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Biomedical subjects

N Hosten

Publications and source records attributed to N Hosten.

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

Signal-enhanced color Doppler sonography of deep venous thrombosis in the lower limbs and pelvis.

Detection of Doppler signal tends to be more difficult in peripheral veins owing to low flow velocity. This can be caused by nonoccluding thrombosis, post-thrombotic wall changes, or a deep anatomic location of pelvic veins. The last-mentioned frequently is accompanied by interference by bowel gas. In addition, inappropriate insonation angles adversely affect the outcome of color-coded Doppler interrogation. The purpose of the present study was to evaluate the effectiveness of signal-enhanced color Doppler sonography on peripheral veins in 31 patients clinically suspected of having deep vein thrombosis. As a result of diagnostic uncertainty, additional enhanced studies were performed on 43 venous segments. The enhancement led to a decrease in false-positive results (from four patients to one patient) and false-negative results (from four patients to two patients) compared to unenhanced studies. Evaluation of the deeply located pelvic veins profited the most through signal enhanced Doppler sonography.

Adult↗
PubMed1999

Staging and monitoring of malignant lymphoma of the bone: comparison of 67Ga scintigraphy and MRI.

UNLABELLED: The aim of this study was two-fold: to compare 67Ga scintigraphy with MRI (a) for the staging of malignant lymphoma of the bone and (b) with regard to accuracy in detecting residual disease after first-line chemotherapy for restaging. METHODS: Twenty-one patients with 36 malignant osseous lesions were examined, including 7 patients with primary or multifocal osseous lymphoma and 14 patients with malignant lymphoma and simultaneous or secondary involvement of the bone. After first-line therapy, MRI and 67Ga scintigraphy were performed on 13 patients. The remission status based on all clinical and radiological findings during the follow-up was used as the gold standard. RESULTS: The osseous lesions were located on the axial skeleton in 64% of patients and on the appendicular skeleton in 36%. 67Ga scintigraphy detected 77% of the osseous lesions examined by MRI. For restaging after first-line therapy, MRI had a sensitivity of 90% and a specificity of 80% when dynamic MRI information was included. There were several false-positive results as a result of the pathologic increase in signal intensity ratios of reactive hematopoietic regions after chemotherapy. For 67Ga scintigraphy, a sensitivity of 70% and a specificity of 93% were calculated. CONCLUSION: These data show that monitoring malignant lymphoma of the bone still presents diagnostic problems. Given the high sensitivity of MRI and the high specificity of 67Ga scintigraphy but the limited specificity of MRI and sensitivity of 67Ga scintigraphy, both methods are valuable but should be used as complementary diagnostic tools.

Adolescent↗
PubMed1999

[MRI in the diagnosis and differential diagnosis of radiocarpal diseases and injuries].

Advances in MRI technology have greatly improved visualization of the radio-carpal region. With todays high-resolution imaging, even very small anatomic structures like the triangular fibrocartilage may be seen. Established indications include the osteonecroses (scaphoid and lunate); however, MR images always should be evaluated in conjunction with plain radiographs. By delineating bone marrow edema, MRI is well suited for the detection of microfractures. Visualization of small soft tissue tumors, soft tissue extension of bone tumors and for staging of tumors in general may also be regarded as indications generally agreed upon. Promising indications include pathology of ligaments and similar structures.

Arthritis, Rheumatoid↗
PubMed1998

Imaging in epidural lipomatosis.

This paper reviews the literature concerning symptomatic epidural lipomatosis. The different diagnostic procedures (conventional myelography, computed tomography, and magnetic resonance imaging) and therapeutic approaches (including medical treatment, surgery, and dietary influence) are discussed.

Journal Article↗
PubMed1998

[Morphologic image processing operators: reduction of partial volume effects for improved 3D visualization of CT data].

AIM: The quality of segmentation and three-dimensional reconstruction of anatomical structures in tomographic slices is often impaired by disturbances due to partial volume effects (PVE). The potential for artefact reduction by use of the morphological image processing operators (MO) erosion and dilation is investigated. DESIGN: The CT examinations of 31 patients with pathological alterations in lung or brain were segmented using automatic region growing and the MO were applied in a different number of iterations. The processed regions were 3D-reconstructed (shaded surface display, MIP, volume rendering) and the occurrence of PVE-related artefacts using the signal-to-background ratio (SBR) prior to and after MO application was compared. RESULTS: For all patients under review, the artefacts caused by PVE were significantly reduced by erosion (lung: mean SBRpre = 1.67, SBRpost = 4.83; brain: SBRpre = 1.06, SBRpost = 1.29) even with only a small number of iterations. Region dilation was applied to integrate further structures (e.g. at tumor borders) into a configurable neighbourhood for segmentation and quantitative analysis. CONCLUSIONS: The MO represent an efficient approach for the reduction of PVE artefacts in 3D-CT reconstructions and allow optimized visualization of individual objects.

Densitometry↗
PubMed1998

[Electron-beam computed tomography in heart surgery].

PURPOSE: Electron beam CT (EBCT) has been devised to improve the imaging of the heart and the great vessels. Therefore, this method is expected to facilitate the imaging workup of patients referred for cardiothoracic surgery. We set out to review the most important surgical issues that can be addressed with this method. METHODS: From June, 1997 until July, 1998, more than 300 patients were referred from cardiothoracic surgery. In a retrospective analysis, diagnostic results were reviewed and compared with surgical findings and the clinical course. RESULTS: Aortocoronary bypass graft occlusions were detected with a sensitivity of 100% and a specificity of 95%. Calcifications of the aorta, pericardium and intracardiac tumors were surgically confirmed in all instances. There was a significant association of the degree of coronary artery calcification and the progression of cardiac allograft vasculopathy in 50 heart transplant recipients. In EBCT of the aorta, a high degree of diagnostic confidence was found for aortic dissection, aortic wall hematoma or aortic perforation. CONCLUSIONS: We conclude that EBCT represents an important diagnostic tool both for surgical planning and postoperative surveillance in cardiothoracic surgery.

Adult↗
PubMed1998

Lipomatous secretory meningioma: case report and review of the literature.

Secretory meningioma is a rare entity which may be characterised by imaging features unusual for other subtypes of meningioma, such as low attenuation on CT, high (fat-tissue equivalent) signal intensity on T1-weighted MRI, marked surrounding oedema, and irregular contrast enhancement. We report a case of secretory meningioma and review the literature.

Aged↗
PubMed1998

[High resolution functional magnetic resonance tomography with Gd-DTPA eyedrops in diagnosis of lacrimal apparatus diseases].

UNLABELLED: Both dacryocystography and dacryoscintigraphy are well established in the evaluation of stenoses of the lacrimal drainage system. They provide limited information about the ductal anatomy itself and about periductal structures. MR imaging was evaluated for its capability to directly visualize the lacrimal drainage system in detail and simultaneously provide functional characterization of dacryostenosis. SUBJECTS AND METHODS: Twenty-seven lacrimal drainage systems of 23 patients suffering from epiphora were examined in an MR unit before and after conjunctival and intravenous application of Gd-DTPA using a surface coil. RESULTS: Dacryostenosis was found in 23 of 27 lacrimal systems. Stenoses were localized to the canalicular (n = 3), saccular (n = 8), and ductal (n = 12) level, and were classified as stenosis or occlusion. CONCLUSION: MR imaging with conjunctival contrast application allows within one examination both detailed morphological and functional assessment of the lacrimal drainage system with depiction of surrounding structures. Limitations arise mainly from demands on technical and patient-related preconditions.

Contrast Media↗
PubMed1998

[Radiotherapy of exudative senile macular degeneration. A prospective controlled study].

UNLABELLED: Despite the successful therapy of subretinal neovascular membranes by laserphotocoagulation there are many problems to be overcome. In the case of subfoveolar neovascularization, photocoagulation leads to a sudden decrease in visual acuity. Recently radiotherapy is considered as an alternative. Complications and effectivity were evaluated in this prospective and randomized trial. The initial results are presented. PATIENTS AND METHODS: There are 76 patients (51 women, 25 men, average age 77.7 +/- 8.6 years) included in the prospective randomized study. All of them show subfoveolar neovascular membranes in FLA and a decrease in visual acuity between 0.05 and 0.5. They were randomly assigned to either the radiotherapy or the control group. Radiotherapy was done within 6 days by 6 x 2 Gy (6 MV photons). The follow-up was at 4 weeks, after 3 months, after 6 months and then every 6 months after the end of radiotherapy. On average the follow-up is at 15.1 months. RESULTS: Concerning age and visual acuity before therapy, the control group and the radiotherapy group were not significantly different. At 4 weeks after radiotherapy, visual acuity was 0.13 +/- 0.46 (LogMAR). After 12 months, visual acuity at a distance was 0.11 +/- 0.30 in the therapy group and 0.09 +/- 0.13 (P = 0.838) in the control group. Patients with a preoperative visual acuity better than 0.2 improved more after radiotherapy. Metamorphopsy improved in 75% of the therapy group. The following complications could be observed: In the control group 3 patients suffered subretinal bleeding, in the radiotherapy group 3 patients, respectively. CONCLUSIONS: At present, the follow-up is too short to recommend radiotherapy as a standard procedure in the case of subfoveolar neovascularization. The results in patients with a better preoperative visual acuity encourage us to continue this study.

Aged↗
PubMed1998

[Blood flow quantification in hemodialysis shunts by phase contrast magnetic resonance angiography (PC-MRA) compared with duplex sonography].

PURPOSE: Aim of this study was to evaluate whether phase contrast MR angiography (PC-MRA) could provide additional functional information besides morphology in the assessment of haemodialysis fistulae. MATERIAL AND METHOD: Twenty-two patients (11 male, 11 female), aged 22-77 years, were examined. MR images were obtained with a 1.5 T Gyroscan ACS-NT (Philips, Best, Netherlands) using a high-resolution wrap-around coil. In addition to MRA blood-flow measurements were performed with a gradient-echo sequence (TR 14 ms, TE 5-5.5 ms, flip-angle 15 degrees, 6 mm slice thickness, retrospective gating, matrix 96:128) in the venous and arterial section of the fistulae. Doppler flow measurements were performed at the same position with a Sonoline Elegra (Siemens AG, Erlangen) using a 7.5 MHz transducer. RESULTS: Both methods of flow-volume measurements showed a good correlation (r = 0.94 in the arterial section, r = 0.90 in the venous section, p < 0.001). The average calculated blood flow was measured 11% (arterial section) and 12.8% (venous section) higher with Pulsed Waved Doppler as compared to PC-MRA. CONCLUSION: PC-MRA with a high-resolution wrap-around coil is a reliable method for measuring functional parameters like flow-volume and flow velocity in haemodialysis fistulae and a useful complement to the visualisation capabilities of MRA.

Adult↗
PubMed1998

[When is it meaningful to support magnetic resonance tomography by administering a positive enteral contrast medium?--an account of practical experience].

PURPOSE: To evaluate in which parts of the gastrointestinal tract and in what clinical situations the diagnostic quality of MR examination may be improved by a positive enteral contrast agent. METHODS: MR examinations of 37 patients performed before and after application of a Gadolinium-DTPA preparation suitable for oral and rectal application were evaluated. Exams were evaluated by two independent observers. Neoplastic disease of the gastrointestinal tract constituted the majority of indications followed by inflammatory changes and extraenteral space-occupying lesions. RESULTS: The majority of examinations (62%) were improved by the application of enteral contrast agent. No effect was observed in 35%; in two patients image quality was poorer after contrast application. The benefit of enteral contrast agents was highest in MR examinations of the sigma and rectum. The enteral contrast agent was most valuable in the detection of lymphoma if an evaluation according to indication was performed. CONCLUSION: In selected cases, the diagnostic quality of abdominal MRI can be improved by the application of an enteral contrast agent. Apart from the effect of greater signal intensity, the contrast agent does complement MR imaging by a functional aspect.

Abdominal Neoplasms↗
PubMed1998

[Comparative findings of digital thoracic images and digital images of statistical phantoms as film copy, a radiological work station and a PC].

INTRODUCTION: An ROC analysis was carried out in order to determine the reliability of digital luminescence radiography review at a PC and this was compared with a radiological work station and with X-ray film on a viewing box. MATERIAL AND METHOD: 54 chest images obtained by digital luminescence radiography were selected, 31 of these contained small pulmonary nodules. In order to evaluate critical detail, five images of a phantom showing round foci were used. Five radiologists examined these, using a Siemens Magic View work station, a PC with proprietary software (ViewMed) and X-ray films on a viewing box. Image processing of the work station used the standard clinical application. ViewMed performs linear scaling of grey levels to 8 Bit. The results were examined statistically by means of a t-test. RESULTS: As far as the chest images were concerned there was no significant difference in the diagnostic value of these methods. There was, however, a highly significant loss of diagnostic information with respect to the round focus phantom when using the PC compared with the other methods. CONCLUSION: In the configuration in which it was used, the PC should not be relied on as a primary means of examination since critical details cannot always be seen. In routine use these play a subordinate role and there was no significant diagnostic loss where the chest images were concerned. We expect that by improvements in the frequency and contrast processing the PC accuracy will be considerably increased.

Humans↗
PubMed1998

[Cardiac MR flowmetry: experimental validation and results in patients with operated heart defects].

PURPOSE: A flow-sensitive MR sequence (phase-contrast technique) was evaluated in phantom studies with regard to factors influencing measurements and correctness of results. The sequence was additionally used for functional evaluation of operated congenital heart disease. METHODS: Pulsatile and constant flow were produced with the help of a phantom. Influence of angulation, range and vessel bending was evaluated. An examination protocol was developed from the results. 35 patients with surgically repaired congenital heart disease or without repair were examined. RESULTS: A range preset below the actual flow velocity as well as angulation of more than 20 degrees were isolated as main pitfalls in MR flowmetry. In addition to morphological MR findings flow measurements were possible in 11 patients at vessel sites which were not or not completely suited for examination by Doppler ultrasound. CONCLUSION: The evaluated phase-contrast technique allows for fast and reliable flow quantification if the influences identified in phantom studies are considered.

Blood Flow Velocity↗
PubMed1998

[Doppler sonographic monitoring control of perfusion of hepatocellular carcinoma after arterial chemoembolization].

INTRODUCTION: 22 patients with hepato-cellular carcinomas were examined sonographically before and after intra-arterial chemo-embolisation. The aim was to evaluate different techniques for judging tumour morphology and for assessing changes in perfusion. MATERIAL AND METHODS: The morphological appearances and perfusion changes were analysed by means of colour coded duplex sonography and power Doppler sonography before and after intravenous contrast medium. Pulsatility (Pl) and resistance index (RI) were used as quantitative parameters for judging changes in perfusion. RESULTS: In 13 patients intra-tumoral arteries were identified by duplex sonography and in four patients only by the power Doppler procedure. In three patients arterial vessels could only be identified after intravenous contrast. In 9 patients it was possible to document a reduction in arterial perfusion following embolisation. The indices calculated from these findings gave no prognostic indication. DISCUSSION: The methods described give information concerning changes in perfusion of a tumour following chemo-embolisation and, in conjunction with CT and clinical findings, provide indications for further tumour embolisation.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1998

[Appearance of choroidal melanoma on high resolution MRI using 1.5T with a dedicated surface coil in 200 consecutive patients].

PURPOSE: Choroidal melanomas usually present a characteristic appearance in MRI. Differing characteristics can cause problems in differential diagnosis between melanomas and other masses in the globe. The purpose of this study was to evaluate the appearance of choroidal melanomas with MRI in a large consecutive patient group. METHODS: In a prospective study, 200 patients with choroidal melanomas were investigated with MRI using a 1.5 T scanner and a 5 cm surface coil. Both quantitative and qualitative evaluation of the resulting images was performed. RESULTS: 78.5% of the melanomas presented with homogeneous signal intensities within the tumor due to a homogeneous pigmentation whereas 21.5% of the melanomas demonstrated a mixed pigmentation. Signal intensities of the homogeneous melanomas in the plain T1-WI were moderately or markedly hyperintense compared to the vitreous in 29.3% and moderately or markedly hypointense in the T2-WI in 37.1%. An accompanying retinal detachment was found in 65.5% and an extraocular growth in 7.0%. CONCLUSIONS: In 10% to 37% we observed the typical well known MR appearance, including homogeneous high signal in the T1-WI and low signals in the T2-WI. For further differentiation, morphological criteria (e.g. shape, size, and position) were used, which are also discussed.

Choroid Neoplasms↗
PubMed1998

[Color doppler ultrasonography in peripheral artery occlusive disease: continuous application of a signal enhancer].

PURPOSE: The effect of continuous infusion of a signal enhancer on the diagnostic efficacy of Doppler ultrasound in peripheral artery disease was evaluated. METHODS: 35 patients with peripheral artery disease were investigated by Doppler ultrasound before and during infusion of a signal enhancer (Levovist). Femoral and popliteal arteries were examined. Angiographic diagnoses included occlusions (24) and stenoses (22). They were compared to plain and enhanced Doppler findings. Artefacts and effects on signal intensity were evaluated. RESULTS: An increased Doppler signal was observed starting 1 min 35 s (mean) after begin of the infusion. It persisted for 11 min 46 s (mean). Signal enhanced studies provided less over- (0/1) and underestimation (3/5) of the findings and evaluation in the adductor channel was less compromised. Signal enhanced studies highlighted collaterals. CONCLUSION: Doppler ultrasound in patients with peripheral arterial disease is improved by continuous application of a signal enhancer.

Adult↗