Medical fluid system including radio frequency (RF) device within a magnetic assembly, and fluid cartridge body with one of multiple passageways disposed within the RF device, and specially configured cartridge gap accepting a portion of said RF device

A medical fluid system comprising:

• a medical fluid pumping machine;
• a magnet assembly defining a cavity in which a radio frequency device is positioned, the magnet assembly being configured to generate a magnetic field within the cavity;
• and
• a medical fluid cartridge comprising:
• a body having:
• a first portion defining a first fluid passageway and
• a second portion defining a second fluid passageway in fluid communication with the first fluid passageway, the first and second portions defining a gap therebetween, and the gap being sized and shaped to accept a portion of the radio frequency device to allow the first portion of the body to be disposed within the radio frequency device while the second portion of the body is disposed within the cavity defined by the magnet assembly and outside the radio frequency device.