Measuring regional hypertrophy by radiopaque myocardial markers viewed in 3D with a single X-ray camera

Regional differences in hypertrophy may be measured by comparing the positions of radiopaque myocardial markers at multiple time points. Accurate measurement of volume changes requires 3-D reconstruction of marker positions from stereo pairs of images. Using the periodicity of heart motion quasi stereo pairs can be obtained by using one camera at two viewing positions. For this set-up 3-D reconstruction methods were developed. In computer simulations of markers attached to a beating heart (70 mm diameter) the performance of these methods was evaluated. With 12 markers recorded on standard video (256/spl times/256 pixel), a position noise of 0.5 pixel (s.d), and using only a single frame pair, the reconstruction error was 1.7 mm. Using the marker images in a sequence of 50 frames per view, the error reduced to 0.35 mm. By applying a SVD based noise reduction method the error may further be reduced to 0.17 mm. The obtained accuracy is appropriate for the measurement of volume changes of cardiac muscle which are typical of the order of 10%.