Isotropic cine cardiac magnetic resonance imaging an extension to contrast-free angiography: 100% efficient reconstruction through compressive sensing and joint estimation of cardio-respiratory motion
We pursue to develop new cardiac MRI acquisition and reconstruction techniques that let the practitioner obtain, in a single study, an isotropic 3D+t dataset that is robust to cardiac and respiratory motion and from which a cine as well as a contrast-free MRA can be achieved. Expected benefits are:
- A noticeable shortening of the study duration since cine and MRA will be posible out of a unique 3D+t acquisition and since efficiency will be increased since no synchronization will be needed. As an example let us indicate: in our 2015 ISMRM paper (véase sección 4.5 para los detalles concretos del artículo) we have achieved 2D multislce cine in a unique apnea with 12 slices perpendicular to the long axis and with a temporal resolution of 46.4 msec, i.e., we have achieved a speed-up by a factor of 12 current clinical standards. Our idea is to extend these developments to the 3D+t case in a free-breathing scenario.
- We intend to elliminate the slice planification step, so we will contribute to shorten the exam duration as well as to avoid the risk of exam repetition should the planification be carried out incorrectly.
- Minimization of the additional hardware required to acquire both the respiratory and the cardiac signal, so the exam will be simplied and may be applicable to situations in which synchronism cannot be assured —atrial fibrilation of low quality ECG in high fields—.
- To avoid contrast agents in MRA, with a cost reduction and risk minimization so that the breadth of MRA potential patients is increased.
- As a consequence of the previous benefits, the cost and duration of the study will be reduced, so the public health system will increase its efficiency.
From another perspective, diffusion imaging outside the brain (diffusion in body) is a relatively recent technique. Diffusion in body has to cope with motion of abdominal and thoracic structures. On one hand, it requires several acquisitions with a varying parameter in each of them so that the parameters of the diffusion model can be estimated. To the best of oiur knowledge, joint reconstruction of cardiac-respiratory motion with different values of this parameter has not been explored; reconstructions have been done for each parameter in isolation. It is our understanding that a synergistic effect between the cardiac and the body diffusion may be obtained at it will allow us to face the second problem within an integrated model that will bring about improved performance in the final precedure.
As of today, multiple efforts are under course to overme the limitations so far exposed. However, groupwise registration techniques used as a procedure for motion estimation and compensation are scarcely used, despite the benefits we have observed they provide.