Hatem Alkadhi

University of Zurich, Zürich, Zurich, Switzerland

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Publications (461)1417.74 Total impact

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    ABSTRACT: Purpose: To investigate diagnostic performance of advanced modelled iterative reconstruction (ADMIRE) to filtered back projection (FBP) when using an ultra-low dose protocol for the detection of solid and sub-solid pulmonary-nodules. Methods: Single-energy CT was performed at 100kVp with tin-filtration in an anthropomorphic chest-phantom with solid and sub-solid pulmonary-nodules (2-10mm, attenuation, 20HU to -800HU at 120 kVp). CTDIvol of the standard chest protocol was 2.2 mGy. Subsequent scans were obtained at 1/8 (0.28 mGy), 1/20 (0.10 mGy), and 1/70 (0.03 mGy) dose levels by lowering tube-voltage and -current. Images were reconstructed with FBP and ADMIRE. One reader measured image noise; two readers determined image quality and assessed nodule localization. Results: Image noise was significantly reduced using ADMIRE compared to FBP (ADMIRE at a strength-level of 5: 70.4% for 1/20; 71.6% for 1/8;p<0.001). Inter-observer agreement for image-quality was excellent (k=0.88). Image-quality was considered diagnostic for all images at 1/20 dose using ADMIRE. Sensitivity of nodule detection was 97.14% (100% for solid, 93.8% for sub-solid nodules) at 1/20 dose and 100% for both nodule entities at 1/8 dose using ADMIRE5. Images obtained with 1/70 dose had moderate sensitivity (overall85.71%; solid 94%; sub-solid 73.3%). Conclusion: Our study suggests that with a combination of tin-filtration and ADMIRE the mean volume CT dose index (CTDIvol) of chest CT can be lowered considerably, while sensitivity for nodule-detection remains high. For solid nodules CTDIvol was 0.10 mGy, while sub-solid nodules required a slightly higher CTDIvol of 0.28 mGy. Advances in knowledge: Detection of sub-solid nodules is feasible with ultralow-dose protocols.
    The British journal of radiology 10/2015; DOI:10.1259/bjr.20150389 · 2.03 Impact Factor
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    ABSTRACT: Objective: The purpose of this study was to evaluate the influence of sinogram-affirmed iterative reconstruction (SAFIRE) on quantification of lung volume and pulmonary emphysema in low-dose chest computed tomography compared with filtered back projection (FBP). Methods: Enhanced or nonenhanced low-dose chest computed tomography was performed in 20 patients with chronic obstructive pulmonary disease (group A) and in 20 patients without lung disease (group B). Data sets were reconstructed with FBP and SAFIRE strength levels 3 to 5. Two readers semiautomatically evaluated lung volumes and automatically quantified pulmonary emphysema, and another assessed image quality. Radiation dose parameters were recorded. Results: Lung volume between FBP and SAFIRE 3 to 5 was not significantly different among both groups (all P > 0.05). When compared with those of FBP, total emphysema volume was significantly lower among reconstructions with SAFIRE 4 and 5 (mean difference, 0.56 and 0.79 L; all P < 0.001). There was no nondiagnostic image quality. Conclusions: Sinogram-affirmed iterative reconstruction does not alter lung volume measurements, although quantification of lung emphysema is affected at higher strength levels.
    Journal of computer assisted tomography 10/2015; DOI:10.1097/RCT.0000000000000313 · 1.41 Impact Factor
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    ABSTRACT: This study investigates the capabilities of low tube voltage computed tomography (CT) and dual-energy CT (DECT) for predicting successful shock wave lithotripsy (SWL) of urinary stones in vitro. A total of 33 urinary calculi (six different chemical compositions; mean size 6 ± 3 mm) were scanned using a dual-source CT machine with single- (120 kVp) and dual-energy settings (80/150, 100/150 Sn kVp) resulting in six different datasets. The attenuation (Hounsfield Units) of calculi was measured on single-energy CT images and the dual-energy indices (DEIs) were calculated from DECT acquisitions. Calculi underwent SWL and the number of shock waves for successful disintegration was recorded. The prediction of required shock waves regarding stone attenuation/DEI was calculated using regression analysis (adjusted for stone size and composition) and the correlation between CT attenuation/DEI and the number of shock waves was assessed for all datasets. The median number of shock waves for successful stone disintegration was 72 (interquartile range 30-361). CT attenuation/DEI of stones was a significant, independent predictor (P < 0.01) for the number of required shock waves with the best prediction at 80 kVp (β estimate 0.576) (P < 0.05). Correlation coefficients between attenuation/DEI and the number of required shock waves ranged between ρ = 0.31 and 0.68 showing the best correlation at 80 kVp (P < 0.001). The attenuation of urinary stones at low tube voltage CT is the best predictor for successful stone disintegration, being independent of stone composition and size. DECT shows no added value for predicting the success of SWL.
    Urolithiasis 09/2015; DOI:10.1007/s00240-015-0824-y · 1.00 Impact Factor
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    ABSTRACT: To evaluate in patients with hepatocellular carcinoma (HCC), whether assessment of tumor heterogeneity by histogram analysis of computed tomography (CT) perfusion helps predicting response to transarterial radioembolization (TARE). Sixteen patients (15 male; mean age 65 years; age range 47-80 years) with HCC underwent CT liver perfusion for treatment planning prior to TARE with Yttrium-90 microspheres. Arterial perfusion (AP) derived from CT perfusion was measured in the entire tumor volume, and heterogeneity was analyzed voxel-wise by histogram analysis. Response to TARE was evaluated on follow-up imaging (median follow-up, 129 days) based on modified Response Evaluation Criteria in Solid Tumors (mRECIST). Results of histogram analysis and mean AP values of the tumor were compared between responders and non-responders. Receiver operating characteristics were calculated to determine the parameters' ability to discriminate responders from non-responders. According to mRECIST, 8 patients (50 %) were responders and 8 (50 %) non-responders. Comparing responders and non-responders, the 50th and 75th percentile of AP derived from histogram analysis was significantly different [AP 43.8/54.3 vs. 27.6/34.3 mL min(-1) 100 mL(-1)); p < 0.05], while the mean AP of HCCs (43.5 vs. 27.9 mL min(-1) 100 mL(-1); p > 0.05) was not. Further heterogeneity parameters from histogram analysis (skewness, coefficient of variation, and 25th percentile) did not differ between responders and non-responders (p > 0.05). If the cut-off for the 75th percentile was set to an AP of 37.5 mL min(-1) 100 mL(-1), therapy response could be predicted with a sensitivity of 88 % (7/8) and specificity of 75 % (6/8). Voxel-wise histogram analysis of pretreatment CT perfusion indicating tumor heterogeneity of HCC improves the pretreatment prediction of response to TARE.
    CardioVascular and Interventional Radiology 07/2015; DOI:10.1007/s00270-015-1185-1 · 2.07 Impact Factor
  • A Meier · M Wurnig · L Desbiolles · S Leschka · T Frauenfelder · H Alkadhi ·
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    ABSTRACT: To investigate the value of advanced virtual monoenergetic image reconstruction (mono-plus) from dual-energy computed tomography (CT) for improving the contrast of CT pulmonary angiography (CTPA). Forty consecutive patients (25 women, mean 62.5 years, range 28-87 years) underwent 192-section dual-source CTPA with dual-energy CT (90/150 SnkVp) after the administration of 60 ml contrast media (300 mg iodine/ml). Conventional virtual monochromatic images at 60 keV and 17 mono-plus image datasets from 40-190 keV (in 10 keV steps) were reconstructed. Subjective image quality (artefacts, subjective noise) was rated. Attenuation was measured in the pulmonary trunk and in the right lower lobe pulmonary artery; noise was measured in the periscapular musculature. The signal-to-noise (SNR) and contrast-to-noise ratios (CNR) were calculated for each patient and dataset. Comparisons between monochromatic images and mono-plus images were performed by repeated measures analysis of variance (ANOVA) with post-hoc Bonferroni correction. Interreader agreement was good to excellent for subjective image quality (ICC: 0.616-0.889). As compared to conventional 60 keV images, artefacts occurred less (p=0.001) and subjective noise was rated lower (p<0.001) in mono-plus 40 keV images. Noise was lower (p<0.001), and the SNR and CNR in the pulmonary trunk and right lower lobe pulmonary artery were higher (both, p<0.001) in mono-plus 40 keV images compared to conventional monoenergetic 60 keV images. Transient interruption of contrast (TIC) was found in 14/40 (35%) of patients, with subjective contrast being similar 8/40 (20%) or higher 32/40 (80%) in mono-plus 40 keV as compared to conventional monoenergetic 60 keV images. Compared to conventional virtual monoenergetic imaging, mono-plus images at 40 keV improve the contrast of dual-energy CTPA. Copyright © 2015 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
    Clinical Radiology 07/2015; 70(11). DOI:10.1016/j.crad.2015.06.094 · 1.76 Impact Factor
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    ABSTRACT: The aim of this study was to directly compare metal artifact reduction (MAR) of virtual monoenergetic extrapolations (VMEs) from dual-energy computed tomography (CT) with iterative MAR (iMAR) from single energy in pelvic CT with hip prostheses. A human pelvis phantom with unilateral or bilateral metal inserts of different material (steel and titanium) was scanned with third-generation dual-source CT using single (120 kVp) and dual-energy (100/150 kVp) at similar radiation dose (CT dose index, 7.15 mGy). Three image series for each phantom configuration were reconstructed: uncorrected, VME, and iMAR. Two independent, blinded radiologists assessed image quality quantitatively (noise and attenuation) and subjectively (5-point Likert scale). Intraclass correlation coefficients (ICCs) and Cohen κ were calculated to evaluate interreader agreements. Repeated measures analysis of variance and Friedman test were used to compare quantitative and qualitative image quality. Post hoc testing was performed using a corrected (Bonferroni) P < 0.017. Agreements between readers were high for noise (all, ICC ≥ 0.975) and attenuation (all, ICC ≥ 0.986); agreements for qualitative assessment were good to perfect (all, κ ≥ 0.678). Compared with uncorrected images, VME showed significant noise reduction in the phantom with titanium only (P < 0.017), and iMAR showed significantly lower noise in all regions and phantom configurations (all, P < 0.017). In all phantom configurations, deviations of attenuation were smallest in images reconstructed with iMAR. For VME, there was a tendency toward higher subjective image quality in phantoms with titanium compared with uncorrected images, however, without reaching statistical significance (P > 0.017). Subjective image quality was rated significantly higher for images reconstructed with iMAR than for uncorrected images in all phantom configurations (all, P < 0.017). Iterative MAR showed better MAR capabilities than VME in settings with bilateral hip prosthesis or unilateral steel prosthesis. In settings with unilateral hip prosthesis made of titanium, VME and iMAR performed similarly well.
    Investigative radiology 07/2015; DOI:10.1097/RLI.0000000000000191 · 4.44 Impact Factor
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    ABSTRACT: To determine MR-imaging features for the differentiation between hepatocellular carcinoma (HCC) and benign hepatocellular tumors in the non-cirrhotic liver. 107 consecutive patients without liver cirrhosis (46 male; 45±14 years) who underwent liver resection due to suspicion of HCC were included in this multi-center study. The following imaging features were assessed: lesion diameter and demarcation, satellite-lesions, central-scar, capsule, fat-content, hemorrhage, vein-infiltration and signal-intensity (SI) on native T1-, T2- and dynamic-enhanced T1-weighted images (center versus periphery). In addition, contrast-media (CM) uptake in the liver specific phase was analyzed in a sub-group of 42 patients. Significant differences between HCC (n=55) and benign lesions (n=52) were shown for native T1-, T2- and dynamic-enhanced T1-SI, fat-content, and satellite-lesions (all, P<.05). Independent predictors for HCC were T1-hypointensity (odds-ratio, 4.81), T2-hypo-/hyperintensity (5.07), lack of central tumor-enhancement (3.36), and satellite-lesions (5.78; all P<0.05). Sensitivity and specificity of HCC was 91% and 75% respectively for two out-of four independent predictors, whereas specificity reached 98% for all four predictors. Sub-analysis, showed significant differences in liver specific CM uptake between HCC (n=18) and benign lesions (n=24; P<0.001) and revealed lack of liver specific CM uptake (odds-ratio, 2.7) as additional independent feature for diagnosis of HCC. Independent MRI features indicating HCC are T1-hypointensity, T2-hypo- or hyperintensity, lack of central tumor-enhancement, presence of satellite-lesions and lack of liver specific CM-uptake. These features may have the potential to improve the diagnosis of HCC in the non-cirrhotic liver. Copyright © 2015. Published by Elsevier Ireland Ltd.
    European journal of radiology 07/2015; 84(10). DOI:10.1016/j.ejrad.2015.06.029 · 2.37 Impact Factor
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    ABSTRACT: The advent of computed tomography (CT) has revolutionized radiology. Starting as head-only scanners, modern CT systems are now capable of performing whole-body examinations within a couple of seconds in isotropic resolution. Technical advancements of scanner hardware and image reconstruction techniques are reviewed and discussed in their clinical context. These improvements have led to a steady increase of CT examinations in all age groups for a number of reasons. On the one hand, it is very easy today to obtain whole-body data for oncologic staging and follow-up or for trauma imaging. On the other hand, new examinations such as cardiac imaging, virtual colonoscopy, gout imaging, and whole-organ perfusion imaging have widened the application profile of CT. The increasing awareness of risks associated with radiation exposure triggered the development of a variety of dose reduction techniques. Effective dose values below 1 mSv, less than the annual natural background radiation (3.1 mSv/year on average in the United States), are now routinely possible for a number of dedicated examinations, even for coronary CT angiography.
    Investigative radiology 07/2015; 50(9). DOI:10.1097/RLI.0000000000000172 · 4.44 Impact Factor
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    ABSTRACT: Purpose To evaluate the potential of advanced modeled iterative reconstruction (ADMIRE) for optimizing radiation dose of high-pitch coronary CT angiography (CCTA). Methods High-pitch 192-slice dual-source CCTA was performed in 25 patients (group 1) according to standard settings (ref. 100 kVp, ref. 270 mAs/rot). Images were reconstructed with filtered back projection (FBP) and ADMIRE (strength levels 1–5). In another 25 patients (group 2), high-pitch CCTA protocol parameters were adapted according to results from group 1 (ref. 160 mAs/rot), and images were reconstructed with ADMIRE level 4. In ten patients of group 1, vessel sharpness using full width at half maximum (FWHM) analysis was determined. Image quality was assessed by two independent, blinded readers. Results Interobserver agreements for attenuation and noise were excellent (r = 0.88/0.85, p p p Conclusions In a selected population, ADMIRE can be used for optimizing high-pitch CCTA to an effective dose of 0.3 mSv. Key points • Advanced modeled IR (ADMIRE) reduces image noise up to 50 % as compared to FBP. • Coronary artery vessel borders show an increasing sharpness at higher ADMIRE levels. • High-pitch CCTA with ADMIRE is possible at a radiation dose of 0.3 mSv.
    European Radiology 06/2015; DOI:10.1007/s00330-015-3862-5 · 4.01 Impact Factor
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    ABSTRACT: To determine the value of advanced virtual monoenergetic images (mono+) from dual-energy computed tomography (CT) of hyperattenuating and hypoattenuating liver lesions in various phantom sizes and patients in comparison with standard monoenergetic images (mono). Anthropomorphic phantoms simulating 4 patient sizes (S, 300 × 200 mm; M, 350 × 250 mm; L, 400 × 300 mm; and XL, 600 × 450 mm) with a liver insert containing both hyperattenuating and hypoattenuating iodine-containing lesions were imaged with dose-equivalent dual-energy (100/150 Sn kilovolt [peak] [kV{p}]) and single-energy (120 kV[p]) protocols on a 192-slice dual-source CT system. In addition, 4 patients with 3 hypoattenuating and 3 hyperattenuating hepatocellular carcinoma were included and underwent dual-energy CT imaging with the same scanner at similar kV(p) settings (100/150 Sn kV[p]). Images were reconstructed with standard mono and with the mono+ algorithm at 10-kiloelectron volt (keV) intervals from 40 to 190 keV. Attenuation of the liver and lesions were measured, and contrast-to-noise ratios (CNRs) were calculated. Lesion conspicuity was rated by 2 blinded independent readers in all mono and mono+ data sets from 40 to 190 keV using a 5-point Likert scale (1, lowest conspicuity; and 5, highest conspicuity). Attenuation in the liver and in both hyperattenuating and hypoattenuating lesions did not differ between mono and mono+ (P = 0.41-0.49). Noise on mono+ was significantly lower than on mono for all phantom sizes (P < 0.05) and was increasing with phantom size. Hyperattenuating lesion CNR was highest for mono+ images at 40 keV in the S phantom (6.73), with significantly higher CNR for mono+ than for mono and for single energy (120 kV[p]) in all phantom sizes (all P < 0.001) except for the XL phantom. Hypoattenuating lesion CNR was highest for high-keV mono+ being significantly higher than on mono and on single-energy (120 kV[p]) images (all P < 0.001), except for the XL phantom with significantly higher CNR for mono (1.3) compared with mono+ (0.47) and 120 kV(p) (1.26). In patients, CNR curves of hyperattenuating hepatocellular carcinoma were in accordance with the phantom data, whereas hypoattenuating lesions demonstrate varying curves, some being in accordance with findings in phantoms. Interreader agreement for lesion conspicuity was very good (intraclass correlation, 0.95), with higher conspicuity scores for mono+ than for mono and single energy (120 kV[p]) at all phantom sizes (all P < 0.05) and within patients. Our ex vivo and patient data demonstrate added value for imaging of both hyperattenuating and hypoattenuating liver lesions with advanced virtual monoenergetic dual-energy CT by decreased noise, increased CNR, and higher lesion conspicuity, although with limitations in XL body sizes.
    Investigative radiology 05/2015; 50(10). DOI:10.1097/RLI.0000000000000171 · 4.44 Impact Factor
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    ABSTRACT: Purpose To investigate the accuracy of x-ray grating interferometry phase-contrast (PC) imaging for the characterization of human coronary artery plaque. Materials and Methods PC and conventional absorption computed tomographic (CT) imaging was performed ex vivo in this institutional review board-approved study in 40 human coronary artery segments by using a synchrotron radiation source. Qualitative analyses and calculations of image quality (McNemar test), plaque components (McNemar test), and plaque classification (Cohen κ test) according to the American Heart Association classification were performed in 38 plaques detected at histopathologic examination (reference standard). Quantitative measurements of plaque components (ie, collagen, lipids, smooth muscle, and calcifications) were compared among PC and absorption images by using analysis of variance for repeated measures with post hoc Bonferroni correction. Results Image quality was superior in PC (median image score, 1) in all cases (100%) compared with absorption imaging (median image score, 3) (P < .001). Plaque components were detected by means of PC without significant differences (seven of seven calcifications, 22 of 22 plaques with collagen and smooth muscle cells, P > .99; 29 of 29 plaques with lipids, P = .10) with histopathologic findings, whereas absorption imaging was used to detect calcifications (seven of seven, P > .99) without statistical differences only (nine of 29 plaques with lipids, 0 of 22 plaques with collagen and smooth muscle cells, P < .001). Accuracy for plaque stage assessment with PC (early vs advanced) was 100%, and characterization was correct in 33 of 38 plaques (87%), while conventional absorption imaging allowed correct characterization of seven plaques only (18%, P < .001). PC CT numbers were significantly different (P < .05) for all plaque components (mean for calcifications, 1236 HU ± 69; collagen, 78 HU ± 24; lipids, -18 HU ± 23; and smooth muscle cells, 34 HU ± 12), whereas absorption images showed significant differences (P < .001) between calcifications (1336 HU ± 241) and other plaque components, but not for collagen (22 HU ± 13), lipids (-15 HU ± 14), and smooth muscle (13 HU ± 9) (P > .99). Conclusion PC imaging allows accurate characterization of human coronary artery plaques and quantitative assessment of plaque components, thereby outperforming absorption imaging. (©) RSNA, 2015 Online supplemental material is available for this article.
    Radiology 05/2015; 277(1):141614. DOI:10.1148/radiol.2015141614 · 6.87 Impact Factor

  • Investigative Radiology 04/2015; 50(4):187. DOI:10.1097/RLI.0000000000000139 · 4.44 Impact Factor
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    ABSTRACT: To assess radiation dose and image quality in body CT-angiography (CTA) with automated attenuation-based tube voltage selection (ATVS) on a 192-slice dual-source CT (DSCT). Forty patients (69.5 ± 9.6 years) who had undergone body CTA with ATVS (ref.kVp 100, ref.mAs 90) using a 2x192-slice CT in single-source mode were retrospectively included. All patients had undergone prior CTA with a 2x128-slice CT and ATVS with identical imaging and contrast media protocols, serving for comparison. Images were reconstructed with iterative reconstruction at similar strength levels. Radiation dose was determined. Image quality was assessed semi-quantitatively (1:excellent, 5:non-diagnostic), aortic attenuation, noise and CNR were determined. As compared to 128-slice DSCT, 192-slice DSCT selected tube voltages were lower in 30 patients (75 %), higher in 3 (7.5 %), and similar in 7 patients (17.5 %). CTDIvol was lower with 192-slice DSCT (4.7 ± 1.9 mGy vs. 5.8 ± 2.1 mGy; p < 0.001). Subjective image quality, mean aortic attenuation (342 ± 67HU vs. 268 ± 67HU) and CNR (9.8 ± 2.5 vs. 8.2 ± 2.9) were higher with 192-slice DSCT (all p < 0.01), all datasets being diagnostic. Our study suggests that ATVS of 192-slice DSCT for body CTA is associated with an improved image quality and further radiation dose reduction of 19 % compared to 128-slice DSCT. • 192-slice DSCT allows imaging from 70 kVp to 150 kVp at 10 kVp increments. • 192-slice DSCT allows for radiation-dose reduction in body-CTA with ATVS. • Subjective and objective image quality increase compared to 128-slice DSCT.
    European Radiology 02/2015; 25(8). DOI:10.1007/s00330-015-3632-4 · 4.01 Impact Factor

  • European Heart Journal 02/2015; 36(16). DOI:10.1093/eurheartj/ehv020 · 15.20 Impact Factor
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    ABSTRACT: Objectives The aim of the study was to examine frequency, size, and localization of peri-device leaks after percutaneous left atrial appendage (LAA)-closure with the AMPLATZER-Cardiac-Plug (ACP) by using a multimodal imaging approach, i.e. combined cardiac-CT and TEE follow-up. Background Catheter-based LAA-occlusion using ACP aims to reduce the risk of stroke in patients with atrial fibrillation. Detection of peri-device leaks after ACP implantation by TEE is challenging, the few available data are inconsistent and the frequency of LAA leaks after ACP implantation remains therefore unclear. Methods Cardiac-CT using a multi-phase protocol and a second-generation dual-source-CT-system was performed in 24 patients with non-valvular atrial fibrillation starting 3 months after LAA-closure by ACP. Color Doppler multiplane TEE was used to evaluate peri-device flow. ResultsCardiac-CT follow-up detected any persistent LAA contrast filling in 62% of patients (n=15), but leak-sizes were small (1.51.4 mm). Peri-device leaks were almost exclusively localized at the posterior portion of the LAA-orifice (>90%). TEE follow-up revealed peri-device flow in 36% of patients (jet-sizes:4 mm). ACP-lobe compression (>10%) and perpendicular ACP-lobe orientation to the LAA-neck axis, that was also dependent on LAA anatomy, were substantially more frequent in patients with complete LAA closure. Conclusion The present study evaluates for the first time peri-device flow after LAA closure by ACP using a combined cardiac-CT and TEE follow-up. Persistent LAA-perfusion was frequently detected, leak-sizes were small and were less frequent when lobe compression was >10% and lobe orientation was perpendicular to the LAA-neck axis, that was also related to the LAA anatomy. The clinical significance of these small leaks after LAA-closure using ACP needs to be further evaluated in future studies. (c) 2014 Wiley Periodicals, Inc.
    Catheterization and Cardiovascular Interventions 02/2015; 85(2). DOI:10.1002/ccd.25667 · 2.11 Impact Factor
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    ABSTRACT: Objectives: To determine the number of imaging examinations, radiation dose, and the time to complete trauma-related imaging in multiple trauma patients before and after introduction of whole-body CT (WBCT) into early trauma care. Methods: 120 consecutive patients before and 120 patients after introduction of WBCT into our hospitals' trauma algorithm were compared regarding number and type of CT, radiography, focused assessment with sonography for trauma (FAST), additional CT examinations (defined as CT of same body regions after radiography and/or FAST), and the time to complete trauma-related imaging. Results: In the WBCT cohort significantly more patients underwent CT of the head, neck, chest, and abdomen (P<.001) as compared to the non-WBCT cohort, whereas the number of radiography of the cervical spine, chest and pelvis and of FAST examinations were significantly lower (P<.001). There were no significant differences between cohorts regarding the number of radiography of upper (P=.56) and lower extremities (P=.30). We found significantly higher effective doses in the WBCT (29.5mSv) as compared to the non-WBCT cohort (15.9mSv, P<.001), but less additional CT for completing the work-up were needed in the WBCT cohort (P<.001). The time to complete trauma-related imaging was significantly shorter in the WBCT (12min) as compared to the non-WBCT cohort (75min, P<.001). Conclusion: Including WBCT in the initial work-up of trauma patients results in higher radiation dose, but less additional CT is needed, and the time for completing trauma-related imaging is shorter. Advances in knowledge: WBCT in trauma patients is associated with a high radiation dose of 29.5mSv.
    British Journal of Radiology 01/2015; 88(1047):20140616. DOI:10.1259/bjr.20140616 · 2.03 Impact Factor
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    ABSTRACT: To investigate the dual-energy CT behavior of cocaine and heroin and of typical adulterants, and to evaluate the elemental composition of pure cocaine and heroin compared with cocaine and heroin in bodypacks. Pure heroin and pure synthetic cocaine samples, eight different adulterants, and in each case ten different bodypacks containing cocaine or heroin, were imaged at 80, 100, 120, and 140 kVp in a dual source CT system at two different degrees of compression. Two radiologists, blinded to the samples, measured the attenuation. The dual-energy index (DEI) was calculated. We performed atomic mass spectrometry for the elemental analysis of pure cocaine, pure heroin, and heroin and cocaine in bodypacks, and 140 kVp in a dual-source CT system. Inter- and intra-observer agreement for attenuation measurements was good (r = 0.61-0.72; p < 0.01). The cocaine bodypacks had a positive DEI of 0.029, while the pure drugs and the heroin bodypacks had a negative DEI (-0.051 to -0.027). Levamisole was the only substance which expressed a positive DEI of 0.011, while the remaining adulterants had negative DEIs ranging between -0.015 and -0.215. Atomic mass spectrometry revealed a concentration of tin in the cocaine bodypack that was 67 times higher than in the pure synthetic cocaine sample. The different DEIs of bodypacks containing cocaine and heroin allow them to be distinguished with dual-energy CT. Although the material properties of pure cocaine, pure heroin, or common drug extenders do not explain the differences in DEI, tin contamination during illicit natural cocaine production may be a possible explanation.
    Forensic Science Medicine and Pathology 01/2015; 11(1). DOI:10.1007/s12024-014-9643-7 · 1.98 Impact Factor
  • M Niemann · H Alkadhi · A Gotschy · S Kozerke · R Manka ·
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    ABSTRACT: Since the discovery of the obese (ob) gene product leptin, fat has been considered an endocrine organ. Especially epicardial fat has gained increasing attention in recent years. The epicardial fat plays a major role in fat metabolism; however, harmful properties have also been reported. Echocardiography, computed tomography and cardiac magnetic resonance imaging are the non-invasive tools used to measure epicardial fat volume. This review briefly introduces the basic physiological and pathophysiological considerations concerning epicardial fat. The main issue of this review is the presentation of non-invasive measurement techniques of epicardial fat using various imaging modalities and a literature overview of associations between epicardial fat and common cardiovascular diseases.
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    ABSTRACT: To compare low-contrast detectability, and qualitative and quantitative image parameters on standard and reduced radiation dose abdominal CT reconstructed with filtered back projection (FBP) and model-based iterative reconstruction (MBIR). A custom built liver phantom containing 43 lesions was imaged at 120 kVp and four radiation dose levels (100% = 188 mAs, 50%, 25%, and 10%). Image noise and contrast-to-noise ratios (CNR) were assessed. Lesion detection and qualitative image analysis (five-point Likert scale with 1 = worst, 5 = best for confidence) was performed by three independent radiologists. CNR on MBIR images was significantly higher (mean 246%, range 151-383%) and image noise was significantly lower (69%, 59-78%) than on FBP images at the same radiation dose (both p < 0.05). On MBIR 10% images, CNR (3.3 ± 0.3) was significantly higher and noise (15 ± 1HU) significantly lower than on FBP 100% images (2.5 ± 0.1; 21 ± 1 HU). On 100% images, lesion attenuation was significantly lower with MBIR than with FBP (mean difference -2 HU). Low-contrast detectability and qualitative results were similar with MBIR 50% and FBP 100%. Low-contrast detectability with MBIR 50% and FBP 100% were equal. Quantitative parameters on even lower dose MBIR images are superior to 100%-dose FBP images. Some attenuation values differ significantly with MBIR compared with FBP. Copyright © 2014 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
    Clinical Radiology 12/2014; 70(4). DOI:10.1016/j.crad.2014.11.015 · 1.76 Impact Factor
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    ABSTRACT: Current technological advances in CT, specifically those with a major impact on clinical imaging, are discussed. The intent was to provide for both medical physicists and practicing radiologists a summary of the clinical impact of each advance, offering guidance in terms of utility and day-to-day clinical implementation, with specific attention to radiation dose reduction.
    Investigative Radiology 12/2014; 50(2). DOI:10.1097/RLI.0000000000000125 · 4.44 Impact Factor

Publication Stats

10k Citations
1,417.74 Total Impact Points


  • 2000-2015
    • University of Zurich
      • • Institut für Diagnostische und Interventionelle Radiologie
      • • Center for Integrative Human Physiology
      • • Division of Neuropsychology
      Zürich, Zurich, Switzerland
  • 2009-2013
    • Harvard University
      Cambridge, Massachusetts, United States
  • 2011-2012
    • Massachusetts General Hospital
      Boston, Massachusetts, United States
  • 2003-2012
    • University Hospital Zürich
      Zürich, Zurich, Switzerland
  • 2010-2011
    • Harvard Medical School
      • Department of Radiology
      Boston, Massachusetts, United States
  • 2008
    • Kantonsspital St. Gallen
      San Gallo, Saint Gallen, Switzerland
  • 2001
    • ETH Zurich
      Zürich, Zurich, Switzerland