Zsolt Szucs-Farkas

Inselspital, Universitätsspital Bern, Berna, Bern, Switzerland

Are you Zsolt Szucs-Farkas?

Claim your profile

Publications (55)160.02 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We assessed quality and diagnostic confidence with 100 kVp CTPA at high body weight•Results in 75–99 kg, 100–125 kg and >125 kg groups were compared (216 patients)•Subjective quality and confidence did not differ between the body weight groups•Diagnostic confidence in non-obese and obese patients was not different either•CTPA at 100 kVp provides good quality and diagnostic confidence in patients <125kg; >125kg is unknown
    Clinical Radiology. 10/2014;
  • [Show abstract] [Hide abstract]
    ABSTRACT: To compare image quality and low-contrast detectability of an integrated circuit (IC) detector in abdominal CT of obese patients with conventional detector technology at low tube voltages.
    European radiology. 10/2014;
  • [Show abstract] [Hide abstract]
    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;
  • Source
    [Show abstract] [Hide abstract]
    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
  • [Show abstract] [Hide abstract]
    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
  • [Show abstract] [Hide abstract]
    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; · 2.30 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: PURPOSE To assess the image quality and low-contrast detectability of simulated liver lesions in abdominal CT using a dual-source, dual-energy and a single-energy technique at similar radiation dose in a phantom. METHOD AND MATERIALS A custom liver phantom with 43 hypodense tumors (diameters of 5, 10 and 15 mm; tumor-to-liver contrast of -10, -25, and -50 HU) was placed in a cylindrical water container that mimicked an intermediate-sized patient. The phantom was scanned with a dual-source CT scanner (Somatom Definition Flash, Siemens) using a single-energy protocol (120 kVp, 150 reference mAs) and a dual-energy protocol (tube A, 100 kVp, 190 reference mAs; tube B, 140 kVp, 162 reference mAs). Automatic tube current modulation was used for both CT protocols. The radiation dose was assessed with the volume CT dose index (CTDIvol). The image noise was measured, and the contrast-to-noise ratio (CNR) of the tumors was calculated. Tumor detection was independently performed by three blinded radiologists. Statistical analysis included analysis of variance and non-parametric tests. RESULTS The CTDIvol measured 14.9 mGy for the single-energy protocol and 14.6 mGy for the dual-energy protocol. The image noise was significantly lower in the dual-energy compared to the single-energy protocol (14.4 vs. 17.8 HU, respectively; P < 0.01). The CNR of the dual-energy protocol was significantly higher compared to the single-energy protocol (3.8 vs 3.1, respectively; P < 0.01). The overall sensitivity for tumor detection measured 74.4%, and 82.2% for the single-energy and dual-energy protocol, respectively (P = 0.45). CONCLUSION At similar radiation dose, abdominal dual-source, dual-energy CT demonstrates a significantly improved quantitative image quality and trend for improved low-contrast detectability compared to single-energy CT. CLINICAL RELEVANCE/APPLICATION Abdominal dual-source, dual-energy CT improves radiation dose efficiency compared to single-energy CT.
    Radiological Society of North America 2013 Scientific Assembly and Annual Meeting; 12/2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: PURPOSE To assess the image quality, iodine quantification and low-contrast detectability in abdominal dual-source, dual-energy CT at different radiation dose levels in a phantom. METHOD AND MATERIALS A custom liver phantom with 43 hypodense tumors (diameters of 5, 10 and 15 mm; tumor-to-liver contrast of -10, -25, and -50 HU) and eight tubes containing solutions of varying iodine concentration (0-22 mg/ml) were placed in a cylindrical water container that mimicked an intermediate-sized patient. The phantoms were scanned with a dual-source CT scanner (Somatom Definition Flash, Siemens) using the abdominal dual-energy protocol recommended by the vendor (tube A, 100 kVp, 230 reference mAs; tube B, 140 kVp, 196 reference mAs) (protocol A). The phantoms were also scanned with three dose-optimized protocols in which the reference mAs setting of tube A was reduced by 40, 80 and 120 compared to protocol A (protocol B, C and D, respectively). The radiation dose was assessed with the volume CT dose index (CTDIvol). 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. Software provided by the vendor was used for iodine quantification. Kruskal-Wallis test was used to compare iodine measurements between protocols. RESULTS The CTDIvol of protocol A, B, C and D measured 17.7, 14.6, 11.5 and 8.5 mGy, respectively. As the radiation dose decreased, the image noise increased (13.2, 14.4, 16.7 and 19.4 HU for protocol A, B, C and D, respectively) and the CNR decreased (4.4, 3.8, 3.1, and 2.7 for protocol A, B, C and D, respectively) (P < 0.05). The overall sensitivity for tumor detection measured 82.2%, 82.2%, 81.4% and 79.8% (P = 0.789). Quantitative iodine measurements showed no significant difference in the four protocols (P = 0.996). CONCLUSION The radiation dose of the abdominal dual-energy CT protocol that is provided by the vendor can be reduced by at least 50% while maintaining low-contrast detectability and accuracy in iodine quantification. Image noise and CNR is not an adequate surrogate for evaluating the potential for radiation dose reduction. CLINICAL RELEVANCE/APPLICATION The radiation dose-optimized abdominal dual-source, dual-energy CT protocol improves patient safety without degradation of diagnostic accuracy.
    Radiological Society of North America 2013 Scientific Assembly and Annual Meeting; 12/2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: PURPOSE To compare diagnostic accuracy of low-dose computed tomography pulmonary angiography (CTPA), with both reduced radiation and reduced contrast material (CM) dose with a normal-dose protocol in detecting acute pulmonary embolism (PE). METHOD AND MATERIALS The Reduced Dose in Pulmonary Embolism Detection (REDOPED) trial was a single-centre, single-blinded, HIPAA-complient, prospective randomized study. Five hundred and one patients with body weights of <100 kg with suspected acute PE were assigned to normal-dose CTPA (255 patients; 100 kVp tube energy and 100 mL CM of 300 mgI/mL) and low-dose CTPA (246 patients; 80 kVp tube voltage and 75 mL CM of 300 mgI/mL). Primary endpoints were evidence of PE in CTPA and accuracy of CTPA on a composite reference standard. Secondary endpoints were PE and PE-related death within 90 days after CTPA and radiation dose. RESULTS The reference diagnosis was equivocal in 20 of 501 patients. CTPA diagnosis was correct in 240 patients and incorrect in 5 in the normal-dose group. CTPA was correct in 230 cases and incorrect in 6 in the low-dose group (odds ratio 1.25, 95% confidence interval, 0.38 to 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 90-day follow-up. The mean estimated effective dose was 3.28 mSv in the normal-dose group and 2.25 mSv in the low-dose group, corresponding to a reduction by 31% (P<0.001). CONCLUSION The accuracy of low-dose CTPA with reduced radiation and reduced CM dose is not significantly different from that of normal-dose CTPA in detecting or excluding acute PE in patients weighing <100 kg. CLINICAL RELEVANCE/APPLICATION CTPA with 80 kVp tube voltage provides high accuracy at reduced radiation and reduced CM dose and can be recommended for routine PE diagnosis in patients weighing <100 kg.
    Radiological Society of North America 2013 Scientific Assembly and Annual Meeting; 12/2013
  • [Show abstract] [Hide abstract]
    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
  • [Show abstract] [Hide abstract]
    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
  • [Show abstract] [Hide abstract]
    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
  • [Show abstract] [Hide abstract]
    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
  • [Show abstract] [Hide abstract]
    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
  • Source
    [Show abstract] [Hide abstract]
    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. · 3.53 Impact Factor
  • [Show abstract] [Hide abstract]
    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; · 1.66 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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
  • [Show abstract] [Hide abstract]
    ABSTRACT: PURPOSE To compare diagnostic accuracy, qualitative and quantitative image quality on full and reduced radiation dose abdominal CT reconstructed with two different algorithms – filtered back projection (FBP) and model based iterative reconstruction (MBIR). METHOD AND MATERIALS A custom built phantom simulating the liver during the portal venous phase containing 43 simulated hypovascular lesions in three sizes (5, 10 and 15mm) and three tumor-to-liver contrast levels (10, 25 and 50 HU) was placed in a water filled cylindrical container mimicking an intermediate size patient. Imaging was performed at 120 kVp and four incrementally decreasing dose levels (100%=188 mAs, 50%=95 mAs, 25%=48 mAs and 10%=20 mAs). Each acquisition was reconstructed with FBP and MBIR resulting in eight datasets. For quantitative analysis contrast-to-noise ratios (CNR) and image noise were measured. Qualitative image analysis consisted of lesion detection and subjective image quality scores (5-point scale; 1=worst and 5=best for confidence, image noise and overall image quality). Qualitative and quantitative results were compared between the different datasets. RESULTS CNR on MBIR images was significantly higher (mean 246%, 151-383%) and image noise was significantly lower (mean 69%, 59-78%) than on FBP images at the same radiation dose (P <.05). On 10% radiation dose MBIR images, CNR (3.27 ± 0.26) was significantly higher and image noise (15.25 ± 1.10) was significantly lower than on full dose FBP images (CNR: 2.54 ± 0.07; image noise: 20.58 ± 0.76) (P<.05). Lesion detection and subjective image quality scores slightly improved on MBIR images compared to FBP images at the same radiation dose and similar on 50% radiation dose MBIR images (sensitivity: 84%; confidence: 3.61; subj. image noise: 4; subj. image quality: 5) compared to full dose FBP images (sensitivity 86%; confidence: 3.78; subj. image noise: 4; subj. image quality: 5). CONCLUSION Model based iterative reconstruction for abdominal CT allows for a 50% reduction in radiation dose, without compromising diagnostic accuracy, qualitative or quantitative image parameters. CLINICAL RELEVANCE/APPLICATION Model based iterative reconstruction provides adequate image quality at low radiation dose in abdominal CT, and therefore is a helpful tool in radiation dose reduction.
    Radiological Society of North America 2012 Scientific Assembly and Annual Meeting; 11/2012
  • [Show abstract] [Hide abstract]
    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
  • [Show abstract] [Hide abstract]
    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

Publication Stats

415 Citations
160.02 Total Impact Points

Institutions

  • 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