Tomography of hydrogen with NMR, and the potential for imaging other body constituents

Nuclear Magnetic Resonance (NMR) presents an exciting potential for medical diagnosis. The short exposure times to both magnetic fields and radio-frequency waves indicates its non-hazardous nature. Since NMR information is most likely to overlap the data provided by x-ray computerized tomography, and in size and cost the equipment is likely to be similar, it is worthwhile to avoid as much as possible the pitfalls of CT in designing NMR imagers. Of these the most obvious is the desire to avoid reconstruction techniques where the data at any one region in the image is dependent on (and affects) the data in all other regions of the image, since in this case artifacts can arise that result in images with false or uninterpretable information. Also, in the interest of time, it is desirable to accumulate simultaneous data from as many elements in the image as possible. These requirements are not necessarily compatible, and system design requires prioritizing them. We present the imaging properties of a NMR imager that utilizes a Varian Magnet with 30 cm diameter pole tips and a 10 cm gap, operated at 3.52 KGauss (15 MHz hydrogen resonant frequency). Line readout techniques are used to avoid the need for reconstructions. An analysis is also presented of the potential for imaging other atomic components of the human body. When comparing to hydrogen it is assumed that the magnetic field strength can be increased so that the imaging can be performed at the highest possible frequency consistent with obtaining acceptable RF penetration. The clinical utility of images of these other elements will be strongly dependent on the performance of the system for hydrogen