Hardware for Performing Hyperpolarized Helium Imaging on a Clinical MR Imager

For the past forty years, magnetic resonance imaging (MRI) has been one of the most common methods for obtaining volume images of human organs. However, some organs in the human body, such as the lungs, are resistant to these techniques, due to their lack of protons. In 1994, hyperpolarized noble gas MRI was introduced, and today is viewed as the best solution to the MR imaging dilemma. The different resonance frequencies of proton and helium, however, present an obstacle for hyperpolarized helium imaging. Conventional MR scanners are proton-based and, thus, are incapable of transmitting and receiving at frequencies other than that of proton. Broadband MR scanners, which are capable of transmitting and receiving at a variety of frequencies, are expensive and are not readily available for all nuclei. A heterodyne system is an inexpensive system that can be added to conventional MR systems to enable them to image a variety of nuclei. This system transforms the output of the MR system, at the frequency of proton, to the frequency of the nuclei of interest. The resulting signal obtained from the subject is transformed back to the frequency of proton by the heterodyne system, thereby enabling the MR system to create an image of the subject. With this system, hyperpolarized helium images of human lungs were obtained using a variety of different protocols. This heterodyne system opens up the possibility of new types of imaging, based on nuclei other than proton, on conventional MR scanners. Acknowledgements I would like to thank my thesis supervisor at Brigham and Women's Hospital, Dr. Mitch Albert, who was always there to advise me and provide support. Special thanks to Professor Bob Lenkinski for providing the basic design for the heterodyne system, and for helping in the inital setup and testing of the system. Thanks to my lab-mates, Arvind Venkatesh and Adelaide Zhang, who taught me so much and helped during the initial setup and testing of the heterodyne system. Many thanks to Ken Hickson, the GE Field Engineer, for helping me debug the gating problem and for his continued help with the intricacies of making our equipment talk to the Signa equipment. Many thanks to Ralph Hashoian who taught me so much about RF coils and mixers, and who always had wonderful suggestions for solving the problems with our coils, our T/R switch and pre-amplifier, and the Signa. I would like to thank my MIT …