Imaging by nuclear magnetic resonance and its bio-medical implications.

The distribution of proton spin concentration (water concentration) and the proton spin-lattice relaxation time (T1) can be imaged in a sample by placing it in a magnetic field gradient, applying appropriate radio-frequency (rf) pulses, and measuring the rf radiated from the sample. The Aberdeen machine is designed to image the human body in vivo at 400 gauss and 1.7 MHz. The spatial resolution predicted is about 1 cm for a 20% difference of T1. Measurements of T1 for small samples of tissue in vitro show a five-fold range of values for some soft tissues. Breast tumours and liver metastases have shown T1 values very different from the surrounding tissue. The method has the potential of perhaps imaging any pathology which changes water concentration, forms fluid pools or affects the binding of water to macromolecules. The potential hazards, which need more investigation, seem slight.