4D retrospective black blood trueFISP imaging of mouse heart

Abstract

The purpose of this study was to demonstrate the feasibility of steady-state True fast imaging with steady precession (True-FISP) four-dimensional imaging of mouse heart at high resolution and its efficiency for cardiac volumetry. Three-dimensional cine-imaging of control and hypoxic mice was carried out at 4.7 T without magnetization preparation or ECG-triggering. The k-space lines were acquired with the TrueFISP sequence (pulse repetition time/echo time ‫؍‬ 4/2 ms) in a repeated sequential manner. Retrospective reordering of raw data allowed the reconstruction of 10 three-dimensional images per cardiac cycle. The acquisition scheme used an alternating radiofrequency phase and sum-of-square reconstruction method. Black-blood three-dimensional images at around 200 m resolution were produced without banding artifact throughout the cardiac cycle. High contrast to noise made it possible to estimate cavity volumes during diastole and systole. Right and left ventricular stroke volume was significantly higher in hypoxic mice vs controls (20.2 ؎ 2 vs 15.1 ؎ 2; P < 0.05, 24.9 ؎ 2 vs 20.4 ؎ 2; P < 0.05, respectively). Owing to the many possibilities offered by transgenic and surgical approaches, numerous models of cardiovascular diseases have been developed in mouse. This provides not only a better understanding of physiology but is also of great use in preclinical trials, e.g., gene therapy or pharmacological treatment.MRI has become a reference noninvasive tool to characterize variations in structure and function of mouse heart. Until now, most of the MR studies on mouse models were performed with two-dimensional white-blood cine-imaging combined with cardiac triggering for MR acquisition synchronization (1-4). Parameters like end-systolic and end-diastolic volumes can be measured in order to evaluate both stroke volume and ejection fraction. Nevertheless, routine MRI techniques suffer from many drawbacks. First of all, two-dimensional imaging results in a limited spatial resolution in the slice dimension. In fact, typical out-ofplane resolutions are in the range of 1 mm, whereas mouse heart does not exceed 10 mm in the long axis. This could result in measurement errors due to a partial volume effect.To overcome this issue, some authors have shown interest in performing four-dimensional (4D) (three-dimensional [3D]-cine) imaging (5-7). Feintuch et al. (6) demonstrated the feasibility of 4D mouse imaging with an isotropic spatial resolution of 200 m. Nevertheless, scan times were very long (between 80 and 120 min) for bright blood imaging. More recently, Bucholz et al. (7) presented impressive images with exceptional resolution (80 m), but injection of a nonconventional liposomal gadolinium contrast agent was required. The other drawback of such experiments is that, in many cases, images are acquired with a bright blood contrast. It is now widely accepted that MR sequences with suppression of the blood signal (black or dark blood sequence) are more appropriate to reduce interobserver variability in the drawing of epicar...

Improved Energy Supply Regulation in Chronic Hypoxic Mouse Counteracts Hypoxia-Induced Altered Cardiac Energetics

“…This modification is mainly the consequence of the global heart remodeling in response to chronic hypoxia (i.e. increase in right ventricle mass associated with a decrease in left ventricle mass, table 1), also evidenced and described in vivo by us and others with magnetic resonance imaging [1], [3] or doppler echocardiography [25].…”

“…Pulmonary hypertension induces a right ventricular hypertrophy that may distort the left ventricle [1]–[3] and impair its function [1], [2]. Along with global heart remodeling, complex structural, hormonal and biochemical modifications occur, concerning both energy-producing and energy-consuming processes in heart cells (see [4], [5]).…”

Magnetic resonance imaging tracking of human adipose derived stromal cells within three-dimensional scaffolds for bone tissue engineering

“…The animals were positioned prone within the magnet with the liver at the centre of the NMR coil. A 3D T2*-weighted TrueFISP (Oppelt, 1986) imaging with alternating RF phase pulse method (4) and sum of square reconstruction were used as already described (Vasanawala et al, 2000;Miraux et al, 2009) …”

An Optical Fiber-Based Gating Device for Prospective Mouse Cardiac MRI

“…However, some sequences such as magnetization-prepared sequences or gated hyperpolarized cardiac imaging [26] cannot be retro-gated. Moreover, this method requires magnetic gradient coils with elevated duty cycle as well as an efficient cooling circuit to prevent temperature increase due to short TR and long scan time without any pause [27]. As a matter of fact, the limited heat surface exchange in small diameter gradient coils can switch the gradient amplifiers in security mode to prevent gradient coil damage.…”