MR-guided periarterial ethanol injection for renal sympathetic denervation: a feasibility study in pigs.

PURPOSE: To evaluate the feasibility and efficacy of image-guided periarterial ethanol injection as an alternative to transluminal radiofrequency ablation. METHODS: Unilateral renal periarterial ethanol injection was performed under general anesthesia in 6 pigs with the contralateral kidney serving as control. All interventions were performed in an open 1.0 T MRI system under real-time multiplanar guidance. The injected volume was 5 ml (95 % ethanol labelled marked MR contrast medium) in 2 pigs and 10 ml in 4 pigs. Four weeks after treatment, the pigs underwent MRI including MRA and were killed. Norepinephrine (NE) concentration in the renal parenchyma served as a surrogate parameter to analyze the efficacy of sympathetic denervation. In addition, the renal artery and sympathetic nerves were examined histologically to identify evidence of vascular and neural injury. RESULTS: In pigs treated with 10 ml ethanol, treatment resulted in neural degeneration. We found a significant reduction of NE concentration in the kidney parenchyma of 53 % (p < 0.02) compared with the untreated contralateral kidney. In pigs treated with 5 ml ethanol, no significant changes in histology or NE were observed. There was no evidence of renal arterial stenosis in MRI, macroscopy or histology in any pig. CONCLUSION: MR-guided periarterial ethanol injection was feasible and efficient for renal sympathetic denervation in a swine model. This technique may be a promising alternative to the catheter-based approach in the treatment of resistant arterial hypertension.

[Virtual cystoscopy with reduced tube current: an alternative to cystoscopy?]. / Virtuelle Zystoskopie mit reduziertem Röhrenstrom: Eine Alternative zur Zystoskopie?

PURPOSE: Virtual cystoscopy at different mAs settings in patients with tumors of the bladder in comparison with cystoscopy and axial CT. MATERIALS AND METHODS: The study included 28 patients with bladder tumors and 28 patients without tumors as control group. The bladder was distended with air and scanned at two different mAs settings (protocol 1 and 2). The radiation exposure was reduced by 82 % for protocol 2 in comparison with protocol 1. Three readers compared virtual cystoscopy with cystoscopy and axial CT as to tumor location and size. Sensitivity, specificity and accuracy were calculated. RESULTS: Of the 47 tumors seen at cystoscopy, all readers detected 45 tumors by virtual cystoscopy using protocol 1 and 44 tumors using protocol 2, with p > 0.05 in comparison with cystoscopy. Virtual cystoscopy showed higher sensitivity than axial CT (97.2 % vs. 86.5 % for protocol 1) and (96.5 % vs. 86.5 % for protocol 2) with the same specificity (100 %). The accuracy was 0.982 for protocol 1 and 0.978 for protocol 2. In comparison with virtual cystoscopy, axial CT shoved more often over- and underestimation of the tumor size. CONCLUSION: Virtual cystoscopy at reduced mAs setting is a modality suitable for the detection of polypoid tumors, but does not provide data of the mucosa and thus cannot replace cystoscopy yet.

Diagnostic potential of virtual cystoscopy of the bladder: MRI vs CT. Preliminary report.

The aim of the study was to evaluate the diagnostic potential of the half-Fourier acquired single-shot turbo spin echo (HASTE) sequence for MRI cystoscopy compared with CT cystoscopy and the gold standard conventional cystoscopy. The MRI- and CT cystoscopy was performed in 29 patients with bladder tumors documented at cystoscopy and a control group using a 1.5-T unit (6-mm slice thickness) and a helical CT (3-mm collimation, pitch 1) after filling the bladder with air. Axial MRI and CT images were transferred to a workstation for application of virtual cystoscopy and compared with routine cystoscopy. Axial images and virtual cystoscopies were read by three readers for size and location of tumors. Forty-seven tumors were diagnosed at cystoscopy (12<1 cm, 35>/=1 cm). The sensitivity for detection of tumors smaller than 1 cm was 88.9% at MRI cystoscopy and 100% for tumors of 1 cm or larger. These results were not statistically different from the other modalities. Three tumors smaller than 1 cm were not detected at CT cystoscopy, four not all identical at MRI cystoscopy. One tumor with a wall thickening was detected on axial CT and MR images and CT cystoscopy by all observers, but only by two at MRI cystoscopy. The MRI cystoscopy is a diagnostic modality with results comparable to conventional and CT cystoscopy.

Virtual cystoscopy of the bladder based on CT and MRI data.

Carcinoma of the bladder can be a serious and complex condition that is not always easy to diagnose with radiologic methods. Numerous investigations are available to establish the diagnosis and demonstrate extravesical manifestations. This article updates the role of virtual cystoscopy based on computed tomographic (CT) data at different dose levels and magnetic resonance imaging (MRI) data in the diagnosis of the carcinoma of the bladder. The appearances of normal bladder and polypoid bladder carcinoma are shown. Factors for improvement of both virtual procedures are presented and pitfalls are discussed. New developments in CT, MRI, and postprocessing procedures are discussed. The value of virtual cystoscopy in sizing, localizing, and staging of bladder carcinoma is described and compared with cystoscopy, axial CT, and MRI.

Digital selenium radiography: anti-scatter grid for chest radiography in a clinical study.

The purpose of this study was to evaluate the diagnostic performance of an additional stationary anti-scatter grid in digital selenium radiography (DSR) compared with images acquired with only an air gap. Chest radiographs were obtained with DSR in 100 patients with and without an anti-scatter grid. Four observers scored 12 anatomical landmarks, catheters and wire cerclages for their visualization in both subsets of images. Statistical analysis was performed using a paired t-test. Anatomical landmarks, catheters and wire cerclages were statistically better visualized in regions of high attenuation when the images were performed with an anti-scatter grid. No statistically significant difference was noted for peripheral regions, nor for sex and weight of the patient between the two modalities. Therefore, an anti-scatter grid is not recommended for chest radiography as it increases the radiation exposure of patients without having a significant impact on visualization for all regions of the chest.

Diagnostic potential of virtual bronchoscopy: advantages in comparison with axial CT slices, MPR and mIP?

The aim of this study was to evaluate the diagnostic potential of virtual endoscopy (VE) and to compare it with axial CT slices, multiplanar reconstructions (MPR), minimal intensity projections (mIP), and bronchoscopy in patients diagnosed with bronchogenic carcinoma. Thirty patients underwent a spiral CT. Axial CT images were transferred to an Onyx workstation (Silicon Graphics, Sun Microsystems, Mountain View, Calif.) for performing virtual endoscopy. Accuracy for this procedure was tested by three radiologists on a monitor in comparison with axial CT slices, MPR, mIP, and bronchoscopy concerning the localization and degree of stenoses. Endoluminal tumors were identified by virtual bronchoscopy with no statistically significant difference of localization or grading of stenosis in comparison with bronchoscopy, axial CT slices, MPR and mIP. Axial CT slices, MPR, and mIP showed poorer results with over- or underestimation of stenoses compared with VE and bronchoscopy. Passing of stenoses was only possible with VE in 5 patients. Virtual endoscopy is a non-invasive method for identification of endoluminal tumors and is comparable to real bronchoscopy.

Prospectively randomized evaluation of stentless versus conventional biological aortic valves: impact on early regression of left ventricular hypertrophy.

BACKGROUND: The aim of this prospectively randomized study was to evaluate left ventricular hypertrophy and its regression after stentless versus conventional biological aortic valve replacement. METHODS AND RESULTS: From March 1996 through April 1998, 180 patients were prospectively selected; 106 patients received a stentless aortic valve (SAV), and 74 received a conventional stented bioprosthesis (CSB). Of these patients, 95% and 96%, respectively, had aortic stenosis. Their mean age was 72.3 and 74.8 years, and there were no significant differences in left ventricular function, preoperative pressure gradients, and NYHA functional status. Aortic annulus diameter indexes were comparable at 13.46 (SAV) versus 13.55 (CSB) mm (P=NS). Larger SAVs were implanted because of the oversizing technique. In-hospital mortality (n=3 and 1 for SAV and CSB) was not valve related. At follow-up, all patients were in NYHA class 1 or 2. Baseline end-diastolic left ventricular posterior wall thickness was 15.6 (SAV) and 14.8(CSB) mm (P=NS) and decreased to 11. 8 (SAV) and 13.2 (CSB) mm (P<0.05) at 6 months. Left ventricular mass index was 213 and 202 g/m(2) at baseline (P=NS), whereas after 6 months, it was 141 (SAV) and 170 (CSB) g/m(2) (P<0.05). CONCLUSIONS: Regression of left ventricular hypertrophy occurs in all patients after aortic valve replacement but is significantly enhanced after SAV implantation. This possibly is due to improved transvalvular hemodynamics.

Detection of simulated interstitial lung disease and catheters with selenium, storage phosphor, and film-based radiography.

PURPOSE: To evaluate the diagnostic performance of storage phosphor and digital selenium radiography (DSR) with asymmetric and symmetric screen-film systems at different speeds in the detection of simulated interstitial lung disease and catheters. MATERIALS AND METHODS: Patterns of simulated interstitial lung disease and catheters were superimposed over an anthropomorphic chest phantom. Hard-copy images were generated at DSR (200-, 400-, and 600-speed), storage phosphor radiography (200- and 400-speed), and asymmetric (400-speed) and symmetric (200- and 400-speed) screen-film imaging. Surface doses were measured, and receiver operating characteristic analyses were performed. RESULTS: No statistically significant differences were found between the detector systems with the same speeds for each interstitial pattern. Significantly poorer results were found at 600-speed DSR than at 200-speed DSR. Detection of catheters and nodules over high-attenuation areas was significantly worse with the symmetric screen-film system than with the other detectors. The surface dose with the DSR system, without a grid, was about 50% less than that of the other detector systems, with grids, at the same speed. CONCLUSION: No significant difference was found in the diagnostic performance at DSR, storage phosphor radiography, and film-based radiography for simulated interstitial lung disease at corresponding speeds; there was a reduction in the surface dose of about 50% with the 400-speed DSR system.

CT scanning of the paranasal sinuses: axial helical CT with reconstruction in the coronal direction versus coronal helical CT.

Paranasal sinuses of 52 patients with sinusitis, tumours or fibrous dysplasia were scanned. Axially acquired spiral data were obtained and reconstructed coronally. Four radiologists compared the two sets of images. They evaluated the diagnostic quality for visualization of the ostiomeatal unit, infundibulum, infraorbital canal, inflammatory disease, fine osseous lamellae and presence of amalgam or step artefacts. Two test phantoms were scanned for both techniques and lens dose was measured. Statistical significant differences in the diagnostic quality of the representation of the fine osseous structures in the paranasal sinuses, attributable to step artefacts were found in the coronally reconstructed images (p < 0.001). However, there was no amalgam and almost no motion artefacts in the reconstructed images. Interobserver correlation was r = 0.953 versus 0.956 for inflammatory disease, r = 0.816 versus 0.852 for artefacts, and r = 0.596 versus 0.547 for fine osseous lamellae in coronally acquired or axially acquired and reconstructed images, respectively. Lens dose was measured between 11.8 mGy and 13.8 mGy for axially acquired and reconstructed images. The advantage of axially acquired, coronally reconstructed images is the absence of artefacts attributable to amalgam and fewer motion artefacts. Axially acquired, coronally reconstructed images are inferior to coronal helical CT images, because of step artefacts, when it comes to evaluating the resolution of fine osseous structures. Nevertheless, reconstructed images are suitable as a investigatory procedure for patients with inflammatory disease who cannot maintain the prone position.

Subtle pulmonary abnormalities: detection on monitors with varying spatial resolutions and maximum luminance levels compared with detection on storage phosphor radiographic hard copies.

PURPOSE: The purpose of this receiver operating characteristic study was to compare diagnostic efficacy with images displayed on monitors of varying spatial resolutions and maximum luminance levels to that with storage phosphor radiographic hard copies. MATERIALS AND METHODS: Seven types of simulated lesions were superimposed onto an anthropomorphic chest phantom. Images were viewed by five radiologists on a 2,560 x 2,048 pixel monitor (maximum luminance, 75 foot-lamberts), on two 1,024 x 1,024 monitors with maximum luminance levels of 25 foot-lamberts and 75 foot-lamberts, respectively, as well as on hard copies. Monitor images were viewed both without and with systematic magnification. RESULTS: Overall visualization of the lesions was best on hard copies, but visualization on the 2,560 x 2,048 monitor was not found to be substantially different. Lines, reticular opacifications, and catheters were found to be particularly poorly visualized with the 1,024 x 1,024 monitor. These results could be statistically significantly improved only with a systematic magnification; however, this involved a considerable increase in viewing time. Observer performance was markedly inferior with the 1,024 x 1,024 monitor with the lower luminance. CONCLUSION: Diagnostic performance with a 1,024 x 1,024 monitor is statistically significantly inferior to that with hard copies. A statistically significant improvement can be achieved with a high-resolution 2,560 x 2,048 monitor with a maximum luminance of 75 foot-lamberts.

Comparison of three-dimensional virtual endoscopy with bronchoscopy in patients with oesophageal carcinoma infiltrating the tracheobronchial tree.

Virtual endoscopy (VE) is a technique for performing simulated bronchoscopy using helical CT data of the tracheobronchial tree. In order to evaluate a virtual three-dimensional (3D) endoluminal procedure for the tracheobronchial tree, comparison was made between bronchoscopy, axial CT images and minimal intensity projections (MIP). 21 patients were referred for helical CT because of oesophageal carcinoma shown by bronchoscopy to infiltrate into the trachea or bronchi. Axial CT images obtained on a helical scanner were transferred to a Sparc20 workstation. VE was compared with the axial CT images and the MIP concerning additional information on the location and degree of stenosis gained after 3D reconstruction of the inner surface of the tracheobronchial tree. The accuracy of this VE system was compared with bronchoscopy. Follow-up was performed in two patients to evaluate the tracheobronchial system after stent implantation. All stenoses were identified by VE with no statistically significant difference in detection of location or grading of the stenosis to real time bronchoscopy. Passage of subtotal stenosis was only possible with VE. VE is suitable for following up stent implantation. Submucosal lesions of the tracheobronchial tree could not be detected by VE. There was no statistically significant difference regarding the location of the stenoses between VE, axial CT slices, MIP and bronchoscopy. The VE showed only a statistically significant difference with regard to the degree of stenosis which was underrated on axial CT slices and MIPs. Pitfalls including mucus plugs and wall defects due to the wrong threshold value were a limitation of VE. VE is presently too time-consuming to use in every patient with an infiltrating tumour into the tracheobronchial tree. In conclusion, while VE cannot replace endoscopy of the tracheobronchial tree or the oesophagus, it is an accurate and non-invasive method for identifying endoluminal tumours, grading stenoses and visualizing the tracheobronchial tree beyond stenoses in a small number of patients who are not amenable to endoscopy.

[Ultrasound diagnosis of soft tissue changes in dialysis-associated amyloidosis]. / Sonographische Diagnose von Weichteilveränderungen bei der dialyseassoziierten Amyloidose.

AIM: To develop criteria for the detection of long term dialysis-associated soft tissue changes due to amyloid deposits in various joints. METHOD: Ultrasonographic examination of the shoulder (15 patients), hip (5 patients), knee (6 patients) and elbow (2 patients) using a 7.5 or 5 MHz scanner. A total of 28 joints were examined. RESULTS: Soft tissue changes in long term dialysis were found to be associated with an increased thickness of the supraspinatus tendon and/or biceps tendon as well as joint effusions with echogenic zones. Moreover, increased thickness of the joint capsule and echogenic proliferation of the synovia were observed. CONCLUSION: Ultrasound is an inexpensive and suitable method in the diagnosis and follow-up of soft tissue changes in patients on long term dialysis.

Electrophysiological and neurobiochemical evidence for the blockade of a potassium channel by dendrotoxin.

The effects of dendrotoxin (DTX), a toxic peptide from Dendroaspis angusticeps venom, were studied electrophysiologically on peripheral frog nerve fibres, and biochemically on large synaptosomes from rat brain. On nerve fibres, DTX reduced the amplitude and prolonged the duration of the action potential; even at 0.1 nmol/l DTX produced significant effects. Maximum block of potassium currents occurred at about 30 nmol/l. Turning on of the remaining current was slowed. Reversibility was incomplete. The reduction of potassium currents was between 31% and 85% at 85 nmol/l DTX (n = 8). The remainder appeared to be resistant to DTX. Sodium channels were not affected. On large synaptosomes DTX (above 1 nmol/l) produced a slight depolarization, indicated by an outward shift of the lipophilic cation tetraphenylphosphonium, and promoted the release of radioactivity after preloading with [3H] GABA. DTX had similar potency but lower efficacy in this respect than sea anemone toxin II (ATX II). In contrast to the effects of ATX II, those due to DTX were only partially inhibited by tetrodotoxin. The actions of 4-aminopyridine resembled those of DTX, but the latter was about 500 times more potent. The electrophysiological data provide direct evidence for blockade of a potassium channel by DTX. This action is sufficient to explain the biochemical observations, although additional effects on synaptosomes cannot be excluded.