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Matthias Stuber

Publications and source records attributed to Matthias Stuber.

At least 19 recordsLinked to original sources
PubMed2007

Reproducibility of free-breathing cardiovascular magnetic resonance coronary angiography.

OBJECTIVE: Contemporary free-breathing non contrast enhanced cardiovascular magnetic resonance angiography (CMRA) was qualitatively and quantitatively evaluated to ascertain the reproducibility of the method for coronary artery luminal dimension measurements. SUBJECTS AND METHODS: Twenty-two healthy volunteers (mean age 32 +/- 7 years, 12 males) without coronary artery disease were imaged at 2 centers (1 each in Europe and North America) using navigator-gated and corrected SSFP CMRA on a commercial whole body 1.5T System. Repeat images of right (RCA, n = 21), left anterior descending (LAD, n = 14) and left circumflex (LCX, n = 14) coronary arteries were obtained in separate sessions using identical scan protocol and imaging parameters. True visible vessel length, signal-to-noise (SNR), contrast-to-noise ratios (CNR) and the average luminal diameter over the first 4 cm of the vessel were measured. Intra-observer, inter-observer and inter-scan reproducibility of coronary artery luminal diameter were determined using Pearson's correlation, Bland-Altman analysis and intraclass correlation coefficients (ICC). RESULTS: CNR, SNR and the mean length of the RCA, LAD and LCX imaged for original and repeat scans were not significantly different (all p > 0.30). There was a high degree of intra-observer, inter-observer and inter-scan agreements for RCA, LAD and LCX luminal diameter respectively on Bland-Altman and ICC analysis (ICC's for RCA: 0.98. 0.98 and 0.86; LAD: 0.89, 0.89 and 0.63; LCX: 0.95, 0.94 and 0.79). CONCLUSION: In a 2-center study, we demonstrate that free-breathing 3D SSFP CMRA can visualize long continuous segments of coronary vessels with highly reproducible measurements of luminal diameter.

Adult↗
PubMed2006

Subclinical coronary and aortic atherosclerosis detected by magnetic resonance imaging in type 1 diabetes with and without diabetic nephropathy.

BACKGROUND: Patients with type 1 diabetes and nephropathy maintain an excess cardiovascular mortality compared with diabetic patients with normoalbuminuria. We sought to evaluate coronary and aortic atherosclerosis in a cohort of asymptomatic type 1 diabetic patients with and without diabetic nephropathy using cardiovascular magnetic resonance imaging. METHODS AND RESULTS: In a cross-sectional study, 136 subjects with long-standing type 1 diabetes without symptoms or history of cardiovascular disease, including 63 patients (46%) with nephropathy and 73 patients with normoalbuminuria, underwent cardiovascular magnetic resonance imaging. All subjects underwent cardiac exercise testing and noninvasive tests for peripheral artery disease and autonomic neuropathy. Coronary artery stenoses were identified in 10% of subjects with nephropathy (versus 0% with normoalbuminuria; P=0.007). Coronary plaque burden, expressed as right coronary artery mean wall thickness (1.7+/-0.3 versus 1.3+/-0.2 mm; P<0.001) and maximum right coronary artery wall thickness (2.2+/-0.5 versus 1.6+/-0.3 mm; P<0.001), was greater in subjects with nephropathy. The prevalence of thoracic (3% versus 0%; P=0.28) and abdominal aortic plaque (22% versus 16%; P=0.7) was similar in both groups. Subjects with and without abdominal aortic plaques had similar coronary plaque burden. CONCLUSIONS: In asymptomatic type 1 diabetes, cardiovascular magnetic resonance imaging reveals greater coronary plaque burden in subjects with nephropathy compared with those with normoalbuminuria.

Adult↗
PubMed2006

MRI visualized neo-intimal dissection and co-localization of novel apoptotic markers apolipoprotein C-1, ceramide and caspase-3 in a Watanabe hyperlipidemic rabbit model.

PURPOSE: Apoptotic arterial wall vascular smooth muscle cell death is known to contribute to plaque vulnerability and rupture. Novel apoptotic markers like apolipoprotein C-I have been implicated in apoptotic human vascular smooth muscle cell death via recruiting a neutral sphingomyelinase (N-SMase)-ceramide pathway. In vivo relevance of these observations in an animal model of plaque rupture has not been shown. METHODS AND RESULTS: Using Watanabe rabbits, we investigated three different groups (group 1, three normal Watanabe rabbits; group 2, six Watanabe rabbits fed with high cholesterol diet for 3 months; group 3, five Watanabe rabbits with similar diet but additional endothelial denudation). We followed progression of atherosclerosis to pharmacologically induced plaque rupture non-invasively using novel 3D magnetic resonance Fast-Field-Echo angiography (TR=7.2, TE=3.6 ms, matrix=512 x 512) and Fast-Spin-Echo vessel wall imaging methods (TR=3 heart beats, TE=10.5 ms, matrix=304 x 304) on 1.5 T MRI. MRI provided excellent image quality with good MRI versus histology vessel wall thickness correlation (r=0.8). In six animals of group 2/3 MRI detected neo-intimal dissection in the abdominal aorta which was accompanied by immuno-histochemical demonstration of concomitant aforementioned novel apoptotic markers, previously implicated in the apoptotic smooth muscle cell death in vitro. CONCLUSIONS: Our studies suggest a potential role for the signal transduction pathway involving apolipoprotein C-I for in vivo apoptosis and atherosclerotic plaque rupture visualized by MRI.

Animals↗
PubMed2006

Selective coronary artery plaque visualization and differentiation by contrast-enhanced inversion prepared MRI.

AIMS: We sought to evaluate the utility of contrast-enhanced coronary magnetic resonance imaging (CE-MRI) for selective visualization and non-invasive differentiation of atherosclerotic coronary plaque in humans. METHODS AND RESULTS: Nine patients with coronary artery disease (CAD) as confirmed by X-ray angiography and multidetector computed tomography (MDCT) were studied by T1-weighted black blood inversion recovery coronary MRI before (N-IR) and after administration of Gd-DTPA (CE-IR). Plaques were categorized as calcified, non-calcified, and mixed based on their Hounsfield number derived from MDCT. With MDCT, a total of 29 plaques were identified, including calcified (n=6), non-calcified (n=6), and mixed calcified/non-calcified (n=17). On N-IR MRI, 26 plaques (90%) were dark, whereas three plaques (two non-calcified and one mixed) appeared bright. On CE-MRI, 13/29 (45%) plaques, 11 of which were mixed, one non-calcified, and one calcified showed contrast uptake. All others remained dark. CONCLUSION: In this preliminary study, we demonstrate the potential utility of CE-IR MRI for selective plaque visualization and differentiation of plaque types. The observed contrast uptake may be associated with endothelial dysfunction, neovascularization, inflammation, and/or fibrosis.

Adult↗
PubMed2006

Improved myocardial tagging contrast in cine balanced SSFP images.

PURPOSE: To improve the tag persistence throughout the whole cardiac cycle by providing a constant tag-contrast throughout all the cardiac phases when using balanced steady-state free precession (bSSFP) imaging. MATERIALS AND METHODS: The flip angles of the imaging radiofrequency pulses were optimized to compensate for the tagging contrast-to-noise ratio (Tag-CNR) fading at later cardiac phases in bSSFP imaging. Complementary spatial modulation of magnetization (CSPAMM) tagging was implemented to improve the Tag-CNR. Numerical simulations were performed to examine the behavior of the Tag-CNR with the proposed method, and to compare the resulting Tag-CNR with that obtained from the more commonly used spoiled gradient echo (SPGR) imaging. A gel phantom, as well as five healthy human volunteers, were scanned on a 1.5T scanner using bSSFP imaging with and without the proposed technique. The phantom was also scanned with SPGR imaging. RESULTS: With the proposed technique, the Tag-CNR remained almost constant during the whole cardiac cycle. Using bSSFP imaging, the Tag-CNR was about double that of SPGR. CONCLUSION: The tag persistence was significantly improved when the proposed method was applied, with better Tag-CNR during the diastolic cardiac phase. The improved Tag-CNR will support automated tagging analysis and quantification methods.

Adult↗
PubMed2006

Real-time imaging of regional myocardial function using fast-SENC.

A technique for fast imaging of regional myocardial function using a spiral acquisition in combination with strain-encoded (SENC) magnetic resonance imaging (MRI) is presented in this paper. This technique, which is termed fast-SENC, enables scan durations as short as a single heartbeat. A reduced field of view (FOV) without foldover artifacts was achieved by localized SENC, which selectively excited the region around the heart. The two images required for SENC imaging (low- and high-tuning) were acquired in an interleaved fashion throughout the cardiac cycle to further shorten the scan time. Regional circumferential contraction and longitudinal shortening of both the left ventricle (LV) and right ventricle (RV) were examined in long- and short-axis views, respectively. The in vivo results obtained from five human subjects and five infarcted dogs are presented. The results of the fast-SENC technique in a single heartbeat acquisition were comparable to those obtained by conventional SENC in a long acquisition time. Therefore, fast-SENC may prove useful for imaging during stress or arrhythmia.

Animals↗
PubMed2006

Correction of through-plane deformation artifacts in stimulated echo acquisition mode cardiac imaging.

Attempts to use a stimulated echo acquisition mode (STEAM) in cardiac imaging are impeded by imaging artifacts that result in signal attenuation and nulling of the cardiac tissue. In this work, we present a method to reduce this artifact by acquiring two sets of stimulated echo images with two different demodulations. The resulting two images are combined to recover the signal loss and weighted to compensate for possible deformation-dependent intensity variation. Numerical simulations were used to validate the theory. Also, the proposed correction method was applied to in vivo imaging of normal volunteers (n = 6) and animal models with induced infarction (n = 3). The results show the ability of the method to recover the lost myocardial signal and generate artifact-free black-blood cardiac images.

Animals↗
PubMed2006

B1-insensitive T2 preparation for improved coronary magnetic resonance angiography at 3 T.

At 3 T, the effective wavelength of the RF field is comparable to the dimension of the human body, resulting in B1 standing wave effects and extra variations in phase. This effect is accompanied by an increase in B0 field inhomogeneity compared to 1.5 T. This combination results in nonuniform magnetization preparation by the composite MLEV weighted T2 preparation (T2 Prep) sequence used for coronary magnetic resonance angiography (MRA). A new adiabatic refocusing T2 Prep sequence is presented in which the magnetization is tipped into the transverse plane with a hard RF pulse and refocused using a pair of adiabatic fast-passage RF pulses. The isochromats are subsequently returned to the longitudinal axis using a hard RF pulse. Numerical simulations predict an excellent suppression of artifacts originating from B1 inhomogeneity while achieving good contrast enhancement between coronary arteries and surrounding tissue. This was confirmed by an in vivo study, in which coronary MR angiograms were obtained without a T2 Prep, with an MLEV weighted T2 Prep and the proposed adiabatic T2 Prep. Improved quantitative and qualitative coronary MRA image measurement was achieved using the adiabatic T2 Prep at 3 T.

Adult↗
PubMed2006

Detection of coronary stenoses with contrast enhanced, three-dimensional free breathing coronary MR angiography using the gadolinium-based intravascular contrast agent gadocoletic acid (B-22956).

PURPOSE: To determine the diagnostic value of the intravascular contrast agent gadocoletic acid (B-22956) in three-dimensional, free breathing coronary magnetic resonance angiography (MRA) for stenosis detection in patients with suspected or known coronary artery disease. METHODS: Eighteen patients underwent three-dimensional, free breathing coronary MRA of the left and right coronary system before and after intravenous application of a single dose of gadocoletic acid (B-22956) using three different dose regimens (group A 0.050 mmol/kg; group B 0.075 mmol/kg; group C 0.100 mmol/kg). Precontrast scanning followed a coronary MRA standard non-contrast T2 preparation/turbo-gradient echo sequence (T2Prep); for postcontrast scanning an inversion-recovery gradient echo sequence was used (real-time navigator correction for both scans). In pre- and postcontrast scans quantitative analysis of coronary MRA data was performed to determine the number of visible side branches, vessel length and vessel sharpness of each of the three coronary arteries (LAD, LCX, RCA). The number of assessable coronary artery segments was determined to calculate sensitivity and specificity for detection of stenosis > or = 50% on a segment-to-segment basis (16-segment-model) in pre- and postcontrast scans with x-ray coronary angiography as the standard of reference. RESULTS: Dose group B (0.075 mmol/kg) was preferable with regard to improvement of MR angiographic parameters: in postcontrast scans all MR angiographic parameters increased significantly except for the number of visible side branches of the left circumflex artery. In addition, assessability of coronary artery segments significantly improved postcontrast in this dose group (67 versus 88%, p < 0.01). Diagnostic performance (sensitivity, specificity, accuracy) was 83, 77 and 78% for precontrast and 86, 95 and 94% for postcontrast scans. CONCLUSIONS: The use of gadocoletic acid (B-22956) results in an improvement of MR angiographic parameters, asssessability of coronary segments and detection of coronary stenoses > or = 50%.

Aged↗
PubMed2006

MRI of coronary vessel walls using radial k-space sampling and steady-state free precession imaging.

OBJECTIVE: The objective of our study was to investigate the impact of radial k-space sampling and steady-state free precession (SSFP) imaging on image quality in MRI of coronary vessel walls. SUBJECTS AND METHODS: Eleven subjects were examined on a 1.5-T MR system using three high-resolution navigator-gated and cardiac-triggered 3D black blood sequences (cartesian gradient-echo [GRE], radial GRE, and radial SSFP) with identical spatial resolution (0.9 x 0.9 x 2.4 mm3). The signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), vessel wall sharpness, and motion artifacts were analyzed. RESULTS: The mean SNR and CNR of the coronary vessel wall were improved using radial imaging and were best using radial k-space sampling combined with SSFP imaging. Vessel border definition was similar for all three sequences. Radial k-space sampling was found to be less sensitive to motion. Consistently good image quality was seen with the radial GRE sequence. CONCLUSION: Radial k-space sampling in MRI of coronary vessel walls resulted in fewer motion artifacts and improved SNR and CNR. The use of SSFP imaging, however, did not result in improved coronary vessel wall visualization.

Adult↗
PubMed2005

Meeting highlights of the 8th Annual Scientific Sessions of the Society For Cardiovascular Magnetic Resonance, January 21 to 23, 2005.

Parallel tracks for clinical scientists, basic scientists, and pediatric imagers was the novel approach taken for the highly successful 8th Annual Scientific Sessions of the Society for Cardiovascular Magnetic Resonance, held in San Francisco, California, January 21 to 23, 2005. Attendees were immersed in information on the latest scientific advances in cardiovascular magnetic resonance (CMR) from mice to man and technological advances from systems with field strengths from 0.5 T to 11.7 T. State-of-the-art applications were reviewed, spanning a wide range from molecular imaging to predicting outcome with CMR in large patient populations.

Adult↗
PubMed2005

Reproducibility of 3D free-breathing magnetic resonance coronary vessel wall imaging.

AIMS: Although the coronary artery vessel wall can be imaged non-invasively using magnetic resonance imaging (MRI), the in vivo reproducibility of wall thickness measures has not been previously investigated. Using a refined magnetization preparation scheme, we sought to assess the reproducibility of three-dimensional (3D) free-breathing black-blood coronary MRI in vivo. METHODS AND RESULTS: MRI vessel wall scans parallel to the right coronary artery (RCA) were obtained in 18 healthy individuals (age range 25-43, six women), with no known history of coronary artery disease, using a 3D dual-inversion navigator-gated black-blood spiral imaging sequence. Vessel wall scans were repeated 1 month later in eight subjects. The visible vessel wall segment and the wall thickness were quantitatively assessed using a semi-automatic tool and the intra-observer, inter-observer, and inter-scan reproducibilities were determined. The average imaged length of the RCA vessel wall was 44.5+/-7 mm. The average wall thickness was 1.6+/-0.2 mm. There was a highly significant intra-observer (r=0.97), inter-observer (r=0.94), and inter-scan (r=0.90) correlation for wall thickness (all P<0.001). There was also a significant agreement for intra-observer, inter-observer, and inter-scan measurements on Bland-Altman analysis. The intra-class correlation coefficients for intra-observer (r=0.97), inter-observer (r=0.92), and inter-scan (r=0.86) analyses were also excellent. CONCLUSION: The use of black-blood free-breathing 3D MRI in conjunction with semi-automated analysis software allows for reproducible measurements of right coronary arterial vessel-wall thickness. This technique may be well-suited for non-invasive longitudinal studies of coronary atherosclerosis.

Adult↗
PubMed2005

Artifact-free coronary magnetic resonance angiography and coronary vessel wall imaging in the presence of a new, metallic, coronary magnetic resonance imaging stent.

BACKGROUND: Coronary in-stent restenosis cannot be directly assessed by magnetic resonance angiography (MRA) because of the local signal void of currently used stainless steel stents. The aim of this study was to investigate the potential of a new, dedicated, coronary MR imaging (MRI) stent for artifact-free, coronary MRA and in-stent lumen and vessel wall visualization. METHODS AND RESULTS: Fifteen prototype stents were deployed in coronary arteries of 15 healthy swine and investigated with a double-oblique, navigator-gated, free-breathing, T2-prepared, 3D cartesian gradient-echo sequence; a T2-prepared, 3D spiral gradient-echo sequence; and a T2-prepared, 3D steady-state, free-precession coronary MRA sequence. Furthermore, black-blood vessel wall imaging by a dual-inversion-recovery, turbo spin-echo sequence was performed. Artifacts of the stented vessel segment and signal intensities of the coronary vessel lumen inside and outside the stent were assessed. With all investigated sequences, the vessel lumen and wall could be visualized without artifacts, including the stented vessel segment. No signal intensity alterations inside the stent when compared with the vessel lumen outside the stent were found. CONCLUSIONS: The new, coronary MRI stent allows for completely artifact-free coronary MRA and vessel wall imaging.

Animals↗
PubMed2005

Magnetic resonance stress tagging in ischemic heart disease.

High-dose dobutamine magnetic resonance stress testing has been shown to be superior to dobutamine stress echocardiography for diagnosis of coronary artery disease (CAD). We determined the feasibility of quantitative myocardial tagging during low- and high-dose dobutamine stress and tested the ability of global systolic and diastolic quantitative parameters to identify patients with significant CAD. Twenty-five patients suspected of having significant CAD were examined with a standard high-dose dobutamine/atropine stress magnetic resonance protocol (1.5-T scanner, Philips). All patients underwent invasive coronary angiography as the standard of reference for the presence (n = 13) or absence (n = 12) of significant CAD. During low-dose dobutamine stress, systolic (circumferential shortening, systolic rotation, and systolic rotation velocity) and diastolic (velocity of circumferential lengthening and diastolic rotation velocity) parameters changed significantly in patients without CAD (all P < 0.05 vs. rest) but not in patients with CAD. Identification of patients without and with CAD during low-dose stress was possible using the diastolic parameter of "time to peak untwist." At high-dose stress, none of the global systolic or diastolic parameters showed the potential to identify the presence of significant CAD. With myocardial tagging, a quantitative analysis of systolic and diastolic function was feasible during low- and high-dose dobutamine stress. In our study, the diastolic parameter of time to peak untwist as assessed during low-dose dobutamine stress was the most promising global parameter for identification of patients with significant CAD. Thus quantitative myocardial tagging may become a tool that reduces the need for high-dose dobutamine stress.

Adrenergic beta-Agonists↗
PubMed2005

Free-breathing renal magnetic resonance angiography with steady-state free-precession and slab-selective spin inversion combined with radial k-space sampling and water-selective excitation.

The impact of radial k-space sampling and water-selective excitation on a novel navigator-gated cardiac-triggered slab-selective inversion prepared 3D steady-state free-precession (SSFP) renal MR angiography (MRA) sequence was investigated. Renal MRA was performed on a 1.5-T MR system using three inversion prepared SSFP approaches: Cartesian (TR/TE: 5.7/2.8 ms, FA: 85 degrees), radial (TR/TE: 5.5/2.7 ms, FA: 85 degrees) SSFP, and radial SSFP combined with water-selective excitation (TR/TE: 9.9/4.9 ms, FA: 85 degrees). Radial data acquisition lead to significantly reduced motion artifacts (P < 0.05). SNR and CNR were best using Cartesian SSFP (P < 0.05). Vessel sharpness and vessel length were comparable in all sequences. The addition of a water-selective excitation could not improve image quality. In conclusion, radial k-space sampling reduces motion artifacts significantly in slab-selective inversion prepared renal MRA, while SNR and CNR are decreased. The addition of water-selective excitation could not improve the lower CNR in radial scanning.

Adult↗
PubMed2005

Inherently self-calibrating non-Cartesian parallel imaging.

The use of self-calibrating techniques in parallel magnetic resonance imaging eliminates the need for coil sensitivity calibration scans and avoids potential mismatches between calibration scans and subsequent accelerated acquisitions (e.g., as a result of patient motion). Most examples of self-calibrating Cartesian parallel imaging techniques have required the use of modified k-space trajectories that are densely sampled at the center and more sparsely sampled in the periphery. However, spiral and radial trajectories offer inherent self-calibrating characteristics because of their densely sampled center. At no additional cost in acquisition time and with no modification in scanning protocols, in vivo coil sensitivity maps may be extracted from the densely sampled central region of k-space. This work demonstrates the feasibility of self-calibrated spiral and radial parallel imaging using a previously described iterative non-Cartesian sensitivity encoding algorithm.

Algorithms↗
PubMed2005

Spin-labeling coronary MR angiography with steady-state free precession and radial k-space sampling: initial results in healthy volunteers.

The purpose of this study was to prospectively compare free-breathing navigator-gated cardiac-triggered three-dimensional steady-state free precession (SSFP) spin-labeling coronary magnetic resonance (MR) angiography performed by using Cartesian k-space sampling with that performed by using radial k-space sampling. A new dedicated placement of the two-dimensional selective labeling pulse and an individually adjusted labeling delay time approved by the institutional review board were used. In 14 volunteers (eight men, six women; mean age, 28.8 years) who gave informed consent, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), vessel sharpness, vessel length, and subjective image quality were investigated. Differences between groups were analyzed with nonparametric tests (Wilcoxon, Pearson chi2). Radial imaging, as compared with Cartesian imaging, resulted in a significant reduction in the severity of motion artifacts, as well as an increase in SNR (26.9 vs 12.0, P < .05) in the coronary arteries and CNR (23.1 vs 8.8, P < .05) between the coronary arteries and the myocardium. A tendency toward improved vessel sharpness and vessel length was also found with radial imaging. Radial SSFP imaging is a promising technique for spin-labeling coronary MR angiography.

Adult↗