H.C. van Assen, H.A. Vrooman, M. Egmont-Petersen, G. Koning, E.L. van
der Linden, B. Goedhart, J.H.C. Reiber. "Automated calibration in vascular
X-ray images using the accurate localization of catheter marker bands,"
Investigative
Radiology, Vol. 35, No. 4, pp. 219-226, 2000.
Abstract:
RATIONALE AND OBJECTIVES. TO develop a new automated calibration method
for vessel measurements in vascular x-ray images.
METHODS. Radiopaque marker bands mounted equidistantly on a small catheter
were acquired in vitro at five image intensifier (II) sizes in x-ray projection
images, The positions of the marker centers were detected by using a Hough
transform and were computed at subpixel precision by using either a novel,
iterative center-of-gravity approach (CGA) or a symmetry filter, Curve-fitting
procedures were used to reject false-positive marker detections and to
calculate intermarker distances. The calibration factor was calculated
from the true marker distance and the average of the measured distances
in pixels, Results were compared statistically with a grid calibration
method, which was taken as the gold standard. A simulation study was performed
to assess the influence of image noise on the CGA method,
RESULTS, The iterative CGA method was convergent and faster than the
symmetry-based technique. For four II sizes (17, 20, 25, and 31 cm), the
results from the CGA method were not significantly different from the results
obtained with grid calibration. For the II size of 38 cm, a significant
difference (0.3% of the grid calibration factor) was found; however, this
was caused by the quantification error in the image data and was not clinically
relevant, In general, the performance of the CGA method improved with increasing
signal-to-noise ratio.
CONCLUSIONS. A practical new calibration method for small catheter
sizes was developed and validated for quantitative vascular arteriography.
Reprints, please contact me: michael@cs.uu.nl