Axel Kuettner

Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Bavaria, Germany

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Publications (187)488.29 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Paclitaxel, eine sehr potente antiproliferative Substanz, fördert die Bildung ungewöhnlich stabiler und funktionsgestörter Mikrotubuli und verändert dadurch zelluläre Mechanismen, die letztlich zu verminderter Proliferation, Migration und Signaltransduktion führen. Paclitaxel ist lipophil, was eine rasche Aufnahme in die Zelle fördert, und hat einen langanhaltenden Effekt in der Zelle aufgrund der strukturellen Veränderung des Zytoskelettes. Diese Eigenschaften machen Paclitaxel zu einem vielversprechenden Kandidaten für die lokale Medikamentenapplikation zur Restenoseprophylaxe. In dieser Arbeit werden die in-vitro und in-vivo Ergebnisse aus unseren Forschungsarbeiten zu Paclitaxel vorgestellt. Zellkulturexperimente mit Monokulturen von humanen glatten Gefäßmuskelzellen sowie mit Co-Kulturen mit humanen Endothelzellen zeigten, daß Paclitaxel in einem Dosisbereich zwischen 1,0 und 10,0μmol/l zu einer beinahe vollständigen Wachstumshemmung, selbst nach kurzer (20 min.) Einmalapplikation führt. Nach Vergleich von 3 verschiedenen Kathetersystemen (poröser Ballon, mikroporöser Ballon und Doppelballon) wurde der Doppelballon für die in-vivo Anwendung favorisiert. Anhand von Anfärbungen des Zytoskelettes sowie elektronenoptisch gelang der Nachweis der Paclitaxelwirkung in den glatten Muskelzellen der Gefäßwand. Im Kaninchen führte lokal appliziertes Paclitaxel zu einer signifikanten Hemmung der neointimalen Proliferation und Erweiterung des Gefäßdurchmessers im Vergleich zu ballondilatierten Kontrolltieren. In Zusatzexperimenten konnte eine drastische Verringerung der vaskulären Kontraktionskraft nach Paclitaxelgabe gezeigt werden. Ähnlich eindeutige Ergebnisse fanden sich nach Stentimplantation im Schweinemodell nicht. Paclitaxel, a potent anti-tumor agent, shifts the cytoskeleton equilibrium towards assembly of altered and extraordinarily stable microtubules. These cellular modifications lead to reduced proliferation, migration, and signal transduction. It is highly lipophilic, which promotes a rapid cellular uptake, and has a long-lasting effect in the cell due to the structural alteration of the cytoskeleton. This makes paclitaxel a promising candidate for local drug delivery intended to address the proliferative and migratory processes involved in restenosis. In this article, results of our in vitro and in vivo studies with paclitaxel are presented. Cell culture experiments with monocultures of human arterial smooth muscle cells as well as cocultures with human endothelial cells showed that paclitaxel leads to an almost complete growth inhibition within a dose range of 1.0–10.0μmol/l, even after a short (20 min) single dose application. The comparison of an active, semi-active, and passive delivery system (porous balloon, microporous balloon, and double balloon) favored the double balloon for the following in vivo experiments. Tubulin staining and electron microscopy enabled visualization of paclitaxel-induced vessel wall alterations. In the rabbit model, locally delivered paclitaxel resulted in reduced neointima formation and enlargement in vessel size; in the pig model, however, after stenting, this inhibition was not significant. Both reduced proliferation and enlargement in vessel size contribute to a preservation of vessel shape and are likely to be caused by a structural alteration of the cytoskeleton, which is also supported by vascular contraction force experiments. Schlüsselwörter PTCA –¶Angioplastie – Paclitaxel –¶Restenose – TaxolKey words Angioplasty – smooth muscle – paclitaxel – restenosis – taxol
    Zeitschrift für Kardiologie 04/2012; 89(5):390-397. · 0.97 Impact Factor
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    ABSTRACT: To evaluate radiation dose levels in patients undergoing spiral coronary computed tomography angiography (CTA) on a dual-source system in clinical routine. Coronary CTA was performed for 56 patients with electrocardiogram-triggered tube current modulation (TCM) and heart-rate (HR) dependent pitch adaptation. Individual Monte Carlo (MC) simulations were performed for dose assessment. Retrospective simulations with constant tube current (CTC) served as reference. Lung tissue was segmented and used for organ and effective dose (ED) calculation. Estimates for mean relative ED was 7.1 ± 2.1 mSv/100 mAs for TCM and 12.5 ± 5.3 mSv/100 mAs for CTC (P < 0.001). Relative dose reduction at low HR (≤60 bpm) was highest (49 ± 5%) compared to intermediate (60-70 bpm, 33 ± 12%) and high HR (>70 bpm, 29 ± 12%). However lowest ED is achieved at high HR (5.2 ± 1.5 mSv/100 mAs), compared with intermediate (6.7 ± 1.6 mSv/100 mAs) and low (8.3 ± 2.1 mSv/100 mAs) HR when automated pitch adaptation is applied. Radiation dose savings up to 52% are achievable by TCM at low and regular HR. However lowest ED is attained at high HR by pitch adaptation despite inferior radiation dose reduction by TCM. KEY POINTS : • Monte Carlo simulations allow for individual radiation dose calculations. • ECG-triggered tube current modulation (TCM) can effectively reduce radiation dose. • Slow and regular heart rates allow for highest dose reductions by TCM. • Adaptive pitch accounts for lowest radiation dose at high heart rates. • Women receive higher effective dose than men undergoing spiral coronary CT-angiography.
    European Radiology 03/2012; 22(3):569-78. · 4.34 Impact Factor
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    ABSTRACT: To evaluate, whether semi-automated vessel extraction and curved planar reformations ("automated vessel extraction") increases diagnostic accuracy in the detection of relevant coronary artery lesions compared to manual, interactive multiplanar interpretation ("manual approach"). 50 coronary CT angiography datasets were evaluated by four independent readers (two experienced, two novice) for the presence of stenoses exceeding 50% diameter reduction. One experienced and one novice reader each used the "manual approach" for cases 1-25 and "automated vessel extraction" for cases 26-50, while the other two readers used the complementary method. Results were compared to those of invasive coronary angiography. Using the "manual approach", 37 of 42 stenoses were correctly detected by experienced as well as novice readers. 14 vs. 17 lesions were false positive (sensitivity 88%, specificity 91% vs. 89%, PPV 73% vs. 69%, NPV 97%, n.s.). Using "automated vessel extraction", experienced readers detected 35/42 stenoses compared to 31/42 for novice readers. 7 vs. 11 lesions were missed and 17 vs. 15 false-positive lesions reported (sensitivity 83% vs. 74%, specificity 89% vs. 90%, PPV 67%, NPV 95% vs. 93%, n.s.).In patient-based analysis, for novice readers sensitivity was higher using the "manual approach" (97%, 29/30 pts. vs. 80%, 24/30 pts., p=0.069). Semi-automated vessel extraction and curved multiplanar reconstructions do not improve the diagnostic accuracy of coronary CT angiography compared to the use of interactive multiplanar reformations. Especially for less experienced readers, the use of automatically rendered curved multiplanar reconstructions alone cannot be recommended.
    European journal of radiology 10/2011; 80(1):89-95. · 2.65 Impact Factor
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    ABSTRACT: An extensive number of protocols have been suggested to allow for functional diagnostics; however, no data is available about the minimal amount of contrast medium to achieve reliable imaging properties. None of the plethora of existing studies report a rational why the specific concentration was chosen. A total of 40 patients were included in this prospective, controlled study. They were divided up into four equal groups getting a different concentration (10%, 20%, 30% or 40%) of a second contrast medium bolus. Corresponding septal and right ventricular ROIs were compared. A visual score was established. Coronary attenuation was measured in the right and left coronary artery. Streak artifacts in the right atrium/ventricle were assessed. In the 10% contrast medium (CM) group only in 5/10 (50%) patients full septal delineation was reached. In all other groups full septal visualization was obtained. No group showed a relevant difference of mean density measured in HU units of the left ventricle or the coronary arteries. All study groups except of group 1 (10% CM) showed streak artifacts in the right atrium. The dual flow protocol with a minimum concentration of 20% improves septal visualization as basis for left ventricular functional assessment, however, does not allow for reliable right ventricular or atrial visualization. There is no significant difference between the different concentration protocols in terms of coronary attenuation.
    European journal of radiology 06/2011; 81(4):e461-6. · 2.65 Impact Factor
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    ABSTRACT: computed tomography (CT) is considered the method of choice in thoracic imaging for a variety of indications. Sedation is usually necessary to enable CT and to avoid deterioration of image quality because of patient movement in small children. We evaluated a new, subsecond high-pitch scan mode (HPM), which obviates the need of sedation and to hold the breath. a total of 60 patients were included in this study. 30 patients (mean age, 14 ± 17 month; range, 0-55 month) were examined with a dual source CT system in an HPM. Scan parameters were as follows: pitch = 3.0, 128 × 0.6 mm slice acquisition, 0.28 seconds gantry rotation time, ref. mAs adapted to the body weight (50-100 mAs) at 80 kV. Images were reconstructed with a slice thickness of 0.75 mm. None of the children was sedated for the CT examination and no breathing instructions were given. Image quality was assessed focusing on motion artifacts and delineation of the vascular structures and lung parenchyma. Thirty patients (mean age, 15 ± 17 month; range, 0-55 month) were examined under sedation on 2 different CT systems (10-slice CT, n = 18; 64-slice CT, n = 13 patients) in conventional pitch mode (CPM). Dose values were calculated from the dose length product provided in the patient protocol/dose reports, Monte Carlo simulations were performed to assess dose distribution for CPM and HPM. all scans were performed without complications. Image quality was superior with HPM, because of a significant reduction in motion artifacts, as compared to CPM with 10- and 64-slice CT. In the control group, artifacts were encountered at the level of the diaphragm (n = 30; 100%), the borders of the heart (n = 30; 100%), and the ribs (n = 20; 67%) and spine (n = 6; 20%), whereas motion artifacts were detected in the HPM-group only in 6 patients in the lung parenchyma next to the diaphragm or the heart (P < 0,001). Dose values were within the same range in the patient examinations (CPM, 1.9 ± 0.6 mSv; HPM, 1.9 ± 0.5 mSv; P = 0.95), although z-overscanning increased with the increase of detector width and pitch-value. high-pitch chest CT is a robust method to provide highest image quality making sedation or controlled ventilation for the examination of infants, small or uncooperative children unnecessary, whereas maintaining low radiation dose values.
    Investigative radiology 02/2011; 46(2):116-23. · 4.85 Impact Factor
  • Sedat Alibek, Michael Uder, Axel Kuettner
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    ABSTRACT: PURPOSE Evaluate image quality of spiral-CT exams with a dual source CT system using a high pitch mode in free breathing non-sedated children METHOD AND MATERIALS 63 consecutive children (age range 1-18 years, mean age: 5,7 years) who were referred to chest or abdomen CT were scanned with a dual source CT system with a high-pitch spiral mode protocol. Patient were not intubated and not sedated. Image quality was rated by two experienced radiologists on a three point quality scale in consensus; special focus was on motion artefacts of lung parenchyma, aortic root and anterior chest/abdominal wall (0: non-diagnostic, 1: acceptable, 2: excellent image quality). RESULTS All examinations were technically successful and overall image quality score was 2,0. CONCLUSION Spiral chest/abdomen CT with high-pitch on a dual source system seems to be feasible for pediatric patients without sedation in free breathing and delivers excellent image quality. CLINICAL RELEVANCE/APPLICATION Pediatric patients do not need to be sedated and can breath freely when using a hig pitch spiral CT mode for chest/abdomen CT exams.
    Radiological Society of North America 2010 Scientific Assembly and Annual Meeting; 12/2010
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    ABSTRACT: The computed tomographic (CT) attenuation of coronary atherosclerotic plaque has been proposed as a marker for tissue characterization and may thus potentially contribute to the assessment of plaque instability. We analyzed the influence of reconstruction parameters on CT attenuation measured within noncalcified coronary atherosclerotic lesions. Seventy-two patients were studied by contrast-enhanced dual-source CT coronary angiography (330 millisecond rotation time, 2 x 64 x 0.6 mm collimation, 120 kV, 400 mAs, 80 mL contrast agent intravenously at 6 mL/s), and a total of 100 distinct noncalcified coronary atherosclerotic plaques were identified. Image data sets were reconstructed with a soft (B20f), medium soft (B26f), and sharp (B46f) reconstruction kernel. With the medium soft kernel, image data sets were reconstructed with a slice thickness/increment of 0.6/0.3 mm, 0.75/0.4 mm, and 1.0/0.5mm. Within each plaque, CT attenuation was measured. Mean CT attenuation using the medium soft kernel was 109 +/- 58 HU (range, -16 to 168 HU). Using the soft kernel, mean density was 113 +/- 57 HU (range, -13 to 169 HU), and using a sharp kernel, mean density was 97 +/- 49 HU (range, -23 to 131 HU). Similarly, reconstructed slice thickness had a significant influence on the measured CT attenuation (mean values for medium soft kernel: 102 +/- 52 HU versus 109 +/- 58 HU versus 113 +/- 57 HU for 0.6-mm, 0.75-mm, and 1.0-mm slice thickness). The differences between 0.75-mm and 0.6-mm slice thickness (P = 0.05) and between medium sharp and sharp kernels (P = 0.02) were statistically significant. Image reconstruction significantly influences CT attenuation of noncalcified coronary atherosclerotic plaque. With decreasing spatial resolution (softer kernel or thicker slices), CT attenuation increases significantly. Using absolute CT attenuation values for plaque characterization may therefore be problematic.
    Journal of cardiovascular computed tomography 01/2010; 4(2):110-5. · 2.55 Impact Factor
  • Rofo-fortschritte Auf Dem Gebiet Der Rontgenstrahlen Und Der Bildgebenden Verfahren - ROFO-FORTSCHR RONTGENSTRAHL. 01/2010; 182.
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    ABSTRACT: Diarrhea is common in patients with Crohn's disease and may be accompanied by acid base disorders, most commonly metabolic acidosis due to intestinal loss of bicarbonate. Here, we present a case of severe metabolic alkalosis in a young patient suffering from M. Crohn. The patient had undergone multiple resections of the intestine and suffered from chronic kidney disease. He was now referred to our clinic for recurrent acute kidney injury, the nature of which was pre-renal due to profound volume depletion. Renal failure was associated with marked hypochloremic metabolic alkalosis which only responded to high volume repletion and high dose blockade of gastric hypersecretion. Intestinal failure with stomal fluid losses of up to 5.7 litres per day required port implantation to commence parenteral nutrition. Fluid and electrolyte replacement rapidly improved renal function and acid base homeostasis. This case highlights the important role of gastrointestinal function to maintain acid base status in patients with Crohn's disease.
    BMC Nephrology 01/2010; 11:6. · 1.64 Impact Factor
  • Journal of The American College of Cardiology - J AMER COLL CARDIOL. 01/2010; 55(10).
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    ABSTRACT: We evaluated the feasibility and image quality of a new scan mode for coronary computed tomography angiography (CTA) with an effective dose of less than 1 mSv. In 50 consecutive patients (body weight <or= 100 kg, sinus rhythm <or=60 b.p.m. after pre-medication, coronary CTA was performed using a dual-source CT system with 2 x 128 x 0.6 mm collimation, 0.28 s rotation time, a pitch of 3.2 or 3.4, 100 kV tube voltage and current of 320 mA s. Data acquisition was prospectively triggered at 60% of the R-R interval and completed within one cardiac cycle. Image quality was evaluated using a four-point scale (1 = absence of any artefacts to 4 = uninterpretable). In all 50 patients, imaging was successful. Mean duration of data acquisition was 258 +/- 20 ms. Mean dose-length product was 62 +/- 5 mGy cm, the effective dose was 0.87 +/- 0.07 mSv (0.78-0.99 mSv). Of the 742 coronary artery segments, 94% had an image quality score of 1, 5.0% a score of 2, 0.9% a score of 3, and 4 segments (0.5%) were 'uninterpretable'. In non-obese patients with a low and stable heart rate, prospectively ECG-triggered high-pitch spiral coronary CTA provides excellent image quality at a consistent dose below 1.0 mSv.
    European Heart Journal 11/2009; 31(3):340-6. · 14.72 Impact Factor
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    ABSTRACT: To evaluate staged low-dose approaches for coronary CT angiography (CTA) in which a standard sequence was added if the low-dose sequence did not allow reliable rule-out of coronary stenosis. A total of 176 consecutive patients referred for dual-source CTA were randomized to three protocols: group 1 using prospective ECG-triggering (100 kV, 330 mAs), group 2 a retrospectively gated "MinDose" sequence (100 kV, 330 mAs) and group 3 a standard spiral sequence (120 kV, 400 mAs). If image quality in low-dose groups 1 or 2 was non-diagnostic, an additional standard CT examination (as in group 3) was performed. Non-diagnostic image quality was found in 11/56, 4/55, and 2/65 patients (46/896, 4/880 and 3/1,040 coronary segments) in groups 1, 2 and 3, respectively. Median (interquartile ranges) volumes of contrast material, CTDI(vol), DLP and effective dose for low-dose groups 1 and 2 and for standard group 3 were 92.5 (11.3), 75.0 (2.5) and 75.0 (9.0) ml; 8.0 (1.4), 16.8 (4.8) and 48.1 (14.2) mGy; 108.0 (27.3), 246.0 (93.0) and 701.0 (207.8) mGy cm; and 1.5 (0.4), 3.4 (1.3) and 9.8 (2.9) mSv, respectively. A staged coronary CTA protocol with an initial low-dose approach and addition of a standard sequence--should image quality be too low--can lead to a substantial reduction in radiation exposure.
    European Radiology 11/2009; 20(5):1197-206. · 4.34 Impact Factor
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    ABSTRACT: We evaluated radiation exposure and image quality of a new coronary CT angiography protocol, high-pitch spiral acquisition, using dual source CT (DSCT). Coronary CTAwas performed in 25 consecutive patients with a stable heart rate of 60 bpm or less after premedication, using 2 x 128 0.6-mm sections, 38.4-mm collimation width and 0.28-s rotation time. Tube settings were 100 kV/320 mAs and 120 kV/400 mAs for patients below and above 100-kg weight, respectively. Data acquisition was prospectively ECG-triggered at 60% of the R-R interval using a pitch of 3.2 (3.4 for the last 10 patients). Images were reconstructed with 75-ms temporal resolution, 0.6-mm slice thickness and 0.3-mm increment. Image quality was evaluated using a four-point scale (1 = excellent, 4 = unevaluable). Mean range of data acquisition was 113 +/- 22 mm, mean duration was 268 +/- 23 ms. Of 363 coronary artery segments, 327 had an image quality score of 1, and only 2 segments were rated as "unevaluable". Mean dose-length product (DLP) was 71 +/- 23 mGy cm, mean effective dose was 1.0 +/- 0.3 mSv (range 0.78-2.1 mSv). For 21 patients with a body weight below 100 kg, mean DLP was 63 +/- 5 mGy cm (0.88 +/- 0.07 mSv; range 0.78-0.97 mSv). Prospectively ECGtriggered high-pitch spiral CT acquisition provides high and stable image quality at very low radiation dose.
    European Radiology 09/2009; 19(11):2576-83. · 4.34 Impact Factor
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    ABSTRACT: Despite clinically available high-resolution CT, the detection and classification of gallstones remains a challenge in some cases. This pilot study examines whether noninvasive characterization of gallstones in vitro is possible using dual-energy analysis (DECT) of dual source CT datasets. A total of 43 gallstones (0.4 - 1.5 cm) were examined at 80 kV, 140 kV and in the dual-energy mode. The monoenergetic datasets were examined by two independent examiners and classified as calcium, cholesterol or pigment stones. The results were compared with the pathological classification as the clinical gold standard. After creating reference images for each group via dual-energy analysis, the classification was repeated and compared with the gold standard again. Using the monoenergetic analysis at 80 kV, the sensitivity and specificity were 100 / 84 % and 100 / 88 % for calcium stones. For cholesterol stones the values were 54 / 89 % and 54 / 85 % and for pigment stones 70 / 80 % for both examiners. At 140 kV, the sensitivity and specificity for calcium stones were 100 / 84 % for both examiners, 46 / 92 % for cholesterol stones for both examiners and the sensitivity and specificity were 80 / 75 % and 80 / 80 % for pigment stones. Using the reference images established by DECT, both examiners were able to correctly classify all gallstones. The present data indicates that DECT is able to correctly classify Gallstones according to the clinical gold standard in vitro. Clinical studies have to demonstrate whether these results lead to optimized clinical decision making.
    RöFo - Fortschritte auf dem Gebiet der R 05/2009; 181(4):367-73. · 2.76 Impact Factor
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    ABSTRACT: Spiral CT angiography (CTA) of the coronaries using low-pitch scanning and ECG-gated image reconstruction is a robust method for detecting or excluding relevant coronary plaque. However, the resulting dose exposure is considerable. The aim of the present study was to evaluate image quality and artifacts as well as to record dose values for sequential coronary CTA using a 128-slice scanner with a temporal resolution of 150 ms. 20 patients with a regular heart rate and without contraindications for oral/I.V. beta blockers, who were referred for CTA of the coronaries for exclusion or detection of relevant plaques, were examined by sequential CTA with the following parameters: 120 kV, 200 ref mAs, collimation 2 x 64 x 0.6, table feed of 34.5 mm at a detector width of 38.4 mm. A total acquisition time of 380 ms per table position allowed for mild shifting of the reconstruction window within the cardiac cycle of +/- 5 %. 50 ml of contrast agent were injected at 5 ml/s followed by a 50 ml split bolus (20 % contrast). The individual start delay was determined by a test bolus scan (10 ml contrast + 50 ml saline flush at 5 ml/s). The image quality for each segment, coronary artery, and patient was determined on a 4-point scale. Dose values were estimated based on the individual dose length product as provided by the scanner's patient protocol. Artifacts were evaluated to determine the cause (calcium vs. motion). All patients received beta blocker pretreatment. The mean heart rate was 62 +/- 5 beats/min. 5 % (13 / 286) of all segments in 5 / 20 patients were rated as non-diagnostic. The mean dose length product was 213 mGy x cm, and the mean effective dose was 3.6 mSv. Calcifications were the major cause of non-diagnostic images. However breathing or other motion artifacts occurred as well. In select patients with effective heart rate control and thorough instruction for breath hold compliance, sequential CTA of the coronaries using a 128-slice scanner with a temporal resolution of 150 ms is technically feasible. The resulting effective dose values are clearly below those of spiral coronary CT scans.
    RöFo - Fortschritte auf dem Gebiet der R 05/2009; 181(4):332-8. · 2.76 Impact Factor
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    ABSTRACT: As a result of rapid advances in CT technology, including dual source CT, cardiac CT exams at high heart rates are feasible, making pediatric cardiac CT in congenital heart disease possible. Dose concerns and patient size variability make general recommendations difficult. The aim of this study was to investigate which scanner settings are suitable for multiple weight groups to provide dose-optimized scanning. All 12 patients underwent a contrast-enhanced gated dual source CT exam. A maximum of 2 ml/kg body weight or 60 ml contrast was applied. Scanner settings at 80 and 120 kV, as well as weight-adapted mAs settings were used in an iterative fashion. Datasets were assessed for image quality and dose-optimized scan parameters were established via class comparison. In a final step a table was created as a recommendation for cardiac CT in children corresponding to their body weight. Strategies for optimized contrast application with hand vs. manual injection were explored. In all children diagnostic image quality was obtained. In children < 60 kg, 80 kV can be used, in all others 100 kV is sufficient. The eff. mAs varied from 362 mAs to 30 mAs depending on body weight. Retrospectively a significant dose reduction would have been possible in 6 / 12 patients. Cardiac CT can be performed between 0.6 and 3.2 mSv in a pediatric population. The present study shows that dual source cardiac CT is a potential diagnostic alternative in children with congenital heart disease without excessive radiation exposure or contrast media application.
    RöFo - Fortschritte auf dem Gebiet der R 04/2009; 181(4):339-48. · 2.76 Impact Factor
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    ABSTRACT: Due to the technical advance of multislice cardiac CT and the recently introduced dual source CT, the acquisition times for cardiac CT exams are < 10 sec. At the same time the assessment of left ventricular function is possible. However, in many patients a complete right ventricular outwash is noted, leading to insufficient septal delineation. Studies were able to demonstrate that contrast media (CM) mixed in the saline chaser bolus is sufficient for significantly better visualization of septal structures. The aim of this study was to investigate whether this dual flow concept works as well for 64-slice and dual source CT angiography using only 20 % CM in the saline chaser bolus. 97 patients were included in this prospective study. 47 patients underwent 64-slice CT coronary angiography. 80 cc were administered at 5 cc/sec as the main bolus followed by a 50 cc saline chaser bolus containing 20 % contrast media. The other 50 patients were examined using dual source CT. They received a CM protocol adapted for the scan time with the identical saline/CM chaser bolus. The datasets were quantitatively examined in defined ROIs along the septum and in the right ventricle with respect to the density. The septal delineation was qualitatively analyzed and both groups were compared. In a final step the density was measured in the proximal and distal RCA as well as in the LAD and also compared. Using the protocol adapted for the scan time, significantly less CM was used. No significant difference was able to be found regarding the septal delineation or coronary enhancement. The study shows that the dual flow concept allows for robust septal delineation regardless of the CM injection protocol used as long as a 20 % saline chaser bolus is used. A CM protocol adapted for the scan time also leads to significant CM reduction at equal image quality.
    RöFo - Fortschritte auf dem Gebiet der R 04/2009; 181(4):324-31. · 2.76 Impact Factor
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    ABSTRACT: Assessment of coronary artery stents using computed tomographic angiography has been challenging. The technology of dual-source computed tomography (DSCT) provides higher temporal resolution that may allow more accurate evaluation of coronary stents. This study evaluated the accuracy of DSCT for the assessment of coronary artery in-stent restenosis. A total of 112 patients with 150 previously implanted coronary stents (diameter > or = 3.0 mm) were examined using DSCT (Definition; Siemens Medical Solutions, Forchheim, Germany) before conventional coronary angiography. Each stent was classified as assessable or not assessable. All assessable stents were further classified for the absence or presence of in-stent restenosis (>50% diameter reduction) using DSCT, and results were compared with those using quantitative coronary angiography. Mean stent diameter was 3.27 +/- 0.35 mm. Fifteen of 80 stents (19%) with a diameter of 3.0 mm were not assessable, and all 70 stents >3.0 mm were assessable. DSCT correctly identified 16 of 19 in-stent restenoses in 135 assessable stents, as well as the absence of in-stent restenosis in 110 of 116 stents (sensitivity 84%, specificity 95%, positive predictive value 73%, and negative predictive value 97% in assessable stents). In conclusion, DSCT may be useful to noninvasively detect in-stent restenosis, especially in stents with a relatively large diameter.
    The American journal of cardiology 03/2009; 103(6):812-7. · 3.58 Impact Factor
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    ABSTRACT: Coronary CT angiography allows high-quality imaging of the coronary arteries when state-of-the-art CT systems are used. However, radiation exposure has been a concern. We describe a new scan mode that uses a very high-pitch spiral acquisition, "Flash Spiral," which has been developed specifically for low-dose imaging with dual-source CT. The scan mode uses a pitch of 3.2 to acquire a spiral CT data set, while covering the entire volume of the heart in one cardiac cycle. Data acquisition is prospectively triggered by the electrocardiogram and starts in late systole to be completed within one cardiac cycle. Images are reconstructed with a temporal resolution that corresponds to one-quarter of the gantry rotation time. Throughout the data set, subsequent images are reconstructed at later time instants in the cardiac cycle. In a patient with a heart rate of 49 beats/min, the Flash Spiral scan mode was used with a first-generation dual-source CT system and allowed artifact-free visualization of the coronary arteries with a radiation exposure of 1.7 mSv for a 12-cm scan range at 120 kVp tube voltage.
    Journal of cardiovascular computed tomography 01/2009; 3(2):117-21. · 2.55 Impact Factor
  • Rofo-fortschritte Auf Dem Gebiet Der Rontgenstrahlen Und Der Bildgebenden Verfahren - ROFO-FORTSCHR RONTGENSTRAHL. 01/2009; 181.

Publication Stats

6k Citations
488.29 Total Impact Points

Institutions

  • 2008–2011
    • Friedrich-Alexander Universität Erlangen-Nürnberg
      Erlangen, Bavaria, Germany
    • Thurgau Hospital AG
      Frauenfeld, Thurgau, Switzerland
  • 2006–2011
    • Universitätsklinikum Erlangen
      Erlangen, Bavaria, Germany
    • RWTH Aachen University
      • Klinik für Diagnostische und Interventionelle Radiologie
      Aachen, North Rhine-Westphalia, Germany
  • 1997–2008
    • University of Tuebingen
      • • Department of Internal Medicine
      • • Institute for Physiology
      Tübingen, Baden-Wuerttemberg, Germany
  • 2007
    • HELIOS Klinikum Berlin-Buch
      • Institut für Röntgendiagnostik
      Berlín, Berlin, Germany
    • Asklepios Klinik Barmbek
      Hamburg, Hamburg, Germany
  • 2003–2006
    • Siemens
      • Siemens Medical Solutions
      München, Bavaria, Germany
  • 2002–2006
    • Universitätsklinikum Tübingen
      • Division of Diagnostic and Interventional Radiology
      Tübingen, Baden-Württemberg, Germany
  • 2001
    • University of Bristol
      Bristol, England, United Kingdom