An objective computer system for the quantification of artery stenoses

Wankling, P.F.; Perry, Raphael A.; Seth, Ashok; Hunt, A; Escaned, X.; Newell, J. A.; Shiu, M F

doi:10.1007/bf01833977

Cited by 6 publications

(4 citation statements)

References 6 publications

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“…Model 1 uses bilinear interpolation between the distortion vectors derived at the four grid points that constitute a quadrilateral cell, where a distortion vector is defined as the vector from the position of a distorted grid point to its corresponding undistorted position. 21,22 In Models 2 and 3 polynomial mapping is applied:…”

Section: Distortion Correctionmentioning

confidence: 99%

Correction for geometric image distortion in the x‐ray imaging chain: Local technique versus global technique

Gronenschild

1999

Medical Physics

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The local technique to correct for geometric image distortion in the x-ray imaging chain has been implemented and compared with the global correction technique reported previously. Three local correction models were considered, all applied locally within each quadrilateral cell bounded by four adjacent points on a distorted 1.0 cm spaced rectilinear calibration grid. Model 1 uses bilinear interpolation between the correction vectors derived at the four vertices. In Models 2 and 3 a polynomial mapping from distorted to undistorted positions is applied, with Model 2 representing a linear six-parameter correction and Model 3 a nonlinear eight-parameter correction. Both techniques have been analyzed in depth concerning their accuracy. To this end, experimental (35 mm cine film and online video) and computer simulated distorted images of the calibration grid were used. Both radial and sigmoidal distortions were considered in the simulations. The main results are summarized as follows. The accuracy of the local technique depends upon the position within each quadrilateral cell and upon the local direction of the distortion gradient, contrary to the global technique. The accuracy of the local technique decreases with increasing radial as well as sigmoidal distortion. For the global technique only the latter dependency applies. The relationship of the accuracy with the pixel size is different for all models. Finally, the local technique is more sensitive to noise than the global technique. The reproducibility of the correction methods has been evaluated by means of imaging the calibration grid in various orientations with respect to the input screen of the image intensifier. The local technique turns out to reproduce a factor of 4-10 worse than the global technique. In summary, Model 1 is the worst method in all respects, whereas Model 3 is slightly better than Model 2. However, the global technique is to be preferred because it outperforms the local technique on all relevant issues.

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Section: Distortion Correctionmentioning

confidence: 99%

Correction for geometric image distortion in the x‐ray imaging chain: Local technique versus global technique

Gronenschild

1999

Medical Physics

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“…This can be performed locally for each quadrilateral cell with vertices defined by the corresponding grid points. The mapping is exactly known at the vertices and for positions inside the cell, either an analytical function 16 or bilinear interpolation 11,12 can be used. However, this will give rise to discontinuities at the transition from one cell to another.…”

Section: Correctionmentioning

confidence: 99%

“…Interpolation is used to obtain the correction at each intermediate position. 11,12 Some investigators store the computed distortion vectors at each intersection point of the calibration grid and use these to automatically correct positions lying on the object boundaries ͑e.g., arterial edges͒. 5,13,14 In another approach, analytical functions are used to map distorted positions to undistorted positions.…”

Section: Introductionmentioning

confidence: 99%

The accuracy and reproducibility of a global method to correct for geometric image distortion in the x‐ray imaging chain

Gronenschild

1997

Medical Physics

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A method to correct for geometric image distortion in the x-ray imaging chain, so-called dewarping, has been developed. A global two-dimensional polynomial model of which the degree is optimized is used. The performance of the method has been tested in a number of experiments using images of a plate with a 1 cm spaced wire grid put against the input screen of the x-ray image intensifier (14/17/27 cm). Both offline cine film and online video images were analyzed. The accuracy of the dewarp method was derived from the acquired images and from computer-simulated distorted images. The robustness and reproducibility of the dewarp method was evaluated by means of imaging the grid in various random orientations. Three parameters describing the behavior of the algorithm were considered. One is the reproducibility of the location of a dewarped position. The second parameter is the reproducibility of the distance between two adjacent dewarped positions as a measure of the reproducibility of the size of an object under investigation. The third parameter is the reproducibility of the pixel size in the plane of the calibration plate. The major results are: the reproducibility of the location of a dewarped position was 0.01-0.04 mm for cine film and 0.04-0.07 mm for video images. The coefficient of variation of the distance between two dewarped positions was 0.04%-0.11% for cine film and 0.15%-0.18% for video images. The dewarp algorithm turned out to be fast and accurate and the distortion was removed over the whole image field down to a low random residual level. It was found that a random orientation of the grid did not affect the assessment of the distortion nor its correction. The dewarp method proved to be intrinsically robust and highly reliable. Time instability of the imaging chain was the main source of variability in the dewarp results.

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“…Studies of videodensitometry using conventional two-dimensional techniques have been found to be generally less accurate than edge detection (20). However, there is also evidence that densitometric measurements of vessel dimensions, when properly made and corrected for vessel orientation and local background intensity, may be more accurate than geometric measurements (21). By utilizing the ability of a threedimensional reconstruction system to correct the videodensitometric measurements for the inclination angle of the target vessel, the clinical utility of such measurements may be significantly enhanced.…”

Section: Introductionmentioning

confidence: 98%

A Comparison of the Accuracy and Reproducibility of Digital Three-Dimensional Coronary Artery Reconstructions Using Edge Detection or Videodensitometry

Muhlestein

Zhang

Parker

et al. 1997

Computers and Biomedical Research

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An objective computer system for the quantification of artery stenoses

Cited by 6 publications

References 6 publications

Correction for geometric image distortion in the x‐ray imaging chain: Local technique versus global technique

Correction for geometric image distortion in the x‐ray imaging chain: Local technique versus global technique

The accuracy and reproducibility of a global method to correct for geometric image distortion in the x‐ray imaging chain

A Comparison of the Accuracy and Reproducibility of Digital Three-Dimensional Coronary Artery Reconstructions Using Edge Detection or Videodensitometry

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