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Biomedical subjects

C D Claussen

Publications and source records attributed to C D Claussen.

At least 19 recordsLinked to original sources
PubMed1992

[Role of current diagnostic procedures in gastroenterology: MRI].

The diagnostic value of magnetic resonance imaging (MRI) in gastroenterology has not been definitely defined. In focal liver lesions MRI has a high sensitivity and aids in the differential diagnosis. In pathologies of the gall bladder and the pancreas, MRI currently has no clinical relevance. MRI diagnosis of pelvic fistulas and abscesses in chronic inflammatory bowel disease is both sensitive and specific. MRI is superior to CT in detecting and differentiating recurrent rectal cancer.

Diagnosis, Differential↗
PubMed1992

Volume-selective proton MRS in vertebral bodies.

Volume-selective 1H magnetic resonance spectra of small volume elements of (13 mm)3 positioned in lumbar vertebral bodies have been investigated in 15 healthy persons of different ages and sexes and in 11 patients with leukemia using double spin-echo sequences. Signal intensities and positions of the spectral lines have been evaluated. Interindividual spectra of VOI located in the center of vertebral bodies, intraindividual spectra of central VOI in different vertebral bodies, and spectra of different localizations within the same vertebral body have been compared as well as spectra before and partly after cytostatic treatment in leukemia patients. Unexpected phenomena of the signal shapes have been found. The water signal distributions in healthy persons compared to patients after bone marrow transplantation show significant differences. The success of the cytostatic treatment in cases of leukemia is accompanied by an increase in the intensity of the lipid signals and a decrease in the water signals.

Adipose Tissue↗
PubMed1992

In vitro and clinical feasibility study with an over-the-wire delivery system for pulsed dye laser angioplasty.

The suitability of a pulsed dye laser (504 nm) in experimental and clinical angioplasty was investigated. In an experimental study, the ablation thresholds were 3 J/cm2 +/- 8 (mean +/- standard deviation) for fibrofatty plaque and 25 J/cm2 for calcified tissues under saline. At a radiant exposure of 10 J/cm2 the etch rates were 1.7 microns per pulse +/- 0.3 for media, 2.8 microns/pulse +/- 0.4 for normal intima, and 3.9 microns/pulse +/- 1.1 for fibrofatty plaque (P less than .05). Pressure wave effects with a separation of tissue layers were predominantly localized at the internal elastic lamina. Thermal injury with vacuolations extended 15 microns +/- 6 into adjacent tissue. For clinical study, laser-assisted balloon angioplasty was performed in 10 patients (64 years +/- 14) with occlusions of peripheral arteries using a 9-F multifiber ring catheter. Lesion length ranged from 2 to 12 cm (mean, 7 cm). Laser angioplasty with an 80 mJ/pulse decreased the mean stenosis from 100% to 58% +/- 12% (P less than .005). The ankle-brachial index rose from a median of 0.48 to 0.88 (P less than .001). In 33% of patients, there were subintimal dissections after laser angioplasty. After a mean follow-up of 10.2 months, the overall clinical success was 70% with a primary patency of 78%. The over-the-wire approach with a pulsed dye laser may constitute a safe and feasible tool in laser angioplasty.

Angioplasty, Laser↗
PubMed1992

[Manganese DPDP as a contrast medium for MR tomography of focal liver lesions. Tolerance and image quality in 20 patients].

Twenty patients with focal liver lesions (18 metastases, 1 hepatocellular carcinoma, 1 cholangiocarcinoma) were given manganese DPDP as part of a multicentric phase II study of paramagnetic hepatobiliary MR contrast media. 5 mumol/kg manganese DPDP were injected into 10 patients in a concentration of 50 mumol/ml or 10 mumol/ml (3 ml/min). Blood pressure, pulse rate, ECG, respiratory rate, body temperature, blood and serum parameters and the patients' subjective feelings were recorded. MRI was performed with 1.5 T using T1- and T2-weighted sequences. 6 patients reported 8 side effects (flushing, feeling of warmth, metallic taste); 7 of these were produced by the 50 mumol concentration. Two hours after injection there was a significant reduction in alkaline phosphatase which was no longer present after 24 hours. On T1-weighted images manganese DPDP resulted in marked improvement in the contrast difference between the lesions and the liver parenchyma which resulted in a marked increase in the signal to noise ratio. Comparing the two concentrations, better results were obtained by the lower concentration. Extrahepatic uptake was found in the gallbladder, duodenum, pancreas, kidneys, gastric mucosa and myocardium. Manganese DPDP in a concentration of 10 mumol/ml and a dose of 5 mumol/kg is a well tolerated contrast medium which improves the demonstration of focal liver lesions in view of its distribution and uptake. The mechanisms for the transitory side effects require further studies.

Adult↗
PubMed1992

Comparison of pulsed laser-assisted angioplasty and balloon angioplasty in femoropopliteal artery occlusions.

The authors performed a prospective, comparative study of 96 patients (age, 41-87 years) with femoropopliteal artery occlusions. Laser-assisted angioplasty was performed in 64 patients with 9- and 7-F over-the-wire multifiber catheters. Supplemental balloon dilation was performed after laser angioplasty. Thirty-two patients underwent excimer laser angioplasty (ELA), and 32 underwent pulsed dye laser angioplasty (DLA). The remaining 32 patients underwent conventional balloon angioplasty (BA). The length of occlusions was 3-10 cm (mean, 6.3 cm). Lesion characteristics in the three patient groups were similar. Technical success rates were 84% for ELA, 78% for pulsed DLA, and 81% for conventional BA. The 1-year clinical success rate was 69% (22 of 32 patients) in the ELA group, 63% (20 of 32 patients) in the pulsed DLA group, and 66% (21 of 32 patients) in the BA group (differences were not significant). Laser-assisted angioplasty with multifiber catheters in femoropopliteal artery occlusions did not help improve the technical success rate and 1-year clinical success rate when compared with those of conventional BA.

Adult↗
PubMed1992

[Percutaneous transhepatic cholangioscopic color laser lithotripsy in bile duct calculi].

Tunable dye laser lithotripsy is an effective and low risk treatment in patients with bile duct stones in which transpapillary maneuvers failed. The percutaneous approach allows to introduce small caliber endoscopes (10.5 F) to fragment the calculi under vision. This technique was evaluated in 8 patients who had undergone a biliodigestive anastomosis or in whom the biliary calculi could not removed by standard retrograde treatment. Laser lithotripsy resulted in sufficient fragmentation in 7 patients. Bile duct clearance proved to be a particular problem with the percutaneous access. When a retrograde sphincterotomy is not possible an antegrade papillotomy must be attempted under fluoroscopic guidance. In bile duct strictures the implantation of expandable stents facilitates the passage of fragments and may prevent recurrent stricture and development of new stones.

Aged↗
PubMed1992

Holmium:YAG laser angioplasty. Experimental ablation of vascular tissue via flexible ring catheters.

This experimental study was designed to define the potential value of a mid-infrared holmium laser in the free running mode for angioplasty. Immediately after removal, fresh normal and diseased human cadaveric arteries were irradiated under saline with a Ho:YAG laser (wavelength 2.13 microns). The laser was pulsed at 3 Hz, 250 microseconds pulse width and fluences of 10 to 40 J/cm2. The laser beam was coupled to ring catheters with multiple low-OH quartz fibers. The tip of the delivery device was held in direct contact with the vessel surface with the laser beam oriented perpendicularly. Ablation of atherosclerotic plaque was accomplished at an ablation threshold of 10 J/cm2. The ablation rate was 2.1 to 8.3 microns/pulse. Removal of calcified plaque was only partially effective. There were marked thermal effects with vacuolizations extending up to 1505 +/- 178 microns into the adjacent tissue. Laser light at the mid-infrared wavelength of 2.13 microns is supposed to be attractive as it is readily absorbed in water and can easily be transmitted through optical fibers. However, Q-switching seems to be essential to minimize thermal side effects and to make effective ablation of calcium possible.

Angioplasty, Laser↗
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↗
PubMed1992

[Portal computed tomography. Methodology and indications].

CT arterioportography (CTAP) requires intra-arterial contrast material via the superior mesenteric (splenic) artery. Malignant hepatic tumors are characterized by arterial vascularization and only minimal portal blood supply. Portal contrast therefore reveals small tumors with a high sensitivity of 68-87%. Sensitivity is higher in metastatic tumors than in hepatocellular carcinomas. CTAP is the method of choice for evaluation of the number, size and location of hepatic tumors prior to surgical intervention. If the findings are unclear, additional magnetic resonance imaging and sonography during the operation are useful.

Contrast Media↗
PubMed1991

[Peripheral excimer laser angioplasty. The indications, methods and clinical results].

Between March 1989 and January 1990, percutaneous transluminal excimer laser angioplasty was performed in 61 patients (40 men and 21 females; mean age 66 [41-86] years) with 65 peripheral arterial occlusions (iliac: 11, femoropopliteal: 48, tibial: 5, left subclavian artery: 1). The average ankle-arm index before treatment was 0.45 (0.2-0.8) for iliac, 0.52 (0-0.7) for femoropopliteal and 0.3 (0.1-0.4) for tibial occlusion. Recanalization was successful in 58 occlusions, but additional balloon dilatation was necessary in 54. The mean residual stenosis degree after laser application was 54%, after balloon dilatation 22%. Postangioplasty thromboembolism occurred in five patients. Intravascular stents were implanted in 11 patients because of extensive dissection or high-grade restenosis. After four weeks the clinical findings were improved in 54 of the 58 patients, in 47 even after six months. At that point the average ankle-arm index was 0.88 (0.5-1.1) after iliac, 0.79 (0.6-1.15) after femoropopliteal and 0.6 (0.4-0.7) after tibial recanalization.

Adult↗
PubMed1991

Laser angioplasty of peripheral arterial occlusive disease.

To evaluate the impact of laser ablation of arteriosclerotic material on the long-term results of transluminal angioplasty, 103 patients were treated by laser-assisted recanalization of peripheral arterial occlusion and followed-up for 6 and 12 months. Two pulsed laser systems (308 nm-excimer laser and 504 nm-dye laser) were tested. Laser energy was transmitted via wire-guided 4.5-, 7- and 9-French multifiber catheters. Stand-alone laser angioplasty was possible in 22% of the patients, especially in the popliteal and the lower-limb arteries. Compared to the results of balloon dilatation in the literature, the clinical success rate at 6 and 12 months after the treatment was better in occlusions with a length between 6 and 10 cm, however no improvement was seen in either shorter or longer occlusion. Due to the limited size of percutaneously applicable catheters, laser treatment and pretreatment seemed to be of most benefit in distal femoropopliteal arteries and in lower-limb arteries. Clinical improvement after revascularization depends on a sufficient run-off in branching vessels distal to the recanalized artery segment.

Adult↗
PubMed1991

Angiodynography (color-coded duplex sonography) in the evaluation of vasculogenic impotence.

The penile arteries of 18 men with erectile dysfunction were examined by angiodynography (color-coded duplex sonography). Blood flow velocity was measured before and after intracavernous injection of papaverine/phentolamine. The angiodynographic findings were compared to arteriography. Normal values of peak flow velocity (after injection) were obtained from 6 men with normal arteriographic findings (deep artery greater than 25 cm/s, superficial artery greater than 30 cm/s). Angiodynography enables good imaging of the four penile arteries superior to duplex sonography. A strong correlation with the arteriographic findings could be found. Thus noninvasive angiodynography may replace penile arteriography for the routine evaluation of impotence.

Adult↗
PubMed1991

Dye laser-assisted angioplasty with multifiber catheters: short-term results in the treatment of 29 peripheral arterial occlusions.

The use of pulsed dye laser energy for angioplasty offers the possibility of ablating atherosclerotic plaques without thermal damage to the adjacent arterial wall. However, to be of value, systems that deliver the energy safely and effectively are required. We tested multifiber catheters in 504-nm pulsed dye laser angioplasty for treatment of peripheral arterial occlusions. Flexible multifiber catheters consist of 12 (7-French) and 19 (9-French) concentrically arranged 200-microns quartz fibers allowing guidewire-directed use. Laser-assisted angioplasty was performed in 2- to 13-cm- (mean, 7.5-cm) long occlusions of iliac (six) and femoropopliteal (23) arteries in patients with symptomatic occlusive vascular disease. Angiograms were obtained before and after laser ablation, after subsequent balloon dilatation, and if signs or symptoms indicated restenosis, during follow-up. The laser procedure was impossible to perform in three (10%) of 29 patients; this was related to unsuccessful passage of the wire in one patient and to inability to advance the laser catheter across the lesion in two patients. In one other patient, reocclusion occurred 1 day after angioplasty. Stand-alone laser angioplasty relieved residual stenosis of less than 30% in six (26%) of 23 femoropopliteal arteries, making balloon dilatation dispensable. Immediate clinical improvement was achieved in 26 (90%) of 29 patients. Laser treatment caused no perforation and no embolization, but minor dissections occurred in 36% of the patients. Our experience suggests that pulsed dye laser angioplasty via multifiber catheters converts arterial occlusions into stenoses. With the exception of angioplasty in distal femoropopliteal arteries, additional balloon dilatation is necessary to complete recanalization.

Aged↗
PubMed1991

[Pancreas].

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Acute Disease↗