Extending the Detectability Index to Quantitative Imaging Performance: Applications in Tomosynthesis and CT

This study aimed to extend Fourier-based imaging metrics for the modeling of quantitative imaging performance. Breast tomosynthesis was used as a platform for investigating acquisition and processing parameters (e. g., acquisition angle and dose) that can significantly affect 3D signal and noise, and consequently quantitative imaging performance. The detectability index was computed using the modulation transfer function and noise-power spectrum combined with a Fourier description of imaging task. Three imaging tasks were considered: detection, area estimation (in coronal slice), and volume estimation of a 4 mm diameter spherical target. Task functions for size estimation were generated by using measured performance of the maximum-likelihood estimator as training data. The detectability index computed with the size estimation tasks correlated well with precision measurements for area and volume estimation over a fairly broad range of imaging conditions and provided a meaningful figure of merit for quantitative imaging performance. Furthermore, results highlighted that optimal breast tomosynthesis acquisition parameters depend significantly on imaging task. Mass detection was optimal at an acquisition angle of 85 degrees while area and volume estimation for the same mass were optimal at similar to 100 degrees and 125 degrees acquisition angles, respectively. These findings provide key initial validation that the Fourier-based detectability index extended to estimation tasks can represent a meaningful metric and predictor of quantitative imaging performance.