[Endovascular treatment of a thoracic aneurysm of the aorta with a novel coated stent].
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Aged↗
Biomedical subjects
W A Kaiser
Publications and source records attributed to W A Kaiser.
[In vitro studies to determine the degree of stenosis using spiral CT angiography].
UNLABELLED: Aim of the study was to evaluate the influence of different spiral-CT parameters for the visualisation of vascular stenoses, especially of the renal arteries. MATERIAL AND METHODS: Models with a density equivalent to that of fat, filled with diluted contrast agent, and an inner lumen of 4, 6, 8 mm were scanned in x-, y- and z-direction. Data were acquired in up to 24 second long spiral-CT scans using different spiral-CT parameters (collimation, table speed, reconstruction algorithm, tube current). Detection of the degree of stenosis was achieved by assessment of the axial images and 3D reconstructions. RESULTS: The best correlation between real and measured degree of stenosis was seen by using a small collimation, a low table increment and assessment of the axial images reconstructed in standard algorithm. The stenosis degrees of models directed in x- and y-direction were overestimated and those in z-direction were underestimated depending on the spiral-CT parameters. CONCLUSION: For optimal imaging of renal artery stenoses, collimation of 2 mm (pitch = 1-2 and a reconstruction interval of 1 mm is recommended.
Algorithms↗
31P-magnetic resonance spectroscopy (31P-MRS) of human allografts after renal transplantation.
BACKGROUND: 31P-Magnetic resonance spectroscopy (31P-MRS) can be used as a non-invasive tool for measuring the relative intracellular concentrations of several phosphorus metabolites in different organs. Various pathological conditions are characterized by different metabolic patterns. We studied the value of 31P-MRS after renal transplantation with both an uneventful and a clinically complicated course. METHODS: We determined the relative concentrations of phosphate-containing metabolites in renal allografts of humans with 31P-MRS (1.5 Tesla) in the first few weeks after transplantation; 18 patients with an uneventful clinical course and 10 patients who required dialysis after transplantation were examined. Six patients with a stable allograft function 2-3 months after transplantation served as controls. RESULTS: In patients with primary allograft function, we found a significant correlation between the phosphomonoester/phosphodiester-ratio (PME/PDE) (r = 0.66, r < 0.01) and the time after transplantation, but no correlation between the nucleoside triphosphate (beta-NTP)-concentration (r = -0.11) and the time course. In the patients with primary or early allograft dysfunction caused by histologically proven rejection (n=5), we found a low beta-NTP compared to patients with an uncomplicated clinical course (0.09+/-0.01 vs 0.15+/-0.03), but no differences in the PME/PDE ratio (0.73+/-0.21 vs 0.80+/-0.21). In contrast, the PME/PDE ratio was lowered in three patients with delayed graft function caused by acute tubular necrosis (0.45+/-0.07 vs 0.80+/-0.21), but the beta-NTP concentration was not reduced (0.15+/-0.003 vs 0.15+/-0.03). The 31P-MR spectrum of two patients with cyclosporin A damage was not altered compared to the controls. CONCLUSIONS: 31P-MRS can be used in patients in the early period after renal transplantation. A significant correlation between the PME/PDE ratio and the time course but no change in the beta-NTP concentration was found in patients with primary allograft function in the first 4 weeks after renal transplantation. Different patterns of 31P-MR spectra were observed depending on the different causes of primary and early transplant dysfunction.
Adult↗
Diagnostic evaluation of sonographically visualized breast lesions by using a new clinical amplitude/velocity reference imaging technique (CARI sonography).
RATIONALE AND OBJECTIVES: The goal of this study was to evaluate and differentiate breast lesions in patients by sonographic measurements performed using CARI sonography. METHODS: Thirty-one patients with 33 histologically proven breast lesions were examined by mammography, conventional ultrasound sonography, and CARI sonography. Investigation with mammography-like positioning was performed in case of CARI sonography. The ratios of the lesion diameters were calculated in a craniocaudal and a mediolateral plane. The results were compared with the results obtained with conventional modalities. RESULTS: Breast lesions were detected with the best sensitivity (100%) and a high specificity (86%) using B-mode ultrasound sonography. Mammography resulted in a sensitivity of 92% and a specificity of 91%, whereas the CARI sonography yielded 100% sensitivity and 67% specificity. CONCLUSIONS: The differentiation of lesions by measurements performed with CARI sonography resulted in a high sensitivity. The specificity, however, was inferior compared with the other imaging modalities. This may limit the routine application of the technique for clinical diagnoses of breast lesions. However, due to the small number of patients investigated in this pilot study, the full potential should be evaluated in a larger collective of patients.
Adult↗
Cognitive stimulation with the Wisconsin Card Sorting Test: functional MR imaging at 1.5 T.
PURPOSE: To determine whether functional magnetic resonance (MR) imaging can demonstrate a specific pattern of cerebral activation during cognitive stimulation by using a high-level cognitive task such as the Wisconsin Card Sorting Test. MATERIALS AND METHODS: Thirty-one healthy volunteers underwent functional MR imaging with a 1.5-T MR imager with a standard head coil (100/50 [repetition time msec/echo time msec], 230-mm field of view, 40 degrees flip angle, 256 x 256 matrix). For stimulation, a personal computer version of the Wisconsin Card Sorting Test was used. Image analysis was done off-line, and cross-correlation coefficients between the stimulus function and the signal intensity response were calculated on a pixel-by-pixel basis and overlaid onto the corresponding anatomic MR image for each volunteer. RESULTS: Stimulation resulted in strongly frontal activation, which included the mesial and the dorsolateral prefrontal cortexes, interconnected with Brodmann areas 44, 45, and 46. While activation was often bilateral, the largest area of activation was in the right hemisphere. Activation also was found in the basal ganglia and the mesial thalamic nuclei. CONCLUSION: Functional MR imaging can demonstrate a specific pattern during activation with a cognitive task. Functional MR imaging has promise for more precise anatomic and functional imaging studies of brain interaction than have other imaging modalities.
Adult↗
Decreased energy demanding processes in the frontal lobes of schizophrenics due to neuroleptics? A 31P-magneto-resonance spectroscopic study.
In the present investigation on 31P-magneto-resonance spectroscopic parameters in the frontal lobe, we found phosphocreatine levels and the ratio phosphocreatine/adenosine triphosphate to be increased (12.62 +/- 1.98% resp. 0.31 +/- 0.06) in 50 neuroleptic-treated schizophrenics, whereas no differences were detected in 10 neuroleptic-free patients (11.66 +/- 2.57% resp. 0.29 +/- 0.08) compared to 36 controls (11.37 +/- 1.45 resp. 0.29 +/- 0.04). This result points to a major role of neuroleptics in the metabolism of high-energy phosphates.
Adenosine Triphosphate↗
Brain activation during cognitive stimulation with the Wisconsin Card Sorting Test--a functional MRI study on healthy volunteers and schizophrenics.
It has been demonstrated by single photon emission computed tomography (SPECT) and positron emission tomography (PET) that frontal brain regions are stimulated during performance of the Wisconsin Card Sorting Test (WCST). The WCST is also regarded as one of the standard tests for the assessment of frontal activity in brain imaging studies of schizophrenia. In this study cerebral activation was assessed by means of functional magnetic resonance imaging (fMRI). In healthy volunteers WCST stimulation resulted in a right lateralized frontal activation. In 13 chronic schizophrenics on stable neuroleptic medication, a lack of activation in the right prefrontal cortex and--as a trend--an increased left temporal activity during execution of the WCST was noted compared to controls. Since a one-slice technique was used, no information about the activation pattern in adjacent brain regions was obtained. However, as fMRI possesses a superior spatial resolution compared to SPECT and PET, the anatomical localization of the activation effect in the measured slice can be defined more precisely. Beside these methodological considerations, the results are discussed in relation to prior findings of a reduced ability of schizophrenics to coordinate cerebral function.
Adult↗
31P magnetic resonance spectroscopy in the dorsolateral prefrontal cortex of schizophrenics with a volume selective technique--preliminary findings.
Pettegrew et al (Arch Gen Psychiatry 48:563-568, 1991) were the first to determine abnormalities concerning phospholipids and high energy metabolites in the dorsolateral prefrontal cortex of drug-naive schizophrenics with 31P magnetic resonance spectroscopy (MRS). Other investigations could not replicate these findings. We included in our study 13 schizophrenic inpatients and 14 age-matched controls. Whereas Pettegrew et al found increased levels of phosphodiesters and decreased levels of phosphomonoesters we measured decreased levels of phosphodiesters in the schizophrenics as compared to controls. One possible explanation for the contradictory findings of the both trials might be the different localization techniques used.
Adult↗
[Indications for intravenous urography].
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Adult↗
[MR venography of the deep leg veins: signal enhancement by volume infusion].
PURPOSE: To enhance flow signals in the deep veins of the lower extremity by means of a drip infusion. METHODS: Saline solution and diluted contrast media were consecutively administered in 8 healthy volunteers by drip infusion (3 ml/min) via the cubital vein. Imaging of the deep veins in both legs was performed using a gradient echo sequence with flow compensation. Changes of the intravascular signal-to-noise-ratio (SNR) were correlated with the duration of the drip infusion. RESULTS: Improved SNR were detected in each level examined in both thigh and calf. SNR increases up to 157% were opposed to decreases of less than 16%. The average rise of SNR was up to 55% in the calf veins. CONCLUSION: Saline drip infusion is a simple and valuable method for enhancement of venous flow signals and should be administered routinely in time-of-flight venographies.
Adult↗
[Radiation exposure of the ocular lens and thyroid gland in digital subtraction angiography of brain-supplying arteries].
PURPOSE: To find out the individual level of radiation exposure of the ocular lens and thyroid gland during DSA of arteries supplying the brain, considering the indication. MATERIAL AND METHOD: The study was conducted on 72 patients during aortic arch and cerebral artery angiographies using thermoluminescent dosimetry. RESULTS: During 20 aortic arch angiographies the measured values were within non-critical limits, whereas during carotid, vertebral or cerebral four-vessel angiography of the left ocular lens exposure values of more than 500 mGy (max. 782 mGy) were stated in two of 52 cases. The highest measured exposure relating to the right ocular lens was 126 mGy, to the thyroid gland 88 mGy. However, in 51 of 52 cases thyroid gland doses of below 51 mGy were measured. In 71 of 72 cases there was a lateral difference between right and left lens exposure up to twice the measured dose for the right ocular lens during aortic arch angiographies and up to sixteen-fold in respect of the left lens during cerebral angiographies. CONCLUSION: In addition to the fluoroscopic time, number of images, fade-in and zoom some other dose-influencing factors, radiation geometry is especially decisive for organ exposure. The risk of cataracts or thyroid gland carcinomas/hypothyrosis can be neglected with median values of 40 and 70 mGy relating to the ocular lens and 17 mGy for the thyroid gland during cerebral angiographies.
Angiography, Digital Subtraction↗
Evaluation of temperature increase with different amounts of magnetite in liver tissue samples.
RATIONALE AND OBJECTIVES: The biologic effects of magnetically induced heating effects using iron oxide, magnetite, were examined in vitro in liver tissue samples as a first step toward potential applications in cancer therapy. METHODS: For the determination of the temperature profile around an iron oxide sample, a cylinder containing 170 mg of magnetite was constructed and placed into pureed liver tissue from pig, together with thermocouples of copper and constantan wires positioned at defined distances from it. Temperature measurements were performed during the exposure to an alternating magnetic field (frequency: 400 kHz; amplitude: approximately 6.5 kA/m) generated by a circular coil (90 mm of diameter). Moreover, variable amounts of magnetite (dissolved in approximately 0.2 mL physiologic saline) were injected directly into carrageenan gels. During the exposure to a magnetic field for 4 minutes the temperature increase was determined in the area of iron oxide deposition using a thermocouple. Additionally, variable amounts of magnetite were injected directly into isolated liver tissue samples (diameter: 20 mm; height: 30 mm) and exposed to a magnetic field for 2 minutes. The extent of the induced macroscopically visible tissue alterations (light brown colorations caused by heating) was examined by means of volume estimations. The degrees of cellular necrosis were investigated by histopathologic studies. RESULTS: The temperature profile around a magnetite cylinder revealed a significant decrease of temperature difference between the beginning and the end of heating, depending on increasing distance from the sample center. The extent of the temperature difference correlated with increasing heating time. No significant variations of temperature were observed at a distance of approximately 12 mm from the sample center. A good correlation (r = 0.98) between the injected amounts (31 to 200 mg) and the temperature increase since the start of heating (6.8-33.7 degrees C) in the area of iron oxide deposits was detected. The volume of damaged liver tissue was approximately seven times higher than the injected volume of iron oxide dispersion. Histologically different degrees of cellular necrosis were observed. CONCLUSIONS: The parameters determined in this article show that iron oxides are able to induce considerable heating effects in the surroundings. After an adequate optimization of the technical procedure, it is conceivable that heating properties of magnetites can be used in future cancer treatments.
Animals↗
[Patient screening for MRI with SQUID biomagnetometers].
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Contraindications↗
[Hyperthermic treatment of tumor tissue using iron(II,III)-oxide].
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Animals↗
[MR mammography--a critical stocktaking].
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Breast↗
[Contrast medium supported imaging of tumorous vessels by color Doppler and power Doppler mode in animal experiments].
PURPOSE: The purpose was to determine tumor neovascularisation via colour-coded Doppler (duplex) sonography and the "power mode", both visually and quantitatively, by means of videodensitometry. MATERIAL AND METHODS: 6 VX2 tumours of 4 to 11 mm size were implanted in 4 rabbits at various sites. The colour-coded duplex sonography and the new sonographic power technique were tested before and after having injected a new contrast medium (SH U 616A). RESULTS: If no contrast medium was injected, tumour neovascularisation was identified in only 50% of the cases. Injection of contrast medium increased signal intensity three to fourfold with all examined tumors. Combined use of the sonographic method by the power technique with injection of contrast medium is outstandingly suitable for tumor vessel imaging even of small tumors, as these initial results seem to show. CONCLUSION: If these results are corroborated by further studies, contrast-medium supported sonographic technique may possibly become established as an alternative method to other imaging procedures.
Adipose Tissue↗
[Color coded ultrasound--quantification of perfusion in a perfusion model].
This experimental study demonstrates the quantification of perfusion in a phantom-simulating tissue using a computer-assisted interpretation. The parameters flow volumin, velocity (defined by pulse-repetition-frequency-PRF), and the time of adding up peaks were varied. The detected color-coded pixels determine the flow area as a percentage of the ground area and the frequency with the highest pixel density. The width is the area between the highest and lowest detected frequencies. The flow area correlates with the perfusion rate (r > or = 0.97). To detect low perfusions, a slow velocity and extended Peak Hold-function are necessary. Peaks with a high frequency superpose those with lower frequencies, so that these signals are not available for the interpretation. To determine the width or the frequency with highest pixel density a short Peak Hold-function must be chosen. When changing the velocity, these quantities are also changed, so that standards are necessary. This study shows a correlation between a defined perfusion in a phantom-simulating tissue and the flow area. It suggests a possibility to quantify flow in different organs. One aim would be to determine abnormal vascularisation, for example, in tumours of the liver or breast.
Blood Flow Velocity↗
Serial magnetic resonance imaging in juvenile dermatomyositis--delayed normalization.
Demonstration of myositis in juvenile dermatomyositis (JDM) has traditionally required the presence of two out of three objective findings including muscle enzyme studies, electromyography, and muscle biopsy. Magnetic resonance imaging (MRI) is considered another objective criterion and has been recommended for follow-up studies as well. We report on a 6-year-old girl with JDM, presenting with facial rash and proximal muscle weakness, in whom MRI, in conjunction with elevated creatinine kinase (CK) levels, was diagnostic, with an increased T2 signal of proximal muscles. MRI reflected exacerbation of myositis in spite of steroid therapy 2 weeks later, but failed to mirror normalization of muscle strength and CK values 10 weeks later. In fact, improvement of MRI followed clinical and laboratory normalization with a delay of 2 months. This possible delay should be considered when MRI is used to monitor the response to therapy.
Child↗