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Biomedical subjects

C D Claussen

Publications and source records attributed to C D Claussen.

At least 235 records · Page 13Linked to original sources
PubMed1996

Functional MR imaging of anomalies of the aorta.

Stenosis of a vessel is a well-known reason for increased resistance leading to lower flow rates. Other anomalies of the shape or additional blood influx are often considered to be less influential on flow dynamics inside the vessel. In this report, examples of irregular flow patterns in the human aorta are presented. The cases were selected from magnetic resonance examinations of 25 volunteers and more than 150 patients with dysfunctions of the heart or anomalies of the thoracic vessels. The protocol for magnetic resonance examinations included black blood imaging performed in the cine mode (with ECG triggering). Even minor modifications of the aortic shape are shown to result in marked disturbances of the laminar flow pattern in some patients. Effects of abnormal curvatures, additional blood influx, stenoses and dilatation of the aorta are demonstrated.

Adult↗
PubMed1995

Magnetization transfer in hemopoietic bone marrow examined by localized proton spectroscopy.

The sensitivity of hemopoietic bone marrow to magnetization transfer is analyzed in 15 healthy volunteers and seven patients with different hematological disorders (inflammation, plasmacytoma, hemopoietic reconstitution after bone marrow transplantation). To obtain sufficient signal-to-noise ratio, a 90 degrees - 180 degrees - 180 degrees double spin echo (PRESS) single voxel spectroscopic method was combined with pulsed magnetization transfer. Several spectra were recorded from each volume element inside the vertebral marrow, alternately with and without prepulses for magnetization transfer. Water signals from marrow with increased content of extracellular water due to inflammation or edema revealed less magnetization transfer effects than marrow with increased intracellular water content due to high cellularity. The preliminary results show magnetization transfer to be a promising tool for the clinically important characterization of the water composition in red bone marrow.

Adult↗
PubMed1995

Adapted techniques for clinical MR imaging of tendons.

To determine whether the echo time of magnetic resonance gradient-echo and spin-echo imaging sequences may be important for the occurrence of high signal strength from tendon with pathological alterations, imaging sequences with sufficient spatial resolution and very short echo times were developed for whole-body imagers with standard gradient system. The sequences were applied on the Achilles tendons of five healthy volunteers and seven patients with achillodynia. Some affected regions inside tendon, probably corresponding with tissue with subtle edema in the collagen bundles were only revealed in images recorded with very short echo times TE < 5 ms, whereas stronger affections and protons in liquids between the fiber bundles were also shown in images with longer echo times TE > 10 ms. Gradient-echo methods allow shorter echo times than spin-echo techniques for a given gradient system of the imager and given spatial resolution. So minimum echo time gradient-echo sequences should be used for sensitive imaging of tendon alterations, because no considerable signal dephasing due to susceptibility effects were found in tendon.

Achilles Tendon↗
PubMed1995

Characterization of bone marrow after transplantation by means of magnetic resonance.

Magnetic resonance (MR) has become a new tool for noninvasive characterization of bone marrow in patients with hematological disorders in the past few years. Experiences gained from 1H MR imaging and spectroscopic investigations in 48 healthy volunteers and more than 130 patients with hematological disorders are reported and interpreted. Twenty-four of the patients underwent bone marrow transplantation (BMT) before the MR examinations. The findings in these studies provided noninvasive characterization and monitoring of vertebral marrow after BMT. Specifically, MR techniques were found to be suitable for studies of different aspects in physiological and pathological alterations of bone marrow: The water content within the marrow can be analyzed by chemical-shift selective-imaging techniques with good spatial resolution. Spectroscopic methods also allow more sensitive quantification of the signal fractions, as well as separate evaluation of the relaxation times of water and lipids. Relaxometry might be useful to characterize the cellular and extracellular portions of water molecules. Furthermore, the distribution of the magnetic field within small-volume elements of vertebral marrow can be measured. The field distribution is influenced by the trabecular density and the composition of the marrow. High amounts of hemosiderin in the marrow result in clearly broadened field distributions, demonstrated by increasing line widths in MR proton spectra. Magnetic resonance techniques can be used to assess not only the cellularity of the bone marrow, but also metabolic alterations in this compartment which result from cytotoxic treatment or immunological processes.

Bone Marrow↗
PubMed1995

[Dynamic 3D MR mammography using a rapid gradient-echo sequence].

Up to now, MR mammography is performed by two different methods: 2-D techniques with high temporal resolution and 3-D techniques with high spatial resolution. This article investigates whether a dynamic examination of the breast using a novel 3-D-gradient-echo sequence is feasible with sufficient spatial and temporal resolution. MR imaging was performed on a 1.0 Tesla imager using a gradient field strength of 15 mT/m. Phantom measurements were done to evaluate the correlation between signal intensity and contrast medium concentration for different sequences. Subsequently, 40 patients with 22 histologically verified lesions were examined using the double breast coil and a novel FLASH3D sequence (TR/TE/fa 9/3/50 degrees). Reading of the films in standardized documentation, multiplanar reconstruction (MPR), calculation and maximum intensity projection (MIP) of subtraction images as well as signal-to-time curve calculations in selected ROIs were performed for data evaluation. In the phantom measurements the FLASH3D-9/3/50 degrees sequence yielded the best correlation between signal intensity and Gd-DTPA concentration. The sequence provided good visualization even of small lesions. The 3-D postprocessing procedures facilitated the detection and localization of the lesions. Therefore, the new FLASH3D-9/3/50 degrees sequence enables a dynamic 3-D examination of the breast with a sufficient spatial and temporal resolution.

Adolescent↗
PubMed1995

[Echo contrast agents for the color Doppler sonographic diagnosis of deep femoral venous thrombosis].

PURPOSE: Evaluation of an echo contrast medium (Echovist) for color-coded duplex sonography of deep venous thrombosis of the thigh. MATERIAL AND METHODS: In 19 patients with deep vein thrombosis of the thigh, diagnosed by contrast phlebography, 22 color-coded duplex sonography studies were performed for flow analysis at the top of the thrombus. During the studies 8.5 ml echo contrast medium were injected in an ipsilateral vein at the back of the foot. The flow signals of the non-enhanced color coded duplex sonography were compared with those of the echo enhanced study for differentiation between floating thrombi from those adherent to the vein wall. RESULTS: The echo-enhanced color-coded duplex sonography showed a significant increase in detection of perfusion at the top of the thrombus in comparison with non-enhanced color-coded duplex sonography (p < 0.01). 9 thrombi were regarded as wall adherent after the native study, 7 of these could be identified as floating thrombi by echo-enhanced color-coded duplex sonography. CONCLUSION: Echo-enhanced color-coded duplex sonography yields a significant increase of diagnostic information in certain findings of the non-enhanced color-coded duplex sonography differentiating between floating thrombi and wall adherent thrombi in the deep venous system of the thigh.

Adult↗
PubMed1995

[High-resolution magnetic resonance tomography of the anal sphincter using an intravaginal surface coil].

PURPOSE: To assess the visualisation of the anal sphincter by means of an intravaginal surface coil. METHODS: MR imaging was performed using a 1.0 T unit. In 10 females (6 nullipara, one primipara without and three primipara with postpartum faecal incontinence) a surface coil, originally designed for endorectal use, was placed into the vagina. Transverse oblique T1-weighted spin echo and double echo turbo spin echo sequences with T2- and proton density-weighting were acquired parallel to the puborectal, rectococcygeal and anorectal planes. Three readers analysed the images in consensus. RESULTS: The anatomic structures of the external and internal sphincter as well as the mucosa were differentiated in all cases with a good contrast. The best results were yielded by the proton density weighting. In one case of faecal incontinence a sphincter defect after repair of a complete rupture of the anal sphincter was shown. In another case irregularities in the structure of the external sphincter and perineum were visualised. CONCLUSION: Intravaginal surface coil imaging seems a well-tolerated novel method for the evaluation of the anal sphincter tissues in truly anatomical states. Due to its capability to depict subtle tissue structures as well as pathologic irregularities, it might become a potential tool in the diagnosis and operation planning of postpartal faecal incontinence.

Adult↗
PubMed1995

[Value of the AMBER system in interstitial lung changes].

PURPOSE: To evaluate the diagnostic value of the AMBER technique in the diagnosis of interstitial lung disease. METHODS: A prospective comparison of conventional and AMBER chest radiographs of 52 patients was performed using HR-CT as a gold standard on the same day. ROC analysis based on the results of 5 observers was carried out to quantify the diagnostic value of both chest radiograph techniques. RESULTS: The ROC area for the AMBER system (0.860) showed statistically significant superiority in comparison to the conventional technique (0.828). This was mainly due to the better sensitivity of the AMBER system (65.3%) compared to the conventional chest radiographs (39.8%) within the lung regions superimposed by the diaphragm or the mediastinum. No difference between both methods was observed within the lung regions without superimposion. CONCLUSION: AMBER technique improved conventional chest radiography in the diagnosis of interstitial lung disease due to superiority in the superimposed lung regions.

Evaluation Studies as Topic↗
PubMed1995

[Spiral CT and CT angiography after coronary bypass surgery].

AIM: Evaluation of spiral-CT and CT-angiography for imaging of venous and arterial coronary bypass grafts during the early postoperative period. PATIENTS AND METHODS: In 198 patients suffering from coronary heart disease, 583 aortocoronary venous grafts (ACVG), 70 arterial grafts and 24 jumped grafts were investigated 9-15 days following coronary surgery. In 57 patients the results were compared to arterial DSA and reconstructive CT-angiography. RESULTS: At arterial DSA 93% of ACVG and 100% of arterial grafts were patent. Spiral-CT demonstrated 104 of 105 ACVG (99%) and 20 of 29 arterial grafts (69%) correct patent. All occluded ACVG (n = 8) were detected. 90% of ACVG but only 32% of arterial grafts were visualised completely over long segments. Imaging of jumped grafts was insufficient. In CT-angiography artificial vessel stenoses impaired correct visualisation of graft morphology. CONCLUSIONS: Spiral-CT allows sufficient differentiation of patent and obstructed ACVG during the early postoperative period. Diagnostic of arterial grafts is of lower accuracy. For CT angiography of venous and arterial coronary grafts further improvements are necessary.

Angiography↗
PubMed1995

Comparison of magnetic resonance imaging methods for examinations of abdominal aortic aneurysms.

RATIONALE AND OBJECTIVES: Different magnetic resonance imaging techniques were compared with respect to available anatomic information regarding abdominal aortic aneurysms (AAA) and regions involved in thrombosis. METHODS: Twenty patients with AAA were examined by turbo spin-echo (TSE) imaging of coronal and transverse slices, resulting in black blood images. Bright blood imaging was performed using a spoiled gradient-echo sequence with gradient moment nulling. Sets of 25 to 50 thin slices were recorded sequentially in a single slice mode using coronal and transverse orientation. Both sets of bright blood images were reconstructed by maximum intensity projection. RESULTS: In all patients, the size and shape of the AAA could better be assessed by the TSE images than by the gradient-echo images. In contrast, reliable differentiation of thrombotic areas and of the perfused lumen was possible in only 56% of the slices recorded by TSE imaging but in 94% of the gradient-echo images. The two-dimensional inflow technique provided clearly higher sensitivity even to slow blood flow than TSE imaging. Maximum intensity projection reconstructions from sets of coronal two-dimensional inflow images often did not depict the lower part of the AAA because of saturation effects, whereas sets of transverse slices provided complete angiograms of the aortoiliac vascular tree. DISCUSSION: At this time, no single magnetic resonance method can provide all essential information. A comprehensive examination should include TSE imaging for topographic assessment and transverse two-dimensional inflow imaging for analysis of thrombotic areas.

Aged↗
PubMed1995

Normal bone marrow in the sacrum of young adults: differences between the sexes seen on chemical-shift MR imaging.

OBJECTIVE: Age-related changes in the distribution of fatty and nonfatty bone marrow in the pelvis and femur are well recognized. However, mapping not only of age-related MR appearance of normal bone marrow but also of potential variations in females versus males is necessary to differentiate normal findings from marrow disease. Accordingly, we studied possible sex-related differences in the MR imaging appearance of sacral bone marrow in young adults. SUBJECTS AND METHODS: A population of 21 healthy men and 21 healthy women (17-42 years old) was prospectively studied with chemical-shift pulse sequences. MR imaging (1.5 T) of the sacrum was done with frequency-selective fat images (SENEX [selective nonexcitation] 300/27) and water images (SENEX 1000/27) by using an elliptical surface coil. Two independent observers compared the signal intensity of sacral marrow with the signal of fatty tissue planes adjacent to the sacrum (fat images) and the signal of gluteus muscle (water images). T2 relaxation times were estimated by using a two-parametric monoexponential fit on SENEX 1000/27 and SENEX 1000/54 images. RESULTS: In both sexes, fat MR images showed a higher fat content and greater heterogeneity in the bone marrow of the lateral masses than in the vertebral bodies of the sacrum (p < .05). Yellow marrow in the lateral masses of the sacrum appeared brighter in men than in women (p < .05). The heterogeneity of fatty marrow did not differ significantly between the sexes. On water MR images, the signal intensity of the sacrum was higher in women (p < .05). T2 relaxation times were longer in nonfatty marrow with a high water signal intensity (41.8 +/- 5.5 msec versus 33.4 +/- 2.6 msec p < .01). CONCLUSION: Our findings show that the normal appearance of the sacral bone marrow depicted on chemical-shift MR imaging differs between young men and women. Awareness of these differences is important to avoid misinterpretation of normal MR findings seen in patients in this age group.

Adolescent↗
PubMed1995

[Modern radiologic diagnosis for the ENT physician].

Radiologic diagnosis has acquired an increased importance in head and neck diseases since the introduction of sectional imaging techniques. In addition to clinical and endoscopic examinations, CT has become the standard modality for TNM staging of malignant diseases. CT is also a basic tool in diagnosing benign diseases localized in or infiltrating into the deep head and neck regions. Ultrasound is widely available and is now well established in the diagnosis of superficial pathologies. Magnetic resonance is the newest imaging modality and is being increasingly used in clinical practice. By avoiding ionizing radiation MRI provides an improved method for contrast studies and enables high-quality multiplanar imaging. The applications of this method are still expanding with ongoing refinements of MR imaging techniques. Conventional radiological methods remain limited to a few indications. Radiation dose and cost have now required replacement of traditional step-by-step diagnostic methods by the one method that can meet most requirements in a single examination.

Humans↗
PubMed1995

Magnetic resonance bone densitometry. Comparison of different methods based on susceptibility.

RATIONALE AND OBJECTIVES: Three different magnetic resonance techniques for the assessment of the density of trabecular bone are presented and compared. METHODS: All methods are based on the susceptibility difference between marrow and bony components. Localized spectroscopic (PRESS single voxel spectroscopy) and two different imaging approaches (FLASH gradient echo imaging and MAGSUS imaging) are demonstrated to be sensitive to the trabecular structures on application to the distal femur of a healthy volunteer. This region was chosen because a continuous rarefication of the trabecular density from the epiphysis to the metaphysis occurs physiologically. In addition, results from the heel-bones of five young healthy volunteers were compared with data from three patients with severe osteoporosis. RESULTS: All methods allowed differentiation between the two groups. Advantages and disadvantages of the methods concerning spatial resolution, preparation and measuring time, necessity of postprocessing, problems with shim adjustment, and occurrence of several chemical shift components are reported. The MAGSUS technique combines simple application and avoidance of postprocessing for at least qualitative assessment of bone density with sufficient spatial resolution. CONCLUSIONS: A reliable assessment of osteoporosis by magnetic resonance is possible in peripheral marrow regions of adults. Further studies are needed to establish standard measuring protocols.

Adult↗
PubMed1995

[High intensification film-screen systems in thoracic diagnosis. A clinical comparative study].

OBJECTIVE: The quality of chest images was evaluated for a conventional screen-film system, a new asymmetric screen-film system, and a new uv screen-film system. MATERIALS AND METHODS: 138 chest radiographs (69 p.a., 69 lateral) obtained with three different high intensification screen-film combinations were compared. Film density and film contrast were measured. Three readers graded the image quality according to 16 criteria. RESULTS: The asymmetric film-screen combination Insight HC showed the lowest film contrast, the best exposure range, and a elevated film density in the mediastinal area. The asymmetric screen-film system was ranked by all three observers as being substantially better in image quality. CONCLUSION: Compared to conventional screen-film systems, the new screen-film systems can improve the image quality of chest radiographs. Therefore, the new high intensification screen-film combinations can be used as a low cost alternative to the Amber technique and digital radiography.

Humans↗
PubMed1994

Localized MR 1H spectroscopy reveals alterations of susceptibility in bone marrow with hemosiderosis.

A noninvasive investigation of the structure of hemopoietic bone marrow is based on the determination of the magnetic field distribution within small volume elements in vertebral bodies by localized 1H MR spectroscopy. In patients with hematological diseases the status of the bone marrow was found to considerably influence the homogeneity of the magnetic field in trabecular bone in vivo. The line widths of the 1H signals were evaluated in follow-up studies during initial chemotherapy of eight patients with leukemia. Intraindividual comparison revealed significant broadening of the field distribution after a few weeks of cytotoxic treatment in five of the patients. Additionally, 19 patients after bone marrow transplantation showed significantly broader field distributions in the lipid signals than 13 matched healthy volunteers. These alterations of the microscopic field homogeneity were not caused by trabecular density effects. Iliac crest biopsies revealed high amounts of hemosiderin in the cases with broadened line widths. Ten of the 19 patients after bone marrow transplantation showed high amounts of hemosiderin and broad lines in the spectra. The content of hemosiderin of the other patients was not significantly increased.

Acute Disease↗
PubMed1994

Pulmonary nodules in spiral volumetric and single slice computed tomography.

Single slice acquisition of conventional CT and volume scanning of spiral volumetric CT are compared in terms of detection and assessment of pulmonary nodules. Spiral CT is supposed to be superior to conventional CT in detecting all lung nodules by scanning the complete lung volume, while conventional CT may miss nodules due to inconsistent levels of inspiration for single slices. Different technical procedures of spiral CT may change the imaging of nodules and other findings. Fifty-two patients with known or suspected lung nodules were examined by conventional CT and spiral CT. Number and size of lung nodules and imaging of other pulmonary findings were registered independently by two radiologists. Spiral CT showed 15 lung nodules not seen on conventional CT, and missed one nodule. Spiral CT imaging of nodules was superior in some cases (characterisation of benign nodules) because complete scanning provided more information than conventional CT. It was worse in some cases (small nodules, fibrosis, small pleural effusion) due to the greater partial volume effect and less mAs. Technically improved spiral CT with longer scanning facilities and a 180-degree algorithm may be able to replace conventional CT for this indication.

Humans↗
PubMed1994

Eosinophilia-myalgia syndrome: findings at MR imaging and proton spectroscopy of the lower leg.

Five magnetic resonance (MR) studies of the lower leg were performed in three patients with eosinophilia-myalgia syndrome (EMS). The 1H spectroscopic and imaging findings were compared with seven examinations of age-matched healthy controls. Standard imaging with proton density-, T1-, and T2-weighted spin-echo (SE) sequences at 1.5 T showed marked atrophy of the calf muscles and slightly increased signal strength of muscle tissue in T2-weighted SE images. The application of frequency selective chemical shift imaging (SENEX) exhibited skin changes similar to those of scleroderma with increased water content and thickened cutis in the water selective images. In one patient the tibialis muscles showed irregular structures, but no fatty degeneration as demonstrated in the fat selective images. Proton signals from volume elements of (20 mm)3 within the soleus and gastrocnemius muscle were recorded by the PRESS localization method. A reduction of the creatine/water and the choline/water ratios was found in the 1H spectra from the EMS patients compared to the controls. Localized 1H spectroscopy exhibited modified distributions of the lipid signals in two EMS patients with slightly elevated signals from unsaturated fatty acids. The transverse relaxation of choline and creatine signals was accelerated in both examinations of one patient compared with the healthy controls.

Adult↗