Method and apparatus of cone beam CT dynamic imaging
A cone-beam scanning system scans along a half circle. The reconstruction uses a weighting function which decreases for rows farther from the scan plane to take the redundancy of the projection data into account. Another embodiment uses a circle plus sparse helical scan geometry. Image data can be taken in real time.
1. A method for forming a cone beam reconstruction image of an object, the method comprising:
(a) performing a cone-beam scan of the object by using a cone-beam emitter and a detector to perform a circle plus sparse spiral scanning geometry or partial circle plus sparse spiral scanning geometry so as to obtain projection data, wherein the sparse spiral scanning consists of acquiring eight projections at points during helical scanning which covers an angular range of 4π; and
(b) forming the cone beam reconstruction image from the projection data.
2. The method of claim 1 , wherein the object comprises a breast.
3. The method of claim 2 , wherein the circle or partial circle scanning geometry is around the breast and the spiral scanning geometry is along the breast.
4. The method of claim 3 , wherein step (b) comprises adding terms from the circle and the spiral scanning geometry, or partial circle scanning geometry and the spiral scanning geometry.
5. The method of claim 4 , wherein step (b) further comprises adding a correction term representing information in Radon space which cannot be acquired through a circular scan.
6. A system for forming a cone beam reconstruction image of an object, the system comprising:
a cone-beam emitter;
a detector;
a gantry supporting the cone-beam emitter and the detector such that x-rays emitted by the cone-beam emitter are detected by the detector after passing through the object;
a processor configured to:
(a) perform a cone-beam scan of the object by causing the gantry to perform relative movement of the cone-beam emitter and the detector to perform a circle plus sparse spiral scanning geometry or partial circle plus sparse spiral scanning geometry so as to obtain projection data, wherein the sparse spiral scanning consists of acquiring eight projections at points during helical scanning which covers an angular range of 4π; and
(b) form the cone beam reconstruction image from the projection data.
7. The system of claim 6 , wherein the processor adds terms from the circle and the spiral scanning geometry, or from the partial circle scanning geometry and the spiral scanning geometry.
8. The system of claim 7 , wherein the processor further adds a correction term representing information in Radon space which cannot be acquired through a circular scan or partial circle scanning geometry.
9. The system of claim 6 , wherein the gantry rotates around an axis of rotation for the circle or partial circle scanning geometry, and wherein the gantry frame both rotates around the axis of rotation and moves along the axis of rotation for the spiral scanning geometry.