Biomedical subjects

Herbert Bruder

Publications and source records attributed to Herbert Bruder.

10 recordsLinked to original sources

PubMed2006

Material differentiation by dual energy CT: initial experience.

The aim of this study was to assess the feasibility of a differentiation of iodine from other materials and of different body tissues using dual energy CT. Ten patients were scanned on a SOMATOM Definition Dual Source CT (DSCT; Siemens, Forchheim, Germany) system in dual energy mode at tube voltages of 140 and 80 kVp and a ratio of 1:3 between tube currents. Weighted CT Dose Index ranged between 7 and 8 mGy, remaining markedly below reference dose values for the respective body regions. Image post-processing with three-material decomposition was applied to differentiate iodine or collagen from other tissue. The results showed that a differentiation and depiction of contrast material distribution is possible in the brain, the lung, the liver and the kidneys with or without the underlying tissue of the organ. In angiographies, bone structures can be removed from the dataset to ease the evaluation of the vessels. The differentiation of collagen makes it possible to depict tendons and ligaments. Dual energy CT offers a more specific tissue characterization in CT and can improve the assessment of vascular disease. Further studies are required to draw conclusions on the diagnostic value of the individual applications.

Algorithms↗

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

Influence of heart rate and temporal resolution on left-ventricular volumes in cardiac multislice spiral computed tomography: a phantom study.

PURPOSE: We sought to investigate the influence of heart rate and temporal resolution on the assessment of left-ventricular (LV) function with multislice spiral computed tomography (CT). MATERIAL AND METHODS: A dynamic cardiac phantom was repeatedly scanned with a 64-slice CT scanner using a standardized scan protocol (64 x 0.6 mm, 120kV, 770mAs(eff), 330 milliseconds rotation time) at different simulated heart rates, ranging from 40 to 140 beats per minute. Images were reconstructed with an algorithm utilizing data from 1 to 4 cardiac cycles (RR intervals). Ejection fraction (EF), end-systolic, end-diastolic, and stroke volume as well as cardiac output were calculated. Results of the measurements were compared with the real volumes of the phantom. Interscan and intraobserver variability were calculated. RESULTS: Using a monosegmental reconstruction algorithm, the temporal resolution was fixed to 165 milliseconds. With bi-, tri-, and quad-segmental image reconstruction, mean temporal resolution was 128.3 +/- 33.2 milliseconds, 103.3 +/- 49.2 milliseconds, and 87.8 +/- 81.5 milliseconds, respectively. Multisegmental image reconstruction resulted in a lower deviation when comparing measured and real volumes. Using mono-, bi-, tri-, and quad-segmental image reconstruction, the percent deviation between measured and real values for EF was 8.2%, 4.5%, 3.3%, and 3.4%, respectively. Applying multisegmental image reconstruction with improved temporal resolution the deviation decreased with increasing heart rate when compared with mono-segmental image reconstruction. Interscan and intraobserver variability for EF were 1.1% and 1.9%, respectively. CONCLUSION: Enhanced temporal resolution improves the quantification of LV volumes in cardiac multislice spiral CT, enabling reliable assessment of LV volumes even at increased heart rates.

Algorithms↗

PubMed2006

Electrocardiogram-independent image reconstruction in cardiac multidetector computed tomography using retrospective motion synchronization.

OBJECTIVE: We sought to evaluate an electrocardiogram (ECG)-independent image reconstruction technique for coronary computed tomography (CT)-angiography based on cardiac motion. MATERIALS AND METHODS: The raw data from 20 patients was reconstructed with both an ECG-gated algorithm and a motion-dependent algorithm that calculates the cardiac motion-function directly from the CT raw data using a center of mass technique. Images were reconstructed in 5% steps over the R-R interval and the cardiac motion-cycle. For both approaches multiplanar reformations were created and the set of images with the least motion artifacts was used for the evaluation. Motion artifacts affecting the ascending aorta, the left main coronary artery and the entire course of the LAD, LCX and RCA were scored using a 5-point scale. RESULTS: The mean optimal reconstruction window was at 60% of the R-R interval and 30% of the cardiac motion cycle. A total of 73 of 100 vascular regions showed no motion artifacts in ECG-gated images, with the motion-synchronized algorithm only 41 regions were free of motion artifacts. The mean motion-score was 1.4 (+/-0.6) and 2.4 (+/-1.2) respectively (P < 0.05). CONCLUSION: In the currently implemented form the motion-gated algorithm is inferior to ECG-gated image reconstruction but can be used in patients with an incomplete or corrupt ECG-signal.

Algorithms↗

PubMed2005

First performance evaluation of a dual-source CT (DSCT) system.

We present a performance evaluation of a recently introduced dual-source computed tomography (DSCT) system equipped with two X-ray tubes and two corresponding detectors, mounted onto the rotating gantry with an angular offset of 90 degrees . We introduce the system concept and derive its consequences and potential benefits for electrocardiograph [corrected] (ECG)-controlled cardiac CT and for general radiology applications. We evaluate both temporal and spatial resolution by means of phantom scans. We present first patient scans to illustrate the performance of DSCT for ECG-gated cardiac imaging, and we demonstrate first results using a dual-energy acquisition mode. Using ECG-gated single-segment reconstruction, the DSCT system provides 83 ms temporal resolution independent of the patient's heart rate for coronary CT angiography (CTA) and evaluation of basic functional parameters. With dual-segment reconstruction, the mean temporal resolution is 60 ms (minimum temporal resolution 42 ms) for advanced functional evaluation. The z-flying focal spot technique implemented in the evaluated DSCT system allows 0.4 mm cylinders to be resolved at all heart rates. First clinical experience shows a considerably increased robustness for the imaging of patients with high heart rates. As a potential application of the dual-energy acquisition mode, the automatic separation of bones and iodine-filled vessels is demonstrated.

Coronary Angiography↗

PubMed2005

Multi-detector row CT systems and image-reconstruction techniques.

The introduction in 1998 of multi-detector row computed tomography (CT) by the major CT vendors was a milestone with regard to increased scan speed, improved z-axis spatial resolution, and better utilization of the available x-ray power. In this review, the general technical principles of multi-detector row CT are reviewed as they apply to the established four- and eight-section systems, the most recent 16-section scanners, and future generations of multi-detector row CT systems. Clinical examples are used to demonstrate both the potential and the limitations of the different scanner types. When necessary, standard single-section CT is referred to as a common basis and starting point for further developments. Another focus is the increasingly important topic of patient radiation exposure, successful dose management, and strategies for dose reduction. Finally, the evolutionary steps from traditional single-section spiral image-reconstruction algorithms to the most recent approaches toward multisection spiral reconstruction are traced.

Electrocardiography↗

PubMed2004

Weighted FBP--a simple approximate 3D FBP algorithm for multislice spiral CT with good dose usage for arbitrary pitch.

A new 3D reconstruction scheme, weighted filtered backprojection (WFBP) for multirow spiral CT based on an extension of the two-dimensional SMPR algorithm is described and results are presented. In contrast to other 3D algorithms available, the algorithm makes use of all available data for all pitch values. The algorithm is a FBP algorithm: linear convolution of the parallel data along the row direction followed by a 3D backprojection. Data usage for arbitrary pitch values is maintained through a weighting scheme which takes into account redundant data. If proper row weighting is applied, the image quality is superior to the image quality of the SMPR algorithm.

Algorithms↗

PubMed2003

Performance evaluation of a multi-slice CT system with 16-slice detector and increased gantry rotation speed for isotropic submillimeter imaging of the heart.

BACKGROUND: 4-slice CT scanners have shown limitations in clinical application for noninvasive coronary CT angiography (CTA). We evaluate advances in ECG-gated scanning of the heart and the coronary arteries with recently introduced 16-slice CT equipment (SOMATOM Sensation 16, Siemens, Forchheim, Germany). MATERIALS AND METHODS: The technical principles of ECG-gated cardiac scanning, scan parameters, and detector design of the new scanner are presented. ECG-gated scan and image reconstruction techniques and ECG-controlled dose modulation ("ECG pulsing") for a reduction of the patient dose are described, key parameters for image quality and simulation results presented, and phantom studies and initial patient experience discussed. The impact of reduced gantry rotation time (0.42 s) on temporal resolution and initial estimations of the patient dose are presented. RESULTS: Extensions of ECG-gated reconstruction algorithms used for 4-slice CT provide adequate image quality for up to 16 slices. For each detector collimation different slice widths are available for retrospective reconstruction with well-defined slice sensitivity profiles (SSPs). For coronary CTA the heart can be covered with 0.75 mm collimation within a 20-s breathhold. The best possible spatial resolution is 0.5 x 0.5 x 0.6 mm. For 0.42 s gantry rotation time, temporal resolution reaches its optimum (105 ms) at a heart rate of 81 bpm. Effective patient dose for coronary CTA is 4-5 mSv using ECG-pulsed acquisition. CONCLUSION: The clinical performance of coronary CTA by means of spatial resolution, temporal resolution and scan time is substantially improved with the evaluated 16-slice CT scanner. Also, display of smaller coronary segments and instent visualization are substantially improved.

Algorithms↗

PubMed2003

Advances in cardiac imaging with 16-section CT systems.

RATIONALE AND OBJECTIVES: The authors present advances in electrocardiographically (ECG) gated cardiac spiral scanning with recently introduced 16-section computed tomographic (CT) equipment. MATERIALS AND METHODS: The authors discuss the technical principles of ECG-gated cardiac scanning. They give an overview on system properties and on the detector design. They describe ECG-gated scan- and image-reconstruction techniques and ECG-controlled dose modulation ("ECG pulsing") for a reduction of the patient dose. They discuss key parameters for image quality and present simulation and phantom studies and they give preliminary values for the patient dose. RESULTS: An extension of the adaptive cardiac volume reconstruction for ECG-gated spiral CT provides adequate image quality for up to 16 sections. With the smallest reconstructed section width (about 0.83 mm) and overlapping image reconstruction, cylindrical holes 0.6-0.7 mm in diameter can be resolved in a transverse resolution phantom independent of the heart rate. For coronary CT angiography, the influence of transverse resolution is most pronounced for coronary segments that are only slightly tilted relative to the scan plane. In this case, visualization of stents and plaques is considerably improved with 1.0-mm or smaller section width. For 0.42-second gantry rotation time, temporal resolution reaches its optimum (105 msec) at a heart rate of 81 beats per minute. Effective patient dose for the standard protocols recommended by the manufacturer ranges from 0.45 mSv (male) for ECG-triggered calcium scoring to 7.1 mSv (male) for high-resolution ECG-gated coronary CT angiography. With ECG pulsing, the dose is reduced by 30%-50% depending on the patient's heart rate. CONCLUSION: Clinical experience will be needed to evaluate fully the potential of 16-section technology for cardiac imaging.

Artifacts↗

PubMed2002

Segmented multiple plane reconstruction: a novel approximate reconstruction scheme for multi-slice spiral CT.

A new reconstruction scheme for multi-row spiral CT is described and results are presented. The spiral path is decomposed into small, overlapping segments which are used for a separate convolution and backprojection yielding a stack of segment images which contain only projection data of a partial scan (typically in the range of 20). These segment image stacks are, in a second step, reformatted to the requested image planes. In a third step, the reformatted segment images are added to obtain full images. The main benefit of the proposed algorithm is superior images quality. A 64-row dataset with a cone angle of 6.4 and a table feed of 80 mm per spiral turn has been reconstructed with excellent image quality. A filter direction for three-dimensional (3D) backprojection algorithms is suggested by investigating the limit where the partial scan size goes to zero.

Algorithms↗