Four-Dimensional Computerized Tomography (4D-CT) Reconstruction without an External Breath Surrogate

Objective: To investigate the feasibility of a four-dimensional computerized tomography (4D-CT) reconstruction method based on the similarity principle of spatial adjacent images and mutual information measure. Methods: The CT data of patient underwent free breathing were acquired in Cine mode by a GE Light Speed 16 CT scanner, the Cine during time was equal to the breathing period of the patient plus one second (about 4-6s) and 8 to 15 slices CT image were acquired by a row CT detector in every Cine scan. A software program was developed by using VC++ and VTK software tools to re-sort the CT data and reconstruct the 4D-CT. Then all of the CT data with same phase were sorted by the program into a same series based on the similarity principle of spatial adjacent images and mutual information measure among them, and 3D reconstruction of different phase CT data were completed by using the software. Results: All of the CT data were sort accurately into different series based on the similarity principle of spatial adjacent images and mutual information measures among them. Compared with the unsorted CT data, the motion artifacts in the 3D reconstruction of sorted CT data were reduced significantly, and all of the sorted CT series result in a 4D-CT that reflected the characteristic of the free breathing. Conclusion: Time-resolved 4D-CT reconstruction can be implemented with any general multi-slice CT scanners based on the similarity principle of spatial adjacent images and mutual information measure, the process of the 4D--CT data acquisition and reconstruction were not restricted to the hardware or software of the CT scanner and has the feasibility and extensive applicability.