Sebastian Vogt

Publications of Sebastian Vogt

• Coronary CT angiography: image quality, diagnostic accuracy, and potential for radiation dose reduction using a novel iterative image reconstruction technique-comparison with traditional filtered back projection.

  Authors: Antonio Moscariello, Richard A P Takx, U Joseph Schoepf, Matthias Renker, Peter L Zwerner, Terrence X O'Brien, Thomas Allmendinger, Sebastian Vogt, Bernhard Schmidt, Giancarlo Savino, Christian Fink, Lorenzo Bonomo, Thomas Henzler

  European radiology. 05/2011; 21(10):2130-8.

  To compare image noise, image quality and diagnostic accuracy of coronary CT angiography (cCTA) using a novel iterative reconstruction algorithm versus traditional filtered back projection (FBP) andTo compare image noise, image quality and diagnostic accuracy of coronary CT angiography (cCTA) using a novel iterative reconstruction algorithm versus traditional filtered back projection (FBP) and to estimate the potential for radiation dose savings. Sixty five consecutive patients (48 men; 59.3 ± 7.7 years) prospectively underwent cCTA and coronary catheter angiography (CCA). Full radiation dose data, using all projections, were reconstructed with FBP. To simulate image acquisition at half the radiation dose, 50% of the projections were discarded from the raw data. The resulting half-dose data were reconstructed with sinogram-affirmed iterative reconstruction (SAFIRE). Full-dose FBP and half-dose iterative reconstructions were compared with regard to image noise and image quality, and their respective accuracy for stenosis detection was compared against CCA. Compared with full-dose FBP, half-dose iterative reconstructions showed significantly (p = 0.001 - p = 0.025) lower image noise and slightly higher image quality. Iterative reconstruction improved the accuracy of stenosis detection compared with FBP (per-patient: accuracy 96.9% vs. 93.8%, sensitivity 100% vs. 100%, specificity 94.6% vs. 89.2%, NPV 100% vs. 100%, PPV 93.3% vs. 87.5%). Iterative reconstruction significantly reduces image noise without loss of diagnostic information and holds the potential for substantial radiation dose reduction from cCTA.

• In vitro evaluation of metallic coronary artery stents with 64-MDCT using an ECG-gated cardiac phantom: relationship between in-stent visualization, stent type, and heart rate.

  Authors: J Matthias Kerl, U Joseph Schoepf, Thomas J Vogl, Hanns Ackermann, Sebastian Vogt, Philip Costello, Christopher Herzog

  AJR. American journal of roentgenology. 03/2010; 194(3):W256-62.

  The purpose of this study was to assess the accuracy of 64-MDCT in the visualization of different coronary artery stents and in the appraisal of in-stent stenosis. MATERIALS AND METhODS: FiveThe purpose of this study was to assess the accuracy of 64-MDCT in the visualization of different coronary artery stents and in the appraisal of in-stent stenosis. MATERIALS AND METhODS: Five different coronary stent types with three diameters (2.5, 3.0, and 4.0 mm) were analyzed using anthropomorphic dynamic cardiac phantom. All stents were mounted on polyurethane sticks of defined outer diameter and contained a default concentric stenosis of 50% each. Imaging was performed at four different heart rates (no motion, 60 beats/min, 75 beats/min, and 90 beats/min). Apparent stent diameter, degree of stenosis, in-stent attenuation, and diagnostic accuracy were assessed. A significant (p < 0.05) overestimation of the degree of stenosis (41.1% +/- 41.4%), underestimation of the stent lumen (-42.7% +/- 41.4%), and increase in in-stent attenuation (36.6 +/- 29.2 HU) were observed for all stents and heart rates. In-stent stenosis > 50% was detected with an overall sensitivity of 88.9% (95% CI, 75.9-96.3%) and an overall specificity of 51.1% (95% CI, 35.8-66.3%) by observer 1 and with an overall sensitivity of 86.7% (95% CI, 73.2-94.9%) and an overall specificity of 57.8% (95% CI, 42.2-72.3%) by observer 2. A trend toward higher specificity was observed for increasing stent diameter, however, without reaching statistical significance (p = 0.63). In an experimental setting, 64-MDCT allows a reliable detection of instent stenosis but significantly overestimates the actual degree of stenosis. Within the range of physiologic heart rates, diagnostic accuracy is restricted by spatial, not temporal, resolution.

• Coronary CT angiography: automatic cardiac-phase selection for image reconstruction.

  Authors: Balazs Ruzsics, Mulugeta Gebregziabher, Heon Lee, Robin Brothers, Thomas Allmendinger, Sebastian Vogt, Philip Costello, U Schoepf

  European radiology. 03/2009;

  We evaluated an algorithm for automatic selection of the cardiac phase with the least motion for image reconstruction at coronary computed tomography (CT) angiography (CCTA). We analyzed data of 100We evaluated an algorithm for automatic selection of the cardiac phase with the least motion for image reconstruction at coronary computed tomography (CT) angiography (CCTA). We analyzed data of 100 patients (49 female, mean age 59 years) who had undergone retrospectively ECG-gated CCTA. Two experienced observers visually identified the most suitable end-systolic and end-diastolic phases using a series of image reconstructions in 5% increments across the RR cycle. The same data were then reconstructed using an automatic phase finding algorithm based on a 4D weighting function of cardiac motion. On average, the algorithm determined the most suitable systolic reconstruction phase at 40.11 +/- 6.29% RR compared with 40.07 +/- 5.58% RR by the human observers (p = NS). The most suitable diastolic phase was found at 72.71 +/- 7.37% RR by the automatic algorithm, compared with 76.43 +/- 6.35% RR by the observers (p < 0.05). No statistically significant difference was found between automatically and visually determined reconstruction phases regarding motion and stair-step artifacts in either systole or diastole (p > 0.05). Thus, there appears to be no relevant difference between an automatic phase finding algorithm and visual selection by experienced observers for determining the phase with the least cardiac motion for CCTA image reconstruction. The use of automatic phase finding may therefore facilitate the performance of cardiac CT and reduce human error.

• Dual-energy CT of the heart-Principles and protocols.

  Authors: Florian Schwarz, Balazs Ruzsics, U Joseph Schoepf, Gorka Bastarrika, Salvatore A Chiaramida, Joseph A Abro, Robin L Brothers, Sebastian Vogt, Bernhard Schmidt, Philip Costello, Peter L Zwerner

  European journal of radiology. 12/2008;

  The introduction of coronary CT angiography (cCTA) has reinvigorated the debate whether management of patients with suspected coronary artery disease (CAD) should be primarily based on physiologicalThe introduction of coronary CT angiography (cCTA) has reinvigorated the debate whether management of patients with suspected coronary artery disease (CAD) should be primarily based on physiological versus anatomical testing. Anatomical testing (i.e., cCTA or invasive catheterization) enables direct visualization and grading of coronary artery stenoses but has shortcomings for gauging the hemodynamic significance of lesions for myocardial perfusion. Conversely, rest/stress myocardial perfusion imaging (MPI) has been extensively validated for assessing the clinical significance of CAD by demonstrating fixed or reversible perfusion defects but has only limited anatomical information. There is early evidence that contrast medium enhanced dual-energy cCTA (DECT) has potential for the comprehensive analysis of coronary artery morphology as well as changes in myocardial perfusion. DECT exploits the fact that tissues in the human body and iodine-based contrast media have unique absorption characteristics when penetrated with different X-ray energy levels, which enables mapping the iodine (and thus blood) distribution within the myocardium. The purpose of this communication is to describe the practical application of this emerging technology for the comprehensive diagnosis of coronary artery disease in the context of the currently used tomographic imaging modalities (cCTA, nuclear MPI, MR MPI).

• High-temporal resolution dual-energy computed tomography of the heart using a novel hybrid image reconstruction algorithm: initial experience.

  Authors: John William Nance, Gorka Bastarrika, Doo Kyoung Kang, Balazs Ruzsics, Sebastian Vogt, Bernhard Schmidt, Rainer Raupach, Thomas G Flohr, U Joseph Schoepf

  Journal of computer assisted tomography. 35(1):119-25.

  Dual-energy computed tomography (DECT) has been proposed for the comprehensive assessment of coronary artery stenosis and myocardial perfusion yet traditionally required reducing the temporalDual-energy computed tomography (DECT) has been proposed for the comprehensive assessment of coronary artery stenosis and myocardial perfusion yet traditionally required reducing the temporal resolution of cardiac studies. We evaluated a reconstruction algorithm that preserves high temporal resolution at cardiac DECT. Twelve consecutive patients (3 women; mean [SD] age, 64 [10] years) with an abnormal single photon emission CT result underwent invasive coronary angiography and cardiac DECT. Dual-energy CT studies were reconstructed using the standard algorithm with 165-millisecond temporal resolution and a hybrid algorithm providing 83-millisecond temporal resolution. These studies were rated for coronary image quality and motion artifacts and compared with invasive coronary angiographic studies. One hundred sixty-eight coronary artery segments (82%) were evaluated. The standard 165-millisecond reconstruction provided 95% diagnostic segments compared with 100% using the 83-millisecond hybrid reconstruction. Image quality was rated significantly (P < 0.05) better with hybrid reconstruction and had 91.4% sensitivity, 94.7% specificity, 82.1% positive predictive value, and 97.7% negative predictive value for detecting significant stenosis versus 85.7%, 93.2%, 76.9%, and 96.1% with standard reconstruction, respectively. Hybrid image reconstruction mitigates the former limitations in temporal resolution of cardiac DECT.

• Iterative image reconstruction techniques: Applications for cardiac CT.

  Authors: Matthias Renker, Ashok Ramachandra, U Joseph Schoepf, Rainer Raupach, Paul Apfaltrer, Garrett W Rowe, Sebastian Vogt, Thomas G Flohr, J Matthias Kerl, Ralf W Bauer, Christian Fink, Thomas Henzler

  Journal of cardiovascular computed tomography. 5(4):225-30.

  Traditional limitations of cardiac CT are related to image noise, blooming artifacts from calcifications and stents, and radiation exposure. We evaluated whether these limitations can be amelioratedTraditional limitations of cardiac CT are related to image noise, blooming artifacts from calcifications and stents, and radiation exposure. We evaluated whether these limitations can be ameliorated by the use of iterative reconstruction in image space (IRIS) instead of traditional filtered back projection (FBP) image reconstruction techniques. We compared image reconstruction with the use of IRIS with traditional FBP for their effect on image quality, noise, volume of heavy coronary artery calcifications, and stents as a measure of "blooming" artifacts, and radiation dose at cardiac CT. The radiation dose comparison was performed as a matched pair analysis, whereas all other comparisons were performed within the same group of patients. The subjective image quality of IRIS reconstructions was rated higher than FBP reconstructions. Image noise was lower with IRIS than with FBP. The volume of stents and heavy coronary artery calcifications measured lower in IRIS reconstructed series compared with FBP. Similar levels of image noise were achieved with 80/100 kVp of tube voltage with IRIS compared with 120 kVp and FBP, resulting in a 62% reduction in effective dose. Our preliminary experiences suggest that IRIS incrementally improves the CT evaluation of coronary arteries, especially in challenging scenarios. Substantial radiation reduction seems feasible without associated increases in image noise.