Task-based assessment of breast tomosynthesis: Effect of acquisition parameters and quantum noisea)

Abstract

Purpose: Tomosynthesis is a promising modality for breast imaging. The appearance of the tomosynthesis reconstructed image is greatly affected by the choice of acquisition and reconstruction parameters. The purpose of this study was to investigate the limitations of tomosynthesis breast imaging due to scan parameters and quantum noise. Tomosynthesis image quality was assessed based on performance of a mathematical observer model in a signal-known exactly ͑SKE͒ detection task. Methods: SKE detectability ͑dЈ͒ was estimated using a prewhitening observer model. Structured breast background was simulated using filtered noise. Detectability was estimated for designer nodules ranging from 0.05 to 0.8 cm in diameter. Tomosynthesis slices were reconstructed using iterative maximum-likelihood expectation-maximization. The tomosynthesis scan angle was varied between 15°and 60°, the number of views between 11 and 41 and the total number of x-ray quanta was ϱ, 6ϫ 10 5 , and 6 ϫ 10 4 . Detectability in tomosynthesis was compared to that in a single projection. Results: For constant angular sampling distance, increasing the angular scan range increased detectability for all signal sizes. Large-scale signals were little affected by quantum noise or angular sampling. For small-scale signals, quantum noise and insufficient angular sampling degraded detectability. At high quantum noise levels, angular step size of 3°or below was sufficient to avoid image degradation. At lower quantum noise levels, increased angular sampling always resulted in increased detectability. The ratio of detectability in the tomosynthesis slice to that in a single projection exhibited a peak that shifted to larger signal sizes when the angular range increased. For a given angular range, the peak shifted toward smaller signals when the number of views was increased. The ratio was greater than unity for all conditions evaluated. Conclusion: The effect of acquisition parameters on lesion detectability depends on signal size. Tomosynthesis scan angle had an effect on detectability for all signals sizes, while quantum noise and angular sampling only affected the detectability small-scale signals.

Achieving Routine Submillisievert CT Scanning: Report from the Summit on Management of Radiation Dose in CT

“…3 decades (78,79). These model observers have been applied to many different imaging modalities to narrow the range of acceptable imaging conditions and to improve the efficiency of system optimization (80), including nuclear medicine imaging (81)(82)(83), mammography (84-87), dual-energy radiography (88), tomosynthesis and flat-panel cone-beam CT (89)(90)(91), and magnetic resonance imaging (92). However, relatively few studies have been performed with clinical CT (93,94).…”

Task‐based detectability in CT image reconstruction by filtered backprojection and penalized likelihood estimation

“…where S proj denotes the 2D projection NPS, Conversion gain from x-rays to secondary quanta (e.g., optical photons) P k Gain and spreading factors associated with K-fluorescence T 3 Transfer function due to stochastic spread of secondary quantā g 4 Coupling efficiency of photodiode a pd Width of (square) photodiode T 5 Transfer function due to photodiode aperture III 6 Detector pixel sampling (2D comb function) σ add Additive electronics noise III 8 Postreadout projection resampling (optional) T 8 Transfer function due to 2D binning aperture (optional) T 10 Ramp filter T 11 Apodization filter T 12 Interpolation filter T 13 Transfer function associated with backprojection of signal 13 Transfer function associated with backprojection of noise III 14 3D voxel sampling (3D comb function) III 15 Postreconstruction sampling (optional) T 15 Transfer function due to 3D binning aperture (optional) m Number of projections acquired across a circular orbit θ tot Total angular extent of acquisition M Magnification factor, source-detector distance (SDD)/source-axis distance (SAD) FOV Size of the reconstruction field of view…”

A virtual trial framework for quantifying the detectability of masses in breast tomosynthesis projection data

“…Specifically, optimization of the x-ray source scan angle and angular sampling scheme is an area of interest in recent literature. [6][7][8][9][10][11][12][13][14][15][16][17] These studies could reduce the number of physical prototype iterations and eventually lead to task-and patient-specific optimization of tomosynthesis. But to achieve these goals, we first need accurate, task-based strategies for evaluating key DBT system parameters in simulation.…”