X-ray guided surgical location system with extended mapping volume

A method of tracking an object within a body, comprising:

• attaching a plurality of reference coordinate sensing devices to the body and at least one object coordinate sensing device to the object;
• registering the positions of the plurality of reference coordinate sensing devices in a frame of reference fixed to the body;
• selecting at least one of the plurality of reference coordinate sensing devices in proximity to the object;
• and
• receiving and processing signals from the at least one selected reference coordinate sensing device and the object coordinate sensing device to determine signal-based coordinates of the object and of the selected reference device so as to register the object coordinates relative to the body.

A method of tracking an object within a body comprising:

• placing at least one field transducer, having a detection volume, in a vicinity of the body;
• determining the position of the at least one field transducer;
• displaying a map showing the detection volume of the at least one field transducer relative to the body;
• and
• controlling the tracking of the object responsive to the map.

A system for determining the disposition of an object within a body of a patient, comprising:

• a position sensor, which is coupled to the object;
• a plurality of reference sensors, which are attached to the body;
• a movable field transducer, which transmits fields to or receives fields from the position sensor and reference sensors;
• and
• a processor, which selects at least one of the reference sensors in proximity to the object and determines coordinates of the position sensor relative to the selected reference sensor, irrespective of movement of the field transducer relative to the patient.

A system for determining the disposition of an object within a body of a patient, comprising:

• a position sensor for coupling to the object;
• at least one reference sensor for attaching to the body;
• one or more field transducers having respective detection volumes for transmitting fields to or receiving fields from the position sensor and reference sensor;
• and
• a processor, which determines the disposition of the object and the positions of the field transducers responsive to the transmitted fields and indicates the detection volumes of the field transducers responsive to the positions.

Apparatus for X-ray guided surgery, comprising:

• a reference element, which is placed in contact with the body of a subject, said element comprising a reference coordinate sensing device, in a predetermined, fixed position thereon;
• a fluoroscope, for forming at least one X-ray image of the body, including the reference element;
• and
• a computer, which receives signals from the reference coordinate sensing devices and processes the signals to determine signal-based coordinates thereof, and which analyzes the image to derive an image-based coordinate system and to find a transformation to register the signal-based coordinates and the image-based coordinate system.