Simulation of four‐dimensional CT images from deformable registration between inhale and exhale breath‐hold CT scans

Abstract

The generation of 4-D CT images by deformable registration of inhale and exhale CT images is feasible. This can lower the dose needed for 4-D CT acquisitions or can help to correct 4-D acquisition artifacts. The 4-D CT model can be used to propagate contours, to compute a 4-D dose map, or to simulate CT acquisitions with an irregular breathing signal. It could serve as a basis for 4-D radiation therapy planning. Further work is needed to make the simulation more realistic by taking into account hysteresis and more complex voxel trajectories.

Functional Imaging: CT and MRI

“…With the broader coverage, retrospective gating methods have emerged for both cardiac as well as pulmonary imaging whereby, via a very low pitch, images are gathered during the respiratory or cardiac cycles while recording the physiologic signal together with the projection images. Prospectively, (11) or retrospectively (10,(12)(13)(14)(15)(16)(17), the portions of the physiologic cycle of interest can be selected from within the slow pitch spiral data such that a volumetric image data set is reconstructed for just that location of the respiratory or cardiac cycle. Multiple portions of the physiologic cycle can thus be reconstructed to yield a dynamic image sequence of the organ of interest.…”

“…Multiple portions of the physiologic cycle can thus be reconstructed to yield a dynamic image sequence of the organ of interest. (10,(12)(13)(14)(15)(16)(17) In pulmonary applications, the earliest use of this method has been in oncology, tracking the maximum trajectory throughout a respiratory cycle for the purposes of treatment planning. (15,18).…”

“…With the ability to retrospectively reconstruct 4D image data sets to represent a complete breathing cycle it becomes possible to assess regional ventilation through the use of image matching algorithms (12)(13)(14)(15)(16)(17)(18)112). Such image matching provides not only regional volume changes but also regional images of tissue strain, providing potential insights into local tissue properties such as early fibrosis, etc.…”

Temporal Groupwise Registration for Motion Modeling

“…They register each volumetric phase image to a reference image by using the displacement field computed for the previous volumetric image as the initial deformation. Sarrut et al [20] simulate a 4D computed tomography (CT) image of the thorax by first registering end-diastole and end-systole images and then by linearly interpolating images in between. These methods either do not use temporal information or fix a reference frame during the registration.…”

How Do Registration Parameters Affect Quantitation of Lung Kinematics?

“…Dougherty and Li have applied optical flow to computed tomography (CT) images of the lung to construct an atlas of normal pulmonary anatomy [1,2], while Hatabu et al have developed magnetic resonance protocols for imaging the lung, [3]. In addition, Sarrut et al have proposed an interpolation scheme for upsampling 4DCT image sequences, [4].…”