[Ganglion block. Celiac plexus neurolysis]. / Ganglienblockade. Neurolyse des Plexus coeliacus.

BACKGROUND: Pain originating from the organs of the upper abdomen, especially in patients suffering from inoperable carcinoma of the pancreas or advanced inflammatory conditions, is difficult to treat in a significant number of patients. STANDARD RADIOLOGICAL PROCEDURES: Computed tomography (CT) guided neurolysis is the most commonly used technique for neurolysis of the celiac plexus. Ethanol is used to destroy the nociceptive fibers passing through the plexus and provides an effective means of diminishing pain arising from the upper abdomen. METHODS: Using either an anterior or posterior approach, a 22 G Chiba needle is advanced to the antecrural space and neurolysis is achieved by injecting a volume of 20-50 ml of ethanol together with a local anesthetic and contrast medium. PERFORMANCE: In up to 80% of patients suffering from tumors of the upper abdomen, CT-guided celiac plexus neurolysis diminishes pain or allows a reduction of analgesic medication; however, in some patients the effect may only be temporary necessitating a second intervention. In inflammatory conditions, celiac neurolysis is often less effective in reducing abdominal pain. PRACTICAL RECOMMENDATIONS: The CT-guided procedure for neurolysis of the celiac plexus is safe and effective in diminishing pain especially in patients suffering from tumors of the upper abdomen. The procedure can be repeated if the effect is only temporary.

[Dual-Energy CT in the follow-up after endovascular abdominal aortic aneurysm repair]. / Dual-Energy CT zur postoperativen Langzeitkontrolle nach endovaskulär therapierten abdominellen Aortenaneurysmen.

PURPOSE: This study investigates the dual-energy procedure for postoperative CT follow-up scans after endovascularly treated abdominal aortic aneurysms. The procedure is analyzed with respect to its sensitivity and specificity as well as the associated radiation exposure. MATERIALS AND METHODS: 51 examinations were carried out on 47 patients between February 2009 and March 2010. For each patient, a non-enhanced, an arterial and a venous scan were conducted, the latter two using the dual-energy technology. Virtual images for the non-enhanced phase were reconstructed from the data taken in the venous phase. Protocol A, the reference standard, consisted of non-enhanced images and images of the arterial and venous phase. In protocol B, standard non-enhanced images were replaced by the reconstructed virtual non-enhanced images. Protocol C consisted only of virtual non-enhanced and 80 kV images taken during the venous phase. All data was anonymized and evaluated by two independent radiologists. For protocol C, sensitivity, specificity, negative and positive predictive values were computed. The effective radiation dosage was determined for each scan. RESULTS: All endoleaks identified in protocol A were found using protocols B and C. For protocol C, the sensitivity and negative predictive value were 100 %, the specificity was 94.1 %, and the positive predictive value was 89.5 %. Compared to protocol A, protocol C reduces the radiation exposure by 62.45 %. CONCLUSION: A scan protocol consisting of virtual non-enhanced images as well as 80 kV images taken during the venous phase was found to be a reliable alternative method for diagnosing endoleaks, while reducing the radiation exposure by 62.45 %.

Reperfusion by combined thrombolysis and mechanical thrombectomy in acute stroke: effect of collateralization, mismatch, and time to and grade of recanalization on clinical and tissue outcome.

BACKGROUND AND PURPOSE: Our research focuses on interventional neuroradiology (stroke treatment including imaging methods) and general neuroimaging with an emphasis on functional MR imaging. Our aim was to determine the efficacy of revascularization (TIMI) of middle cerebral and/or carotid artery occlusion by means of mechanical recanalization techniques and to evaluate the impact of collateralization, mismatch in perfusion CT, time to revascularization, grade of revascularization on tissue, and clinical outcome in patients with acute ischemic stroke. MATERIALS AND METHODS: Thirty-one patients with MCA and/or ICA occlusion were included. Ischemic stroke was diagnosed by NECT, CTA, and volume PCT for grading collateralization and mismatch. Time to recanalization was measured from the onset of stroke to the time point of DSA-proved mechanical recanalization. Tissue outcome was calculated by segmentation of infarct size between pre- and postinterventional CT and percentage mismatch lost. Clinical outcome was determined by the mRS. RESULTS: Twenty-one of 31 patients (61.8%) presented with MCA and 10/31 patients (38.2%), with distal ICA occlusions. Sufficient recanalization (TIMI 2 and 3) was achieved in 23/31 (75%). Clinical evaluation revealed an mRS score of ≤2 in 25.5%. Age (r = 0.439, P = .038) and TIMI (r = 0.544, P = .002) showed the strongest correlation with clinical outcome. Time to recanalization, TIMI score, and mismatch were associated with a good tissue outcome in ANOVA. CONCLUSIONS: Favorable outcome after mechanical recanalization of acute MCA and ICA occlusion depends on time to and grade of recanalization, mismatch, and collateralization. These results indicate that multimodal stroke imaging is helpful to guide therapy decisions and to indicate patients amenable for mechanical recanalization.

Liver lesion segmentation in MSCT: effect of slice thickness on segmentation quality, measurement precision and interobserver variability.

PURPOSE: To evaluate the effect of slice thickness on semi-automated liver lesion segmentation. MATERIALS AND METHODS: In this retrospective study, liver MSCT scans from 60 patients were reconstructed at a slice thickness of 1.5 mm, 3 mm and 5 mm. 106 liver lesions (8 - 64 mm, mean size 25 ± 13 mm) were evaluated independently by two radiologists using semi-automated segmentation software (OncoTreat®). Lesions were classified as cystic, hypodense and hyperdense according to their contrast-to-noise ratio (CNR). The long axis diameter (LAD), short axis diameter (SAD) and volume were measured. The necessity for manual correction (NOC = relative difference between uncorrected and corrected volume) and the relative interobserver difference (RID) were determined. Precision was calculated in terms of relative measurement deviations (RMD) from the reference standard (mean of 1.5 mm data sets). Wilcoxon test, t-test and intraclass correlation coefficients (ICC) were employed for statistical analysis. All statistical analyses were intended to be exploratory. RESULTS: Regardless of the liver lesion subtype, the NOC was found to be significantly higher for 5 mm than for 3 mm (p = 0.035) and 1.5 mm (p = 0.0002). The RID was consistently low for metric and volumetric parameters with no difference in any of the slice thicknesses for all subtypes (ICC > 0.89). The RMD increased significantly for the LAD, SAD and volume at a slice thickness of 5 mm (p < 0.01), e. g. volume: 0.5 % at 1.5 mm, 5.5 % at 3.0 mm and 7.6 % at 5.0 mm. CONCLUSION: Since the deviations in measurements are significant, and manual corrections made during semi-automated assessment of the liver lesions are considerable, a slice thickness of 1.5 mm, and no more than 3.0 mm, should be used for reconstruction for inconsistently vascularized liver lesions.

[Imaging of coronary stents using multislice computed tomography]. / Darstellung von Koronarstents mit der Computertomographie.

Coronary artery stenting has become the most important form of coronary revascularization. With the introduction of drug-eluting stents (DES) the rate of restenosis has declined but due to the delayed formation of intimal tissue the incidence of late (>30 days after stent placement) and very late thrombosis of the stents is higher for DES. Visualization of the stent lumen is possible with multislice computed tomography (MSCT) but blooming artifacts hamper the delineation of the stent lumen. The severity of these artifacts and thus the width of the visible stent lumen depends on several factors, such as the thickness of the stent struts, the design of the stent and the underlying material itself. The most important factor influencing the extent of blooming artifacts is the convolution kernel selected for image reconstruction. Dedicated, edge-enhancing kernels offer superior lumen visualization compared to the soft or medium kernels used for coronary artery imaging. The trade-off using edge-enhancing kernels is an increase in image noise.Despite all efforts undertaken to enhance stent lumen visualization, stent imaging is still a challenge in MSCT. In the majority of stents currently used, sufficient lumen visualization is only possible in stents with a diameter larger than 3 mm. A position of the stent in the proximal segments of the coronary artery tree facilitates delineation of the stent lumen not only because of the relatively little motion but also because of the lesser extent of blooming artifacts obscuring the stent lumen if the stent is oriented perpendicular to the z-axis of the scanner.

[Dual-source computed tomography: effect on regional and global left ventricular function assessment compared to magnetic resonance imaging]. / Untersuchung der regionalen und globalen linksventrikulären Funktion mit der Dual-Source-Computertomografie im Vergleich zur Magnetresonanztomografie.

PURPOSE: To determine regional and global left ventricular (LV) functional parameters and to perform segmental wall thickness (SWT) and motion (WM) analysis of dual-source CT (DSCT) with optimized temporal resolution versus MRI. MATERIALS AND METHODS: 30 patients with known or suspected CAD, non-obstructive HCM, DCM, ARVCM, Fallot Tetralogy, cardiac sarcoidosis and cardiac metastasis underwent DSCT and MRI. The DSCT and MR images were evaluated: end-systolic (ESV), end-diastolic LV (EDV) volumes, stroke volume (SV), ejection fraction (EF), and myocardial mass (MM) as well as LV wall thickening and segmental WM applying the AHA model were obtained and statistically analyzed. RESULTS: The mean LV-EDV (r = 0.96) and ESV (r = 0.98) as well as LV-EF (r = 0.97), SV (r = 0.83), and MM (r = 0.95) correlated well. Bland Altman analysis revealed little systematic underestimation of LV-EF (-1.1 +/- 7.8 %), EDV (-0.3 +/- 18.2 ml), SV (-1.3 +/- 16.7 ml) and little overestimation of ESV (1.1 +/- 7.8 ml) and MM (12.8 +/- 14.4 g) determined by DSCT. Systolic reconstruction time points correlated well (DSCT 32.2 +/- 6.7 vs. MRI 35.6 +/- 4.4 % RR-interval). The LV wall thickness obtained by DSCT and MRI showed close correlation in all segments (Ø diff 0.42 +/- 1 mm). In 413 segments (89 %) WM abnormalities were equally rated, whereas DSCT tended to underestimate the degree of wall motion impairment. CONCLUSION: DSCT with optimized temporal resolution enables regional and global LV function analysis as well as segmental WM analysis in good correlation with MRI. However, the degree of WM impairment is slightly underestimated by DSCT.

Optimization of scan delay for routine abdominal 64-slice CT with body weight-adapted application of contrast material.

PURPOSE: Determination of an adequate scan delay for routine abdominal 64-slice CT examinations with body weight-adapted contrast application. MATERIALS AND METHODS: 57 patients underwent abdominal CT with a 64-slice scanner. The contrast material was adapted to patient body weight. All patients were randomized into five groups with varying scan delay and scan direction (group 1: delay 65 sec; group 2: 75 sec; group 3: 85 sec, craniocaudal; group 4: 85 sec, caudocranial; group 5: 95 sec). Two blinded radiologists evaluated the image quality. CT values (HU) were obtained in different segments of the aorta, inferior vena cava, iliac veins, portal vein, hepatic veins and liver, spleen and pancreas. Statistical analysis was performed using the independent sample t-test and ANOVA test. RESULTS: The diagnostic acceptability of protocols 3 and 4 were rated equally good and significantly/substantially superior to protocol 1 (p = 0.004/0.008) and protocol 5, respectively. Contrast enhancement in the aorta and portal vein peaked at 65 sec. Contrast enhancement in the hepatic and iliac veins peaked at 85 sec independently of the scan direction but was substantially lower at 75 sec. Liver parenchyma enhancement was lowest at 95 sec. CONCLUSION: This data suggests an optimal scan delay for routine abdominal 64-slice CT of 85 sec regardless of scan direction.

Automatic selection of optimal systolic and diastolic reconstruction windows for dual-source CT coronary angiography.

The aim of this study was to assess the performance of a motion-map algorithm that automatically determines optimal reconstruction windows for dual-source coronary CT angiography. In datasets from 50 consecutive patients, optimal systolic and diastolic reconstruction windows were determined using the motion-map algorithm. For manual determination of the optimal reconstruction window, datasets were reconstructed in 5% steps throughout the RR interval. Motion artifacts were rated for each major coronary vessel using a five-point scale. Mean motion scores using the motion-map algorithm were 2.4 +/- 0.8 for systolic reconstructions and 1.9 +/- 0.8 for diastolic reconstructions. Using the manual approach, overall motion scores were significantly better (1.9 +/- 0.5 and 1.7 +/- 0.6, p < 0.05), but diagnostic image quality was reached in >90% of cases using either approach. Using the automated approach, there was a negative correlation between heart rate and motion scores for systolic reconstructions (rho = -0.26, p < 0.05) and a positive correlation for diastolic reconstructions (rho = 0.46, p < 0.01). For the manual approach, no significant correlation was found for systolic reconstructions (rho = -0.1, p = 0.52), while there was a positive correlation for diastolic reconstructions (rho = 0.48, p < 0.01). Thus, the motion-map algorithm is a useful tool to save time in finding an appropriate reconstruction window in patients with heart rates <70 bpm (diastolic reconstruction) and >80 bpm (systolic reconstruction).

[Accuracy of liver lesion assessment using automated measurement and segmentation software in biphasic multislice CT (MSCT)]. / Einfluss des vaskularisationsgrades auf die automatische segmentierung und messung von lebertumoren nach RECIST in einer biphasischen multi-slice-CT (MSCT).

PURPOSE: To assess the accuracy of liver lesion measurement using automated measurement and segmentation software depending on the vascularization level. MATERIALS AND METHODS: Arterial and portal venous phase multislice CT (MSCT) was performed for 58 patients. 94 liver lesions were evaluated and classified according to vascularity (hypervascular: 13 hepatocellular carcinomas, 20 hemangiomas; hypovascular: 31 metastases, 3 lymphomas, 4 abscesses; liquid: 23 cysts). The RECIST diameter and volume were obtained using automated measurement and segmentation software and compared to corresponding measurements derived visually by two experienced radiologists as a reference standard. Statistical analysis was performed using the Wilcoxon test and concordance correlation coefficients. RESULTS: Automated measurements revealed no significant difference between the arterial and portal venous phase in hypovascular (mean RECIST diameter: 31.4 vs. 30.2 mm; p = 0.65; kappa = 0.875) and liquid lesions (20.4 vs. 20.1 mm; p = 0.1; kappa = 0.996). The RECIST diameter and volume of hypervascular lesions were significantly underestimated in the portal venous phase as compared to the arterial phase (30.3 vs. 26.9 mm, p = 0.007, kappa = 0.834; 10.7 vs. 7.9 ml, p = 0.0045, kappa = 0.752). Automated measurements for hypovascular and liquid lesions in the arterial and portal venous phase were concordant to the reference standard. Hypervascular lesion measurements were in line with the reference standard for the arterial phase (30.3 vs. 32.2 mm, p = 0.66, kappa = 0.754), but revealed a significant difference for the portal venous phase (26.9 vs. 32.1 mm; p = 0.041; kappa = 0.606). CONCLUSION: Automated measurement and segmentation software provides accurate and reliable determination of the RECIST diameter and volume in hypovascular and liquid liver lesions. Hypervascular lesions are prone to be underestimated with regard to size in the portal venous phase and therefore should preferentially be segmented in the arterial phase.

[Endovascular therapy of infrarenal aortic aneurysms: preinterventional imaging and follow-up]. / Endovaskuläre Therapie des Bauchaortenaneurysmas: Prä- und postinterventionelle bildgebende Diagnostik.

Imaging plays an important role in the selection of patients with infrarenal aortic aneurysms suitable for interventional therapy and preinterventional workup. It is also an important tool for follow-up after stent-graft placement. Cross-sectional imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI) allow the delineation of the vessel lumen and side branches. Modern postprocessing techniques permit precise measurement of aneurysm properties such as the length and diameter of the proximal and distal neck and the length and diameter of the aneurysm. Evaluation of the access vessel is also possible. During follow-up after stent-graft placement, it is important to detect possible endoleaks and further growth of the aneurysm sac. Furthermore fractures of the stent struts, migration of the stent, and in-stent thrombosis must to be detected. This review provides an overview of the pros and cons of the different imaging modalities in pre- and postinterventional studies. In addition the most important criteria for the exclusion of infrarenal aortic aneurysms and for patient follow-up are presented.

Virtual intra-arterial angioscopy (VIA) of the carotid artery based on helical CT data.

The purpose of this study was to visualize both the vessel wall and atherosclerotic plaques in virtual intra-arterial angioscopy (VIA) based on helical CT data sets. To achieve this in vitro, the optimal reconstruction threshold of the vessel wall was determined to be 56.4% of the maximum enhancement. Using this threshold, 20 patients suffering from symptomatic carotid disease were examined in a helical CT scanner. The degree of stenosis was defined using the North American Symptomatic Endarterectomy Trial (NASCET) criteria and compared with results from digital substraction angiography (DSA). Grading of stenoses was only possible by adding the separately computed plaque geometry to the geometry of the vessel wall in a second step. Correlation between VIA and DSA in low grade, medium grade and high grade stenosis was 88%, 93% and 71%, respectively. Complete occlusions were diagnosed correctly in all patients. Sensitivity and specificity for the correct diagnosis of high grade stenosis was 93.7% and 91.3%, respectively. A realistic depiction of intraluminal structures in carotid arteries can only be generated by displaying both the vessel wall and plaque structures simultaneously.

Intraoperative, perioperative and late complications with endovascular therapy of aortic aneurysm.

PURPOSE: To describe the incidence and management of the intraoperative, perioperative and late complications of endovascular aortic aneurysm repair. METHODS: Endovascular aneurysm repair was attempted in 130 patients between October, 1995 and January, 2000. Follow-up including computed tomography (CT) was performed in the immediate postoperative period and then at 3, 6, 9 and 12 months and biannually thereafter. The median follow-up period was 20 months. RESULTS: Intra- and perioperative problems occurred in 26 patients (20%). Conversion to open surgery was required in five cases (4%). The primary technical success rate was 86%. Three patients (2%) died within the first 30 postoperative days. Late problems occurred in 28 patients (26%). These included: endoleaks (type I: 5%; type II: 10%; type III: 1%) and limb occlusion (3%). The cumulative rate of freedom from secondary intervention was in the first 65 patients treated: 86% and 65% after 1 and 3 years, respectively, and in the last 65 patients: 90% at 1 year. CONCLUSIONS: Endovascular aneurysm repair is associated with a higher complication rate than open surgery.

Endovascular grafting of traumatic aortic aneurysms in contaminated fields.

PURPOSE: To evaluate the potential of endovascular stent-grafts to treat traumatic aortic lesions in contaminated areas. METHODS: Four patients (3 women; ages 26-78 years) underwent stent-grafting to repair an aortic rupture sustained in a motorcycle accident, aortic lacerations secondary to surgical treatment of spondylitis in 2 patients, and an aortobronchial fistula following surgical thoracic aortic repair 10 years earlier. Stent-grafts (2 Corvita, 1 Talent, and 1 Vanguard) were placed endoluminally into the infected areas via a transfemoral approach. Follow-up included erythrocyte sedimentation rate, white blood count, C-reactive protein, blood cultures, and computed tomography (CT). RESULTS: The stent-grafts were successfully placed in all cases and excluded the aortic lesion. Under supportive antibiotic therapy, inflammation parameters returned to normal. CT imaging showed no evidence of paraprosthetic infection, nor were there any other complications over a follow-up that ranged from 3 to 34 months. CONCLUSIONS: Endovascular therapy may be an alternative in the acute management of aortic ruptures in the setting of infection. Long-term results are required for definitive evaluation of the method.

Geometric changes in aortic endografts over a 2-year observation period.

PURPOSE: To report geometric changes in bifurcated aortic endografts observed over a 2-year follow-up period. METHODS: Twenty-two patients (21 men; mean age 68 years, range 57-83) with abdominal aortic aneurysms were treated with an endovascular stent-graft. Follow-up examinations included spiral computed tomographic scanning postoperatively and at 3, 6, 9, 12, 18, and 24 months after treatment. Geometric changes were measured using 3-dimensional reconstructed images in anteroposterior (AP) and lateral projections. Locations for the measurements were the proximal neck, the midportion of the endograft, and the graft limbs at the origin of the iliac arteries. RESULTS: Lateral changes predominated, demonstrating maximum angles on the side of the inserted left limb. For the proximal neck, the stent angle changed by a mean -0.71 degrees in the AP and 4.0 degrees in the lateral projection. At the midgraft, changes were -0.56 degrees for AP and 12.5 degrees for lateral. The right limb showed an angle of 6.43 degrees in AP and -0.43 degrees in lateral, whereas the left limb angles changed 1.38 degrees in AP and 11.71 degrees in the lateral plane after 2 years. There was no statistically significance difference in these changes from baseline. CONCLUSIONS: Aortic endografts are exposed to a significant amount of movement after insertion, but the resultant changes are very inhomogeneous, unpredictable, and ongoing even after 2 years. The most vulnerable location seems to be the attachment zone of the modular graft limb. These geometric changes might be one cause for late complications, including leaks and limb dislocations.

[High-resolution virtual laryngoscopy based on spiral CT data]. / Hochauflösende virtuelle Laryngoskopie aus Spiral-CT-Datensätzen.

This pilot study investigated the feasibility and clinical value of high-resolution virtual real-time laryngoscopy based on helical CT data sets. Nine patients with laryngeal pathology (three with tumors of the vocal cords, two laryngeal carcinomas, one with invasion of the larynx by thyroid carcinoma and six subglottic stenoses) underwent examination by helical CT at a collimation of 1 mm. Following acquisition, the images were processed at a workstation with standard visualization software, such that virtual endoscopy (VE) in real time was possible. The images were then compared with the findings of conventional endoscopy. Because of swallowing artifacts, reconstruction failed in 2 of 12 patients. None of the carcinomas of the vocal cords was recognized at VE or in the cross-sectional CT images. VE provided the correct diagnosis in 8 of 12 cases (laryngeal tumors, subglottic stenoses). Virtual laryngoscopy is capable of simulating the visual findings of endoscopy in cases of laryngeal tumors and subglottic stenoses. Small tumors of the vocal cords are not adequately visualized. The major problem affecting results is motion artifacts resulting from involuntary swallowing.