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Biomedical subjects

C D Claussen

Publications and source records attributed to C D Claussen.

At least 73 records · Page 4Linked to original sources
PubMed2004

[MRI monitoring of autologous hyaline cartilage grafts in the knee joint: a follow-up study over 12 months].

PURPOSE: To evaluate the suitability of different MR sequences for monitoring the stage of maturation of hyaline cartilage grafts in the knee joint and the early detection of complications like hypertrophy. In addition, it was analyzed whether indirect MR arthrography can indicate debonding of the graft. MATERIALS AND METHODS: MRI examinations were performed in 19 patients, aged 17 - 48 years, with autologous transplantation of a hyaline cartilage tissue graft after knee trauma. Examination dates were prior to transplantation to localize the defect, and 6 weeks, 3, 6 and 12 months after transplantation to control morphology and maturation of the autologous graft. Standard T2- and proton-density-weighted turbo spin echo (TSE) sequences and T1-weighted spin echo (SE) sequences were used, as well as gradient echo (GRE) sequences with and without magnetization transfer (MT) prepulses. In some cases, indirect MR arthrography was performed. RESULTS: Cartilage defect and the hyaline cartilage graft could be detected in all 19 patients. Hypertrophy of the graft could be found early in 3 patients and debonding in 1 patient. For depicting the graft a short time after surgery, T2-weighted TSE-sequences showed the best results. Six and 12 months after transplantation, spoiled 3D-GRE-sequences like FLASH3D (fast low angle shot) showed reduced artifacts due to magnetic residues from the surgery. Difference images from GRE-sequences with and without MT pulse provided high contrast between cartilage and surrounding tissue. The quantification of the MT effect showed an assimilation of the graft to the original cartilage within 12 months. Indirect MR arthrography showed subchondral contrast medium even 12 months after transplantation in 3 patients. CONCLUSION: MRI allows a reliable depiction of the hyaline graft and provides very early detection of complications like hypertrophy. The MT effect seems to be correlated with maturation of the graft and allows selective depiction of normal cartilage and engrafted cartilage.

Adolescent↗
PubMed2004

[Early prediction of treatment response to high-dose chemotherapy in patients with relapsed germ cell tumors using [18F]FDG-PET, CT or MRI, and tumor marker].

PURPOSE: To assess the ability of [(18)F]FDG-PET, CT/MRI and serum tumor marker (TM) for the early prediction of response in patients with metastatic germ cell tumors (GCT) undergoing salvage high-dose chemotherapy (HD-CTX). MATERIALS AND METHODS: Before commencement of HD-CTX, 19 patients with metastases from GCT were evaluated with [(18)F]FDG-PET, CT or MRI and TM after 2-3 cycles of induction chemotherapy and the results compared with those of the baseline examinations. PET was analyzed visually and quantitatively by calculating the standard uptake value (SUV). CT or MRI was evaluated for changes in tumor size (progressive disease/stable disease PD/SD = viable lesion; partial remission/complete remission PR/CR = nonviable lesion), density or signal intensity, homogeneity and contrast enhancement. For the prognosis, the worse case, i.e., the most vital lesion detected in a patient, was considered. The reference standard was the result of the histology after resection of any residual masses (N = 10) and/or the clinical-radiological follow-up for at least 6 months after completion of the treatment (N = 9). RESULTS: Six of nineteen patients (32 %) remained progression-free for over 6 months following treatment, whereas 13 (68 %) progressed. The outcome of HD-CTX was correctly predicted by PET, CT and TM in 89 %, 67 % and 88 %, respectively. In 5 of 6 patients with successful HD-CTX, PET was negative (mean SUV = 1.8), with CT or MRI showing a partial regression of the tumor in 4 of 5 patients. Of the 13 patients not cured by HD-CTX, the PET data were positive in all (mean SUV = 2.7), and the CT/MRI results were true positive (PD or SD) in 8 and false negative (PR) in 5 patients. The combined assessment of CT and TM corrected 3 false negative prognoses and 1 false positive CT prognosis. Two patients with unfavorable outcome despite a favorable response by CT and TM criteria were exclusively identified by PET. The resultant sensitivities and specificities for the prediction of therapy response are as follows: PET 100% and 67%; CT/MRI 62% and 80%; TM 83% and 100%; CT+TM 85% and 83%. CONCLUSION: FDG-PET has a high prognostic value for predicting the response to chemotherapy in patients with metastatic GCT early in the course of treatment and may improve patient selection for subsequent HD-CTX protocols. Especially in patients with response to induction chemotherapy according to CT or TM evaluation, PET offers additional information to detect patients with an overall unfavorable outcome.

Adult↗
PubMed2004

MR visualization of the inner ear structures: comparison of 1.5 Tesla and 3 Tesla images.

AIM OF THE STUDY: To compare high resolution MRI examinations of inner ear structures at 1.5 T and at 3 T. METHOD: Temporal bones were measured bilaterally in 3 healthy volunteers in a 1.5 T and in a 3 T MR-scanner using the respective one channel head coil (quadrature detection) of the manufacturer. The same steady-state gradient echo sequence (3D-CISS) was employed at a voxel size of 0.4 x 0.4 x 0.4 mm(3). The signal-to-noise ratio (SNR) was determined quantitatively. RESULTS: An SNR of 8 could be achieved for the measurements at 3 T in 7:37 min. The SNR at 3 T was, on average, a factor of 1.34 higher than that at 1.5 T despite the fact that the excitation angle had to be drastically reduced (alpha = 42 degrees instead of alpha = 70 degrees at 1.5 T) due to the limit of the specific absorption rate (SAR). DISCUSSION: The MR representation of the inner ear is clearly improved at 3 T. To obtain the same SNR at 1.5 T approximately the double measuring time would be required, connected with reduced patient comfort and an increased risk for a displacement of the head during the high resolution measurement.

Cochlea↗
PubMed2004

Muscle type dependent increase in intramyocellular lipids during prolonged fasting of human subjects: a proton MRS study.

The amount of intramyocellular lipids in skeletal muscle was assessed by proton magnetic resonance spectroscopy during a voluntary fasting period of 120 h in four healthy lean volunteers. The aim of the study was to determine whether muscular lipid uptake in the presence of high plasma lipid levels, or lipid oxidation due to lacking glycogen as a source of energy in musculature, are the dominant effects on intramyocellular lipid levels under fasting conditions in various muscle types. Intramyocellular lipids were quantified in the tibialis anterior (mixed type I and type II fibers, predominantly type II) and the soleus muscle (predominantly type I fibers) before and after 24 h, 72 h, and 120 h of fasting. An extreme increase in intramyocellular lipids to levels of 369 % (median) was found in the tibialis anterior muscle compared to baseline value (intramyocellular lipid level prior to fasting, set to 100 %; p = 0.02). The soleus muscle with clearly higher baseline content of intramyocellular lipids (2 - 4-fold compared to tibialis anterior) revealed slightly delayed and less pronounced uptake of intramyocellular lipids during fasting to 152 % (median) after 120 h (p = 0.02). The absolute increment in intramyocellular lipids (in terms of ratios between lipid and creatine signals) was also higher in tibialis anterior than in soleus (not statistically significant). These findings indicate augmentation of the intramyocellular lipid pool during long-term elevation of plasma FFA in the presence of low plasma insulin concentrations in both muscles investigated. The rate of muscular lipid oxidation during fasting is clearly lower than the increased uptake of FFA by myocytes.

Adult↗
PubMed2004

Non-invasive evaluation of atherosclerosis with contrast enhanced 16 slice spiral computed tomography: results of ex vivo investigations.

OBJECTIVE: To evaluate the diagnostic accuracy of 16 slice computed tomography (CT) in determining plaque morphology and composition in an experimental setting. The results were compared with histopathological analysis as the reference standard. METHODS: Nine human popliteal arteries derived from amputations because of atherosclerotic disease were investigated with multislice spiral CT (MSCT). Atherosclerotic lesions were morphologically classified (completely or partially occlusive, concentric, eccentric), and tissue densities were determined within these plaques. In addition, vessel dimensions were quantitatively measured. RESULTS: The results were compared with histological analysis. The concordance index kappa for morphological classification was 0.88. Plaque density (n = 51 lesions) was significantly different (p < 0.0001) between lipid rich, fibrotic, and calcified lesions (Stary stage III: n = 2, 58 (8) Hounsfield units (HU); Stary V: n = 11, 50 (21) HU; Stary VI: n = 14, 96 (42) HU; Stary VII: n = 6, 858 (263) HU; Stary VIII: n = 18, 126 (99) HU). The concordance index kappa for the classification of plaques based on density was 0.51. Vessel dimensions had a good correlation (r = 0.98). CONCLUSIONS: 16 slice CT was found to be a reliable non-invasive imaging technique for assessing atherosclerotic plaque morphology and composition. Although calcified lesions can be differentiated from non-calcified lesions, the diagnostic accuracy in further subclassifying non-calcified plaques as lipid rich and fibrotic is low, even under experimental conditions.

Contrast Media↗
PubMed2004

Multislice CT in cardiac and coronary angiography.

In the last 2 years, mechanical multidetector-row CT (MDCT) systems with simultaneous acquisition of four slices and a half second scanner rotation time have become widely available. Data acquisition with these scanners allows for considerably faster coverage of the heart volume compared with single slice scanning. This increased scan speed can be used for retrospective gating together with 1 mm collimated slice widths and allows coverage of the entire cardiac volume in one breath-hold. First results from studies in correlation with intracoronary ultrasound suggest that MDCT technology not only offers the possibility to visualize intracoronary stenoses non-invasively, but also to differentiate plaque morphology. This is especially the case with the next generation of 16-row MDCT systems. An increased number of simultaneously acquired slices and submillimetre collimation for cardiac applications allows true isotropic scanning with high temporal resolution. Contrast-enhanced MDCT is a promising non-invasive technique for the detection, visualization and characterization of stenotic artery disease. It could act as a gatekeeper prior to cardiac catherization and finally replace conventional diagnostic modalities.

Calcinosis↗
PubMed2004

Extensive peritoneal and omental lymphomatosis with raised CA 125 mimicking carcinomatosis: CT and intraoperative findings.

Diffuse peritoneal and omental seeding are well-known forms of dissemination of metastatic carcinoma. A wide variety of primary neoplasms may cause peritoneal and omental carcinomatosis, most commonly carcinomas of the ovary, gastrointestinal tract and breast. Extensive involvement of the peritoneal cavity with lymphoma is, however, rare. The association of peritoneal lymphoma with a raised CA 125, a tumour marker which is commonly raised in ovarian carcinoma, is a highly challenging clinical situation, which to our knowledge has not been published before in the medical literature. Not being aware of the possibility of this unusual combination of clinical, laboratory and imaging findings can lead to an erroneous diagnosis, as in our case.

Adult↗
PubMed2004

Evaluation of combined transmission and emission tomography for classification of skeletal lesions.

OBJECTIVE: This study assessed the benefit of transmission emission tomography (TET) for classification of skeletal lesions in patients with known malignant disease. SUBJECTS AND METHODS: The TET technology combines acquisition of SPECT and CT data using the same imaging device, thus allowing perfect overlay of anatomic and functional images. We performed TET in 47 patients with tumors who had a total of 104 focal lesions found on bone scintigraphy. Technetium-99m diphosphonate was used as the radiopharmaceutical in all patients. Findings of bone scintigraphy (planar and SPECT), SPECT + CT or radiography, and TET were compared with regard to the precise location and nature (benign vs malignant) of each lesion. Validation was achieved by radiologic follow-up on CT, MRI, or radiography, especially for the extremities, and using biopsy results in five patients. RESULTS: TET could classify 88 (85%) of 104 lesions compared with 37 (36%) of 104 on SPECT. When we counted inconclusive studies as positive for cancer, discrepant findings between SPECT and TET were obtained in 39 lesions. In 38 (97%) of these, TET was correct. Sensitivity for cancer detection was 98% for TET and 94% for SPECT (p = 0.63), and specificity was 81% for TET and 19% for SPECT (p < 0.0001). The highest diagnostic gain was in the spine, thoracic cage, skull, and pelvis. Small osteolytic lesions were missed because of the limited resolution of transmission images. SPECT + CT or radiography and TET were discordant in nine of 104 lesions. TET was false-negative in one lesion and false-positive in another, and SPECT + CT or radiography was false-positive in seven lesions. As a result, sensitivities of TET and SPECT + CT or radiography were nearly the same, but the specificity of TET was significantly higher (p = 0.015). CONCLUSION: TET improves the accuracy of bone scintigraphy by correctly classifying equivocal lesions, especially by identifying benign abnormalities in the axial skeleton and thus increasing the specificity of positive findings.

Adult↗
PubMed2003

Assessment of peripheral arterial occlusive disease: comparison of multislice-CT angiography (MS-CTA) and intraarterial digital subtraction angiography (IA-DSA).

PURPOSE: The aim of the study was to assess the arterial vascular system of the lower extremities in patients with peripheral arterial occlusive disease using Multislice-CT angiography (MS-CTA) and to compare the results with the standard of reference, intraarterial digital subtraction angiography (IA-DSA). MATERIALS AND METHODS: MS-CTA and IA-DSA of the lower extremities were carried out on 23 patients with peripheral arterial occlusive disease (Fontain Stage IIb: 18, III: 3, IV: 2). MS-CTA comprised a 4 x 2.5 mm collimation, 15 mm table feed/rotation, 0.5 sec rotation time and 3 mm slice thickness (1.5 mm reconstruction increment). Delay time was determined by bolus tracking. 150 ml of contrast media were injected intravenously at a flow rate of 3 ml/sec. Maximum intensity projection (MIP) reformations were performed using a semi-automatic vessel tracking program. MS-CTA (axial and MIP-reformatted images) and IA-DSA were reviewed by two radiologists. The grade of vascular stenosis as well as occlusion were rated on a scale of 0 to 3 (0=0-50% stenosis, 1 = 51-75% stenosis, 2 = 76-99% stenosis, 3 = occlusion). RESULTS: For MS-CTA, the mean delay time was 30.2 s (23-40 s), mean scan time was 37.4 (33-42 s). Data analysis was based upon a total of 1136 vascular segments for both methods (568 each). A comparison of all the evaluated segments in both techniques revealed a MS-CTA / IA-DSA 86.3% match. Out of 442 segments proximal the trifurcation, 386 were correctly assessed in MS-CTA (87.3%) and distal the trifurcation, 101 out of 126 segments were rated correctly (80.2%). In MS-CTA, an overall confidence interval of 95% can be achieved in 83.2% to 89.0% for correctly rated stenosis grading. CONCLUSIONS: In patients with peripheral arterial occlusive disease, MS-CTA of the lower extremity is a promising minimal-invasive method for detection of relevant arterial stenoses. However, the technique was limited to routine diagnostic purposes due to severe calcifications and time consuming reconstruction procedures.

Aged↗
PubMed2003

One case of gram-negative anaerobic spondylodiscitis with Prevotella intermedia.

We report the case of a 45-year-old woman with spondylodiscitis at L1/L2, communicating with paravertebral, intravertebral and bilateral psoas abscesses. Percutaneous computed tomography (CT)-guided abscess drainage and an intravenous antibiotic therapy with Imipenem were performed. After removing the drainage at 2 weeks, the patient was discharged at 4 weeks with normalized blood parameters, normal temperature, and without need for analgesics. The underlying bacterium in the case was a very rare gram-negative anaerobic bacterium: Prevotella intermedia.

Abscess↗
PubMed2003

MDCT: cardiology indications.

In the past 2 years mechanical multidetector-row CT (MDCT) systems with simultaneous acquisition of four slices and half-second scanner rotation have become widely available. Data acquisition with these scanners allows for considerably faster coverage of the heart volume compared with single-slice scanning. This increased scan speed can be used for retrospective gating together with 1-mm collimated slice widths and allows coverage of the entire cardiac volume in one breath hold. Initial results from studies in correlation with intracoronary ultrasound suggest that MDTC technology not only offers the possibility to visualize intracoronary stenoses non-invasively but also to differentiate plaque morphology. This is especially the case with the next generation of 16-row multidetector CT. An increased number of simultaneously acquired slices and sub-millimeter collimation for cardiac applications allows true isotropic scanning with high temporal resolution. Contrast-enhanced MDTC is a promising non-invasive technique for the detection, visualization, and characterization of stenotic artery disease. It could act as a gate keeper prior to cardiac catherization and finally replace conventional diagnostic modalities.

Calcinosis↗
PubMed2003

[Stereotactic vacuum-assisted breast biopsy--success, histologic accuracy, patient acceptance and optimizing the BI-RADSTM-correlated indication].

PURPOSE: To evaluate success, histologic accuracy, patient acceptance and BI-RADS TM-correlated malignancy rate of stereotactic vacuum-assisted breast biopsies in order to optimize the indication. MATERIALS AND METHODS: In 132 patients with mammographically detected breast lesions 166 stereotactic vacuum- assisted 11 gauge core biopsies were performed. All lesions were classified according to the BI-RADS TM categories of the ACR. Removal of the lesion was radiographically assessed as complete, representative or not representative. Patient acceptance was evaluated. RESULTS: Of the 166 lesions, 54 (32.5 %) lesions were judged completely removed, 110 (66.3 %) representatively removed and 2 (1.2 %) not representatively removed. Malignancy was found in 38 (22.9 %) lesions. The rate of malignancy increased from 6.3 % (2/32) for BI-RADS TM category 3 to 16.7 % (19/114) for BI-RADS TM category 4 and increased further to 85 % (17/20) for BI-RADS TM category 5 (p < 0.001). The histology of a sufficient vacuum-assisted biopsy was underestimated in 6 (15 %) of the 40 lesions that were subsequently excised surgically. Most patients (98.5 %; 130/132) stated they would undergo a vacuum-assisted biopsy again. CONCLUSION: Vacuum-assisted breast biopsy is accurate, has a justifiable rate of histologic underestimation and is well accepted by patients. Patients with BI-RADS TM category 4 microcalcification benefit the most. Lesions of BI-RADS TM category 3 and BI-RADS TM category 5 should be biopsied only under special circumstances (family risk of breast cancer; assessment of lesions extension).

Adult↗
PubMed2003

[Visualization of pulmonary vein stenosis after radio frequency ablation for treatment of atrial fibrillation using multidetector computed tomography with retrospective gating].

PURPOSE: With the number of radio frequency ablations (RFA) for treatment of chronic atrial fibrillation increasing, the diagnostic evaluation for RFA associated pulmonary vein stenosis is getting more important. This study investigates the feasibility of the visualization of pulmonary vein stenosis using non-invasive multidetector computed tomography. MATERIALS AND METHODS: Twenty-eight patients were examined following RFA-treatment. A 4-slice (20 patients) and a 16-slice (8 patients) multidetector CT scanner (SOMATOM Volume Zoom and Sensation 16, Siemens, Forchheim, Germany) with retrospective gating was used to assess the pulmonary veins. Lesion severity was determined on a semi-quantitative scale (< 30 %, 30 - 50 %, > 50 %). RESULTS: CT was performed without any complications in all patients. Diagnostic image quality could be obtained in all examinations. The pulmonary veins showed lesions < 30 % in four patients, lesions of 30 -, 50 % in five patients and a stenosis > 50 % in one patient. Eighteen patients showed no lesions. CONCLUSION: Multidetector CT of the pulmonary veins seems to be able to visualize high-grade and low-grade lesions, but larger catheter-controlled studies are needed for further assessment of the diagnostic accuracy and clinical reliability of this noninvasive method.

Adult↗
PubMed2003

Radiopaque markers in endovascular stents--benefit and potential hazards.

AIM: The primary objective of this study was to evaluate the impact of radiopaque markers on stent visibility. The secondary objective was to investigate the impact of such radiopaque markers on localized corrosion at the stent corpus-marker interfaces. MATERIAL AND METHODS: The radiopacity of the following stents was evaluated at different fluoroscopy modes (spotfilm, continuous fluoroscopy, 15 p/s, 7.5 p/s, 3 p/s): Memotherm Flexx (FX), Memotherm Luminexx (LX)(Bard), SMART (SM), SMARTeR (SMR)(Cordis). Four readers evaluated a total of 3200 images (160 per stent per fluoro mode) according to the following radiopacity score (RS): 0 = no stent visible, 1 = poor, 2 = acceptable, 3 = good, and 4 = very good stent visibility. LX and SMR stents (n = 5/group) were subjected to potentiodynamic polarization testing in de-aerated Hanks salt solution at 37 degrees C using a potentiostat. Palmaz-Schatz stents (n = 3) were used as the control group for comparative evaluation. The corrosion current density (I corr ) and the breakdown value (E bd ) were compared parameters of interest. RESULTS: At the spotfilm mode the LX, the SM and the SMR were rated well to very well visible in 99 %, 96 %, 96 %, and the FX only in 64 %. At 7.5 p/s (standard fluoro mode) the LX was considered to be well to very well visible in 77 %, followed by the SMR in 12.5 %, the SM in 1 %, and the FX in 0 %. The SMR stents exhibited the highest E bd values (802 +/- 112 mV vs SCE), while the LX stents exhibited the lowest E bd values (155 +/- 38 mV vs SCE). Also, the average E bd values for the SMR stents were better than those exhibited by the PS stents (503 +/- 107 mV vs SCE). CONCLUSION: Stent radiopacity can be increased significantly with the help of radiopaque markers (p < 0,0001 LX vs. FX). However, the surface condition of the stent corpus and the mode of attachment of the marker onto the corpus may have a significant impact on the uniformity of the final corrosion behavior. It is not feasible to determine the clinical impact of this localized corrosion behavior from this in vitro study. Further experimentation is recommended to ascertain the same.

Coated Materials, Biocompatible↗
PubMed2003

[Radiofrequency ablation ex vivo: comparison of the efficacy of impedance control mode versus manual control mode by using an internally cooled clustered electrode].

PURPOSE: To compare the effectiveness of pulsed (impedance control mode) and non-pulsed (manual control mode) radiofrequency ablation (RFA) by using an internal cooled-clustered electrode. MATERIALS AND METHODS: Ex vivo RF ablations (n = 93) were performed with a 200 W RF generator (Model-Cooled Tip, Radionics, USA) in 10 bovine livers, using the impedance and manual control mode. In the impedance control mode, the generator automatically adjusted the applied RF power to the tissue impedance measured during RF ablation. In the manual control mode, the application of the RF power was constant. Both applications were investigated in a capacity range between 5 and 200 W. The duration for each RF ablation was between 2 and 60 minutes. After RF ablation, the short axis diameter of the necrosis was determined macroscopically and the peripheral zone of the necrosis histologically. RESULTS: The impedance control mode produced lesions with short axis diameters of 5.3 +/- 0.3 cm at a power of 200 W after 60 minutes of RF ablation and the manual control mode lesions with short axis diameters of 4.1 +/- 0.4 cm at a power of 70 W after 8 +/- 2 minutes of RF ablation. The impedance control mode increased significantly the time of RF ablation with higher power and the size of necrosis (p < 0.01). CONCLUSION: In comparison to non-pulsed RF ablation, pulsed RF ablation with internal cooled-clustered electrodes significantly increases the size of the lesions and represents a methodical optimization in our opinion.

Animals↗