Marco Das

Publications of Marco Das

• Virtual elastic sphere processing enables reproducible quantification of vessel stenosis at CT and MR angiography.

  Authors: Felix Gremse, Christoph Grouls, Moritz Palmowski, Twan Lammers, Anke de Vries, Holger Grüll, Marco Das, Georg Mühlenbruch, Shamima Akhtar, Andreas Schober, Fabian Kiessling

  Radiology. 09/2011; 260(3):709-17.

  To develop and evaluate a user-friendly tool to enable efficient, accurate, and reproducible quantification of blood vessel stenosis in computed tomographic (CT) and magnetic resonance (MR)To develop and evaluate a user-friendly tool to enable efficient, accurate, and reproducible quantification of blood vessel stenosis in computed tomographic (CT) and magnetic resonance (MR) angiographic data sets. All clinical experiments were approved by the institutional review board, and informed patient consent was acquired. Animal experiments were approved by the governmental review committee on animal care. A virtual elastic sphere passes through a blood vessel specified by user-provided start and end points, and the adapting diameter over the course of the vessel is recorded. The program was tested in phantoms to determine the accuracy of diameter estimation, and it was applied in micro-CT data sets of mice with induced vessel stenosis. Dual-energy CT angiography and MR angiography were performed in 16 patients with carotid artery stenosis, and reproducibility and required reader time of this automated technique were compared with manual measurements. Additionally, the effect of dual-energy CT-based discrimination between iodine- and calcium-based enhancement was investigated. Differences between carotid artery diameters of mice and between automated and manual measurement durations were assessed with a paired t test. Reproducibility of stenosis scores was evaluated with the Fisher z test. Phantom diameters were determined with an average error of 0.094 mm. Diameters of normal and injured carotid arteries of mice were significantly different (P < .01). For patient data, automated interreader variability was significantly (P < .01) lower than manual intra- and interreader variability, while time efficiency was improved (P < .01). The virtual elastic sphere tool is applicable to CT, dual-energy CT, and MR angiography, and it improves reproducibility and efficiency over that achieved with manual stenosis measurements.

• Quantification of left and right ventricular function and myocardial mass: Comparison of low-radiation dose 2nd generation dual-source CT and cardiac MRI.

  Authors: Richard A P Takx, Antonio Moscariello, U Joseph Schoepf, J Michael Barraza, John W Nance, Gorka Bastarrika, Marco Das, Mathias Meyer, Joachim E Wildberger, Stefan O Schoenberg, Christian Fink, Thomas Henzler

  European journal of radiology. 08/2011;

  OBJECTIVE: To prospectively evaluate the accuracy of left and right ventricular function and myocardial mass measurements based on a dual-step, low radiation dose protocol with prospectivelyOBJECTIVE: To prospectively evaluate the accuracy of left and right ventricular function and myocardial mass measurements based on a dual-step, low radiation dose protocol with prospectively ECG-triggered 2nd generation dual-source CT (DSCT), using cardiac MRI (cMRI) as the reference standard. MATERIALS AND METHODS: Twenty patients underwent 1.5T cMRI and prospectively ECG-triggered dual-step pulsing cardiac DSCT. This image acquisition mode performs low-radiation (20% tube current) imaging over the majority of the cardiac cycle and applies full radiation only during a single adjustable phase. Full-radiation-phase images were used to assess cardiac morphology, while low-radiation-phase images were used to measure left and right ventricular function and mass. Quantitative CT measurements based on contiguous multiphase short-axis reconstructions from the axial CT data were compared with short-axis SSFP cardiac cine MRI. Contours were manually traced around the ventricular borders for calculation of left and right ventricular end-diastolic volume, end-systolic volume, stroke volume, ejection fraction and myocardial mass for both modalities. Statistical methods included independent t-tests, the Mann-Whitney U test, Pearson correlation statistics, and Bland-Altman analysis. RESULTS: All CT measurements of left and right ventricular function and mass correlated well with those from cMRI: for left/right end-diastolic volume r=0.885/0.801, left/right end-systolic volume r=0.947/0.879, left/right stroke volume r=0.620/0.697, left/right ejection fraction r=0.869/0.751, and left/right myocardial mass r=0.959/0.702. Mean radiation dose was 6.2±1.8mSv. CONCLUSIONS: Prospectively ECG-triggered, dual-step pulsing cardiac DSCT accurately quantifies left and right ventricular function and myocardial mass in comparison with cMRI with substantially lower radiation exposure than reported for traditional retrospective ECG-gating.

• Semiautomated versus manual evaluation of liver metastases treated by radiofrequency ablation.

  Authors: Sebastian Keil, Philipp Bruners, Lutz Ohnsorge, Cedric Plumhans, Florian F Behrendt, Sven Stanzel, Michael Sühling, Rolf W Günther, Marco Das, Andreas H Mahnken

  Journal of vascular and interventional radiology : JVIR. 02/2010; 21(2):245-51.

  To determine the accuracy of semiautomated volume and density measurements of liver metastases from colorectal and breast cancer before and after radiofrequency (RF) ablation compared with manualTo determine the accuracy of semiautomated volume and density measurements of liver metastases from colorectal and breast cancer before and after radiofrequency (RF) ablation compared with manual evaluation. Twenty-five patients (mean age, 63.2 years +/- 10.7) with 50 known liver metastases from underlying primary breast (n = 15) or colorectal cancer (n = 35) underwent triphasic contrast-enhanced multidetector computed tomography (CT) to evaluate hepatic tumor load and localization before RF ablation and for postinterventional follow-up. Each lesion was quantified in terms of volume and CT value (in HU) with a semiautomated software tool and manually by an experienced radiologist before and 4 months after RF ablation. Before RF ablation, all 50 liver metastases, and after ablation, 49 of 50 ablation zones (98%), were correctly evaluated by the software. Mean lesion volumes before and after the intervention were 5.5 cm(3) and 22.4 cm(3), respectively. Corresponding concordance correlation coefficients between measurement techniques were 0.98 and 0.99, respectively, for volume; and 0.90 and 0.76, respectively, for CT value. Compared with manual measurements, semiautomated volumetric assessment of liver metastases before and after RF ablation demonstrated a high degree of correlation. Agreement of attenuation was slightly worse, particularly when assessing the postinterventional multidetector CT examination, probably because of the different regions of interest used for manual and semiautomated assessment of CT values.

• Dose Reduction for Semi-Automated Volumetry of Hepatic Metastasis in MDCT Studies.

  Authors: Sebastian Keil, Cedric Plumhans, Istvan A Nagy, Katharina Schiffl, Grzegorz Soza, Florian F Behrendt, Andreas H Mahnken, Rolf W Günther, Marco Das

  Investigative radiology. 12/2009;

  OBJECTIVES:: To investigate the performance of semi-automated measurements (RECIST, volume) of hepatic metastases in multidetector-row computed tomography (MDCT) under normal-dose- and simulatedOBJECTIVES:: To investigate the performance of semi-automated measurements (RECIST, volume) of hepatic metastases in multidetector-row computed tomography (MDCT) under normal-dose- and simulated low-dose-protocols. MATERIALS AND METHODS:: Thirty-five patients (67 +/- 13 years) with a total of 79 hepatic metastases underwent 16-MDCT (120 kv, 160 mAseff, pitch 1, 3 mm slice thickness, 2 mm reconstruction increment, B30f standard soft tissue kernel) for either initial staging or therapy monitoring. Corresponding raw data from these standard-dose scans were simulated at lower radiation doses of 80/60/40 mAseff (Somatom Noise Vers.6.1 beta, Siemens Healthcare, Forchheim, Germany). A semi-automated software tool (SyngoCT Oncology, Siemens Healthcare, Forchheim, Germany) was applied to each dose setting to evaluate size parameters (RECIST, volume). These measurements were compared by applying repeated-measures analysis of variance and displayed graphically. RESULTS:: For RECIST measurements no statistically significant differences were found between standard dose (Mean RECIST diameter: 20.46 +/- 8.37 mm) and different simulated low radiation doses (80 mAseff: 20.95 +/- 8.20 mm/60 mAseff: 20.50 +/- 8.35 mm/40 mAseff: 19.95 +/- 8.16 mm): P = 0.0774.Statistically significant differences of volume quantification (P < 0.05) could be found between standard-(3.60 +/- 4.63 mL) and simulated lowest dose of 40 mAseff (3.17 +/- 4.08 mL), whereas there was no difference (P > 0.05) between 160 mAseff and either 80 mAseff(3.46 +/- 4.31 mL) or 60 mAseffprotocols (3.44 +/- 4.35 mL). CONCLUSIONS:: Software-assisted assessment of RECIST criteria and volume demonstrated valid performances under different dose-settings in MDCT; therefore, substantial radiation dose reduction could be possible with the use of semi-automated measurements in follow-up studies.

• Comparison of dual-source CT angiography and MR angiography in preoperative evaluation of intra- and extracranial vessels: a pilot study.

  Authors: Georg Mühlenbruch, Marco Das, Gottfried Mommertz, Meike Schaaf, Stefan Langer, Andreas Mahnken, Joachim Wildberger, A Thron, Rolf Günther, Timo Krings

  European radiology. 08/2009;

  Besides the assessment of carotid artery stenosis, evaluation of the vascular anatomy and lesions within both the extra- and intracranial arteries is crucial for proper clinical evaluation, treatmentBesides the assessment of carotid artery stenosis, evaluation of the vascular anatomy and lesions within both the extra- and intracranial arteries is crucial for proper clinical evaluation, treatment choice and planning. The purpose of our study was to evaluate the potential of dual-source CTA and 3T-MRA. In 16 symptomatic CAS patients, contrast-enhanced DSCT and 3T-MRA examinations were performed. For DSCT a dual-energy protocol with a 64 x 0.6-mm collimation was applied. In 3T-MRA intracranial high-resolution unenhanced TOF and extracranial contrast-enhanced MRA were performed. All examinations were analyzed for relevant morphologic and pathologic features or anomalies, and a total of 624 vessel segments were scored. All examinations were of diagnostic image quality with good to excellent vessel visibility. Almost all intracranial arteries were significantly better visualized by MRA compared to CTA (five of six vessels, p < 0.05). DSCT however allowed for further morphological carotid stenosis description, especially with respect to calcification. Although MRA proved to be superior in visualization of smaller intracranial arteries, all pre-interventionally relevant information could be perceived from DSCT. DSCT and MRA may both be regarded as a reliable, fast, pre-interventional imaging investigation in patients with carotid artery stenosis.

• Radiofrequency Ablation of Liver Metastases-Software-Assisted Evaluation of the Ablation Zone in MDCT: Tumor-Free Follow-Up Versus Local Recurrent Disease.

  Authors: Sebastian Keil, Philipp Bruners, Katharina Schiffl, Martin Sedlmair, Georg Mühlenbruch, Rolf Günther, Marco Das, Andreas Mahnken

  Cardiovascular and interventional radiology. 08/2009;

  The purpose of this study was to investigate differences in change of size and CT value between local recurrences and tumor-free areas after CT-guided radiofrequency ablation (RFA) of hepaticThe purpose of this study was to investigate differences in change of size and CT value between local recurrences and tumor-free areas after CT-guided radiofrequency ablation (RFA) of hepatic metastases during follow-up by means of dedicated software for automatic evaluation of hepatic lesions. Thirty-two patients with 54 liver metastases from breast or colorectal cancer underwent triphasic contrast-enhanced multidetector-row computed tomography (MDCT) to evaluate hepatic metastatic spread and localization before CT-guided RFA and for follow-up after intervention. Sixteen of these patients (65.1 +/- 10.3 years) with 30 metastases stayed tumor-free (group 1), while the other group (n = 16 with 24 metastases; 62.0 +/- 13.8 years) suffered from local recurrent disease (group 2). Applying an automated software tool (SyngoCT Oncology; Siemens Healthcare, Forchheim, Germany), size parameters (volume, RECIST, WHO) and attenuation were measured within the lesions before, 1 day after, and 28 days after RFA treatment. The natural logarithm (ln) of the quotient of the volume 1 day versus 28 days after RFA treament was computed: lnQ1//28/0(volume). Analogously, ln ratios of RECIST, WHO, and attenuation were computed and statistically evaluated by repeated-measures ANOVA. One lesion in group 2 was excluded from further evaluation due to automated missegmentation. Statistically significant differences between the two groups were observed with respect to initial volume, RECIST, and WHO (p < 0.05). Furthermore, ln ratios corresponding to volume, RECIST, and WHO differed significantly between the two groups. Attenuation evaluations showed no significant differences, but there was a trend toward attenuation assessment for the parameter lnQ28/0(attenuation) (p = 0.0527), showing higher values for group 1 (-0.4 +/- 0.3) compared to group 2 (-0.2 +/- 0.2). In conclusion, hepatic metastases and their zone of coagulation necrosis after RFA differed significantly between tumor-free and local-recurrent ablation zones with respect to the corresponding size parameters. A new parameter (lnQ1//28/0(volume/RECIST/WHO/attenuation)) was introduced, which appears to be of prognostic value at early follow-up CT.

• Global left ventricular function: assessment with dual-source CT versus conventional ventriculography in a porcine model.

  Authors: Philipp Bruners, Christian Knackstedt, Andreas H Mahnken, Nadja Luhmann, Marco Das, Christian Fach, Thomas Schmitz-Rode, Rolf W Günther, Malte Kelm, Georg Mühlenbruch

  Acta cardiologica. 07/2009; 64(3):311-9.

  OBJECTIVE: Cardiac computed tomography (CT) and conventional biplane ventriculography are established methods for the determination of ventricular function. Recently dual source CT was introduced forOBJECTIVE: Cardiac computed tomography (CT) and conventional biplane ventriculography are established methods for the determination of ventricular function. Recently dual source CT was introduced for cardiac CT scanning providing a temporal resolution of 83 ms independent of the patient's heart rate. The purpose of this study was to assess the global left ventricular function using retrospectively ECG-gated dual source computed tomography (DSCT) in comparison to conventional ventriculography. METHODS AND RESULTS: Contrast-enhanced cardiac DSCT and conventional ventriculography were performed in 10 domestic pigs with an approximate weight of 60 kg using standardized examination protocols under general anaesthesia. From manually drawn endocardial contours, LV end-systolic (ESV) and end-diastolic volume (EDV), stroke volume (SV), ejection fraction (EF) were calculated by means of dedicated analysis software separately for both examination modalities. LV functional parameters were analysed using Bland-Altman plots, Student t-test, and Pearson correlation coefficient. Left ESV and EDV determined with DSCT correlated well with conventional ventriculography results (ESV: r = 0.86; EDV: r = 0.72) with a good correlation also for SV (r = 0.67).An only moderate correlation was found for EF (r = 0.52). Student t-test showed a significant underestimation of SV and EF derived from DSCT in comparison to ventriculography. CONCLUSION: Retrospectively ECG-gated DSCT can accurately determine LV volumes in comparison to conventional ventriculography but provides lower SV and EF values; however, the correlation was only moderate.

• Effect of different saline chaser volumes and flow rates on intravascular contrast enhancement in CT using a circulation phantom.

  Authors: Florian F Behrendt, Philipp Bruners, Sebastian Keil, Cedric Plumhans, Andreas H Mahnken, Marco Das, Diana Ackermann, Rolf W Günther, Georg Mühlenbruch

  European journal of radiology. 05/2009;

  PURPOSE: To evaluate the influence of different saline chaser volumes and different saline chaser flow rates on the intravascular contrast enhancement in MDCT. MATERIALS AND METHODS: In aPURPOSE: To evaluate the influence of different saline chaser volumes and different saline chaser flow rates on the intravascular contrast enhancement in MDCT. MATERIALS AND METHODS: In a physiological flow phantom contrast medium (120ml, 300mgI/ml, Ultravist 300) was administered at a flow rate of 6ml/s followed by different saline chaser volumes (0, 30, 60 and 90ml) at the same injection rate or followed by a 30-ml saline chaser at different injection rates (2, 4, 6 and 8ml/s). Serial CT-scans at a level covering the pulmonary artery, the ascending and the descending aorta replica were obtained. Time-enhancement curves were computed and both pulmonary and aortic peak enhancement and peak time were determined. RESULTS: Compared to contrast medium injection without a saline chaser the pushing with a saline chaser (30, 60, and 90ml) resulted in a statistically significant increased pulmonary peak enhancement (all p=0.008) and prolonged peak time (p=0.032, p=0.024 and p=0.008, respectively). Highest aortic peak enhancement values were detected for a saline chaser volume of 30ml. A saline chaser flow rate of 8ml/s resulted in the highest pulmonary peak enhancement values compared to flow rates of 2, 4 and 6ml/s (all p=0.008). Aortic peak enhancement showed the highest values for a flow rate of 6ml/s. CONCLUSION: A saline chaser volume of 30ml and an injection rate of 6ml/s are sufficient to best improve vascular contrast enhancement in the pulmonary artery and the aorta in MDCT.

• Contrast enhancement in chest multidetector computed tomography: intraindividual comparison of 300 mg/ml versus 400 mg/ml iodinated contrast medium.

  Authors: Florian F Behrendt, Cedric Plumhans, Sebastian Keil, Georg Mühlenbruch, Marco Das, Peter Seidensticker, Christina Mutscher, Rolf W Günther, Andreas H Mahnken

  Academic radiology. 02/2009; 16(2):144-9.

  RATIONALE AND OBJECTIVES: We sought to intraindividually compare intravascular contrast enhancement in multidector computed tomography (MDCT) of the chest using contrast media (CM) containing 300 andRATIONALE AND OBJECTIVES: We sought to intraindividually compare intravascular contrast enhancement in multidector computed tomography (MDCT) of the chest using contrast media (CM) containing 300 and 400 mg iodine/ml. MATERIALS AND METHODS: Seventy-one patients underwent repeated MDCT scanning of the chest at baseline and follow-up. CM with standard iodine (protocol A: 300 mg iodine/ml; Iopromide 300) and high iodine concentration (protocol B: 400 mg iodine/ml; Iomeprol 400) were used. The iodine delivery rate (1.29 g iodine/s) and total iodine load (37 g iodine) were identical for the two protocols. Contrast enhancement was measured in the right and left ventricles, pulmonary trunk, right and left pulmonary arteries, and ascending and descending aortas. Results were compared using paired t-tests; P values were adjusted using Bonferroni correction (P <or= .005). RESULTS: Contrast enhancement values showed no statistically significant differences between the two protocols at all anatomic sites (all P > .005). In the right ventricle, pulmonary trunk, and right and left pulmonary arteries, higher attenuation values for protocol A were detected compared to protocol B (379.0 +/- 110.5 vs. 349.8 +/- 117.6, 354.5 +/- 112.2 vs 330.9 +/- 118.3, 348.6 +/- 106.0 vs. 321.8 +/- 109.9, and 347.9 +/- 102.4 vs. 321.0 +/- 104.9 HU, respectively). After the lung circulation (left ventricle, ascending aorta, and descending aorta), attenuation values were marginally higher for protocol B. Using both protocols resulted in suitable contrast enhancement with a mean pulmonary attenuation higher than 300 HU. CONCLUSIONS: Using an adapted injection protocol, the administration of 300 and 400 mg iodine CM resulted in a suitable intravascular contrast enhancement in the chest. The use of 400 mg iodine CM does not lead to a statistically significant improvement in contrast enhancement compared to the 300 mg iodine CM.

• Combined approach for a locked unilateral facet fracture-dislocation of the cervicothoracic junction.

  Authors: Bernhard Schmidt-Rohlfing, Matthias Nossek, Matthias Knobe, Marco Das

  Acta orthopaedica Belgica. 01/2009; 74(6):875-80.

  The authors present the case of a 36-year-old patient who sustained a unilateral fracture-dislocation C7-T1 involving all three columns, given the lesion of the C7-T1 disc on MRI. In view of theThe authors present the case of a 36-year-old patient who sustained a unilateral fracture-dislocation C7-T1 involving all three columns, given the lesion of the C7-T1 disc on MRI. In view of the fractured facet, closed reduction without anaesthesia was not attempted. First, open reduction and instrumentation were performed from posteriorly. In a second operation, anterior fusion C7-T1 was added, using a tricortical bone graft and instrumentation. The authors felt that this three-column lesion at the cervicothoracic junction necessitated combined posterior-anterior stabilisation.

• Automated measurement of lymph nodes: a phantom study.

  Authors: Sebastian Keil, Cedric Plumhans, Florian Behrendt, Sven Stanzel, Michael Suehling, Georg Mühlenbruch, Andreas Mahnken, Rolf Günther, Marco Das

  European radiology. 01/2009;

  The purpose of this study was to assess the accuracy of automated nodal quantification in a phantom. MDCT of a phantom with 17 synthetic lymph nodes of different sizes (diameter 6.0-30.0 mm) wasThe purpose of this study was to assess the accuracy of automated nodal quantification in a phantom. MDCT of a phantom with 17 synthetic lymph nodes of different sizes (diameter 6.0-30.0 mm) was performed at varying tube currents, reconstruction kernels and slice thicknesses. RECIST diameter and volume were measured using an automated software tool. Results were compared with the reference diameter and volume by calculating the absolute percentage error (APE). Degree of agreement between software and reference measurements was evaluated by computing corresponding concordance correlation coefficients (CCC). Under varying tube currents the mean APE (CCC) varied between 5.18% and 10.12% (0.95-0.99) for RECIST diameter and between 7.22% and 16.21% (0.94-1.00) for the volume. At different reconstruction kernels the mean APE values ranged between 7.20% and 7.55% (0.99) (RECIST) and between 8.96% and 14.42% (1.00) (volume). With different slice thicknesses the mean APE values differed from 5.81% to 9.20% (0.97-0.99) (RECIST) and from 8.16% to 22.66% (0.99-1.00) (volume). Regarding RECIST criteria and volume, automated evaluation of lymph nodes in a phantom demonstrated a high accuracy under varying MDCT parameters.

• Semi-Automated Quantification of Hepatic Lesions in a Phantom.

  Authors: Sebastian Keil, Cedric Plumhans, Florian Behrendt, Sven Stanzel, Michael Suehling, Georg Mühlenbruch, Andreas Mahnken, Rolf Günther, Marco Das

  Investigative radiology. 01/2009;

  PURPOSE:: Accurate measurement is crucial for the assessment of tumor dimensions to allow accurate evaluation of tumor response. Thus, the purpose of our study was to assess the accuracy ofPURPOSE:: Accurate measurement is crucial for the assessment of tumor dimensions to allow accurate evaluation of tumor response. Thus, the purpose of our study was to assess the accuracy of semi-automated RECIST and volumetric measurements of liver lesions in a liver phantom with different CT acquisition parameters. MATERIALS AND METHODS:: A phantom of the upper abdomen with 14 hepatic lesions of different sizes (diameter: 12.0-40.0 mm), densities (45/180 HU at 120 kV), or alignment (vertical/transverse) was scanned with a 16-slice multidetector row computed tomography using varying tube currents (40/60/80/100/120/165mAseff), reconstruction kernels (Siemens B20/30/40/50/70s), or slice thicknesses (1/2/3/4/5 mm). Longest axial diameter and volume of the 14 lesions were quantified using a semi-automated software tool (SyngoOncology, Siemens Medical Solutions, Forchheim, Germany) and compared with the known real longest axial diameter and volume values of the lesions. Absolute percentage errors (APE) were calculated. Degree of agreement in longest axial diameter and volume between software and real measurements was represented graphically in Bland-Altman plots and by corresponding concordance correlation coefficient. RESULTS:: At standard soft tissue reconstruction kernel (Siemens B30s) and slice thickness (3 mm) mean absolute percentage error APE (concordance correlation coefficients) ranged between 6.93 and 14.27 (0.96 and 0.99) for longest axial diameter and between 4.98 and 10.85 (0.99 and 1.00) for volume. At varying reconstruction kernels, APE values (concordance correlation coefficients) ranged between 7.92 and 8.31 (0.98 and 0.99) for longest axial diameter and between 4.95 and 6.93 (1.00) for volume. Applying different slice sections APE values (concordance correlation coefficients) differed from 6.54 to 11.82 (0.97 and 0.99) for longest axial diameter and from 6.93 to 9.17 (1.00) for volume. CONCLUSIONS:: Software quantification of longest axial diameter and volume of hepatic lesions in a phantom demonstrated a high correlation and accuracy under varying multidetector row computed tomography parameter.

• Impact of different vein catheter sizes for mechanical power injection in CT: in vitro evaluation with use of a circulation phantom.

  Authors: Florian F Behrendt, Philipp Bruners, Sebastian Keil, Cedric Plumhans, Andreas H Mahnken, Sven Stanzel, Marco Das, Rolf W Günther, Georg Mühlenbruch

  Cardiovascular and interventional radiology. 01/2009; 32(1):25-31.

  The purpose of this study was to evaluate the influence of different peripheral vein catheter sizes on the injection pressure, flow rate, injection duration, and intravascular contrast enhancement. AThe purpose of this study was to evaluate the influence of different peripheral vein catheter sizes on the injection pressure, flow rate, injection duration, and intravascular contrast enhancement. A flow phantom with a low-pressure venous compartment and a high-pressure arterial compartment simulating physiological circulation parameters was used. High-iodine-concentration contrast medium (370 mg iodine/ml; Ultravist 370) was administered in the venous compartment through peripheral vein catheters of different sizes (14, 16, 18, 20, 22, and 24 G) using a double-head power injector with a pressure limit of 325 psi. The flow rate was set to 5 ml/s, with a total iodine load of 36 g for all protocols. Serial CT scans at the level of the pulmonary artery and the ascending and the descending aorta replica were obtained. The true injection flow rate, injection pressure, injection duration, true contrast material volume, and pressure in the phantom during and after injection were continuously monitored. Time enhancement curves were computed and both pulmonary and aortic peak time and peak enhancement were determined. Using peripheral vein catheters with sizes of 14-20 G, flow rates of approximately 5 ml/s were obtained. During injection through a 22-G catheter the pressure limit was reached and the flow rate was decreased, with a consecutive decreased pulmonary and aortic contrast enhancement compared to the 14- to 20-G catheters. Injection through a 24-G peripheral vein catheter was not possible because of disconnection of the canula due to the high flow rate and pressure. In summary, intravenous catheters with sizes of 14-20 G are suitable for CT angiography using an injection protocol with a high flow rate and a high-iodine-concentration contrast medium.

• Which Iodine concentration in chest CT?--a prospective study in 300 patients.

  Authors: Georg Mühlenbruch, Florian F Behrendt, Mohammed A Eddahabi, Christian Knackstedt, Sven Stanzel, Marco Das, Peter Seidensticker, Rolf W Günther, Joachim E Wildberger, Andreas H Mahnken

  European radiology. 12/2008; 18(12):2826-32.

  In computed tomography (CT) several contrast media with different iodine concentrations are available. The aim of this study is to prospectively compare contrast media with iodine concentrations ofIn computed tomography (CT) several contrast media with different iodine concentrations are available. The aim of this study is to prospectively compare contrast media with iodine concentrations of 300, 370 and 400 mg iodine/ml for chest- CT. 300 consecutive patients were prospectively enrolled, under a waiver of the local ethics committee. The first (second, third) 100 patients, received contrast medium with 300 (370, 400) mg iodine/ml. Injection protocols were adapted for an identical iodine delivery rate (1.3 mg/s) and total iodine load (33 g) for all three groups. Standardized MDCT of the chest (16 x 0.75 mm, 120 kVp, 100 mAseff.) was performed. Intravascular attenuation values were measured in the pulmonary trunk and the ascending aorta; subjective image quality was rated on a 3-point-scale. Discomfort during and after injection was evaluated. There were no statistically significant differences in contrast enhancement comparing the three contrast media at the pulmonary trunk (p = 0.3198) and at the ascending aorta (p = 0.0840). Image quality (p = 0.0176) and discomfort during injection (p = 0.7034) were comparable for all groups. General discomfort after injection of contrast media with 300 mg iodine/ml was statistically significant higher compared to 370 mg iodine/ml (p = 0.00019). Given identical iodine delivery rates of 1.3 g/s and iodine loads of 33 g, contrast media with concentrations of 300, 370 and 400 mg iodine/ml do not result in different intravascular enhancement in chest-CT.

• Introduction of a Dedicated Circulation Phantom for Comprehensive In Vitro Analysis of Intravascular Contrast Material Application.

  Authors: Florian Behrendt, Philipp Bruners, John Kalafut, Andreas Mahnken, Sebastian Keil, Cedric Plumhans, Marco Das, Sven Stanzel, Joachim Wildberger, Jochen Pfeffer, Rolf Günther, Georg Mühlenbruch

  Investigative radiology. 11/2008; 43(10):729-736.

  OBJECTIVES:: To develop a circulation phantom with physiologic circulation parameters, including a pulmonary and a body circulation for the evaluation of intravascular contrast material (CM)OBJECTIVES:: To develop a circulation phantom with physiologic circulation parameters, including a pulmonary and a body circulation for the evaluation of intravascular contrast material (CM) application. MATERIALS AND METHODS:: The circulation phantom consists of a low-pressure venous system into which CM is injected, a pulmonary circulation, and high-pressure body circulation with an anthropometric aorta and coronary arteries. The phantom is driven by a pulsatile Harvard heart pump. Venous and arterial pressure were set to physiologic values with heart rate (60 beats/min), stroke volume (60 mL), and ratio of diastole to systole (60/40) also were within physiologic limits. CM with different iodine concentrations (300, 370, and 400 mg iodine/mL) were injected at a flow rate of 4 mL/s (iodine delivery rate: 1.2 g, 1.48 g, and 1.6 g iodine/s, respectively; total iodine load for all protocols: 36 g). Serial computed tomography scans at the level of the pulmonary artery, the ascending and the descending aorta replica were obtained. Dynamic pressure in the phantom and true injection system parameters (flow rate, injection pressure, and CM volume) was continuously monitored. Time-enhancement curves were calculated, and pulmonary and aortic peak time and enhancement were determined. Results were compared using nonparametric unpaired Wilcoxon tests. RESULTS:: The pressure in the phantom showed physiologic values for the low (mean pressure: 15 mm Hg) and high pressure part (125/75 mm Hg). Programmed injection values (flow rate, pressure, and volume) were reached for all injections. Using CM with 400 mg iodine/mL, the shortest pulmonary and aortic peak times and the highest pulmonary and aortic peak enhancement values were obtained compared with CM with 300 and 370 mg iodine/mL. CONCLUSIONS:: We developed a flow phantom with physiologic circulation parameters for measurement of contrast enhancement. The phantom is suitable for further evaluation of CM injection protocols for pulmonary and aortic enhancement.

• Semi-automated measurement of hyperdense, hypodense and heterogeneous hepatic metastasis on standard MDCT slices. Comparison of semi-automated and manual measurement of RECIST and WHO criteria.

  Authors: Sebastian Keil, Florian F Behrendt, Sven Stanzel, Michael Sühling, Alexander Koch, Jhenee Bubenzer, Georg Mühlenbruch, Andreas H Mahnken, Rolf W Günther, Marco Das

  European radiology. 11/2008; 18(11):2456-65.

  As semi-automated measurement would be desirable for lesion quantification and therapy-response control, the purpose of this study was to compare semi-automated measurements with manual assessment ofAs semi-automated measurement would be desirable for lesion quantification and therapy-response control, the purpose of this study was to compare semi-automated measurements with manual assessment of different types of hepatic metastases. Seventy-six patients with known liver metastases were analysed. All of them underwent contrast-enhanced 16-MDCT (16 x 0.75 mm collimation, 120 kV, 0.5 s rotation time, 160 mAs(eff)) for evaluation of follow-up status. On the basis of standard reconstructed 5-mm slices (in 4-mm increments), each lesion was quantified based on RECIST and WHO criteria using a semi-automated software tool (Syngo Oncology) and also manually by an experienced radiologist. Results from the software were compared to manual measurements. Statistical analysis was performed applying the concordance correlation coefficient, and results were represented graphically in Bland-Altman plots. A total of 52 hyperdense, 57 hypodense and 56 heterogeneous metastases were found and correctly measured by the software. All three lesion types revealed a strong correlation agreement between measurement techniques [RECIST diameter: 0.93 (hyperdense), 0.95(hypodense), 0.94 (heterogeneous); WHO area: 0.95, 0.98, 0.93]. Semi-automatic measurement of hyperdense, hypodense and heterogeneous liver metastases showed reliable results on standard axial reconstructions in comparison to manual quantification.

• Computer-aided detection of pulmonary embolism: Influence on radiologists' detection performance with respect to vessel segments.

  Authors: Marco Das, Georg Mühlenbruch, Anita Helm, Annemarie Bakai, Marcos Salganicoff, Sven Stanzel, Jianming Liang, Matthias Wolf, Rolf W Günther, Joachim Ernst Wildberger

  European radiology. 07/2008; 18(7):1350-5.

  The purpose was to assess the sensitivity of a CAD software prototype for the detection of pulmonary embolism in MDCT chest examinations with regard to vessel level and to assess the influence onThe purpose was to assess the sensitivity of a CAD software prototype for the detection of pulmonary embolism in MDCT chest examinations with regard to vessel level and to assess the influence on radiologists' detection performance. Forty-three patients with suspected PE were included in this retrospective study. MDCT chest examinations with a standard PE protocol were acquired at a 16-slice MDCT. All patient data were read by three radiologists (R1, R2, R3), and all thrombi were marked. A CAD prototype software was applied to all datasets, and each finding of the software was analyzed with regard to vessel level. The standard of reference was assessed in a consensus read. Sensitivity for the radiologists and CAD software was assessed. Thirty-three patients were positive for PE, with a total of 215 thrombi. The mean overall sensitivity for the CAD software alone was 83% (specificity, 80%). Radiologist sensitivity was 77% = R3, 82% = R2, and R1 = 87%. With the aid of the CAD software, sensitivities increased to 98% (R1), 93% (R2), and 92% (R3) (p<0.0001). CAD performance at the lobar level was 87%, at the segmental 90% and at the subsegmental 77%. With the use of CAD for PE, the detection performance of radiologists can be improved.

• Dose reduction during CT fluoroscopy: phantom study of angular beam modulation.

  Authors: Christian Hohl, Christoph Suess, Joachim E Wildberger, Dagmar Honnef, Marco Das, Georg Mühlenbruch, Andreas Schaller, Rolf W Günther, Andreas H Mahnken

  Radiology. 03/2008; 246(2):519-25.

  PURPOSE: To prospectively evaluate, in a phantom, the dose reductions achievable by using angular beam modulation (ABM) during computed tomographic (CT) fluoroscopy-guided thoracic interventions.PURPOSE: To prospectively evaluate, in a phantom, the dose reductions achievable by using angular beam modulation (ABM) during computed tomographic (CT) fluoroscopy-guided thoracic interventions. MATERIALS AND METHODS: To enable measurement of organ doses and effective patient dose, a female Alderson-Rando phantom was equipped with thermoluminescent dosimeters (TLDs) in 41 positions, with three TLDs in each position. Additionally, the local dose was assessed in 22 locations above the phantom to estimate the radiation exposure to the radiologist's hand and the patient's skin dose during thoracic interventions. Radiation exposure was performed with a 64-section multidetector CT scanner in the CT fluoroscopy mode, simulating a CT fluoroscopy-guided chest intervention. Effective dose, breast dose, and the dose to the radiologist's hand during the simulated chest intervention were measured with and without ABM. Image noise as an indicator for image quality was compared for both settings. Statistical significance of the measured dose reductions and the image noise was tested by using the paired-samples t test, with P < .05 indicating a significant difference. RESULTS: ABM significantly reduced the effective patient dose by 35%, the skin dose by 75%, the breast dose by 47% (P < .001 for all), and the physician's hand dose by between 27% (scattered radiation, P = .007) and 72% (direct radiation, P < .001). No significant difference was found in a comparison of the image noise with and that without ABM. CONCLUSION: ABM leads to significant dose reductions for both patients and personnel during CT fluoroscopy-guided thoracic interventions, without impairing image quality.

• Locally adaptive fuzzy pulmonary vessel segmentation in contrast enhanced CT data.

  Authors: Jens N. Kaftan, Annemarie Bakai, Marco Das, Til Aach

  Proceedings of the 2008 IEEE International Symposium on Biomedical Imaging: From Nano to Macro, Paris, France, May 14-17, 2008; 01/2008

• Pulmonary embolism: computer-aided detection at multidetector row spiral computed tomography.

  Authors: U Joseph Schoepf, Alex C Schneider, Marco Das, Susan A Wood, Jugesh I Cheema, Philip Costello

  Journal of thoracic imaging. 12/2007; 22(4):319-23.

  BACKGROUND: We aimed to evaluate the feasibility and performance of a computer-aided detection (CAD) tool for automated detection of segmental and subsegmental pulmonary emboli. METHODS: A CAD toolBACKGROUND: We aimed to evaluate the feasibility and performance of a computer-aided detection (CAD) tool for automated detection of segmental and subsegmental pulmonary emboli. METHODS: A CAD tool (ImageChecker CT, R2 Technology, Inc) for automated detection of pulmonary emboli was evaluated on multidetector-row CT studies of varying diagnostic quality in 23 patients (13 female, mean age 52 y) with pulmonary embolism (PE) and of 13 patients (all female, mean age 49 y) without PE. A collimation of 16 x 1 mm and a reconstructed section width of 1.25 mm had been used in each patient. The performance of the CAD tool for the detection of emboli in the segmental and subsegmental pulmonary arterial tree was assessed. Consensus reading of the same studies by 2 radiologists, with a third for adjudication, for the identification of segmental and subsegmental pulmonary emboli was used as the standard of reference. RESULTS: Consensus reading revealed 130 segmental pulmonary emboli and 107 subsegmental pulmonary emboli in the 23 patients with PE. All 23 patients with PE were correctly identified as having PE by the CAD system. In a vessel-by-vessel analysis, the sensitivity of the CAD algorithm was 92% (119/130) for the detection of segmental pulmonary emboli and 90% (92/107) for subsegmental pulmonary emboli. The overall specificity, positive predictive value (95% confidence interval) and negative predictive value (95% confidence interval) of the algorithm were 89.9%, 63.2% (57.9%-68.2%) and 97.7% (96.7%-98.4%), respectively. The average false positive rate of the CAD algorithm was 4.8 (range 1 to 9) false positive detection marks per case. CONCLUSION: CAD of segmental and subsegmental pulmonary emboli based on 1-mm multidetector-row CT studies is feasible. Application of CAD tools may improve the diagnostic accuracy and decrease the interpretation time of computed tomographic angiography for the detection of pulmonary emboli in the peripheral arterial tree and further enhance the acceptance of this test as the first line diagnostic modality for suspected PE.