Ralf W Bauer

Publications of Ralf W Bauer

• High-pitch Dual-source Computed Tomography Pulmonary Angiography in Freely Breathing Patients.

  Authors: Ralf W Bauer, Boris Schell, Martin Beeres, Julian L Wichmann, Boris Bodelle, Thomas J Vogl, Josef Matthias Kerl

  Journal of thoracic imaging. 04/2012;

  PURPOSE:: To investigate pulmonary arterial (PA) enhancement, image noise, and artifacts related to breathing and heart motion in patients with suspected pulmonary embolism. MATERIALS AND METHODS::PURPOSE:: To investigate pulmonary arterial (PA) enhancement, image noise, and artifacts related to breathing and heart motion in patients with suspected pulmonary embolism. MATERIALS AND METHODS:: Seventy-six consecutive patients underwent computed tomographic pulmonary angiography (CTPA) in dual-source high-pitch mode (pitch 3.0, 100 kV, 180 mAs, 50 mL contrast material) without breathing commands. PA enhancement, image noise, signal to noise ratio, overall image quality, incidence of total or partial interruption of the contrast column in the PAs, and heart motion-related and breathing-related artifacts of the diaphragm and pulmonary structures were recorded. RESULTS:: Mean central and peripheral PA attenuation was 404±104 and 453±119 HU; mean image noise was 11±2 HU; mean examination time was 0.67±0.09 s; and mean dose-length product was 142±31 mGy cm. There were no motion artifacts of the diaphragm or pulmonary vessels related to breathing or heart motion. There was no case of partial or total interruption of the contrast column in the PA tree. No examination was rated nondiagnostic. CONCLUSIONS:: High-pitch dual-source CTPA in freely breathing patients effectively produces images that are free of artifacts related to breathing and cardiac motion. Hence, Valsalva-related artifacts can be eliminated using this technique.

• MR-based Thermometry of Laser Induced Thermotherapy: Temperature Accuracy and Temporal Resolution In vitro at 0.2 and 1.5 T Magnetic Field Strengths.

  Authors: Thomas J Vogl, Frank Huebner, Nagy N N Naguib, Ralf W Bauer, Martin G Mack, Nour-Eldin A Nour-Eldin, Dirk Meister

  Lasers in surgery and medicine. 03/2012; 44(3):257-65.

  To evaluate MR-thermometry using fast MR sequences for laser induced interstitial thermotherapy (LITT) at 0.2 and 1.5 T systems. In-vitro experiments were performed using Agarose gel mixture andTo evaluate MR-thermometry using fast MR sequences for laser induced interstitial thermotherapy (LITT) at 0.2 and 1.5 T systems. In-vitro experiments were performed using Agarose gel mixture and lobes of porcine liver. MR-thermometry was performed by means of longitudinal relaxation time (T1) and proton resonance frequency shift (PRF) methods under acquisition of amplitude and phase shift images. Four different sequences were used for T1 thermometry: A gradient-echo (GRE), a True Fast Imaging with Steady Precession (TRUFI), a Saturation Recovery Turbo-FLASH (SRTF), and an Inversion Recovery Turbo-FLASH (IRTF) sequence (FLASH-Fast Low Angle Shot). PRF was measured with four sequences: Two fast-spoiled GRE sequences (one as WIP sequence), a Turbo-FLASH (TFL) sequence (WIP sequence), and a multiecho-TrueFISP sequence. Temperature was controlled and verified using a fiber-optic Luxtron device. The temperature was correlated with the MR measurement. All sequences showed a good linear correlation R(2)  = 0.97-0.99 between the measured temperature and the MR-thermometry measurements. The only exception was the TRUFI sequence in the Agarose phantom that showed a non-linear calibration curve R(2)  = 0.39-0.67. At 1.5 T, the Agarose experiments revealed similar temperature accuracies of 4-6°C for all sequences excluding TRUFI. During experiments with the liver, the PRF sequences showed better performance than the T1, with accuracies of 5-12°C, contrary to the T1 sequences at 14-18°C. The accuracy of the Siemens PRF-FLASH sequence was 5.1°C. At 0.2 T, the Agarose experiments provided the highest accuracy of 3.3°C for PRF measurement. At the liver experiments the T1 sequences SRTF and FLASH revealed the best accuracies at 6.4 and 7.0°C. The accuracy and speed of MR temperature measurements are sufficient for controlling the temperature-based tumor destruction. For 0.2 T systems SRTF and FLASH sequences are recommended. For 1.5 T systems SRTF and FLASH are the most accurate. Lasers Surg. Med. 44:257-265, 2012. © 2012 Wiley Periodicals, Inc.

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• Correlation of left ventricular wall thickness, heart mass, serological parameters and late gadolinium enhancement in cardiovascular magnetic resonance imaging of myocardial inflammation in an experimental animal model of autoimmune myocarditis.

  Authors: Wolfgang Kromen, Huedayi Korkusuz, Yuecel Korkusuz, Philip Esters, Ralf W Bauer, Frank Huebner, Sebastian Lindemayr, Thomas J Vogl

  The international journal of cardiovascular imaging. 02/2012;

  For a definitive diagnosis of myocarditis, different strategies like analysis of late gadolinium enhancement (LGE) in cardiovascular magnetic resonance imaging (CMR) up to invasive endomyocardialFor a definitive diagnosis of myocarditis, different strategies like analysis of late gadolinium enhancement (LGE) in cardiovascular magnetic resonance imaging (CMR) up to invasive endomyocardial biopsy have been applied. The objective of the study was to investigate inflammatory changes like left ventricular wall thickening and increase of ventricular mass and to quantitatively analyse their correlation with extent and localisation of myocardial damage in CMR and with subsequent changes of serological markers in an animal model of an experimental autoimmune myocarditis (EAM). In the current study, an EAM was induced in 10 male Lewis rats, 10 rats served as control. On day 21, animals were examined with four CMR protocols to assess the extent of LGE in a 12 segment model of the rat heart. Left myocardial wall thickness and mass and histological grade of inflammation were measured to determine localisation and severity of the induced myocarditis. Depending on the CMR sequence, LGE was mostly found in the left anterior (9.6%) and left lateral (8.7%) myocardial wall segments. Wall thickness correlated with the LGE area in CMR imaging and the histopathological severity of myocarditis for the left lateral myocardial wall segment. In a similar way, the heart mass correlated to the extent of LGE for the left lateral segment. We conclude that in our animal model left ventricular wall thickness and mass reflect the severity of myocardial changes in myocarditis and that the EAM rat model is well suited for further investigations of myocarditis.

• Image-quality perception as a function of dose in digital radiography.

  Authors: Thomas Lehnert, Nagy N N Naguib, Huedayi Korkusuz, Ralf W Bauer, J Matthias Kerl, Martin G Mack, Thomas J Vogl

  AJR. American journal of roentgenology. 12/2011; 197(6):1399-403.

  The purpose of this article is to determine the degree to which the skin entrance dose could be lowered, by adjusting exposure parameters and filtration, and the subsequent effect on readers'The purpose of this article is to determine the degree to which the skin entrance dose could be lowered, by adjusting exposure parameters and filtration, and the subsequent effect on readers' confidence levels of digital radiographs. The study was prospectively performed on a cadaver. Digital radiographs of bones were evaluated and scored on a 9-point scale separately by four radiologists who were blinded to the types of filtration and doses used. The study entailed three phases: phase 1, random dose and filter; phase 2, fixed filter and varying radiation doses (100%, 75%, 50%, and 25% of the standard recommended dose); and phase 3, fixed dose and varying filtration (no filtration, aluminum filter, and aluminum-copper filter). Skin entrance dose was measured using a dosimeter placed on the skin. Differences in scores were tested using a Friedman test. The mean scores given to images with 100%, 75%, 50%, and 25% of the recommended standard dose were 6.18, 6.1, 5.11, and 4.07, respectively. No significant difference was noted between 100%- and 75%-dose images (p = 0.1). A significant difference (p < 0.0001) was noted when we compared the 100%- and 75%-dose images with the 50%- and 25%-dose images. The mean scores given for no filtration, aluminum filtration, and aluminum-copper filtration were 5.67, 5.43, and 5.18, respectively. No significant difference between no filtration and aluminum filtration (p = 0.411) was noted. A significant difference was detected between no filtration and aluminum-copper filtration (p = 0.012). The combination of an aluminum filter and a 75% standard dose achieved a 31.1% reduction in skin entrance dose. It is possible to achieve a 31.1% reduction in skin entrance dose for imaging bony structures by using 75% of the standard dose and aluminum filtration without significantly affecting image quality.

• Intravenous contrast material administration at high-pitch dual-source CT pulmonary angiography: Test bolus versus bolus-tracking technique.

  Authors: J Matthias Kerl, Thomas Lehnert, Boris Schell, Boris Bodelle, Martin Beeres, Volkmar Jacobi, Thomas J Vogl, Ralf W Bauer

  European journal of radiology. 10/2011;

  PURPOSE: To compare test bolus and bolus tracking for the determination of scan delay of high-pitch dual-source CT pulmonary angiography in patients with suspected pulmonary embolism using 50ml ofPURPOSE: To compare test bolus and bolus tracking for the determination of scan delay of high-pitch dual-source CT pulmonary angiography in patients with suspected pulmonary embolism using 50ml of contrast material. MATERIALS AND METHODS: Data of 80 consecutive patients referred for CT pulmonary angiography were evaluated. All scans were performed on a 128-channel dual-source CT scanner with a high-pitch protocol (pitch 3.0, 100kV, 180mAs). Contrast enhancement was achieved by injecting 50ml of iomeprol followed by a saline chaser of 50ml injected at a rate of 4ml/s. The scan delay was determined using either the test bolus (n=40) or bolus tracking (n=40) technique. Test bolus required another 15ml CM to determine time to peak enhancement of the contrast bolus within the pulmonary trunk. Attenuation profiles in the pulmonary trunk and on segmental level as well as in the ascending aorta were measured to evaluate the timing techniques. Additionally, overall image quality was evaluated. RESULTS: In all patients an adequate and homogeneous contrast enhancement of more than 250HU was achieved in the pulmonary arteries. No statistically significant difference between test bolus and bolus tracking was found regarding attenuation of the pulmonary arteries or overall image quality. However, using bolus tracking 15ml CM less was injected. CONCLUSION: A homogeneous opacification of the pulmonary arteries and sufficient image quality can be achieved with both the bolus tracking and test bolus techniques with significant lower contrast doses compared to conventional contrast material injection protocols.

• High-pitch dual-source CT angiography of the whole aorta without ECG synchronisation: initial experience.

  Authors: Martin Beeres, Boris Schell, Aristidis Mastragelopoulos, Eva Herrmann, Josef Matthias Kerl, Tatjana Gruber-Rouh, Clara Lee, Petra Siebenhandl, Boris Bodelle, Stephan Zangos, Thomas J Vogl, Volkmar Jacobi, Ralf W Bauer

  European radiology. 09/2011; 22(1):129-37.

  To investigate the feasibility, image quality and radiation dose for high-pitch dual-source CT angiography (CTA) of the whole aorta without ECG synchronisation. Each group of 40 patients underwentTo investigate the feasibility, image quality and radiation dose for high-pitch dual-source CT angiography (CTA) of the whole aorta without ECG synchronisation. Each group of 40 patients underwent CTA either on a 16-slice (group 1) or dual-source CT device with conventional single-source (group 2) or high-pitch mode with a pitch of 3.0 (group 3). The presence of motion or stair-step artefacts of the thoracic aorta was independently assessed by two readers. Subjective and objective scoring of motion and artefacts were significantly reduced in the high-pitch examination protocol (p < 0.05). The imaging length was not significantly different, but the imaging time was significantly (p < 0.001) shorter in the high-pitch group (12.2 vs. 7.4 vs. 1.7 s for groups 1, 2 and 3). The ascending aorta and the coronary ostia were reliably evaluable in all patients of group 3 without motion artefacts as well. High-pitch dual-source CT angiography of the whole aorta is feasible in unselected patients. As a significant advantage over regular pitch protocols, motion-free imaging of the aorta is possible without ECG synchronisation. Thus, this CT mode bears potential to become a standard CT protocol before trans-catheter aortic valve implantation (TAVI).

• Dual energy CT for the assessment of reperfused chronic infarction - a feasibility study in a porcine model.

  Authors: J Matthias Kerl, Simon Deseive, Christa Tandi, Christina Kaiser, Mattias Kettner, Huedayi Korkusuz, Ralf Lehmann, Christopher Herzog, U Joseph Schoepf, Thomas J Vogl, Ralf W Bauer

  Acta radiologica (Stockholm, Sweden : 1987). 08/2011; 52(8):834-9.

  BACKROUND: Detection of myocardial infarction has been the focus of considerable research over the past few decades. Recently developed dual source computed tomography (DSCT) scanners with dualBACKROUND: Detection of myocardial infarction has been the focus of considerable research over the past few decades. Recently developed dual source computed tomography (DSCT) scanners with dual energy mode have been used to detect myocardial infarction, but the studies on this topic are few. To evaluate the feasibility and performance of dual energy CT (DECT) during arterial phase in coronary CT angiography for the detection of chronic infarction compared with late enhancement MRI (LE-MRI) and histopathology in a porcine model of reperfused myocardial infarction. Myocardial infarctions were induced by 30 min occlusion of the proximal left anterior descending coronary artery in eight minipigs. DECT, post-contrast LE-MRI and histopathology were performed 60 days after infarct induction. The CT scan was performed in dual energy mode using a dedicated protocol. Myocardial iodine distribution was superimposed as color maps on grey scale multiplanar reformats of the heart. Two radiologists in consensus interpreted all imaging studies for presence of gadolinium uptake at LE-MRI reduced iodine content at DECT and hypoenhanced areas in the initial 100 kV coronary CT angiography images that were acquired during the DECT-acquisition. Results were compared with histopathology. Based on evaluable segments, DECT showed a sensitivity and specificity of 0.72 and 0.88; LE-MRI showed a sensitivity and specificity of 0.78 and 0.92; and the 100 kV data-set of the DECT scan showed a sensitivity and specificity of 0.60 and 0.93, respectively, for the detection of histological proved ischemia. DECT during arterial phase coronary CT angiography, which is ordinarily used for coronary artery evaluation, is feasible for the detection of a chronic reperfused myocardial infarction.

• Estimation and comparison of effective dose (E) in standard chest CT by organ dose measurements and dose-length-product methods and assessment of the influence of CT tube potential (energy dependency) on effective dose in a dual-source CT.

  Authors: Jijo Paul, Rosemarie Banckwitz, Bernhard Krauss, Thomas J Vogl, Werner Maentele, Ralf W Bauer

  European journal of radiology. 06/2011;

  PURPOSE: To determine effective dose (E) during standard chest CT using an organ dose-based and a dose-length-product-based (DLP) approach for four different scan protocols including high-pitch andPURPOSE: To determine effective dose (E) during standard chest CT using an organ dose-based and a dose-length-product-based (DLP) approach for four different scan protocols including high-pitch and dual-energy in a dual-source CT scanner of the second generation. MATERIALS AND METHODS: Organ doses were measured with thermo luminescence dosimeters (TLD) in an anthropomorphic male adult phantom. Further, DLP-based dose estimates were performed by using the standard 0.014mSv/mGycm conversion coefficient k. Examinations were performed on a dual-source CT system (Somatom Definition Flash, Siemens). Four scan protocols were investigated: (1) single-source 120kV, (2) single-source 100kV, (3) high-pitch 120kV, and (4) dual-energy with 100/Sn140kV with equivalent CTDIvol and no automated tube current modulation. E was then determined following recommendations of ICRP publication 103 and 60 and specific k values were derived. RESULTS: DLP-based estimates differed by 4.5-16.56% and 5.2-15.8% relatively to ICRP 60 and 103, respectively. The derived k factors calculated from TLD measurements were 0.0148, 0.015, 0.0166, and 0.0148 for protocol 1, 2, 3 and 4, respectively. Effective dose estimations by ICRP 103 and 60 for single-energy and dual-energy protocols show a difference of less than 0.04mSv. CONCLUSION: Estimates of E based on DLP work equally well for single-energy, high-pitch and dual-energy CT examinations. The tube potential definitely affects effective dose in a substantial way. Effective dose estimations by ICRP 103 and 60 for both single-energy and dual-energy examinations differ not more than 0.04mSv.

• Evaluation of heavily calcified vessels with coronary CT angiography: comparison of iterative and filtered back projection image reconstruction.

  Authors: Matthias Renker, John W Nance, U Joseph Schoepf, Terrence X O'Brien, Peter L Zwerner, Mathias Meyer, J Matthias Kerl, Ralf W Bauer, Christian Fink, Thomas J Vogl, Thomas Henzler

  Radiology. 06/2011; 260(2):390-9.

  To prospectively compare traditional filtered back projection (FBP) and iterative image reconstruction for the evaluation of heavily calcified arteries with coronary computed tomography (CT)To prospectively compare traditional filtered back projection (FBP) and iterative image reconstruction for the evaluation of heavily calcified arteries with coronary computed tomography (CT) angiography. The study had institutional review board approval and was HIPAA compliant. Written informed consent was obtained from all patients. Fifty-five consecutive patients (35 men, 20 women; mean age, 58 years ± 12 [standard deviation]) with Agatston scores of at least 400 underwent coronary CT angiography and cardiac catheterization. Image data were reconstructed with both FBP and iterative reconstruction techniques with corresponding cardiac algorithms. Image noise and subjective image quality were compared. To objectively assess the effect of FBP and iterative reconstruction on blooming artifacts, volumes of circumscribed calcifications were measured with dedicated volume analysis software. FBP and iterative reconstruction series were independently evaluated for coronary artery stenosis greater than 50%, and their diagnostic accuracy was compared, with cardiac catheterization as the reference standard. Statistical analyses included paired t tests, Kruskal-Wallis analysis of variance, and a modified McNemar test. Image noise measured significantly lower (P = .011-.035) with iterative reconstruction instead of FBP. Image quality was rated significantly higher (P = .031 and .042) with iterative reconstruction series than with FBP. Calcification volumes measured significantly lower (P = .019 and .026) with iterative reconstruction (44.3 mm(3) ± 64.7 and 46.2 mm(3) ± 68.8) than with FBP (54.5 mm(3) ± 69.5 and 56.3 mm(3) ± 72.5). Iterative reconstruction significantly improved some measures of per-segment diagnostic accuracy of coronary CT angiography for the detection of significant stenosis compared with FBP (accuracy: 95.9% vs 91.8%, P = .0001; specificity: 95.8% vs 91.2%, P = .0001; positive predictive value: 76.9% vs 61.1%, P = .0001). Iterative reconstruction reduces image noise and blooming artifacts from calcifications, leading to improved diagnostic accuracy of coronary CT angiography in patients with heavily calcified coronary arteries.

• Effect of contrast material on image noise and radiation dose in adult chest computed tomography using automatic exposure control: a comparative study between 16-, 64- and 128-slice CT.

  Authors: Jijo Paul, Boris Schell, J Matthias Kerl, Werner Maentele, Thomas J Vogl, Ralf W Bauer

  European journal of radiology. 06/2011; 79(2):e128-32.

  To determine the difference in radiation dose between non-enhanced (NECT) and contrast-enhanced (CECT) chest CT examinations contributed by contrast material with different scanner generations withTo determine the difference in radiation dose between non-enhanced (NECT) and contrast-enhanced (CECT) chest CT examinations contributed by contrast material with different scanner generations with automatic exposure control (AEC). Each 42 adult patients received a NECT and CECT of the chest in one session on a 16-, 64- or 128-slice CT scanner with the same scan protocol settings. However, AEC technology (Care Dose 4D, Siemens) underwent upgrades in each of the three scanner generations. DLP, CTDIvol and image noise were compared. Although absolute differences in image noise were very small and ranged between 10 and 13 HU for NECT and CECT in median, the differences in image noise and dose (DLP: 16-slice:+2.8%; 64-slice:+3.9%; 128-slice:+5.6%) between NECT and CECT were statistically significant in all groups. Image noise and dose parameters were significantly lower in the most recent 128-slice CT generation for both NECT and CECT (DLP: 16-slice:+35.5-39.2%; 64-slice:+6.8-8.5%). The presence of contrast material lead to an increase in dose for chest examinations in three CT generations with AEC. Although image noise values were significantly higher for CECT, the absolute differences were in a range of 3 HU. This can be regarded as negligible, thus indicating that AEC is able to fulfill its purpose of maintaining image quality. However, technological developments lead to a significant reduction of dose and image noise with the latest CT generation.

• Dose and image quality at CT pulmonary angiography-comparison of first and second generation dual-energy CT and 64-slice CT.

  Authors: Ralf W Bauer, Sebastian Kramer, Matthias Renker, Boris Schell, Maya Christina Larson, Martin Beeres, Thomas Lehnert, Volkmar Jacobi, Thomas J Vogl, Josef Matthias Kerl

  European radiology. 05/2011; 21(10):2139-47.

  To compare dose and image quality of 64-slice, first and second generation dual-energy CT (DECT) for CT pulmonary angiography (CTPA). Totally 120 patients, 30 in each group, underwent CTPA on a firstTo compare dose and image quality of 64-slice, first and second generation dual-energy CT (DECT) for CT pulmonary angiography (CTPA). Totally 120 patients, 30 in each group, underwent CTPA on a first generation (group 1: single-energy, 120 kV/145 mAs; group 2: DE, 140/80 kV, 70/350 mAs) or second generation dual-source DECT device (group 3: DE, 100/Sn140 kV, 120/102 mAs; group 4: DE, 80/Sn140 kV, 202/86 mAs). CTDIvol, DLP, background noise (BN), thorax diameter and attenuation in the pulmonary trunk were compared. Thorax diameter and attenuation in the pulmonary trunk did not differ significantly (p > 0.4 and >0.19) between the groups. Mean CTDIvol and DLP were significantly lower (p < 0.003) in group 4 (6.2 ± 1.6 mGy/170 ± 41 mGycm) compared to group 1 (8.5 ± 2.6 mGy/235 ± 117 mGycm), group 2 (9.2 ± 3.3 mGy/224 ± 122 mGycm) and group 3 (8.7 ± 2.8 mGy/246 ± 86 mGycm). BN was significantly lower (p < 0.0001) in group 4 (12 ± 3 HU) and group 1 (13 ± 6 HU) compared to group 3 and 2 (16 ± 6 HU and 23 ± 9). The use of second generation DECT in 80/Sn140 kV configuration allows for significant dose reduction with image quality similar to 120 kV CTPA.

• Dual-Energy CT of Head and Neck Cancer: Average Weighting of Low- and High-Voltage Acquisitions to Improve Lesion Delineation and Image Quality-Initial Clinical Experience.

  Authors: Ahmed M Tawfik, J Matthias Kerl, Ralf W Bauer, Nour-Eldin Nour-Eldin, Nagy N N Naguib, Thomas J Vogl, Martin G Mack

  Investigative radiology. 05/2011;

  OBJECTIVES:: Mixing low- and high-voltage acquisitions of dual-energy CT (DECT) scan using different weighting factors leads to differences in attenuation values and image quality. The aim of thisOBJECTIVES:: Mixing low- and high-voltage acquisitions of dual-energy CT (DECT) scan using different weighting factors leads to differences in attenuation values and image quality. The aim of this work was to evaluate whether average weighting of DECT acquisitions could improve delineation of head and neck cancer and image quality. MATERIALS AND METHODS:: Among 60 consecutive patients who underwent DECT scan of the head and neck, 35 patients had positive findings and were included in the study. Images were reconstructed as pure 80 kVp, pure Sn140 kVp, and weighted-average (WA) image datasets from low- and high-voltage acquisitions using 3 different weighting factors (0.3, 0.6, 0.8) incorporating 30%, 60%, 80% from the 80 kVp data, respectively. Lesion contrast-to-noise ratio (CNR), attenuation measurements, and objective noise were compared between different image datasets. Two independent blinded radiologists subjectively rated the overall image quality of each image dataset on a 5-point grading scale comprising lesion delineation, image sharpness, and subjective noise. RESULTS:: Mean venous and tumor enhancement and muscle attenuation increased stepwise with decreasing tube voltage from Sn140 kVp through 80 kVp. CNR increased significantly from Sn140 kVp to weighting factor 0.3 then to weighting factor 0.6 (P < 0.0001). The increase in CNR from weighting factor 0.6 to 0.8 then to 80 kVp was nonsignificant (P = 1.00). The 0.6 weighted-average image dataset received the best image quality score by the 2 readers. CONCLUSION:: Mixing the DE data from the 80 kVp and Sn140 kVp tubes using weighting factor 0.6 (60% from 80 kVp data) could improve lesion CNR and subjective overall image quality (including lesion delineation). This weighting factor was significantly superior to the 0.3 weighting factor which simulates standard 120 kVp acquisition.

• Accuracy of coronary artery stenosis detection with CT versus conventional coronary angiography compared with composite findings from both tests as an enhanced reference standard.

  Authors: J Matthias Kerl, U Joseph Schoepf, Peter L Zwerner, Ralf W Bauer, Joseph A Abro, Christian Thilo, Thomas J Vogl, Christopher Herzog

  European radiology. 05/2011; 21(9):1895-903.

  To prospectively compare the accuracy of coronary CT angiography (CCTA) and conventional coronary angiography (CCA) for stenosis detection using composite findings from both tests as an enhancedTo prospectively compare the accuracy of coronary CT angiography (CCTA) and conventional coronary angiography (CCA) for stenosis detection using composite findings from both tests as an enhanced reference standard. One hundred thirteen patients underwent CCTA and CCA. Per-segment and per-patient accuracy of CCTA compared with initial CCA interpretation were determined. Angiographers were then unblinded to the CCTA results and re-evaluation of the CCA studies was performed with knowledge of CCTA findings, which was used as an enhanced reference standard to compare the diagnostic accuracy of CCTA versus CCA. When using the enhanced reference standard instead of initial CCA interpretation, CCTA accuracy for identifying segments (patients) with ≥50% stenosis increased from 97.7% (96.5%) to 98.1% (98.2%), sensitivity from 90.5% (100%) to 90.8% (100%), and specificity from 98.4% (94.3%) to 98.9% (97.1%). CCTA identified six segments and two patients with stenoses ≥50% missed on initial CCA interpretation. Compared with the enhanced reference standard the accuracies of CCTA and of initial CCA interpretation were not different (p = 0.87). CCTA compares favourably with CCA for stenosis detection. Use of a composite reference standard combining findings from both tests can control for the effect of false-negative CCA results when evaluating the accuracy of CCTA.

• Dual energy CT pulmonary blood volume assessment in acute pulmonary embolism - correlation with D-dimer level, right heart strain and clinical outcome.

  Authors: Ralf W Bauer, Claudia Frellesen, Matthias Renker, Boris Schell, Thomas Lehnert, Hanns Ackermann, U Joseph Schoepf, Volkmar Jacobi, Thomas J Vogl, J Matthias Kerl

  European radiology. 04/2011; 21(9):1914-21.

  To investigate the role of perfusion defect (PD) size on dual energy CT pulmonary blood volume assessment as predictor of right heart strain and patient outcome and its correlation with d-dimerTo investigate the role of perfusion defect (PD) size on dual energy CT pulmonary blood volume assessment as predictor of right heart strain and patient outcome and its correlation with d-dimer levels in acute pulmonary embolism (PE). 53 patients with acute PE who underwent DECT pulmonary angiography were retrospectively analyzed. Pulmonary PD size caused by PE was measured on DE iodine maps and quantified absolutely (VolPD) and relatively to the total lung volume (RelPD). Signs of right heart strain (RHS) on CT were determined. Information on d-dimer levels and readmission for recurrent onset of PE and death was collected. D-dimer level was mildly (r = 0.43-0.47) correlated with PD size. Patients with RHS had significantly higher VolPD (215 vs. 73 ml) and RelPD (9.9 vs. 2.9%) than patients without RHS (p < 0.003). There were 2 deaths and 1 readmission due of PE in 18 patients with >5% RelPD, while no such events were found for patients with <5% RelPD. Pulmonary blood volume on DECT in acute PE correlates with RHS and appears to be a predictor of patient outcome in this pilot study.

• Image fusion in dual energy computed tomography for detection of various anatomic structures--effect on contrast enhancement, contrast-to-noise ratio, signal-to-noise ratio and image quality.

  Authors: Jijo Paul, Ralf W Bauer, Werner Maentele, Thomas J Vogl

  European journal of radiology. 03/2011; 80(2):612-9.

  The purpose of this study was to evaluate image fusion in dual energy computed tomography for detecting various anatomic structures based on the effect on contrast enhancement, contrast-to-noiseThe purpose of this study was to evaluate image fusion in dual energy computed tomography for detecting various anatomic structures based on the effect on contrast enhancement, contrast-to-noise ratio, signal-to-noise ratio and image quality. Forty patients underwent a CT neck with dual energy mode (DECT under a Somatom Definition flash Dual Source CT scanner (Siemens, Forchheim, Germany)). Tube voltage: 80-kV and Sn140-kV; tube current: 110 and 290 mAs; collimation-2×32×0.6 mm. Raw data were reconstructed using a soft convolution kernel (D30f). Fused images were calculated using a spectrum of weighting factors (0.0, 0.3, 0.6 0.8 and 1.0) generating different ratios between the 80- and Sn140-kV images (e.g. factor 0.6 corresponds to 60% of their information from the 80-kV image, and 40% from the Sn140-kV image). CT values and SNRs measured in the ascending aorta, thyroid gland, fat, muscle, CSF, spinal cord, bone marrow and brain. In addition, CNR values calculated for aorta, thyroid, muscle and brain. Subjective image quality evaluated using a 5-point grading scale. Results compared using paired t-tests and nonparametric-paired Wilcoxon-Wilcox-test. Statistically significant increases in mean CT values noted in anatomic structures when increasing weighting factors used (all P≤0.001). For example, mean CT values derived from the contrast enhanced aorta were 149.2±12.8 Hounsfield Units (HU), 204.8±14.4 HU, 267.5±18.6 HU, 311.9±22.3 HU, 347.3±24.7 HU, when the weighting factors 0.0, 0.3, 0.6, 0.8 and 1.0 were used. The highest SNR and CNR values were found in materials when the weighting factor 0.6 used. The difference CNR between the weighting factors 0.6 and 0.3 was statistically significant in the contrast enhanced aorta and thyroid gland (P=0.012 and P=0.016, respectively). Visual image assessment for image quality showed the highest score for the data reconstructed using the weighting factor 0.6. Different fusion factors used to create images in DECT cause statistically significant differences in CT value, SNR, CNR and image quality. Best results obtained using the weighting factor 0.6 for all anatomic structures used in this study.

• Dual-energy computed tomography for the detection of late enhancement in reperfused chronic infarction: a comparison to magnetic resonance imaging and histopathology in a porcine model.

  Authors: Simon Deseive, Ralf W Bauer, Ralf Lehmann, Mattias Kettner, Christina Kaiser, Huedayi Korkusuz, Christa Tandi, Alf Theisen, Volker Schächinger, U Joseph Schoepf, Thomas J Vogl, J Matthias Kerl

  Investigative radiology. 03/2011; 46(7):450-6.

  To evaluate the performance of late enhancement dual-energy CT (LE-DECT) for the detection of infarcted myocardium as compared with 1.5-T late enhancement magnetic resonance imaging (LE-MRI) in aTo evaluate the performance of late enhancement dual-energy CT (LE-DECT) for the detection of infarcted myocardium as compared with 1.5-T late enhancement magnetic resonance imaging (LE-MRI) in a porcine model of reperfused chronic myocardial infarction (MI), using histopathology as standard of reference. In 8 healthy minipigs, MI was induced by 30-minute balloon occlusion of the left anterior descending coronary artery. Sixty-one ± 4 days after left anterior descending coronary artery occlusion, LE-DECT was performed 5, 10, and 15 minutes subsequent to contrast material injection. Therefore, a dual-source CT scanner (Somatom Definition, Siemens Healthcare, Forchheim, Germany) was used in dual-energy mode with the following protocol: tube potential/current 140 kV/95 mAs on tube A and 100 kV/165 mAs on tube B, collimation 2 × 32 × 0.6 mm, 1.5 mL/kg contrast material injected at 3 to 4 mL/s. Myocardial iodine distribution was calculated from the dual-energy data and superimposed on the gray scale multiplanar reformats of the heart in short-axis view. Fifty ± 12 minutes after LE-DECT imaging, 1.5-T LE-MRI (Magnetom Avanto, Siemens Healthcare, Forchheim, Germany) was performed 10 minutes successive to injection of contrast material using phase-sensitive inversion recovery sequences. For all pigs investigated, 2,3,5-triphenyltetrazolium chloride staining and histopathology of stained-tissue samples were acquired. Two experienced radiologists assessed all imaging studies in a random manner and were blinded to the results of the other techniques for the presence of late enhancement (LE). The American Heart Association 17-segment model was used to compare the results of LE-DECT, 100 kV grayscale LE images, LE-MRI, and histopathology. Size of MI was calculated for histopathological findings, LE-MRI, LE-DECT, and 100 kV grayscale LE images 10 minutes after contrast agent injection. Agreement between infarct size assessed with imaging modalities and histopathology was evaluated with Bland-Altman analysis. Of the 136 myocardial segments in 8 minipigs, histopathology found MI in 27 segments. Diagnostic per-segment sensitivities and specificities for 100 kV grayscale LE images, LE-DECT images, and MR images obtained 10 minutes after contrast agent injection for both the readers were 0.62, 0.77, 0.79 and 0.97, 0.92, 0.94, respectively. Although sensitivities were higher for LE-DECT and LE-MRI than for 100 kV grayscale images, no statistically significant difference for the diagnostic accuracies of 100 kV grayscale LE images, LE-DECT images, and MR images (0.9, 0.89, 0.9) existed 10 minutes successive to contrast agent injection (all P > 0.05). Infarct size for LE-MRI, LE-DECT, and 100 kV grayscale LE images correlated well with histopathological findings (r = 0.97, 0.96, and 0.94; all P < 0.01). This feasibility study shows a high accuracy and a good correlation of LE-DECT and LE-MRI to histopathology for the detection of LE in a porcine model of reperfused chronic MI.

• Dose levels at coronary CT angiography--a comparison of Dual Energy-, Dual Source- and 16-slice CT.

  Authors: J Matthias Kerl, Ralf W Bauer, Tobias B Maurer, Rene Aschenbach, Huedayi Korkusuz, Thomas Lehnert, Simon Deseive, Hanns Ackermann, Thomas J Vogl

  European radiology. 03/2011; 21(3):530-7.

  To compare the dose estimates and image quality of Dual Energy CT (DECT), Dual Source CT (DSCT) and 16-slice CT for coronary CT angiography (cCTA). Sixty-eight patients were examined with 16 - sliceTo compare the dose estimates and image quality of Dual Energy CT (DECT), Dual Source CT (DSCT) and 16-slice CT for coronary CT angiography (cCTA). Sixty-eight patients were examined with 16 - slice MDCT (group 1), 68 patients with DSCT (group 2) and 68 patients using DSCT in dual energy mode (DECT group 3). CT dose index volume, dose length product, effective dose, signal-to-noise, and contrast-to-noise ratio were compared. Subjective image quality was rated by two observers, blinded to technique. The mean estimated radiation dose of all patients investigated on a 16 - slice MDCT was 12 ± 3.59 mSv, for DSCT in single energy 9.8 ± 4.77 mSv and for DECT 4.54 ± 1.87 mSv. Dose for CTA was significantly lower in group 3 compared to group 1 and 2. The image noise was significantly lower in Group 2 in comparison to group 1 and group 3. There was no significant difference in diagnostic image quality comparing DECT and DSCT. cCTA shows better dose levels at both DECT and DSCT compared to 16-slice CT. Further, DECT delivers significantly less dose than regular DSCT or single source single energy cCTA while maintaining diagnostic image quality.

• Low-dose computed tomography of the paranasal sinus and facial skull using a high-pitch dual-source system--first clinical results.

  Authors: Boris Schell, Ralf W Bauer, Thomas Lehnert, J Matthias Kerl, Markus Hambek, Angelika May, Thomas J Vogl, Martin G Mack

  European radiology. 01/2011; 21(1):107-12.

  Computed tomography (CT) of the paranasal sinus is the standard diagnostic tool for a wide range of indications in mostly younger patients. This study aims to assess the image quality of CT of theComputed tomography (CT) of the paranasal sinus is the standard diagnostic tool for a wide range of indications in mostly younger patients. This study aims to assess the image quality of CT of the sinus by using a high-pitch dual-source technique with special regard to the radiation dose. Examinations were performed on a second-generation dual-source CT with a pitch factor of 3.0 (dual-source mode). Images were compared with those with a pitch factor of 0.9 on the same system (single-source mode) and with those of 16-slice CT. Image quality was evaluated by four blinded readers using a 5-point scale (1=poor, 5=excellent). Comparison of the dose length product (DLP) was used to estimate radiation exposure. Seventy-three consecutive patients underwent imaging with the proposed CT protocols. The viewers rated the image quality of the dual-source image sets as nearly as good (3.62) as the single-source images on the same device (4.18) and those on 16-slice CT (3.7). DLP was cut to half of the dose [51 mGycm vs. 97.8 mGycm vs. 116.9 mGycm (p<0.01)]. Using the proposed dual-source mode when examining the paranasal sinus, diagnostic image quality can be achieved while drastically lowering the patient's radiation exposure.

• 64-slice multidetector-row computed tomography in the diagnosis of coronary artery disease: interobserver agreement among radiologists with varied levels of experience on a per-patient and per-segment basis.

  Authors: Josef Matthias Kerl, U Joseph Schoepf, Ralf W Bauer, Tuna Tekin, Philip Costello, Thomas J Vogl, Christopher Herzog

  Journal of thoracic imaging. 12/2010; 27(1):29-35.

  To assess the interobserver variability of 4 radiologists with different levels of experience in the evaluation of 64-slice coronary computed tomographic angiography (cCTA). Two board-certifiedTo assess the interobserver variability of 4 radiologists with different levels of experience in the evaluation of 64-slice coronary computed tomographic angiography (cCTA). Two board-certified radiologists with 10 and 8 years of experience in reading cCTA and 2 radiology residents, 1 with 3 years of experience in reading cCTA and 1 with experience in reading general computed tomographic scans but without dedicated cCTA training, participated in the study. All the observers independently analyzed 50 cCTA studies for signs of coronary artery disease (stenosis of 0%, ≤49%, 50% to 74%, 75% to 99%, or 100%). Diagnostic accuracy of the 4 readers for stenosis detection on cCTA was compared with that of conventional angiography on a per-segment and per-patient basis. No patients, vessels, or segments were excluded from analysis. On a per-segment basis, correlation between cCTA and invasive coronary angiography was good for readers with more than 10 (r=0.75), more than 8 (r=0.75), and more than 3 (r=0.73) years of cCTA experience. The correlation coefficient was poor (r=0.39) for the untrained reader. Sensitivity was not significantly (P=0.56) different between observers with more than 8 and more than 10 years of experience but was significantly (P>0.05) lower for the reader with less than 3 years experience and for the untrained reader. However, we found no significant difference in overall diagnostic accuracy on a per-patient (P=0.86) and on a per-segment level (P=0.72) among the 4 readers. The level of experience significantly influences the sensitivity of coronary artery stenosis detection at cCTA, and thus highlights the need for dedicated training in cCTA interpretation.

• Lung perfusion analysis with dual energy CT in patients with suspected pulmonary embolism--influence of window settings on the diagnosis of underlying pathologies of perfusion defects.

  Authors: Ralf W Bauer, J Matthias Kerl, Eva Weber, Philipp Weisser, Huedayi Korkusuz, Thomas Lehnert, Volkmar Jacobi, Thomas J Vogl

  European journal of radiology. 10/2010; 80(3):e476-82.

  On lung perfusion analysis with dual energy CT (DECT) in patients with suspected pulmonary embolism (PE) commonly three patterns of perfusion defects (PD) are observed: wedge-shaped, circumscribedOn lung perfusion analysis with dual energy CT (DECT) in patients with suspected pulmonary embolism (PE) commonly three patterns of perfusion defects (PD) are observed: wedge-shaped, circumscribed but not wedge-shaped, and patchy. We investigated the influence of different window settings on the identification of the underlying pathologies for these types of PD. 3724 segments in 196 consecutive patients who underwent pulmonary DECT angiography for clinically suspected acute PE were analyzed. Iodine distribution in the lung parenchyma was calculated from the dual energy data and displayed as color map in axial, sagittal and coronal view. Afterwards, lung and angiography window were applied separately and assessed for pulmonary embolism and pathologies of the lung parenchyma. 1420 segments in 141 patients showed PD, of which 276 were wedge-shaped, 287 circumscribed and 857 patchy. Circumscribed PD were associated in 99% with interstitial or alveolar fluid collections and in 1% with located bullae. Patchy PD were associated in 65% with emphysematous or fibrotic changes, in 38% with diffuse infiltrations or interstitial fluid collections and in 0.2% with PE. The underlying pathologies for wedge-shaped PD were in 78% PE, in 3% tumors compressing pulmonary arteries, in another 3% located bullae and in further 3% infiltrations. 13% (n=15) of the segments in this group did not show vascular or parenchymal pathologies, but in 80% (n=10) of these cases patients had PE in another segment. Totally n=6 of wedge-shaped PD in 5 patients remained with unclear direct cause. Whereas patchy and circumscribed PD are almost exclusively associated with pathologies of the lung parenchyma, wedge-shaped PD are mostly associated with PE. For a small number of wedge-shaped PD the underlying cause cannot be detected with DECT. Very small peripherally situated micro-emboli may be discussed as a reason. However, prospective trials are needed to clarify the value of this finding.