Preserving image texture while reducing radiation dose with a deep learning image reconstruction algorithm in chest CT: A phantom study

Purpose: To assess whether a deep learning image reconstruction algorithm (TrueFidelity) can preserve the image texture of conventional filtered back projection (FBP) at reduced dose levels attained by ASIR-V in chest CT. Methods: Phantom images were acquired using a clinical chest protocol (7.6 mGy) and two levels of dose reduction (60% and 80%). Images were reconstructed with FBP, ASIR-V (50% and 100% blending) and True-Fidelity (low (DL-L), medium (DL-M) and high (DL-H) strength). Noise (SD), noise power spectrum (NPS) and task-based transfer function (TTF) were calculated. Noise texture was quantitatively compared by computing root-mean-square deviations (RMSD) of NPS with respect to FBP. Four experienced readers performed a contrast-detail evaluation. The dose reducing potential of TrueFidelity compared to ASIR-V was assessed by fitting SD and contrast-detail as a function of dose. Results: DL-M and DL-H reduced noise and NPS area compared to FBP and 50% ASIR-V, at all dose levels. At 7.6 mGy, NPS of ASIR-V 50/100% was shifted towards lower frequencies (f(peak) = 0.22/0.13 mm(-1), RMSD = 0.14/0.38), with respect to FBP (f(peak) = 0.30 mm(-1)). Marginal difference was observed for TrueFidelity: f(peak) = 0.33/0.30/0.30 mm(-1) and RMSD = 0.03/0.04/0.07 for L/M/H strength. Values of ITF50% were independent of DL strength and higher compared to FBP and ASIR-V, at all dose and contrast levels. Contrast-detail was highest for DL-H at all doses. Compared to 50% ASIR-V, DL-H had an estimated dose reducing potential of 50% on average, without impairing noise, texture and detectability. Conclusions: TrueFidelity preserves the image texture of FBP, while outperforming ASIR-V in terms of noise, spatial resolution and detectability at lower doses.

Automated summary

The study assessed the performance of TrueFidelity algorithm at low doses in chest CT, showing that TrueFidelity can better preserve image texture at lower doses compared to ASIR-V.