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Biomedical subjects

Katharina Anders

Publications and source records attributed to Katharina Anders.

18 recordsLinked to original sources
PubMed2006

Diagnostic accuracy of noninvasive coronary angiography in patients after bypass surgery using 64-slice spiral computed tomography with 330-ms gantry rotation.

BACKGROUND: Multidetector computed tomographic angiography (MDCT) has been shown to allow detection of coronary artery bypass graft (CABG) occlusions and stenoses. However, the assessment of native coronary arteries in addition to CABG has thus far not been sufficiently validated. METHODS AND RESULTS: Fifty patients with a total of 138 CABG (34 mammary grafts, 3 radial grafts, 101 venous grafts) were investigated by MDCT (0.6-mm collimation, 32 detector rows, 2 focal points, 330-ms rotation) 9 to 252 months (mean, 106 months) after surgery. CABG and all native coronary arteries with a diameter of > 1.5 mm were evaluated for the presence of significant stenoses (> or = 50% diameter reduction). Results were compared with quantitative coronary angiography. By MDCT, all CABG were evaluable and were correctly classified as occluded (n=38) or patent (n=100). Sensitivity for stenosis detection in patent grafts was 100% (16/16) with a specificity of 94% (79/84). For the per-segment evaluation of native coronary arteries and distal runoff vessels, sensitivity in evaluable segments (91%) was 86% (87/101) with a specificity of 76% (354/465). If evaluation was restricted to nongrafted arteries and distal runoff vessels, sensitivity was 86% (38/44) with a specificity of 90% (302/334). On a per-patient basis, classifying patients with at least 1 detected stenosis in a CABG, a distal runoff vessel, or a nongrafted artery or with at least 1 unevaluable segment as "positive," MDCT yielded a sensitivity of 97% (35/36) and specificity of 86% (12/14). CONCLUSIONS: We found that 64-slice MDCT permits the evaluation of bypass grafts and the assessment of the native coronary arteries for the presence of stenosis.

Adult↗
PubMed2006

Assessment of coronary artery stent restenosis by 64-slice multi-detector computed tomography.

AIMS: We investigated the feasibility of assessing coronary artery stent restenosis using a new generation 64-slice multi-detector computed tomography-scanner (MDCT) in comparison to conventional quantitative angiography. METHODS AND RESULTS: MDCT was performed in 64 consecutive patients (mean age 58+/-10 years) with previously implanted coronary artery stents (102 stented lesions: mean stent diameter 3.17+/-0.38 mm). Each stent was classified as 'evaluable' or 'unevaluable', and in evaluable stents, the presence of in-stent restenosis (diameter reduction >50%) was determined visually. Results were verified against invasive, quantitative coronary angiography. Fifty-nine stented lesions (58%) were classified as evaluable in MDCT. The mean diameter of evaluable stents was 3.28+/-0.40 mm, whereas the mean diameter of non-evaluable stents was 3.03+/-0.31 mm (P=0.0002). Overall, six of 12 in-stent restenoses were correctly detected by MDCT [50% sensitivity (confidence interval 22-77%)] and in 51 of 90 lesions, in-stent restenosis was correctly ruled out [57% specificity (46-67%)]. In evaluable stents, six of seven in-stent restenoses were correctly detected, and the absence of in-stent stenosis was correctly identified in 51 of 52 cases [sensitivity 86% (42-99%) and specificity 98% (88-100%)]. CONCLUSION: Stent type and diameter influence evaluability concerning in-stent restenosis by MDCT. The rate of assessable stents is low, but in evaluable stents, accuracy for detection of in-stent restenosis can be high.

Coronary Restenosis↗
PubMed2006

Coronary artery bypass graft (CABG) patency: assessment with high-resolution submillimeter 16-slice multidetector-row computed tomography (MDCT) versus coronary angiography.

PURPOSE: To investigate the ability of 16-slice multidetector-row computed tomography (MDCT) to visualize coronary artery bypass graft (CABG) patency and to detect bypass stenoses. MATERIALS AND METHODS: Thirty-two patients with 94 grafts (20 mammary artery grafts, 74 venous grafts) were investigated by 16-slice MDCT using a scan protocol with 12 x 0.75 mm slice collimation (pitch 0.3), 420 ms rotation time and simultaneous electrocardiogram (ECG)-registration. One hundred milliliters iodinated contrast agent were injected with a delay according to the individually determined contrast agent transit time. Patients with heart rates above 60 bpm received oral beta-blockade. Cross-sectional images with a slice width of 1.0 mm (0.5 mm increment) were reconstructed using an ECG-gated half-scan reconstruction or a multisegment reconstruction algorithm depending on the heart rate. Bypass grafts were evaluated concerning patency and presence of stenoses > or = 50% diameter reduction on cross-sectional images, multiplanar reformations and maximum intensity projections by two independent observers. Results were compared to coronary bypass angiography. RESULTS: Sixteen-slice MDCT results were compared to those of invasive coronary angiography concerning absence or presence of bypass graft occlusion or relevant stenosis > or = 50% lumen reduction. Coronary CT angiography (CTA) permitted detection of bypass occlusion with 100% sensitivity (28/28) and 98% specificity (64/65). Seventy-eight percent (observer 1) and 84% (observer 2) of all patent grafts were found to be evaluable concerning presence or absence of stenosis. In 34 of 40 (observer 1) and 38 of 43 (observer 2) bypass grafts, high-grade stenoses were correctly ruled out (specificity 85% versus 88%, sensitivity 80% and 82%). Yet, if all patients with either unevaluable grafts/graft anastomosis or relevant graft stenosis were excluded, only 8/32 patients (25%) had fully diagnostic "negative" graft-CTA. According to Kappa statistics, agreement between the observers was 1.0 and 0.93 concerning occlusion and relevant stenosis, respectively. CONCLUSION: Sixteen-slice coronary CTA with sub-millimeter spatial resolution and premedication with oral beta-blockade permits non-invasive assessment of coronary artery bypass grafts with decreasing numbers of unevaluable graft segments. However, patient-based analysis reveals that only a relatively small number of patients ("negative" and completely evaluable graft-CTA) truly profits from noninvasive work-up and could be spared invasive angiography.

Adult↗
PubMed2006

Contrast-enhanced coronary artery visualization by dual-source computed tomography--initial experience.

UNLABELLED: Multi-detector computed tomography (CT) scanners, by virtue of their high temporal and spatial resolution, permit imaging of the coronary arteries. However, motion artifacts, especially in patients with higher heart rates, can impair image quality. We thus evaluated the performance of a new dual-source CT (DSCT) with a heart rate independent temporal resolution of 83 ms for the visualization of the coronary arteries in 14 consecutive patients. METHODS: Fourteen patients (mean age 61 years, mean heart rate 71 min(-1)) were studied by DSCT. The system combines two arrays of an X-ray tube plus detector (64 slices) mounted on a single gantry at an angle of 90 degrees With a rotation speed of 330 ms, a temporal resolution of 83 ms (one-quarter rotation) can be achieved independent of heart rate. For data acquisition, intraveous contrast agent was injected at a rate of 5 ml/s. Images were reconstructed with 0.75 slice thickness and 0.5 mm increment. The data sets were evaluated concerning visibility of the coronary arteries and occurrence of motion artifact. RESULTS: Visualization of the coronary arteries was successful in all patients. Most frequently, image reconstruction at 70% of the cardiac cycle provided for optimal image quality (50% of patients). Of a total of 226 coronary artery segments, 222 (98%) were visualized free of motion artifact. In summary, DSCT constitutes a promising new concept for cardiac CT. High and heart rate independent temporal resolution permits imaging of the coronary arteries without motion artifacts in a substantially increased number of patients as compared to earlier scanner generations. Larger and appropriately designed studies will need to determine the method's accuracy for detection of coronary artery stenoses.

Artifacts↗
PubMed2006

New techniques in CT angiography.

Computed tomographic (CT) angiography has been improved significantly with the introduction of four- to 64-section spiral CT scanners, which offer rapid acquisition of isotropic data sets. A variety of techniques have been proposed for postprocessing of the resulting images. The most widely used techniques are multiplanar reformation (MPR), thin-slab maximum intensity projection, and volume rendering. Sophisticated segmentation algorithms, vessel analysis tools based on a centerline approach, and automatic lumen boundary definition are emerging techniques; bone removal with thresholding or subtraction algorithms has been introduced. These techniques increasingly provide a quality of vessel analysis comparable to that achieved with intraarterial three-dimensional rotational angiography. Neurovascular applications for these various image postprocessing methods include steno-occlusive disease, dural sinus thrombosis, vascular malformations, and cerebral aneurysms. However, one should keep in mind the potential pitfalls of these techniques and always double-check the final results with source or MPR imaging.

Algorithms↗
PubMed2005

Usefulness of multidetector row spiral computed tomography with 64- x 0.6-mm collimation and 330-ms rotation for the noninvasive detection of significant coronary artery stenoses.

Eighty-four patients with suspected coronary artery disease were studied to determine the accuracy of noninvasive coronary angiography using a multidetector computed tomographic scanner with 64- x 0.6-mm collimation and 330-ms gantry rotation. All coronary artery segments with a diameter >1.5 mm were assessed with respect to stenoses >50% decreased diameter. Results were compared with quantitative coronary angiographic findings. After exclusion of unevaluable coronary segments (4%), multidetector computed tomography demonstrated a sensitivity of 93%, a specificity of 97%, and a negative predictive value of 100% in a per-segment analysis. In a per-artery analysis, 15 of 336 arteries (4%) were unevaluable. Sensitivity and specificity in evaluable arteries were 95% and 93%, respectively. In a per-patient analysis (81 of 84 patients included), sensitivity and specificity were 96% and 91%, respectively.

Adult↗
PubMed2005

Visualization of coronary artery anomalies by contrast-enhanced multi-detector row spiral computed tomography.

BACKGROUND: We investigated the potential of 16-slice multi-detector row spiral CT (MDCT) with retrospective ECG-gating for evaluation of coronary artery anomalies. METHODS: A total of 35 patients (23 men, 12 women, 19-81 years) in whom anomalous coronary arteries had been detected by invasive coronary angiography underwent MDCT (Sensation 16, Siemens, Germany). During one breathhold, a contrast-enhanced (90 ml, 5 ml/s) volume data set of the heart was acquired (16x0.75mm collimation, gantry rotation 375 ms). Images were reconstructed with a slice thickness of 1.0 mm in 0.5-mm intervals using retrospective ECG-gated reconstruction. The 35 data sets and 80 data sets of patients with angiographically normal coronary anatomy were analysed in random order concerning the origin and course of the coronary arteries. The results were compared to invasive coronary angiography. RESULTS: All patients with coronary artery anomalies and all controls with normal coronary anatomy were identified by MDCT. In addition, the origins and course concerning their anatomical relationship to adjacent cardiac structures were visualized in all patients, including right-sided origin of the left main (n=10), left anterior descending coronary artery (n=4) or left circumflex coronary artery (n=10); left-sided origin of the right coronary artery (n=6); four coronary fistula to the pulmonary artery (two from the left anterior descending, one from the right coronary artery, one from the left main), and one fistula from the circumflex coronary artery to the left atrium CONCLUSIONS: The study demonstrates that MDCT is a reliable noninvasive technique to identify and define anomalous coronary arteries and their course.

Adult↗
PubMed2005

Computed tomography angiography versus digital subtraction angiography in vascular mapping for planning of microsurgical reconstruction of the mandible.

The aim of this work was to compare the potential of computed tomography angiography (CTA) with that of digital subtraction angiography (DSA) in vascular mapping of the external carotid artery (ECA) branches for planning of microvascular reconstructions of the mandible with osteomyocutaneous flaps. In 15 patients CTA and DSA were performed prior to surgery. Selective common carotid angiograms were acquired in two projection for both sides of the neck. Sixteen-slice spiral computed tomography was performed with a dual-phase protocol, using the arterial phase images for 3D CTA reconstruction. Thin-slab maximum intensity projections and volume rendering were employed for postprocessing of CTA data. The detectability of the different ECA branches in CTA and DSA was evaluated by two examiners. No statistically significant differences between CTA and DSA (p=0.097) were found for identifying branches relevant for microsurgery. DSA was superior to CTA if more peripheral ECA branches were included (P=0.030). CTA proved to be a promising alternative to DSA in vascular mapping for planning of microvascular reconstruction of the mandible.

Angiography, Digital Subtraction↗
PubMed2005

[Diagnostic imaging with a 64-slice computed tomography scanner--the first year in clinical routine].

The implementation of 64-slice scanners allows for isotropic imaging with shortened acquisition time. Beam-hardening and spiral artifacts can be reduced by using sophisticated tube technology with so called double-z-sampling. The following article is meant to provide a brief overview concerning substantial changes as they could be witnessed in clinical routine using a 64-slice scanner, with special focus on CT-angiography in general and CT-angiography of the coronaries.

Angiography↗
PubMed2004

Improvement of image quality of multislice spiral CT scans of the head and neck region using a raw data-based multidimensional adaptive filtering (MAF) technique.

The purpose was to evaluate the potential of the multidimensional adaptive filtering (MAF) technique by investigating its effects on image noise and image quality in multislice spiral CT (MSCT) examinations of the head and neck region. Fifty patients with head and neck tumors were examined using MSCT with a high resolution protocol. Reconstructions were performed using dedicated reconstruction software with a standard algorithm both without and with MAF using different modification. In all reconstructions, we measured the noise in seven different anatomical structures. The image quality and image noise were rated on a five-point scale. There was a significant (P<0.05) reduction in mean pixel noise in the reconstructions using MAF in comparison to the standard reconstructions, but there was no significant difference between the different modification fractions. With MAF the mean reduction in noise level was 60%, depending upon body shape and anatomical region. Independently from the used modification fraction, MAF led to a significant (P<0.05) improvement of image quality. In direct comparison of the different filter strength, the optimal image quality was achieved in the investigations with 15% MAF. The use of MAF facilitates the distinction of anatomical and pathological structures from artifacts in the supraclavicular fossae and the upper mediastinum, whereas the image quality of the upper portions of the neck remained unchanged. MAF improved image quality by reducing the noise level and removing noise structures without loss of image sharpness. This technique offers new perspectives to reduce the patient dose.

Adipose Tissue↗
PubMed2003

Detection of calcified and noncalcified coronary atherosclerotic plaque by contrast-enhanced, submillimeter multidetector spiral computed tomography: a segment-based comparison with intravascular ultrasound.

BACKGROUND: We investigated the ability of multidetector spiral computed tomography (MDCT) to detect atherosclerotic plaque in nonstenotic coronary arteries. METHODS AND RESULTS: In 22 patients without significant coronary stenoses, contrast-enhanced MDCT (0.75-mm collimation, 420-ms rotation) and intravascular ultrasound (IVUS) of one coronary artery were performed. A total of 83 coronary segments were imaged by IVUS (left main, 19; left anterior descending, 51; left circumflex, 4; right coronary, 9). MDCT data sets were evaluated for the presence and volume of plaque in the coronary artery segments. Results were compared with IVUS in a blinded fashion. For the detection of segments with any plaque, MDCT had a sensitivity of 82% (41 of 50) and specificity of 88% (29 of 33). For calcified plaque, sensitivity was 94% (33 of 36) and specificity 94% (45 of 47). Coronary segments containing noncalcified plaque were detected with a sensitivity of 78% (35 of 45) and specificity of 87% (33 of 38), but presence of exclusively noncalcified plaque was detected with only 53% sensitivity (8 of 15). If analysis was limited to the 41 proximal segments (segments 1, 5, 6, and 11 according to American Heart Association classification), sensitivity and specificity were 92% and 88% for any plaque, 95% and 91% for calcified plaque, and 91% and 89% for noncalcified plaque. MDCT substantially underestimated plaque volume per segment as compared with IVUS (24+/-35 mm3 versus 43+/-60 mm3, P<0.001). CONCLUSIONS: The results indicate the potential of MDCT to detect coronary atherosclerotic plaque in patients without significant coronary stenoses. However, further improvements in image quality will be necessary to achieve reliable assessment, especially of noncalcified plaque throughout the coronary tree.

Calcinosis↗
PubMed2003

Quantitative parameters of image quality in multidetector spiral computed tomographic coronary imaging with submillimeter collimation.

Multidetector computed tomography (MDCT) permits visualization of the coronary arteries, but limited spatial and temporal resolution can lead to artifacts. We quantitatively evaluated the image quality that can be obtained with the latest generation of MDCT scanners with submillimeter collimation and increased gantry rotation speed. Thirty patients with angiographically proved absence of significant coronary artery stenoses (mean age 56 +/- 13 years, mean heart rate 62 +/- 13 beats/min) were studied by MDCT (12 x 0.75 mm collimation, 420-ms tube rotation, 210-ms temporal resolution, 500 mA, 120 kVp, retrospective electrocardiographic gating). In multiplanar reconstructions of the 4 major coronary arteries (left main, left anterior descending, left circumflex, and right coronary artery), the overall visualized vessel length and the length of segments without motion artifacts were measured. Vessel diameters at 8 predefined locations were measured in MDCT maximum intensity projections and in corresponding invasive angiograms. The mean lengths of visualized coronary arteries were left main 13 +/- 6 mm, left anterior descending 138 +/- 39 mm, left circumflex 84 +/- 34 mm, and right coronary artery 155 +/- 41 mm. On average, 93 +/- 13% of the total visualized vessel length was depicted without motion artifacts (left main 100 +/- 0%, left anterior descending 93 +/- 12%, left circumflex 91 +/- 17%, and right coronary artery 87 +/- 14%). The percentage of vessel length visualized free of motion artifacts was significantly higher in patients with a heart rate </=60 beats/min compared with patients with a heart rate >60 beats/min (96 +/- 8% vs 89 +/- 17%, p <0.05). Vessel diameters in MDCT correlated closely to quantitative coronary angiography (R(2) 0.83 to 0.87). In conclusion, MDCT with submillimeter collimation and improved temporal resolution permits reliable visualization of the vessel lumen and accurate measurements of vessel dimensions.

Analysis of Variance↗
PubMed2003

Detection of coronary artery stenoses with thin-slice multi-detector row spiral computed tomography and multiplanar reconstruction.

BACKGROUND: We analyzed the accuracy of multi-detector row spiral computed tomography (MDCT) using a 16-slice CT scanner with improved spatial and temporal resolution, as well as routine premedication with beta-blockers for detection of coronary stenoses. METHODS AND RESULTS: Seventy-seven patients with suspected coronary disease were studied by MDCT (12x0.75-mm cross-sections, 420 ms rotation, 100 mL contrast agent IV at 5 mL/s). Patients with a heart rate above 60/min received 50 mg atenolol before the scan. In axial MDCT images and multiplanar reconstructions, all coronary arteries and side branches with a diameter of 1.5 mm or more were assessed for the presence of stenoses exceeding 50% diameter reduction. In comparison to invasive coronary angiography, MDCT correctly classified 35 of 41 patients (85%) as having at least 1 coronary stenosis and correctly detected 57 of 78 coronary lesions (73%). After excluding 38 of 308 coronary arteries (left main, left anterior descending, left circumflex, and right coronary artery in 77 patients) classified as unevaluable by MDCT (12%), 57 of 62 lesions were detected, and absence of stenosis was correctly identified in 194 of 208 arteries (sensitivity: 92%; specificity: 93%; accuracy: 93%; positive and negative predictive values: 79% and 97%). CONCLUSIONS: MDCT coronary angiography with improved spatial resolution and premedication with oral beta-blockade permits detection of coronary artery stenoses with high accuracy and a low rate of unevaluable arteries.

Adrenergic beta-Antagonists↗
PubMed2003

Clinical results of minimally invasive coronary angiography using computed tomography.

Fast, high-resolution CT techniques, such as EBCT and MDCT permit imaging of the coronary arteries. Continuous improvements in the capabilities of both technologies for visualization of the coronary lumen and detection of coronary artery stenoses are being made. Image quality currently is not robust enough in all patients to consider non-invasive coronary angiography by EBCT and MDCT a routine clinical tool. In selected patients and carefully performed, however, they show promise as means to exclude the presence of coronary artery stenoses in a non-invasive fashion. This may become a beneficial and important application of these technologies. Other possible applications pertain to smaller patient subsets, such as patients with anomalous coronary arteries, fistulas or aneurysms. The development of techniques to visualize non-calcified plaque is interesting with respect to assessment of coronary risk, but this requires further investigation.

Coronary Angiography↗
PubMed2003

Comparison of image quality in contrast-enhanced coronary-artery visualization by electron beam tomography and retrospectively electrocardiogram-gated multislice spiral computed tomography.

RATIONALE AND OBJECTIVES: To compare the image quality of electron beam tomography (EBT) and multislice spiral CT (MSCT) for coronary artery visualization. MATERIALS AND METHODS: Two groups of 30 patients without coronary stenoses were studied by MSCT (4 x 1 mm collimation) or EBT (3 mm slice thickness). Contrast-to-noise ratio (CNR), overall length of the visualized arteries and vessel length free of motion artifacts were measured. RESULTS: Length of visualized arteries was equal in MSCT and EBT. In EBT, longer segments were depicted free of motion artifacts (MSCT: 73%, EBT: 92% of visualized length, P< 0.001) and CNR was significantly higher than in MSCT (15.4 vs. 9.0; P< 0.001). In both modalities, vessel diameters correlated closely to quantitative coronary angiography. CONCLUSIONS: EBT and MSCT permit reliable coronary artery visualization and measurement of vessel diameters. For the used scan protocol, MSCT images had a lower CNR and were more frequently affected by motion.

Aged↗
PubMed2002

Prolonged infusional topotecan and accelerated hyperfractionated 3d-conformal radiation in patients with newly diagnosed glioblastoma--a phase I study.

PURPOSE: Topotecan has demonstrated exceptional central nervous system penetration as well as radiosensitizing properties in glioblastoma xenografts [Chastagner et al., Int J Radiat Oncol Biol Phy 50: 777-782, 2001]. This phase I trial was performed to determine the maximum tolerated dose and the recommended dose of topotecan continuous infusion administered together with concomitant radiotherapy in patients with glioblastoma. PATIENTS AND METHODS: A total of 20 patients were treated in this trial. Twenty one day topotecan continuous infusion was escalated from 0.3 mg/m2/d in increments of 0.1 mg/m2/d and cohorts of 3-6 patients until maximum tolerated dose was reached; Three-dimensional (3d) conformal radiotherapy was applied concurrently twice daily with a fraction size of 1.75 Gy up to 57.75 Gy total dose. Three additional cycles of maintenance topotecan chemotherapy were scheduled. RESULTS: Fifty-three courses were performed in 5 dose levels (0.3 mg/m2/d: 12 cycles, 0.4 mg/m2/d: 6 cycles, 0.5 mg/m2/d: 10 cycles, 0.6 mg/m2/d: 6 cycles, 0.7 mg/m2/d: 19 cycles). Maximum tolerated dose was reached at dose level 5 (0.7 mg/m2/d), because 3/7 patients suffered from dose limiting toxicity. These were febrile sinusitis, bacterial sepsis and grade 4 thrombocytopenia. Neutropenia of grade 4 was encountered in 2 cycles (0.5 and 0.7 mg/m2/d). Response data were available in 17 patients, 3 of which (18%) achieved partial remission, 12 (71%) stable disease throughout the observation period and 2 (11%) progressive disease. CONCLUSION: The recommended dose for further trials will be 0.6 mg/m2/d topotecan administered as 21 days continuous infusion in combination with accelerated 3d conformal radiation.

Adult↗