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Biomedical subjects

E Grabbe

Publications and source records attributed to E Grabbe.

At least 73 records · Page 4Linked to original sources
PubMed1999

[The MR imaging of the vena cava system: a comparison of different technics].

PURPOSE: To evaluate the feasibility and diagnostic value of there different MR angiographic imaging techniques for the assessment of the central body veins. METHODS: 25 investigations of the central veins were performed with an ECG-triggered black-blood HASTE sequence, a segmented 2D cine FLASH sequence and a contrast-enhanced 3D-FISP angiography. The results of the MR-studies were compared with those of spiral CT or venography. RESULTS: The HASTE sequence was suitable for the assessment of the complete central body vein system also in less cooperative patients. The combination with the 2D cine FLASH sequence enabled the detection of intravascular tumors or thromboses and the graduation of subtotal occlusions. The involvement of the right atrium was proved in 2/2 cases. The attachment at the vessel wall could be assessed. Only contrast-enhanced 3D MRA visualized the renal veins and complex collaterals sufficiently. But this procedure has to be done in a strict breath-hold technique. CONCLUSION: In the present study all thromboses and tumor cones of the central body veins were detected with the combined use of HASTE/Cine FLASH. For the assessment of complex collaterals and the renal vessels the application of contrast-enhanced 3D-MRA techniques is necessary.

Adolescent↗
PubMed1999

[Slice sensitivity profile and image pixel noise of multi-slice spiral CT in comparison with single slice spiral CT].

PURPOSE: Presentation and evaluation of slice sensitivity profile and pixel noise of multi-slice CT in comparison to single-slice CT. METHODS: Slice sensitivity profiles and pixel noise of a multi-slice CT equipped with a 2D matrix detector array and of a single-slice CT were evaluated in phantom studies. RESULTS: For the single-slice CT the width of the slice sensitivity profiles increased with increasing pitch. In spite of a much higher table speed the slice sensitivity profiles of multi-slice CT were narrower and did not increase with higher pitch. Noise in single-slice CT was independent of pitch. For multi-slice CT noise increased with higher pitch and for the higher pitch decreased slightly with higher detector row collimation. CONCLUSIONS: Multi-slice CT provides superior z-resolution and higher volume coverage speed. These qualities fulfill one of the prerequisites for improvement of 3D postprocessing.

Artifacts↗
PubMed1999

[Computer-assisted visualization of digital mammography images].

PURPOSE: In a clinical study, the feasibility of using a mammography workstation for the display and interpretation of digital mammography images was evaluated and the results were compared with the corresponding laser film hard copies. MATERIALS AND METHODS: Digital phosphorous plate radiographs of the entire breast were obtained in 30 patients using a direct magnification mammography system. The images were displayed for interpretation on the computer monitor of a dedicated mammography workstation and also presented as laser film hard copies on a film view box for comparison. The images were evaluated with respect to the image handling, the image quality and the visualization of relevant structures by 3 readers. RESULTS: Handling and contrast of the monitor displayed images were found to be superior compared with the film hard copies. Image noise was found in some cases but did not compromise the interpretation of the monitor images. The visualization of relevant structures was equal with both modalities. Altogether, image interpretation with the mammography workstation was considered to be easy, quick and confident. CONCLUSIONS: Computer-assisted visualization and interpretation of digital mammography images using a dedicated workstation can be performed with sufficiently high diagnostic accuracy.

Aged↗
PubMed1999

[The evaluation of experimentally induced injuries to the upper cervical spine with a digital x-ray technic, computed tomography and magnetic resonance tomography].

PURPOSE: To compare digital X-ray, CT, and MRI in the evaluation of ligamentous and osseous lesions in upper cervical spine specimens after artificial craniocervical injury with the findings of macroscopic preparation. MATERIALS AND METHODS: A rotation trauma of defined severity was applied to 19 human corpses. After dissection of the neck specimens, digital X-ray (DIMA Soft P41, Feinfocus), conventional and helical CT (CTi, High Speed, GE, collimation 1 mm; pitch 1.0), and MRI were performed from the skull base to C3. The findings were correlated with the macroscopic results of preparation. MR (Magnetom Vision, Siemens) imaging was obtained with a 1.5 T system using 2D- and 3D-sequences. RESULTS: Preparation revealed 6 fractures of the vertebral bodies, 5 fractures of the dens axis, 1 fracture of the arcus anterior of the atlas, 4 osseous flakes at the occipital condylus, and 6 lesions of the alar ligaments. Digital radiography showed all fractures and 4 osseous flakes at the occipital condylus. With conventional and helical CT, all fractures and all ruptured alar ligaments could be detected. 2D MRI depicted 9 of the fractures and 3D MRI showed fractures. With 2D MRI, 2 of the 4 osseous flakes at the condylus could be detected and with 3D MRI one occipital condylus fracture could be depicted. Ligamentous injuries were visualized by 2D MRI in 2 of 6 cases and by 3D MRI in one case. CONCLUSIONS: In post-mortem studies, CT was superior to MRI in the visualization of osseous and ligamentous injuries after trauma of the upper cervical spine. However, these results are not transferable to patients with rotation injury in general.

Aged↗
PubMed1999

[The optimization of MR cholangiopancreatography].

PURPOSE: To improve the image quality of magnetic resonance cholangiopancreatography (MRCP) by modification of examination conditions. MATERIALS AND METHODS: MRCP of 72 patients was performed with a 1.5 T system (Magnetom Vision, Siemens, 25 mT/m) using two breath-hold techniques, half-fourier acquisition with multislice T2-WI HASTE in MIP technique, and single shot T2-WI turbo-spin-echo (RARE) with different slice thicknesses. The effects of n-butylscopolamine were assessed. Furthermore, oral contrast agents [barium sulfate, Fe(II)-gluconate, Fe(II,III)-oxide] in various concentrations were used. The slice thickness was varied for the RARE sequence (3-7 cm). RESULTS: N-butylscopolamine had no influence on image quality. Improvements could be attained by variation of the slice thickness. A significant reduction of disturbing background noise was obtained by oral application of iron gluconate, or iron oxide-containing contrast media. Similar improvements were achieved with barium sulfate. CONCLUSIONS: Variation of slice thickness allows an improvement of MRCP quality. Oral contrast media improve the image quality of MRCP. The expense of contrast media may be a determinant of choice.

Administration, Oral↗
PubMed1999

[Dental CT: image quality and radiation exposure in relation to scan parameters].

PURPOSE: To develop a scan protocol for dental-CT which guarantees good image quality at the lowest possible radiation dose. METHODS: In an experimental investigation Dental-CT (HSA, GE, Milwaukee, USA) of the mandible of two human skeletons positioned in a water tank were performed in order to define the most advantageous scan protocol. Tube currents ranged from 40 to 200 mA and the scan technique was modified (axial mode or helical mode with pitches of 1 to 3 and corresponding increments of 0.4 to 1.0 mm). 39 patients underwent a dental-CT with decreased current (80 mA) in the helical scan mode (pitch 2, slice thickness 1 mm). Dose measurements were performed for two different scan protocols (A: axial, 130 mAs, B: helical, 80 mA, pitch 2). RESULTS: The preliminary investigations of image quality showed only a minor effect of the applied current. For the helical scan mode, pitches of more than 2 impaired image quality. A low increment had no advantages. There were no disadvantages in clinical practice using protocol B with decreased tube current. Absorbed radiation dose of dental CT performed with protocol B was decreased to one third in comparison to protocol A. CONCLUSIONS: A scan protocol with a low tube current (e.g., 80 mA, for a rotation time of 1 s) and a helical scan mode (e.g., for a slice thickness of 1 mm with a pitch of 2 and an increment of 1 mm) is recommended for performing dental-CT.

Adult↗
PubMed1999

[Instability of spinal fractures--therapeutic relevance of different classifications].

PURPOSE: To investigate if the assessment of spinal fracture stability according to the Magerl classification permits a better therapy decision than using the Denis 3-column model. MATERIAL AND METHODS: The X-ray and CT images of 99 consecutive patients treated for thoracolumbar spine fractures were analysed and the fractures were classified according to the above mentioned classifications. Using the 3-column model, the involvement of two or more columns was considered as unstable, whereas the fracture types A3.2, A3.3, B and C of the Magerl classification were defined as unstable. The stability evaluation was compared with the therapy decision and outcome. RESULTS: According to the 3-column model, 23 of 53 fractures which were classified as unstable were operated. Only five of the 30 conservatively treated unstable fractures showed a reduced healing process. The 46 stable fractures were treated conservatively with good results. Using the Magerl classification, 21 of the 28 unstable fractures were operated and 4 of the remaining 7 cases showed a reduced healing process. Of the 71 stable fractures only 2 were operated and in one patient minimal neurological symptoms occurred. CONCLUSION: The Magerl classification enables a more exact definition of stable and unstable spinal fractures.

Adolescent↗
PubMed1999

[Direct digital magnification mammography with a large-surface detector made of amorphous silicon].

PURPOSE: To investigate the image quality of a new direct digital mammography system using a large-area amorphous silicon X-ray detector in a phantom study. MATERIALS AND METHODS: The contrast-detail resolution as a function of the tube voltages, the magnification factors and the mean glandular doses were investigated using dedicated test objects. RESULTS: The contrast-detail resolution was significantly improved in comparison with conventional screen-film mammography. Usually, the doses necessary to obtain these high-quality survey mammograms were smaller. CONCLUSIONS: By combining the direct magnification technique and a digital flat panel detector the limited spatial resolution of such image receptors can be overcome. With this direct digital mammography technique, a digital image was directly captured without an intermediate step of optical or mechanical scan.

Equipment Design↗
PubMed1999

[Diagnostic imaging in hepatosplenic candidiasis].

Hepatosplenic candidiasis is a severe complication encountered in immuno-compromised patients. Different imaging techniques can establish the diagnosis. After an introduction to the pathophysiological and clinical principles, the role of plain radiography, radionuclide scans, ultrasound, computed tomography and magnetic resonance imaging is discussed.

Candidiasis↗
PubMed1999

Helical computed tomography of renal lesions.

Helical computed tomography is a new technique that acquires a volumetric data set of both kidneys within a single breath-hold. It has proved to be superior to conventional computed tomography. Multiphasic helical computed tomography after the administration of contrast material shows advantages concerning the detection and characterization of renal lesions and the preoperative staging of renal cell carcinomas. The proper scan protocol for a sufficient examination of the kidneys is described as well as its diagnostic value. The characteristic computed tomography morphology of benign and malignant renal lesions is reviewed and the advantages of helical computed tomography are illustrated.

Animals↗
PubMed1999

Hepatic blood supply: comparison of optimized dual phase contrast-enhanced three-dimensional MR angiography and digital subtraction angiography.

PURPOSE: To optimize and determine the value of dual-phase contrast material-enhanced three-dimensional (3D) magnetic resonance (MR) angiography for preoperative evaluation of the blood supply to the liver. MATERIALS AND METHODS: Dual phase 3D MR angiography of the hepatic arteries and portal vein was performed in 140 patients. In 80 patients, the value of fat saturation, digital image subtraction, an anticholinergic agent, and a high-caloric meal were evaluated. In the next 60 patients, MR angiographic and digital subtraction angiographic (DSA) image quality and diagnostic value were compared. RESULTS: Fat-saturated images were of significantly better quality (P < .01) than non-fat-saturated images. Digital image subtraction was useful in only 23 of 40 patients. The injection of an anticholinergic agent was superfluous, whereas administration of a high-caloric meal helped in demonstration of the superior mesenteric artery and portal vein. Classification on MR angiograms of the arterial blood supply was correct in 57 of 60 patients. All arterial and portal venous lesions were seen on MR angiograms, and MR angiograms had a significantly higher subjective image-quality ranking than did DSA images in the evaluation of the portal vein (P < .05). CONCLUSION: Fat saturation and use of a high-caloric meal improve the results of MR angiography of hepatic vessels. MR angiography was comparable to DSA for evaluation of the arterial system and was superior for demonstration of the portal vein; therefore, MR angiography could replace intraarterial DSA.

Angiography, Digital Subtraction↗
PubMed1999

Breast carcinoma: effect of preoperative contrast-enhanced MR imaging on the therapeutic approach.

PURPOSE: To determine if magnetic resonance (MR) imaging can help determine the therapeutic approach in women with breast cancer. MATERIALS AND METHODS: Preoperative contrast-enhanced MR imaging of the breast was performed in 463 patients with probably benign lesions (n = 63), suspicious lesions (n = 230), or lesions highly suggestive of malignancy (n = 170) per established clinical, mammographic, and/or ultrasonographic (US) criteria. T1-weighted fast low-angle shot MR imaging was performed before and after administration of gadopenetetate dimeglumine. MR imaging findings were correlated with other imaging results and histopathologic findings. Special attention was paid to multifocality and multicentricity. RESULTS: Histopathologic analysis revealed 143 benign and 405 malignant lesions. The sensitivity, specificity, and accuracy were 58%, 76%, and 62% for clinical examination; 86%, 32%, and 72% for conventional mammography; 75%, 80%, and 76% for US; and 93%, 65%, and 85% for contrast-enhanced MR imaging. Multifocality in 30 of 42 patients, multicentricity in 24 of 50 patients, and additional contralateral carcinomas in 15 of 19 patients were depicted with MR imaging alone. Due to the MR imaging findings, therapy was changed correctly in 66 patients (14.3%); unnecessary open biopsy was performed in 16 patients (3.5%). CONCLUSION: Contrast-enhanced MR imaging of the breast is highly sensitive for invasive breast cancer. MR imaging may reveal unsuspected multifocal, multicentric, or contralateral breast carcinoma and result in therapy changes.

Adult↗
PubMed1998

Structural and functional properties of two mutants of lecithin-cholesterol acyltransferase (T123I and N228K).

Two naturally occurring mutants of human lecithin-cholesterol acyltransferase (LCAT), T123I and N228K, were expressed in COS-1 and Chinese hamster ovary cells, overproduced, and purified to homogeneity in order to study the structural and functional defects that lead to the LCAT deficiency phenotypes of these mutations. The mutants were expressed and secreted by transfected cells normally and had molecular weights and levels of glycosylation similar to wild type LCAT. The purified proteins (>98% purity) had almost indistinguishable structures and stabilities as determined by CD and fluorescence spectroscopy. Enzymatic activities and kinetic analysis of the pure enzyme forms showed that wild type LCAT and both mutants were reactive with the water-soluble substrate, p-nitrophenyl butyrate, indicating the presence of an intact core active site and catalytic triad. Both the T123I and N228K mutants had markedly depressed reactivity with reconstituted HDL (rHDL), but T123I retained activity with low density lipoprotein. To determine whether defective binding to rHDL was responsible for the low activity of both mutants with rHDL, the equilibrium binding constants were measured directly with isothermal titration calorimetry and surface plasmon resonance (SPR) methods. The results indicated that the affinities of the mutants for rHDL were only about 2-fold lower than the affinity of wild type LCAT (Kd = 2.3 x 10(-7) M). Together, the activity and equilibrium binding results suggest that the T123I mutant is defective in activation by apolipoprotein A-I, and the N228K mutant has impaired binding of lipid substrate to the active site. In addition, the kinetic binding rate constants determined by the SPR method indicate that normal LCAT dissociates from rHDL, on average, after one catalytic cycle.

Animals↗
PubMed1998

Magnification survey and spot view mammography with a new microfocus X-ray unit: detail resolution and radiation exposure.

The aim of our study was to evaluate a mammography unit capable of magnification of up to fourfold at an equivalent or lower dose than with current systems. A prototype mammography tube with an electron-beam-focusing technology resulting in a focal spot size of 40-120 micro m was combined with a highly intensifying screen-film system. To evaluate contrast-detail resolution, phantom radiographs were performed with the prototype magnification mammography system using a magnification factor of 1.7 for survey views and a magnification factor of 4.0 for spot views. They were compared with unmagnified survey views and magnification spot views (magnification factor 1.9) of a state-of-the-art mammography system. The radiation exposure was measured and mean glandular doses were calculated. The contrast-detail resolution with both prototype (m = 1.7) and conventional (m = 1.1) survey views was equivalent while the entrance dose and the mean glandular dose were approximately 50 % lower with the prototype. For spot views, the contrast-detail resolution was substantially higher for the prototype than for conventional magnification while the dose was equivalent. Dose reduction and improved detail resolution are possible with this new technology.

Acrylic Resins↗
PubMed1998

Electrocardiograph-triggered two-dimensional time-of-flight versus optimized contrast-enhanced three-dimensional MR angiography of the peripheral arteries.

We determined whether the accuracy of magnetic resonance angiography (MRA) in the peripheral run-off vessels can be improved by using contrast-enhanced (CE) three-dimensional (3D) technique in comparison to electrocardiograph (ECG)-triggered two-dimensional (2D) time-of-flight (TOF) technique. In a prospective study 20 patients with occlusions of the pelvic and/or femoral arteries underwent a CE 3D MRA (repetition time (TR): 5 ms, (TE) echo time: 2 ms, flip angle (FA): 30 degrees ) and an ECG-triggered 2D time-of-flight (TOF) technique (TR: 408 resp. 608 ms, TE: 7 ms, FA: 70 degrees) of the run-off vessels on a 1.5 T MR system. Each patient received a contrast material volume of 0.15 mmol/kg of body weight of gadolinium (Gd)/DTPA using an automatic injector. The tube system to the patient was flushed by 50 mL of a saline solution applied with the same injection rate as the contrast material administration. The start of the 3D MR sequence was tailored individually to the applied contrast material after determination of circulation times by a prior bolus. All patients underwent each conventional or digital arteriography for comparison, as well. The visualization of the run-off vessels was ranked on a scale of 0-3 (0 = poor, 1 = fair, 2 = good, 3 = excellent) by three blinded reviewers. They also graded the vascular segments as either occluded or significantly altered (>50% reduction in diameter) or free of significant stenosis. CE 3D MRA was significantly faster in imaging the run-off vessels in comparison to the ECG-triggered 2D TOF technique. All 160 vascular segments were visualized with the 3D method, whereas only 142/160 segments were seen with 2D technique. The resulting image quality ranking of all vascular segments was significantly higher (p < 0.05) using CE 3D MRA (2.8) than with the 2D TOF technique (2.4). The detection of the stenoses was possible with both techniques. The grading of seven of seven stenoses was correct with 3D method and in five of seven cases with the 2D TOF technique. All vessel occlusions were detected by using both techniques. Small collaterals were visualized in more detail with the CE 3D MR angiography. These data demonstrate an improvement in image quality and accuracy of MRA of the peripheral arteries using a CE 3D technique in comparison to an ECG-triggered 2D TOF sequence.

Contrast Media↗