This project has worked in two general areas over the last year, Hall effect imaging and technical improvements in cardiovascular MRI. Hall effect imaging is a new non-invasive method of investigating the electrical properties of biological samples. While it holds promises in very good soft tissue and pathology based contrast, it is also demanding on sensor design. Adaptation of conventional single-element ultrasonic sensors for Hall effect imaging was a major focus of our effort to optimize this imaging modality. A method has been found to adapt existing ultrasonic transducers to Hall effect imaging, by combining strict electromagnetic shielding and ultrasonic wave manipulation. This method will allow the further adaptation of medical array ultrasound sensors and fast imaging technology to Hall effect imaging. A very broadband fiber-optic ultrasonic sensor has been designed and constructed in collaboration with the Naval Research Laboratory. This single-element sensor possesses a bandwidth three or more times that of broadband conventional sensors, and is geometrically similar to regular medical transducers. Originally designed for Hall effect imaging, this sensor is generally superior to current single-element medical transducers because of its very broad bandwidth and immunity to electromagnetic interference. Currently work is in progress to reduce the cost of the overall device and improve its robustness. In cardiac magnetic resonance imaging it is of great significance to track the motion of the myocardium. A stimulated-echo based phase tagging method has been developed for this purpose, first results on dog models are promising. The advantage of this method over intensity based tagging method is its much higher spatial resolution. This high spatial resolution may reveal transmural variation in the myocardium, and provide a tool for the study of muscle fiber layout and mechanics of contraction in detail, in vivo. In cardiac and abdominal MRI a frequent problem is that the field of view is often unnecessarily large to prevent signals of the outer areas of the body from aliasing into the region of interest, such as the heart. This practice reduces image resolution and lengthens scan time. A """"""""signal spoiler"""""""" has been developed to erase the signal from the back of the body and solve the field-of-view problem. The spoiler operates on the scrambling effect of a local strong gradient, and the depth of spoiling is controlled. It has been demonstrated that in long-axis cardiac scans the spoiler reduces the field of view, and therefore the scan time, by 40% or more. It is now installed on the cardiac scanner of LCE, and further integration into the GE Signa platform is in progress.
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