Design and assembly of an 8 tesla whole-body MR scanner

Purpose: The purpose of this report is to describe the design and construct ion of an 8 T/80 cm whole-body MRI system operating at 340 MHz. Method: The 8 T/80 cm magnet was constructed from 414 km of niobium titaniu m superconducting wire; The winding of this wire on four aluminum formers r esulted in a total inductance of 4,155 H. Gradient subsystems included eith er a body gradient or a head gradient along with a removable shim insert. T he magnet and gradient subsystems were interfaced to two spectrometers. The se provided the control of the gradient amplifiers and the two sets of four RF power amplifiers. The latter provide in excess of 8 kW of RF power from 10 to 140 MHz and 10 kW of RF power from 245 to 345 MHz. A dedicated compu ter-controlled patient table wits designed and assembled. The entire system is located in a clinical setting, facilitating patient-based studies. Results: The 8 T/80 cm magnet was energized without complication and achiev ed persistent operation using 198.9 A of current, thereby storing 81.5 MJ o f magnetic energy. Exceptional performance was observed for nearly all comp onents both in isolation and when combined within the complete system. Conclusion: An 8 T/80 cm MRT system has been assembled. The magnet subsyste m is extremely stable and is characterized by good homogeneity and acceptab le boil-off rates.