Ct extremity scanner

Abstract

A CT scanner according to the present invention is particularly adapted for scanning the extremities of a patient. The CT scanner includes an x-ray source and x-ray detector mounted for rotation and translation along an axis parallel to a table for supporting the patient's extremity. The source and detector are mounted opposite one another on an inner circumference of an inner ring. The inner ring is rotatable about the axis within an outer ring mounted on at least one carriage. The carriage is movable parallel to the axis. During scanning, the inner ring rotates within the outer ring while the rings and carriage move along the axis, thereby producing a helical scan of the extremity.

1 . A CT scanner comprising:
 a rail;   a carriage movable along the rail;   a ring rotatably mounted to the carriage;   an x-ray source mounted to the ring; and   an x-ray detector mounted to the ring opposite the source.   
     
     
         2 . The CT scanner of  claim 1  wherein the ring is an inner ring, the CT scanner further including an outer ring fixedly mounted to the carriage. 
     
     
         3 . The CT scanner of  claim 2  further including a motor between the inner ring and outer ring for rotatably driving the inner ring relative to the outer ring. 
     
     
         4 . The CT scanner of  claim 3  further including a stand supporting the rail. 
     
     
         5 . The CT scanner of  claim 4  further including a motor translating the carriage along the rail. 
     
     
         6 . The CT scanner of  claim 5  wherein the rail threadably engages the carriage and the motor rotatably drives the rail relative to the carriage to cause translation of the carriage relative to the rail. 
     
     
         7 . The CT scanner of  claim 1  wherein the inner diameter of the ring is less than 24″. 
     
     
         8 . The CT scanner of  claim 1  wherein the inner diameter of the ring is between approximately 18″ and approximately 24″. 
     
     
         9 . The CT scanner of  claim 1  further including a motor translating the carriage along the rail. 
     
     
         10 . The CT scanner of  claim 9  wherein the rail threadably engages the carriage and a motor rotatably drives the rail relative to the carriage to cause translation of the carriage relative to the rail. 
     
     
         11 . The CT scanner of  claim 1  wherein the rail is a first rail and the carriage is a first carriage, the CT scanner further including a second rail parallel to the first rail and a second carriage movable along the second rail, the ring rotatably mounted to the first and second carriages. 
     
     
         12 . A CT scanner comprising:
 a patient support surface;   an x-ray source movable about an arc adjacent the patient support surface; and   an x-ray detector adjacent the patient support surface to receive x-rays from the source.   
     
     
         13 . The CT scanner of  claim 12  wherein the detector is a first detector, the CT scanner further including a second detector mounted adjacent the patient support surface, the second detector mounted transversely to the first detector, such that, as the source moves along the arc, x-rays from the source initially are received primarily by the first detector, then substantially equally by the first detector and the second detector and then primarily by the second detector. 
     
     
         14 . The CT scanner of  claim 13  wherein the detector is movable about an arc adjacent the patient support surface 
     
     
         15 . The CT scanner of  claim 14  wherein the detector is movable about an arc complementary to the arc about which the source moves. 
     
     
         16 . A method for taking an x-ray image:
 a) placing an extremity of a patient on a support surface;   b) moving a source and a detector rotatably about an axis generally parallel to the support surface; and   c) translating the source and the detector generally along the axis while the source and the detector are rotating about the extremity of the patient.   
     
     
         17 . The method of  claim 16  wherein only the extremity of the patient is between the source and the detector in said steps b) and c). 
     
     
         18 . The method of  claim 16  wherein the source and detector are mounted to a ring, the method further including the step of rotatably driving the ring during said step b). 
     
     
         19 . A CT scanner comprising:
 a rail;   a carriage movable along the rail;   an x-ray source rotatably mounted to the carriage; and   an x-ray detector mounted opposite the source and rotatable with the source.   
     
     
         20 . The CT scanner of  claim 19  further including an inner ring, the CT scanner further including an outer ring fixedly mounted to the carriage. 
     
     
         21 . The CT scanner of  claim 20  further including a motor between the inner ring and outer ring for rotatably driving the inner ring relative to the outer ring. 
     
     
         22 . The CT scanner of  claim 21  further including a motor translating the carriage along the rail. 
     
     
         23 . The CT scanner of  claim 19  wherein the detector is between approximately 18 inches and approximately 24 inches from the source.