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Karl-Jürgen Wolf

Publications and source records attributed to Karl-Jürgen Wolf.

13 recordsLinked to original sources
PubMed2005

Multipolar radiofrequency ablation of hepatic tumors: initial experience.

Institutional review board approval and patient informed consent were obtained. Use of a multipolar radiofrequency (RF) ablation device in patients with hepatic malignancy was prospectively evaluated with regard to feasibility, achieved ablation zone size and shape, technical effectiveness, and complications. Nineteen malignant liver tumors were treated with the multipolar resistance-controlled RF ablation system, with which up to three internally cooled bipolar coagulation electrodes can be operated simultaneously. Postinterventional imaging was performed with dynamic contrast material-enhanced magnetic resonance (MR) imaging and MR imaging-based three-dimensional planimetry. Complete tumor destruction was achieved in 18 of 19 tumors. Mean ablation zone volume was 52 mL +/- 45 (standard deviation). Thirteen patients were treated with a percutaneous approach; six, with an intraoperative approach. Maximum ablation size was 91 x 62 x 79 mm with the percutaneous and 73 x 98 x 74 mm with the intraoperative approach. Of the 18 completely evaluable ablation zones, 13 were concentric, two were moderately eccentric, two were eccentric, and one was wedge-shaped. The multipolar RF ablation device achieves large ablation zones and has high technical effectiveness in treating hepatic tumors.

Aged↗
PubMed2005

Evaluation of MR imaging compatibility of a new intracranial pressure monitoring device.

We report our observations on MR imaging quality and functionality of a recently introduced intracranial pressure monitoring device. The device was tested at two different field strengths in a pig brain specimen to investigate MR imaging artifacts, probe function during and after MR data acquisition, and device-related temperature changes in the brain tissue. Image reading was not impaired, and probe function, although reduced, was not fully interrupted during data acquisition.

Animals↗
PubMed2004

Low contrast dose voiding urosonography in children with phase inversion imaging.

Voiding urosonography (VUS) using a microbubble contrast agent has been introduced as an alternative technique in the diagnosis of vesicoureteral reflux (VUR). This study was undertaken to assess if phase inversion ultrasound (PIUS), a recent microbubble specific imaging technique, has advantages over fundamental in VUS and if it allows a reduction of contrast agent dose. Forty-three children with suspected VUR (aged 3 days-12 years, average of 3.9 years) with 92 kidney-ureter units (KUU) were included. Everyone obtained a baseline US scan that was followed by VUS using Levovist as the contrast agent. Constant switching between fundamental and PIUS performed the enhanced part for comparison. Every child underwent VCUG immediately afterwards. Contrast enhancement was stronger and longer lasting on PIUS than on fundamental US in all 43 cases. Reflux was detected in a total of 21 KUU, out of 92 KUU (23%). PIUS revealed VUR in 18; fundamental in 14 KUU and VCUG depicted 16 cases of reflux (p> or =0.29). The mean volume of Levovist dose administered to the bladder was 7.4+/-3.4% of the bladder volume. VUS using PI mode provided considerably stronger and longer enhancement and slightly improved the detection of VUR. It allowed a reduction of contrast dose and cost by approximately 35% over current dose recommendations for fundamental US.

Child↗
PubMed2004

Multiple cerebral aneurysms in factor VII deficiency.

A rare case of multiple cerebral aneurysms and factor VII deficiency is presented. The authors hypothesize a possible combined genetic defect similar to that of other conditions with clotting disorders. Different treatment options are discussed for factor VII deficiency in particular and multiple cerebral aneurysms in general. The authors advise treatment of all detected aneurysms in case of a subarachnoid hemorrhage rather than only treatment of the ruptured aneurysms in order to immediately start the so-called triple-H therapy.

Adult↗
PubMed2003

[Risk management from the perspective of the radiation protection officer. Consequences of new radiation protection laws in hospitals].

The implications of the new radiation protection law for hospitals. The novel German radiation control regulation ("Roentgenverordnung") came into effect on July 1, 2002. It contains a number of new rules the majority of which clearly take a more restrictive approach towards the application of ionising radiation. New dose thresholds have been set for control and monitoring areas and written working instructions are now required for all areas of radiology departments. The new regulations also require the indication for a radiological examination to be checked by a radiologist who has completed a formalised training in radiation protection. This particular aspect will have serious implications for every day practice. The necessity of having a trained radiologist on site for 24 hours a day will cause problems in many hospitals. The power of the responsible external independent control body ("ärztliche Stelle") has been increased as have the duties of medical physicists. The performance of x-ray examinations that are not medically indicated is punishable by law as bodily harm. This as well as many other regulations are currently being checked for applicability in terms of guidelines, the majority of which are not yet available.

Germany↗
PubMed2002

Heterogeneous delayed enhancement of the liver after ultrasound contrast agent injection--a normal variant.

We report a characteristic heterogeneous delayed liver enhancement pattern that we have encountered in a total of 6 of approximately 1500 subjects who underwent contrast-enhanced liver ultrasonography. The heterogeneous enhancement occurred several min after contrast injection and persisted for up to 1 h. It was seen in diseased as well as healthy livers and appears to represent a "normal variant" of liver enhancement. It was observed with two different contrast agents. The cause of the described effect is unknown; it may be related to the formation of large bubbles and vascular entrapment of these bubbles in the liver.

Adult↗
PubMed2002

Neurovascular contact and blood pressure response in young, healthy, normotensive men.

BACKGROUND: Neurovascular contact (NVC) of the left rostral ventrolateral medulla has been implicated in the pathogenesis of "essential" hypertension, and recent studies suggest that this anomaly may be genetically determined. We therefore assessed the prevalence of this vascular anomaly in young normotensive volunteers. We also studied blood pressure, heart rate reactivity, and changes in baroreflex sensitivity in response to mental and physical stress in a subset of subjects with positive and negative brainstem findings. METHODS: Magnetic resonance imaging of the brainstem was performed in 113 young (aged 25 +/- 8 years), normotensive male volunteers. Baroreflex sensitivity was then assessed in 13 subjects with positive brainstem findings and 20 subjects with negative findings. RESULTS: Left-sided NVC was found in 19 subjects. Blood pressure levels, heart rate, and baroreflex sensitivity were similar in all groups. However, modulation of baroreflex sensitivity was reduced under mental and physical stress in subjects with a positive finding for NVC. Subjects with a positive finding also had a significantly lower body mass index than those with a negative finding. CONCLUSIONS: Left-sided NVC is present in approximately one-fifth of young normotensive men, and may modulate the baroreceptor reflex under stress in these individuals.

Adult↗
PubMed2002

Use of a blood-pool contrast agent for MR-guided vascular procedures: feasibility of ultrasmall superparamagnetic iron oxide particles.

RATIONALE AND OBJECTIVES: The purpose of this study was to examine the dose dependency of the intravascular signal intensity after injection of ultrasmall superparamagnetic iron oxide (USPIO) particles (SH U 555 C) in a rabbit model studied with a low-field-strength magnetic resonance (MR) imaging system. The results were used to facilitate MR-guided vascular procedures in a pig. MATERIALS AND METHODS: All experiments were performed at 0.2 T. To determine the optimum USPIO (or SH U 555 C) dose for intravascular interventions, the authors acquired coronal three-dimensional MR angiographic images in 12 rabbits after injection of four dose levels (10, 20, 30, and 40 micromol of iron per kilogram body weight). The intraaortic signal intensities were measured in user-defined regions of interest. For numerical analysis, signal intensity enhancement was computed. Subsequently MR image-guided procedures were performed in USPIO-enhanced vessels in one pig. RESULTS: The signal intensity evaluation shows a clear-cut dose dependence in both early and late phases after administration of SH U 555 C. A high-spatial-resolution MR angiogram acquired 20 minutes after injection yielded the best results with the highest dose (40 micromol of iron per kilogram); at that dose, intravascular enhancement was sufficient for vascular procedures for 60 minutes after injection. CONCLUSION: SH U 555 C is a promising contrast agent for MR angiography and MR-guided vascular procedures in an open low-field-strength MR imager.

Animals↗
PubMed2001

Neurovascular Contact of Cranial Nerve IX and X Root-Entry Zone in Hypertensive Patients.

-Neurovascular contact of the left rostral ventrolateral medulla has been implicated in the pathogenesis of "essential" hypertension, and recent intervention studies suggest that surgical decompression of the ventrolateral medulla lowers blood pressure in these patients. We assessed the prevalence of this vascular anomaly in patients with essential hypertension by using an advanced MRI technique. We performed MRI of the brain stem in 125 hypertensive patients and in 105 age-matched, sex-matched, and body mass index-matched normotensive control subjects. Imaging of the root-entry zone of cranial nerves IX and X was performed by combining a high-resolution 3D constructive interference in steady-state sequence with a flow-sensitive time-of-flight technique, and images were independently assessed by 4 readers using predefined criteria. Left-sided neurovascular contact was found in 23% of the hypertensive patients and in 16% of the normotensive individuals (P:=0.12). Blood pressure level, heart rate, and number of antihypertensive medications in treated hypertensive patients were similar among patients with positive, borderline, and negative brain stem findings. Our findings cast doubt on the importance of left-sided neurovascular contact as a frequent cause of essential hypertension or as a major factor determining the severity of hypertension in patients with this anomaly.

Journal Article↗
PubMedDate not supplied

MRI tumor characterization using Gd-GlyMe-DOTA-perfluorooctyl-mannose-conjugate (Gadofluorine M), a protein-avid contrast agent.

The rationale and objectives were to define the MRI tumor-characterizing potential of a new protein-avid contrast agent, Gd-GlyMe-DOTA-perfluorooctyl-mannose-conjugate (Gadofluorine M; Schering AG, Berlin, Germany) in a chemically induced tumor model of varying malignancy. Because of the tendency for this agent to form large micelles in water and to bind strongly to hydrophobic sites on proteins, it was hypothesized that patterns of dynamic tumor enhancement could be used to differentiate benign from malignant lesions, to grade the severity of malignancies and to define areas of tumor necrosis. Gadofluorine M, 0.05 mmol Gd kg(-1), was administered intravenously to 28 anesthetized rats that had developed over 10 months mammary tumors of varying degrees of malignancy as a consequence of intraperitoneal administration of N-ethyl-N-nitrosourea (ENU), 45-250 mg kg(-1). These tumors ranged histologically from benign fibroadenomas to highly undifferentiated adenocarcinomas. Dynamic enhancement data were analyzed kinetically using a two-compartment tumor model to generate estimates of fractional plasma volume (fPV), apparent fractional extracellular volume (fEV*) and an endothelial transfer coefficient (K(PS)) for this contrast agent. Tumors were examined microscopically for tumor type, degree of malignancy (Scarff-Bloom-Richardson score) and location of necrosis. Eighteen tumor-bearing rats were successfully imaged. MRI data showed an immediate strong and gradually increasing tumor enhancement. K(PS) and fEV*, but not fPV obtained from tumors correlated significantly (p < 0.05) with the SBR tumor grade, r = 0.65 and 0.56, respectively. Estimates for K(PS) and fEV* but not fPV were significantly lower in a group consisting of benign and low-grade malignant tumors compared with the group of less-differentiated high-grade tumors (1.61 +/- 0.64 vs 3.37 +/- 1.49, p < 0.01; 0.45 +/- 0.17 vs 0.78 +/- 0.24, p < 0.01; and 0.076 +/- 0.048 vs 0.121 +/- 0.088, p = 0.24, respectively). It is concluded that the protein-avid MRI contrast agent Gadofluorine M enhances tumors of varying malignancy depending on the tumor grade, higher contrast agent accumulation for more malignant lesions. The results show potential utility for differentiating benign and low-grade malignant lesions from high-grade cancers.

Adenocarcinoma↗