System and method for image based physiological monitoring of cardiovascular function

#This invention is directed to real-time monitoring of heart function using magnetic resonance imaging (MRI), interleaved with imaging used to guide or perform stress testing or interventional cardiovascular procedures.

#Monitoring the electrocardiogram (ECG) for ischemic changes during dobutamine stress testing or an MR-guided intervention is not possible in the MR environment due to the magnetohydrodynamic effect. This effect occurs because ions in the blood flowing through the body in the presence of a static magnetic field create its own electrical voltage. This additional voltage is added to the ECG when the patient is inside the static magnetic field, causing distortion. However, during MR guided cardiovascular interventional procedures or during stress testing, cardiac function should be monitored for possible ischemic changes or dyssynchrony. Wall motion and global cardiac function can be assessed in real time by MR and interleaved with other types of MR acquisitions during the procedure. One approach to monitoring for ischemic changes therefore would be to qualitatively assess wall motion in the images as they are acquired. However, in the time gaps where the physician cannot view the functional images (during ramp-up of dobutamine dose, or while placing a catheter for example), it would be useful to have a measure of cardiac function automatically determined and provided as continuous feedback.

#The main challenge in patient monitoring for ischemia in MRI is that the static magnetic field, RF pulses, and field gradient switching all distort the ECG making it non-diagnostic for ischemia detection. Ischemia in the heart first results in a perfusion deficit, then in abnormalities in wall motion, then ECG changes, then finally in chest pain. Currently, external monitoring systems with ECG, blood pressure, pulse oximetry and sometimes invasive blood pressure are used in conjunction with MR for global patient monitoring. ECG can be used to monitor only the heart rate. During interventional procedures, changing the real time scan plane is used to check for changes in function, but this does not provide continuous monitoring. Visual review of perfusion scans during acquisition also can be used to check for changes in heart perfusion, but these cannot be repeated as often during an exam as ventricular function imaging since they require contrast agent administration.

#FIG. 1 illustrates one exemplary real-time heart function imaging/monitoring configuration, according to an embodiment of the invention.

#FIG. 2 illustrates an exemplary image-based monitoring configuration for 2D radio-frequency (RF) excitation for real-time flow measurement, according to an embodiment of the invention.

#FIGS. 3(A)-(C) depicts an exemplary short axis slice with m-mode projections shown, and the derived contours superimposed on m-mode display, according to an embodiment of the invention.

#Exemplary embodiments of the invention as described herein generally include systems and methods for real-time monitoring of heart function using magnetic resonance imaging (MRI), interleaved with imaging used to guide or perform stress testing or interventional cardiovascular procedures. Accordingly, while the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

#As used herein, the term “image” refers to multi-dimensional data composed of discrete image elements (e.g., pixels for 2-D images and voxels for 3-D images). The image may be, for example, a medical image of a subject collected by computed tomography, magnetic resonance imaging, ultrasound, or any other medical imaging system known to one of skill in the art. The image may also be provided from non-medical contexts, such as, for example, remote sensing systems, electron microscopy, etc. Although an image can be thought of as a function from R3 to R, the methods of the inventions are not limited to such images, and can be applied to images of any dimension, e.g. a 2-D picture or a 3-D volume. For a 2- or 3-dimensional image, the domain of the image is typically a 2- or 3-dimensional rectangular array, wherein each pixel or voxel can be addressed with reference to a set of 2 or 3 mutually orthogonal axes. The terms “digital” and “digitized” as used herein will refer to images or volumes, as appropriate, in a digital or digitized format acquired via a digital acquisition system or via conversion from an analog image.

#A system according to an embodiment of the invention includes imaging data acquired in an interleaved manner, with part of the data used to monitor heart function, and the rest used for diagnostic purposes, such as guiding a procedure, methods for extracting relevant features from the images related to heart function, such as endocardial and epicardial borders, volume flow through the aorta, change in shape of the ventricle, myocardial perfusion, etc., and methods for detecting clinically relevant changes in the aforementioned features and alerting an operator.