Zsolt Szucs-Farkas

Inselspital, Universitätsspital Bern, Berna, Bern, Switzerland

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Publications (45)160.15 Total impact

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    ABSTRACT: To find a threshold body weight (BW) below 100 kg above which computed tomography pulmonary angiography (CTPA) using reduced radiation and a reduced contrast material (CM) dose provides significantly impaired quality and diagnostic confidence compared with standard-dose CTPA.
    European radiology. 05/2014;
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    ABSTRACT: OBJECTIVE. The purpose of this study was to assess the impact of a noise reduction technique on image quality, radiation dose, and low-contrast detectability in abdominal CT for obese patients. MATERIALS AND METHODS. A liver phantom with 12 different tumors was designed, and fat rings were added to mimic intermediately sized and large patients. The intermediate and large phantoms were scanned with our standard abdominal CT protocol (image noise level of 15 HU and filtered back projection [FBP]). The large phantom was scanned with five different noise levels (10, 12.5, 15, 17.5, and 20 HU). All datasets for the large phantom were reconstructed with FBP and the noise reduction technique. The image noise and the contrast-to-noise ratio (CNR) were assessed. Tumor detection was independently performed by three radiologists in a blinded fashion. RESULTS. The application of the noise reduction method to the large phantom decreased the measured image noise (range, -14.5% to -37.0%) and increased the CNR (range, 26.7-70.6%) compared with FBP at the same noise level (p < 0.001). However, noise reduction was unable to improve the sensitivity for tumor detection in the large phantom compared with FBP at the same noise level (p > 0.05). Applying a noise level of 15 HU, the overall sensitivity for tumor detection in the intermediate and large phantoms with FBP measured 75.5% and 87.7% and the radiation doses measured 42.0 and 23.7 mGy, respectively. CONCLUSION. Although noise reduction significantly improved the quantitative image quality in simulated large patients undergoing abdominal CT compared with FBP, no improvement was observed for low-contrast detectability.
    American Journal of Roentgenology 02/2014; 202(2):W146-52. · 2.90 Impact Factor
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    ABSTRACT: The objective of the study was to test the diagnostic performance of low-dose computed tomography pulmonary angiography (CTPA) at peak tube voltage of 80 kVp with both reduced radiation and reduced contrast material (CM) dose. In this single-center, single-blinded prospective randomized trial, 501 patients with body weights of less than 100 kg with suspected acute pulmonary embolism (PE) were assigned to normal-dose CTPA (100-kVp tube energy and 100-mL CM, 255 patients) and low-dose CTPA (80-kVp tube energy and 75-mL CM, 246 patients). Primary end points were evidence of PE in CTPA and accuracy of CTPA on a composite reference standard. Results were compared by calculating the odds ratio with the 95% confidence interval. The reference diagnosis was equivocal in 20 of the 501 patients. Diagnosis of CTPA was correct in 240 patients and incorrect in 5 in the normal-dose group. Computed tomography pulmonary angiography was correct in 230 patients and incorrect in 6 in the low-dose group (odds ratio, 1.25; 95% confidence interval, 0.38-4.16; P = 0.77). Sensitivity was 96.9% and 100% and specificity was 98.1% and 97.1% in the normal-dose and low-dose groups, respectively. No PE or PE-related death occurred during the 90-day follow-up. The size-specific dose estimates were 30% lower at 80 kVp (4.8 ± [1.0] mGy) compared with that at 100 kVp (6.8 ± 1.2 mGy; P < 0.001). The accuracy of low-dose CTPA at 80 kVp with a 30% reduced radiation dose and a 25% lower CM volume is not significantly different from that of normal-dose CTPA at 100 kVp in detecting acute PE in patients weighing less than 100 kg.
    Investigative radiology 01/2014; · 4.85 Impact Factor
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    ABSTRACT: Background The accuracy of CT pulmonary angiography (CTPA) in detecting or excluding pulmonary embolism has not yet been assessed in patients with high body weight (BW). Methods This retrospective study involved CTPAs of 114 patients weighing 75–99 kg and those of 123 consecutive patients weighing 100–150 kg. Three independent blinded radiologists analyzed all examinations in randomized order. Readers' data on pulmonary emboli were compared with a composite reference standard, comprising clinical probability, reference CTPA result, additional imaging when performed and 90-day follow-up. Results in both BW groups and in two body mass index (BMI) groups (BMI < 30 kg/m2 and BMI ≥ 30 kg/m2, i.e., non-obese and obese patients) were compared. Results The prevalence of pulmonary embolism was not significantly different in the BW groups (P = 1.0). The reference CTPA result was positive in 23 of 114 patients in the 75–99 kg group and in 25 of 123 patients in the ≥ 100 kg group, respectively (odds ratio, 0.991; 95% confidence interval, 0.501 to 1.957; P = 1.0). No pulmonary embolism-related death or venous thromboembolism occurred during follow-up. The mean accuracy of three readers was 91.5% in the 75–99 kg group and 89.9% in the ≥ 100 kg group (odds ratio, 1.207; 95% confidence interval, 0.451 to 3.255; P = 0.495), and 89.9% in non-obese patients and 91.2% in obese patients (odds ratio, 0.853; 95% confidence interval, 0.317 to 2.319; P = 0.816). Conclusion The diagnostic accuracy of CTPA in patients weighing 75–99 kg or 100–150 kg proved not to be significantly different.
    European Journal of Internal Medicine 01/2014; · 2.05 Impact Factor
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    ABSTRACT: To determine the value of combined automated attenuation-based tube-potential selection and iterative reconstructions (IRs) for optimising computed tomography (CT) imaging of hypodense liver lesions. A liver phantom containing hypodense lesions was imaged by CT with and without automated attenuation-based tube-potential selection (80, 100 and 120 kVp). Acquisitions were reconstructed with filtered back projection (FBP) and sinogram-affirmed IR. Image noise and contrast-to-noise ratio (CNR) were measured. Two readers marked lesion localisation and rated confidence, sharpness, noise and image quality on a five-point scale (1 = worst, 5 = best). Image noise was lower (31-52 %) and CNR higher (43-102 %) on IR than on FBP images at all tube voltages. On 100-kVp and 80-kVp IR images, confidence and sharpness were higher than on 120-kVp FBP images. Scores for image quality score and noise as well as sensitivity for 100-kVp IR were similar or higher than for 120-kVp FBP and lower for 80-kVp IR. Radiation dose was reduced by 26 % at 100 kVp and 56 % at 80 kVp. Compared with 120-kVp FBP images, the combination of automated attenuation-based tube-potential selection at 100 kVp and IR provides higher image quality and improved sensitivity for detecting hypodense liver lesions in vitro at a dose reduced by 26 %. • Combining automated tube voltage selection/iterative CT reconstruction improves image quality. • Attenuation values remain stable on IR compared with FBP images. • Lesion detection was highest on 100-kVp IR images.
    European Radiology 10/2013; · 4.34 Impact Factor
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    ABSTRACT: To find the best pairing of first and second reader at highest sensitivity for detecting lung nodules with CT at various dose levels. An anthropomorphic lung phantom and artificial lung nodules were used to simulate screening CT-examination at standard dose (100mAs, 120kVp) and 8 different low dose levels, using 120, 100 and 80kVp combined with 100, 50 and 25mAs. At each dose level 40 phantoms were randomly filled with 75 solid and 25 ground glass nodules (5-12mm). Two radiologists and 3 different computer aided detection softwares (CAD) were paired to find the highest sensitivity. Sensitivities at standard dose were 92%, 90%, 84%, 79% and 73% for reader 1, 2, CAD1, CAD2, CAD3, respectively. Combined sensitivity for human readers 1 and 2 improved to 97%, (p1=0.063, p2=0.016). Highest sensitivities - between 97% and 99.0% - were achieved by combining any radiologist with any CAD at any dose level. Combining any two CADs, sensitivities between 85% and 88% were significantly lower than for radiologists combined with CAD (p<0.03). Combination of a human observer with any of the tested CAD systems provide optimal sensitivity for lung nodule detection even at reduced dose at 25mAs/80kVp.
    European journal of radiology 09/2013; · 2.65 Impact Factor
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    ABSTRACT: Purpose:To compare the low-contrast detectability and image quality of computed tomography (CT) at different radiation dose levels reconstructed with iterative reconstruction (IR) and filtered back projection (FBP).Materials and Methods:A custom liver phantom with 12 simulated hypoattenuating tumors (diameters of 5, 10, 15, and 20 mm; tumor-to-liver contrast values of -10, -20, and -40 HU) was designed. The phantom was scanned with a standard abdominal CT protocol with a volume CT dose index of 21.6 mGy (equivalent 100% dose) and four low-dose protocols (20%, 40%, 60%, and 80% of the standard protocol dose). CT data sets were reconstructed with IR and FBP. Image noise was measured, and the tumors' contrast-to-noise ratios (CNRs) were calculated. Tumor detection was independently assessed by three radiologists who were blinded to the CT technique used. A total of 840 simulated tumors were presented to the radiologists. Statistical analyses included analysis of variance.Results:IR yielded an image noise reduction of 43.9%-63.9% and a CNR increase of 74.1%-180% compared with FBP at the same dose level (P < .001). The overall sensitivity for tumor detection was 64.7%-85.3% for IR and 66.3%-85.7% for FBP at the 20%-100% doses, respectively. There was no significant difference in the sensitivity for tumor detection between IR and FBP at the same dose level (P = .99). The sensitivity of the protocol at the 20% dose with FBP and IR was significantly lower than that of the protocol at the 100% dose with FBP and IR (P = .019).Conclusion:As the radiation dose at CT decreases, the IR algorithm does not preserve the low-contrast detectability.© RSNA, 2013Supplemental material:http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13122349/-/DC1.
    Radiology 06/2013; · 6.34 Impact Factor
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    ABSTRACT: BACKGROUND: The objective of the study was to correlate MR-detectable motility alterations of the terminal ileum with biopsy-documented active and chronic changes in Crohn's disease. METHODS: This IRB approved retrospective analysis of 43 patients included magnetic resonance enterography (MRE) and terminal ileum biopsies (<2 weeks apart). Motility was measured at the terminal ileum using coronal 2D trueFISP pulse sequences (1.5T MRI,TR 83.8,TE1.89) and dedicated motility assessment software. Motility grading (hypermotility, normal, hypomotility, complete arrest) was agreed by two experienced readers. Motility was compared and correlated with histopathology using two-tailed Kruskal-Wallis test and paired Spearman Rank-Order Correlation tests. KEY RESULTS: Motility abnormalities were present in 27/43 patients: nine hypomotility and 18 complete arrest. Active disease was diagnosed on 15 biopsies: eight moderate and seven severe inflammatory activity. Chronic changes were diagnosed on 17 biopsies: 13 moderate and four severe cases. In four patients with normal motility alterations on histopathology were diagnosed. Histopathology correlated with presence (P = 0.0056 for hypomotility and P = 0.0119 for complete arrest) and grade (P < 0.0001; P = 0.0004) of motility alterations. A significant difference in the motility was observed in patients with active or chronic CD compared with patients without disease (P < 0.001; P = 0.0024). CONCLUSIONS & INFERENCES: MR-detectable motility changes of the terminal ileum correlate with histopathological findings both in active and chronic CD. Motility changes may indicate the presence pathology, but do not allow differentiation of active and chronic disease.
    Neurogastroenterology and Motility 06/2013; · 2.94 Impact Factor
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    ABSTRACT: OBJECTIVE. The objective of our study was to compare the effect of dual-energy subtraction and bone suppression software alone and in combination with computer-aided detection (CAD) on the performance of human observers in lung nodule detection. MATERIALS AND METHODS. One hundred one patients with from one to five lung nodules measuring 5-29 mm and 42 subjects with no nodules were retrospectively selected and randomized. Three independent radiologists marked suspicious-appearing lesions on the original chest radiographs, dual-energy subtraction images, and bone-suppressed images before and after postprocessing with CAD. Marks of the observers and CAD marks were compared with CT as the reference standard. Data were analyzed using nonparametric tests and the jackknife alternative free-response receiver operating characteristic (JAFROC) method. RESULTS. Using dual-energy subtraction alone (p = 0.0198) or CAD alone (p = 0.0095) improved the detection rate compared with using the original conventional chest radiograph. The combination of bone suppression and CAD provided the highest sensitivity (51.6%) and the original nonenhanced conventional chest radiograph alone provided the lowest (46.9%; p = 0.0049). Dual-energy subtraction and bone suppression provided the same false-positive (p = 0.2702) and true-positive (p = 0.8451) rates. Up to 22.9% of lesions were found only by the CAD program and were missed by the readers. JAFROC showed no difference in the performance between modalities (p = 0.2742-0.5442). CONCLUSION. Dual-energy subtraction and the electronic bone suppression program used in this study provided similar detection rates for pulmonary nodules. Additionally, CAD alone or combined with bone suppression can significantly improve the sensitivity of human observers for pulmonary nodule detection.
    American Journal of Roentgenology 05/2013; 200(5):1006-13. · 2.90 Impact Factor
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    ABSTRACT: The aim of this phantom study was to minimize the radiation dose by finding the best combination of low tube current and low voltage that would result in accurate volume measurements when compared to standard CT imaging without significantly decreasing the sensitivity of detecting lung nodules both with and without the assistance of CAD. An anthropomorphic chest phantom containing artificial solid and ground glass nodules (GGNs, 5-12 mm) was examined with a 64-row multi-detector CT scanner with three tube currents of 100, 50 and 25 mAs in combination with three tube voltages of 120, 100 and 80 kVp. This resulted in eight different protocols that were then compared to standard CT sensitivity (100 mAs/120 kVp). For each protocol, at least 127 different nodules were scanned in 21-25 phantoms. The nodules were analyzed in two separate sessions by three independent, blinded radiologists and computer-aided detection (CAD) software. The mean sensitivity of the radiologists for identifying solid lung nodules on a standard CT was 89.7%±4.9%. The sensitivity was not significantly impaired when the tube and current voltage were lowered at the same time, except at the lowest exposure level of 25 mAs/80 kVp [80.6%±4.3% (p = 0.031)]. Compared to the standard CT, the sensitivity for detecting GGNs was significantly lower at all dose levels when the voltage was 80 kVp; this result was independent of the tube current. The CAD significantly increased the radiologists' sensitivity for detecting solid nodules at all dose levels (5-11%). No significant volume measurement errors (VMEs) were documented for the radiologists or the CAD software at any dose level. Our results suggest a CT protocol with 25 mAs and 100 kVp is optimal for detecting solid and ground glass nodules in lung cancer screening. The use of CAD software is highly recommended at all dose levels.
    PLoS ONE 01/2013; 8(12):e82919. · 3.73 Impact Factor
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    ABSTRACT: AIM: To assess the effect of an automatic tube voltage selection technique on image quality and radiation dose in abdominal computed tomography (CT) angiography of various body sizes. MATERIALS AND METHODS: An abdominal aortic phantom was filled with iodinated contrast medium and placed into three different cylindrical water containers, which simulated a small, intermediate-sized, and large patient. The phantom was scanned with a standard 120 kVp abdominal CT angiography protocol and with an optimized tube voltage protocol that was modulated by an automatic tube voltage technique. The attenuation of the aorta, background, and image noise was measured, and the contrast-to-noise ratio (CNR) was calculated. Three independent readers assessed the overall image quality. RESULTS: The automatic tube voltage technique selected 70 kVp as the optimal tube voltage for the small phantom, 80 kVp for the intermediate phantom, and 100 kVp for the large phantom. Compared to the standard 120 kVp protocol, the automatic tube voltage selection yielded significantly increased CNR values in the small phantom (15.8 versus 19.4, p < 0.001), intermediate phantom (8.4 versus 8.7, p < 0.05), and large phantom (4.3 versus 4.6, p < 0.01). The automatic tube voltage selection resulted in a 55%, 49%, and 39% reduction in the volume CT dose index (CTDI(vol)) in the small, intermediate, and large phantoms, respectively. The subjective overall image quality of the three phantom sizes at different tube voltages ranged between poor and good. CONCLUSION: Compared to a standard 120 kVp abdominal CT angiography protocol, the automatic tube voltage selection substantially reduced the radiation dose without compromising image quality in various simulated patient sizes.
    Clinical radiology 12/2012; · 1.65 Impact Factor
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    ABSTRACT: The aim of this prospective clinical study was to evaluate the location of paravertebral catheters that were placed using the classical landmark puncture technique and to correlate the distribution of contrast dye injected through the catheters with the extent of somatic block. Paravertebral catheter placement was attempted in 31 patients after video-assisted thoracic surgery. In one patient, an ultrasound-guided approach was chosen after failed catheter placement using the landmark method. A fluoroscopic examination in two planes using contrast dye was followed by injection of local anaesthetic and subsequent clinical testing of the extent of the anaesthetised area. In nine patients (29%), spread of contrast dye was not seen within the paravertebral space as intended. Misplaced catheters were in the epidural space (three patients), in the erector spinae musculature (five patients), and in the pleural space (one patient). There was also a discrepancy between the radiological findings and the observed distribution of loss of sensation. We have demonstrated an unacceptably high misplacement rate of paravertebral catheters using the landmark method. Additional research is required to compare the efficacy and safety of continuous paravertebral block using ultrasound-guided techniques or surgical inserted catheters.
    Anaesthesia 12/2012; 67(12):1321-6. · 3.49 Impact Factor
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    ABSTRACT: To identify reasons for ordering computed tomography pulmonary angiography (CTPA), to identify the frequency of reasons for CTPA reflecting defensive behavior and evidence-based behavior, and to identify the impact of defensive medicine and of training about diagnosing pulmonary embolism (PE) on positive results of CTPA. Physicians in the emergency department of a tertiary care hospital completed a questionnaire before CTPA after being trained about diagnosing PE and completing questionnaires. Nine hundred patients received a CTPA during 3 years. For 328 CTPAs performed during the 1-year study period, 140 (43 %) questionnaires were completed. The most frequent reasons for ordering a CTPA were to confirm/rule out PE (93 %), elevated D-dimers (66 %), fear of missing PE (55 %), and Wells/simplified revised Geneva score (53 %). A positive answer for "fear of missing PE" was inversely associated with positive CTPA (OR 0.36, 95 % CI 0.14-0.92, p = 0.033), and "Wells/simplified revised Geneva score" was associated with positive CTPA (OR 3.28, 95 % CI 1.24-8.68, p = 0.017). The proportion of positive CTPA was higher if a questionnaire was completed, compared to the 2-year comparison period (26.4 vs. 14.5 %, OR 2.12, 95 % CI 1.36-3.29, p < 0.001). The proportion of positive CTPA was non-significantly higher during the study period than during the comparison period (19.2 vs. 14.5 %, OR 1.40, 95 % CI 0.98-2.0, p = 0.067). Reasons for CTPA reflecting defensive behavior-such as "fear of missing PE"-were frequent, and were associated with a decreased odds of positive CTPA. Defensive behavior might be modifiable by training in using guidelines.
    European Journal of Intensive Care Medicine 05/2012; 38(8):1345-51. · 5.17 Impact Factor
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    ABSTRACT: To assess the effect of tumor size and tumor-to-liver contrast of simulated hypovascular liver tumors on the diagnostic accuracy of hepatic computed tomography (CT). This retrospective study was approved by the institutional review board, and informed consent was waived. A total of 153 simulated hypovascular liver tumors were embedded in 70 hepatic CT data sets that were acquired during the portal venous phase. The simulated tumors had 3 different diameters (6, 10, and 14 mm) and 3 different tumor-to-liver contrast values (20, 35, and 50 HU). There were also 30 hepatic CT data sets without liver tumors. Three radiologists independently performed tumor detection on the randomized 100 hepatic CT data sets. The lowest sensitivity was obtained for the 6-mm tumors with a tumor-to-liver contrast of 20 HU (4.1%), and the highest sensitivity was obtained for the 10- and 14-mm tumors with a tumor-to-liver contrast of 50 HU (100%). Increasing the contrast from 20 to 35 to 50 HU in the 6-mm tumors yielded a significant increase in sensitivity (4.1%, 48.8%, and 92.4%, respectively; P < 0.0001). The sensitivity for the 10- and 14-mm tumors also increased significantly as the tumor-to-liver contrast value increased from 20 to 35 HU (P < 0.01). However, no significant increase in sensitivity was seen for the 10- and 14-mm tumors as the tumor-to-liver contrast values increased from 35 to 50 HU (P = 0.733 and P = 1.0, respectively). Increasing the tumor-to-liver contrast from 20 to 35 HU results in a significant increase in the detection of hypovascular liver tumors ranging from 6 to 14 mm in diameter. Optimization of the tumor-to-liver contrast is necessary for improved detection of hypovascular liver tumors.
    Investigative radiology 03/2012; 47(3):197-201. · 4.85 Impact Factor
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    ABSTRACT: To determine the prevalence and importance of extracardiac findings (ECF) in patients undergoing clinical CMR and to test the hypothesis that the original CMR reading focusing on the heart may underestimate extracardiac abnormalities. 401 consecutive patients (mean age 53 years) underwent CMR at 1.5 T. Main indications were ischaemic heart disease (n = 183) and cardiomyopathy (n = 164). All CMR sequences, including scout images, were reviewed with specific attention to ECF in a second reading by the same radiologist who performed the first clinical reading. Potentially significant findings were defined as abnormalities requiring additional clinical or radiological follow-up. 250 incidental ECF were detected, of which 84 (34%) had potentially significant ECF including bronchial carcinoma (n = 1), lung consolidation (n = 7) and abdominal abnormalities. In 166 CMR studies (41%) non-significant ECF were detected. The number of ECF identified at second versus first reading was higher for significant (84 vs. 47) and non-significant (166 vs. 36) findings (P < 0.00001). About one fifth of patients undergoing CMR were found to have potentially significant ECF requiring additional work-up. The second dedicated reading detected significantly more ECF compared with the first clinical reading emphasising the importance of active search for extracardiac abnormalities when evaluating CMR studies. • Many patients undergoing cardiac MR have significant extracardiac findings (ECF) • These impact on management and require additional work-up. • Wide review of scout and cine sequences will detect most ECFs. • Education of radiologists is important to identify ECFs on CMR studies.
    European Radiology 01/2012; 22(6):1295-302. · 4.34 Impact Factor
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    ABSTRACT: Background and aims: Continuous paravertebral block is often described as producing a variable degree of block with a limited extent over a few segments only. This variability could be explained by a discrepancy between the needle tip location and the final resting position of the catheter tip once introduced through the needle. This possibility has recently been studied in an imaging study in fixed human cadavers. The aim of this prospective clinical trial was to evaluate the location of paravertebral catheters placed using the classical landmark puncture technique and to correlate the distribution of contrast dye injected through the catheters with the extent of somatic block. Methods: Paravertebral catheters were placed in 30 patients after videoassisted thoracic surgery. A fluoroscopic examination in two planes using contrast dye was followed by injection of local anaesthetics and subsequent clinical testing of the extent of the anaesthetized area. Results: In 30% of the cases, contrast dye spread was not seen within the paravertebral space as intended. Misplaced catheters were in the epidural space (3 cases), in the erector spinae musculature (5 cases) and in the pleural space (1 case). Seven patients had a clinically insufficient block resulting in a 23% failure rate. There was a discrepancy between the radiological findings and the observed distribution of loss of sensation. Conclusions: We can conclude that the paravertebral space is not suitable for catheters in current use and we suggest using single injection techniques unless the catheters are placed under direct vision by a surgeon.
    Regional Anesthesia and Pain Medicine. 01/2012; 37(5):E189.
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    ABSTRACT: To determine the frequency of apparent acute pulmonary embolism (PE) and of concomitant disease in computed tomography pulmonary angiography (CTPA); to compare the frequency of PE in patients with pneumonia or acute cardiac disorder (acute coronary syndrome, tachyarrhythmia, acute left ventricular heart failure or cardiogenic shock), with the frequency of PE in patients with none of these alternative chest pathologies (comparison group). Retrospective analysis of all patients who received a CTPA at the emergency department (ED) within a period of four years and 5 months. Of 1275 patients with CTPA, 28 (2.2%) had PE and concomitant radiologic evidence of another chest disease; 3 more (0.2%) had PE and an acute cardiac disorder without radiological evidence of heart failure. PE was found in 11 of 113 patients (10%) with pneumonia, in 5 of 154 patients (3.3%) with an acute cardiac disorder and in 186 of 1008 patients (18%) in the comparison group. After adjustment for risk factors for thromboembolism and for other relevant patient's characteristics, the proportion of CTPAs with evidence of PE in patients with an acute cardiac disorder or pneumonia was significantly lower than in the comparison group (OR 0.13, 95% CI 0.05-0.33, p<0.001 for patients with an acute cardiac disorder, and OR 0.45, 95% CI 0.23-0.89, p = 0.021 for patients with pneumonia). The frequency of PE and a concomitant disease that can mimic PE was low. The presence of an acute cardiac disorder or pneumonia was associated with decreased odds of PE.
    PLoS ONE 01/2012; 7(10):e47418. · 3.73 Impact Factor
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    ABSTRACT: The purpose of this study was to simulate pulmonary emboli (PE) and image quality at low tube energy and reduced contrast material volume in normal-dose pulmonary CT angiography (CTA) images and to analyze the diagnostic accuracy with normal- and low-dose pulmonary CTA. Normal-dose pulmonary CTA examinations using 120 kVp and 100 mL of contrast material in 10 patients with no PE were retrospectively selected. The image characteristics of an 80-kVp low-dose pulmonary CTA protocol (patient exposure reduction, 57%) with 75 mL of contrast material were simulated. Four different sets of filling defects were computer simulated in identical locations in each normal-dose and corresponding low-dose examination, equaling 783 PE in 40 normal-dose and 40 low-dose datasets. Ten normal-dose and 10 low-dose examinations contained no emboli and were used as controls. The 100 pulmonary CTA studies were randomly assessed by three readers blinded to PE location and image quality. The results were assessed by nonparametric tests and Student t tests. No difference was found between the CT protocols in terms of sensitivity, specificity, and positive and negative diagnostic likelihood ratios at all ramification levels of the pulmonary arteries (p = 0.343-1). The overall sensitivity and specificity with the normal and simulated low-dose protocols were 79.9% versus 81.3% and 98.0% versus 98.2% (p = 0.444 and 0.702), respectively. The diagnostic confidence (2.81 ± 0.39 vs 2.77 ± 0.47; p = 0.297) and overall image quality (3.92 ± 0.52 vs 3.83 ± 0.54; p = 0.216) were similar at 120 kV and 80 kV. The intraindividual comparison of diagnostic accuracy with normal-dose and simulated low-dose pulmonary CTA protocols revealed no difference under experimental conditions.
    American Journal of Roentgenology 11/2011; 197(5):W852-9. · 2.90 Impact Factor
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    ABSTRACT: The purpose of this article is to assess the impact of large patient size on the detection of hypovascular liver tumors with MDCT and the effect of a noise filter on image quality and lesion detection in obese patients. A liver phantom with 45 hypovascular tumors (diameters of 5, 10, and 15 mm) was placed into two water containers mimicking intermediate and large patients. The containers were scanned with a 64-MDCT scanner. The CT dataset from the large phantom was postprocessed using a noise filter. The image noise was measured and the contrast-to-noise ratio (CNR) of the tumors was calculated. Tumor detection was independently performed by three radiologists in a blinded fashion. The application of the noise filter in the large phantom yielded a reduction of image noise by 42% (p < 0.0001). The CNR values of the tumors in the nonfiltered and filtered large phantom were lower than that in the intermediate phantom (p < 0.05). In the non-filtered and filtered large phantom, 25% and 19% fewer tumors, respectively, were detected on average compared with the intermediate phantom (p < 0.01). The risk of missing hypovascular liver tumors with CT is substantially increased in large patients. A noise filter improves image quality in obese patients.
    American Journal of Roentgenology 06/2011; 196(6):W772-6. · 2.90 Impact Factor
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    ABSTRACT: To establish an education and training programme for the reduction of CT radiation doses and to assess this programme's efficacy. Ten radiological institutes were counselled. The optimisation programme included a small group workshop and a lecture on radiation dose reduction strategies. The radiation dose used for five CT protocols (paranasal sinuses, brain, chest, pulmonary angiography and abdomen) was assessed using the dose-length product (DLP) before and after the optimisation programme. The mean DLP values were compared with national diagnostic reference levels (DRLs). The average reduction of the DLP after optimisation was 37% for the sinuses (180 vs. 113 mGycm, P < 0.001), 9% for the brain (982 vs. 896 mGycm, P < 0.05), 24% for the chest (425 vs. 322 mGycm, P < 0.05) and 42% for the pulmonary arteries (352 vs. 203 mGycm, P < 0.001). No significant change in DLP was found for abdominal CT. The post-optimisation DLP values of the sinuses, brain, chest, pulmonary arteries and abdomen were 68%, 10%, 20%, 55% and 15% below the DRL, respectively. The education and training programme for radiological institutes is effective in achieving a substantial reduction in CT radiation dose.
    European Radiology 05/2011; 21(10):2039-45. · 4.34 Impact Factor

Publication Stats

383 Citations
160.15 Total Impact Points


  • 2008–2014
    • Inselspital, Universitätsspital Bern
      • University Institute of Diagnostic, Interventional and Pediatric Radiology
      Berna, Bern, Switzerland
  • 2012
    • Universitätsspital Basel
      Bâle, Basel-City, Switzerland
  • 2011
    • Spitalzentrum Biel-Bienne
      Bienne, Bern, Switzerland