Search PubMed⌕ Search

Biomedical subjects

C D Claussen

Publications and source records attributed to C D Claussen.

At least 199 records · Page 11Linked to original sources
PubMed1998

Gd-enhanced 3D phase-contrast MR angiography and dynamic perfusion imaging in the diagnosis of renal artery stenosis.

The objective of this study was to investigate the role of contrast enhancement using a three-dimensional (3D) phase-contrast (PC) magnetic resonance (MR) sequence (3D PC-MRA) and to assess the value of a dynamic MR perfusion study of the kidneys to determine the hemodynamic relevance of unilateral renal artery stenosis (RAS). Seventeen patients with unilateral RAS were examined on a standard 1.0 T imaging system using a phase shift and magnitude sensitive 3D PC sequence (TR=160 ms, TE=9 ms, venc. 30 cm/s). Following the initial pre-contrast 3D PC-MRA a dynamic first pass perfusion study was performed using a Turbo-FLASH 2D sequence (TR=4.5 ms, TE=2.2 ms, TI=400 ms) after bolus injection of 0.15 mmol gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA)/kg body weight. The 3D PC-MRA was then repeated during infusion of 0.15 mmol Gd-DTPA/kg body weight. Evaluation by three independent readers was based on maximum intensity projection images. Source images were rendered on request. Signal intensity (SI) over time curves of the renal cortex were obtained from the dynamic perfusion study and analyzed for maximum signal enhancement as well as temporal relationship to the aortic SI curve. Results from 3D PC-MRA revealed a sensitivity (pre-/post-contrast) of 100%/89%, specificity of 76%/63%, positive predictive value of 80%/69 %, negative predictive value of 90%/78%, and accuracy of 85%/75% (p=0.07). Interobserver agreement was kappa=0.61/kappa=0.47 (pre/post Gd-DTPA), respectively. Increased signal-to-noise was present in all segments of the renal arteries post contrast (p=0.0003). This came along with image degradation due to aliasing and elevated SI of venous flow that partially obscured the renal arteries. Dynamic SI curves showed a significantly decreased maximum SI in RAS (p=0.01-0.001). A temporal delay of cortical signal intensity enhancement could not be confirmed in this setting. Gd-enhanced 3D PC-MRA did not yield a superior diagnostic value in the diagnosis of RAS compared to pre-contrast measurements. Dynamic perfusion imaging of the kidneys, in combination with 3D PC-MRA, can contribute additional information in suspected unilateral RAS.

Aged↗
PubMed1998

[Intra-arterial calcium stimulation for preoperative localization of insuloma].

PURPOSE: Objective is to evaluate the efficacy of the intraarterial calcium test in the preoperative localisation of insulinomas. MATERIAL AND METHOD: To stimulate the pathological release of insulin, calcium gluconate (0.015 meq Ca++/kg) was selectively injected into the arteries supplying the pancreas. Prior to calcium injection and 30, 60, 90 and 120 seconds later, 5 ml samples of blood were obtained from the right or from both right and left hepatic veins. Insulin levels were then determined by mean of immunoassays. A twofold increase in insulin level in the venous sample after 30 or 60 seconds localised the insulinoma to the region of the pancreas supplied by the selectively injected artery. Results of the calcium test were prospectively analysed in 6 patients and compared with operative findings. RESULTS: All 6 patients had a surgically proved solitary and benign insulinoma. Calcium stimulation with venous sampling provided true-positive localisation of insulinomas in all patients without suspicion of liver metastasis. All 6 patients currently have normal insulin levels after a mean period of 16 months (range 4-24 months) with no evidence of hypoglycaemia on fasting. CONCLUSION: Intraarterial stimulation with calcium and hepatic vein samplings for insulin gradients is a very sensitive minimally invasive functional method and may replace transhepatic portal venous samplings for the preoperative detection of insulinomas.

Adult↗
PubMed1998

[Plaque morphology after arterial interventions in the New Zealand white rabbit--which model of restenosis is most suitable?].

PURPOSE: For evaluation of therapy for possible reduction of restenosis after PTA a suitable animal model is needed. The influence of different interventions on arterial plaque composition was analysed in New Zealand White Rabbits. MATERIAL AND METHODS: The following interventions were performed in the infrarenal aorta of New Zealand White Rabbits (n = 42): a) Balloon denudation (BD) with and b) without 0.5% cholesterol diet (CD), c) application of a Wiktor stent, d) CF without BD, and e) control group, 6 weeks after intervention morphometry and histology were performed. RESULTS: After BD the stenosis rate measured 26 +/- 18%, additional CD after prior BD increased the stenoses rate by 2.5 times up to 61.1%. After stent implantation there was only a thin neointimal layer (89 +/- 68 microns) around the stent wires. CONCLUSIONS: Neither implantation of stents nor single CD are suitable as restenosis models. BD with and without CD was followed by a distinct neointima formation with different cellular composition. The New Zealand White Rabbit constitutes an acceptable model for contemporary research in arteriosclerosis.

Angioplasty, Balloon↗
PubMed1998

[Precise MR-guided preoperative marking of breast lesions with an embolization coil using a standard MR coil].

PURPOSE: To develop and test a new technique for MR-guided localisation of breast lesions. MATERIALS AND METHODS: The examinations were performed on a 1.0 T imager in prone position, using a sagittally oriented oval spine coil. The localization device consisted of a perforated lateral plate which can be angulated. The plate contained an "M" shaped tube filled with oil. This enabled exact localization of the lesion in relation to the bore holes on the MR images. After needle placement through a sterile bushing, the 5 mm marking coil was placed through the needle adjacent to the lesion. Then a suspension of charcoal, Gd-DTPA, and water was injected. Suspicious lesions that could be visualised only by MR were localised preoperatively and marked in 6 patients. RESULTS: The lesion size ranged from 0.5 to 3.5 cm (median 1.2 cm). Three benign lesions (intraductal hyperplasia twice, radial scar once) and three malignant lesions (ductal invasive cancer twice, DCIS once) were found. Angulation of the plate was beneficial in three cases. CONCLUSION: With the new marking technique, exact MR-guided localization of breast lesions using an add-on device is feasible. Construction of an additional MR coil is not necessary. Excision of the lesion is proven by the concomitant excision of the marking coil.

Anesthesia, Local↗
PubMed1998

[Transjugular intrahepatic portosystemic shunt in children. Initial clinical experiences and literature review].

PURPOSE: To present special methodical and clinical findings of transjugular intrahepatic portosystemic shunts (TIPSS) in children and to discuss potential indications. PATIENTS AND METHODS: Between 1993 and 1996, 6 children aged 2-13 years were treated by TIPSS-insertion. In four cases, the underlying disease was extrahepatic biliary atresia (EHBA) and in two cases liver fibrosis secondary to treatment of neoplasms during early childhood. Indications for TIPSS insertion were variceal bleeding resistant to other treatment modalities in three patients, hypersplenism in one patient and both bleeding and hypersplenism in two. Portal vein punctures were performed using 16-gauge needles, because 19-gauge fine-needles showed insufficient stiffness. The mean follow-up was 24.5 months. RESULTS: Shunt insertion succeeded in all children with a mean procedure time of 5.2 hours. Periportal fibrosis associated with EHBA, atypical course of hepatic veins and small diameters and distances of vessels were conditions making the procedure difficult. Bleeding ceased in all patients, peripheral platelet counts rose by a mean value of 58%. Procedure-related complications were minor extrahepatic bleeding in one child and temporary haemolysis in another child. Restenosis resulted in three patients and were treated successfully by means of transjugular interventions. 5 children remain free of symptoms to this day, one child underwent successful orthotopic liver transplantation 8 months after TIPSS. CONCLUSIONS: TIPSS insertion is technically more difficult in children and has to consider child growth and possible subsequent liver transplantation. Potential indications are recurrent variceal bleeding, also of intestinal origin, resistant to standard treatment and clinically significant hypersplenism.

Adolescent↗
PubMed1998

[Intra-arterial application of the ACE inhibitor ramipril using a microperforated catheter for the prevention of neointimal proliferation after angioplasty in an animal model].

PURPOSE: To evaluate the safety and benefit of a high-dose local drug administration via a microporous balloon catheter to prevent neointimal formation after balloon angioplasty. MATERIALS AND METHODS: In New Zealand white rabbits (n = 29) neointima formation was induced by balloon denudation. Additionally, the animals were fed a 0.5% cholesterol diet for 6 weeks. Directly after the denudation, local application of 1.8 mg ramipril (n = 7) or saline (n = 7) via a microporous balloon catheter was performed. Other animals (n = 7) were treated with a systemic ramipril administration. One control group were exclusively fed with a cholesterol diet (n = 8). 6 weeks after intervention the animals were sacrificed and morphometry of the vessels was performed. RESULTS: Local administration of ramipril resulted in a non-significant reduction of 17%. The local administration mode was combined with a significant increase in neointima formation. Systemic ramipril administration resulted in a 66% reduction of plaque area. CONCLUSIONS: The benefit of the local ramipril administration was diminished by the inherent vessel trauma. Systemic ramipril administration resulted in a significant reduction of neointimal proliferation in New Zealand white rabbits.

Angioplasty, Balloon↗
PubMed1998

[Stability of iodinated contrast media in UV-laser irradiation and toxicity of the photoproducts].

PURPOSE: In XeCl-Excimer laser angioplasty, unintended and possibly harmful interaction of the UV-laser light and the contrast media may occur due to the high concentration of contrast medium proximal to the occlusion or subtotal stenosis. METHODS: One ml of three nonionic monomeric contrast agents (iopromide, iomeprol, iopamidol), one nonionic dimeric (jotrolane), and one ionic monomeric (amidotrizoate) X-ray contrast agent were irradiated with a XeCl excimer laser (lambda = 308 nm, pulse duration 120 ns, 50 Hz) using a 9 French multifiber catheter (12 sectors). Up to 20,000 pulses (106 J) were applied. Using high performance liquid chromatography the amount of liberated iodide as well as the fraction of unchanged contrast media were measured. Cytotoxicity of the photoproducts was tested in a colony formation assay of human skin fibroblasts. The contrast agents were irradiated with 2000 pulses/ml (5.3 mJ/pulse; 10.6 J) and then added to the cell cultures for a period of three hours in a concentration of 10%. RESULTS: Excimer laser irradiation induced iodide liberation of up to 3.3 mg iodide/ml. Up to 19% of the contrast agents changed their original molecular structure. Incubation of irradiated contrast agents resulted in a significantly decreased potential for colony formation (p values ranging from 0.0044 to 0.0102) with significantly higher toxicity of amidotrizoate and iomeprol in comparison to iopromide, iotrolan, and iopamidol. DISCUSSION: Due to the cytotoxic photoproducts and the high level of liberated iodide, it is recommended to flush the artery with physiological saline solution before applying a pulsed excimer laser in human arterial obstructions in order to reduce the contrast agent concentration at the site of irradiation.

Cells, Cultured↗
PubMed1998

Abdominal aortic aneurysms: treatment with juxtarenal placement of covered stent-grafts.

PURPOSE: To determine the technical feasibility and clinical outcome of juxtarenal placement of covered stent-grafts for endovascular treatment of abdominal aortic aneurysms with a proximal neck less than 15 mm long. MATERIALS AND METHODS: In seven patients, abdominal aortic aneurysms with infrarenal necks 3-14 mm long were excluded with juxtarenal implantation of polyester-nitinol coknit stent-grafts. The proximal uncovered portion of the stent-graft (length, 12 mm) was placed across one or both orifices of the renal arteries. Seven patients underwent standard infrarenal stent-graft placement. Clinical outcome in all 14 patients was determined with computed tomography (CT) and laboratory values and also with captopril renography in the patients who underwent juxtarenal placement. The mean follow-up was 10.1 months. RESULTS: Findings from serial follow-up CT and laboratory analysis performed in all patients and captopril renography performed in five of the patients who underwent juxtarenal stent-graft placement did not reveal impaired renal function or perfusion. CONCLUSION: Successful exclusion of abdominal aortic aneurysms located closer than 15 mm to the orifices of the renal arteries is possible with juxtarenal placement of the uncovered portion of the stent in the abdominal portion of the aorta.

Aged↗
PubMed1998

Insulinoma and islet cell hyperplasia: value of the calcium intraarterial stimulation test when findings of other preoperative studies are negative.

PURPOSE: To evaluate the efficacy of the intraarterial calcium test in localizing sources of hyperinsulinism that remain undetectable at preoperative morphologic studies. MATERIALS AND METHODS: Twenty-four patients with clinically proved endogenous hyperinsulinism due to tumorous insulin production were prospectively enrolled. They underwent ultrasound (US), computed tomography, magnetic resonance imaging, endoscopic US, abdominal arteriography, and a calcium test, in which insulin concentrations were measured in hepatic venous blood after selective intraarterial calcium stimulation. The results of the calcium test in seven patients (five women, two men; age range, 30-66 years; mean age, 47 years) with negative findings of morphologic studies are described. RESULTS: Six solitary insulinomas (mean diameter, 0.73 cm) and one nodular hyperplasia were diagnosed after surgery. In all seven cases, calcium test findings allowed accurate localization of the pathologic source of insulin secretion. In three of these seven cases, results of arterial calcium stimulation with hepatic venous sampling (ASVS) affected intraoperative management. An increase in insulin concentration after stimulation in the hepatic artery was not observed, making hepatic metastases unlikely. CONCLUSION: ASVS, which is procedurally simpler than transhepatic pancreatic venous sampling, is effective for localizing sources of hyperinsulinism not detected with preoperative morphologic studies.

Calcium Gluconate↗
PubMed1997

[Treatment of osteoid osteoma with CT-guided drilling and ethanol instillation].

HISTORY AND CLINICAL FINDINGS: For 6 months a 25-year-old man had been suffering from intermittent pain in the left upper leg, alleviated by aspirin. Physical examination was unremarkable: local pain was not elicited. INVESTIGATIONS: Routine radiology and computed tomography confirmed the clinically suspected diagnosis of intracortical osteoid osteoma of the femur. Skeletal scintigraphy showed distinctive local concentration of the contrast material. DIAGNOSTIC PROCEDURE, TREATMENT AND COURSE: The lesion's central area was identified by CT and under general anaesthesia drilled into (5 mm diameter drill bit). As the lesion's edges remained partially intact, the cavity was sterilized with 1-2 ml of 96% ethanol. The patient was mobilized after six hours. He has remained free of pain in the subsequent 7 months. CONCLUSIONS: Minimally invasive, CT-guided percutaneous treatment of an osteoid osteoma can be achieved by a combined radiological and percutaneous orthopaedic procedure as an alternative to open surgery.

Adult↗
PubMed1997

Highly selective water and fat imaging applying multislice sequences without sensitivity to B1 field inhomogeneities.

Improved selectivity to one chemical shift component was obtained using simultaneous slice-selective and chemical shift-selective excitation in sequences with usual spin-echo refocusing. The new type of sequences can be applied on modern whole-body units and permits multislice operation. Spatial-spectral excitation is based on prior research in this field, but the proposed improved version provides off-center slice excitation by the usual processing of the RF pulse envelopes. In addition, no irregular gradient shapes are necessary. The required B0 homogeneity of the new method is similar to conventional "fat-sat" techniques. In contrast to fat-sat methods, selectivity to water is not reduced by unavoidable misadjustments of the transmitter or B1 field inhomogeneities in the newly developed approach. Thus, the reported method has the potential to replace standard frequency selective fat-sat sequences for most applications.

Humans↗
PubMed1997

[Effect of age and menstrual cycle on mammography and MR mammography].

Age and menstrual cycle have an important influence on the breast. This well-known fact is experienced in the daily routine of gynecologists and radiologists. The number of publications addressing the effect of these influences on imaging, however, is surprisingly low. The aim of this work is to describe the influences of age and menstrual cycle on the breast and to address their clinical relevance for mammography and MR mammography. Therefore, own data are presented concerning the age and menstrual cycle influences on breast parenchyma in dynamic MR mammography. Literature data are used to correlate mammography and MR imaging findings with these influences. The changes of the breast due to age and menstrual cycle have important direct implications on performing and reading conventional mammography and MR mammography. The knowledge of these changes is also helpful in the interpretation of findings when comparing different methods. Finally, the data gained by using imaging methods enable important basic insights into physiology and physiopathology of the breast in vivo.

Adolescent↗
PubMed1997

Perianal complications of Crohn disease: MR imaging findings.

The aim of this study was to revisit anal anatomy, to explain surgical terminology in perianal complications of Crohn disease, and to show the MR imaging findings of perianal fistulas and abscesses. To this end more than 200 patients were studied using surface coils (Helmholtz; phased array) at 1.0 and 1.5 T. Transverse and coronal T1- and T2-weighted images were obtained. Parks' classification was used to describe perianal abscesses and fistulas. This pictorial essay shows the normal anal anatomy and pathologic findings such as subcutaneous, para-anal, ischiorectal, intersphincteric, and supralevatoric abscesses and fistulas. MR imaging with surface coils is well suited to showing the anal anatomy and to reliably describing perianal abscesses and fistulas according to surgical terminology.

Abscess↗
PubMed1997

[The adjuvant use of the monoclonal antibody c7E3 Fab in peripheral arterial thrombolysis].

Thrombolysis of arterial occlusions has limitations, e.g. it requires extensive time for thrombolysis, occlusions may be resistant to lysis, and the rate of reocclusions may be high. c7E3 Fab inhibits platelet aggregation by binding to the GPIIb/IIIa receptor on platelets. Experimentally, this monoclonal antibody has been shown to decrease, the time required for lysis, and to prevent reocclusion. This is the first report on the adjunctive use of c7E3 Fab in peripheral arterial occlusions in humans. Three patients with occlusion of the iliac or femoropopliteal artery were treated with c7E3 Fab (bolus injection of 0.25 mg/kg KG + i.v.-application 12 micrograms/min for 12 h). In addition, the patients received urokinase (100,000 IU bolus + 100,000 IU/h). Heparin (5,000 IU bolus + 1,000 IU/h) and acetylsalicylate (100 mg/day/p.o.). Occlusion length ranged between 6-40 cm. Therapy was successful in all patients. During the follow-up period (4-6 months) no reocclusion occurred. There were no serious side effects like major bleeding or thrombocytopenia. We conclude that the applied doses appear safe. Even the time required for thrombolysis was short, a conclusion in respect of a significant reduction of the time required for lysis can be drawn only after further controlled studies.

Abciximab↗
PubMed1997

[Value of dacryocystography in localization diagnosis of lacrimal duct stenosis].

PURPOSE: Evaluation of dacryocystography in the preoperative localisation of stenosis of the lacrimal passage. METHOD: The lacrimal system of 20 patients (25 eyes) suffering from lacrimal passage obstruction was examined either by conventional (n = 20) or by digital (n = 5) technique. Diagnostic imaging was evaluated concerning topographic Information of the pathologic lacrimal system, localisation of the level and differential diagnosis of the cause of the obstruction. RESULTS: Cause of the obstruction was chronic dacryocystitis (n = 16), dacryolithiasis (n = 1), atresia of the lacrimal duct (n = 2), posttraumatic lesions (n = 3), rhinosinusitis (n = 1) and carcinoma of the maxillary sinus (n = 1). In 23 of 25 cases (92%) we found an exact correlation between dacryocystography and the intraoperative findings. The variation of stenosis types as well as different examination techniques are presented and compared with literature findings. CONCLUSION: Dacryocystography is a valuable method in the diagnosis and preoperative planing in lacrimal system obstruction.

Adolescent↗