Swan-Ganz catheter to the pulmonary artery following heart surgery].

We report a patient undergoing redo cardiac surgery for combined replacement of the aortic and mitral valves. During the course of the operation, a Swan-Ganz catheter - positioned preoperatively - was accidentally fixed to the wall of the pulmonary artery. As this did not interfere with cardiac output measurement or the pulmonary artery pressure wave form, the fixation was not noticed until an attempt was made to remove the catheter. Fluoroscopy revealed both the catheter's immobility and the location of the suture fixation. The patient required a sternotomy to remove the catheter. In order to avoid this complication, the indications for pulmonary artery catheters during cardiac surgery should be carefully considered. If catheters are inserted, their mobility should by all means be ensured before the chest is closed.

Aged↗

PubMed1994

Eosinophilia-myalgia syndrome: findings at MR imaging and proton spectroscopy of the lower leg.

Five magnetic resonance (MR) studies of the lower leg were performed in three patients with eosinophilia-myalgia syndrome (EMS). The 1H spectroscopic and imaging findings were compared with seven examinations of age-matched healthy controls. Standard imaging with proton density-, T1-, and T2-weighted spin-echo (SE) sequences at 1.5 T showed marked atrophy of the calf muscles and slightly increased signal strength of muscle tissue in T2-weighted SE images. The application of frequency selective chemical shift imaging (SENEX) exhibited skin changes similar to those of scleroderma with increased water content and thickened cutis in the water selective images. In one patient the tibialis muscles showed irregular structures, but no fatty degeneration as demonstrated in the fat selective images. Proton signals from volume elements of (20 mm)3 within the soleus and gastrocnemius muscle were recorded by the PRESS localization method. A reduction of the creatine/water and the choline/water ratios was found in the 1H spectra from the EMS patients compared to the controls. Localized 1H spectroscopy exhibited modified distributions of the lipid signals in two EMS patients with slightly elevated signals from unsaturated fatty acids. The transverse relaxation of choline and creatine signals was accelerated in both examinations of one patient compared with the healthy controls.

Adult↗

PubMed1993

Occurrence, extent, and implications of pressure waves during excimer laser ablation of normal arterial wall and atherosclerotic plaque.

Ablation of atherosclerotic plaque and normal arterial wall was performed using a Xenon-Chloride Excimer laser with a wave-length of 308 nm and a pulse duration of 115 ns. The light was transmitted via a 600 microns bare fibre and adjusted to an energy density of 3.5J/cm2. The acoustic signals generated by the laser pulse were measured with two types of hydrophones consisting of polyvinylidenefluoride with active diameters of 0.3 mm and 0.5 mm and recorded on a dual channel digital storage oscilloscope using either a 0.5 m coaxial cable or a broadband fibre-optic transmission system. Tissue was retrieved from nine cadaver human aortas and macroscopically classified as either normal or calcified atherosclerotic plaque. Histological analysis (Haematoxylin eosin, elastica van Gieson, and immunohistochemical staining) was carried out after the experiments to verify the macroscopic diagnosis and to correlate the acoustic responses with the tissue characteristics. For normal arterial wall, maximum peak pressure was 1.28 MPa +/- 0.85 MPa, rise time 163 ns +/- 43 ns, and pressure increase 8.2k Pa +/- 5.4k Pa/ns. For calcified, atheromatous segments, a maximum peak pressure of 2.02 MPa +/- 1.16 MPa, a rise time of 69.9 ns +/- 25.8 ns, and a pressure increase of 32.3 kPa +/- 21.3 kPa/ns was found. Statistical analysis showed a significant shorter rise time (P < 0.0001) and a higher pressure increase (P < 0.0001) for calcified tissue in comparison to normal arterial wall, whereas maximum pressures alone did not allow a differentiation of tissue characteristics. Several hundred kPa are generated during Excimer laser ablation.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustics↗

PubMed1993

Leukemic red bone marrow changes assessed by magnetic resonance imaging and localized 1H spectroscopy.

Red bone marrow of healthy persons has considerable contents of water and lipids. The cellularity and the corresponding fat-water ratio within the marrow show clear changes in hematological diseases. Magnetic resonance (MR) methods use the signals of the protons of water and lipids. This paper gives a comparison between different standard MR techniques and recently developed fat- and water-selective imaging methods, addressing their sensitivity to bone marrow changes in leukemia. Additionally, 1H results of spectroscopic methods are presented. The results and conclusions are based on the examination of 26 healthy volunteers and 106 patients with general or focal bone marrow alterations. Standard T1-weighted images did not distinguish bone marrow of young healthy volunteers with relatively high cellularity from acute leukemia. Using fat- and water-selective methods, patients with untreated leukemia showed only water proton signals and no lipid signals from red bone marrow of vertebral bodies and the pelvis. This phenomenon was never observed in healthy volunteers. Following chemotherapy, lipid and water contents normalize in successfully treated patients. Nonresponders did not show significant changes of the fat-water ratio after up to 3 weeks of therapy. Phase contrast imaging provides information about the difference between fat and water fractions within the bone marrow, but quantitative determination of the absolute fat and water fractions requires acquisition of several images and suffers from the susceptibility effects in trabecular bone marrow. The fat-water ratio and additional qualities of water and lipid protons (relaxation times) can be evaluated by volume-selective MR spectroscopy. Typical results of spectra from small-volume elements in hypercellular vertebral bone marrow of leukemic patients before cytotoxic treatment and of normocellular or hypocellular marrow after therapy are demonstrated.

Adolescent↗

PubMed1993

[Special MR methods for primary bone tumors: I. Chemical shift selective imaging].

The value of selective imaging of fat and water compared with proton density, T1- and T2- weighted MR sequences was studied in the course of 32 examinations on 22 primary bone tumours in various parts of the body. Fat selective images showed practically signal free areas for osteogenic tumours which could be distinguished from surrounding fat containing soft tissues. Water selective images improved definition of the tumour margin from oedema in the bone marrow. Chemical shift artefacts are avoided by these methods and therefore fat and water selective images provide better spatial resolution for identical pixel sizes.

Adolescent↗

PubMed1993

[Special MR methods for primary bone tumors: II. Volume selective 1H-spectroscopy].

The method of localised 1H MR spectroscopy was used in 19 examinations in 9 patients with primary bone tumours in order to obtain spectral signals and to determine whether these are specific for tumour classification. The spectra were obtained by a double spin echo method and the tumour tissue showed very high water content and only minor lipid and proton signals which showed J-coupling characteristics. The latter are not found in normal bone marrow and are probably due to products of tumour metabolism. The resolution of the spectra within a 13 mm or 20 mm tissue cube depends largely on the structural homogeneity of the tumour. The signal patterns in the spectra were not specific to histological tumour types.

Adolescent↗

PubMed1992

[Magnetic resonance tomography: value and limits in gastroenterologic diagnosis].

At present, the value and limitations of magnetic resonance imaging (MRI) as a diagnostic modality in gastroenterology cannot be conclusively determined. MRI has a high sensitivity in the detection of focal liver lesions. The signal intensity of focal liver lesions on plain and contrast-enhanced T1-weighted images and on plain T2-weighted scans narrows the differential diagnosis in many cases. Imaging of the gallbladder and pancreas presently is no indication for MRI. The high sensitivity of MRI in the detection of fistulae and abscesses in Crohn's disease and the differentiation from fibrosis represents an advantage over other modalities in imaging of inflammatory bowel disease. MRI is superior to CT in differentiating recurrent rectal cancer from fibrosis. Further development of MRI and the use of contrast media for both oral and intravenous administration may offer new perspectives of MRI in the diagnosis of diseases in gastroenterology.

Digestive System Diseases↗

PubMed1991

Potential use of holmium lasers for angioplasty: evaluation of a new solid-state laser for ablation of atherosclerotic plaque.

Tissue effects of the mid-IR Holmium laser (emitting at a wave-length of 2130 nm) were evaluated. This wavelength is attractive because it combines high water absorption and easy transmission through standard optical fibres. The laser was pulsed with pulse durations in the range of 100 microseconds and repetition rates between 2 and 6 Hertz. For all experiments a repetition rate of 2 Hertz was used. The laser beam was coupled into waterfree quartz fibers with core diameters of 200 and 800 microns with an efficiency of 70 and 80%, respectively. Ablation of atherosclerotic plaque has been performed at an ablation threshold of 10J/cm2 for the 800 microns and 40J/cm2 for the 200 microns fibre. Removal of calcified plaque was possible. Ablation efficiency increased in a non-linear fashion with increasing pulse energies. The ablation rate per pulse was approximately 2 mm at energy fluences of 1000J/cm2 for the 200 microns fibre and 1.25 mm at energy fluences of 70J/cm2 for the 800 microns fibre; a further increase in energy densities did not result in higher ablation rates. On macroscopic examination only very limited thermal injury was found in crater adjacent tissue structures. Crater edges were even and did not reveal signs of crater charring or debris in the crater lumen. However, the histologic specimens revealed zones of thermal damage extending 100 up to 1000 microns lateral into adjacent tissue. Thermal damage increased with increasing radiant exposures and depended on the medium used.

Angioplasty, Laser↗

PubMed1990

[Experimental intracoronary Excimer laser angioplasty].

To determine the feasibility of intracoronary application of pulsed ultraviolet laser light 38 coronary arteries of 18 in situ hearts were treated with the bare fiber technique and a specially constructed catheter device. Eight hearts had no coronary artery disease, in 10 hearts coronary artery disease of one or more vessels could be documented angiographically. Total time of laser irradiation varied from 30-490 seconds. Radiation was performed until vessel wall perforation was documented. In all cases a reduction of the stenotic area was realized using the bare fiber technique. Due to a lack in the flexibility of the bare fiber only proximal lesions could be treated and the time of perforation could not be precisely predicted. Dissections were observed in six coronary arteries. The handling of the catheter device was comparable to the conventionally used balloon technique. Ablative treatment of distal vessel lesions was possible. Perforations did not occur. The histologic specimens documented smooth lumen margins not revealing thermal damage. It can be expected that the innovative catheter device will enhance the intracoronary use of pulsed laser light.

Angioplasty, Balloon, Coronary↗