Chemical, usually acetic acid in the fixer and sodium carbonate in the developer, to neutralize the developer and to swell the gelatin, respectively.

The term 'active' refers to any medical device that can only serve its intended use with the supply of power by any means including, but not limited to line, battery, or gas power. Examples of active devices include ventilators, pacemakers, and patient monitoring devices.

Magnetic shielding through the use of secondary shielding coils designed to produce a magnetic field that cancels the field from primary coils in regions where it is not desired. These coils may be inside the magnet cryostat. Active shielding can be applied to the main magnet or to the gradient magnetic fields.

See also Magnetic Shielding, Self Shielding and Room Shielding.

Shimming by suitably adjusting the currents in shim coils for qualitiy assurance.

See Active Shielding.