Biomedical subjects

C D Claussen

Publications and source records attributed to C D Claussen.

303 records · Page 17Linked to original sources

PubMedDate not supplied

Superparamagnetic iron oxide: detection of focal liver lesions at high-field-strength MR imaging.

AMI-25 was evaluated at 1.5 T as a superparamagnetic iron oxide contrast agent for the liver. Sixteen patients with up to five suspected focal liver lesions were examined with T1-, proton-density-, and T2-weighted spin-echo sequences before and after intravenous administration of AMI-25 (15 mumol/kg iron). The contrast-to-noise ratio (C/N) increased from 1.8 to 3.5 on 600/15 (TR msec/TE msec) images and from 1.7 to 7.9 on 2,500/15 images after AMI-25 administration (P < .01). C/N did not change significantly on 2,500/90 images. Two blinded readers counted the number of lesions visible on unenhanced and contrast-enhanced images, with the 32 sets of images of the 16 patients presented in random order. Both readers identified more lesions on AMI-25-enhanced images, but the difference was not statistically significant (P > .05). Two patients reported minor side effects (flushing, sensation of heat, lower back pain). On the basis of the results obtained in a limited number of patients, the authors conclude that at 1.5 T, AMI-25 does not significantly improve the detection of focal liver lesions on conventional spin-echo images.

Contrast Media↗

PubMedDate not supplied

Dynamic 3D-MR mammography: is there a benefit of sophisticated evaluation of enhancement curves for clinical routine?

The purpose of the study was to compare standard analysis with pharmacokinetic analysis of time-intensity curves in dynamic three-dimensional (3D) MR mammography (MRM) for their capability of differentiating benign from malignant disease. Dynamic MRM of the whole breast was performed at 1.0 T using an axial fast low-angle shot (FLASH) 3D sequence. For the standard evaluation, the enhancement of the first minute (E1) and the slope of enhancement from minute 2 to 10 (SE2-10) were calculated. For pharmacokinetic analysis, the amplitude of enhancement (A), distribution time (t21), and elimination time (tel) were computed. Sixty-two histologically verified lesions were evaluated. The standard evaluation methods yielded a highly significant difference between benign and malignant disease for E1 (P = .0008) and SE2-10 (P = .0001). The pharmacokinetic parameters gained similarly significant P values (A, P = .0014; t21, P = .0024; tel, P = .0001). Both standard and pharmacokinetic analysis concordantly discriminated between benign and malignant lesions in discriminant analysis. Compared with standard analysis, a pharmacokinetic analysis of time-intensity curves is not beneficial for routine clinical diagnosis.

Adolescent↗

PubMedDate not supplied

Magnetization transfer contrast of hepatic lesions in breath-hold gradient-echo images of different T1 weighting.

Seventeen patients with hepatic lesions [six metastases from colon, breast, and gallbladder carcinoma; one gallbladder carcinoma; five hepatocellular carcinoma; three focal nodular hyperplasia (FNH); one adenoma; and one cyst] were examined by MR breath-hold two-dimensional gradient-echo imaging to assess the potential of magnetization transfer contrast (MTC) for improved conspicuity and classification. Imaging sequences were applied with and without irradiation of off-resonant radiofrequency (RF) prepulses, but other parameters were unchanged. Therefore, quantitative assessment of MTC could be performed. In contrast to former examinations of other researchers, no significant difference of MTC was found between malignant liver lesions and benign lesions as FNH or adenoma. MTC might provide differentiation between hemangioma and cysts versus solid tumors, but MTC is not capable of distinguishing benign and malignant types of solid liver tumors. Effects of unchanged MTC prepulses on signal intensity of normal liver tissue and most lesions were more pronounced for nearly proton density-weighted fast low-angle shot (FLASH) images than for T1-weighted FLASH images, obtained by using higher excitation flip angles. Liver-to-lesion contrast could not be improved clearly by MTC prepulses. The contrast between liver and lesions in the gradient-echo breath-hold images was compared with standard T1- and T2-weighted spin-echo images. Liver-to-lesion contrast in the breath-hold images was found to be inferior to T2-weighted spin-echo images in 14 of 17 cases. Lesion conspicuity in regions near the diaphragm was better in breath-hold images, because problems with marked breathing motion (as in standard imaging) could be avoided.

Adult↗

PubMedDate not supplied

Improved clinical echo-planar MRI using spatial-spectral excitation.

Echo-planar imaging (EPI) is markedly susceptible to B0 field distortions and to frequency differences caused by chemical shift, because the phase of the signals is accumulating during the acquisition train. Thus, only water proton signals are usually recorded after frequency-selective suppression of the fat portions of magnetization. Otherwise, a shifted signal frequency from fat results in ghosting artifacts. In this article, a technique is presented working with spatial-spectral excitation for highly selective water or fat EPI. The proposed method allows recording in multislice operation on EPI scanners without irregular gradient or RF pulse shapes. Examples of gradient-echo and spin-echo EPI using spatial-spectral excitation by series of two to eight single slice-selective RF pulses are demonstrated. The method is not sensitive to misadjustments or inhomogeneities of the B1 field, but sufficient homogeneity of the static magnetic field B0 is required. Especially the quality of diffusion-weighted echo-planar images can be markedly improved by the new technique compared to conventional EPI, because artifacts from undesired chemical shift components are completely avoided.

Adult↗

PubMedDate not supplied

Ultrasound-monitored laser angioplasty: preliminary clinical results.

A novel coaxial catheter system for ultrasound (US)-guided, pulsed laser angioplasty was tested clinically in 4 patients with stenoses of the femoral and external iliac artery. The mean lesion length was 1.3 +/- 0.4 cm. The 9F multifiber laser catheter incorporated a 4.8F commercial intravascular US catheter and can be guided over a 0.014 inch wire. Laser angioplasty alone reduced the mean degree of stenoses from 84 +/- 8% to 47 +/- 10%. Though laser-induced artifacts compromised detailed US monitoring during laser firing itself, the system proved to be clinically useful as assessment of laser effects and measurement of the severity of residual stenoses was possible immediately after laser irradiation.

Aged↗

PubMedDate not supplied

Embolization of renal vascular lesions: clinical experience with microcoils and tracker catheters.

After biopsy (n = 6) and nephrostomy (n = 1) of three native and four transplanted kidneys, gross hematuria, hypertension, and deterioration of function necessitated performance of transarterial embolization. Angiography revealed five arteriovenous fistulas (AVFs), one pseudoaneurysm, and one arteriocaliceal fistula. Superselective catheterization was accomplished using 5 Fr standard diagnostic catheters and 3 Fr coaxial Tracker catheters. Four of five AVFs were embolized successfully by inserting unfibered (2 patients) and fibered (2 patients) platinum coils (diameters 2 mm and 4 mm, respectively). For one AVF, additional injection of butylcyanoacrylate was necessary. The pseudoaneurysm was embolized successfully by such injection, and the arteriocaliceal fistula was occluded using one unfibered 2-mm coil. Embolization stopped the bleeding in all patients. One week after treatment, renal function was improved in 5 patients and remained unaffected in 2. Superselective embolization using Tracker catheters and fibered microcoils is an effective, safe treatment of renal vascular lesions.

Adult↗

PubMedDate not supplied

Contrast enhanced MR-guided biopsy of hepatocellular carcinoma.

Magnetic resonance (MR)-guided liver biopsy was performed in three patients with hepatocellular carcinoma. The tumor was considered (n = 2) or proven (n = 1) inaccessible with ultrasound or computed tomographic guidance. Because all lesions were poorly delineated on nonenhanced MR imaging, contrast agents (Gd-BOPTA, n = 1; ferucarbotran, n = 2) were applied to facilitate biopsy in an open low-field scanner. Postcontrast tumor conspicuity was fair in the patient receiving Gd-BOPTA and excellent in both patients receiving ferucarbotran, and biopsy was successful in all cases.

Aged↗

PubMedDate not supplied

The value of hyoscine butylbromide in abdominal MR imaging with and without oral magnetic particles.

PURPOSE: The purpose of this article was to assess the impact of intravenous (IV) anticholinergic hyoscine butylbromide in abdominal magnetic resonance (MR) imaging with oral magnetic particles (OMP) [ABDOS-CAN, Ferristene (USAN), Nycomed Imaging AS, Oslo, Norway]. MATERIALS AND METHODS: In 31 patients with abdominal tumors, T1-weighted spin-echo (SE) images (SE 600/ 15; 1.5 T) were obtained without and with IV hyoscine butylbromide (20 mg) before and after administration of 800 ml of OMP. Two blinded readers assessed motion artifacts, bowel-wall visualization, and lesion delineation on the four sets of T1-weighted images. The two-tailed Wilcoxon paired sample test was used for statistical analysis (p < .05). RESULTS: Hyoscine butylbromide reduced motion artifacts and improved bowel-wall visualization on precontrast and OMP-enhanced images at a statistically significant level (p = 0.0006-0.037). The lowest degree of artifacts was recorded on OMP images with hyoscine butylbromide. OMP with hyoscine butylbromide significantly improved lesion delineation compared to studies without antiperistaltic drug before (p = 0.019) and after OMP administration (p = 0.01). CONCLUSIONS: The authors conclude that the use of IV hyoscine butylbromide is recommended for OMP-enhanced abdominal MR imaging with T1-weighted SE pulse sequences at 1.5 T.

Abdominal Neoplasms↗

PubMedDate not supplied

Growth characteristics and imaging properties of the morris hepatoma 3924A in ACI rats: a suitable model for transarterial chemoembolization.

PURPOSE: For experimental studies investigating modalities and efficacy of transarterial chemoembolization (TACE) in hepatocellular carcinoma (HCC) an animal model resembling the human situation as closely as possible would be appropriate. Specifically, reproducible tumor growth characteristics with the capability for appropriate in vivo imaging to monitor treatment efficacy are required. METHODS: Morris hepatoma 3924A was implanted into the liver of 30 ACI rats. Tumor growth was followed by angiography (n = 10), ultrasound (US, n = 30), native computed tomography (CT, n = 16), and native magnetic resonance imaging (MRI, n = 30) between day 8 and day 36 after implantation. The radiological morphological characteristics were compared with the macroscopic and microscopic histological findings of the explanted tumors. RESULTS: In all 30 animals a solitary liver tumor was found and macroscopically no signs of metastases, ascites, or peritoneal tumor were visible. On histopathological examination tumor sizes ranged between 27 +/- 3 mm(3) (day 8) and 3468 +/- 79 mm(3) (day 36). The first signs of tumor necrosis occurred at day 16. US allowed tumor visualization from day 8, MRI from day 8, angiography from day 10, and CT from day 14. CONCLUSIONS: The tumor model has the potential to be used for the visualization of tumor growth by MRI and US. The potential for monitoring therapeutic effects of TACE needs to be investigated.

Angiography↗

PubMedDate not supplied

Percutaneous transhepatic intraductal biliary sonography for lymph node staging at 12.5 MHz in malignant bile duct obstruction: work in progress.

PURPOSE: To assess the value of intraductal ultrasound (US) for lymph node staging in malignant biliary obstruction. METHODS: Eighteen patients with malignant extrahepatic obstruction were imaged during percutaneous bile duct drainage with a mechanically rotating US transducer at 12.5 MHz. Detectable lymph nodes were classified as malignant when two of three criteria (hypoechoic, rounded, conspicuous margins) were fulfilled. The results were compared with histopathological data in 8 patients and follow-up CT findings in 10 patients. RESULTS: In 15 of 18 patients (83%) malignant lymph node involvement was suspected at intraductal US and in 5 of 18 patients (28%) during CT. Histopathological investigation after operation (n = 8) and follow-up CT studies (n = 10) revealed the presence of malignant nodal involvement in 13 of 18 (72%) patients. The sensitivity, specificity, and accuracy of transhepatic intraductal biliary US in determining merely the presence or absence of malignant lymph nodes without specific topographic assignment were 92%, 40%, and 78%, respectively. CONCLUSION: These preliminary results suggest that intraductal US may develop into a promising adjunctive modality during percutaneous bile duct drainage in patients with suspected malignant regional lymph node involvement.

Adult↗

PubMedDate not supplied

Local administration of ramiprilat is less effective than oral ramipril in preventing restenosis after balloon angioplasty in an animal model.

PURPOSE: To test the hypothesis that local administration of angiotensin converting enzyme (ACE) inhibitor via a microporous balloon catheter would be more effective than oral administration of ACE inhibitor in preventing neointima formation after balloon angioplasty. MATERIALS AND METHODS: Neointima formation was induced by balloon denudation followed by 0.5% cholesterol diet in 29 New Zealand White rabbits. Directly after denudation, local administration of 1.8 mg of ramiprilat (n = 7) or saline (n = 7) with a microporous balloon catheter at a pressure of 3 atm was performed. Both groups additionally received ramipril orally (1 mg/d). Seven animals were treated exclusively with oral ramipril. The control group was fed a 0.5% cholesterol diet and given no medication (n = 8). Six weeks after intervention, the animals were killed and morphometric and immunohistologic analyses were performed. RESULTS: Oral administration of ramipril resulted in a significant reduction of placque area (-66%, P < .05). Oral and local administration of the ACE inhibitor was followed by a nonsignificant reduction of the neointimal area (-17%). Local administration of saline combined with oral ramipril failed to prevent neointimal formation (reduction of 6%, NS). CONCLUSION: Oral administration of ramipril resulted in a significant reduction of neointimal proliferation in New Zealand White rabbits. The possible benefit of an additional administration of local ramiprilat was diminished by an excessive neointimal hyperplasia, which was most likely caused by the inherent vessel trauma with use of the microporous balloon catheter.

Administration, Oral↗

PubMedDate not supplied

[Examination of trabecular bone structures of the foot skeleton with MRI imaging].

AIMS: To assess trabecular density and structures at various cancellous bone sites in the foot using MR imaging. To compare the MRI findings with the bone mineral density (BMD) values obtained by quantitative computed tomography (QCT) in the lumbar vertebrae. MATERIALS AND METHODS: Bone mineral densities were measured by QCT in lumbar vertebrae 1 to 3 in ten patients with suspected osteoporosis. Sagittal images of the feet were obtained from these patients and also from seven healthy volunteers applying spin-echo and gradient-echo MR techniques. RESULTS: MR imaging revealed differences between patients with osteoporosis and individuals with healthy bones. Comparison of MR and BMD data revealed a significant dependence of MR data on the bone density measured by QCT (alpha < 0.05). In addition, a good correlation (r = 0.73) was found between the results of the different MRI techniques. CONCLUSIONS: The MR imaging techniques investigated offer an interesting tool for the non-invasive assessment of bony structures, at least at peripheral locations with yellow bone marrow. To enable reliable application in the clinical routine setting, additional studies are required to identify suitable standardized methods and establish normal ranges.

Adult↗

PubMedDate not supplied

Comparison of 18FDG-PET with CT scans in the evaluation of patients with residual and recurrent Hodgkin's lymphoma.

The reliable assessment of residual masses after treatment as well as of new lesions suspected for relapse remains a diagnostic problem in patients with Hodgkin's disease (HD). The current study compares the results obtained by CT scan to FDG-PET imaging in a blind analysis with respect to the viability of residual masses and in case of suspected relapse. Between 1/94 and 10/99, 47 comparisons of PET and corresponding CT scans - 26 comparisons in 24 patients with residual tumors and 21 comparisons in 20 patients with suspected relapse of HD - were evaluated by independent reviewers blinded to he results of each other. Patients with primary diagnosis had been treated within trials of the German HD Trial study group. Relapsed patients received intensified salvage chemotherapy regimens. PET was assessed visually and by quantifying glucose uptake (SUV). Changes in size of tumor lesions as well as contrast medium enhancement served as criteria for assessment by CT scans. Results were validated either by histologic examination of a resected mass or biopsy (n=17) or by a clinical follow-up over 6 months following treatment (n=30). In 26 cases with residual lesions FDG-PET showed an increased tracer uptake in 8, 7 of which were true positive (TP) and 1 false positive (FP). Eighteen cases were classified as being negative (no viable HD), 17 true negative (TN) and 1 FN. In the blinded reading of the corresponding CT scans, 10 cases with residual lesions were considered to contain vital lymphoma (2 TP, 8 FP). Sixteen CT scans were classified as negative (10 TP, 6 FN). The resulting sensitivity and specificity of PET were 87.5% and 94.4% in contrast to only 25% and 56% for CT scans. The positive and negative predictive values of PET and CT scans were 87.5% and 94.4% and 20% and 62.5%, respectively. In patients with suspected relapse, sensitivity and positive predictive value for the diagnosis of the relapse were 100% and 86%, respectively, yielding the same results for both methods. FDG-PET performed in HD patients with residual masses appears to offer important additional information regarding the presence of viable HD in these residual lesions. In patients with suspected relapse of HD, FDG-PET seems not to offer any information over CT scans. Using SUVs is not superior to visual assessment of PET alone.

Adult↗

PubMedDate not supplied

Lipid selective MR imaging and localized 1H spectroscopy of bone marrow during therapy of leukemia.

In most patients with acute leukemia very low or absent lipid signals from central red bone marrow are detected using magnetic resonance (MR) techniques, in contrast to healthy persons with considerable signals from both, water and lipid protons. The proliferation of the malignant leukemic cells causes the displacement of fat cells in the marrow. This disorder is reversible during successful cytotoxic chemotherapy of acute leukemia: Lipid signals from vertebral bodies arise again due to the replacement of hypercellular leukemic marrow by fat. Different approaches for lipid selective MR imaging and spectroscopy are reported and results from typical examples are demonstrated and discussed. The report is based on examinations of 12 patients with leukemia in follow-up studies, 11 patients with other disorders of bone marrow, and 26 healthy volunteers.

Adolescent↗

PubMedDate not supplied

Lipids in bone tumors assessed by magnetic resonance: chemical shift imaging and proton spectroscopy in vivo.

The methods of fat and water selective magnetic resonance (MR) imaging and localized 1H MR spectroscopy were evaluated in the course of 37 examinations on 27 primary bone tumors. These methods are capable of demonstrating small amounts of lipids inside the tumors and subtle edema in the adacent bone marrow, in contrast to the usually applied spin-echo and gradient-echo sequences providing signals dependent on the total proton density and on the relaxation times. The tumor masses of the malignant tumors were free of signals in the fat selective images, whereas in three out of six osteochondroma fat signals could be detected. Localized MR spectroscopy was more sensitive even to very low lipid content (lipid portion < 0.5%) in the tumors and revealed signals with J-coupling from seven out of 13 malignant tumors.

Adolescent↗