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Biomedical subjects

S Venz

Publications and source records attributed to S Venz.

At least 37 records · Page 2Linked to original sources
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↗
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↗
PubMed1996

[Preoperative staging of bladder carcinomas with Gd-DTPA-supported dynamic magnetic resonance tomography. Comparison with plain and Gd-DTPA-supported spin-echo sequences].

PURPOSE: Evaluation of dynamic Gd-DTPA enhanced MR imaging in the staging of bladder cancer. METHODS: We studied 40 patients with histologically proven bladder cancer. All patients were examined with routine T1- and T2-weighted MRI and late Gd-DTPA enhanced T1-weighted MRI. Additionally, a dynamic study was performed with 10 subsequent short FLASH-2-D gradient echo sequences without delay immediately after bolus injection of Gd-DTPA. Signal intensities of the tumour and of the surrounding tissue as well as image contrast parameters were quantified. RESULTS: The dynamic study showed a higher accuracy in the evaluation of stage pTa to pT2 cancer compared to spin echo MRI (63% and 46%, respectively) and no difference regarding the sensitivity (87.5%). However, overstaging was a problem with both modalities. The contrast-to-noise ratio of bladder tumour and muscle was equal or significant higher with the dynamic study compared to spin echo MRI. A higher signal-to-contrast ratio of bladder tumour and bladder muscle was calculated for the dynamic study compared with the spin-echo MRI (p < 0.01; Mann-Whitney U test). CONCLUSION: Dynamic Gd-DTPA enhanced MRI is recommended to be used additionally in the preoperative staging of bladder neoplasms.

Adult↗
PubMed1996

[Magnetic resonance tomography in patients with Parkinson's disease and Parkinson-plus syndromes].

PURPOSE: To define characteristic MR-findings in patients with clinically typical extrapyramidal movement disorders. METHODS: 15 patients with Parkinson's disease (PD), 9 with multisystem atrophy (MSA), and 6 with progressive supranuclear palsy (PSP) underwent MRI using a 1.5 T. Magnetom unit. Two investigators analysed the images with special regard to global and/or focal atrophy and to changes in signal intensity of the CNS in the consensus mode. Normal images of 10 subjects served as controls to patient's images. RESULTS: In all patients with PSP and MSA characteristic pathological findings on MRI were observed including regional changes within the extrapyramidal nuclei. In contrast all patients with PD had an unremarkable MRI study of the CNS. CONCLUSION: MRI enables us to define characteristic morphological changes of the brain in patients with extrapyramidal movement disorders. Early recognition of these findings avoids misdiagnoses in patients who are difficult to diagnose.

Adult↗
PubMed1996

The value of magnetic resonance imaging in the diagnosis of suspected penile fracture with atypical clinical findings.

PURPOSE: We studied the use of magnetic resonance imaging (MRI) in the diagnosis of suspected penile fracture. MATERIALS AND METHODS: Penile fracture diagnosis was based on classic history and typical physical signs in 8 patients who were treated surgically without any further diagnostic procedure. Sonography, cavernosography and MRI were performed in 4 patients with equivocal findings. RESULTS: Only MRI identified rupture of the corpus cavernosum in all 4 cases. CONCLUSIONS: MRI is the most accurate imaging procedure when penile fracture is suspected but clinical findings are unusual.

Adult↗
PubMed1996

[Determining the depth of infiltration in urinary bladder carcinoma with contrast medium enhanced dynamic magnetic resonance tomography. With reference to postoperative findings and inflammation].

OBJECTIVE: The purpose of this study was to evaluate dynamic contrast-enhanced magnetic resonance imaging for the staging of urothelial bladder carcinoma and to compare it with plain and contrast-enhanced spin-echo MRI. METHODS: Pre-operative MRI was carried out in 62 patients. Post-operative histological examination confirmed bladder carcinoma in 50/62 patients. Carcinoma was excluded in 12 patients. Beside spinecho MRI a dynamic contrast-enhanced study was performed immediately after IV application of Gd-DTPA using 10 sequential FLASH-2Dsequences, each with a duration of 15 s. Images were evaluated visually by three radiologists in a blinded fashion. RESULTS: In 41/62 patients pre-operative tumor staging with the dynamic contrast-enhanced study was confirmed by the histological examination after surgery. MRI with spinecho sequences yielded correct staging in 30/62 patients (P = 0.028). Staging of superficial bladder cancer was more accurate with dynamic contrast-enhanced MRI than with conventional MRI (P = 0.024). Overstaging was observed in some patients with stage pT1 tumors. Furthermore, postoperative changes of the bladder wall could be differentiated from cancer due to significantly earlier contrast enhancement of bladder cancer compared with postoperative and inflammatory alterations (P < 0.001). CONCLUSION: Contrast-enhanced dynamic MRI is a helpful addition in the presurgical T-staging of bladder cancer.

Adult↗
PubMed1995

[MR urography with the T2-weighted turbo-spin-echo sequence].

Tumor-induced dilatation of the urinary tract is difficult to diagnose in the distal part of the ureter, including the stenosis, by ultrasound and X-ray. Often on account of renal insufficiency and allergy, i.v.-contrast media cannot be used. The present study should show the suitability of fast T2-weighted (turbo-) spin-echo sequences (T2-TSE) for MR-urography (MRU). Seven patients (62.3 +/- 6.1 years) were examined in the coronal plane with T2-TSE sequence (TR = 4500 ms, TE = 160 ms) and an MRU was calculated by using the MIP method (maximal intensity projection). This technique enabled urogram-like morphological representation of dilated urinary tract including stenosis in 6 of 7 patients. Assuming a high magnetic field homogeneity, MRU by using a T2-TSE-sequence, without i.v.-contrast media administration, can visualize the urinary tract dilatation and localize tumor-induced stenosis.

Adult↗
PubMed1995

[Estimating patient dosage in radiologic examinations. Effective doses of the most frequent roentgen examinations].

The effective dose (E) measures the stochastic risk of radiation exposure from the viewpoint of the induction of cancer and genetic diseases. In order to compare this risk in roentgen examinations, the effective dose was calculated for the most frequent roentgen examinations. The calculations were performed with a mathematical human phantom for a standard patient. Acquisition parameters were chosen according to national recommendations. The highest values were found for the small bowel enema and lumbar myelography, the lowest values for X-rays of the cervical spine, the paranasal sinuses and the upper thigh.

Body Burden↗
PubMed1994

[[111In]-DTPA-D-phenylalanine octreotide SPECT for the scintigraphic imaging of enhanced somatostatin-receptor density in endocrine ophthalmopathy].

Recently, [111In]-DTPA-D-phenylalanine-octreotide was introduced for clinical use. This radioligand binds specifically to somatostatin receptors and is suitable for SPECT examinations. The aim of this study was to clarify whether an increased somatostatin receptor density can be imaged and quantified in patients with endocrine ophthalmopathy (e.o.). 7 patients between 34 and 55 years with e.o. at stages III to VI and 4 controls between 38 and 63 years were examined. All patients and controls received approximately 200 MBq [111In]-DTPA-D-phenylalanine-octreotide by IV injection. A SPECT examination was performed 4 hours after injection and a normalised tracer uptake (A(n)) was calculated for both orbitae. In patients with e.o. the values of A(n) were significantly higher compared with controls (P = 0.002). There was a correlation between A(n) and exophthalmus stages according to Hertel with r = 0.844 (P = 0.001). These results indicate that [111In]-DTPA-D-phenylalanine-octreotide SPECT might be useful for the in vivo assessment of an increased somatostatin receptor density in e.o. These findings could have an impact on the treatment with somatostatin analogous in e.o.

Adult↗
PubMed1994

[Osteoplastic bone metastases in prostatic carcinoma: magnetic resonance tomography and bone marrow scintigraphy].

MRI of the vertebral column was performed in 28 patients with histologically confirmed prostate carcinoma. Besides routine spin-echo sequences all patients were examined with gradient-echo sequences using the chemical shift mode. In addition, in all patients bone marrow scintigraphy (BMS) was performed, and all results were compared with routine bone scan (BS). In our study BMS was not superior to bone scan. In contrast, MRI scan revealed solitary metastases in two patients with negative BS and BMS. Osteoplastic metastases showed a contrast enhancement in the MRI and could be distinguished from benign alterations.

Aged↗
PubMed1994

Dopamine D2 receptor imaging with iodine-123-iodobenzamide SPECT in idiopathic rotational torticollis.

UNLABELLED: The cause of idiopathic rotational torticollis (IRT) is not completely understood to date. However, basal ganglia are believed to be involved in the pathophysiology of IRT. To elucidate this disorder further, the value of iodobenzamide (IBZM) SPECT was studied for the evaluation of striatal dopamine D2 receptors in these patients. METHODS: Striatal dopamine D2 receptor density was assessed in 10 patients with IRT using 123I-IBZM SPECT. The images were interpreted by a nuclear medicine physician initially to determine IBZM binding within the striatum and the cerebellum and, secondly, interstriatal IBZM binding. The results were correlated with the clinical parameters of the patients and compared with the results obtained from normal controls. RESULTS: No difference was found in average, specific striatal IBZM binding (basal ganglia/cerebellum ratio) between patients and controls. However, interstriatal analysis of IBZM binding revealed a significantly higher binding in the striatum contralateral to the direction of the torticollis (p = 0.026, by chi-square test). CONCLUSION: It was concluded that the striatal dopamine D2 receptor status is altered in patients with IRT.

Adult↗
PubMed1994

[Preoperative evaluation of drug resistant focal epilepsies with 123I-iomazenil SPECT. Comparison with vidio/EEG monitoring and postoperative results].

SPECT with the benzodiazepine receptor antagonist 123I-Iomazenil was performed in 33 patients with intractable partial seizures for pre-operative evaluation. The results combined with MRI and 99mTc-HMPAO-SPECT findings were compared with the video-assisted EEG monitoring ("gold standard") which localised the focus in 25 patients. 11 patients underwent surgical resection of the epileptogenic area and became seizure-free for a period up to 13 months. The Iomazenil SPECT had a significantly higher sensitivity compared to 99mTc-HMPAO in the visualization of an epileptogenic area and should be regularly used in the diagnostic of medically intractable partial seizures.

Adolescent↗
PubMed1994

[(123 I)-anti-NCA95 antibodies in diagnosis of bacterial wound infections after prosthetic vascular replacement. Comparison with computerized tomography].

Immunoscintigraphy (IS) with [123I]-anti-NCA95 labelled autologous granulocytes and computer-tomography (CT) examinations were performed in 21 patients with clinical suspicion of a vascular graft infection. The results of both IS and CT were compared with bacteriological and surgical findings. In this study the sensitivity was higher for IS compared with CT (92% and 67%, respectively). However, specificity was lower in IS compared with CT (89% and 100%, respectively). No false positive results have been found in CT. False positive results were observed in IS within 30 days after vascular surgery and may be due to a unspecific accumulation of granulocytes in perivascular hematomas. In later infection of a vascular graft (i.e. more than 30 days after surgery) no false positive findings were made by IS. In contrast, CT was false negative in two cases. IS with [125I]-anti-NCA95 labelled autologous granulocytes represents a useful tool for the detection of vascular graft infection, since granulocyte accumulation in infected tissue can be visualized with high sensitivity and specificity.

Antibodies, Monoclonal↗
PubMed1994

[123I-iomazenil- and 99mTc-HMPAO in the diagnosis of focal epilepsies: a comparison of untreated and treated patients].

The purpose of this study was to compare HMPAO- and IMZ-SPECT findings in treated and untreated patients with focal epilepsies. We examined 20 patients (untreated 13; treated 7). All patients had a normal CT and/or MRI scan. In all patients both whole-brain activity and regional count density (rcd) were evaluated by SPECT. Furthermore, the specific and non-specific binding of IMZ were calculated for each ROI and the results of both, treated and untreated patients were compared. Our data indicate that the normalized cerebral total binding of IMZ was significantly increased in all regions in the group of treated patients (p < 0.001). In contrast, no difference in the tracer binding was found with HMPAO-SPECT. We conclude that the difference in the IMZ-binding might be due either to exogenous or endogenous factors. In our study IMZ-SPECT had a higher sensitivity and a lower specificity in the detection of decreased rcd in areas with EEG findings that indicate an epileptogenic focus compared with HMPAO-SPECT.

Adolescent↗
PubMed1993

Modified surface-active monomers for adhesive bonding to dentin.

PMGDM, a PMDM-type adhesive monomer, was synthesized from pyromellitic dianhydride and glycerol dimethacrylate. Only the para isomer of PMDM, a solid, is used in dental adhesives. The adhesive monomer PMGDM is a liquid and consists of a mixture of para- and meta isomers. This study shows that PMGDM has several advantages over PMDM. For example, the adhesive can be applied at a greater thickness, and additives and/or additional initiators for improved curing can be incorporated. Use of the liquid monomer PMGDM also provided a convenient means of varying the thickness of the adhesive layer between dentin and composite. The adhesive bonds were tested in both shear and tensile modes. PMDM was used as the control. The reliability of the bonds, as judged from the Weibull modulus and Weibull characteristic strength, was improved by (1) use of more concentrated solutions of PMGDM adhesive, (2) use of an adhesive thickness of about 25 microns, and (3) modification of PMGDM with a diluent monomer which is expected to enhance the degree of cure and/or the dentin-wetting properties of the adhesive resin.

Adhesives↗
PubMed1991

NIR-spectroscopic investigation of water sorption characteristics of dental resins and composites.

A near infrared (NIR) method using the 5200 cm(-1) absorption of water has been employed to examine water absorbed in photopolymerized dental resins and composites in the form of 0.01-cm- to 0.15-cm-thick specimens. The concentration, c [mol L(-1)], of absorbed water in specimens of thickness t [cm] was calculated by means of Beer's law, A = e ct. A is the NIR absorbance and e is the absorptivity of absorbed water. e depends on the environment of the water molecule and it is necessary to estimate e for water in each material. Water sorption was determined gravimetrically and correlated to the absorbance in the NIR spectrum. Once the relationship between e and water content was known for a material, water sorption was determined rapidly on very thin specimens for faster equilibration. Where dissolution of the specimen occurred, the solubility behavior of the specimen was evaluated from a comparison of NIR and gravimetric measurements. The NIR absorptivity, e, of water absorbed in a polymeric medium was found to be inversely related to the degree of hydrophilicity and hydrogen bonding capability of the polymer. The presence of water clusters in a polyethylene oxide methacrylate polymer was inferred from convex-up curvature in the plot of e vs. water content.

Absorption↗