Free-breathing renal MR angiography with steady-state free-precession (SSFP) and slab-selective spin inversion: initial results.

BACKGROUND: The aim of our study was the investigation of a novel navigator-gated three-dimensional (3D) steady-state free-precession (SSFP) sequence for free-breathing renal magnetic resonance angiography (MRA) without contrast medium, and to examine the advantage of an additional inversion prepulse for improved contrast. METHODS: Eight healthy volunteers (mean age 29 years) and eight patients (mean age 53 years) were investigated on a 1.5 Tesla MR system (ACS-NT, Philips, Best, The Netherlands). Renal MRA was performed using three navigator-gated free-breathing cardiac-triggered 3D SSFP sequences [repetition time (TR) = 4.4 ms, echo time (TE) = 2.2 ms, flip angle 85 degrees, spatial resolution 1.25 x 1.25 x 4.0 mm(3), scanning time approximately 1 minute 30 seconds]. The same sequence was performed without magnetization preparation, with a non-slab selective and a slab-selective inversion prepulse. Signal-to-noise ratio (SNR), contrast-to-noise (CNR) vessel length, and subjective image quality were compared. RESULTS: Three-dimensional SSFP imaging combined with a slab-selective inversion prepulse enabled selective and high contrast visualization of the renal arteries, including the more distal branches. Standard SSFP imaging without magnetization preparation demonstrated overlay by veins and renal parenchyma. A non-slab-selective prepulse abolished vessel visualization. CNR in SSFP with slab-selective inversion was 43.6 versus 10.6 (SSFP without magnetization preparation) and 0.4 (SSFP with non-slab-selective inversion), P < 0.008. CONCLUSION: Navigator-gated free-breathing cardiac-triggered 3D SSFP imaging combined with a slab-selective inversion prepulse is a novel, fast renal MRA technique without the need for contrast media.

Free-breathing 3D steady-state free precession coronary MR angiography with radial k-space sampling: comparison with cartesian k-space sampling and cartesian gradient-echo coronary MR angiography--pilot study.

The authors compared radial steady-state free precession (SSFP) coronary magnetic resonance (MR) angiography, cartesian k-space sampling SSFP coronary MR angiography, and gradient-echo coronary MR angiography in 16 healthy adults and four pilot study patients. Standard gradient-echo MR imaging with a T2 preparatory pulse and cartesian k-space sampling was the reference technique. Image quality was compared by using subjective motion artifact level and objective contrast-to-noise ratio and vessel sharpness. Radial SSFP, compared with cartesian SSFP and gradient-echo MR angiography, resulted in reduced motion artifacts and superior vessel sharpness. Cartesian SSFP resulted in increased motion artifacts (P <.05). Contrast-to-noise ratio with radial SSFP was lower than that with cartesian SSFP and similar to that with the reference technique. Radial SSFP coronary MR angiography appears preferable because of improved definition of vessel borders.

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.

Assessment of skinfold thickness equations in estimating body composition in children with inflammatory bowel

Introduction: Growth is a central process in paediatrics. Weight and height evaluation are therefore routine exams for every child but in some situation, particularly inflammatory bowel disease (IBD), a wider evaluation of nutritional status needs to be performed. The assessment of body composition is essential in order to maintain acceptable growth using the following techniques: Dual-energy X-ray absorptiometry (DEXA), bio-impedance-analysis (BIA) and anthropometric measurements (skinfold thickness skin), the latter being most easily available and most cost effective. Objectives: To assess the accuracy of skinfold equations in estimating percentage body fat (%BF) in children with inflammatory bowel disease (IBD), compared with assessment of body fat dual energy X-ray absorptiometry (DEXA). Methods: Twenty-one patients (11 females, 10 males; mean age: 14.3 years, range 12 - 16 years) with IBD (Crohn's disease n = 15, ulcerative colitis n = 6)). Estimated%BF was computed using 6 established equations based on the triceps, biceps, subscapular and suprailiac skinfolds (Deurenberg, Weststrate, Slaughter, Durnin & Rahaman, Johnston, Brook) and compared to DEXA. Concordance analysis was performed using Lin's concordance correlation and the Bland-Altman limits of agreement method. Results: Durnin & Rahaman's equation shows a higher Lin's concordance coefficient with a small difference amongst raw values for skinfolds and DEXA compared to the other equations. Correlation coefficient between mean and difference is close to zero with a non-significant Bradley-Blackwood test. Conclusion: Body composition in paediatric IBD patients using the Durnin & Rahaman skinfold-equation adequately reflects values obtained by DEXA.

Étude des sédiments quaternaires, de la molasse et sa tectonique, dans le Grand Lac (Léman) à partir de données sismiques 2D et 3D

RESUME L'Institut de Géophysique de l'Université de Lausanne a développé au cours de ces dernières années un système d'acquisition de sismique réflexion multitrace à haute résolution 2D et 3D. L'objectif de cette thèse était de poursuivre ce développement tout améliorant les connaissances de la géologie sous le lac Léman, en étudiant en particulier la configuration des grands accidents sous-lacustres dans la Molasse (Tertiaire) qui forme l'essentiel du substratum des formations quaternaires. En configuration 2D, notre système permet d'acquérir des profils sismiques avec une distance inter-CDP de 1,25 m. La couverture varie entre 6 et 18 selon le nombre de traces et la distance inter-tir. Le canon à air (15/15 eu. in.), offre une résolution verticale de 1,25 ni et une pénétration maximale de 300 m sous le fond de l'eau. Nous avons acquis au total plus de 400 km de sections 2D dans le Grand Lac et le Haut Lac entre octobre 2000 et juillet 2004. Une campagne de sismique 3D a fourni des données au large d'Evian sur une surface de 442,5 m sur 1450 m, soit 0,64 km2. La navigation ainsi que le positionnement des hydrophones et de la source ont été réalisés avec des GPS différentiels. Nous avons utilisé un traitement sismique conventionnel, sans appliquer d'AGC et en utilisant une migration post-stack. L'interprétation du substratum antéquaternaire est basée sur l'identification des sismofaciès, sur leurs relations avec les unités géologiques adjacentes au lac, ainsi que sur quelques données de forages. Nous obtenons ainsi une carte des unités géologiques dans le Grand Lac. Nous précisons la position du chevauchement subalpin entre la ville de Lausanne, sur la rive nord, et le bassin de Sciez, sur la rive sud. Dans la Molasse de Plateau, nous avons identifié les décrochements de Pontarlier et de St. Cergue ainsi que plusieurs failles non reconnues jusqu'ici. Nous avons cartographié les accidents qui affectent la Molasse subalpine ainsi que le plan de chevauchement du flysch sur la Molasse près de la rive sud du lac. Une nouvelle carte tectonique de la région lémanique a ainsi pu être dressée. L'analyse du substratum ne montre pas de failles suggérant une origine tectonique de la cuvette lémanique. Par contre, nous suggérons que la forme du creusement glaciaire, donc de la forme du lac Léman, a été influencée par la présence de failles dans le substratum antéquaternaire. L'analyse des sédiments quaternaires nous a permis de tracer des cartes des différentes interfaces ou unités qui les composent. La carte du toit du substratum antéquaternaire montre la présence de chenaux d'origine glaciaire dont la profondeur maximale atteint la cote -200 ni. Leur pente est dirigée vers le nord-est, à l'inverse du sens d'écoulement actuel des eaux. Nous expliquons cette observation par l'existence de circulations sous-glaciaires d'eau artésienne. Les sédiments glaciaires dont l'épaisseur maximale atteint 150 ni au centre du lac ont enregistré les différentes récurrences glaciaires. Dans la zone d'Evian, nous mettons en évidence la présence de lentilles de sédiments glaciolacustres perchées sur le flanc de la cuvette lémanique. Nous avons corrélé ces unités avec des données de forage et concluons qu'il s'agit du complexe inférieur de la pile sédimentaire d'Evian. Celui-ci, âgé de plus de 30 000 ans, serait un dépôt de Kame associé à un lac périglaciaire. La sismique réflexion 3D permet de préciser l'orientation de l'alimentation en matériel détritique de l'unité. La finesse des images obtenues nous permet également d'établir quels types d'érosion ont affecté certaines unités. Les sédiments lacustres, dont l'épaisseur maximale imagée atteint plus de 225 m et sans doute 400 ni sous le delta du Rhône, indiquent plusieurs mécanismes de dépôts. A la base, une mégaturbidite, épaisse d'une trentaine de mètres en moyenne, s'étend entre l'embouchure de la Dranse et le delta du Rhône. Au-dessus, la décantation des particules en suspension d'origine biologique et détritique fournit l'essentiel des sédiments. Dans la partie orientale du lac, les apports détritiques du Rhône forment un delta qui prograde vers l'ouest en s'imbriquant avec les sédiments déposés par décantation. La structure superficielle du delta a brutalement évolué, probablement à la suite de l'évènement catastrophique du Tauredunum (563 A.D.). Sa trace probable se marque par la présence d'une surface érosive que nous avons cartographiée. Le delta a ensuite changé de géométrie, avec notamment un déplacement des chenaux sous-lacustres. Sur l'ensemble de nos sections sismiques, nous n'observons aucune faille dans les sédiments quaternaires qui attesterait d'une tectonique postglaciaire du substratum. ABSTRACT During the last few years the institute of Geophysics of the University of Lausanne cleveloped a 2D and 3D high-resolution multichannel seismic reflection acquisition system. The objective of the present work was to carry on this development white improving our knowledge of the geology under Lake Geneva, in particular by studying the configuration of the large accidents affecting the Tertiary Molasse that makes up the basement of most Quaternary deposits. In its 2D configuration, our system makes it possible to acquire seismic profiles with a CDP interval of 1.25 m. The fold varies from 6 to 18 depending on the number of traces and the shooting interval. Our air gun (15/15 cu. in.) provides a vertical resolution of 1.25 m and a maximum penetration depth of approximately 300 m under water bottom. We acquired more than 400 km of 2D sections in the Grand Lac and the Haut Lac between October 2000 and July 2004. A 3D seismic survey off the city of Evian provided data on a surface of 442.5 m x 1450 m (0.64 km2). Ship's navigation as well as hydrophone- and source positioning were carried out with differential GPS. The seismic data were processed following a conventional sequence without .applying AGC and using post-stack migration. The interpretation of the pre-Quaternary substratum is based on sismofacies, on their relationships with terrestrial geological units and on some borehole data. We thus obtained a map of the geological units in the Grand Lac. We defined the location of the subalpine thrust from Lausanne, on the north shore, to the Sciez Basin, on the south shore. Within the Molasse de Plateau, we identified the already know Pontarlier and St Cergue transforms Fault as well as faults. We mapped faults that affect subalpine Molasse as well as the thrust fault plane between alpine flysch and Molasse near the lake's south shore. A new tectonic map of the Lake Geneva region could thus be drawn up. The substratum does not show faults indicating a tectonic origin for the Lake Geneva Basin. However, we suggest that the orientation of glacial erosion, and thus the shape of Lake Geneva, vas influenced by the presence of faults in the pre-Quaternary basement. The analysis of Quaternary sediments enabled us to draw up maps of various discontinuities or internal units. The top pre-Quaternary basement map shows channels of glacial origin, the deepest of them reaching an altitude of 200 m a.s.l. The channel's slopes are directed to the North-East, in opposite direction of the present water flow. We explain this observation by the presence of artesian subglacial water circulation. Glacial sediments, the maximum thickness of which reaches 150 m in the central part of the lake, record several glacial recurrences. In the Evian area, we found lenses of glacio-lacustrine sediments set high up on the flank of the Lake Geneva Bassin. We correlated these units with on-land borehole data and concluded that they represent the lower complex of the Evian sedimentary pile. The lower complex is aider than 30 000 years, and it could be a Kame deposit associated with a periglacial lake. Our 3D seismic reflexion survey enables us to specify the supply direction of detrital material in this unit. With detailed seismic images we established how some units were affected by different erosion types. The lacustrine sediments we imaged in Lake Geneva are thicker than 225 m and 400 m or more Linder the Rhone Delta. They indicate several depositional mechanisms. Their base is a major turbidite, thirty meters thick on average, that spreads between the Dranse mouth and the Rhone delta. Above this unit, settling of suspended biological and detrital particles provides most of the sediments. In the eastern part of the lake, detrital contribution from the Rhone builds a delta that progrades to the west and imbricates with the settling sediments. The shallow structure of the Rhone delta abruptly evolved, probably after the catastrophic Tauredunum event (563 A.D.). It probably coincides with an erosive surface that we mapped. As a result, the delta geometry changed, in particular associated with a displacement of water bottom channels. In all our seismic sections, we do not observe fault in the Quaternary sediments that would attest postglacial tectonic activity in the basement.

Steady State Concentrations of the Enantiomers of Mianserin and Desmethylmianserin in Poor and in Homozygous and Heterozygous Extensive Metabolizers of Debrisoquine.

AB Summary: Steady state concentrations of (S)- and (R)-mianserin and desmethylmianserin were measured in 21 homozygous extensive metabolizers (as determined by genotyping for mutations 3 [or A] and 4 [or B]), in seven heterozygous extensive metabolizers and in one poor metabolizer of debrisoquine, as well as in one patient receiving very high doses of mianserin (360 mg/day) and fluoxetine (160 mg/day), a strong cytochrome P450IID6 inhibitor. The mean dose of mianserin was (mean +/- SD, range: 67 +/- 63, 10 to 360 mg/day). High dispersions of the (S)/(R)-mianserin and desmethylmianserin ratios were observed (mean +/- SD, range: 2.10+/- 1.01, 0.64 to 4.76, and 0.29 +/- 0.14, 0.08 to 0.57, respectively). The highest (S)/(R)-mianserin ratio was calculated for the poor metabolizer (4.76) agreeing with those results of a single-dose study with poor and extensive metabolizers of debrisoquine, in that the cytochrome P450IID6 is probably involved in the metabolism of mianserin with an enantioselectivity for the (S)-enantiomer. Nevertheless, the mean concentration-to-dose ratios for (S)- or (R)-mianserin or desmethylmianserin were not significantly different between homozygous and heterozygous extensive metabolizers, and no particular values were measured in the poor metabolizer nor in the patient receiving fluoxetine. Furthermore, the(S)/(R)-mianserin ratio measured in the PM was only slightly higher than the second highest ratio (3.85) of an homozygous extensive metabolizer, whereas no particular value (2.92) was calculated for the patient taking fluoxetine. Finally, no significant differences in (S)/(R)-mianserin or(S)/(R)-desmethylmianserin were calculated between homozygous and heterozygous extensive metabolizers. Although the number of patients included in this study is too low to allow definite conclusions, the results suggest that the debrisoquine genotype has only a moderate influence on the steady state concentrations of the enantiomers of mianserin and desmethylmianserin. (C) Lippincott-Raven Publishers

Comparison of 3D segmented gradient-echo and steady-state free precession coronary MRI sequences in patients with coronary artery disease.

OBJECTIVE: Our objective was to compare two state-of-the-art coronary MRI (CMRI) sequences with regard to image quality and diagnostic accuracy for the detection of coronary artery disease (CAD). SUBJECTS AND METHODS: Twenty patients with known CAD were examined with a navigator-gated and corrected free-breathing 3D segmented gradient-echo (turbo field-echo) CMRI sequence and a steady-state free precession sequence (balanced turbo field-echo). CMRI was performed in a transverse plane for the left coronary artery and a double-oblique plane for the right coronary artery system. Subjective image quality (1- to 4-point scale, with 1 indicating excellent quality) and objective image quality parameters were independently determined for both sequences. Sensitivity, specificity, and accuracy for the detection of significant (> or = 50% diameter) coronary artery stenoses were determined as defined in invasive catheter X-ray coronary angiography. RESULTS: Subjective image quality was superior for the balanced turbo field-echo approach (1.8 +/- 0.9 vs 2.3 +/- 1.0 for turbo field-echo; p < 0.001). Vessel sharpness, signal-to-noise ratio, and contrast-to-noise ratio were all superior for the balanced turbo field-echo approach (p < 0.01 for signal-to-noise ratio and contrast-to-noise ratio). Of the 103 segments, 18% of turbo field-echo segments and 9% of balanced turbo field-echo segments had to be excluded from disease evaluation because of insufficient image quality. Sensitivity, specificity, and accuracy for the detection of significant coronary artery stenoses in the evaluated segments were 92%, 67%, 85%, respectively, for turbo field-echo and 82%, 82%, 81%, respectively, for balanced turbo field-echo. CONCLUSION: Balanced turbo field-echo offers improved image quality with significantly fewer nondiagnostic segments when compared with turbo field-echo. For the detection of CAD, both sequences showed comparable accuracy for the visualized segments.

Three-Dimensional (3D) Microarchitecture Correlations with 2D Projection Image Gray-Level Variations Assessed by Trabecular Bone Score Using High-Resolution Computed Tomographic Acquisitions: Effects of Resolution and Noise.

The aim of the present study is to determine the level of correlation between the 3-dimensional (3D) characteristics of trabecular bone microarchitecture, as evaluated using microcomputed tomography (μCT) reconstruction, and trabecular bone score (TBS), as evaluated using 2D projection images directly derived from 3D μCT reconstruction (TBSμCT). Moreover, we have evaluated the effects of image degradation (resolution and noise) and X-ray energy of projection on these correlations. Thirty human cadaveric vertebrae were acquired on a microscanner at an isotropic resolution of 93μm. The 3D microarchitecture parameters were obtained using MicroView (GE Healthcare, Wauwatosa, MI). The 2D projections of these 3D models were generated using the Beer-Lambert law at different X-ray energies. Degradation of image resolution was simulated (from 93 to 1488μm). Relationships between 3D microarchitecture parameters and TBSμCT at different resolutions were evaluated using linear regression analysis. Significant correlations were observed between TBSμCT and 3D microarchitecture parameters, regardless of the resolution. Correlations were detected that were strongly to intermediately positive for connectivity density (0.711≤r(2)≤0.752) and trabecular number (0.584≤r(2)≤0.648) and negative for trabecular space (-0.407 ≤r(2)≤-0.491), up to a pixel size of 1023μm. In addition, TBSμCT values were strongly correlated between each other (0.77≤r(2)≤0.96). Study results show that the correlations between TBSμCT at 93μm and 3D microarchitecture parameters are weakly impacted by the degradation of image resolution and the presence of noise.

Motion artifact reduction and vessel enhancement for free-breathing navigator-gated coronary MRA using 3D k-space reordering.

Breathing-induced bulk motion of the myocardium during data acquisition may cause severe image artifacts in coronary magnetic resonance angiography (MRA). Current motion compensation strategies include breath-holding or free-breathing MR navigator gating and tracking techniques. Navigator-based techniques have been further refined by the applications of sophisticated 2D k-space reordering techniques. A further improvement in image quality and a reduction of relative scanning duration may be expected from a 3D k-space reordering scheme. Therefore, a 3D k-space reordered acquisition scheme including a 3D navigator gated and corrected segmented k-space gradient echo imaging sequence for coronary MRA was implemented. This new zonal motion-adapted acquisition and reordering technique (ZMART) was developed on the basis of a numerical simulation of the Bloch equations. The technique was implemented on a commercial 1.5T MR system, and first phantom and in vivo experiments were performed. Consistent with the results of the theoretical findings, the results obtained in the phantom studies demonstrate a significant reduction of motion artifacts when compared to conventional (non-k-space reordered) gating techniques. Preliminary in vivo findings also compare favorably with the phantom experiments and theoretical considerations. Magn Reson Med 45:645-652, 2001.

Nonenhanced arterial spin labeled carotid MR angiography using three-dimensional radial balanced steady-state free precession imaging.

PURPOSE: To optimize and preliminarily evaluate a three-dimensional (3D) radial balanced steady-state free precession (bSSFP) arterial spin labeled (ASL) sequence for nonenhanced MR angiography (MRA) of the extracranial carotid arteries. MATERIALS AND METHODS: The carotid arteries of 13 healthy subjects and 2 patients were imaged on a 1.5 Tesla MRI system using an undersampled 3D radial bSSFP sequence providing a scan time of ∼4 min and 1 mm(3) isotropic resolution. A hybridized scheme that combined pseudocontinuous and pulsed ASL was used to maximize arterial coverage. The impact of a post label delay period, the sequence repetition time, and radiofrequency (RF) energy configuration of pseudocontinuous labeling on the display of the carotid arteries was assessed with contrast-to-noise ratio (CNR) measurements. Faster, higher undersampled 2 and 1 min scans were tested. RESULTS: Using hybridized ASL MRA and a 3D radial bSSFP trajectory, arterial CNR was maximized with a post label delay of 0.2 s, repetition times ≥ 2.5 s (P < 0.05), and by eliminating RF energy during the pseudocontinuous control phase (P < 0.001). With higher levels of undersampling, the carotid arteries were displayed in ≤ 2 min. CONCLUSION: Nonenhanced MRA using hybridized ASL with a 3D radial bSSFP trajectory can display long lengths of the carotid arteries with 1 mm(3) isotropic resolution. J. Magn. Reson. Imaging 2015;41:1150-1156. © 2014 Wiley Periodicals, Inc.

Increased risk of cardiovascular disease (CVD) with age in HIV-positive men : a comparison of the D:A:D CVD risk equation and general population CVD risk equations

OBJECTIVES: The aim of the study was to statistically model the relative increased risk of cardiovascular disease (CVD) per year older in Data collection on Adverse events of anti-HIV Drugs (D:A:D) and to compare this with the relative increased risk of CVD per year older in general population risk equations. METHODS: We analysed three endpoints: myocardial infarction (MI), coronary heart disease (CHD: MI or invasive coronary procedure) and CVD (CHD or stroke). We fitted a number of parametric age effects, adjusting for known risk factors and antiretroviral therapy (ART) use. The best-fitting age effect was determined using the Akaike information criterion. We compared the ageing effect from D:A:D with that from the general population risk equations: the Framingham Heart Study, CUORE and ASSIGN risk scores. RESULTS: A total of 24 323 men were included in analyses. Crude MI, CHD and CVD event rates per 1000 person-years increased from 2.29, 3.11 and 3.65 in those aged 40-45 years to 6.53, 11.91 and 15.89 in those aged 60-65 years, respectively. The best-fitting models included inverse age for MI and age + age(2) for CHD and CVD. In D:A:D there was a slowly accelerating increased risk of CHD and CVD per year older, which appeared to be only modest yet was consistently raised compared with the risk in the general population. The relative risk of MI with age was not different between D:A:D and the general population. CONCLUSIONS: We found only limited evidence of accelerating increased risk of CVD with age in D:A:D compared with the general population. The absolute risk of CVD associated with HIV infection remains uncertain.