Theoretical framework for the dual-energy cone-beam CT noise-power spectrum, NEQ, and tasked-based detectability index

G. J. Gang; W. Zbijewski; J. W. Stayman; J. A. Carrino; J. H. Siewerdsen

doi:10.1117/12.911817

23 February 2012 Theoretical framework for the dual-energy cone-beam CT noise-power spectrum, NEQ, and tasked-based detectability index

G. J. Gang, W. Zbijewski, J. W. Stayman, J. A. Carrino, J. H. Siewerdsen

Author Affiliations +

Proceedings Volume 8313, Medical Imaging 2012: Physics of Medical Imaging; 83131J (2012) https://doi.org/10.1117/12.911817
Event: SPIE Medical Imaging, 2012, San Diego, California, United States

Abstract

The optimization of dual-energy computed tomography (DE-CT) is challenged by the lack of a theoretical foundation for image quality. This work reports a cascaded systems analysis model that was used to derive signal and noise propagation in DE-CBCT in prevalent Fourier metrics such as the noise-power spectrum (NPS) and noise-equivalent quanta (NEQ). The model was validated in comparison to measurements of the 3D NPS and NEQ in DE-CBCT images acquired using an experimental imaging bench. Task-based detectability index was derived using DE-NPS and NEQ as an objective function in optimizing DE imaging parameters such as the dose allocation factor (D_A) and kVp pair. The resulting dose allocation optimization is in agreement with the practice of assigning more dose to the high-energy image (D_A < 0.5), and the model provides a quantitative basis for examining the optimal dose allocation as a function of total dose, kVp pair, the presence of electronics noise, and the imaging task. An example optimization is shown for a breast tumor detection task. Using DE decomposition to cancel fibroglandular tissue (rendering a DE-CBCT image of breast tumor against an adipose tissue background) and assuming a total dose of 15mGy, the optimal kVp pair is identified at [45, 105]kVp with DA=0.46. The model is sufficiently general for applications beyond this example, demonstrating utility in the optimization in a broad range of imaging parameters. The model provides a new, valuable framework for understanding the theoretical limits of DE-CBCT imaging performance and maximizing image quality while minimizing radiation dose.

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G. J. Gang, W. Zbijewski, J. W. Stayman, J. A. Carrino, and J. H. Siewerdsen "Theoretical framework for the dual-energy cone-beam CT noise-power spectrum, NEQ, and tasked-based detectability index", Proc. SPIE 8313, Medical Imaging 2012: Physics of Medical Imaging, 83131J (23 February 2012); https://doi.org/10.1117/12.911817

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KEYWORDS

Systems modeling

Tissues

3D modeling

Modulation transfer functions

Image quality

Optimization (mathematics)

Imaging systems

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