The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform

Guy Friedrich - One of the best experts on this subject based on the ideXlab platform.

Florian Wolf - One of the best experts on this subject based on the ideXlab platform.

Robert Goetti - One of the best experts on this subject based on the ideXlab platform.

  • CT perfusion of renal cell carcinoma: Impact of volume coverage on quantitative analysis
    Investigative Radiology, 2012
    Co-Authors: Caecilia S. Reiner, Thomas Pfammatter, Tullio Sulser, Robert Goetti, Ernst Klotz, Daniel Eberli, Thomas Frauenfelder, Andreas Boss, Holger Moch, Hatem Alkadhi
    Abstract:

    Purpose: To assess the feasibility, image quality, and radiation dose of computed tomography (CT) renal perfusion imaging in the adaptive 4-dimensional (4D)-Spiral Mode in patients with renal cell carcinoma (RCC), and to compare quantitative measurements between 2-dimensional regions-of-interest (2D-ROI) and 3-dimensional volumes-of-interest (3D-VOI). Materials and Methods: Twenty-one patients (13 male; age, 67.4 +/- 9.5 years) with 24 histologically proven RCCs underwent CT perfusion imaging (100 kV, 100 mAs/rotation, scan range 10 cm, examination time 40.17 seconds) in a 4D-Spiral Mode with dual-source 128-slice CT. The ability to suspend respiration during CT perfusion imaging was visually monitored. Two independent readers assessed motion artifacts of CT perfusion imaging data sets on a 4-point scale before and after automated motion correction. Qualitative (enhancement pattern) and quantitative perfusion analysis (blood flow [BF], blood volume [BV], flow extraction product [KTrans]) were performed in the tumor and in healthy ipsi- and contralateral renal cortex applying the maximum-slope and a modified Patlak approach for quantitative analysis in 2D-ROI and 3D-VOI, the latter including the entire RCCs. Results: Of the 21 patients, 8 (38%) could suspend respiration throughout the perfusion scan. Of 21 RCCs, 18 (86%) were completely included in the scan range. Motion artifacts were significantly reduced after automated motion correction (P = 0.001). All 24 RCCs could be included in the qualitative perfusion analysis, and 22 of 24 (92%) were eligible for quantitative perfusion analysis. Enhancement was homogenous in 4 (17%), peripheral in 4 (17%), and heterogeneous in 16 (66%) tumors (good interobserver agreement, Kappa = 0.74). A high correlation was found between the 2 readers regarding quantitative perfusion parameters (r = 0.93–0.94, P = 0.01). Quantitative measurements in 3D-VOIs revealed significantly lower BV, BF, and KTrans in RCCs than in normal renal cortex (P < 0.001). In solid tumor periphery, BV was similar to the renal cortex (P = 0.299), while BF and KTrans were significantly lower (P < 0.01 and < 0.001) in tumor tissue. Comparison of tumor measurements in 3D-VOIs with those obtained from 2D-ROIs revealed considerable differences in perfusion parameters beyond the 95% confidence limits in 46% to 68% of the tumors. KTrans was significantly higher in the contralateral than in healthy ipsilateral renal cortex (P < 0.01). Estimated effective radiation dose of the CT perfusion protocol was 16.3 mSv. Conclusion: CT perfusion imaging using an adaptive 4D-Spiral Mode is feasible and enables, after use of automated motion correction, the reliable analysis of renal perfusion in patients with RCCs. Considerable tumor heterogeneity was found, with differences in perfusion parameters between 2D-ROI and 3D-VOI analysis, reinforcing the use of volumetric techniques for perfusion imaging and analysis. Differences between ipsi- and contralateral healthy renal cortex KTrans suggest a compensatory increase in glomerular filtration rate in the healthy contralateral kidney.

  • Coronary artery stent imaging with 128-slice dual-source CT using high-pitch Spiral acquisition in a cardiac phantom: comparison with the sequential and low-pitch Spiral Mode
    European Radiology, 2010
    Co-Authors: Florian Wolf, Robert Goetti, Sebastian Leschka, Christian Loewe, Peter Homolka, Christina Plank, Ruediger Schernthaner, Dominik Bercaczy, Johannes Lammer, Guy Friedrich
    Abstract:

    Objective To evaluate coronary stents in vitro using 128-slice-dual-source computed tomography (CT). Methods Twelve different coronary stents placed in a non-moving cardiac/chest phantom were examined by 128-slice dual-source CT using three CT protocols [high-pitch Spiral (HPS), sequential (SEQ) and conventional Spiral (SPIR)]. Artificial in-stent lumen narrowing (ALN), visible inner stent area (VIA), artificial in-stent lumen attenuation (ALA) in percent, image noise inside/outside the stent and CTDIvol were measured. Results Mean ALN was 46% for HPS, 44% for SEQ and 47% for SPIR without significant difference. Mean VIA was similar with 31% for HPS, 30% for SEQ and 33% for SPIR. Mean ALA was, at 5% for HPS, significantly lower compared with −11% for SPIR ( p  = 0.024), but not different from SEQ with −1%. Mean image noise was significantly higher for HPS compared with SEQ and SPIR inside and outside the stent ( p  

  • Quantitative computed tomography liver perfusion imaging using dynamic Spiral scanning with variable pitch: feasibility and initial results in patients with cancer metastases.
    Investigative Radiology, 2010
    Co-Authors: Robert Goetti, Ernst Klotz, Sebastian Leschka, Lotus Desbiolles, Panagiotis Samaras, Lotta Von Boehmer, Frank Stenner, Cäcilia Reiner, Paul Stolzmann, Hans Scheffel
    Abstract:

    Purpose:To assess the feasibility and image quality of computed tomography (CT) liver perfusion imaging using an adaptive 4D Spiral-Mode, developed to extend the z-axis coverage, and to report initial qualitative and quantitative results in patients with cancer metastases.Materials and Methods:A tot

  • coronary artery stent imaging with 128 slice dual source ct using high pitch Spiral acquisition in a cardiac phantom comparison with the sequential and low pitch Spiral Mode
    European Radiology, 2010
    Co-Authors: Florian Wolf, Robert Goetti, Sebastian Leschka, Christian Loewe, Peter Homolka, Christina Plank, Ruediger Schernthaner, Dominik Bercaczy, Johannes Lammer, Guy Friedrich
    Abstract:

    Objective To evaluate coronary stents in vitro using 128-slice-dual-source computed tomography (CT).

Chen Yundai - One of the best experts on this subject based on the ideXlab platform.

  • DIAGNOSTIC ACCURACY OF 128-SLICE DUAL-SOURCE CT USING HIGH-PITCH Spiral Mode IN ASSESSMENT OF CORONARY ARTERY STENT IMAGING COMPARISON WITH INVASIVE CORONARY ANGIOGRAPHY
    Heart, 2020
    Co-Authors: Chen Yundai
    Abstract:

    Objectives To investigate the diagnostic accuracy of 128-slice dual-source CT (DSCT) using high–pitch Spiral Mode in assessment of coronary stent imaging comparison with invasive coronary angiography (CA). Methods We conducted a prospective study on patients with previous stent implantation who was scheduled for coronary angiography, received 128-slice dual-source CT using three CT protocols (high-pitch Spiral (HPS), sequential (SEQ), low-pitch Spiral (LPS)). Two reviewers scored coronary stent image quality, evaluated lumen blinded to the result of CA and calculated the radiation dose. Results One hundreds and sixty-five patients with total 256 stents were evaluated. There were no significant differences in image quality scores between three groups. Image quality was not influenced by age, body mass index or heart rate in any groups, but heart rate variability and an impact on the image quality of SEQ and HPS group. Per-stent based sensitivity, specificity, and positive and negative predictive value in assessment of stent restenosis were 100%, 97.1%, 83.3%, 100%, respectively in the HPS CT angiography groups, 92.3%, 95.9%, 80%, 98.6%, respectively in the SEQ groups and 93.3%, 97.3%, 87.5%, 98.6%, respectively in the LPS groups. The mean effective dose in three groups were 1.0±0.5 mSv (HPS), 3.0±1.4 mSv(SEQ) and 13.0±5.4 mSv(LPS), respectively. The effective dose in HPS group is significant less than SEQ and LPS group (p Conclusions As a gold standard of CA, 128-slice DSCT using HPS Mode has a similar performance in assessing coronary stent patency comparison with SEQ and LPS Mode, but a lower effective dose in selected patients with regular heart rates≤70 bpm.

  • accuracy of 128 slice dual source ct using high pitch Spiral Mode for the assessment of coronary stents first in vivo experience
    European Journal of Radiology, 2013
    Co-Authors: Yang Junjie, Zhou Ying, Wang Qi, Jin Qinhua, Chen Yundai
    Abstract:

    Abstract Objective To investigate the accuracy of 128-slice dual-source CT using high-pitch Spiral Mode (HPS) for the assessment of coronary stents. Methods We conducted a prospective study on patients with previous stent implantation due to recurred suspicious symptoms of angina with positive findings at stress testing scheduled for coronary angiography (CA), while dual source computed tomography (DSCT) examinations were randomly done by one of the three different scan Modes [HPS, sequential Mode (SEQ), low-pitch Spiral Mode (LPS)] one week before CA examinations. The image quality, radiation dose and stent patency of DSCT were evaluated blinded to the results of CA. Results 180 patients with total 256 stents were enrolled in this study. There was no significant difference on the image quality of DSCT by HPS (1.4 ± 0.5), SEQ (1.5 ± 0.5) and LPS (1.3 ± 0.6) ( P  > 0.05). The noise of images reconstructed with B26f kernel in HPS is significantly increased than in SEQ/LPS ( P P  > 0.05). Heart rate (HR) variability had a slight impact on the image quality for HPS ( P P  > 0.05). In the assessment of stent restenosis compared with CA on per-stent basis, there was no significant difference on sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of DSCT using HPS (100%, 97.1%, 83.3%, 100%), LPS (92.3%, 95.9%, 80%, 98.6%) and SEQ (93.3%, 97.3%, 87.5%, 98.6%) ( P  > 0.05). The effective dose of DSCT by HPS (1.0 ± 0.5 mSv) is significant less than that by SEQ (3.0 ± 1.4 mSv) or LPS (13.0 ± 5.4 mSv) ( P Conclusions DSCT using HPS provides good diagnostic accuracy on coronary stent patency compared with CA, similar to that by SEQ/LPS, whereas with lower effective dose in patients with HR lower than 65 bpm.

J.j.h. Wang - One of the best experts on this subject based on the ideXlab platform.

  • The physical foundation, developmental history, and ultra-wideband performance of SMM (Spiral-Mode microstrip) antennas
    2005 IEEE Antennas and Propagation Society International Symposium, 2005
    Co-Authors: J.j.h. Wang
    Abstract:

    The paper reviews the physical foundation, developmental history, and ultra-wideband (UWB) performance of the SMM (Spiral-Mode microstrip) antenna (Wang, J.J.H. and Tripp, V.K., 1996; Wang, 1997; Wang et al., 2005). The paper is inspired by the recent article on self-complementary (SC) antennas by Y.Mushiake (see IEEE Antennas and Propag. Magazine, vol.46, 2004; IEEE Antennas and Propag. Symp. Dig., 2003), and shares with it considerable physical insight and technical relevance. However, it is worth pointing out that an SC structure offers only a real constant impedance, not necessarily a useful radiation pattern; both are needed to qualify as a UWB, or even a frequency-independent (FI) antenna, and this is where the geometries of Spiral, log-periodic (LP), etc. come into play. Additionally, for practical reasons it is often necessary that the antenna be amenable to conformal mounting on a platform; this can be accomplished by the SMM antenna.

  • Ultra-wideband omnidirectional conformable low-profile Mode-0 Spiral-Mode microstrip (SMM) antenna
    2005 IEEE Antennas and Propagation Society International Symposium, 2005
    Co-Authors: J.j.h. Wang, C.j. Stevens, D.j. Triplett
    Abstract:

    An ultra-wideband low-profile platform-conformable omnidirectional antenna based on the Mode-0 SMM antenna has been developed. Its 10:1 gain bandwidth is slightly larger than that of the well-established conical monopole, yet its height is less than half that of the monopole. Compared with other well-known low-profile omnidirectional antennas with a gain bandwidth over 2:1, its gain bandwidth of 10:1 is much larger. Further size reduction improvement and performance enhancement for this new antenna are highly feasible.

  • Low-cost wideband 3-bit phased array module using integrated antenna/phase-shifter
    IEEE Antennas and Propagation Society International Symposium. 1998 Digest. Antennas: Gateways to the Global Network. Held in conjunction with: USNC U, 1998
    Co-Authors: J.j.h. Wang, J.k. Tillery, G.t. Thompson, K.e. Bohannan
    Abstract:

    A low-cost wideband 3-bit integrated antenna/phase-shifter array module using the Spiral-Mode microstrip (SMM) antenna has been developed, achieving a 10:1 frequency bandwidth with good, robust measured performance. The estimated cost for the array modules is about $300 each in production quantities of over 20,000 units.

  • Multioctave wideband Mode-0 operation of Spiral-Mode microstrip antennas
    IEEE Antennas and Propagation Society International Symposium 1997. Digest, 1997
    Co-Authors: J.j.h. Wang, J.k. Tillery, M.a. Acree
    Abstract:

    The multioctave impedance and pattern bandwidths ofa 2-arm Spiral Mode microstrip (SMM) antenna with Mode-0 excitation have been demonstrated. Although the amplitude and phase of the radiation patterns are fairly constant throughout a 9.1 (2-18 GHz) band, reactive loading in the SMM antenna structure can modify the pattern shape somewhat. Of practical significance are: (1) possible wideband applications similar to that of a monopole on a finite ground plane and (2) possible low-loss and low-cost applications presently utilizing high-cost and high-loss Mode-2 operations.

  • A frequency-independent phase shifter and low-profile phased array module
    IEEE Antennas and Propagation Society International Symposium 1997. Digest, 1997
    Co-Authors: J.j.h. Wang, J.k. Tillery, K.e. Bohannan, G.t. Thompson
    Abstract:

    We have demonstrated a robust and stable frequency-independent phase-shifting mechanism using the phase pattern of the Spiral antenna, which has been investigated without success with enormous efforts and expense during the past two to three decades. The integration of this phase switching into the low-profile wideband Spiral-Mode microstrip (SMM) antenna readily yields a low-profile phased array module with bandwidth over 10:1. This array module also has potentially lower insertion loss, and higher power-handling capability, than the PIN-diode phase shifters. In addition, this integrated antenna/phase-shifter appears readily applicable to PSK (phase shift keying), including BPSK (binary PSK), QPSK (quadrature PSK), and MPSK (M-ary PSK, N bits) in digital communication systems.