Table 1.

Characteristics of included studies

Author	Publication date	Study goal	Study type	Number of patients	Reconstruction methods	Vendor	Quantitative outcome measures	Abdominal organs	CNR formula
M. Akagi [12]	Jan 2019		RS	46	AIDR3D FIRST AiCE	Canon Medical Systems	CT value Noise CNR	Liver	$\frac{{\mathit{ROI}}_{\mathrm{organ}}-{\mathit{ROI}}_{\mathrm{muscle}}}{\mathrm{noise}}$
M. Akagi [11]	Oct 2020		RS	50	AIDR3D FIRST AiCE	Canon Medical Systems	Noise CNR	Liver	$\frac{{\mathit{ROI}}_{\mathrm{organ}}-{\mathit{ROI}}_{\mathrm{muscle}}}{\mathrm{noise}}$
L. Cao [13]	Feb 2021	Using DLR to reduce dose and improve image quality	PS	40	ASIR-V 50% DLR-H	GE Healthcare	CT value Noise CNR	Liver Spleen	$\frac{{\mathit{ROI}}_{\mathrm{organ}}-{\mathit{ROI}}_{\mathrm{muscle}}}{\mathrm{noise}}$
Y. Ichikawa [14]	Jan 2021		RS	50	ASIR-V DLR-H	GE Healthcare	Noise SNR/CNR	Liver	$\frac{{\mathit{ROI}}_{\mathrm{organ}}-{\mathit{ROI}}_{\mathrm{liver}}}{\mathrm{noise}}$
C.T. Jensen [15]	July 2020	Quantitative and qualitative evaluation of DLR	RS	40	ASIR-V 30% DLR-L/M/H	GE Healthcare	CT value Noise CNR	Liver Spleen	$\frac{{\mathit{ROI}}_{\mathrm{organ}}-{\mathit{ROI}}_{\mathrm{muscle}}}{\mathrm{noise}}$
T. Kaga [16]	April 2021	Evaluating image quality and lesion detection of DLR	PS	59	ASIR-V 40% DLR/L/M/H	GE Healthcare	CT value Noise SNR/CNR	Liver Spleen Pancreas	$\frac{{\mathit{ROI}}_{\mathrm{organ}}-{\mathit{ROI}}_{\mathrm{liver}}}{\mathrm{noise}}$
J.H. Kim [17]	Jan 2021	Evaluating image quality and DLR	RS	58	ASIR-V 30% DLR-M/H	GE Healthcare	CT value Noise SNR/CNR	Liver	$\frac{{2\left({\mathit{ROI}}_{\mathrm{organ}},-,{\mathit{ROI}}_{\mathit{background}}\right)}^2}{{{\mathit{SD}}_{\mathrm{organ}}}^2+{{\mathit{SD}}_{\mathrm{background}}}^2}$
L.L. Li [18]	March 2021	Quantitative and qualitative evaluation of DLR	PS	47	FBP ASIR-V 40/80% DLR-M/H	GE Healthcare	CT value Noise SNR/CNR	Liver Spleen Kidney	$\frac{{\mathit{ROI}}_{\mathrm{organ}}-{\mathit{ROI}}_{\mathrm{muscle}}}{\mathrm{noise}}$
Y. Nakamura [19]	July 2019		RS	58	AIDR3D AiCE	Canon Medical Systems	Noise CNR	Liver	$\frac{{\mathit{ROI}}_{\mathrm{organ}}-{\mathit{ROI}}_{\mathrm{tumor}}}{\mathrm{noise}}$
Y. Nakamura [20]	Nov 2020		RS	72	AIDR3D FIRST AiCE	Canon Medical Systems	Noise CNR	Liver	$\frac{{\mathit{ROI}}_{\mathrm{organ}}-{\mathit{ROI}}_{\mathrm{muscle}}}{\mathrm{noise}}$
Y. Noda [21]	Feb 2021	Evaluating image quality and lesion detection of DLR	PS	59	ASIR-V 40% DLR-H	GE Healthcare	CT value SNR	Liver Spleen Pancreas	–
C. Park [22]	Oct 2020		RS	37	ASIR-V 80//100% DLR-L/M/H	GE Healthcare	CT value Noise SNR/CNR	Liver	$\frac{{\mathit{ROI}}_{\mathrm{organ}}-{\mathit{ROI}}_{\mathrm{fat}}}{\mathrm{noise}}$
R. Singh [23]	Sept 2019		PS	59	FBP AIDR3D FIRST AiCE	Canon Medical Systems	Noise SNR	Liver	–
A. Steuwe [24]	Jan 2021		RS	27	FBP SAFIRE DLR	Siemens Healthineers	CT value Noise SNR/CNR	Liver Spleen	$\frac{{\mathit{ROI}}_{\mathrm{organ}}-{\mathit{ROI}}_{\mathrm{fat}}}{\mathrm{noise}}$
X. Wang [25]	April 2021		PS	251	FBP 30% IR DLR 50%/100%	Neusoft Medical	Noise SNR/CNR	Liver	$\frac{{2\left({\mathit{ROI}}_{\mathrm{organ}},-,{\mathit{ROI}}_{\mathrm{background}}\right)}^2}{{{\mathit{SD}}_{\mathrm{organ}}}^2+{{\mathit{SD}}_{\mathrm{background}}}^2}$
L. Zeng [26]	Feb 2021		PS	207	HIR 50% DLR	United Imaging Healthcare	CT value Noise SNR/CNR	Liver	$\frac{{\mathit{ROI}}_{\mathrm{organ}}-{\mathit{ROI}}_{\mathrm{muscle}}}{\mathrm{noise}}$

PS prospective, RS retrospective, AIDR3D adaptive iterative dose reduction 3D, FIRST forward-projected model-based iterative reconstruction solution, AiCE advanced intelligent clear-IQ engine, DLR-L/-M/-H deep learning reconstruction low/medium/high, ASIR-V adaptive statistical iterative reconstruction, FBP filtered back-projection, SAFIRE sinogram affirmed iterative reconstruction, IR iterative reconstruction, SNR signal-to-noise ratio, CNR contrast-to-noise ratio