A medical apparatus, comprising: a probe, adapted for insertion into a heart, the heart having a pericardium thereabout; a memory having programs stored therein; a display; and a processor linked to the display and coupled to access the memory to execute the programs, the processor being connectable to a MRI apparatus, the programs comprising a MRI control module and an image analysis module, wherein the programs cause the processor to perform the steps of: iteratively acquiring magnetic resonance imaging data that includes the pericardium, by invoking the MRI control module to communicate control signals to the MRI apparatus, the MRI data including a first set of MRI data and a second set of MRI data; measuring the pericardium by analyzing the sets of MRI data using the image analysis module; making a determination that a measurement of the pericardium in the second set of MRI data differs from the measurement of the pericardium in the first set of MRI data; and responsively to the determination reporting a change in configuration of the pericardium, wherein the steps of iteratively acquiring, measuring, making a determination, and reporting are performed while performing a medical procedure on a living subject. a probe, adapted for insertion into a heart, the heart having a pericardium thereabout; a memory having programs stored therein; a display; and a processor linked to the display and coupled to access the memory to execute the programs, the processor being connectable to a MRI apparatus, the programs comprising a MRI control module and an image analysis module, wherein the programs cause the processor to perform the steps of: iteratively acquiring magnetic resonance imaging data that includes the pericardium, by invoking the MRI control module to communicate control signals to the MRI apparatus, the MRI data including a first set of MRI data and a second set of MRI data; measuring the pericardium by analyzing the sets of MRI data using the image analysis module; making a determination that a measurement of the pericardium in the second set of MRI data differs from the measurement of the pericardium in the first set of MRI data; and responsively to the determination reporting a change in configuration of the pericardium, wherein the steps of iteratively acquiring, measuring, making a determination, and reporting are performed while performing a medical procedure on a living subject. iteratively acquiring magnetic resonance imaging data that includes the pericardium, by invoking the MRI control module to communicate control signals to the MRI apparatus, the MRI data including a first set of MRI data and a second set of MRI data; measuring the pericardium by analyzing the sets of MRI data using the image analysis module; making a determination that a measurement of the pericardium in the second set of MRI data differs from the measurement of the pericardium in the first set of MRI data; and responsively to the determination reporting a change in configuration of the pericardium, wherein the steps of iteratively acquiring, measuring, making a determination, and reporting are performed while performing a medical procedure on a living subject.