Joachim E Wildberger

Publications of Joachim E Wildberger

• 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.

• Volumetric arterial enhancement fraction predicts tumor recurrence after hepatic radiofrequency ablation of liver metastases: initial results.

  Authors: Andreas H Mahnken, Ernst Klotz, Sara Schreiber, Philipp Bruners, Peter Isfort, Rolf W Günther, Joachim E Wildberger

  AJR. American journal of roentgenology. 05/2011; 196(5):W573-9.

  The objective of our study was to investigate the diagnostic value of the volumetric arterial enhancement fraction of the liver with color mapping for the early detection of tumor relapse afterThe objective of our study was to investigate the diagnostic value of the volumetric arterial enhancement fraction of the liver with color mapping for the early detection of tumor relapse after hepatic radiofrequency ablation (RFA). Fifty-three patients (24 men, 29 women; mean age ± SD, 65 ± 10 years) with a total of 215 liver metastases treated by RFA and a mean postinterventional follow-up period of 20 ± 15 (SD) months were included in this retrospective study. Quantitative arterial enhancement fraction color maps of the whole liver were computed from triple-phase contrast-enhanced MDCT images. Follow-up examinations served as the standard of reference. The diagnostic performance of the arterial enhancement fraction color maps to predict subsequent tumor occurrence before tumor was visible on routine multiphase CT images was evaluated. The mean arterial enhancement fraction of segments that developed metastases (62% ± 23%) was significantly higher than the mean of segments that did not develop metastases (39% ± 20%) (p < 0.0001). Receiver operating characteristic curve analysis revealed a probability of 77% for arterial enhancement fraction values to be higher in case of subsequent metastases as compared with liver parenchyma without tumor recurrence. The arterial enhancement fraction provides incremental value in the imaging surveillance for liver metastases after RFA. Arterial enhancement fraction color maps may be suited to predict tumor recurrence earlier than routine assessment using contrast-enhanced MDCT.

• 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.

• Flat panel computed tomography for non-invasive flow measurement: initial results in in-vitro studies.

  Authors: Andreas H Mahnken, Michael Grasruck, Bernhard Schmidt, Rolf W Günther, Joachim E Wildberger

  European radiology. 05/2008; 18(4):747-52.

  The purpose was to evaluate the feasibility of flat panel computed tomography (FPCT) for quantifying flow by analyzing contrast changes along the z-axis in an in-vitro setting. Contrast material wasThe purpose was to evaluate the feasibility of flat panel computed tomography (FPCT) for quantifying flow by analyzing contrast changes along the z-axis in an in-vitro setting. Contrast material was injected in a 3-mm silicone tube at flow rates of 0.1, 0.2, 0.5 and 1.0 ml/s using a commercially available injector pump. FPCT scans of this phantom were performed with a gantry rotation time of 3 s. From this data 41 phases were reconstructed at different points in time using a full and a partial gantry rotation. The differences in the contrast material arrival time and the contrast enhancement along the z-axis were recorded. Flow was calculated from this data and compared to the injector settings. There was a good agreement between the injector settings and the calculated flow rates, but agreement decreased with increasing flow rates. Absolute (percent) mean deviation between the injector settings and calculated flow values was 0.0230 +/- 0.0489ml/s (3.7243 +/- 4.7817%) using the full gantry rotation. Repeated-measurement ANOVA failed to show significant differences between the various techniques (p = 0.9726). FPCT allows for computing flow. While preliminary results indicate a good agreement at low flow rates, further studies are needed to assess this technique for higher flow rates.

• 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.

• Prospective evaluation of image quality with use of a patient image gallery for dose reduction in pediatric 16-MDCT.

  Authors: Dagmar Honnef, Joachim E Wildberger, Gabriel Haras, Christian Hohl, Gundula Staatz, Rolf W Günther, Andreas H Mahnken

  AJR. American journal of roentgenology. 03/2008; 190(2):467-73.

  OBJECTIVE: The purposes of this study were to evaluate prospective adjustment of dose settings in pediatric 16-MDCT by use of computer-simulated images in a patient image gallery and to compare theOBJECTIVE: The purposes of this study were to evaluate prospective adjustment of dose settings in pediatric 16-MDCT by use of computer-simulated images in a patient image gallery and to compare the dose reduction achieved with that of standard pediatric protocols. SUBJECTS AND METHODS: The image gallery consisted of images from weight-dependent sample examinations performed with varied simulated tube current-exposure time settings. The scanning parameters prospectively chosen on the basis of the image quality of the image gallery were used for 30 16-MDCT examinations (chest, n = 15; abdomen, n = 8; pelvis, n = 7) of 22 children (14 boys, eight girls; mean age, 6.8 +/- 5.8 years; mean body weight, 26.7 +/- 19.6 kg). Three blinded radiologists used a 4-point grading scale to rate the overall image quality of the image gallery and the 16-MDCT scans. Objective and subjective image quality was assessed for the simulated and actual CT scans. The concordance correlation coefficient (K) was determined. RESULTS: There was mainly moderate concordance with regard to objective (chest, K = 0.69; abdomen, K = 0.33; pelvis, K = 0.55) and subjective (chest soft-tissue window, kappa coefficient [kappa] = 0.00; chest lung window, kappa = 0.53; abdomen, kappa = 1.00; pelvis, kappa = 0.48) analysis of image gallery compared with actual 16-MDCT examinations. Compared with use of previous weight-adapted pediatric standard protocols, use of an image gallery resulted in further dose reduction for abdominal and pelvic CT but not for thoracic CT. CONCLUSION: A patient image gallery can be used as a basis for pediatric 16-MDCT examinations. The gallery provides a preexamination overview of expected image quality. Radiation exposure can be optimized with regard to patient weight and the image quality needed to answer the clinical question.

• Value of conventional chest radiography for the detection of coronary calcifications: Comparison with MSCT.

  Authors: Andreas H Mahnken, Berthold B Wein, Anil M Sinha, Rolf W Günther, Joachim E Wildberger

  European journal of radiology. 01/2008;

  PURPOSE: To evaluate if computed tomography (CT) coronary calcium scoring is needed after detection of coronary calcifications on conventional chest radiographs. MATERIALS AND METHODS: One hundredPURPOSE: To evaluate if computed tomography (CT) coronary calcium scoring is needed after detection of coronary calcifications on conventional chest radiographs. MATERIALS AND METHODS: One hundred and five patients (67 men; 57.2+/-12.8years) with suspected coronary artery disease underwent conventional chest radiography and non-enhanced, retrospectively ECG-gated multislice spiral CT (MSCT) of the heart (4mmx2.5mm, 120kV, 133mAs(eff.)). Chest radiographs were assessed independently by two radiologists. Detection of coronary calcifications was compared between both methods. Sensitivity, specificity, negative and positive predictive values, median, 25% and 75% percentiles for the detection of coronary calcifications were calculated. Receiver operating characteristics (ROC) analyses were computed. RESULTS: In 90 patients, MSCT revealed coronary calcifications. The mean coronary calcium score was 526.2 (0-4784.5). On chest radiographs, coronary calcifications were correctly detected in 46 (61) patients by observer 1 (observer 2). The corresponding sensitivity was 51.1% in observer 1 and 67.8% in observer 2. Median of detected coronary calcifications was 361.9 (426.4) for observer 1 (observer 2). Corresponding 25% und 75% percentiles were 109.6 (109.6) and 798.5 (898.5). The area under the ROC curve was 0.636 for observer 1 and 0.715 for observer 2. There was no correlation between image quality and the detection of coronary calcifications on plain film radiographs. CONCLUSION: As coronary calcifications of various extents are inconsistently detected on plain chest radiographs, CT calcium scoring may not be omitted even if coronary artery calcifications were detected on conventional chest radiographs.

• Assessment of global left and right ventricular function using dual-source computed tomography (DSCT) in comparison to MRI: an experimental study in a porcine model.

  Authors: Philipp Bruners, Andreas H Mahnken, Christian Knackstedt, Nadja Luhmann, Elmar Spüntrup, Marco Das, Christian Hohl, Joachim E Wildberger, Thomas Schmitz-Rode, Rolf W Günther, Georg Mühlenbruch

  Investigative radiology. 12/2007; 42(11):756-64.

  OBJECTIVE: We sought to evaluate the ability of retrospectively ECG-gated dual-source computed tomography (DSCT) to assess left (LV) and right ventricular (RV) functional parameters in comparison toOBJECTIVE: We sought to evaluate the ability of retrospectively ECG-gated dual-source computed tomography (DSCT) to assess left (LV) and right ventricular (RV) functional parameters in comparison to 1.5 T magnetic resonance imaging (MRI). MATERIALS AND METHODS: Ten domestic pigs (60 kg) underwent both contrast-enhanced cardiac DSCT and cardiac MRI using standardized examination protocols under general anesthesia. From manually drawn endocardial and epicardial contours, LV and RV end-systolic (ESV) and end-diastolic volume (EDV), stroke volume (SV), ejection fraction (EF), myocardial mass (MM), peak filling rate (PFR), peak ejection rate (PER), time to peak ejection (TPE), and time to peak filling (TPF) were calculated by means of dedicated analysis software. LV and RV functional parameters were analyzed using Bland-Altman plots, Student t test, and Pearson's correlation coefficient. RESULTS: Both left and right ESV and EDV, SV and EF determined with DSCT correlated well with MR imaging results (left, r = 0.98/0.92/0.82/0.98; right, r = 0.90/0.94/0.96/0.94). PER, PFR, TPE, TPF, and MM showed only a moderate to low correlation (left, r = 0.67/0.37/0.23/0.35/0.57; right, r = 0.78/0.69/0.12/0.11/0.44). PER and PFR were significantly underestimated by DSCT when compared with MRI. CONCLUSIONS: Retrospectively ECG-gated DSCT correctly depicts end-systole and can accurately determine LV and RV volumes, SV, and EF in comparison to MRI. DSCT showed a significant underestimation of PER and PFR in comparison to MRI.

• Late-phase MSCT in the different stages of myocardial infarction: animal experiments.

  Authors: Andreas H Mahnken, Philipp Bruners, Sylvia Kinzel, Marcus Katoh, Georg Mühlenbruch, Rolf W Günther, Joachim E Wildberger

  European radiology. 10/2007; 17(9):2310-7.

  The purpose of this study was to intraindividually evaluate myocardial late enhancement on multislice spiral computed tomography (MSCT) for the assessment of the different stages of myocardialThe purpose of this study was to intraindividually evaluate myocardial late enhancement on multislice spiral computed tomography (MSCT) for the assessment of the different stages of myocardial infarction (MI) in comparison with magnetic resonance (MR) imaging. Reperfused MI was successfully induced in seven pigs. Delayed enhancement MR imaging and late-phase MSCT were performed on day 0 as well as 7, 28 and 90 days after the procedure. The pigs were sacrificed, and 2,3,5-triphenyltetrazolin-chloride (TTC) staining was acquired. MI size was compared between the different imaging techniques and over time applying Bland-Altman plots and multivariate analysis with repeated measures. On day 0 the mean MI size was 23.7 +/- 11.8% of the left ventricular area on MSCT and 24.5 +/- 10.6% on MR imaging. On day 90 infarct sizes decreased significantly to 16.9 +/- 8.4% and 18.9 +/- 8.0%, respectively (P = 0.0019). On TTC staining the size of MI was 16.8 +/- 8.2%. Bland-Altman plots showed a good agreement between MSCT and MR imaging with mean deviations ranging from -3.4% to -1.9%. No significant difference between MSCT and MR imaging was found. Myocardial late enhancement on MSCT correlates well with delayed enhancement MR imaging during the different stages of MI and allows for reliable assessment of reperfused MI during acute, subacute and chronic stages.

• Molecular MR imaging of human thrombi in a swine model of pulmonary embolism using a fibrin-specific contrast agent.

  Authors: Elmar Spuentrup, Marcus Katoh, Arno Buecker, Bernd Fausten, Andrea J Wiethoff, Joachim E Wildberger, Patrick Haage, Edward C Parsons, Rene M Botnar, Philip B Graham, Manfred Vettelschoss, Rolf W Günther

  Investigative radiology. 09/2007; 42(8):586-95.

  OBJECTIVE: Molecular targeted MR imaging of human clots material in a model of pulmonary embolism using a fibrin-specific magnetic resonance imaging contrast agent (EP-2104R, EPIX Pharmaceuticals,OBJECTIVE: Molecular targeted MR imaging of human clots material in a model of pulmonary embolism using a fibrin-specific magnetic resonance imaging contrast agent (EP-2104R, EPIX Pharmaceuticals, Cambridge, MA). MATERIAL AND METHODS: Fresh ex vivo engineered thrombi (human blood) and human clots removed from patients were delivered in 11 swine. Molecular MR imaging with a 3D gradient-echo [3D fast field echo (3DFFE)] sequence and a navigator-gated and cardiac-triggered 3D inversion-recovery black-blood gradient-echo sequence (IR) was performed before thrombus delivery, after thrombus delivery but before contrast media application, and 2 hours after i.v. administration of 4 micromol/kg EP-2104R. MR images were analyzed by 2 investigators and contrast-to-noise ratio (CNR) was assessed. Thrombi were removed for assessment of gadolinium (Gd) concentration. RESULTS: Only after contrast media application were pulmonary emboli [freshly engineered thrombi (n = 23) and human clot material removed from patients (n = 25)] visualized as white foci on MR images. CNR was 13 +/- 3 (ex vivo engineered clot) and 22 +/- 9 (patient clot material) for the fast field echo (FFE)-sequence and 29 +/- 9 (ex vivo engineered clot) and 43 +/- 18 (patient clot material) for the IR-sequence, respectively. A high Gd concentration in the clots was found (82 +/- 43 microM for the freshly engineered and 247 +/- 44 microM for the clots removed from patients, respectively). CONCLUSIONS: EP-2104R allows for molecular MR imaging of human clot material in the pulmonary vessels of a swine model.

• Accuracy of automated volumetry of pulmonary nodules across different multislice CT scanners.

  Authors: Marco Das, Julia Ley-Zaporozhan, H A Gietema, Andre Czech, Georg Mühlenbruch, Andreas H Mahnken, Markus Katoh, Annemarie Bakai, Marcos Salganicoff, Stefan Diederich, Mathias Prokop, Hans-Ulrich Kauczor, Rolf W Günther, Joachim E Wildberger

  European radiology. 09/2007; 17(8):1979-84.

  The purpose of this study was to compare the accuracy of an automated volumetry software for phantom pulmonary nodules across various 16-slice multislice spiral CT (MSCT) scanners from differentThe purpose of this study was to compare the accuracy of an automated volumetry software for phantom pulmonary nodules across various 16-slice multislice spiral CT (MSCT) scanners from different vendors. A lung phantom containing five different nodule categories (intraparenchymal, around a vessel, vessel attached, pleural, and attached to the pleura), with each category comprised of 7-9 nodules (total, n = 40) of varying sizes (diameter 3-10 mm; volume 6.62 mm(3)-525 mm(3)), was scanned with four different 16-slice MSCT scanners (Siemens, GE, Philips, Toshiba). Routine and low-dose chest protocols with thin and thick collimations were applied. The data from all scanners were used for further analysis using a dedicated prototype volumetry software. Absolute percentage volume errors (APE) were calculated and compared. The mean APE for all nodules was 8.4% (+/-7.7%) for data acquired with the 16-slice Siemens scanner, 14.3% (+/-11.1%) for the GE scanner, 9.7% (+/-9.6%) for the Philips scanner and 7.5% (+/-7.2%) for the Toshiba scanner, respectively. The lowest APEs were found within the diameter size range of 5-10 mm and volumes >66 mm(3). Nodule volumetry is accurate with a reasonable volume error in data from different scanner vendors. This may have an important impact for intraindividual follow-up studies.

• Dual-source computed tomography for assessing cardiac function: a phantom study.

  Authors: Andreas H Mahnken, Herbert Bruder, Christoph Suess, Georg Mühlenbruch, Philipp Bruners, Christian Hohl, Rolf W Guenther, Joachim E Wildberger

  Investigative radiology. 08/2007; 42(7):491-8.

  PURPOSE: To investigate the influence of heart rate and temporal resolution on the assessment of global ventricular function with dual-source computed tomography (DSCT). MATERIALS AND METHODS: APURPOSE: To investigate the influence of heart rate and temporal resolution on the assessment of global ventricular function with dual-source computed tomography (DSCT). MATERIALS AND METHODS: A dynamic cardiac phantom was repeatedly scanned with a DSCT scanner applying a standardized scan protocol at different heart rates, ranging from 40 to 140 bpm. Images were reconstructed with monosegmental and bisegmental algorithms using data from a single source and from both sources. Ventricular volumes and ejection fraction (EF) were computed by semiautomated analysis. Results were compared with the phantom's real volumes. Interscan, intraobserver, and interobserver variability were calculated. RESULTS: For single-source data reconstruction temporal resolution was fixed to 165 milliseconds, whereas dual-source image reconstructions resulted in a temporal resolution of 83 milliseconds (monosegmental) and 67.7+/-14.2 milliseconds (bisegmental), respectively. In general, deviation from the phantom's real volumes was less with dual-source data reconstruction when compared with single-source data reconstruction. Comparing dual-source data reconstruction with single-source data reconstruction, the percent deviation from the phantom's real volumes for EF was 0.7% (monosegmental), 0.7% (bisegmental), and 4.3% (single source), respectively. There was no correlation between heart rate and EF for dual-source data reconstruction (r=-0.168; r=-0.157), whereas a relevant correlation was observed for single-source data reconstruction (r=-0.844). Interscan, intraobserver, and interobserver variability for EF were 1.4%, 0.9%, and 0.3%, respectively. CONCLUSIONS: DSCT allows reliable quantification of global ventricular function independent of the heart rate. Multisegmental image reconstruction is not needed for DSCT assessment of global ventricular function.

• Evaluation of automated attenuation-based tube current adaptation for coronary calcium scoring in MDCT in a cohort of 262 patients.

  Authors: Georg Mühlenbruch, Christian Hohl, Marco Das, Joachim E Wildberger, Christoph Suess, Ernst Klotz, Thomas Flohr, Ralf Koos, Christoph Thomas, Rolf W Günther, Andreas H Mahnken

  European radiology. 07/2007; 17(7):1850-7.

  The aim of our study was to evaluate attenuation-based tube current adaptation in coronary calcium scoring using ECG-gated multi-detector-row CT (MDCT). A total of 262 patients underwent non-enhancedThe aim of our study was to evaluate attenuation-based tube current adaptation in coronary calcium scoring using ECG-gated multi-detector-row CT (MDCT). A total of 262 patients underwent non-enhanced cardiac MDCT. Group 1 was scanned using a standard protocol with 120 kV and 150 mAs(eff). Groups 2-4 were scanned using an attenuation-based dose-adaptation template (CARE Dose) with different effective reference mAs settings (150, 180, 210 mAs(eff)). Body-mass index (BMI) and CT-dose index values were calculated for each patient. Image noise and subjective image quality were assessed. Regression analysis was performed, and the variation coefficient of image noise was determined. Compared to the standard scan protocol a dose reduction of 31.1% for group 2 and 20.1% for group 3 was observed. Measurement variation of image noise was smaller for the attenuation-based dose adaptation protocols (group 2-4) (16.2-17.1%) compared to the standard scan protocol (32.3%). Regression analysis of groups 2-4 showed better correlation with improved dose usage based on BMI (all P <or= 0.001). Median image quality was "excellent" in groups 2-4 and "good" in group 1. Automated attenuation-based tube current adaptation in coronary calcium scoring is technically feasible, can decrease patient dose, and reduces variation in image noise as a sign of improved dose usage.

• Automated volumetry of solid pulmonary nodules in a phantom: accuracy across different CT scanner technologies.

  Authors: Marco Das, Georg Mühlenbruch, Markus Katoh, Annemarie Bakai, Marcos Salganicoff, Sven Stanzel, Andreas H Mahnken, Rolf W Günther, Joachim E Wildberger

  Investigative radiology. 06/2007; 42(5):297-302.

  OBJECTIVES: The accuracy of automated volumetry for pulmonary nodules in a phantom using different CT scanner technologies from single-slice spiral CT (SSCT) to 64-slice multidetector-row CT (MDCT)OBJECTIVES: The accuracy of automated volumetry for pulmonary nodules in a phantom using different CT scanner technologies from single-slice spiral CT (SSCT) to 64-slice multidetector-row CT (MDCT) was compared. MATERIALS AND METHODS: A lung phantom with 5 different categories of pulmonary nodules was scanned using a single-slice spiral CT, a 4-slice MDCT, a 16-slice MDCT and a 64-slice MDCT. Each category comprised of 7-9 nodules each (total n = 40) with different known volumes. Standard dose and low dose protocols were performed using thin and thick collimation. Image data were reconstructed at the thinnest slice thickness. Data sets were analyzed with a dedicated volumetry software. Volumes of all nodules were calculated and compared. RESULTS: Mean absolute percentage error (APE) for all nodules was 8.65% (+/-7.29%) for the SSCT, 10.26% (+/-8.25%) for the 4-slice MDCT, 8.19% (+/-7.57%) for the 16-slice MDCT and 7.89% (+/-7.39%) for the 64-slice MDCT. There was statistically significant influence of the scanner type, protocol, anatomic location, and nodule volume on APE, but overall, APEs were comparable. CONCLUSION: Computer-aided volumetry showed accurate measurements in all tested scanner types. This finding has important implications for nodule assessment and follow-up.

• Quantitative prediction of contrast enhancement from test bolus data in cardiac MSCT.

  Authors: Andreas H Mahnken, Annabella Rauscher, Ernst Klotz, Georg Mühlenbruch, Marco Das, Rolf W Günther, Joachim E Wildberger

  European radiology. 06/2007; 17(5):1310-9.

  The purpose of this study was to evaluate a new algorithm for the prediction of contrast enhancement from test bolus data in cardiac multislice spiral computed tomography (MSCT). An algorithm for theThe purpose of this study was to evaluate a new algorithm for the prediction of contrast enhancement from test bolus data in cardiac multislice spiral computed tomography (MSCT). An algorithm for the prediction of contrast enhancement using test bolus data was developed. A total of 30 consecutive patients (15 male, 69.5 +/- 9.6 years) underwent cardiac MSCT (12 x 0.75 mm, 120 kV, 500 mAs(eff.)) with a biphasic contrast material injection protocol. Contrast timing was derived from a standard 20 ml test bolus injection. Based on the test bolus time attenuation curves, expected enhancement values were computed for the ascending and descending aorta and the pulmonary trunk and compared with measured data from the cardiac CT scan. At the level of the test bolus measurement in the ascending aorta, the corresponding attenuation values were 309.4 +/- 49.6 Hounsfield Units (HU) for the predicted and 285.6 +/- 42.6 HU for the measured attenuation, respectively. The mean deviation between predicted and measured CT values was 32.8 +/- 48.2 HU (upper and lower limits of agreement 101.4/-53.8 HU), indicating a slight systematic tendency for overestimation. For 80% of the patients the prediction error was less than 50 HU. Prediction of contrast enhancement in cardiac MSCT from test bolus data is feasible with a relatively small mean deviation; 80% of the predictions were within a range that might be acceptable for routine clinical application.

• Asbestos Surveillance Program Aachen (ASPA): initial results from baseline screening for lung cancer in asbestos-exposed high-risk individuals using low-dose multidetector-row CT.

  Authors: Marco Das, Georg Mühlenbruch, Andreas H Mahnken, K G Hering, H Sirbu, W Zschiesche, Lars Knoll, Michael K Felten, Thomas Kraus, Rolf W Günther, Joachim E Wildberger

  European radiology. 06/2007; 17(5):1193-9.

  The purpose of this study was to assess the prevalence of lung cancer in a high-risk asbestos-exposed cohort using low-dose MDCT. Of a population of 5,389 former power-plant workers, 316 wereThe purpose of this study was to assess the prevalence of lung cancer in a high-risk asbestos-exposed cohort using low-dose MDCT. Of a population of 5,389 former power-plant workers, 316 were characterized as individuals at highest risk for lung cancer according to a lung-cancer risk model including age, asbestos exposure and smoking habits. Of these 316, 187 (mean age: 66.6 years) individuals were included in a prospective trial. Mean asbestos exposure time was 29.65 years and 89% were smokers. Screening was performed on a 16-slice MDCT (Siemens) with low-dose technique (10/20 mAs(eff.); 1 mm/0.5 mm increment). In addition to soft copy PACS reading analysis on a workstation with a dedicated lung analysis software (LungCARE; Siemens) was performed. One strongly suspicious mass and eight cases of histologically proven lung cancer were found plus 491 additional pulmonary nodules (average volume: 40.72 ml, average diameter 4.62 mm). Asbestos-related changes (pleural plaques, fibrosis) were visible in 80 individuals. Lung cancer screening in this high-risk cohort showed a prevalence of lung cancer of 4.28% (8/187) at baseline screening with an additional large number of indeterminate pulmonary nodules. Low-dose MDCT proved to be feasible in this highly selected population.

• Cardiac CT: coronary arteries and beyond.

  Authors: Andreas H Mahnken, Georg Mühlenbruch, Rolf W Günther, Joachim E Wildberger

  European radiology. 05/2007; 17(4):994-1008.

  Multi-detector-row computed tomography (MDCT) has emerged as a rapidly developing method for non-invasive imaging of the heart. An understanding of ECG synchronization, contrast materialMulti-detector-row computed tomography (MDCT) has emerged as a rapidly developing method for non-invasive imaging of the heart. An understanding of ECG synchronization, contrast material administration, patient preparation and image post-processing is needed to optimize image quality. The basic technical principles and essentials of these technical basics are described here. Correctly applied cardiac MDCT allows imaging of the coronary arteries including coronary anatomy and stenosis detection. The same is true for evaluation of coronary artery bypass grafts and, to some extent, coronary artery stents. While quantification of total calcified plaque burden has been long established, coronary MDCT allows assessing plaque morphology and constitution. Recent approaches go beyond the coronaries and include evaluation of left ventricular function at rest and myocardial viability. In combination with experimental approaches for assessing aortic valve function and myocardial perfusion imaging, cardiac MDCT offers the potential for a comprehensive examination of the heart using a single breath-hold examination.

• MDCT detection of mitral valve calcification: prevalence and clinical relevance compared with echocardiography.

  Authors: Andreas H Mahnken, Georg Mühlenbruch, Marco Das, Joachim E Wildberger, Harald P Kühl, Rolf W Günther, Malte Kelm, Ralf Koos

  AJR. American journal of roentgenology. 05/2007; 188(5):1264-9.

  OBJECTIVE: The purpose of this study was to analyze the prevalence and clinical significance of mitral valve calcification incidentally detected on chest CT scans in comparison with echocardiography.OBJECTIVE: The purpose of this study was to analyze the prevalence and clinical significance of mitral valve calcification incidentally detected on chest CT scans in comparison with echocardiography. MATERIALS AND METHODS: The data of 390 patients (227 men and 163 women; mean age, 62.4 +/- 12.2 years) who underwent MDCT of the chest and echocardiography were retrospectively evaluated. On MDCT, mitral valve leaflet and annulus calcification were visually graded on a scale of 0-3, with grade 0 denoting no calcification and grade 3 indicating severe calcification. CT findings were correlated with hemodynamic data obtained at echocardiography. Unpaired Student's t tests, chi-square analysis, and a weighted-kappa test were used to compare results. RESULTS: In 32 (8.2%) of 390 patients, chest MDCT revealed mitral valve leaflet calcification. Fifteen of these patients (15/390, 3.8%) presented with mitral valve stenosis. Excellent agreement (kappa = 0.882) was seen between the presence of mitral valve calcification on MDCT and echocardiographically proven mitral valve sclerosis. Mitral valve leaflet calcification on MDCT and the severity of mitral valve disease on echocardiography showed a substantial agreement (kappa = 0.730). A significant relationship was seen between the degree of mitral valve calcification on MDCT and the echocardiographically determined severity of mitral valve disease (no sclerosis vs mitral sclerosis vs mitral stenosis; p < 0.0001). CONCLUSION: Mitral valve leaflet calcification on MDCT indicates mitral valve sclerosis or stenosis. Thus, patients presenting with incidentally detected mitral valve leaflet calcification on chest CT may benefit from a functional assessment with echocardiography.

• Active breathing control (ABC): determination and reduction of breathing-induced organ motion in the chest.

  Authors: Bernd Gagel, Cengiz Demirel, Aline Kientopf, Michael Pinkawa, Marc Piroth, Sven Stanzel, Christian Breuer, Branka Asadpour, Thomas Jansen, Richard Holy, Joachim E Wildberger, Michael J Eble

  International journal of radiation oncology, biology, physics. 04/2007; 67(3):742-9.

  PURPOSE: Extensive radiotherapy volumes for tumors of the chest are partly caused by interfractional organ motion. We evaluated the feasibility of respiratory observation tools using the activePURPOSE: Extensive radiotherapy volumes for tumors of the chest are partly caused by interfractional organ motion. We evaluated the feasibility of respiratory observation tools using the active breathing control (ABC) system and the effect on breathing cycle regularity and reproducibility. METHODS AND MATERIALS: Thirty-six patients with unresectable tumors of the chest were selected for evaluation of the ABC system. Computed tomography scans were performed at various respiratory phases starting at the same couch position without patient movement. Threshold levels were set at minimum and maximum volume during normal breathing cycles and at a volume defined as shallow breathing, reflecting the subjective maximal tolerable reduction of breath volume. To evaluate the extent of organ movement, 13 landmarks were considering using commercial software for image coregistration. In 4 patients, second examinations were performed during therapy. RESULTS: Investigating the differences in a normal breathing cycle versus shallow breathing, a statistically significant reduction of respiratory motion in the upper, middle, and lower regions of the chest could be detected, representing potential movement reduction achieved through reduced breath volume. Evaluating interfraction reproducibility, the mean displacement ranged between 0.24 mm (chest wall/tracheal bifurcation) to 3.5 mm (diaphragm) for expiration and shallow breathing and 0.24 mm (chest wall) to 5.25 mm (diaphragm) for normal inspiration. CONCLUSIONS: By modifying regularity of the respiratory cycle through reduction of breath volume, a significant and reproducible reduction of chest and diaphragm motion is possible, enabling reduction of treatment planning margins.

• Low tube voltage improves computed tomography imaging of delayed myocardial contrast enhancement in an experimental acute myocardial infarction model.

  Authors: Andreas H Mahnken, Philipp Bruners, Georg Mühlenbruch, Melanie Emmerich, Christian Hohl, Rolf W Günther, Joachim E Wildberger

  Investigative radiology. 03/2007; 42(2):123-9.

  OBJECTIVE: We sought to evaluate the influence of tube voltage on the visualization of acute myocardial infarction (MI) in cardiac multislice spiral computed tomography (MSCT). MATERIALS AND METHODS:OBJECTIVE: We sought to evaluate the influence of tube voltage on the visualization of acute myocardial infarction (MI) in cardiac multislice spiral computed tomography (MSCT). MATERIALS AND METHODS: Acute MI was induced in 12 domestic pigs by a 45-minute balloon occlusion of the left anterior descending artery. Delayed enhancement magnetic resonance imaging was performed 15 minutes after the injection of 0.2 mmol/kg Gd-DTPA. On the same day, retrospectively ECG-gated MSCT was performed at 120, 100, and 80 kV (16x0.75mm, 550mAseff.) 15 minutes after the injection of 140 mL of iopromide (1 g/iodine/kg). The pigs were killed and the hearts were excised and stained with 2,3,5-triphenyltetrazolium chloride. The area of acute MI, contrast-to-noise ratio (CNR), and percent signal difference were compared among the different imaging techniques by applying Bland-Altman plots and 2-way analysis of variance. RESULTS: On MSCT at 120, 100, and 80 kV, the respective mean acute MI sizes were 18.4+/-11.4%, 19.3+/-11.5%, and 20.5+/-11.6%. The mean MI sizes were 20.8+/-12.2% and 20.1+/-12.4% on magnetic resonance imaging and 2,3,5-triphenyltetrazolium chloride staining. Analysis of variance did not show any statistically significant differences between the different techniques with respect to the size of acute MI (P=0.9880). Comparing the different kV settings on MSCT, the highest percent signal difference (74.7+/-12.1%) and the highest CNR (6.7+/-1.8) between infarcted and healthy remote myocardium were achieved at 80 kV. CONCLUSIONS: When compared with routine scan protocols, low tube voltage MSCT allows for the assessment of the MI size with an improved CNR and contrast resolution. This technique appears to be advantageous for assessing myocardial viability from contrast enhanced late-phase MSCT.