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Biomedical subjects

C D Claussen

Publications and source records attributed to C D Claussen.

At least 109 records · Page 6Linked to original sources
PubMed2002

Virtual coronary angioscopy using multislice computed tomography.

BACKGROUND: With faster image acquisition times and thinner slice widths, multislice detector computed tomography (MSCT) allows visualisation of human coronary arteries with diagnostic image quality. In addition to conventional axial slices, virtual coronary angioscopies (VCA) can be reconstructed using MSCT datasets. OBJECTIVE: To evaluate the feasibility of reconstructing VCA and to determine the clinical value of this new application in detecting atherosclerotic coronary artery lesions. METHODS: Datasets obtained by contrast enhanced non-invasive coronary angiography using MSCT (Somatom VZ) were analysed from 14 consecutive patients. VCA were simulated in 14 coronary arteries (left anterior descending, n = 7; right coronary, n = 7). Lesion detection was undertaken on conventional contrast enhanced axial slices, as well as by VCA. Intracoronary ultrasound (ICUS) was used as the gold standard for in vivo plaque detection. RESULTS: 38 lesions were detected both on ICUS and on axial slices: 14 severe target lesions of > 75% area stenosis (11 calcified, three non-calcified), and 24 intermediate lesions of < or = 75% area stenosis (seven calcified, 17 non-calcified). Using VCA, all severe lesions (n = 14) and all calcified intermediate plaques (n = 7) could clearly be identified. However, non-calcified intermediate lesions (n = 17) could not be accurately distinguished from the vessel wall; they were recognised as vessel wall alterations without significant luminal narrowing. CONCLUSIONS: Current MSCT technology allows reconstruction of VCA with good image quality. Despite a more anatomical view of heart and coronary vessels on three dimensional reconstruction, conventional axial slices were found to be superior for detecting coronary lesions. Thus further technical innovations are required before VCA can become a useful technique in clinical cardiology.

Adult↗
PubMed2001

Prophylaxis of restenosis with (186)re-labeled stents in a rabbit model.

BACKGROUND: Intraluminal beta-irradiation has been shown to decrease neointimal proliferation after angioplasty in experimental models. The purpose of this study was to test the technical feasibility and biological effects of (186)Re-labeled stents. METHODS AND RESULTS: Thirty-four New Zealand White rabbits were fed a 0.5% cholesterol diet before balloon angioplasty and insertion of Palmaz stents in the infrarenal aorta. The animals were killed 7 weeks after stent implantation. Two of 34 animals died prematurely (aortic leak, pneumonia). Control stents (n=7) were compared with (186)Re stents (2.6 MBq [n=6], 8.1 MBq [n=5], 16.0 MBq [n=6], and 25.3 MBq [n=8]). Stent application was successful in all cases. No thrombus occlusion was observed. After 7 weeks, neointima formation was 2.2+/-0.2 mm(2) in the control group. In the treatment groups, a dose-dependent neointima reduction was detectable (0.5+/-0.5 mm(2) [2.6 MBq], 0.4+/-0.4 mm(2) [8.1 MBq], and 0 mm(2) [16.0 MBq, 25.3 MBq]). No induction of neointimal formation was observed at the edges of the stents. Radiation resulted in delayed reendothelialization. CONCLUSIONS: (186)Re stents were capable of reducing neointima formation in a dose-dependent fashion. (186)Re stents did not cause late thrombosis or neointimal induction at the stent margins in the observation period of 7 weeks.

Animals↗
PubMed2001

MR cholangiography in the diagnosis of sclerosing cholangitis in Langerhans' cell histiocytosis.

Langerhans' cell histiocytosis (LCH) is a disorder of histiocytic proliferation that primarily affects infants. Imaging findings of a rare case of lung and liver involvement in an adult are presented. High-resolution computed tomography (HRCT) of the lungs showed confluent thin-walled cystic air spaces compatible with advanced LCH. Liver CT and MRI revealed unspecific signs of fatty infiltration. Irregular widening of peripheral bile ducts was displayed in breath-hold MR cholangiography. This pattern is considered characteristic for sclerosing cholangitis and should support the diagnosis of LCH in case of concomitant cystic pulmonary disease, even in adult patients.

Aged↗
PubMed2001

Rhenium-188 for inhibition of human aortic smooth muscle cell proliferation.

PURPOSE: To evaluate dose-dependent growth-modulating effects of the beta-gamma emitter Rhenium-188 on cultured human aortic smooth muscle cells (haSMC). METHODS AND MATERIALS: HaSMC were plated in 25 cm(2) flasks. Two days after plating, cells were incubated with the Re-188 (beta E(max) 2.12 MeV, tissue range(max) < 10 mm, T(1/2) 17 h) for five days. The doses administered were 0.2 Gy, 1, 4, 6, 8, 16, and 32 Gy. After five days, the radionuclide was removed. Cell growth, cell cycle distribution, and clonogenic activity were analyzed for the following 25 days. RESULTS: The 0.2 and 1 Gy groups did not show relevant growth-inhibiting effects compared to the control groups. The 4 to 32 Gy groups presented dose-dependent growth inhibition, with a complete growth arrest of the 16 and 32 Gy groups. Clonogenic activity of the smooth muscle cell was strongly inhibited from doses > or =8 Gy. Flow cytometry showed a lasting dose-dependent G2/M phase block. CONCLUSION: Smooth muscle cell (SMC) growth can be controlled effectively with Re-188 for at least 25 days after radiation in vitro. As the first four weeks after arterial angioplasty are crucial concerning neointimal formation, Re-188 may be a valuable radionuclide to inhibit restenosis after arterial angioplasty.

Aorta↗
PubMed2001

Fast elevation of the intramyocellular lipid content in the presence of circulating free fatty acids and hyperinsulinemia: a dynamic 1H-MRS study.

The influence of a short-term elevation of free fatty acids (FFAs) on intramyocellular lipids (IMCL) under hyperinsulinemic conditions was monitored in five healthy male subjects in the course of a 5-hr hyperinsulinemic glucose clamp. During the glucose clamp a lipid emulsion (Intralipid 20(R)) and heparin were administered intravenously. IMCL was quantified in the tibialis anterior (TA) and the soleus (SOL) muscle by (1)H-MRS. A rapid elevation of the IMCL pool was found in both muscles (61% in TA and 22% in SOL) in the 5-hr time period. A control hyperinsulinemic glucose clamp in the same study group, repeated without elevation of circulating FFAs, did not lead to significant changes in IMCL for both muscles. The present study shows for the first time that only the combination of high concentrations of FFAs and insulin lead to marked storage of lipids in skeletal muscle cells in humans. Magn Reson Med 45:179-183, 2001.

Adult↗
PubMed2001

Noninvasive detection of coronary lesions by multislice computed tomography: results of the New Age pilot trial.

The reliable noninvasive assessment of coronary artery disease would constitute an important step forward in clinical cardiology. The aim of the New Age pilot trial was to evaluate the diagnostic accuracy of multislice computed tomography (MSCT) in determining coronary lesions. As a gold standard for in vivo plaque detection, intracoronary ultrasound (ICUS) was used. Forty plaques were detected by ICUS in 15 target vessels (LAD, n = 8; RCA, n = 7) in patients assigned for ICUS-guided PTCA. Preinterventional MSCT was performed in all patients and the results were compared to ICUS with regard to lesion detection and quantification. According to ICUS results, the 40 plaques were divided into three groups: group I, mild lesions < 50% (n = 14; 44.36% +/- 5.77%); group II, intermediate lesions 50%-75% (n = 12; 59.18% +/- 9.39%); and group III, severe lesions > 75% (n = 14; 91.47% +/- 3.68%). All MSCT scans showed sufficient image quality for analysis. Thirty of 40 (75%) plaques were detected by MSCT in a first blinded session. After unblinding the ICUS results, the remaining 10 (25%) plaques could be identified. Lesion severity was classified correctly in 34 of 40 (85%) plaques. Plaque calcifications were diagnosed correctly in 16 of 19 (84.2%) plaques. Quantification of vessel size revealed a good correlation to the ICUS results (r(2) 0.68; P = 0.004). Noninvasive MSCT angiography showed good diagnostic accuracy with regard to lesion detection and quantification of vessel size. The overall good image quality, makes this new technology a promising modality, which might become an alternative diagnostic approach in patients with known or suspected coronary artery disease. Cathet Cardiovasc Intervent 2001;53:352-358.

Adult↗
PubMed2001

MR-guided biopsy of musculoskeletal lesions in a low-field system.

Thirty magnetic resonance (MR)-guided biopsies were obtained from 20 skeletal and 10 soft-tissue lesions in 31 patients using an open 0.2 T MR system equipped with interventional accessories. The results from aspiration (N = 3), core biopsy (N = 15), and transcortical trephine biopsy (N = 12) were evaluated for accuracy and clinical efficacy. Specimens were successfully obtained from 29 patients. Results were clinically effective in 23 patients, rated definitive in 16, nonconclusive in 9, and unspecific in 2 patients. A false diagnosis due to sampling error occurred in 2 patients, and biopsy sampling was impossible in one case. The best diagnostic yield was achieved from nontranscortical biopsies of osteolytic or soft-tissue masses. Results from transcortical biopsies were less specific due to the predominance of benign lesions. MR fluoroscopy for needle guidance was applied in 13 patients. Complete needle placement inside the magnet could be performed in 16 patients. MR-guided biopsy using an open low-field MR imager is feasible and clinically effective and will become a valuable tool in the management of musculoskeletal lesions. J. Magn. Reson. Imaging 2001;13:761-768.

Adolescent↗
PubMed2001

Osteodensitometry of human heel bones by MR spin-echo imaging: comparison with MR gradient-echo imaging and quantitative computed tomography.

The aim of the study was to investigate whether quantitative magnetic resonance (MR) fast spin-echo (FSE) imaging with moderate spatial resolution enables osteodensitometry in peripheral yellow bone marrow. Signal intensities in T1-weighted FSE images from yellow bone marrow indicate the amount of adipose tissue per volume. The signal intensity in marrow regions with spongy bone was assessed and compared to signal intensity of pure fatty marrow (100%). Heel bones of 30 patients with suspected osteoporosis were analyzed and the FSE images were compared with results from parallel MR gradient-echo (GE) imaging and quantitative computed tomography (QCT) examinations. High correlation was found between FSE imaging and QCT [r = 0.91 in the dorsal region of interest (ROI); r = 0.86 in ventral ROI]. Linear correlation coefficients between GE imaging and QCT were slightly lower in the dorsal part (r = -0.86) and considerably lower in the ventral part (r = -0.68). Correlation between the two MR techniques amounted to r = -0.72/-0.61 (dorsal/ventral). The high correlation between FSE imaging and bone mineral density (BMD) allows possible clinical applications of FSE imaging for diagnosis of osteoporosis. Further improvements of the accuracy using reference phantoms might be possible.

Adult↗
PubMed2001

Subacute myocardial infarction: assessment by STIR T2-weighted MR imaging in comparison to regional function.

PURPOSE: Increased T2 signal intensity (SI) can be regularly observed in myocardial infarction. However, there are controversial reports about the relationship of elevated T2 SI to myocardial viability and some authors propose that high T2 SI serves as a sign of irreversible myocardial injury. This study investigates increased T2 SI compared to myocardial function in patients with reperfused subacute myocardial infarction. Preserved function was used as criterion for viability. METHODS: Ten healthy volunteers and 17 patients with myocardial infarction and patent infarct related coronary artery were examined on a 1.5 T Magnetom Vision system (Siemens). For T2-weighted MR imaging a breath-hold STIR sequence with dark-blood preparation was used. Cine FLASH 2D imaging was applied to assess myocardial function. Signal-to-noise (S/N) in STIR T2 images was measured in normal and infarcted regions and subsequently identified by two independent observers. Based on a 20 segment model of the left ventricle findings were compared to regional myocardial function. RESULTS: Elevated STIR T2 SI was found in all 17 patients and observed in 27% (204/754) of segments. S/N of normal myocardium was 5.1 +/- 0.7 in volunteers and 4.9 +/- 0.8 in patients (P = NS). Infarcted myocardium presented with significantly increased S/N 12.8 +/- 1.9 (P < 0.0001). Significant transmural elevation of T2 SI was noted in 32% of segments with preserved systolic function. CONCLUSION: Increased STIR T2 SI can be observed transmurally in post-ischemic myocardial regions with preserved function. It therefore cannot be used as an exclusive marker for the non-viable region.

Aged↗
PubMed2001

[Technique and results of CT-guided percutaneous bone biopsy].

PURPOSE: The aim of the study was to evaluate the feasibility and results of CT-guided percutaneous bone biopsy (PBB) of unknown bone lesions in a representative number of patients. METHODS: In 92 patients (100 biopsies) with different bone lesions CT-guided PBB was performed. RESULTS: The rate of technical success, defined as a successful retrieval of a sufficient tissue sample which then was sent for histological evaluation, was 89% (89/100 biopsies). The diagnostic accuracy was defined as a clinically useful histological result and was obtained in 80% (80/100 biopsies). Minor complications (minimal bleedings) occurred in 3% of all biopsies, no special therapy was necessary. Osteolytic lesions (92%) were classified more accurately by PBB than osteoplastic (80%) or mixed lesions (67%). Considering the anticipated dignity of the lesions prior to PBB, the suspected malignant bone lesions had a better diagnostic accuracy of 82% than the suspected benign bone lesions with an accuracy of 50%. CONCLUSION: Due to its universal availability combined with a low risk and a high diagnostic value the PBB of unknown bone lesions can be regarded as a valuable diagnostic tool. However, leave-me-alone lesions should be excluded.

Biopsy, Needle↗
PubMed2001

Biphasic spiral CT of the liver: automatic bolus tracking or time delay?

The aim of this study was to evaluate the value of automatic bolus tracking for biphasic spiral CT of the liver in comparison with time delay examinations. Forty patients scheduled for a biphasic spiral CT of the liver randomly were examined either with time delay of 25 s for the arterial phase and 55 s for the portal-venous phase (n = 20), or with an automatic scan start triggered by contrast enhancement in the aorta (n = 20). Examinations were performed with 120 ml of contrast material and a flow rate of 4.0 ml/s. Density measurements of the aorta, of the liver parenchyma, and of the spleen were obtained by means of regions of interest (ROI). The end of the arterial phase was considered when hepatic parenchymal enhancement was greater than 20 HU. In all patients of the group with automatic bolus tracking arterial scanning was completed in the arterial phase of the liver. In 25 % of patients with fixed time delay, however, an enhancement of liver parenchyma during arterial phase greater than 20 HU was observed. During the portal-venous phase there was no significant difference in parenchymal enhancement between both groups. Automatic bolus tracking allows an individualized timing of the arterial phase in biphasic spiral CT of the liver. The timing is more accurate than in time delay scanning.

Adult↗
PubMed2001

Automatic bolus tracking in monophasic spiral CT of the liver: liver-to-lesion conspicuity.

The aim of this study was to evaluate the value of automatic bolus tracking for monophasic spiral CT of the liver and to assess the liver-to-lesion conspicuity in comparison with time-delay examinations. In 40 patients scheduled for therapy control of known hypovascular hepatic metastases a monophasic spiral CT was completed either with time delay of 65 s (n = 20) or with automatic bolus tracking in the liver parenchyma (n = 20). Examinations were performed with 120 ml of contrast material and a flow rate of 3.0 ml/s. For automatic bolus tracking a parenchymal enhancement threshold of 40 HU was used. Contrast enhancement in the liver parenchyma and in liver lesions was obtained by means of regions of interest (ROI). Mean parenchymal enhancement was not significantly different between time delay and bolus-tracking group. In 4 of 20 patients in the bolus-tracking group the threshold level of 40 HU was not reached. With automatic bolus tracking a significantly higher liver-to-lesion density difference was observed (P < 0.0001). Automatic bolus tracking allows a better liver-to-lesion conspicuity in monophasic spiral CT. Contrary to recent studies, a significantly higher parenchymal enhancement was not found using automatic bolus tracking.

Adult↗
PubMed2001

Non-invasive characterisation of coronary lesion morphology and composition by multislice CT: first results in comparison with intracoronary ultrasound.

The reliable non-invasive detection of coronary artery disease (CAD) is a prime goal for future developments in clinical cardiology. In addition to the documentation of high-grade stenoses, the detection of vulnerable plaques is of major importance for risk stratification and early treatment to prevent plaque rupture. Recently, a new generation of fast spiral CT has been introduced using a multi-slice technique (MSCT), which is the first real quantum leap in CT since the introduction of spiral CT in the early 1990s. We report on non-invasive differentiation of coronary plaque morphology by MSCT in patients with lesions in the proximal left anterior descending artery (LAD). The results were compared with the findings of intracoronary ultrasound (ICUS). The ICUS and MSCT scans were analysed in 6 patients scheduled for ICUS-guided PTCA. One target lesion was selected in each patient. On ICUS, two lesions were classified as soft, two as intermediate and two as calcified according to established criteria based on echogenicity. By multislice CT, density measurements (expressed in Hounsfield Units, HU) were performed at 16 randomly selected areas within the plaques. The two soft plaques showed a mean density of 6+/-28 and -5+/-25 HU, the two intermediate plaques of 83+/-17 and 51+/-19 HU, and the two calcified plaques of 489+/-372 and 423+/-111 HU. To our knowledge, this is the first report on non-invasive characterisation of coronary lesions by MSCT. Plaque composition could be clearly differentiated and classified according to the ICUS results by determining tissue density within the lesions. Thus, this new technology holds promise for non-invasive risk assessment in patients with known or suspected CAD since also rupture-prone soft coronary lesions can be detected by use of this new technique.

Aged↗
PubMed2001

Tc-99m-labeled endothelin derivative for imaging of experimentally induced atherosclerosis.

OBJECTIVE: to characterize the potential of an endothelin derivative labeled with technetium-99m (Tc-99m) for the imaging of experimentally induced atherosclerosis. METHODS: neointima of different cellularity and severity of stenosis was induced in 32 rabbits by balloon denudation followed by distinct dietary regimens and drug application. Angiograms and scintigrams after injection of the Tc-99m-labeled endothelin derivative were obtained. The aorta was dissected for autoradiography, sudan-III-staining, morphometry, and immunohistology. RESULTS: the lesions induced could be detected in vivo (whole body scintigram) in all the animals 15 min after the injection of the Tc-99m endothelin derivative. Autoradiography revealed a strong relationship between tracer accumulation and sudan-III-staining of lesions. Accumulation of the endothelin derivative correlated with the number of neointimal smooth muscle cells (SMC), but not with the number of medial SMC, neointimal macrophages, and neointimal area. CONCLUSIONS: the results indicate that in vivo imaging of atherosclerosis with an endothelin derivative is a feasible method of detecting and characterizing atherosclerotic arterial wall lesions at early stages.

Angiography↗
PubMed2001

Hybrid 3D visualization of the chest and virtual endoscopy of the tracheobronchial system: possibilities and limitations of clinical application.

OBJECTIVE: A hybrid rendering method which combines a color-coded surface rendering method and a volume rendering method is described, which enables virtual endoscopic examinations using different representation models. MATERIALS AND METHODS: 14 patients with malignancies of the lung and mediastinum (n=11) and lung transplantation (n=3) underwent thin-section spiral computed tomography. The tracheobronchial system and anatomical and pathological features of the chest were segmented using an interactive threshold interval volume-growing segmentation algorithm and visualized with a color-coded surface rendering method. The structures of interest were then superimposed on a volume rendering of the other thoracic structures. For the virtual endoscopy of the tracheobronchial system, a shaded-surface model without color coding, a transparent color-coded shaded-surface model and a triangle-surface model were tested and compared. RESULTS: The hybrid rendering technique exploit the advantages of both rendering methods, provides an excellent overview of the tracheobronchial system and allows a clear depiction of the complex spatial relationships of anatomical and pathological features. Virtual bronchoscopy with a transparent color-coded shaded-surface model allows both a simultaneous visualization of an airway, an airway lesion and mediastinal structures and a quantitative assessment of the spatial relationship between these structures, thus improving confidence in the diagnosis of endotracheal and endobronchial diseases. CONCLUSIONS: Hybrid rendering and virtual endoscopy obviate the need for time consuming detailed analysis and presentation of axial source images. Virtual bronchoscopy with a transparent color-coded shaded-surface model offers a practical alternative to fiberoptic bronchoscopy and is particularly promising for patients in whom fiberoptic bronchoscopy is not feasible, contraindicated or refused. Furthermore, it can be used as a complementary procedure to fiberoptic bronchoscopy in evaluating airway stenosis and guiding bronchoscopic biopsy, surgical intervention and palliative therapy and is likely to be increasingly accepted as a screening method for people with suspected endobronchial malignancy and as control examination in the aftercare of patients with malignant diseases.

Adult↗