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Biomedical subjects

C U Herborn

Publications and source records attributed to C U Herborn.

15 recordsLinked to original sources
PubMed2006

[Osteosynthesis in facial bones: silicon nitride ceramic as material].

BACKGROUND: The favorable properties of silicon nitride (Si3N4) ceramic, such as high stability and biocompatibility suggest its biomedical use as an implant material. The aim of this study was to test its suitability for osteosynthesis. MATERIALS AND METHODS: A Si3N4 prototype minifixation system was manufactured and implanted for osteosynthesis of artificial frontal bone defects in three minipigs. After 3 months, histological sections, CT and MRI scans were obtained. Finite element modeling (FEM) was used to simulate stresses and strains on Si3N4 miniplates and screws to calculate survival probabilities. RESULTS: Si3N4 miniplates and screws showed satisfactory intraoperative workability. There was no implant loss, displacement or fracture. Bone healing was complete in all animals and formation of new bone was observed in direct contact to the implants. CONCLUSIONS: Si3N4 ceramic showed a good biocompatibility outcome both in vitro and in vivo. This ceramic may serve as biomaterial for osteosynthesis, e.g. of the midface including reconstruction of the floor of the orbit and the skull base. Advantages compared to titanium are no risk of implantation to bone with mucosal attachment, no need for explantation, no interference with radiological imaging.

Animals↗
PubMed2005

Whole body positron emission tomography/computed tomography (PET/CT) tumour staging with integrated PET/CT colonography: technical feasibility and first experiences in patients with colorectal cancer.

AIM: The aim of this study was to implement an imaging protocol for positron emission tomography/computed tomography (PET/CT) colonography and to combine this protocol with whole body PET/CT tumour staging for a single whole body examination for routine clinical use. SUBJECTS AND METHODS: A whole body PET/CT protocol for tumour staging and a protocol for PET/CT colonography were integrated into one examination. Fourteen prospective patients with suspected colorectal cancer underwent whole body PET/CT after aqueous bowel distension and pharmacological bowel relaxation. Colonoscopy and histopathology served as the standards of reference in all patients. RESULTS: The modified PET/CT examination detected all but one lesion in the colon. One additional lesion was detected in a patient with incomplete colonoscopy due to high grade luminal stenosis. One polyp with malignant conversion was identified with the modified PET/CT protocol. PET/CT colonography proved accurate in local lymph node staging and staged nine out of 11 patients correctly. Six additional extracolonic tumour sites were detected based on the whole body staging approach. CONCLUSION: Whole body PET/CT with integrated colonography is technically feasible for whole body staging in patients with colorectal cancer. Based on these initial diagnostic experiences, this integrated protocol may be of substantial benefit in staging patients with colorectal cancer, focusing on patients with incomplete colonoscopy and those with small synchronous bowel lesions.

Aged↗
PubMed2004

[Cardiovascular whole-body MRI: possibilities and limitations in prevention].

Cardiovascular disease is a major challenge to the healthcare with increasing prevalence in western societies. Hence, early detection of cardiovascular pathologies and preventative strategies will experience growing relevance in the future. Magnetic resonance imaging (MRI) nowadays allows a comprehensive analysis of the cardiovascular system. By combining separate examinations of brain, arterial vasculature, and heart the technique permits early detection of pathological changes with high diagnostic accuracy void of adverse events. Such a protocol has been proven feasible and technically robust and can be performed within 45 min. Inherent limitations are low spatial resolution of whole-body MR angiography and lack of functional stress testing of the heart. However, while being suitable as a fast and comprehensive imaging technique for cardiovascular screening purposes, medical consequences and socioeconomic relevance must further be elucidated.

Adult↗
PubMed2004

Optimization of contrast-enhanced peripheral MR angiography with mid-femoral venous compression (VENCO).

PURPOSE: To compare a standard protocol for contrast-enhanced three-dimensional magnetic resonance angiography (3D CE-MRA) of the lower extremities to a high spatial resolution protocol with venous compression (VENCO) at the mid-femoral level. MATERIAL AND METHODS: 12 patients with peripheral arterial occlusive disease (8-males; age range, 52 - 74 years; mean 67.1 years; 4 females; age range, 57 - 71 years; mean 62.1 years) were examined once with a standard MR angiography (MRA) protocol, and a second time with a high spatial resolution protocol in combination with mid-femoral venous compression (60 mm Hg) for the last two stations. All imaging was performed on a 1.5 T whole-body MR scanner (Magnetom Sonata, Siemens Medical Solutions, Erlangen, Germany) using a dedicated coil and paramagnetic contrast agent (gadodiamide, Omniscan, Amersham, Oslo, Norway). Signal-to-noise ratios (SNR) and contrast-to-noise ratios (CNR) were calculated and image quality as well as venous overlay were assessed on a five-point scale for both examinations. Statistical significance was established at p < 0.05. RESULTS: Mean SNR and CNR values of the two lower stations with VENCO were statistically significantly higher in comparison to the standard protocol (66 +/- 8 vs. 52 +/- 11 and 53 +/- 9 vs. 41 +/- 8, respectively; p < 0.01). The same was true for overall image quality with VENCO (4.0 +/- 0.2 vs. 3.4 +/- 0.8; p < 0.05) and presence of venous overlay (3.5 +/- 0.4 vs. 4.1 +/- 0.9; p < 0.05), respectively. CONCLUSION: VENCO 3D CE-MRA is simple to put into practice and advances the performance of multi-station MRA strategies for assessment of the peripheral arterial vasculature.

Aged↗
PubMed2004

High spatial resolution whole-body MR angiography featuring parallel imaging: initial experience.

PURPOSE: To combine whole-body multi-station three-dimensional contrast enhanced magnetic resonance angiography (3D CE MRA) using a self-developed rolling table platform with parallel imaging strategies (PAT) in order to increase the spatial resolution of the 3D MRA data sets. MATERIALS AND METHODS: Whole-body multi-station MRA was performed with a rolling table platform (AngioSURF) on 5 volunteers in two imaging series: 1) standard imaging protocol, 2) modified high-resolution protocol employing PAT using the generalized autocalibrating partially parallel acquisitions (GRAPPA) algorithm with an acceleration factor of 3. For an intra-individual comparison of the two MR examinations, the arterial vasculature was divided into 30 segments. Signal-to-noise ratios (SNR) and contrast-to-noise ratios (CNR) were calculated for all 30 arterial segments of each subject. Vessel segment depiction was qualitatively assessed applying a 5-point scale to each of the segments. Image reconstruction times were recorded for the standard as well as the PAT protocol. RESULTS: Compared to the standard protocol, PAT allowed for increased spatial resolution through a 3-fold reduction in mean voxel size for each of the 5 stations. Mean SNR and CNR values over all specified vessel segments decreased by a factor of 1.58 and 1.56, respectively. Despite the reduced SNR and CNR, the depiction of all specified vessel segments increased in PAT images, reflecting the increased spatial resolution. Qualitative comparison of standard and PAT images showed an increase in vessel segment conspicuity with more detailed depiction of intramuscular arterial branches in all volunteers. The time for image data reconstruction of all 5 stations was significantly increased from about 10 minutes to 40 minutes when using the PAT acquisition. CONCLUSION: The implementation of PAT into the concept of whole-body MRA enabled to increase the spatial resolution in all examined territories, which resulted in more detailed MR angiograms.

Adult↗
PubMed2003

Geometrical optimization of a phased array coil for high-resolution MR imaging of the carotid arteries.

The geometry of an RF phased-array receiving coil for high-resolution MRI of the carotid artery, particularly the bifurcation, was optimized with respect to signal-to-noise ratio (SNR). A simulation tool was developed to determine homogeneity, sensitivity, and SNR for a given imaging situation. The algorithm takes into account the coil geometry, the parameters of the measured object, and the imaging parameters of the pulse sequence. The coil with the optimum geometry was implemented as a receive-only coil for 1.5 T and comparative SNR measurements with different coils were performed. The experimental SNR measurements verified the simulations. The optimized carotid artery phased array offered the best SNR over the desired field of view. In vivo high-resolution MRI of the carotid arteries of healthy volunteers and patients with known stenosis was conducted with the optimized phased array coil. The capability of the phased array coil for resolving components within the carotid artery walls is demonstrated. Magn Reson Med 50:439-443, 2003.

Carotid Artery, Common↗
PubMed2003

[Magnetosomes as biological model for iron binding: relaxivity determination with MRI].

PURPOSE: In vitro characterization of iron-containing bacterial particles (magnetosomes) as superparamagnetic contrast agents for MRI. MATERIAL AND METHODS: Different concentrations of magnetosomes were examined with a 1.5 T clinical whole-body MR system at 21 degrees C using the transit/receive extremity coil. Both longitudinal and transversal relaxivities (R1 and R2) of the magnetosomes were determined by an inversion recovery snapshot gradient recall echo (IR FLASH) with various inversion times and a multi echo spin echo sequence. Atomic absorption spectrometry (AAS) and electron microscopy were used as reference standard. RESULTS: Longitudinal and transverse relaxivities of the magnetosomes were calculated to be R1 = 7.688 mmol -1 s -1 and R2 = 147.67 mmol -1 s -1, respectively. The corresponding iron concentrations were determined in all dilutions using AAS, while the magnetosomes were morphologically delineated by electron microscopy. CONCLUSION: Magnetosomes represent a new and interesting class of iron-containing contrast agents warranting further evaluation in cellular cultures and animal models. Magnetosomes may be suited for displaying the vector distribution and gene expression of new molecular therapies.

Contrast Media↗
PubMed2001

0.5 M Gd chelate (Magnevist) versus 1.0 M Gd chelate (Gadovist): dose-independent effect on image quality of pelvic three-dimensional MR-angiography.

To compare the effect on image quality of a 1.0 M gadolinium (Gd) chelate to that of a conventional 0.5 M Gd chelate, five healthy volunteers and seven patients with angiographically documented aorto-iliac disease underwent a mono-station three-dimensional magnetic resonance angiography (MRA) exam (Siemens SONATA, Erlangen, Germany) twice, once using Gadovist 1.0 and the other time using Magnevist as the contrast agent. All subjects received a fixed volume of Gadovist 1.0, corresponding to a dose between 0.1 and 0.15 mmol/kg body weight followed by a saline flush. For the Magnevist exam, the contrast agent volumes and flow rates were doubled. For both quantitative and qualitative analysis of the angiographic data sets, the arterial tree was divided into nine segments. 1 M Gadovist 1.0-enhanced three-dimensional MRA data sets were characterized by significantly higher signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) values compared to 0.5 M Magnevist-enhanced images. The data revealed mean SNR/CNR increases exceeding 70% (P < 0.01). Although there was no statistically significant difference in the rating of image quality (P > 0.05), the Gadovist 1.0 exam led to better delineation of the arterial morphology, especially of small vessels.

Adult↗
PubMed2001

Clustered microcalcification following breast implant removal mimicking malignancy.

On mammography, clustered microcalcification can be an early and sensitive sign of malignancy, although it is also commonly seen in benign alterations of the breast. We report on a 52-year-old woman with mammographically suspicious granular calcification as a late result of a short-term silicone augmentation. Plain film, surgical, and histopathological features are demonstrated.

Breast Diseases↗
PubMed2001

Dark lumen MR-colonography: initial experience.

PURPOSE: The aim of this study was to assess a new strategy of MR colonography for the detection of colonic polyps/malignancy. The technique is based on a rectal enema with water in combination with the intravenous application of a paramagnetic contrast agent. METHODS: Twelve subjects were included in this study either due to suspected colorectal tumors or for screening purposes. For MR colonography the colon was filled with approximately 3000 ml of tap water while Gadobenate dimeglumine (0.2 mmol/kg) was injected intravenously. A T1w GRE sequence was acquired before and 75 sec after the contrast administration only in prone position. Three patient underwent the "bright lumen" MRC as well. All MR examinations were performed at least five days prior to conventional colonoscopy and the results of both modalities were compared. RESULTS: The colonic filling with water resulted in a homogeneously low signal throughout the colonic lumen in all twelve subjects. Intravenous injection of gadolinium caused avid enhancement of the colonic wall. Similarly lesions arising from the colonic wall enhanced avidly. Dark lumen MR colonography correctly identified five polyps in four patients. Bright lumen MRC showed in one patient false positive results. CONCLUSION: The new MR colonography concept based on a dark colonic lumen and a bright, contrast enhanced colonic wall turned out to be a promising alternative to the traditional MRC based on a bright lumen concept. The new technique suggests a higher accuracy in detecting polyps, a better evaluation of other parenchymal organs as well as a reduced time needed for data acquisition and analysis.

Adult↗