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Biomedical subjects

C D Claussen

Publications and source records attributed to C D Claussen.

At least 253 records · Page 14Linked to original sources
PubMed1994

[The color-coded duplex sonography and contrast-enhanced magnetic resonance tomography of scintigraphically cold thyroid nodules].

In order to establish diagnostic criteria, colour-coded duplex sonography was performed on 40 patients who had a total of 43 operatively confirmed thyroid lesions which were scintigraphically "cold" (28 adenomas, 8 carcinomas, 4 cases of thyroiditis and 3 cysts). 32 of these patients also had MRT with T2- and T1-weighted images before and after injection of Gd-DTPA (0.1 mmol/kg). Adenomatous nodules and adenomas showed a peripheral vascular halo on colour-coded duplex sonography with a sensitivity of 96% and a specificity of 93%. Malignant lesions showed marked central vascularisation and on B-images irregular marginal structures. Adenomas and adenomatous nodules showed hyperintense areas on T1-weighted unenhanced MR images and/or homogeneous uptake in the lesion (sensitivity 100%, specificity 77%). Malignant lesions typically showed an irregular margin with increased contrast uptake on MRT. If sonography and colour-coded duplex sonography is unable to classify a lesion with any degree of assurance then MRT with Gd-DTPA enhancement should be performed.

Adult↗
PubMed1994

[The MR tomography of focal liver lesions with the superparamagnetic contrast agent AMI-25 at 1.5 tesla].

Superparamagnetic iron oxide particles (AMI-25) were evaluated as a liver contrast agent in high-field MR imaging (1.5 T). 16 patients with up to 5 presumed focal liver lesions (liver metastases n = 8, HCC n = 5, Klatskin tumours n = 2, FNH n = 1) received 15 mumol Fe/kg BW intravenously and were examined via standard T1- and T2-weighted spin-echo sequences. Quantitative image analysis showed a post-contrast increase of the contrast-to-noise ratio (C/N) from 1.6 to 7.4 on SE 2,500/15 images (p < .05). However, C/N was in the same range on plain SE 2,500/90 scans. Blind evaluation by two independent readers revealed that AMI-25-enhanced images did not provide a significantly increased number of lesions. Two patients reported minor, self-limited side-effects (flush, back pain). We conclude that in contrast to reports at mid-field MR imagers, the use of AMI-25 at 1.5 T does not significantly improve the detection of focal liver lesions on conventional SE images.

Adult↗
PubMed1994

[Peripheral pulsed laser angioplasty--4-year clinical experience].

In 134 patients, 21 iliac, 91 femoropopliteal and 22 crural arterial occlusions were treated by percutaneous laser-assisted angioplasty and in 32 patients femoropopliteal occlusions by conventional balloon angioplasty. Laser angioplasty could be performed in 126 patients following initial guide wire recanalisation using 9.7 and 4.5-F multifiber catheters, respectively. In 72 patients a 308-nm excimer laser and in 54 patients a 504-nm pulsed day laser was used. Luminal opening by laser angioplasty was obtained in 102 of 126 (81%) procedures (9 incomplete catheter passages, 15 persistent occlusions). 95% of iliac, 90% of femoropopliteal and 77% of crural recanalizations including supplemental balloon dilatations (n = 105) and stent implantations (n = 24) succeeded technically. Clinical success rates at 1 (2) years after angioplasty were 95% (89%) for iliac, 66% (63%) for femoropopliteal and 57% (50%) for crural treatments. Technical and clinical results of laser-assisted femoropopliteal recanalizations showed no significant differences in comparison to the results of conventional balloon angioplasty. The use of pulsed lasers for the treatment of peripheral arterial occlusive disease would require further technical improvements.

Adult↗
PubMed1994

[CT-guided percutaneous lumbar sympathicolysis in peripheral arterial occlusive diseases].

Between June 1991 and November 1992, 36 patients with peripheral arterial occlusive disease were treated by CT-guided percutaneous lumbar sympathicolysis. Three months after the procedure, 39% claimed subjective improvement, 53% were unchanged and 8% were worse. Walking distance increased significantly from 86 to 167 m (p = 0.02). There was a comparable increase in walking distance between diabetics and non-diabetics. Comparison of one and two level procedures (each 50%) also showed similar increase in walking distance. There were no serious complications. The results justify the use of CT-guided percutaneous lumbar sympathicolysis in patients with peripheral arterial occlusive disease who are unsuitable for treatment by revascularisation. The procedure can be carried out on an outpatient basis and on otherwise inoperable patients and therefore has significant advantages compared with surgical sympathectomy.

Adult↗
PubMed1994

[Transvenous sonography of the peripheral arterial vessels. The initial clinical results].

Intravascular ultrasound with 20 MHz/6.2-French transducer systems was used for arterial imaging via a transvenous approach. In 20 patients suffering from chronic arterial occlusive disease, 15 iliac arteries were evaluated during diagnostic angiography and 5 femoropopliteal arteries during balloon angioplasty (n = 3) and laser-assisted angioplasty (n = 2), respectively. Transvenous sonography did not allow differentiation of arterial wall layers and determination of vessel diameters as is usually possible during intraarterial sonography. Visualisation of iliac arteries was incomplete. In femoropopliteal vessels, guide wires could be detected within the arterial lumen but not in complete occlusions. Delivery of pulsed laser energy induced bright echoes near the catheter tip within a distance of 1-2 cm. Transvenous sonography is insufficient for monitoring of peripheral angioplasty; however, improved imaging quality might be possible at lower frequencies.

Aged↗
PubMed1994

[CT and HR-CT in the diagnosis of pulmonary complications of bone marrow transplantation].

The aim of this prospective study was to compare conventional and high resolution CT for demonstrating pulmonary complications. 23 patients treated by bone marrow transplantation were included in the study between December 1990 and August 1991. These patients were examined radiologically at regular intervals following the transplants. In 9 patients lung changes were detected by CT: there were pneumonic infiltrates, including one CMV pneumonia, two cases of mild parenchymal fibrosis, two cases of extensive lung fibrosis and one of miliary tuberculosis. The advantages and disadvantages of conventional and high resolution techniques are discussed in relation to our findings.

Adult↗
PubMed1994

[Evacuation proctography: physiological variability and clinical relevance of the anorectal angle and the position of the pelvic floor].

Evacuation proctography is an important imaging method for the investigation of abnormalities of defecation. For this procedure, the most commonly carried out measurements are the ano-rectal angle and the position of the pelvic floor. The given mean values and the physiologically acceptable deviations vary just as much as the perceived clinical value of these measurements. 173 evacuation proctograms were evaluated in a prospective study; the subjective abnormalities were correlated with clinical findings. No significant correlation between the measurements from the proctograms and the clinical findings could be determined. The clinical relevance of these measurements is, therefore, uncertain.

Adult↗
PubMed1994

[The chemoembolization of hepatocellular carcinoma: the computed tomographic findings and clinical results in prospective repetitive therapy].

Between April 1989 and March 1993 162 transarterial chemoembolizations (TACE) were performed repeatedly (mean interval: 2.9 months) in 52 patients with hepatocellular carcinoma (HCC): An emulsion of Lipiodol and epirubicin was injected as selectively as possible in a dosage proportional to liver function and tumour size. Before and after each TACE the size of tumours and ratio of tumour volume containing Lipiodol (RTVCL) were determined in CT and the grade of tumour vascularisation was assessed angiographically. The RTVCL increased from 58% after the first treatment to 73% after the third treatment. RTVCL and Lipiodol retention were higher in responders than in non-responders. Tumours with expansive growth pattern showed a higher response rate (56%) than infiltrating tumours (20%). Mean survival of these patients was different (19 and 8 months; p < 0.01), respectively. Survival rates of all patients were 54, 22, and 11% after 1, 2 and 3 years, respectively. Repeated TACE shows local effectiveness. Three treatments during a period of one year are recommended for patients with Child-Pugh class A cirrhosis.

Adult↗
PubMed1994

[The value of the supine chest x-ray with digital luminescence radiography in relation to the experience of the observer. A ROC analysis in CT-validated cases].

The aim of the present study was to evaluate supine chest radiographs obtained by DLR for the diagnosis of pleural and parenchymatous changes and to compare the accuracy of observers in relation to their experience. 50 examinations, which had been checked by CT, were chosen. The images were examined by 7 doctors (2 non-radiologists, 5 radiologists). Our experience indicates that DLR has high specificity but low sensitivity for the diagnosis of a pneumothorax but relatively high sensitivity and low specificity for other changes (pleural effusions, atelectases and other intrapulmonary opacities). The area under the ROC curve averaged over the 7 rater was similar for these 4 entities. There were marked differences between the observers; the radiologists were considerably better than the non-radiologists. Altogether, the diagnostic value of single DLR examinations was relatively low. In indeterminate cases, additional diagnostic methods should, therefore, be used.

Adolescent↗
PubMed1994

Intravascular ultrasound: value of electronic and mechanical devices for quantifying mild to moderate atherosclerosis.

To define the accuracy of electronic and mechanical ultrasound (US) devices for determining the thickness of intima and media, 32 fresh normal and atherosclerotic human femoral arteries were obtained at necropsy. The samples were imaged with a 64-element array and a mechanically rotating US transducer at 20 MHz. The mean thickness of the intimal and medial layer was measured with electronic calipers followed by histopathologic and micromorphometric analysis. Morphometric correlation for intima showed r = 0.64 for the electronic and r = 0.58 for the mechanical US device. The correlation between ultrasonic and histologic measurement of medial thickness in normal and diseased specimens was r = 0.79 for the multielement and r = 0.76 for the mechanical transducer. In conclusion, multielement array transducers are equivalent to mechanically driven probes in the quantitative assessment of peripheral arterial wall layers. Both systems lack sufficient accuracy in the determination of mild to moderate intimal thickening.

Arteriosclerosis↗
PubMed1994

Transvenous and intra-arterial ultrasound monitoring of laser-assisted angioplasty.

To evaluate the effects of peripheral laser angioplasty in vivo, two new applications of intravascular ultrasound have been tested. Sonography of iliac and femoropopliteal arteries using 6.2-French/20-MHz transducers via a transvenous approach was technical feasible, however, spatial resolution of images was not equivalent to intra-arterial sonography. Catheters and guide wires could be observed in normal and moderate stenotic segments but not in occlusions. Using a combined 9-French multifiber-laser-ultrasound-catheter sonographic analysis of arterial stenoses revealed a reduction of the degree of stenoses from 84 +/- 8% before to 47 +/- 10% after laser angioplasty. Both imaging modalities detected bright echoes during pulsed laser energy delivery with a focal appearance within the occlusion material and a diffuse pattern involving the distal arterial lumen. Probably these effects are caused by optico-mechanical plaque disruptions and ejections of gaseous products during the laser ablation. Further development of combined catheter devices to guide energy delivery by continuous imaging might improve the results of laser angioplasty.

Aged↗
PubMed1993

Posttransplant renal artery stenosis--outpatient intraarterial DSA versus color aided duplex Doppler sonography.

A prospective trial was conducted to assess the accuracy of color aided duplex Doppler (CADD) sonography to rule out transplant renal artery stenosis (TRAS) and to determine feasibility and safety of intraarterial digital subtraction angiography (DSA) in hypertensive renal allograft recipients on an outpatient basis. All patients were hypertensive (n = 18, mean age: 42 +/- 11 years) and underwent CADD and an i.a. DSA with 4F catheters. There was a 4 hour rest post DSA. Duplex Doppler measurements of maximum velocity were obtained. Absolute values of > or = 100 cm/s were considered indicative to suspect TRAS. DSA revealed severe TRAS in 4 patients (22%). The stenoses were located near the iliorenal anastomosis (n = 2) and at the bifurcation of the renal artery (n = 2). Duplex Doppler classified twelve (67%) renal artery pedicles normal (maximum velocity: 79 +/- 23 cm/s). TRAS was suspected in 6 patients with a maximum velocity of 159 +/- 48 cm/s (P < 0.01). False positive CADD diagnoses were due to tortuous graft vessels and a postbiopsy arteriovenous fistula. Sensitivity of CADD was 100%, specificity 86%. There were no DSA related complications. No impairment of graft function occurred. CADD allows renal angiography to be reserved to clarify an inconclusive ultrasound study and for definite diagnosis of angiomorphology and lesion classification. Intraarterial DSA of renal grafts in outpatients may be performed without an increased risk of procedure-related complications.

Adult↗
PubMed1993

The double-line sign of osteonecrosis: evaluation on chemical shift MR images.

The MR appearance of osteonecrosis was assessed on selective fat and water images to further evaluate the features of the double-line sign of osteonecrosis. Conventional T1- and T2-weighted spin-echo and frequency selective chemical shift images of eight patients with avascular necrosis of the femoral head and three patients with bone infarcts were retrospectively reviewed. Eight of 11 patients showed a double-line sign on T2-weighted spin-echo images. In these cases correlation with selective water images revealed that a chemical shift artifact contributed to the appearance and location of the hyperintense line. The double-line sign was not seen in three patients with radiologically and clinically proven osteonecrosis. It is concluded that chemical shift imaging improves our understanding of the nature of the double-line sign.

Adult↗
PubMed1993

Pancreatic and ampullary carcinoma. Ultrasound, computed tomography, magnetic resonance imaging and angiography.

Ultrasound remains the most readily available and least expensive of the imaging techniques used in assessment of the upper abdomen. Ultrasound is very useful in the detection of pancreatic tumors as well as in the evaluation of the extent of the disease. If ultrasound fails technically or is inconclusive, CT is recommended. Determination of CA 19-9 may help to decide whether ultrasound should be followed by CT or other examinations (51). Patients with any equivocal or inconclusive abnormality on ultrasound or CT should undergo ERCP. Even when ultrasound and CT of the pancreas appear normal there may be an indication for performing ERCP if the clinical suspicion of pancreatic cancer is still strong (52). Angiography is a reliable method of assessing major vascular tumor involvement, which to most surgeons would be a sign of unresectability. Although for some investigators CT is superior to angiography in assessing vascular involvement, angiography is performed preoperatively in many cases because it delineates the vascular anatomy, which can be abnormal in up to one third of patients. Percutaneous biopsy is an important technique for confirming the radiologic diagnosis of unresectable pancreatic carcinoma, particularly for differentiating pancreas carcinoma from other focal pancreatic lesions such as islet cell tumor, lymphoma, and chronic pancreatitis.

Adenocarcinoma↗
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↗
PubMed1993

[The value of the AMBER system in demonstrating intrathoracic space-occupying lesions. A comparative ROC study of the AMBER and conventional technics for postero-anterior views of the thorax. Advanced Multiple Beam Equalization Radiography].

Since October 1991 the AMBER technique has been used for the diagnosis of chest diseases in about 4,000 patients. The ability of this technique, compared with conventional methods, for demonstrating intrathoracic masses on p.a. views has been assessed. Amongst the patients there were 43 with coin lesions, 18 with hilar and 33 with mediastinal masses. ROC analysis showed the AMBER technique to be superior in demonstrating coin lesions (AMBER 0.92, conventional 0.85) and mediastinal masses (AMBER 0.89, conventional 0.73). There was a small, statistically not significant, disadvantage in the AMBER technique for demonstrating hilar masses (AMBER 0.80, conventional 0.84).

Chi-Square Distribution↗