Biomedical subjects

N Hosten

Publications and source records attributed to N Hosten.

At least 91 records · Page 5Linked to original sources

PubMed1998

[Use of high resolution color Doppler sonography in diagnosis of temporal arteritis].

PURPOSE: To define sonographic signs of arteritis temporalis using color coded duplex sonography. METHODS: 20 patients with clinically suspected temporal arteritis were examined with color coded Doppler ultrasound prior to temporalis biopsy. The investigation included the temporal artery on both sides and documentation was performed with color prints of the longitudinal orientation of both temporal arteries. All patients had an unilateral biopsy of the temporal artery. RESULTS: 6/20 patients had histologically confirmed temporal arteritis. All patients showed a paravasal zone of lower echogenicity (halo-sign) along the temporal artery. 12/14 patients without temporal arteritis showed no halo-sign. However, a halo-sign was found in 2/14 patients without temporal arteritis which could not be distinguished from the halo-sign observed in patients with temporal arteritis. CONCLUSIONS: A halo-sign could be detected in the majority of patients with arteritis temporalis in concordance with the recent published findings of Schmidt et al. However, a definite specificity of this halo-sign must be rejected.

Aged↗

PubMed1998

Do ultrasonic contrast agents artificially increase maximum Doppler shift? In vivo study of human common carotid arteries.

The aim of this study was to establish whether an increase of maximum Doppler shift occurs in the human common carotid artery after the administration of Levovist, an ultrasonographic echo enhancer. Twenty common carotid arteries of 10 patients were examined. Spectral Doppler waveform examinations were performed before and after administration of Levovist using an Acuson 128 XP 10 and a 7.0 MHz transducer probe. Time averaged mean velocity, peak velocity, maximum Doppler shift, and spectral Doppler indices (pulsatility index, resistive index, systolic-diastolic ratio) were assessed. No significant changes in any of the measured parameters, including maximum Doppler shifts, peak velocity (P = 0.35, Wilcoxon rank sum test), pulsatility indices (P = 0.70), resistive indices (P = 0.98), or other spectral indices, were found. We conclude that an increase in Doppler shift does not inevitably occur after the administration of a signal enhancer when examining the human common carotid artery.

Blood Flow Velocity↗

PubMed1998

Septum orbitale: high-resolution MR in orbital anatomy.

PURPOSE: The purpose of this study was to ascertain whether MR imaging, with the use of a surface coil, can accurately show small intraorbital structures; in particular, the septum orbitale. METHODS: Examinations of 26 patients who underwent unilateral orbital high-resolution MR imaging for different indications were evaluated to differentiate the septum orbitale from related structures, such as the aponeurosis of the levator palpebrae, the superior tarsal (Müller's) muscle, and the superior orbital (Whitnall's) ligament. RESULTS: A subtle differentiation of the septum orbitale was obtained in 23 patients (88%) and of the levator aponeurosis and Müller's muscle in 24 patients (92%). The orbicularis oculi muscle and the submuscular fibroadipose tissue were reliably identified in all patients. CONCLUSIONS: High-resolution MR imaging is suitable for differentiating small intraorbital structures. Nevertheless, an exact depiction of the septum orbitale remains very much dependent on the cooperation of the patient. The site of orbital disease can be determined precisely and in a noninvasive manner in relation to the septum orbitale.

Aged↗

PubMed1998

Loss of dopamine-D2 receptor binding sites in Parkinsonian plus syndromes.

UNLABELLED: This study analyzed temporal changes of striatal dopamine-D2 receptor binding during the course of different extrapyramidal movement disorders using 123I-iodobenzamide (IBZM) SPECT. METHODS: Eighteen patients (9 with Parkinson's disease, 9 with parkinsonian plus syndrome) were followed for 11-53 mo. Dopamine-D2 receptor binding was assessed using 123I-IBZM SPECT at the beginning and at the end of the follow-up period. SPECT data were acquired 120 min postinjection of 3-5 mCi 123I-IBZM. A semiautomated algorithm was applied to the raw data for semiquantitative evaluation of regional cerebral receptor binding. RESULTS: Intraobserver (r = 0.992) and interobserver (r = 0.930) variance was low for the semiautomated interpretation of the SPECT examination of the dopaminergic D2 receptor binding, reflecting a highly reproducible SPECT algorithm. Mean specific dopamine-D2 receptor binding was lower in patients with parkinsonian plus syndrome compared to patients with Parkinson's disease on the initial (p < 0.001) as well as the follow-up study (p < 0.001). In patients with Parkinson's disease, we observed an unaffected receptor binding compared to a reduced binding of radiotracer in patients with parkinsonian plus syndrome during the course of the disease (p < 0.001). CONCLUSION: During the follow-up, patients with Parkinson's disease showed a constant dopamine-D2 receptor binding. In contrast, patients with parkinsonian plus syndrome revealed a decline of the binding of dopamine-D2 receptor. These findings are in agreement with histopathological data that demonstrated a preserved dopamine-D2 receptor status in patients with Parkinson's disease and a decline of the dopamine-D2 receptors in patients with parkinsonian plus syndrome. SPECT examinations using 123I-IBZM are useful for assessing dynamic changes of dopamine-D2 receptors in extrapyramidal movement disorders. Semiquantitative SPECT evaluations may provide valuable information for clinical management and prognosis of the patient with extrapyramidal movement disorders.

Adult↗

PubMed1998

[Imaging tumor extension of renal cell carcinomas with magnetic resonance tomography. Improved tumor-tissue contrast with Gd-DTPA-assisted spin-echo sequences and simultaneous fat suppression].

PURPOSE: To evaluate the use of contrast-enhanced T1-weighted images with fat suppression (T1FS) to improve the contrast-to-noise ratio of renal cancer and renal parenchyma as well as perirenal fat. METHODS: 25 patients with histologically proven unilateral renal cancer after nephrectomy were examined before surgery. In addition to plane and contrast-enhanced T1-weighted as well as T2-weighted spin-echo images, all patients had T1 FS immediately after administration of Gd-DTPA in two planes. The contrast-to-noise ratio was calculated using circular regions-of-interest which outlined the tumor, the renal parenchyma, pyelon, and the perirenal fat. RESULTS: T1 FS significantly improved the contrast-to-noise ratio of renal cancer and renal parenchyma compared to all conventional spinecho sequences (p < 0.001; Wilcoxon-Test). Compared to contrast-enhanced T1-weighted images without fat-suppression T1 FS yielded a higher CNR of the tumor, the perirenal fat and the pyelon. Another advantage was the absence of the chemical-shift artifact which is mostly pronounced in T2-weighted images and a reduced number of observed artifacts due to breathing. CONCLUSION: T1 FS should replace conventional contrast-enhanced T1-weighted spin-echo images in the work-up of renal cancer using MRI.

Adult↗

PubMed1998

[Cervix carcinoma: staging, therapy, after-care. Experiences with magnetic resonance tomography of cervix carcinoma based on recent literature 1993 to 1997].

The investigation of cervix carcinoma with magnetic resonance tomography (MRT) is still controversially discussed with regard to its diagnostic value as well as for planning radiation therapy. The purpose of this article is to present and discuss papers published between 1993 and 1997 in this field with respect to the technique used, the contrast media applied and its clinical value. A literature search using three different databases (Medline, Embase, Cancerlit) identified 39 publications, which were then analysed. Despite the partially suboptimal presentation of results in these papers MRT proved superior to other imaging modalities. Due to better demarcation of cervix carcinoma with MRT, it was possible to calculate tumor value as well as to correctly judge the infiltrative character. This allows for a more precise treatment and staging of the patient's prognosis. In the future, MRT might be useful in diagnosing recurrence at relatively early stage. Unfortunately lymphatic nodes can only be insufficiently verified using MRT.

Cervix Uteri↗

PubMed1998

Choroidal hemangioma: MR findings and differentiation from uveal melanoma.

BACKGROUND AND PURPOSE: The aim of this study was to establish the MR imaging characteristics of choroidal hemangioma and to compare them with those of uveal melanoma. METHODS: Among 41 patients examined at 1.5 T (4-cm surface coil, T1-weighted and fast spin-echo T2-weighted sequences), 25 had uveal melanoma and 16 had circumscribed choroidal hemangioma. After i.v. bolus injection of gadopentetate dimeglumine, dynamic and T1-weighted sequences were acquired. RESULTS: In patients with choroidal hemangioma, uniform signal characteristics were detected on fast T2-weighted images. In 15 of 16 patients with choroidal hemangioma, lesions were isointense with vitreous on fast spin-echo T2-weighted images, whereas lesions in 24 of 25 patients with uveal melanoma were hypointense. Signal characteristics of uveal melanoma and hemangioma did not differ significantly on plain T1-weighted images. Enhancement was earlier and much stronger for circumscribed choroidal hemangioma than for uveal melanoma. After i.v. bolus application of gadopentetate dimeglumine, the increase of signal intensity was higher for circumscribed choroidal hemangioma (signal intensity ratio, 5.8) than for uveal melanoma (signal intensity ratio, 2.2). CONCLUSION: Circumscribed choroidal hemangioma may be difficult to differentiate from melanoma by ophthalmologic examination. Differentiation may not be possible if direct viewing of uveal space-occupying lesions is hampered by opaque vitreous media. The characteristic findings on fast spin-echo T2-weighted MR images and early enhanced images aid in differentiating choroidal hemangioma from uveal melanoma.

Adolescent↗

PubMed1998

MRI-assisted specification/localization of target volumes. Aspects of quality control.

The transportation of MRI information on tumor extension into CT-based radiation therapy planning is desirable for several reasons. MRI's better contrast resolution is usually considered the most important, as it leads to a more exact definition of target volumes. Unlike diagnostic imaging, where a certain margin of error in depiction of tumor extension seems acceptable, radiation therapy planning makes it absolutely necessary, that the contents of every MR pixel (or voxel) correspond exactly to the corresponding area in the patient examined. This exact correspondence may be disturbed by a variety of influencing factors. Objects like various implants may lead to the most severe image distortions and--even worse--contrast alterations, some of which are not easily visible on the slices which are used for target volume definition. Additionally, MR images may have intrinsic faults which are able to change the correspondence between the voxel and the part of the patient's body it represents. Quality control has therefore to ensure that parameters like slice thickness are correct and kept constant by the imager. Image fusion may then be used to transfer MR information on tumor extension into the CT data. Electron density distribution provided by CT then allows for treatment planning. Implanted markers may then be used to ensure exact correspondence between the examined parts of the patient's body and the representing pixel or voxel. Care should be taken that landmarks themselves do not influence this relationship.

Brain Neoplasms↗

PubMed1997

[Multi-media presentation of radiologic image data with the Internet].

AIM: Recent developments of the Internet (World Wide Web) allow the integration of audio, video, digital film sequences, and three-dimensional data. The applicability of these innovations for medical documentation is demonstrated. METHODS: Our existing software for medical image processing and 3D reconstruction was extended to provide images, film sequences, and complex 3D models in an Internet-compatible data format. RESULTS: The multimedia results of the image processing were integrated into Internet documents. Specialized programs are no longer necessary for visualization. The Internet software allows for user-friendly handling and interactive presentation of the 2D and 3D data. CONCLUSIONS: The Internet offers public-domain software for display of images, audio/video, and 3D data. Thus, the tools of the Internet represent an ideal basis for local hospital information systems, computer-aided medical education, and teleconferencing.

Computer Communication Networks↗

PubMed1997

MR anatomy and small lesions of the eye: improved delineation with a special surface coil.

To develop an improved investigation protocol for MRI studies of intraocular lesions, imaging with a small surface coil (diameter 6 cm) was compared with a standard surface coil (diameter 11 cm). Both coils were assessed initially on an eye phantom and then by studying 22 patients with uveal melanoma and similar lesions of the eye. The influence of bandwidth and field or view (FOV) were systematically studied and evaluated quantitatively. A smaller bandwidth improved image quality independent of surface coil size. The subsequent secondary increase in chemical shift artefact was acceptable. Smaller FOVs (60-80 mm) necessitated the use of a smaller surface coil. A smaller bandwidth also proved to be advantageous with the use of the smaller surface coil. In conclusion, a smaller-diameter surface coil improves MR imaging of ocular lesions. Pulse sequences with a small bandwidth maintain an acceptable signal-to-noise ratio when the FOV is reduced.

Artifacts↗

PubMed1997

[CT volumetry of the liver before transplantation].

PURPOSE: Purpose of the study was to assess the predictive accuracy of preoperative CT volumetry for water displacement volume after liver transplantation. METHODS: In a retrospective study the liver volume of 52 patients who underwent an orthotopic liver transplantation, was calculated preoperatively based on incremental and spiral computed tomography (CT). The calculated values were compared with the liver volume measured by water displacement and weight of the extirpated liver. RESULTS: Marked differences of 19-21.5% were seen between calculated CT volume and water displacement volume for the entire group, and of 12.4-16.9% for livers with a plausible physical liver density (0.9 and 1.1 g/cm3). In this group, 68-86% of the livers were in the acceptable tolerance range for a predictive accuracy (+10% to -20%). Other error sources, such as the breathing shift of the abdominal organs and interobserver variability (1.5-2.7%), were of minor importance for volume calculation. CONCLUSION: In conclusion, both incremental CT and spiral CT are reliable methods for the preoperative estimation of the liver volume, whereas best accordance with the corrected water displacement volume was obtained using the individual segmentation thresholds.

Adolescent↗

PubMed1997

[How certain is teleradiological telediagnosis for the tomographic procedure?].

PURPOSE: To define the value of teleradiographic studies, a comparison was carried out between digitised copies of CT examinations of the skull with the original images. Differences in image quality obtained from a digital scanner and a camera were quantified. MATERIAL AND METHOD: 56 CT examinations of the skull, 28 of which had discrete abnormalities, were chosen for ROC analysis. The original films were digitised with a Vidar VXR-12 scanner and Panasonic WV-160 and WV-BP 500 cameras. The images were evaluated by five radiologists after image transfer with Video Conference software to a personal computer. RESULTS: For the analysis of the films the area under the ROC curve was 0.91 +/- 0.04, for the digital scanner it was 0.85 +/- 0.04, for camera WV-BP 500 0.89 +/- 0.06 and for camera WE-160 0.87 +/- 0.09. Comparison with the film findings showed. a minimal p-value of 0.17 which indicated that there was no significant reduction in diagnostic value following digitization. CONCLUSION: The probable reason for the slight deterioration using the digital scanner was the reduction to 75 dpi compared with 134 dpi on the CT films. The cameras produce image noise comparable to CT with low window settings and reduced local resolution. We expect similar results for CT with soft tissue windows or for MRT of the skull. Conventional radiographs containing high local resolution, wide grey scale and low image noise would presumably make higher demands on methods of digitization.

Computers↗

PubMed1997

[Contrast agent enhanced duplex ultrasonography: visualization of the hepatic artery after orthotopic liver transplantation].

PURPOSE: A prospective study was carried out to determine whether an improved assessment of the anatomy and flow velocity in the hepatic artery could be achieved by the administration of a capillary transversing contrast agent (Levovist) in patients after orthotopic liver transplantation. METHODS: In 21 (62%) of 34 patients after liver transplantation, only an insufficient visualisation of the hepatic artery was achieved. Therefore, a capillary transversing contrast agent was administered intravenously. Pre- and post-contrast peak velocity and Doppler frequency shift in the proper hepatic artery were measured and image quality of colour and spectral Doppler was assessed by a qualitative scale. RESULTS: Image quality, with complete visualisation of hepatic artery in 79% (precontrast 38%) of all cases, was significantly improved (p < 0.01 (Wilcoxon test)) by the administration of a contrast agent. CONCLUSIONS: Visualisation of the hepatic artery after orthotopic liver transplantation can be improved by the administration of Levovist. It allows a reliable measurement of peak velocity and Doppler frequency shift and helps to avoid further imaging.

Adult↗

PubMed1997

[Vascularization patterns in focal liver lesions: comparison of plain and signal-enhanced amplitude-modulated color duplex ultrasonography].

PURPOSE: Morphology of focal liver lesions was studied by power Doppler. Plain images and images after i.v. application of galactose-based microbubbles (Levovist, Schering AG) were compared. METHODS: 21 patients with focal liver lesions were studied by power Doppler before and after application of the signal enhancer. RESULTS: In lesions that showed short pulsations in plain studies, vascular structures were visible after application of the signal enhancer. In hepatocellular carcinomas, multiple arteries with small diameter became visible. Peripheral veins were detected in metastases. A large feeding artery was detected in 1/2 haemangiomas with flow and in a focal nodular hyperplasia. CONCLUSION: In comparison to plain amplitude-modulated colour-coded duplex ultrasound, vascular patterns of focal liver lesions were more clearly visible after injection of a signal-enhancer.

Adult↗

PubMed1997

[Dynamic computerized tomography of the bone marrow of normal and pathologic vertebrae].

PURPOSE: The contrast medium dynamics of normal and abnormal bone marrow was examined by CT. MATERIAL AND METHOD: Standardised sections of lumbar vertebrae were obtained after intravenous injection of 80 ml Ultravist 370 and time-density curves of the marrow spaces were calculated in 38 patients. RESULTS: Time-density curves of patients with normal bone marrow differed significantly from those with proliferative bone marrow diseases in respect of maximal density and uptake at 120 and 240 seconds. Patients treated by radiation showed reduced uptake. CONCLUSION: Variations in the time-density curves between normal and abnormal bone marrow provided evidence of different perfusion and uptake of the contrast medium in the extracellular space of the bone marrow. Further investigation will be necessary to determine whether dynamic CT is able to document the effect of radiotherapy or chemotherapy on malignant bone marrow infiltration.

Adenocarcinoma↗

PubMed1997

[Use of Ga-67 SPECT in patients with malignant lymphoma after primary chemotherapy for further treatment planning: comparison with spiral CT].

PURPOSE: To compare the diagnostic value of gallium scintigraphy using a SPECT technique with spiral CT for evaluating activity following chemotherapy in patients with malignant lymphoma and to determine treatment options. MATERIAL AND METHOD: The results of gallium scintigraphy in 28 patients with malignant lymphoma (19 Hodgkin's disease, 9 high grade non-Hodgkin's lymphoma) following curative treatment were compared with the CT morphology in relation to inactive regions and residual masses. RESULTS: Ga-67-SPECT proved superior to CT for evaluating the activity in 85 initially involved nodes (sensitivity 94.4% against 83.3%; specificity 100% against 92.5%). It was, however, inferior for demonstrating organ involvement in 28 instances. In seven patients with residual masses, Ga-67-SPECT directly affected staging and further therapy. CONCLUSION: The increasing use of secondary treatment schemes for curative purposes makes Ga-67-SPECT a suitable method for the early recognition of residual activity in Hodgkin's disease and high grade non-Hodgkin's lymphoma.

Adult↗

PubMed1997

[Safety and use of gadobutrol in patients with brain tumors (phase III trial)].

PURPOSE: The purpose of the study was to investigate the use and safety of Gadobutrol, a new low-osmolar, non-ionic contrast agent for MRI using a total dose of 0.3 mmol/kg b.w. on the basis of a clinical phase 3 study. METHODS: 30 patients with primary brain tumours (n = 15) or cerebral metastases (n = 15) were examined via MRI before and after application of a total of 0.3 mmol/kg b.w. given in two fractions (0.1 and 0.2 mmol/kg b.w.). T2-weighted images were performed before, T1-weighted images before, between and after application of contrast material. RESULTS: In this study one-molar Gadobutrol showed a good tolerance. In half of the cases the contrast between lesion and brain was improved comparing single and triple dose, but this means only a slightly improvement of information for the primary brain tumours compared with single dose. The detected metastatic lesions increased in 40% of the patients after the single dose and in 53% of the patients after cumulative triple dose. There was a consecutive change in therapy in 20% of the patients. CONCLUSION: For the differentiation of primary brain tumours the single dose was sufficient, in metastatic lesions triple dose was essential for the detection or exclusion of multifocality.

Adenoma↗

PubMed1997

Comparison of transthoracic three dimensional echocardiography with magnetic resonance imaging in the assessment of right ventricular volume and mass.

OBJECTIVE: Assessment of right ventricular volume and mass with three dimensional echocardiography and comparison with magnetic resonance imaging. METHODS: Measurements of right ventricular volumes performed on three dimensional datasets acquired by transthoracic echocardiography were compared to those obtained from magnetic resonance imaging performed on the same day. Volumes were measured in end systole and end diastole and ejection fraction calculated. Right ventricular mass was assessed in end systole. With both methods, the areas of a 2 mm thick slice of the ventricle were manually outlined and multiplied by the slice thickness to obtain slice volume. Slice volumes were multiplied by the number of measured slices to obtain the ventricular volume. PATIENTS: 16 patients were studied: three with normal hearts, three after surgical repair of coarctation of the aorta, nine following repair of tetralogy of Fallot, and one with Mustard atrial repair of complete transposition of the great arteries. RESULTS: Correlation between end diastolic volumes measured by both methods was r = 0.95 with limits of agreement ranging from -3.5 to 12.5 ml; correlation for end systolic volumes was r = 0.87 with limits of agreement between -4.0 and 16.4 ml; correlation for end systolic right ventricular mass was r = 0.81 with limits of agreement between -7.0 and 20.6 g. Interobserver variability ranged from 4.3% (range 0.2% to 9.3%) for end diastolic volume to 7.6% (1.8% to 15.4%) for mass measurements. CONCLUSIONS: With transthoracic three dimensional echocardiography, end diastolic right ventricular volumes can be assessed with acceptable accuracy in normal hearts and those with enlarged right ventricles, whereas the current method of three dimensional echocardiography is less good for end systolic volumes and not satisfactory for right ventricular mass measurements.

Adolescent↗