Insights from the IronTract challenge: Optimal methods for mapping brain pathways from multi-shell diffusion MRI.

Limitations in the accuracy of brain pathways reconstructed by diffusion MRI (dMRI) tractography have received considerable attention. While the technical advances spearheaded by the Human Connectome Project (HCP) led to significant improvements in dMRI data quality, it remains unclear how these data should be analyzed to maximize tractography accuracy. Over a period of two years, we have engaged the dMRI community in the IronTract Challenge, which aims to answer this question by leveraging a unique dataset.

Anatomical bases of fast parietal grasp control in humans: A diffusion-MRI tractography study.

The dorso-posterior parietal cortex (DPPC) is a major node of the grasp/manipulation control network. It is assumed to act as an optimal forward estimator that continuously integrates efferent outflows and afferent inflows to modulate the ongoing motor command. In agreement with this view, a recent per-operative study, in humans, identified functional sites within DPPC that: (i) instantly disrupt hand movements when electrically stimulated; (ii) receive short-latency somatosensory afferences from intrinsic hand muscles.

Higher in vivo Cortical Intracellular Volume Fraction Associated with Lithium Therapy in Bipolar Disorder: A Multicenter NODDI Study.

Background: MRI studies in patients with bipolar disorder have suggested that lithium is associated with grey matter increases that may underlie its therapeutic effects. However, the relationship between grey matter volume and cellular microstructural changes is not straightforward, as modifications of different cellular compartments of grey matter may be involved.

Objectives: Our aim was to test the hypothesis that dendritic density is higher in patients undergoing lithium therapy than in patients without lithium, using advanced modelling of water diffusion investigated with MRI.

Particle deposition and resistance in the noses of adults and children.

Nasal filter efficiency for particles has been described by several authors as showing large individual variations, probably somehow related to airflow resistance. Twelve children, aged 5.5-11.

Assessment of the optimal atrio-ventricular delay in DDD paced patients by impedance plethysmography.

The beneficial haemodynamic effects of sequential atrioventricular (AV) pacing have been clearly established and are dependent on the AV delay and pacing rate. However, the optimal AV delay is difficult to determine in each particular patient. We used a modified impedance plethysmographic method to assess variations in stroke volume for different AV delay and pacing rate settings.

A dynamic analysis of the ventilatory response to hypoxia in man.

1. The dynamics of the ventilatory response to isocapnic hypoxia were studied in seven healthy subjects using four different levels of hypoxia, (inspired oxygen pressures, PI,O2 equal to 110, 100, 80 and 60 mmHg) successively increasing and decreasing stepwise. 2.

Particle size study of nine metered dose inhalers, and their deposition probabilities in the airways.

This study deals with the particle size measurement of nine aerosol metered dose inhalers. Calibration was made possible by the use of a laser particle velocimeter (aerodynamic Particle Sizer from TSI). The count median aerodynamic diameters (CMAD) show little variation, from 0.

A dynamic analysis of the ventilatory response to carbon dioxide inhalation in man.

1. The dynamics of the ventilatory response to carbon dioxide inhalation were studied in ten healthy young men using four different inspired fractions of carbon dioxide (FI, CO2) in air (0.015, 0.

Inhaled particle deposition and clearance from the normal respiratory tract.

Tracheo-bronchial and pulmonary deposited fractions of inhaled insoluble particles and their clearances rates were studied in 16 healthy non-smokers. After oral inhalation of radioactive particles (Mean Mass Aerodynamic Diameter (MMAD) = 3 microns, sigma g = 1.4 labelled with 111In) incorporated radioactivity was measured for each subject both by a gamma camera from to until the 3rd day, then from the 3rd until the 5th day first by a gamma camera and then by a low background profile scanner and from the 5th until the 35th day by a low background profile scanner alone.

[Short-term tracheobronchial clearance in apparently pure Gougerot-Sjögren syndrome].

Bronchopulmonary involvement in the Sjögren syndrome can lead to distal obstructive airway disease. This syndrome induces a decrease in secretions which become rare and thick, and consequently a slowing down of mucociliary activity. This activity, which can be estimated by tracheobronchial clearance studies, was investigated in seven non-smoking women (mean age = 56.

Arterial elasticity and physical working capacity in young men.

We have tested the hypothesis that there is a positive relation between arterial elasticity and physical working capacity (PWC) at a given age. The subjects were 28 young men, 16-18 yr old. Arterial elasticity was evaluated by measuring the carotid to femoral pulse-wave velocity (c) at rest.

[Study of segmental ventricular contraction by the analysis of the radius of curvature].

We have developed a procedure for segmental contraction analysis in the left ventricle based on the study of the radius of local curvature. This method has the advantage of non-necessitating the determination of basal reference values. The problem of optimal homogenisation of the raw date was resolved by developing a method based on a mobile average of 5 points by introducing a ponderation by second derivations.

[Detection of cardiac graft rejection using proton nuclear magnetic resonance].

Rejection of cardiac transplants can be detected by NMR imaging if it is associated with a change in myocardial T1 and/or T2 proton relaxation time. T1 and T2 were studied in 14 Lewis rats that underwent heterotopic cardiac transplantation. T1 and T2 were measured in vitro immediately after sacrifice 3, 4, 7 or 11 days after the graft using a Minispec BRUKER PC20.

Assessment of ventilatory performance of athletes using the maximal expiratory flow-volume curve.

We carried out a maximum expiratory flow-volume curve (MEFV) and a spirometric recording with 67 athletes of different ages (15-27 years) and disciplines (rowers, kayakists, cyclists, swimmers) and with 20 adult and 13 adolescent nonathletic controls of matching ages. These recordings were repeated, with athletes only, after 6-10 months of training. Significant differences between the groups of adult athletes and the controls were observed for some parameters, the most discriminating of which were, in order, the peak expiratory flow (PEF), the forced expiratory volume in the first second (FEV1), and the flow at 75% of the vital capacity (V75).

Nuclear magnetic resonance and proton relaxation times in experimental heterotopic heart transplantation.

It should be possible to detect heart transplant rejection by nuclear magnetic resonance (NMR) imaging if it induces myocardial T1 and T2 proton relaxation time alterations or both. We studied 20 Lewis rats after a heterotopic heart transplantation. In vitro measurement of T1 and T2 was performed on a Minispec PC20 (Bruker) 3 to 9 days after transplantation.

[Propagation rate of arterial pressure waves as a function of age and physical training].

The arterial pulse wave velocity is determined to a large extent by the arterial elastic modulus. We tried to assess the importance of this parameter in cardio-vascular adaptation to exercise by measuring pulse wave velocity (c) in 45 sedentary subjects and 28 competitive cyclists whose ages ranged from 14 to 47 years. The measurements were performed at rest and during the recovery phase after ergometric exercise.