Distortion correction for digital subtraction angiography imaging: PC based system for radiosurgery planning

We report, the development of a personal computer (PC) based system to correct distortion of digital subtraction angiography (DSA) images. The program was written in INTERACTIVE DATA LANGUAGE (IDL) and implemented on a PC equipped with an Intel Pentium III 450 MHz CPU in the MICROSOFT WINDOWS 98 environment. The system consists of two modules. The coefficient calculation module detects distortions of grid phantom images automatically and determines the distortion correction function. An additional distortion correction module corrects detected distortion using the correction function determined by the coefficient calculation module. The correction program can be used for images taken at arbitrary lateral oblique angle, and about 4 min are required to correct an image. The correction program was verified using phantom and clinical images. After image correction, the root mean square (rms) deviations of the reference points of each image were calculated. The average value of the rms deviation of all phantom images was about 0.1 mm. The residual mean rms deviation of the corrected clinical images (0.34+/-0.19 mm) and maximum error (0.59+/-0.26 mm) were within the acceptable limits of stereotactic radiosurgery. The accuracy, the ability to process lateral oblique angles, and reasonable program running time makes the developed system a valuable tool in clinical practice, for example for the planning of gamma knife radiosurgery.