Sudden cardiac death is often caused by ventricular arrhythmias. These arrhythmias are believed to originate from the
border zones where tissue was damaged by an ischemic event involving the coronary arteries. The specific mechanisms
relating the geometry of these territories to the electrical behavior remains poorly understood. A major problem is the
lack of detailed information describing the morphology of the affected perfusion bed. We present the first perfusion MR
images of excised whole heart preparations where the irregular boundaries of perfusion territories are described. The
filling pattern and final volume of the RCA perfusion territory are clearly visualized.
KEYWORDS: Breast, Finite element methods, Magnetic resonance imaging, Mammography, Image segmentation, Receivers, Image registration, Breast cancer, Chemical elements, Skin
The objectives of this investigation are to improve quality of subtraction MR breast images and improve accuracy of time-signal intensity curves (TSIC) related to local contrast-agent concentration in dynamic MR mammography. The patients, with up to nine fiducial skin markers (FSMs) taped to each breast, were prone with both breasts suspended into a single well that housed the receiver coil. After a preliminary scan, paramagnetic contrast agent gadopentate digmeglumine (Gd) was delivered intravenously, followed by physiological saline. The field of view was centered over the breasts. We used a gradient recalled echo (GRE) technique for pre-Gd baseline, and five more measurements at 60s intervals. Centroids were determined for corresponding FSMs visible on pre-Gd and any post-Gd images. This was followed by segmentation of breast surfaces in all dynamic-series images, and meshing of all post-Gd breast images. Tetrahedral volume and triangular surface elements were used to construct a finite element method (FEM) model. We used ANSYSTM software and an analogy between orthogonal components of the displacement field and the temperature differences in steady-state heat transfer (SSHT) in solids. The floating images were warped to a fixed image using an appropriate shape function for interpolation from mesh nodes to voxels. To reduce any residual misregistration, we performed surface matching between the previously warped floating image and the target image. Our method of motion correction via nonrigid coregistration yielded excellent differential-image series that clearly revealed lesions not visible in unregistered differential-image series. Further, it produced clinically useful maximum intensity projection (MIP) 3D images.
KEYWORDS: Single photon emission computed tomography, Magnetic resonance imaging, Echocardiography, Blood, Electrocardiography, Nuclear medicine, Magnetism, Transducers, Data acquisition, Medical imaging
Fifteen patients underwent resting echocardiography (EC), ECG gated cardiac MR ventriculography (MRV) and blood pool planar and SPECT ventriculography (SPV) sequentially on the same day. In addition, 36 patients had sequential ECG gated blood pool and SPV and 20 normal volunteers, age > 18 years, had sequential ECG gated cardiac MRI performed on both Siemens closed, 1.5T, and open, 0.2T, magnets. Echocardiography was performed using a HP 5500 system equipped with an S4 transducer in 2D mode. MRV at 0.2T and 1.5T used a circular polarized body coil. Nuclear Medicine studies used 25 mCi Tc- 99m labeled red blood cells. Gated planar and SPV were acquired on a dual head Siemens E-Cam system. We have found that MRV affords the most accurate measurement of ventricular function. SPV and MRV provide similar estimations of left ventricular function (LVEF). Further, SPV consistently provides higher LVEF, as compared to the planar data simultaneously acquired. Observed significant differences in intermodality measurements indicate that follow up studies in patients, especially in patients whose management is critically dependent on functional measurement changes, should be monitored by one modality only.
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