Open access superconducting MRI magnet

An open access magnetic resonance imaging apparatus, comprising:

• a substantially open ferromagnetic frame including an upper end plate and a lower end plate mounted horizontally, spaced apart, and generally parallel to one another on at least one support column, to define a patient receiving area therebetween accessible to additional medical equipment and personnel;
• first and second toroidal shaped coils of superconducting wire mounted to said upper and lower end plates, respectively, for generating a magnetic flux field along a vertical polar axis, with a return path for said magnetic flux field provided by said support column and by said upper and lower end plates, said superconducting wire having a low transition temperature;
• magnetic flux shaping means mounted to each said end plate for shaping said flux field to provide generally parallel lines of magnetic flux within said patient receiving area, said flux shaping means including a rose shim mounted to each said end plate;
• a cryocooler;
• and
• a tubular cooling circuit mounted in thermally conductive contact with said cryocooler and said superconducting coils for circulating a cooling fluid around said superconducting coils to cool said superconducting coils by a combination of convective and conductive heat transfer, to maintain said superconducting coils at a temperature below said low transition temperature;
• and
• a counterflow heat exchanger in fluid communication with said cooling circuit for precooling said cooling fluid upstream of said cryocooler, said heat exchanger being contained within one of said vacuum vessels.