<title>Pincushion correction techniques and their effects on calculated 3D positions and imaging geometries</title>

Abstract

Two techniques for pincushion correction are evaluated based on their effect on calculation of the image geometry and 3D positions of object points. Images of a uniform wire mesh and a calibration phantom containing lead beads in its surface were acquired on the image intensifier TV systems in our catheterization labs. The radial mapping functions relating points in the original images and in the corrected images were determined using the mesh image. The undistorted mesh model was also used to determine and correct the distortions locally, i.e., for each square region between the mesh points. Thus, two corrected images were obtained. Images of the calibration phantom before and after correction were analyzed to determine the 3D position of the lead beads and the imaging geometry, using a calibration algorithm and the enhanced Metz-Fencil technique. In comparing the 3D positions calculated from the radially corrected and locally corrected images, the calculated 3D positions using the calibration technique vary by less than 0.6 mm in the x and y direction and less than 5.0 mm in the z direction. The uncorrected data yields differences of over 1 cm in the z direction. The 3D positions calculated using the enhanced Metz-Fendil technique appear to be more accurate when pincushion correction is applied.

Geometrically correct 3-D reconstruction of intravascular ultrasound images by fusion with biplane angiography-methods and validation

“…In addition, the elimination of distorting axial rotations and shifts is required for 3-D reconstruction purposes [44], [45]. For more sophisticated diagnostics, e.g.…”

Determination of 3D positions of pacemaker leads from biplane angiographic sequences

“…The images of the wire mesh were used to determine the pixel size as well as the pincushion distortion and its correction. 15 Wire mesh images were not acquired at each orientation of the II, i.e., data to correct for the S-distortion, 16,17 which depends on the orientation of the II relative to the earth's magnetic field, were not obtained. The possible effects of the rotations due to S-distortions were investigated by rotating the image data about the approximate centers by angles of up to 5 degrees ͑Onnash and Prause 16 have reported ''twisting of the image of approximately 2.5 degrees'' for their system͒.…”

“…Local and radial corrections resulted in the same level and type of error in the 3D data. 15 Thus the radial correction technique was applied. The dependence of the 3D positions on a pincushion distortion is expected to be small and has been found to propagate primarily into changes in the calculated 3D center of mass of the object.…”