Experimental study of rotational DSA on image deformation and measurement error / 中国医学影像技术

ABSTRACT

Objective To evaluate the image deformation and measurement error of rotational DSA by model experiment. Methods Five steel balls (diameter 20 mm) were placed in a horizontal space of 30 mm, the middle of which was as the isocenter for rotational DSA acquisition. Another 5 steel balls (diameter 10 mm) were placed in a vertical space of 30 mm with the same alignment for rotational DSA acquisition. The screen was divided into five regions and the morphological changes of the ball image were observed at each rotation angle. The experimental images of the left anterior oblique ball images at 20°, 40°and 60° among each two groups were selected and measured by automatic isocenter calibration and sphere calibration respectively, and compared with the actual diameters of balls to calculate the image magnification. Results Except the center one, other balls were of deformation at different rotation angles due to the distance to the detector leading to enlargement and reduction. With automatic isocenter calibration, only the diameter of the center ball corresponded with the actual one, the distance away from the center or the rotation angle was inversely proportional to measurement error (maximum magnification 12.42%).With sphere calibration, the measurement results in various regions at different rotation angle were basically the same, with smaller measurement error (maximum magnification 3.41%). Conclusion Placing the organ of interest in the center area can reduce image distortion in rotational DSA imaging. Selecting reasonable measuring technology according to the lesion location is helpful to control measurement errors.