Comparison of geometric distortion in digital angiography with and withouta correction program - Technical note

This study was conducted to evaluate the geometric distortion of angiograph ic images created from a commonly used digital x-ray imaging system and the performance of a commercially available distortion-correction computer pro gram. A 12 X 12 X 12-cm wood phantom was constructed. Lead shots, 2 mm in diamete r, were attached to the surfaces of the phantom. The phantom was then place d inside the angiographic localizer. Cut films (frontal and lateral analog films) of the phantom were obtained. The films were analyzed using GarnmaPl an target series 4.12. The same procedure was repeated with a digital x-ray imaging system equipped with a computer program to correct the geometric d istortion. The distortion of the two sets of digital images was evaluated u sing the coordinates of the lead shots from the cut films as references. The coordinates of all lead shots obtained from digital images and correcte d by the computer program coincided within 0.5 mm of those obtained from cu t films. The average difference is 0.28 mm with a standard deviation of 0.0 1 mm. On the other hand, the coordinates obtained from digital images with and without correction can differ by as much as 3.4 mm. The average differe nce is 1.53 mm, with a standard deviation of 0.67 mm. The investigated computer program can reduce the geometric distortion of di gital images from a commonly used xray imaging system to less than 0.5 mm. Therefore, they are suitable for the localization of arteriovenous malforma tions and other vascular targets in gamma knife radiosurgery.