Biomedical subjects

E P Strecker

Publications and source records attributed to E P Strecker.

At least 19 recordsLinked to original sources

PubMed2001

Clinical aspects of quality criteria in digital radiography.

In clinical radiological practice two main questions regarding image quality have to be looked at: Which degree of image quality is needed? and: How can this image quality be objective? Image quality requirements depend on size, density and contrast of the objects of interest and on the clinical question which has to be answered. In comparison to conventional radiography, the digital radiographic techniques offer additional features concerning optimisation of image quality and dose, like a wider dynamic range, digital fluoroscopic techniques and post-processing. Therefore it is necessary to define new quality criteria for these techniques. In the following, typical examples demonstrate the development of the 'Diagnostic Requirements for Digital Radiographic Procedures'. These examinations include projection radiographs with digital luminiscent radiography, fluoroscopic procedures with digital image intensifier radiography and angiographic procedures with digital subtraction angiography. The clinical question of a radiological examination also forms the background to optimisation strategies considering image quality and radiation dose.

European Union↗

PubMed2000

Flexible tantalum stents for the treatment of renovascular hypertension: a 10-year experience.

The aim of this study was to determine long-term success of flexible tantalum stents for the treatment of ostial and truncal renal artery stenosis. Since 1989, flexible tantalum stents (type Strecker) were implanted in 34 patients (36 arteries, 25 ostial lesions, 11 truncal lesions) with uncontrollable renovascular hypertension, 9 of them in association with renal insufficiency. Stents were placed unilaterally in 32 patients, and bilaterally in 2 patients for the treatment of renal artery stenosis. Thirty-five of 36 lesions were atherosclerotic, including 5 recurrencies after previous percutaneous transluminal renal angioplasty (PTRA). One patient had Takayasu arteritis. Stents were implanted after unsuccessful PTRA of 11 truncal and 23 ostial lesions, and as a primary procedure in 2 ostial lesions. Follow-up examinations included blood pressure measurement, determination of serum creatinine level, color duplex sonography, or angiography. The technical success rate was 92%. Technical failure included incorrect stent placement (1 of 36 lesions, 2.8 % ), and stent dislocation (2 of 36 lesions, 5.6 %), and two stents were retrieved percutaneously. In one case of Takayasu arteritis, residual stenosis of 40% was observed. After technically successful stent placement, 77% of patients became normotensive with or without medication. In the remaining patients there was partial improvement with blood pressure between 140 and 180 mmHg. Renal function improved in 76% of patients (completely in 3 of 8, 38%; and partially in 3 of 8, 38%). Primary patency rate including all stented lesions and initial technical failures was 82.4% +/- 6.8 (1 year) and 82.4% +/- 9.2 (3 years). After technically successful stent placement, patency rates were 89.9 +/- 5.6% (1 year), and 89.9 +/- 7.6% (3 years). For ostial lesions, primary patency rate was 87.9 +/- 6.7% (1 year) and 87.9 +/- 9.2% (3 years). Placement of flexible tantalum stents in renal arteries is technically demanding, especially in ostial lesions. Once placed successfully stent patency rate is excellent.

Aged↗

PubMed2000

Current practice of temporary vena cava filter insertion: a multicenter registry.

PURPOSE: To evaluate the current practice of temporary vena cava filter placement and its complications. MATERIALS AND METHODS: A multicenter registry was conducted from May 1995 until May 1997 using a standardized questionnaire. One hundred eighty-eight patients were evaluated. Patient characteristics, filter indications, filter characteristics, and complications were registered. RESULTS: Deep vein thrombosis was proven in 95.2% of the patients. Main filter indication was thrombolysis therapy (53.1%). Average filter time was 5.4 days. An Antheor filter was inserted in 56.4%, a Guenther filter in 26.6%, and a Prolyser filter in 17.%. Transfemoral filter implantation was slightly preferred (54.8%). Four patients died of pulmonary embolism (PE) during filter protection. Major filter problems were filter thrombosis (16%) and filter dislocation (4.8%). When thrombus was found in or at the filter before explantation, additional thrombolysis was performed in 16.7%, additional filter implantation in 10%, and thrombus aspiration in 6.7%; 4.8% of filters were replaced with permanent filters. DISCUSSION: Temporary vena cava filters are placed to prevent PE in a defined patient population. Despite their presence, PEs still occur in a small percentage. Problems of filter thrombosis and dislocation have to be solved. CONCLUSION: The results of this multicenter registry support the need for innovative filter design, as well as a randomized, prospective study.

Adolescent↗

PubMed1999

[Dose-dependent decrease of the rate of restenosis of stents in peripheral vessels with reviparin].

PURPOSE: In clinical prospective trials, we examined the effect of the low molecular weight heparin (lmwh) reviparin on restenosis rate after Strecker stent implantation in femoral popliteal arteries. MATERIALS AND METHODS: 62 patients were treated between 1992 and 1998. Patients received reviparin, 3500 IU, prior to stent implantation followed by 7500 IU for 24 h (i.v.) and 2 x 1750 IU/day s.c. over three weeks (n = 12) or 10,500 IU for 24 h (i.v.) and 2 x 3500 IU/day s.c. over 3 1/2 weeks (n = 50). Follow-up parameters were clinical symptoms, ankle-brachial index, color Doppler flow duplex sonography, and DSA. RESULTS: Three thrombotic occlusions and three stenoses were observed in the low-dose group. Raising the dose resulted in neither thrombotic nor other events within the first three months. Seven stenoses occurred afterwards up to the 7th month. The complication rate was low: one moderate hematoma and one puncture aneurysm. Primary patency rate was 88% and 80% for one and two years, respectively. This is significantly better than the primary patency rates for patients receiving low-dose lmwh (p < 0.005) or unfractionated heparin (p < 0.05). CONCLUSIONS: Hence, high-dose administration of the lmwh reviparin lowers the restenosis rate after stent implantation in femoropopliteal arteries.

Aged↗

PubMed1999

Correlation of hemodynamic and functional variables with the angiographic extent of peripheral arterial occlusive disease.

The aim of the study was to determine whether hemodynamic and functional variables are related to the angiographic extent of lower limb atherosclerosis. In 150 patients with stable intermittent claudication, the Bollinger angiogram score was compared with the resting Doppler pressure values, and the initial claudication distance (ICD) and absolute claudication distance (ACD) with treadmill exercise. The extent of lower limb atherosclerosis correlated significantly with the age of the patients and the duration of the claudication. The angiogram scores of the patients were negatively correlated with the ankle systolic blood pressure (SBP) and the ankle/brachial index (ABI). In a multiple regression analysis, ABI was the most predictive variable for the angiographic severity of disease. ICD, ACD and work on the treadmill failed to correlate with the angiogram summation score. If patients were classified into groups for those with iliac or femoropopliteal disease, a weak correlation between ACD and femoropopliteal angiogram score was found. The comparison between Doppler measurements and treadmill exercise testing showed no significant correlation between SBP/ABI of the more diseased limb and ICD. However, both SBP and ABI did correlate significantly with ACD (r = 0.16, p < 0.05 and r = 0.20, p < 0.01, respectively). In conclusion, SBP and ABI are reliable parameters for indirect assessment of the angiographic extent of lower limb atherosclerosis. In contrast, the walking capacity of claudicant patients is independent of the angiographic severity of the disease.

Age Factors↗

PubMed1998

[Clinical aspects of image quality and doses in gated pulsed imaging].

PURPOSE: The relations between image quality in last image hold images and dose in grid controlled fluoroscopy in comparison to the continuous mode need to be characterised and recommendations for the clinical application of this technique should be given. MATERIAL AND METHODS: Spatial resolution, signal-noise ratio and, contrast-detail visibility were evaluated by phantom measurements in grid controlled pulsed and continuous fluoroscopy. Dose was measured at the image intensifier entrance. Image quality of last image hold (LIH) images of clinical examinations was graded in relation to single shot exposures. RESULTS: Signal-noise ratio and contrast-detail visibility depend on the dose per puls. Spatial resolution and contrast-detail visibility in grid controlled fluoroscopy are superior than to in the continuous mode. Image quality of the LIH images from the grid controlled fluoroscopy was improved. Radiation exposure could be reduced to 10-46%. CONCLUSIONS: Combinations of puls-dose and -frequency are recommended for achieving extensive dose reduction and improved image quality of LIH images.

Diagnostic Imaging↗

PubMed1997

Percutaneously implantable catheter-port system: preliminary technical results.

The function and safety of a percutaneously implantable catheter-port system were studied in 44 patients with different diseases (32 patients with malignant disease, 11 with peripheral arterial disease, and one with recurrent asthmatic attacks). Most patients required repeated local-regional arterial infusion. Infection (two patients) and catheter-related complications (10 patients) were observed during the follow-up period (maximum length of follow-up, 542 days; mean, 177 days). Port migration or leakage did not occur. The data suggest that this new catheter-port system is safe and easy to handle.

Adolescent↗

PubMed1997

Femoropopliteal artery stent placement: evaluation of long-term success.

PURPOSE: To evaluate the long-term success of femoropopliteal artery stent placement after technical failure of balloon angioplasty and to determine potential factors predictive of stent failure. MATERIALS AND METHODS: In 80 patients, flexible tantalum stents were implanted for treatment of residual stenosis greater than 30% after balloon angioplasty of femoropopliteal artery stenoses (n = 33) or occlusions (n = 47). Follow-up examinations were performed at 1-72 months to evaluate early and late stent failure according to risk factors such as lesion type, anatomic location, stent length, runoff quality, and restenosis after balloon angioplasty. RESULTS: Early stent thrombosis occurred within 10 days after stent placement in four (5%) patients; the frequency was higher (P < .01) in stents longer than 4 cm (14%) versus that in stents 4 cm or shorter (2%). For all stents, the 2-year primary patency rate was 51% and the 3-year rate was 48%. The 2-year primary patency rate was significantly better (P < .05) for shorter stents (59%) versus that for longer stents (30%) and for treated stenoses (73%) versus treated occlusions (33%). Multivariate analysis revealed that lesion type and lesion length were the most reliable factors predictive of stent failure. CONCLUSION: Successful stent therapy does not seem to depend on the type of stent used but rather on lesion type, lesion length, and other predisposing factors.

Adult↗

PubMed1997

[Studies of image quality and dose in digital subtraction angiography].

METHODS: The dose needed for high image quality in l.a. DSA, was determined by investigation of the necessary relationship between dose and image quality. This method is based on measurements of the signal-to-noise ratio and of the contrast-detail detectability. It has been tested on two different systems (Philips integris V3000, Philips Diagnost 97). RESULTS: Our measurements prove that an image intensifier entrance dose of 1.1 microGy (image intensifier diameter 38 cm) is sufficient for high image quality in DSA. An increased dose value does not lead to an improvement in image information. For details larger than the pixel size the 512 matrix produces a higher signal-to-noise ratio with a higher contrast-detail detectability, whereas higher spatial resolution results by the use of a 1024 matrix. In rotational angiography, high image quality can be achieved at an image intensifier entrance dose of 1.1 microGy. In contrast to sequences without rotation, image quality is decreased through movement unsharpness. As the maximum exposure time 25 ms should be selected. The use of a 1024 matrix does not lead to a better spatial resolution in rotational angiography.

Angiography, Digital Subtraction↗

PubMed1996

Flexible tantalum stents for the treatment of iliac artery lesions: long-term patency, complications, and risk factors.

PURPOSE: To evaluate the long-term success of tantalum stents implanted in iliac artery lesions and to determine potential predictive factors of early and late stent failure. MATERIALS AND METHODS: In 289 patients, flexible tantalum stents were implanted in iliac artery stenoses (n - 223) or occlusions (n - 66). Early and late stent failures were evaluated at 1-79 months (mean, 23 months). Four risk factors were evaluated: lesion type (occlusion vs stenosis), lesion location (common vs external iliac artery), lesion length (< 4 vs > 4 cm), and quality of runoff (good vs poor). RESULTS: The frequency of early stent thrombosis was significantly (P < .001) higher in occlusions (15.2%) versus stenoses (2.7%), in external (12.8%) versus common (1.1%) iliac arteries, in long (16.7%) versus short (0.5%) lesions, and in poor (14.0%) versus good (2.1%) runoff. At multivariate analysis, runoff and location were influencing factors. Primary patency rates at 3 and 5 years were 85% and 70%, respectively, for all stents. Three-year patency rates were significantly higher in short (88%) versus long (63%) lesions and in stenoses (92%) versus occlusions (63%). At multivariate analysis, lesion length was the only predictive factor for 3-year stent patency. CONCLUSION: Stent implantation offers valuable long-term treatment for atherosclerotic iliac artery disease. Success can be predicted on the basis of risk factors.

Adult↗

PubMed1995

Malignant duodenal stenosis: palliation with peroral implantation of a self-expanding nitinol stent.

The authors implanted a duodenal stent in a woman with a high-grade duodenal stenosis due to inoperable tumor compression. A flexible self-expanding knitted nitinol stent that conformed to the shape of the duodenum was introduced orally to keep the duodenal passage patent. After stent implantation, repeated vomiting stopped and the patient was able to eat and drink. This technique resolved the patient's duodenal stenosis.

Adenocarcinoma↗

PubMed1994

Current status of the Strecker stent.

Knitted flexible tantalum stents proved to be a valuable adjunct to percutaneous transluminal angiplasty (PTA) in the case of insufficient PTA results, and their use was established in the distal aorta, the iliac, the femoro-popliteal, the renal, and the coronary arteries. Recently, long arterial occlusions were defined as new indications for primary stenting; stent indications were further extended to the subclavian, the carotid, and the splanchnic arteries. Due to higher incidence of acute and late complications after stent treatment of small diameter arteries, patients have to be selected thoroughly. Newly designed drug-releasing stents tested in animal experiments promised to be suitable to diminish the incidence of late restenosis due to intinal hyperplasia, thus providing better long-term patency.

Angioplasty, Balloon↗

PubMed1990

[A new non-surgically implantable catheter port system for locoregional chemotherapy of advanced bladder cancer].

A new method to treat advanced urinary bladder cancer with locoregional chemotherapy has been developed which can be implanted by the radiologist. So far 3 patients with urinary bladder cancer invading the surrounding anatomical structures were treated. A 5F catheter is introduced into the internal iliac artery by the translumbar approach. Then, this catheter is exchanged with a coaxially assembled catheter port system over a guide wire. A subcutaneous tunnel through the puncture site is formed to receive the port. 10 mg mitomycin were infused three times at intervals of one to three weeks. Computed tomograms and cytoscopy showed complete disappearance of the tumour.

Aged↗

PubMed1990

Flexible tantalum stents implanted in aortas and iliac arteries: effects in normal canines.

Vascular endoprostheses made of knitted tantalum wire and expanded over angioplasty balloons were placed into aortas or iliac arteries of 14 normal dogs. Twelve stents were placed into the infrarenal abdominal aorta and two stents in the left common iliac arteries by the left carotid artery approach. To firmly expand the stent against the vascular wall, nominal stent sizes 0.5-1.0 mm larger than the measured arterial diameter were required. Arteriography performed at specified follow-up intervals showed no evidence of thrombi or emboli; all side branches (lumbar arteries) covered by the stents remained patent. Vascular diameter decreased minimally at 8 and 26 weeks, associated with histopathologic evidence of neointimal buildup. This buildup was highest at 8 weeks (mean, 313 microns) and was slightly less at 26 weeks (mean, 223 microns). Almost complete coverage by endothelium was seen as early as 3 weeks. It is concluded that the flexible tantalum wire stents are well tolerated by the arterial wall and become quickly endothelialized. No excessive neointimal buildup was observed during the 6-month study.

Animals↗

PubMed1990

Expandable tubular stents for treatment of arterial occlusive diseases: experimental and clinical results. Work in progress.

The balloon-expandable vascular prosthesis consists of a flexible, knitted tantalum wire mesh tube. To demonstrate its pliability, this prosthesis was tested experimentally in 10 mongrel dogs by implanting it into the proximal femoral arteries. The maximum follow-up time was 1 year. On the basis of the experimental results, in which there was no relevant stenosis, occlusion, or migration of the vascular prosthesis, nine patients were treated: one with iliac artery occlusive disease and eight with superficial femoral artery (SFA) occlusive disease (four reocclusions after angioplasty and four unsatisfactory primary angioplasty results). One SFA lesion was treated with the crossover method from the contralateral side. All implants remained patent without hemodynamically significant stenoses, with the longest observation time being 6 months. Flexible, expandable vascular prostheses are promising adjuncts to angioplasty.

Aged↗

PubMed1989

Tantalum vascular stents: in vivo evaluation with MR imaging.

Magnetic resonance (MR) imaging at 1.5 T was performed on tantalum vascular stents placed in the aortas of six dogs. The stents produced no significant artifact and allowed for clear depiction of the aortic lumina as flow-void zones with spin-echo imaging and as high-signal areas with gradient-echo imaging. The MR findings correlated with the angiographic studies of the stented vessels. These results demonstrate the feasibility of MR imaging as a noninvasive means of evaluating vessel patency in the presence of tantalum vascular stents.

Animals↗

PubMed1989

Influence of an ionic and a nonionic (sodium meglumine diatrizoate and iopromide) x-ray contrast medium of hemorrheology.

In two groups of ten patients each, an ionic and a nonionic contrast medium was injected intravenously, for digital subtraction angiography of the supra-aortic branches, to examine the influence of hemorrheologic properties. Afterward, blood samples were obtained through a central venous catheter and evaluated by a new instrument (oscillating capillary rheometer and densitometer). The viscous and elastic components of the complex blood viscosity and the hematocrit decreased after injection of ionic and nonionic contrast media. A statistically significant difference between the patient groups could not be found. The evaluated results describe an improvement of the hemorrheologic properties after contrast media injection.

Angiography↗

PubMed1988

[Percutaneously implantable balloon-inflatable vascular prostheses. Initial clinical results].

Restenosis and occlusion of atherosclerotic arteries are prevented by a newly developed arterial prosthesis consisting of a pliable and elastic wire mesh tube positioned to the balloon of an angioplasty catheter. As the balloon is inflated the prosthesis dilates and provides the arterial wall with a new mechanical support. This new device was successfully implanted in ten patients having an iliac artery stenosis and improved the therapeutic result of the preceding angioplasty. There were no complications.

Aged↗